JPH0588153A - Liquid crystal panel and liquid crystal display device formed by using this panel - Google Patents

Abstract

(57) [Summary] [Structure] The pixel electrode 13 is formed of ITO, and the counter electrode 1
5 is formed of a metal material on the reflective electrode. On the reflective electrode 15 is formed a diffraction grating 41 with a material having a refractive index that substantially matches the ordinary refractive index n _o of the liquid crystal 21. The liquid crystal 21 is a polymer dispersed liquid crystal. Light incident on the liquid crystal panel is made incident from the array substrate 12 side. Since the liquid crystal 21 is the refractive index of the diffraction grating and n _o when the transmission state is matched grating disappears. Therefore, the incident light is reflected as it is by the reflective electrode 15 and emitted from the pixel electrode 13. When the liquid crystal 21 is in the scattering state, the incident light is scattered and diffracted by the liquid crystal layer. [Effect] Since the reflecting electrode 15 has high smoothness, the reflecting efficiency is high. Further, when the liquid crystal 21 is scattered, the incident light is scattered and diffracted. Therefore, the contrast can be made very high. Further, since a polarizing plate is unnecessary, high brightness image display can be realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a liquid crystal display device (hereinafter referred to as a liquid crystal projection television) for enlarging and projecting an image displayed on a small liquid crystal panel on a screen, and a liquid crystal used for the liquid crystal projection television. It's about panels.

[0002]

2. Description of the Related Art Since a liquid crystal panel has many features such as a light weight and a thin shape, research and development have been actively conducted. However, there are many problems such as difficulty in increasing the screen size. Therefore, in recent years, a liquid crystal projection television, which enlarges and projects a display image of a small liquid crystal panel by a projection lens or the like to obtain a large-screen display image, has been suddenly attracting attention. At present, liquid crystal projection televisions that have been commercialized use twisted nematic (hereinafter referred to as TN) liquid crystal panels that utilize the optical rotation characteristics of liquid crystals. As an example, "Flat Panel Display '91 Nikkei BP Publishing P194-P205"
There is.

FIG. 10 is an equivalent circuit diagram of a liquid crystal panel. G _{1 to} G _m are gate signal lines, one end of which is connected to the gate drive IC 91. S _{1 to} S _n are source signal lines, one end of which is connected to the source drive IC 92. Each pixel has a thin film transistor (hereinafter referred to as a TFT) 93 for applying a signal to a pixel electrode, and an additional capacitor 94 for holding a signal is formed. Reference numeral 95 denotes a liquid crystal sandwiched between the pixel electrode and the counter electrode, which can be regarded as a capacitor in terms of an electric circuit.

A conventional liquid crystal panel will be described below. FIG. 11 is a sectional view of a conventional liquid crystal panel. However, parts unnecessary for description are omitted, and they are drawn as a model for easy understanding of the drawings. The above also applies to the subsequent drawings. 1 in (Fig. 14)
Reference numeral 01 denotes a counter electrode substrate, and a counter electrode 106 made of ITO having light transmittance is formed on one surface of the counter electrode substrate. A black matrix made of Cr or the like is formed on the counter electrode 106. On the other hand, the array substrate 102
A TFT 108 for applying a signal to a pixel, a source signal line 110, and the like are formed on one surface of the above, and an insulating film 103 is formed on the TFT. SiNx or the like corresponds to the material for forming the insulating film. Insulation film 1
On 03, the reflective electrode 104 is formed with a metal substance such as Al or Cr. Alignment films 112 and 111 are formed on the reflective electrode 104 and the counter electrode 106,
Alignment treatment is performed by the rubbing process. A nematic liquid crystal having a positive dielectric constant is sandwiched between the counter electrode substrate 101 and the array substrate 102.

The operation of the liquid crystal panel is shown in FIG. The light modulation uses the property of birefringence of nematic liquid crystal. The rubbing angle of the alignment films 111 and 112 is 60 degrees. Linearly polarized light is incident on the liquid crystal panel from the counter electrode substrate 101 side. This polarization component is called the P component for ease of explanation. A polarization component different from the P component by 90 degrees is called an S component. As shown in FIG. 13A, when the switch 122 is off, no voltage is applied between the counter electrode 106 and the reflective electrode 104. In this case, the incident light is reflected by the reflective electrode 104, and is emitted from the counter electrode substrate as the P component as it is. As shown in FIG. 12B, when the switch 122 is in the ON state, a voltage is applied between the counter electrode 106 and the reflective electrode 104, and the incident P component light is the S component light depending on the applied voltage. And is emitted from the counter electrode substrate 101.

A conventional liquid crystal projection television will be described below with reference to the drawings. FIG. 12 is a principle diagram of a conventional liquid crystal projection television. First, a light source such as a metal halide lamp is arranged in the condensing optical system 113. The white light emitted from the metal halide lamp is extracted by visible light components such as ultraviolet rays and infrared mirrors (hereinafter referred to as UVIR cut mirrors). The visible light emitted from the condensing optical system 113 is sequentially converted into red light (hereinafter referred to as R light), green light (hereinafter referred to as G light), and blue light (hereinafter referred to as B light) by a dichroic mirror. To separate. The polarization beam splitter reflects the P component,
It is assumed that the S component light is transmitted. Of the light guided to the polarization beam splitter, the P component light is reflected and enters from the counter electrode 106 side of the conventional reflective liquid crystal panel 115. The liquid crystal panel 115 modulates the incident light and converts the P component light into the S component light according to the video signal according to the operation principle described in (FIG. 13). The converted S component light passes through the polarization beam splitter 116 and is projected onto the screen 119 by the lens 117.

FIG. 14 is a block diagram of a conventional liquid crystal projection type television. In FIG. 14, 133a is a dichroic mirror that reflects R light (hereinafter referred to as RDM), 133b is a dichroic mirror that reflects G light (hereinafter referred to as GDM), and 133c is a dichroic mirror that reflects B light. (Hereinafter referred to as BDM). The BDM may be replaced with a mirror. 132
a is an R light modulating liquid crystal panel, 132b is a G light modulating liquid crystal panel, and 132c is a B light modulating liquid crystal panel.
Reference numerals 4a, 134b and 134c are projection lenses. In addition,
Since the operation of the conventional liquid crystal projection television has been described with reference to FIG. 12, it will be omitted.

