JPH0618935A - Liquid crystal electro-optical device - Google Patents

Abstract

PURPOSE:To facilitate the orientation control of a liquid crystal and to speed up a response speed by providing a TFT which is longer in channel length than the length in the channel direction of a gate electrode as a switching element for a liquid crystal. CONSTITUTION:A material which can be anodically oxidized is selected for the gate electrode part constituting the gate electrode 15 and an oxide layer 16 and the surface part thereof is anodically oxidized to form the oxide layer 16. The distance between a source region 20 and drain region 21 which are regions to be implanted with ions, i.e., channel length 28, is made longer by about nearly twice the thickness of the oxide layer 16 than the substantial length in the channel length direction of the gate electrode 15. Consequently, the electric fields by the gate electrode 15 are not applied at all in the parts 26 and 27 in the channel region 19 which face each other via the gate insulating film 17 on the oxide layer 16 formed on both flanks of the gate electrodes 15 or the electric fields are extremely weaker than in the parts perpendicularly under the gate electrode. Since the nematic liquid crystal having the positive anisotropy of a dielectric constant is used, the orientation control of the liquid crystal is extremely easy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electro-optical device using a nematic liquid crystal which uses a thin film transistor and has excellent characteristics such as high speed response and high contrast and a steep response to an applied voltage.

[0002]

2. Description of the Related Art Conventionally, a TN (Twisted Nematic) type liquid crystal electro-optical device has been used as a display element for a timepiece, a calculator and the like. The configuration of this TN type liquid crystal electro-optical device will be briefly described.

By injecting nematic liquid crystals having a positive dielectric constant anisotropy between substrates which are oriented at an angle of 90 ° to each other, twist orientation of liquid crystal molecules occurs. When an electric field is applied to this liquid crystal, the long axis of the liquid crystal molecules is aligned at right angles to the substrate due to the interaction between the electric field and the dielectric anisotropy. Then, the state of the liquid crystal molecules when no voltage is applied to the liquid crystal (twist) and the state when a voltage is applied are distinguished by using a polarizing plate. Alternatively, on the contrary, there is also a method of interposing a nematic liquid crystal having a negative dielectric anisotropy between one of the substrates subjected to the vertical alignment treatment.

Further, recently, research on ferroelectric liquid crystals has made great progress. The configuration of the optical device using the ferroelectric liquid crystal is about 2 μm, which is considerably thinner than that of the TN type liquid crystal device, and the substrates subjected to the liquid crystal alignment treatment are bonded to each other, and the liquid crystal is injected between the substrates. To do. Ferroelectric liquid crystal molecules have two stable states when no electric field is applied, and the molecules are aligned in one stable state when an electric field is applied. Then, by applying an electric field in the opposite direction, the molecules are oriented in another stable state. Brightness and darkness are displayed by distinguishing the states of these two liquid crystals using a polarizing plate.

In the case of an optical device using this ferroelectric liquid crystal, the response time is very fast, about several tens of microseconds, so that it has been expected to be applied to various fields.

Alternatively, there is also an active type in which switching elements such as TFT and MIM are arranged in each pixel.

Further, there is STN type liquid crystal in which the twist angle of the nematic liquid crystal is 180 ° to 270 °.

[0008]

However, the above-mentioned T
In the N-type liquid crystal electro-optical device, a liquid crystal alignment film must be formed on both of the pair of substrates, and further, the alignment films on the pair of substrates must be subjected to a rubbing treatment so that they are at 90 ° to each other. There wasn't. Furthermore, since the response time of the TN type liquid crystal electro-optical device is very slow, such as several tens of milliseconds, and the steepness of the response to the applied voltage is poor, the application range other than the display of a small area such as a clock and a calculator is narrowed down. It was Then, in order to further improve the response speed, a method of shortening the substrate interval can be considered, but if the substrate interval is shortened, the liquid crystal can be twisted by 90 ° between one substrate and the other substrate. Disappear.

Although the response time is certainly fast in the electro-optical device using the ferroelectric liquid crystal, there are many problems.

