JPH07333601A - Color liquid crystal display element - Google Patents

Abstract

(57) [Summary] [Object] To provide a birefringence control type color liquid crystal display device capable of displaying a color with high purity. A birefringence control type color liquid crystal display device includes a liquid crystal layer 20 twisted between a pair of substrates 13 and 14.
And a pair of polarizing plates 23, 24 arranged with the liquid crystal cell 12 sandwiched therebetween. Polarizing plate 2
Between 3 and 24, complex refraction elements 21 and 22 whose refractive index is represented by a complex number are arranged. The coefficient k of the imaginary number term of the refractive index of the complex refraction element has a characteristic of becoming smaller as the wavelength becomes longer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color liquid crystal display device which displays a color image by controlling birefringence by changing an applied voltage, and more particularly, a complex refraction device can be used to display three primary colors of high purity. The present invention relates to a color liquid crystal display device.

[0002]

2. Description of the Related Art Conventionally, an electric field is applied to a liquid crystal to deform the alignment of liquid crystal molecules, and a change in birefringence caused at that time is used to display an arbitrary color in a pixel unit to display a color image. A birefringence control type color liquid crystal display device is known.

[0003]

However, the conventional birefringence control type color liquid crystal display device has a problem that the color purity of the display color is low and a beautiful color image cannot be displayed. In particular, it is difficult to separate red light having a long wavelength from green or blue light having a short wavelength, color mixing occurs, and only red or a color close to red having low color purity can be displayed. More specifically, the transmitted light intensity of light of each color changes cyclically with respect to the change of the applied electric field, but the cycle of intensity change of red light having a long wavelength is longer than that of green or blue. . Therefore, in the voltage range where the transmittance of red light is high, peaks also occur in the light intensity of blue and green, and it is difficult to separate red light from blue and green light.

Further, the conventional birefringence control type color liquid crystal display device has a drawback that the viewing angle is narrow and the display color is easily changed depending on the viewing direction. Furthermore, in the conventional birefringence control type color liquid crystal display element, the birefringence is changed by the change in the retardation of the liquid crystal layer due to the temperature change,
There is a problem that the display color changes.

As a color liquid crystal display element, there is also known an element which displays a color image by arranging a red, blue or green filter in each pixel and controlling the brightness of each pixel. However, this type of color liquid crystal display element requires a large number of pixels in order to represent one dot substantially with three pixels, and the elements are densified because a filter is arranged in the large number of pixels. Difficult to manufacture. Further, since the light transmittance of the color filter is low, the reflection type that does not use a dedicated light source such as a backlight has a problem that the display becomes dark.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a birefringence control type color liquid crystal display device which has a high color purity and enables bright color display even with a reflection type. Another object of the present invention is to provide a birefringence control type color liquid crystal display element having a wide viewing angle and a small change in display color due to temperature.

[0007]

In order to achieve the above object, a color liquid crystal display element according to a first aspect of the present invention comprises a first and a second substrate which are arranged to face each other, and the first substrate.
A first and a second formed on opposite surfaces of the first and second substrates, respectively.
Electrode, a first alignment film formed on the first electrode and the first substrate, and subjected to an alignment treatment in a first alignment direction, the second electrode and the second substrate. The molecule is sealed between the first alignment film and the second alignment film formed on the first alignment film, which is subjected to the alignment treatment in the second alignment direction. The molecules are twisted and aligned according to the alignment treatment of the alignment film, the alignment state of the molecules changes according to the voltage applied between the first and second electrodes, and the polarization of light that passes through the alignment state of the molecules changes. A liquid crystal for changing a state, a first polarizing plate arranged outside the first substrate, and a second polarizing plate.
A second polarizing plate disposed on the outer side of the substrate, and disposed between the first polarizing plate and the second polarizing plate, having birefringence and having a refractive index n and a light absorption coefficient k. In this case, an optical element having a complex refractive index N represented by a complex number in Equation 12 and having a characteristic that the light absorption coefficient k becomes smaller as the wavelength becomes longer,