[0008]

The conventional liquid crystal panel is T
The reflective electrode 104 is formed on the insulating film 103 on the FT 108. The reflective electrode 104 is required to have a mirror surface property, but since the TFT 108 and the like are formed in the lower layer of the reflective electrode 104, the formation pattern of the TFT 108 is transferred and unevenness occurs. In order to prevent the unevenness, the insulating film 103 may be thickened. However, if the insulating film 103 is thickened, T
It becomes difficult to form a contact hole for electrically connecting the FT 108 and the reflective electrode 104. In addition, the concave depression in the contact hole portion also becomes large. Therefore, the specularity of the reflective electrode 104 is degraded.
On the other hand, there is a method of increasing the thickness of the reflective electrode 104,
If the film thickness is increased, problems occur such that the deposition time of the metal film for the reflective electrode becomes long, and it becomes difficult to separate the reflective electrode from the adjacent reflective electrode by patterning. Also,
At the time of rubbing, the end of the reflective electrode 104 may be caught, and the peripheral alignment of the reflective electrode 104 may have a poor orientation. In addition, there is a problem that only the end of the reflective electrode 104 is scraped off and the scraped pieces short-circuit the adjacent reflective electrodes.

For the above reasons, the conventional reflection type liquid crystal panel has the advantage that the aperture ratio of the pixel can be increased.
Actually, the reflectance at the reflective electrode was lowered, and it was difficult to obtain a high brightness screen. Also, many pixel defects occur.
In fact, the screen size is 2.3 inches and the number of pixels is 960 x 144.
2, a liquid crystal panel having an aperture ratio of 60% was prototyped, and a liquid crystal projection type television was prototyped using the three panels. The results are that when the screen size is 40 inches and the screen gain is 5, the maximum brightness is 20 (ft-L), The contrast was about 20.

Further, in the conventional liquid crystal panel and liquid crystal projection television, only one of the P component light and the S component light is used. Therefore, since more than half of the light generated by the light source is not used, the light utilization ratio is poor and only a low brightness screen can be obtained.

[0011]

In order to solve the above problems, in the liquid crystal panel of the first aspect of the present invention, a pixel electrode is formed of a transparent material such as ITO and a counter electrode is formed of a metal material to form a reflective electrode. .. An alignment film is formed on the pixel electrode and the reflective electrode, and a rubbing process is performed. A nematic liquid crystal is sandwiched between the counter electrode and the reflective electrode.

In the liquid crystal panel of the second invention, I
A pixel electrode is formed of a transparent material such as TO and a counter electrode is formed of a metal material. Polymer dispersed liquid crystal is sandwiched between the counter electrode and the reflective electrode.

In the liquid crystal panel of the third aspect of the present invention, the pixel electrode is formed of a transparent material such as ITO, and the reflection type diffraction grating is formed on the surface of the counter electrode substrate which is in contact with the liquid crystal layer. In addition,
The diffraction grating described in the present invention also includes a phase grating.
An alignment film is formed on the diffraction grating and the pixel electrode, and a rubbing process is performed. A nematic liquid crystal is sandwiched between the counter electrode and the diffraction grating.

In the liquid crystal panel of the fourth aspect of the present invention, IT
A pixel electrode is formed of a transparent material such as O, and a reflection type diffraction grating is formed on the counter electrode substrate side. A polymer dispersed liquid crystal is sandwiched between the diffraction grating and the pixel electrode.

The liquid crystal projection television of the first aspect of the present invention is a liquid crystal panel of the first or third aspect of the present invention, a light emitting source such as a metal halide lamp, and a function of taking out the P component or the S component of the light from the light emitting source. And a beam splitter having a function of separating the light modulated by the liquid crystal panel into a P component and an S component, and a projection lens system for projecting the light modulated by the liquid crystal panel.

The liquid crystal projection television according to the second aspect of the present invention is the second aspect.
Alternatively, it has a liquid crystal panel of the fourth invention, a light emitting source such as a metal halide lamp, a lens system for irradiating the liquid crystal panel with light from the light emitting source, and a projection lens system for projecting light modulated by the liquid crystal panel. It is a thing.

The liquid crystal projection television according to the third aspect of the present invention includes the liquid crystal panel according to the third aspect of the present invention, a light emitting source such as a xenon lamp, and light of P component or S component of the light from the light emitting source. And the light modulated by the liquid crystal panel
It has a beam splitter having a function of separating the light into a component and an S component, and a Schlieren optical system for projecting light modulated by the liquid crystal panel.

The liquid crystal projection type television of the fourth aspect of the invention has the liquid crystal panel of the fourth aspect of the invention, a light emitting source such as a xenon lamp, and a Schlieren optical system for projecting light modulated by the liquid crystal panel. It is a thing.

[0019]

In the liquid crystal panel of the present invention, the pixel electrode is made of ITO and the reflective electrode is formed on the counter electrode substrate. Light to the liquid crystal panel enters from the array substrate side. TFT on the counter electrode
Since elements such as the above are not formed and have good smoothness, the light reflection efficiency can be made very high.
Further, by forming the reflective electrode with a metal material, it is easy to realize the resistance reduction of the counter electrode.

By using polymer dispersed liquid crystal as the liquid crystal, it is not necessary to use a polarizing element such as a beam splitter. Therefore, the light utilization efficiency can be doubled or more. In addition, the light incident on the liquid crystal panel passes through the liquid crystal layer 2
As a result, it is possible to realize good scattering characteristics with a thinner liquid crystal film thickness and to reduce the driving voltage.

By using a reflection type diffraction grating as the reflection electrode, incident light can be bent at a predetermined angle and its energy intensity can be changed. Therefore, by combining with a projection lens to realize a projection television, high-contrast image display can be performed. In particular, by using a polymer-dispersed liquid crystal as the liquid crystal, a rubbing process is unnecessary and a high-luminance screen can be realized.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A liquid crystal panel of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of the liquid crystal panel of the first invention. In FIG. 1, reference numeral 11 is a counter electrode substrate, on one surface of which a reflective electrode 15 is formed. Examples of the constituent material of the reflective electrode include Al and Cr, and Al is preferable from the viewpoint of reflectance. The manufacturing film thickness is preferably 500 Å or more, and more preferably 1000 Å or more. On the other hand, on the array substrate, there are formed a pixel electrode 13 formed of a material having optical transparency such as ITO, and a TFT 14 as a switching element for applying a signal to the pixel electrode 13. The switching element is not limited to the TFT, but MI
It may be M or a ring diode. Reflective electrode 1
Alignment films 17 and 18 are formed on the pixel electrode 5 and the pixel electrode and subjected to rubbing treatment. The rubbing angle between the alignment films is preferably 30 to 70 degrees, and according to experiments, the degree of light modulation was good near 45 degrees and around 60 degrees. In this example, the alignment treatment was performed at 45 degrees. As the liquid crystal, nematic liquid crystal is used, and the thickness of the liquid crystal layer 16 is 2 μm to 8 μm, and among them, 3 μm to 4 μm is preferable. Note that, hereinafter, components having the same number have the same or similar configuration or contents.