The first problem is that it is very difficult to control the alignment of the liquid crystal. Conventionally, in addition to the rubbing treatment, a method of oblique vapor deposition of silicon oxide, a method of applying a magnetic field, a temperature gradient method, or the like has been performed. However, even if any method is used, uniform alignment cannot be obtained at present. Therefore, high contrast cannot be obtained.

Secondly, a liquid crystal exhibiting a smectic phase can be used as the ferroelectric liquid crystal. Therefore, the ferroelectric liquid crystal has a layer structure peculiar to the smectic liquid crystal. Once this layer structure is destroyed by an external force, it cannot be restored even if the external force is removed. In order to restore this, it is necessary to heat it to cause it to undergo a phase transition to an isotropic phase once, so a ferroelectric liquid crystal having a layer structure that is destroyed by a small external impact is not practical.

Thirdly, in the ferroelectric liquid crystal, charges are accumulated at the interface with the alignment film due to the spontaneous polarization of the liquid crystal itself, and an electric field opposite to the polarization of the liquid crystal is formed. If you display it, the next time you try to display a different screen,
There is a problem that the previous display remains (called “burn”).

Fourthly, the contrast ratio of the electro-optical device using the ferroelectric liquid crystal largely depends on the tilt angle (or cone angle) of the liquid crystal, but the tilt angle (cone angle) of the maximum contrast ratio can be obtained. Value is 22.5 ° (45 °)
Is known to be. However, a liquid crystal satisfying only the condition that the tilt angle (cone angle) is 22.5 ° (45 °) has already been synthesized, but there are other important conditions, such as the problem of the temperature range in which the liquid crystal exhibits ferroelectricity, Ferroelectric liquid crystals have not yet been developed that can satisfy the problem of responsiveness to AC pulses at the same time. Therefore, at present, the problem of the temperature range is emphasized rather than the tilt angle. Therefore, the contrast ratio of the electro-optical device using the ferroelectric liquid crystal, which is currently in the research stage, is not so large. Due to the above-mentioned problems, it is very difficult at present to apply the ferroelectric liquid crystal as a display device.

[0014]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention is a liquid crystal electro-optical device in which a nematic liquid crystal having a positive dielectric anisotropy is interposed between a pair of substrates. A liquid crystal alignment layer in which an organic substance is rubbed is provided on a surface of one of the substrates which is in contact with the liquid crystal, and one of the pair of substrates has a channel length longer than a length of the gate electrode in the channel direction. The TFT is provided as a liquid crystal switching element.

In the present invention, the liquid crystal alignment layer may have a liquid crystal alignment film formed on the surfaces of a pair of substrates which are in contact with both liquid crystals, and in that case, the rubbing treatment may be applied to only one substrate, It may be applied to both substrates. However, when applied to both substrates, the directions should be substantially parallel. Here, “parallel” means that the rubbing directions of the substrates are 0 ° or 180 ° (antiparallel).

The liquid crystal used in the present invention may be cholesteric (chiral nematic) liquid crystal, but nematic liquid crystal is preferred. In the present invention, the conventional T
The substrate spacing of the N-type liquid crystal electro-optical device is approximately 8 μm, whereas the present invention is approximately 5 μm or less, preferably 3.5 μm.
Since a thin substrate distance of m or less is used, the rubbing effect can be exerted on the entire liquid crystal even if only one of the substrates is rubbed, and liquid crystal molecules can be aligned almost in the rubbing direction in the entire liquid crystal layer. .

In the present invention, the liquid crystal 90
Since a twisted orientation of 0 ° is not generated, it is not possible to perform conventional display utilizing the light-transmittance. Therefore,
In the present invention, a display utilizing the refractive index anisotropy of liquid crystal is performed. Further, the gate electrode used in the present invention can be mainly titanium (Ti), aluminum (Al), tantalum (Ta), chromium (Cr) alone, or an alloy thereof.