## EQU12 ## It is characterized in that N = n-ik (i is an imaginary number).

Further, the color liquid crystal display element according to the second aspect of the present invention is formed on the first and second substrates which are arranged to face each other, and on the facing surfaces of the first and second substrates, respectively. A first and a second electrode, a liquid crystal that is sealed between the first and the second substrate, and has an alignment state that changes according to a voltage applied between the first and the second electrodes, A first polarizing plate arranged outside the first substrate, a second polarizing plate arranged outside the second substrate, the first polarizing plate and the second polarizing plate.
Is provided between the polarizing plates and has a birefringence and a refractive index of n and a light absorption coefficient of k, a complex refractive index N represented by a complex number in Expression 13 is provided, and the light absorption coefficient k is a wavelength. An optical element having a characteristic that becomes smaller as the length becomes longer,

## EQU13 ## It is characterized in that N = n-ik (i is an imaginary number).

[0009]

The color liquid crystal display element of the present invention includes an optical element having a complex refractive index (hereinafter referred to as a complex refractive element), and the complex refractive index N (= n-ik) of the imaginary coefficient k (light The absorption coefficient has a negative slope with respect to the wavelength (it becomes smaller as the wavelength becomes longer). Therefore, the longer the wavelength of light, the easier it is for light to pass through this liquid crystal display element. Therefore, in the range of the applied electric field in which the light in the red wavelength region maintains a constant intensity, the intensity of the light in the green or blue wavelength region becomes weaker than in the past. Therefore, mixing of green or blue light with red light can be reduced, and red with high color purity can be displayed.

Further, by using a complex refraction element in which the refractive index in the thickness direction and the refractive index in the plane direction orthogonal to the thickness direction are different from each other, when light is transmitted vertically through the liquid crystal layer and when it is transmitted obliquely. The phase difference is compensated, and the viewing angle is widened. Further, the display color is obtained not only by the birefringence effect of the liquid crystal layer, but also by the birefringence effect of the complex refraction element, and even if the retardation of the liquid crystal layer changes due to temperature change, the effect is relative. Small. Therefore, it is possible to reduce the variation in display color due to the temperature change.

[0011]

Embodiments of a color liquid crystal display element using a complex refraction element will be described below with reference to the drawings. (First Embodiment) First, the structure of a simple matrix type birefringence control type reflection type color liquid crystal display device according to the first embodiment of the present invention will be described with reference to FIGS.

FIG. 1 shows a color liquid crystal display device 11 of this embodiment.
2 is a cross-sectional view showing the configuration of FIG. 2 and FIG. 2 is a plan view showing the arrangement of each optical axis of the color liquid crystal display element 11. In FIG. 1, a liquid crystal cell 12 includes a first substrate (hereinafter, upper glass substrate) 13
And a second substrate (hereinafter, lower glass substrate) 14 are opposed to each other with a minute gap for enclosing the liquid crystal layer, for example, 6.8 μm. On the opposing surfaces of the glass substrates 13 and 14, a plurality of scanning electrodes 15 and a plurality of signal electrodes 16 made of a transparent conductive material such as ITO (an oxide of indium and tin).
And are arranged in a crossed state.

The alignment films 17 and 18 are provided on the surfaces of the scanning electrodes 15 and the signal electrodes 16 provided on the inner surfaces of the glass substrates 13 and 14 of the liquid crystal cell 12, and regulate the alignment direction of liquid crystal molecules. Is. The alignment films 17 and 18 have been subjected to an alignment treatment such as rubbing, and the major axis directions of the liquid crystal molecules adjacent to each other are aligned with the alignment treatment direction. Seal material 19
Is disposed in the peripheral portion between the upper and lower glass substrates 13 and 14, holds the glass substrates 13 and 14 at a predetermined interval, and seals the liquid crystal in that region.