The operation of the liquid crystal panel is the same as that shown in FIG. 13 except that light is incident on the liquid crystal panel from the array substrate 12 side. Although the aperture ratio is limited by the area of the pixel electrode 13, an aperture ratio of about 50% can be realized even if the pixel size is 40 μm or less. The gate signal line (not shown) and the source signal line (not shown) also serve as a black matrix. Although not shown, TF
A light-shielding film is formed on the surface of the T semiconductor layer close to the TFT array substrate 12 so that light does not enter the semiconductor layer, thereby preventing photocon. Linearly polarized light is incident on the array substrate 12.
When no voltage is applied to the liquid crystal layer 16, the incident light is emitted from the array substrate 12 while maintaining the same polarization direction. When a voltage is applied to the liquid crystal layer 16, the light is birefringent according to the applied voltage, the polarization plane is rotated, and the light is emitted from the array substrate 12. Since the reflective electrode 15 has very high smoothness, the light reflectance reaches 90% or more.

Next, the liquid crystal panel of the second invention will be described. FIG. 2 is a sectional view of the liquid crystal panel of the second invention. In FIG. 2, 21 is a polymer dispersed liquid crystal.

The polymer-dispersed liquid crystal will be briefly described below. Polymer dispersed liquid crystals are roughly classified into two types depending on the dispersion state of liquid crystals and polymers. One is a type in which liquid crystals in the form of water droplets are dispersed in a polymer. The liquid crystal exists in the polymer in a discontinuous state. Hereinafter, such a liquid crystal will be referred to as a PDLC, and a liquid crystal panel using the liquid crystal will be referred to as a PD liquid crystal panel. The other is a type that has a structure in which a polymer network is stretched around the liquid crystal layer. It looks like a sponge containing liquid crystal. The liquid crystal does not form a water drop but continuously exists. Hereinafter, such a liquid crystal is called PNLC, and
A liquid crystal panel using the liquid crystal is called a PN liquid crystal panel.
In order to display an image with the above-mentioned two types of liquid crystal panels, light scattering and transmission are controlled.

PDLC utilizes the property that the refractive index is different in the direction in which the liquid crystal is aligned. When no voltage is applied, each water droplet liquid crystal is oriented in an irregular direction. In this state, a difference in refractive index occurs between the polymer and the liquid crystal, and incident light is scattered. When a voltage is applied here, the alignment directions of the liquid crystal are aligned. If the refractive index when the liquid crystal is oriented in a certain direction is matched with the refractive index of the polymer in advance, incident light is transmitted without being scattered.

On the other hand, PNLC uses the irregularity of the alignment of liquid crystal molecules. The incident light is scattered in the irregular alignment state, that is, in the state where no voltage is applied.
On the other hand, light is transmitted when a voltage is applied and the array state is made regular. The above description of the movement of the liquid crystal of PDLC and PNLC is merely a model idea. Although the present invention is not limited to one of the PD liquid crystal panel and the PN liquid crystal panel, it is not limited to the PD liquid crystal panel for ease of explanation.
A liquid crystal panel will be described as an example. Further, PDLC and PNLC are collectively referred to as polymer dispersed liquid crystal, and PD liquid crystal panel and PN liquid crystal panel are collectively referred to as polymer dispersed liquid crystal panel. A liquid containing a liquid crystal to be injected into a polymer dispersed liquid crystal panel is generically called a liquid crystal solution, and a state in which a resin component in the liquid crystal solution is polymerized and cured is called a polymer.

Operation of polymer dispersed liquid crystal (Fig. 3
A brief description will be given using (a) and (b). (Fig. 3 (a)
(B) is an explanatory view of the operation of the polymer dispersed liquid crystal panel. In FIGS. 9 (a) and 9 (b), 31 is an array substrate, 32 is a pixel electrode, 33 is a reflective electrode, 34 is a liquid crystal droplet, 35 is a polymer, and 36 is a counter substrate. A TFT or the like is connected to the pixel electrode 32, and a voltage is applied to the pixel electrode by turning on / off the TFT, thereby changing the liquid crystal alignment direction on the pixel electrode to modulate light. As shown in FIG. 3A, in the state in which no voltage is applied, the water droplet liquid crystals 34 are oriented in irregular directions. In this state, a difference in refractive index occurs between the polymer 35 and the water droplet liquid crystal 34, and incident light is scattered. Here, when a voltage is applied to the pixel electrode as shown in (FIG. 3B), the directions of the liquid crystals are aligned. If the refractive index when the liquid crystal is oriented in a certain direction is matched with the refractive index of the polymer in advance, the incident light is reflected by the reflective electrode 33 and is emitted from the array substrate 31 without being scattered.

Differences from the liquid crystal panel of the first aspect of the present invention will be mainly described. As the liquid crystal 21, the above-mentioned polymer dispersed liquid crystal is used. The liquid crystal of the polymer-dispersed liquid crystal layer 21 is preferably a nematic liquid crystal, a smectic liquid crystal, or a cholesteric liquid crystal, and may be a single or two or more kinds of liquid crystal compounds or a mixture containing a substance other than the liquid crystal compounds. In addition,
Of the above-mentioned liquid crystal materials, cyanbiphenyl nematic liquid crystal is most preferable. The resin material is preferably a transparent polymer, and may be a thermoplastic resin, a thermosetting resin, or a photocurable resin, but it is an ultraviolet curable type from the viewpoint of ease of manufacturing process, separation from the liquid crystal layer, etc. It is preferable to use the above resin. As a specific example, an ultraviolet-curable acrylic resin is exemplified, and a resin containing an acrylic monomer or an acrylic oligomer that is polymerized and cured by ultraviolet irradiation is particularly preferable. By irradiating with ultraviolet rays, these cause a polymerization reaction only in the resin to become a polymer, and only the liquid crystal undergoes phase separation. At this time, when the amount of liquid crystal is smaller than that of the resin component, independent particle-shaped liquid crystal droplets are formed. On the other hand, when the amount of liquid crystal is large, the resin matrix is particulate in the liquid crystal material. , Or exist in the form of a network and the liquid crystals are formed so as to form a continuous layer.