FIG. 1 shows a basic structure (one example) of a TFT that can be used in the present invention. A blocking layer 24 is provided on an insulating substrate 25, and a source region 20, a drain region 21, and a channel region 19 are provided as semiconductor layers on the blocking layer 24.
To provide. On the channel region 19, a gate insulating film 17 and a gate electrode 15 on which an anodizable material is anodized to form an oxide layer 16 which is an insulating layer are formed. A source electrode 22 and a drain electrode 23 are provided in contact with the source region and the drain region, respectively.

As shown in FIG. 1, a material that can be anodized is selected for the gate electrode portion to be the gate electrode 15 and the oxide layer 16, and the surface portion thereof is anodized to form the oxide layer 16. Source region 20 which is the region of ion implantation
Between the drain region 21 and the drain region 21, that is, the channel length 28
Is about twice as long as the thickness of the oxide layer 16 than the substantial length of the gate electrode 15 in the channel length direction. The material of the gate electrode portion is mainly titanium (Ti), aluminum (Al), tantalum (Ta), chromium (C).
r), silicon (Si) simple substance, or alloys thereof are suitable.

As a result, no electric field due to the gate electrode is applied to the portions 26 and 27 in the channel region 19 facing the oxide layer 16 formed on both side surfaces of the gate electrode with the gate insulating film 17 interposed therebetween, or It is much weaker than the vertical bottom.

In this TFT manufacturing method, a gate electrode portion is formed of a material that can be anodized after forming a semiconductor layer to be a source, a drain, a channel region and a gate insulating film layer 17, and then the semiconductor layer is made to be p-type. Alternatively, impurity ions for making it n-type are implanted to form the source region 20 and the drain region 21, and then the surface portion of the gate electrode portion is anodized to form the gate electrode 15 and the oxide layer 16, and a heat treatment process or the like is performed. , Is.

Alternatively, after forming the semiconductor layer and the gate insulating film layer 17 and forming a gate electrode portion with a material that can be anodized, the surface portion of the gate electrode portion is anodized to form the gate electrode 15 and the oxide layer 16. Alternatively, a step of forming the source region 20 and the drain region 21 by implanting impurity ions for making the semiconductor layer p-type or n-type and then performing a heat treatment step may be performed.

By taking the above steps, an insulated gate field effect transistor whose channel length is longer than the length of the gate electrode in the channel length direction can be easily and surely produced without causing performance variations due to mask misalignment. It becomes possible to manufacture it.

[0024]

In the present invention, since nematic liquid crystal having a positive dielectric constant anisotropy is used, it is very easy to control the alignment of the liquid crystal, and since a layer is not formed unlike smectic liquid crystal, the alignment is once disturbed by an external force. Even after the removal of the external force, it is not necessary to heat the isotropic phase or the nematic phase because the orientation is immediately restored after the external force is removed.

Further, although the nematic liquid crystal is used, the alignment layer may be formed on only one side of the substrate or may be formed on both sides. When formed on both substrates, the rubbing treatment may be performed on only one substrate, or both substrates may be treated in parallel.

When the alignment layer is formed only on one of the substrates, the number of steps can be reduced as compared with the conventional method, and when the alignment layers are formed on both substrates, ITO having a large unevenness is generally used.
It is possible to remove the adverse effect on the alignment of the liquid crystal on the surface of the transparent electrode such as, when the alignment layer is formed on both substrates and the rubbing treatment is performed in parallel, the alignment regulating force of the substrate on the liquid crystal molecules becomes strong, It is possible to shorten the response time (referred to as the fall time) of the liquid crystal when the electric field is applied to the liquid crystal and the long axis of the liquid crystal molecule is changed from the state in which the electric field is removed to the state in which the electric field is removed.

When the nematic liquid crystal is aligned without twisting, a considerably large voltage (10 V or more) is usually required to drive the nematic liquid crystal, but the activated channel region as in the present invention is not required. A large voltage can be applied by using the TFT provided.