Unless the particle size of the water-drop liquid crystal or the pore size of the polymer network is uniform to some extent and the size is in the range of 0.1 μm to several μm, the incident light scattering performance is poor and the contrast cannot be improved. The particle size of the water-drop liquid crystal or the pore size of the polymer network is preferably in the range of 0.5 μm to 2.0 μm. For this reason, it is necessary to use a material that can be cured in a short time, such as an ultraviolet curable resin. The orientation ratio between the liquid crystal material and the resin material is 95: 5 to 10:90. Above all 70:30
A range of 90:10 is preferred.

The thickness of the liquid crystal layer 21 is 5 μm to 20 μm.
The range of 8 μm to 15 μm is most suitable for the scattering characteristics and the range of applied voltage for driving.
The film thickness may be set so that a maximum transmittance of 90% can be obtained with an applied voltage of 6 to 10V. The array substrate 12
Since the above is the same as that of the conventional liquid crystal panel, the description thereof will be omitted.

In the liquid crystal panel manufacturing method of the present invention, a sealing resin (not shown) is applied onto the array substrate 12.
Then, the counter electrode substrate 11 and the array substrate 12 are aligned and bonded. Liquid crystal injection methods include a vacuum injection method and a pressure injection method. In the vacuum injection method, the bonded substrates are placed in a vacuum chamber, the array substrate 12 and the counter electrode substrate 11 are evacuated, and then the liquid crystal injection port is immersed in a liquid crystal solution. When the vacuum in the vacuum chamber is broken, the liquid crystal solution is injected between both substrates. On the other hand, the pressure injection method uses the counter electrode substrate 11
The liquid crystal solution is injected by pressure from an injection port of 0.8 to 1.2 mm formed in the peripheral portion of the.

The polymer dispersed liquid crystal 21 and the pixel electrode 13
In order to improve the adhesion at the interface with the reflection electrode 15 and the like, an inorganic thin film such as SiO ₂ is added in an amount of 500 to 1000 A.
It is good to form. Further, on the incident surface of the array substrate 12,
An antireflection film is formed according to the wavelength of the light to be modulated.

The operation of the liquid crystal panel is as described in (FIG. 3). The liquid crystal panel of the first aspect of the invention needs to make the light linearly polarized and incident, but the liquid crystal panel of the second aspect of the invention does not need to do so. Therefore, it is possible to easily realize a brightness higher than twice. Light incident from the array substrate side when no voltage is applied to the liquid crystal 21 passes through the pixel electrode 13 and is scattered by the liquid crystal 21. Reflective electrode 15
The light that has reached is further scattered by the liquid crystal layer. Therefore, a large scattering characteristic can be obtained with a thin liquid crystal film thickness. Further, it can be driven at a low voltage, and the black matrix is unnecessary. When a transmissive liquid crystal panel is formed, it is necessary to double the liquid crystal film thickness in order to obtain the same diffusion characteristics.
Since the other points are the same as those of the liquid crystal panel of the first aspect of the present invention, description thereof will be omitted.

The liquid crystal panel according to the third aspect of the present invention will be described below with reference to the drawings. FIG. 4 is a sectional view of the liquid crystal panel of the third invention. In the following description, different parts of the liquid crystal panel of the first aspect of the present invention will be mainly described. In FIG. 4, 41 is a diffraction grating. In addition,
In the figure, a rectangular diffraction grating is shown to facilitate drawing, but the present invention is not limited to this, and may be a triangle, a sawtooth shape, a trapezoidal shape, or a sine curve shape. Among them, the sine curve shape, which is easy to form, is preferable because of its excellent characteristics. Further, the diffraction grating is not limited to the one-dimensional diffraction grating and may be a two-dimensional diffraction grating.

The pitch of the diffraction grating is preferably 3 μm to 20 μm and should be determined theoretically and experimentally by the diffraction grating of the incident light. In the liquid crystal panel of the present invention, the pitch is 6 μm. The height of the diffraction grating is 0.5 μm to 5 μm.
Is preferable, and 1.0 to 3.0 μm is particularly preferable. However, this changes depending on the diffraction grating material, the refractive index of the liquid crystal, and the wavelength of the light to be modulated. In the liquid crystal panel of the present invention, the diffraction grating is made of transparent acrylic resin and has a refractive index n _k of 1.52.
Is. The refractive index n _k is made to substantially match the ordinary refractive index n _o of the liquid crystal 16.

The diffraction grating is not limited to the above materials. For example, as shown in FIG. 6, a convex portion of the diffraction grating 41 is formed on the counter electrode substrate 11 with a resist or the like,
There is also a method of forming the reflective film 61 of Al or the like on the substrate 11 and the convex portion. In addition, 1.0 on the counter electrode substrate 11
There is also a method of forming a metal thin film having a thickness of up to 5 μm and forming irregularities on the metal thin film by etching or the like. Further, a resist having a diffraction grating pattern is applied to the counter electrode substrate 11, and concavities and convexities are directly formed in the counter electrode substrate shape by a chemical etching or reactive ion etching technique or the like, and a reflection film of Al or the like is formed on the concavities and convexities. There is a way to do it. Also,
The diffraction grating may be formed on the pixel electrode 13. The above matters regarding the diffraction grating are the same in the liquid crystal panel of the fourth aspect of the present invention.

Although not shown in FIG. 4, an alignment film is formed on the diffraction grating 41 and the pixel electrode 13, and the alignment process is performed. As for the orientation direction, when the diffraction grating is a one-dimensional diffraction grating, rubbing treatment is performed in the length direction. The pixel electrode 13 is formed at an angle of 45 degrees with the rubbing direction.

The operation of the liquid crystal panel of the third aspect of the present invention will be described below. The liquid crystal 16 is a material having a positive dielectric constant if it is a nematic liquid crystal. If the refractive index of the liquid crystal voltage in the liquid crystal layer is applied, the ordinary refractive index n _o, and the
When no voltage is applied, the extraordinary light refractive index is n _e . Also, n _e >
Let n _o and n _k = n _o . When no voltage is applied to the liquid crystal layer, the refractive index n of the liquid crystal 16 (hereinafter, referred to as an off state)
= N _e , a refractive index difference is generated between the diffraction grating 41 and the light, and the light reaching the reflective electrode is diffracted. On the contrary, when the voltage is applied (hereinafter referred to as “on state”), the refractive index n of the liquid crystal 16 is n.
= Because it is n _o eliminates the difference in refractive index between the refractive index of the liquid crystal 16 of the diffraction grating 41, it will not be diffracted. In the intermediate state between the on state and the off state, light is diffracted according to the alignment state of the liquid crystal. The fact that light is diffracted means that the principal ray angle of incident light is bent. By arranging a lens at the light exit end of the liquid crystal panel so that light that is bent over a certain angle is not collected, the light quantity ratio between the on state and the off state of the liquid crystal (hereinafter called contrast) is increased. can do. Further, since the reflective electrode 15 has a very high smoothness, the reflection efficiency is also very high.

Incidentally, as shown in FIG. 6, the reflection film 6 has an uneven shape.
When 1 is formed, the phenomenon of generation and reduction of the diffraction grating does not occur as described above. Since the diffraction angle changes due to the change in the refractive index, the change in the diffraction angle may be adjusted by the lens arranged at the light emission end of the liquid crystal panel to adjust the ratio of condensing and non-condensing.

The liquid crystal panel according to the fourth aspect of the present invention will be described below with reference to the drawings. FIG. 5 is a sectional view of the liquid crystal panel of the present invention. Items related to the diffraction grating 41 have been described with respect to the liquid crystal panel of the third aspect of the present invention, and will be omitted. Also, regarding the liquid crystal 21 and the TFT, the second matter
Since it has been described in the liquid crystal panel of the present invention, the description thereof will be omitted. Also,
Similar to the liquid crystal panels of the first to third aspects of the present invention, an antireflection film is formed on the light incident surface of the array substrate 12.

In the fourth aspect of the present invention, a reflection type diffraction grating is formed on the counter electrode substrate 11 and the polymer liquid crystal 21 is sandwiched between the counter electrode substrate 11 and the array substrate 12. Further, on the pixel electrode 13 and the diffraction grating 41, in order to improve the adhesion with the polymer-dispersed liquid crystal and the like, a thin film of SiO ₂ of 500 to
About 1000Å is formed.

Hereinafter, the operation of the liquid crystal panel of the fourth aspect of the present invention will be described.
explain about. The refractive index n of the diffraction grating_k， Polymer
Refractive index n_p, Ordinary refractive index n of liquid crystal_o, Extraordinary light refractive index n
_eAnd n_h≒ n_p≒ n_o, N_o> N_eAnd Also, in the liquid crystal
The ratio of the polymer is low. Polymer dispersed liquid crystal
Then, in the ON state, its refractive index n_aIs n_o， Off state knob
Refractive index n during light scattering_x= (2n_o+ N_e) / 3
It Therefore, n_k<N _x, N_k≒ n_oThere is a relationship.
From the above, when the liquid crystal is in the off state, the pixel electrode 13
The light incident from the light source is scattered by the liquid crystal layer 21 and progresses.
The light reaching the emitting electrode is diffracted by the diffraction grating 41,
You can bend the ray direction. N when the liquid crystal is off_k=
n_oTherefore, the diffraction grating 41 disappears. Therefore,
Light incident on the liquid crystal panel reaches the reflective electrode as it is,
It is reflected as it is. The smoothness of the reflective electrode 15 is also high,
Since it is made of Al, etc., the reflection efficiency reaches 95%.
To do. From the above, the light is emitted from the array substrate 12 at the light emitting end.
By placing the lenses, the contrast is very high.
A liquid crystal panel can be realized. In addition, the liquid crystal on state and off
In the intermediate state of the state, the diffraction grating depends on the alignment state of the liquid crystal.
The degree of diffraction of the liquid crystal changes and the scattering state of the liquid crystal 21 layer also changes.
It goes without saying that it will change.

The liquid crystal projection television of the present invention will be described below with reference to the drawings. FIG. 7 is a principle diagram of the liquid crystal projection type television of the first present invention. LCD panel 71
Uses the liquid crystal panel of the first or third aspect of the present invention. A light emitting source such as a 250 W metal halide lamp is arranged in the condensing optical system 113. A concave mirror and an infrared / ultraviolet ray cut mirror (not shown, hereinafter referred to as UVIR cut mirror) are arranged in the condensing optical system 113 so that only visible light is emitted. White light emitted from the condensing optical system is R light, G light, RDM, GDM, and BDM.
It is split into B light and enters the polarization beam splitter 116. The polarization beam splitter 116 reflects the P component light and makes it enter the liquid crystal panel 71. If the incident angle of the incident light on the liquid crystal panel varies depending on the location, image quality unevenness occurs. To avoid this, it is advisable to make the light incident on the liquid crystal panel as parallel as possible. Therefore, it is preferable to use a good telecentric lens having a very small angle of view on the liquid crystal panel side as the projection lens. According to the experiment, it was necessary to set the collection angle to 6 degrees or less. In addition, the liquid crystal panel is liquid-cooled (not shown) because strong light is incident on it. Due to the heat resistance of the liquid crystal panel, the maximum temperature must be 55 degrees or less.

When the liquid crystal panel of the third invention is used,
The height of the diffraction grating of the liquid crystal panel that modulates R light, G light, and B light is changed. Height of diffraction grating of liquid crystal panel for B light modulation <Height of diffraction grating of liquid crystal panel for G light modulation <
It becomes the height of the R light modulation liquid crystal panel. Each liquid crystal panel modulates light in accordance with an applied video signal and converts P component light into S component light. The light is reflected by the reflective electrode and again enters the polarization beam splitter. The polarization beam splitter transmits the S component light. Reference numeral 80 is a polarizing plate. The polarizing plate 80 transmits only the complete S component light. The polarizing plate is arranged because the polarization beam splitter has a very high degree of separation between the P component and the S component when parallel light is incident, but is low when the light is obliquely incident. Light of a certain spread angle is incident on the liquid crystal panel 71. Therefore, the polarization characteristic of the polarization beam splitter becomes low. The polarizing plate 80 is used to correct the degree of polarization. By arranging the polarizing plate 80, the contrast is improved. The polarizing plate 80 may be arranged between the dichroic mirror 114 and the polarization beam splitter 116. Moreover, you may arrange | position in both. Obviously, it is not necessary to dispose the polarizing plate 80 if the contrast of the display pixels is systematically sufficient without disposing the polarizing plate 80.