Further, according to the present invention, in a conventional TFT having an activated channel portion such as polycrystal, the channel length becomes the gate when the OFF current (the drain current when the gate electrode is OFF) becomes large. By using a TFT longer than the length of the electrode in the channel length direction, this is covered, the OFF current is lowered, and the voltage holding ratio of the element is increased to enable clear display.

In addition, in any case of the present invention, the response time of the liquid crystal is much faster than that of the conventional TN type liquid crystal, and the rise time when an electric field is applied is about several tens of microseconds. , This value almost corresponds to the response time of the ferroelectric liquid crystal. Moreover, since the TFT element is used in the present invention, a large screen display can be performed regardless of whether the voltage-transmission curve of the liquid crystal is steep or not. Examples will be shown below.

[0030]

【Example】

[Embodiment 1] In this embodiment, a viewfinder for a video camera using a liquid crystal electro-optical device having a diagonal of 1 inch was manufactured and the present invention was carried out. In this embodiment, the number of pixels is 387 × 128, and the high mobility TFT by the low temperature process having the structure of the present invention is used.
An element using (thin film transistor) was formed to form a viewfinder. FIG. 3 shows how the active elements are arranged on the substrate of the liquid crystal display device used in this embodiment, and FIG. 2 shows a circuit diagram of this embodiment. A manufacturing process showing the AA ′ cross section and the BB ′ cross section of FIG. 3 is drawn in FIG. AA 'cross section shows NTFT, BB' cross section shows P
A TFT is shown.

In FIG. 4A, an inexpensive glass substrate 5 that can withstand a heat treatment at 700 ° C. or lower, for example, about 600 ° C.
1. A silicon oxide film as the blocking layer 52 is formed on the substrate 1 by using a magnetron RF (radio frequency) sputtering method in an amount of 1000 to 3
It is made to a thickness of 000Å. Process condition is oxygen 100
% Atmosphere, film forming temperature 150 ° C., output 400 to 800 W,
The pressure was 0.5 Pa. The film formation rate using quartz or single crystal silicon for the target was 30 to 100 Å / min.

A silicon film was formed thereon by LPCVD (Low Pressure Vapor Phase) method, sputtering method or plasma CVD method. When forming by the reduced pressure vapor phase method, it is 1 more than the crystallization temperature.
450-550 ° C, which is low by 00-200 ° C, for example, 530 ° C
CVD of disilane (Si ₂ H ₆ ) or trisilane (Si ₃ H ₈ )
The film was supplied to the apparatus to form a film. The reactor pressure is 30-300
It was Pa. The film forming rate was 50 to 250 Å / min.
Threshold voltage (Vt) between PTFT and NTFT
In order to control the concentration to be substantially the same as that of h), boron may be added during the film formation with diborane at a concentration of 1 × 10 ¹⁵ to 1 × 10 ¹⁸ cm ⁻³ .

When the sputtering method is used, the back pressure before sputtering is set to 1 × 10 ^-5 Pa or less, the single crystal silicon is used as the target, and the atmosphere is mixed with 20-80% of hydrogen in argon. For example, argon is 20% and hydrogen is 80%.
The film forming temperature was 150 ° C., the frequency was 13.56 MHz, the sputter output was 400 to 800 W, and the pressure was 0.5 Pa.

When a silicon film is formed by the plasma CVD method, the temperature is, for example, 300 ° C., and monosilane (SiH ₄ ) or disilane (Si ₂ H ₆ ) is used. These were introduced into a PCVD apparatus, and high-frequency power of 13.56 MHz was applied to form a film. The film formed by these methods preferably has oxygen of 5 × 10 ²¹ cm ⁻³ or less. If this oxygen concentration is high, it is difficult to crystallize and the thermal annealing temperature must be high or the thermal annealing time must be long. On the other hand, if the amount is too small, the leak current in the off state increases due to the backlight. Therefore, 4 × 10 ¹⁹ to 4 × 10 ²¹ cm ^-3
And the range. Hydrogen is 4 × 10 ²⁰ cm ^-3 and silicon is 4 × 10
It was 1 atom% when compared with ²² cm ^-3 .