Also, by disposing a quarter-wave plate (not shown) between the beam splitter 116 and the liquid crystal panel 71, the angle range of light that can be used as the beam splitter can be expanded. The quarter wave plate is arranged so that its fast axis or slow axis is orthogonal to a plane including the incident optical axis and the reflected optical axis of the beam splitter 116. The output light from the condensing optical system 113 enters the beam splitter 22, and the P component light passes through a quarter wavelength and reaches the liquid crystal panel 71. In this case, when the light passes through the quarter-wave plate twice, it becomes linearly polarized light in which the polarization direction is twice rotated in the opposite direction. This polarization direction is a polarization direction in which the beam splitter 116 can be used as an analyzer. From the above, the polarization characteristics are improved.

The light emitted from the polarization beam splitter is projected on the screen 119 by the lens 117. (FIG. 7) shows only the modulation part of one liquid crystal panel, but as shown in (FIG. 14), the copied images of the three liquid crystal panels for R, G, B modulation are at the same position on the screen. The images are projected on top of each other and a full-color image is realized.

It is also possible to realize a color image with a single liquid crystal panel. A mosaic color filter may be formed on the liquid crystal panel 71. In the above configuration (FIG. 7), the dichroic mirror 114 may be replaced with a mirror.

The liquid crystal projection television of the second aspect of the present invention will be described below with reference to the drawings. (Figure 8) is the second
FIG. 3 is a configuration diagram of the liquid crystal projection television of the present invention. As the liquid crystal panel 75, the liquid crystal panel of the second or fourth invention using polymer dispersed liquid crystal is used. A light emitting source such as a metal halide lamp or a xenon lamp is arranged in the condensing optical system 72. In order to improve the telecentricity, it is preferable to use a xenon lamp closer to a point light source. A concave mirror and a UVIR cut mirror are arranged in the condensing optical system 72 so that only visible light is emitted. The white light emitted from the condensing optical system 72 is RDM7.
4c separates the R light, the GDM 74b separates the G light, and the BDM 74a separates the B light. In addition, in (Fig. 8) R, G, B
Since the configurations of the respective light modulation systems are almost the same, the G / R light modulation system is omitted. Also, BDM7
4a can be replaced with a mirror, RDM74c,
It is needless to say that the order of the GDM 74b and the BDM 74a is not limited to this order, and may be, for example, the reverse order.

Reference numeral 75 is a liquid crystal panel of the present invention. In addition,
Among the liquid crystal panels, the liquid crystal panel that modulates the R light has a larger water droplet liquid crystal particle diameter or a larger liquid crystal film thickness than other liquid crystal panels. This is because the longer the wavelength of light, the lower the scattering characteristics. The particle size of the water-drop liquid crystal can be controlled by controlling the intensity of ultraviolet light during polymerization or by changing the material used. The liquid crystal film thickness can be adjusted by changing the bead diameter. Also, the height and pitch of the diffraction grating are red (R).
The liquid crystal panels for green (G) and blue (B) may be changed. The matter has been described with respect to the liquid crystal projection television of the first aspect of the present invention, and will not be described. Further, the matters regarding the liquid crystal layer described above are also applied to the liquid crystal projection television of the fourth aspect of the present invention. Reference numerals 76 and 78 are lenses, and reference numeral 77 is an aperture as a diaphragm. The projection optical system is composed of 76, 77 and 78. A set of 76, 77 and 78 is called a projection lens system as long as there is no particular problem. It is also clear that the aperture is not necessary when the F value of the lens 78 or the like is large, and it is clear that the projection lens system can be replaced by one lens.

The projection lens system plays a role of transmitting parallel light rays transmitted through each liquid crystal panel and blocking light scattered by each liquid crystal panel. As a result, full-color display with high contrast can be realized on the screen 79. The contrast is improved by reducing the aperture diameter D of the aperture. However, the image brightness on the screen is reduced.

The thickness of the liquid crystal layer of the liquid crystal panel of the present invention is 8
When it is ˜15 μm, the condensing angle of the lens is optimally around 6 degrees, and at that time, the contrast is 100: 1 at the center of the screen, and when projected on a 40-inch screen on a rear TV, the screen gain is 200 at a screen gain of 5. [Ft] or more, and a screen brightness equal to or higher than that of a CRT projection television could be obtained.

The operation of the liquid crystal projection television of the present invention will be described below. Since the R, G, and B light modulation systems have substantially the same operation, the B light modulation system will be described as an example. First, white light is emitted from the condensing optical system 72, and the B light component of the white light is BDM74.
It is reflected by a. The B light is incident on the polymer dispersed liquid crystal panel 75a. The polymer dispersed liquid crystal panel (see FIG.
As shown in (a) and (b), the scattering and transmission states of the incident light are controlled by the signal applied to the pixel electrode to modulate the light.

The scattered light is blocked by the aperture 77a, and conversely, the light within a predetermined angle passes through the aperture 77a. The modulated light is enlarged and projected on the screen 79 by the projection lens 78a. As described above, the B light component of the image is displayed on the screen. Similarly, the polymer-dispersed liquid crystal panel for light modulation modulates the light of G light component, and R
The polymer dispersed liquid crystal panel for light modulation modulates the light of the R light component, and a color image is displayed on the screen 79.

The projection lens system in FIG. 8 is not limited to this. For example, a central shield type optical system in which parallel light is shielded by a light shield and scattered light is projected on the screen may be used. Needless to say.

In order to realize color image display with a single panel, a mosaic color filter is formed on the liquid crystal panel as in the liquid crystal projection television of the first aspect of the present invention.
The display image on the liquid crystal panel may be projected by a projection lens.

Liquid Crystal Panel When the liquid crystal panel of the fourth aspect of the present invention is used, the incident destination on the liquid crystal panel is diffracted by the diffraction grating. As a matter of course, as described above, the diffraction grating can be extinguished when the liquid crystal is completely in the ON state. Therefore, when the lens 76 and the like are selected in consideration of the degree of focusing of diffracted light, a display image with high contrast can be realized as compared with the case where the second invention uses a liquid crystal panel. The liquid crystal projection television of the third aspect of the present invention will be described below. FIG. 9 is a principle view of the liquid crystal projection type television of the third present invention. In FIG. 9, a Schlieren optical system is used. The liquid crystal panel of the third aspect of the present invention is used as the liquid crystal panel. The projection light emitted from the projection light source 83 such as a xenon lamp is focused on the mirror 82 by the condenser lens 84. The focused light is reflected by the mirror 82, becomes parallel rays by the schlieren lens 85, and enters the polarization beam splitter. It should be noted that although a drawing for separating the P component light and the S component light should be drawn in the drawing, it is also shown in (FIG. 7), and the polarization beam splitter is indicated by a dotted line to facilitate drawing. There is. The polarization beam splitter splits the light into P and S components, and makes the P component light enter from the array side of the liquid crystal panel 86. Although the light of P component is made incident here, the light is not limited to this, and light of S component may be used as in the liquid crystal projection television of the first aspect of the present invention. The liquid crystal panel 86 converts the P component light into the S component light in accordance with the applied video signal, and
Meanwhile, the light is diffracted and emitted from the array substrate 12 side.
The polarization beam splitter 89 transmits the S component light and makes it incident on the schlieren lens 85. The light incident on the pixel for which the diffraction grating is completely generated is diffracted, enlarged by the schlieren lens 85, and projected on the screen 81. The light incident on the pixel in which the diffraction grating has completely disappeared is reflected as it is, and is shielded by the mirror / Schlieren stop 82. In the intermediate state between the generation and disappearance of the diffraction grating, light corresponding to the diffraction state is projected on the screen 81. Although it has been stated that the light diffracted in the liquid crystal projection type television is projected on the screen by the schlieren lens 85, the invention is not limited to this. Even if the diffracted light is configured by a schlieren optical system that is shielded by a schlieren stop. It goes without saying that it is good.

In the embodiment of FIG. 9 as well, the first
It goes without saying that the contrast can be improved by disposing the polarizing plate 80 in the vicinity of the polarizing beam splitter as in the liquid crystal projection television of the present invention.
The polarization characteristics of the beam splitter can be improved by using the four-wave plate.

Further, as shown in (FIG. 4), even if the generation and disappearance of the diffraction grating cannot be controlled, a display image with high contrast can be realized by appropriately designing the converging angle of the schlieren lens 85. ..

When a color image is obtained, the projection light of the projection light source 83 is separated into R, B and G lights by a dichroic mirror,
A liquid crystal panel that modulates each light may be arranged. A full color image can be obtained by projecting the images modulated by the three liquid crystal panels at the same position on the screen 81.

Finally, the liquid crystal projection type television of the fourth aspect of the present invention will be described. In the principle view of the liquid crystal projection television of the fourth aspect of the present invention (FIG. 9), the beam splitter 89 may be removed and the liquid crystal panel of the fourth aspect of the present invention may be used as the liquid crystal panel 86.

The differences from the liquid crystal projection television of the third aspect of the present invention will be mainly described below. The light made into parallel light by the Shuri lens 85 enters from the array substrate 12 side of the liquid crystal panel 86. The light incident on the liquid crystal panel is scattered according to the applied image signal and is diffracted by the diffraction grating formed on the reflective electrode 15. The diffracted and scattered light is emitted from the array substrate again, and the Schlieren lens 8
It is incident on 5. The subsequent operation is the same as that of the liquid crystal projection type television of the third aspect of the present invention, and therefore its explanation is omitted.

In the liquid crystal projection televisions of the first and third aspects of the present invention, the polarization beam splitter is used as the polarization means, but the polarization means is not limited to this, and a polarization mirror or the like may be used. Needless to say.

In the embodiment of the liquid crystal projection type television of the present invention, the rear type liquid crystal projection type television which displays an image on the transmission type screen is described, but the present invention is not limited to this, and the image is displayed on the reflection type screen. Needless to say, it may be a front type liquid crystal projection type television which displays. Further, although the color separation is performed by the dichroic mirror, the present invention is not limited to this, and the color separation may be performed by using, for example, an absorption type color filter.

Further, in the embodiment of the liquid crystal projection type television of the present invention, one projection lens system is provided for each of the R, G and B light modulation systems, but the invention is not limited to this. It goes without saying that, for example, a configuration may be adopted in which light modulated by the three liquid crystal panels is combined into one using a mirror or the like, and then the light is incident on one projection lens system and projected.

[0066]

As described above, in the liquid crystal panel of the present invention, the pixel electrode is formed of the transparent electrode, and the counter electrode is made of the metal substance to be the reflective electrode. Therefore, since the reflective electrode can have a good mirror surface, the light reflection efficiency can be greatly improved. Therefore, if a liquid crystal projection type television is constructed by using the liquid crystal panel of the present invention, high brightness image display and large screen display can be realized.

In the conventional liquid crystal panel, the counter electrode is I
Since it is formed of TO or the like, it has a high resistance value, which may cause uneven brightness in the display image. However, in the liquid crystal panel of the present invention, the counter electrode is formed of a metal substance such as Al. Therefore, the resistance value is low, and the above-mentioned problems do not occur at all.

Further, in the conventional reflection type liquid crystal panel, it is desired to cause the alignment defect on the reflection electrode, but with the configuration of the present invention, sufficient smoothness can be obtained on the reflection electrode and the pixel electrode. Alignment failure does not occur at all.

Further, by using the polymer dispersed liquid crystal as the liquid crystal, it is not necessary to use the polarizing element, and it is possible to realize the brightness higher than twice as high as that using the nematic liquid crystal.

Further, by using a polymer dispersed liquid crystal as the liquid crystal and adopting a reflective structure, it is possible to obtain the same scattering / transmission characteristics with a liquid crystal film thickness of 1/2 as compared with the transmissive liquid crystal panel. Since the voltage can also be reduced, low power consumption can be realized.