By the above method, a silicon film in an amorphous state is formed to a thickness of 500 to 5000Å, for example 1500Å, and then a heat treatment at a medium temperature in a non-oxide atmosphere at a temperature of 450 to 700 ° C. for 12 to 70 hours, For example, it was held at a temperature of 600 ° C. in a hydrogen atmosphere. Since the amorphous silicon oxide film is formed on the surface of the substrate below the silicon film, no specific nuclei are present in this heat treatment, and the whole is uniformly annealed. That is, it has an amorphous structure at the time of film formation, and hydrogen is simply mixed therein.

The annealing causes the silicon film to shift from an amorphous structure to a highly ordered state, and a part of the silicon film assumes a crystalline state. In particular, a region having a relatively high degree of ordering after the film formation of silicon tends to be crystallized and become a crystalline state. However, since silicon existing between these regions is bonded to each other, the silicon members pull each other. Peak 522 of single crystal silicon as measured by laser Raman spectroscopy
Peaks shifted to lower frequencies than cm ^-1 are observed. The apparent particle size is 50 to 5 when calculated from the full width at half maximum.
Although it is a microcrystal like 00Å, in reality there are many highly crystalline regions with a cluster structure, and each cluster has a semi-amorphous structure in which silicon is bonded (anchoring) with each other. Could be formed.

As a result, the coating is in a state in which it may be said that there is substantially no grain boundary (hereinafter referred to as GB). Since the carriers can easily move between the clusters through the anchored portions, the carrier mobility is higher than that of polycrystalline silicon in which so-called GB is clearly present. That is, hole mobility (μh) = 10 to ²⁰⁰ cm ² /
VSec, electron mobility (μe) = 15 to 300 cm ² / V
Sec is obtained. On the other hand, the film may be polycrystallized by a high temperature anneal at 900 to 1200 ° C. instead of the anneal at a medium temperature as described above, but in that case, segregation of impurities in the film by solid phase growth from nuclei. As a result, impurities such as oxygen, carbon, and nitrogen increase in GB, and the mobility in the crystal is large, but a barrier is created in GB and the movement of carriers there is hindered. 10 cm as a result
^The reality is that it is difficult to obtain a mobility of ² / Vsec or higher. Therefore, it is necessary to set the concentration of impurities such as oxygen, carbon, and nitrogen to one-several to several tenths of that of semi-amorphous ones. If you do so, 50-100 cm ² /
Vsec was obtained.

The silicon film thus formed was photoetched to form a semiconductor layer 53 for NTFT (channel width 20 μm) and a semiconductor layer 54 for PTFT. A silicon oxide film to be a gate insulating film is formed on the surface of the film by 500 to 200
It was formed to a thickness of 0Å, for example, 1000Å. This was performed under the same conditions as the production of the silicon oxide film as the blocking layer.
A small amount of fluorine may be added during film formation to immobilize sodium ions.

After that, an aluminum film was formed on the upper side. This is patterned with a photomask and shown in FIG.
(B) was obtained. The gate insulating film 55 for the NTFT and the gate electrode portion 56 are formed, and the length in the channel length direction of both is 1
0 μm, that is, the channel length was 10 μm. Similarly,
A gate insulating film 57 for PTFT and a gate electrode portion 58 were formed, and the length of both of them was 7 μm, that is, the channel length was 7 μm. In addition, both gate electrode portions 5
The thicknesses of 6 and 58 were both 0.8 μm. In FIG. 4C, boron (B) was added to the source 59 and the drain 60 for the PTFT by an ion implantation method in a dose amount of 1 to 5 × 10 ¹⁵ cm ⁻² . Next, as shown in FIG. 4D, a photoresist 61 was formed using a photomask. N
Phosphorus (P) is used as the source 62 and the drain 63 for the TFT.
Was added by an ion implantation method at a dose amount of 1 to 5 × 10 ¹⁵ cm ^-2 .