In addition, by using the reflection electrode as a reflection diffraction grating, the diffracted light can be emphasized by changing the refractive index of the liquid crystal by the applied voltage. Therefore, a liquid crystal projection type television using the liquid crystal panel of the present invention cannot display a multi-gradation, high contrast image.

Further, by using the polymer-dispersed liquid crystal, the rubbing treatment and the formation of the alignment film, which are necessary when using the nematic liquid crystal, are unnecessary, and the manufacturing cost of the liquid crystal panel can be reduced. Further, although the rubbing process on the diffraction grating was often defective, it is not necessary for the polymer dispersed liquid crystal as a matter of course.

Further, by setting the refractive index of the diffraction grating to be substantially the same as the ordinary refractive index of the liquid crystal, the diffraction grating can be generated or eliminated by the voltage applied to the liquid crystal. Therefore, the contrast can be very high,
Good image display can be realized. By changing the average particle diameter or pore diameter of the water-drop liquid crystal, or changing the height of the diffraction grating, etc., corresponding to each of the R, G, and B wavelengths, the contrast at each wavelength is significantly increased. Has been improved to realize high-quality video display.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a liquid crystal panel according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a liquid crystal panel according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram of the operation of the polymer dispersed liquid crystal.

FIG. 4 is a cross-sectional view of a liquid crystal panel according to an embodiment of the present invention.

FIG. 5 is an explanatory diagram of a liquid crystal panel according to an embodiment of the present invention.

FIG. 6 is a cross-sectional view of a liquid crystal panel according to an embodiment of the present invention.

FIG. 7 is a principle diagram of a liquid crystal projection television according to an embodiment of the present invention.

FIG. 8 is a configuration diagram of a liquid crystal projection television according to an embodiment of the present invention.

FIG. 9 is a principle diagram of a liquid crystal projection television according to an embodiment of the present invention.

FIG. 10 is an equivalent circuit diagram of a liquid crystal panel.

FIG. 11 is a cross-sectional view of a conventional liquid crystal panel.

FIG. 12 is a principle diagram of a conventional liquid crystal projection television.

FIG. 13 is an explanatory diagram of the operation of the reflective liquid crystal panel.

FIG. 14 is a configuration diagram of a liquid crystal projection television.

[Explanation of symbols]

 11, 36, 106 Counter electrode substrate 12, 31 Array substrate 13, 32 Pixel electrode 14 TFT 15, 33, 104 Reflective electrode 16 Nematic liquid crystal 17, 18, 111, 112 Alignment film 21 Polymer dispersed liquid crystal 34 Water drop liquid crystal 35 Polymer 41 Diffraction Grating 61 Reflective Film 71, 86 Liquid Crystal Panel 80 Polarizing Plate 72 Condensing Optical System 77 Aperture 82 Mirror 83 Projection Light Source 84 Condenser Lens 85 Schlieren Lens 89, 116 Beam Splitter 107 Nematic Liquid Crystal 103 Insulating Layer

Claims (14)

[Claims] 1. A light-transmitting pixel electrode formed on a first substrate, a switching element for applying a signal to the pixel electrode, and a reflective electrode formed on a second substrate. A liquid crystal panel, wherein a nematic liquid crystal is sandwiched between the first and second substrates, and an alignment film for controlling the alignment of the nematic liquid crystal is provided on the pixel electrode and the reflective electrode. 2. A light-transmitting pixel electrode formed on a first substrate, a switching element for applying a signal to the pixel electrode, and a reflective electrode formed on a second substrate. A liquid crystal panel, wherein a polymer dispersed liquid crystal is sandwiched between the first and second substrates. 3. A light-transmitting pixel electrode formed on a first substrate, a switching element for applying a signal to the pixel electrode, and a reflective electrode formed on the second substrate. A diffraction grating is provided on at least one of the first substrate and the second substrate, a nematic liquid crystal is sandwiched between the first and second substrates, and on the pixel electrode and the diffraction grating. A liquid crystal panel having an alignment film for controlling the alignment of nematic liquid crystal. 4. A light-transmitting pixel electrode formed on a first substrate, a switching element for applying a signal to the pixel electrode, and a reflective electrode formed on a second substrate. A liquid crystal comprising a diffraction grating on at least one of the first substrate and the second substrate, and a polymer dispersed liquid crystal sandwiched between the first and second substrates. panel. 5. The liquid crystal panel according to claim 3, wherein the diffraction grating is a reflection type diffraction grating or a reflection type phase grating. 6. The liquid crystal panel according to claim 3, wherein the pitch of the diffraction grating is 2 μm to 20 μm. 7. The liquid crystal panel according to claim 1 or 3, wherein the liquid crystal layer has a thickness of 2 to 10 μm. 8. The liquid crystal panel according to claim 1 or 3, a light generating means, a deflecting means for polarizing and separating the light generated by the light generating means and irradiating the light to the liquid crystal panel, and modulation by the liquid crystal panel. A liquid crystal display device comprising: an optical element component that projects the emitted light. 9. The liquid crystal panel according to claim 2 or 4, a light generating means, a first optical element part for guiding the light generated by the light generating means to the liquid crystal panel, and modulation by the liquid crystal panel. A liquid crystal display device comprising a second optical element component for projecting reflected light. 10. A liquid crystal panel according to claim 3, a light generating means, a polarizing means for polarizing and separating the light generated by the light generating means and irradiating the liquid crystal panel, and a schlieren for projecting an image on the liquid crystal panel. A liquid crystal display device comprising an optical system. 11. A liquid crystal panel according to claim 4, a light generation means, an irradiation means for irradiating the liquid crystal panel with light generated by the light generation means, and a Schlieren optical system for projecting an image of the liquid crystal panel. A liquid crystal display device comprising: 12. The light generated by the light generating means is divided by a color filter into light of three predetermined wavelengths, blue light, green light and red light, and the liquid crystal panel has a wavelength of the three predetermined ranges. The liquid crystal display device according to claim 8, wherein the liquid crystal display device is arranged for at least one of the lights. 13. An optical element for forming an optical image of a liquid crystal panel that modulates blue light, an optical image of a liquid crystal panel that modulates green light, and an optical image of a liquid crystal panel that modulates red light.
The liquid crystal display device according to claim 8, wherein the image is projected on the same position on the screen. 14. The liquid crystal display device according to claim 12, wherein the color filter is a dichroic mirror.