Then, the gate electrode portion was anodized. L-tartaric acid was diluted with ethylene glycol at a concentration of 5% and the pH was adjusted to 7.0 ± 0.2 with ammonia. The substrate was dipped in the solution, the + side of the constant current source was connected, the platinum electrode was connected to the − side, a voltage was applied in a constant current state of 20 mA, and oxidation was continued until reaching 150 V. Furthermore, at constant voltage at 150V, add 0.1mA
Oxidation was continued until: In this way, the aluminum oxide layer 64 was formed on the surfaces of the gate electrode portions 56 and 58 to obtain the gate electrode 65 for NTFT and the gate electrode 66 for PTFT. Aluminum oxide layer 64 is 0.3
It was formed to a thickness of μm.

Next, heating anneal was performed again at 600 ° C. for 10 to 50 hours. The source 62 and the drain 63 of the NTFT, the source 59 and the drain 60 of the PTFT are produced as N ⁺ and P ⁺ by activating impurities. Channel forming regions 67 and 68 are formed as semi-amorphous semiconductors under the gate insulating films 55 and 57. This TFT
In the production of, the order of ion implantation of impurities and anodic oxidation around the gate electrode may be exchanged.

Since the insulating layer made of metal oxide is formed around the gate electrode in this manner, the substantial length of the gate electrode is twice the thickness of the insulating film rather than the channel length, in this case 0. It was shortened by 0.6 μm, and the leak current at the time of reverse bias could be reduced by providing the offset region where no electric field is applied. In this embodiment, thermal annealing was performed twice in FIGS. 4 (A) and 4 (E). But Figure 4
The anneal of (A) may be omitted depending on the desired characteristics, and both may be combined with the anneal of FIG. 4 (E) to reduce the manufacturing time. In FIG. 4E, an interlayer insulator 69 was formed as a silicon oxide film by the above-described sputtering method. The silicon oxide film may be formed by using the LPCVD method, the photo CVD method, or the atmospheric pressure CVD method. Interlayer insulation is 0.2-0.6
It was formed to a thickness of μm, for example 0.3 μm, and then a window 70 for an electrode was formed using a photomask. further,
As shown in FIG. 4 (F), aluminum is formed on all of them by a sputtering method, and leads 71, 73 and contacts 72 are formed using a photomask, and then the surface is planarized with an organic resin 74 such as a translucent polyimide. A resin was applied and formed, and electrode holes were formed again using a photomask.

ITO (indium tin oxide film) was formed by the sputtering method so that the two TFTs have a complementary structure and the output terminal thereof is connected to the electrode of one pixel of the liquid crystal device as a transparent electrode. It was etched with a photomask to form the electrode 75. This ITO
Was formed at room temperature to 150 ° C. and was accomplished by oxygen at 200 to 400 ° C. or anneal in the atmosphere. In this way, the NTFT 76, the PTFT 77, and the transparent conductive film electrode 75 are formed.
And were manufactured on the same glass substrate 51. TFT obtained
The electrical characteristics of PTFT are mobility 20 (cm ² / Vs),
Vth is -5.9 (V), and mobility is 40 (cm) with NTFT.
² / Vs) and Vth were 5.0 (V).

One substrate for a liquid crystal device was manufactured according to the method as described above. The arrangement of electrodes and the like of this liquid crystal display device is shown in FIG. The NTFT 76 and the PTFT 77 are provided at the intersection of the first signal line 40 and the second signal line 41. A matrix structure using such C / TFT is provided. The NTFT 76 is connected to the second signal line 41 via the lead 71 at the input end of the drain 63, and is connected to the gate 5
Reference numeral 6 is connected to the signal line 40 on which the multilayer wiring is formed. The output end of the source 62 is connected to a pixel electrode 75 via a contact 72.

On the other hand, in the PTFT 77, the input end of the drain 60 is connected to the second signal line 41 via the lead 73,
The gate 58 is connected to the signal line 40, and the output end of the source 59 is connected to the pixel electrode 75 via the contact 72 like the NTFT. This embodiment is constructed by repeating such a structure horizontally and vertically.

Next, as a second substrate, ITO (indium tin oxide film) was also formed by sputtering on a substrate in which a silicon oxide film was laminated in 2000 liters on a soda lime glass by sputtering. This ITO is room temperature to 150
The film was formed at a temperature of 200 ° C., and was achieved by oxygen at 200 to 400 ° C. or an anneal in the atmosphere. Further, a color filter was formed on this substrate to obtain a second substrate. Then, a polyamic acid is applied on the first substrate and the second substrate by an offset printing method and heated at 250 ° C. for 3 hours to obtain a polyimide film as a liquid crystal alignment film. Then, after rubbing with a cotton cloth, seal printing was performed with a screen printing method.

Then, SiO ₂ particles having a diameter of 2.8 μm were dispersed as spacers on the TFT fabrication substrate and bonded to the substrate on which the seal was printed. At this time, the rubbing directions of the two substrates are made parallel to each other. The distance between the substrates was measured by an interference cell thickness gauge at five points, and it was 2.7 to 2.8 microns. After injecting the liquid crystal, observation with a polarization microscope revealed that the liquid crystal molecules were aligned in the rubbing direction in the entire liquid crystal layer. Then, the polarizing plate was attached to the liquid crystal cell so as to form a crossed Nicols. At this time,
The polarization axis of the polarizing plate on the side where the light is incident is 45 with respect to the rubbing direction.
It was set to °. Then, by applying a voltage to the TFT element, the response speed of the liquid crystal was observed using an oscilloscope. The drain voltage used at this time is 5V to 20
V, the frequency is 75 Hz. The liquid crystal used is ZLI-4.
792 (manufactured by Merck) and the alignment film is LP (manufactured by Toray)
Is. As a result, a response speed of 10 msec to 50 μsec was obtained. This is about 10 to 1000 times faster in rising speed than the conventional TN type liquid crystal electro-optical device, and almost corresponds to the response time of the ferroelectric liquid crystal. Then, the liquid crystal driver was connected by the COG method. Thus, a transmissive liquid crystal display device was obtained. In this embodiment, the complementary T
Although the case of FT is shown, only N type or P type may be used.

[Embodiment 2] In Embodiment 1, the case where a transmissive panel was manufactured was described, but in this embodiment, a reflective type is described. In this case, two polarizing plates may be used as in the transmissive type, but even one sheet can be displayed, and a bright screen can be obtained as compared with a normal reflective type display. After the ITO electrode was formed on the substrate on which the TFT was formed in the same manner as in Example 1, the electrodes were formed on the electrode formation surfaces of the two substrates.
A polyimide thin film was obtained in the same manner as in. Then, a rubbing treatment was performed using a cotton cloth on the polyimide production surface of one of the substrates. 1.4 micron SiO ₂ particles were sprinkled as spacers. The distance between the seal printed printed counter substrate and the bonded cell was measured by a known interference method, and then nematic liquid crystal was injected by a vacuum injection method. In addition, about the board | substrate space | interval, although it measured at 5 places, it was 1.3-1.4 micrometers.

After the liquid crystal injection port was sealed, a polarizing plate was attached to the front surface of the panel and a reflection plate was attached to the back surface. At this time, the angle of the polarization axis of the polarizing plate is 45 ° with respect to the rubbing axis.
Angle. In this way, a circuit for driving the liquid crystal was connected to complete a reflective liquid crystal panel.

[Embodiment 3] In this embodiment, a case where the present invention is applied to a color projector will be described with reference to FIG. Since the projector according to this embodiment does not use a color filter, it is possible to manufacture a bright projector having higher transmittance than the conventional one.

In FIG. 5, the wavelength 63 is set as the red light source 81.
A He-Ne laser having a peak near 3 nm, an Ar laser having a peak near a wavelength of 515 nm as a green light source 82, and an Ar laser having a peak near a wavelength of 477 nm as a blue light source 83 are used to emit these laser lights. The liquid crystal panels 85 and 8 manufactured in Example 1 were processed by the optical system 84 so that the outer shape and the light density were adjusted to the necessary light conditions.
Irradiate 6,87 (excluding color filter). The light passing through the liquid crystal panel is combined by the optical system 88, which is ON, OFF, or grayscale, and the amount of transmitted light is limited, by the shutter function of the liquid crystal panel, and is further displayed on the display screen 89 in an enlarged manner.

In this embodiment, since the light source has a single wavelength, the optical conditions for passing through the liquid crystal panel can be adjusted in each liquid crystal panel, so that the scattered light after passing through the panel is small, and the enlarged projection display is performed. There is no blur on the screen, and a sharp display can be performed. As the laser light used in this example, in addition to the gas laser described above, a laser light using a metal vapor of cadmium or zinc, a solid-state laser using a ruby or the like, or a laser light of another type has a peak wavelength in the visible light region. Can be used. Further, it is also possible to use a device that can emit light in the visible light region by passing through a special optical system even at a wavelength other than the normal emission wavelength, such as the second harmonic of a YAG laser.

Normally, three laser lights having emission wavelengths close to red, blue and green wavelengths are used, but four or more laser lights having different wavelengths are used to combine colors to obtain a color. It is also possible to display.

[0054]

As described above, the present invention is capable of displaying in a new mode which has never been present in the conventional liquid crystal electro-optical device, and by using the present invention, the alignment control of liquid crystal can be greatly improved. A liquid crystal electro-optical device that is easy and has a very fast response speed can be obtained. Further, the present invention can easily obtain a large screen display. Therefore, the present invention can be expected to be applied to many fields such as a large-screen liquid crystal display.

[Brief description of drawings]

FIG. 1 shows a basic structure of a TFT that can be used in the present invention.

FIG. 2 shows a circuit diagram of an embodiment.

FIG. 3 shows how active elements are arranged in an example.

4A to 4D are cross-sectional views showing a manufacturing process of a TFT in an example.

FIG. 5 shows a basic configuration of a color projector according to an embodiment.

[Explanation of symbols]

 15, 66 Gate electrode 28 Channel length 25, 51 Substrate 81, 82, 83 Laser light 84, 88 Optical system 85, 86, 87 Liquid crystal panel 89 Display screen

Claims (6)

[Claims] 1. A liquid crystal electro-optical device in which a nematic liquid crystal having a positive dielectric anisotropy is interposed between a pair of substrates, wherein one of the pair of substrates has a surface which is in contact with the liquid crystal. The material has a rubbing-treated liquid crystal alignment layer,
In addition, one of the pair of substrates has a TFT whose channel length is longer than the length of the gate electrode in the channel direction.
A liquid crystal electro-optical device in which a (thin film transistor) is provided as a liquid crystal switching element. 2. The liquid crystal electro-optical device according to claim 1, wherein the channel portion is activated. 3. A liquid crystal electro-optical device in which a nematic liquid crystal having a positive dielectric constant anisotropy is interposed between a pair of substrates, wherein a surface of the pair of substrates in contact with the liquid crystal is made of an organic material. A liquid crystal switching element having an alignment layer, one of the liquid crystal alignment layers being subjected to rubbing treatment, and one of the pair of substrates being a liquid crystal TFT having a channel length longer than the length of the gate electrode in the channel direction. A liquid crystal electro-optical device characterized by being provided as. 4. The liquid crystal electro-optical device according to claim 3, wherein the channel portion is activated. 5. A liquid crystal electro-optical device in which a nematic liquid crystal having a positive dielectric constant anisotropy is interposed between a pair of substrates, wherein a surface of the pair of substrates in contact with the liquid crystal is a liquid crystal alignment layer made of an organic material. Having a liquid crystal alignment layer formed on one substrate and a liquid crystal alignment layer formed on the other substrate are rubbed in parallel with each other, and one of the pair of substrates, A liquid crystal electro-optical device characterized in that a TFT having a channel length longer than a length of a gate electrode in a channel direction is provided as a liquid crystal switching element. 6. The liquid crystal electro-optical device according to claim 5, wherein the channel portion is activated.