The liquid crystal layer 20 is composed of nematic liquid crystal or the like to which chiral liquid crystal is added, and the liquid crystal molecules are twisted at 250 ° ± 20 ° (preferably ± 10 °) according to the alignment regulating force of the alignment films 17 and 18. It is in a twisted orientation at the corners. The optical anisotropy Δn of the liquid crystal is set to about 0.2, and the layer thickness d of the liquid crystal layer 20 is set to about 6.8 μm. That is,
Δn · d = 1360 nm ± 100 nm is set.

The complex refractive element 21 has a refractive index defined by a complex number, and the direction in which the refractive index is maximum on the plane orthogonal to the thickness direction (in-plane stretching direction) is the x direction.
When the direction orthogonal to the x direction on the plane is the y direction and the thickness direction is the z direction, the complex refractive index N _x , N _y in each direction,
N _z is represented by Equations 14 to 16.

N = n _x −ik _x

(15) N _y = n _y −ik _y

Equation 16] N _z = n _z -ik _{z where, n x, n y, n} z represents the refractive index, i is represents an imaginary _{number, k x, k y, k} z denotes the light absorption coefficient.

The refractive indices n _x , n _y and n _z satisfy the relationship of n _x > n _z > n _y . Further, the refractive index anisotropy Δn = n _x -n _y
The product of thickness and thickness Δn · t is 1600nm ± 30nm, Rz
Coefficient is 0.3 to 0.7, preferably 0.45 ± 0.1
belongs to. Note that the Rz coefficient is defined as in Expression 17.

R _z = (n _x −n _z ) / (n _x −n _y ).

The light absorption coefficients k _x , k _y and k _z are functions of the wavelength λ and can be expressed as k _x (λ), k _y (λ) and k _z (λ). Here, the light absorption coefficient k _x (λ), k
_As shown in FIG. 3, _y (λ) and k _z (λ) have a negative slope, that is, a value that decreases as the wavelength λ becomes longer, that is, a negative wavelength dependence.

Explaining the difference between the ordinary refractive index and the complex refractive index, when the light is considered as a wave, the intensity amplitude of the incident light of an optical element (for example, a retardation plate) having the ordinary refractive index is I _i . Then, the amplitude I _{o of the} emitted light is expressed by Equation 18,
Assuming that the intensity amplitude of the incident light of the complex refraction element having the complex refractive index is I _i , the amplitude I _{o of the} emission light thereof is represented by Formula 19.

[Equation 18]

[Formula 19] Here, t represents the thickness of the retardation plate or the complex refraction element,
Exp (−2πkt / λ) in Expression 19 represents an absorption term.

Further, the Jones matrix used for obtaining the polarization state of the light passing through these ordinary optical elements or complex refracting elements is given by Equation 2 for ordinary optical elements.
0, and the complex refraction element is expressed by Equation 21.

[Equation 20]

[0020]

[Equation 21]

Here, Δn is the difference between n _x and n _y (n _x −n _y ).
In it, .DELTA.k is the difference k _x and _{k y (k x -k y)} . In the present embodiment, Δk is almost 0, that is, k _x and k _y have almost the same value (more accurately, almost the same function), and k _z also has the substantially same value.

The other complex refraction element 22 also has a complex refractive index defined by a complex number, and the light absorption coefficient has a negative slope,
Δn · d is 1550 nm ± 30 nm, Rz coefficient is 0.3
˜0.7, preferably 0.45 ± 0.1.

The upper polarizing plate 23 and the lower polarizing plate 24 block (absorb) the polarization component in the absorption axis direction of the incident light and transmit the polarization component orthogonal thereto. Reflector 25
Is provided on the lower surface of the lower polarizing plate 24, and reflects the light incident from the upper polarizing plate 23 and transmitted through the liquid crystal cell 12 and the lower polarizing plate 24 to the liquid crystal cell 12 side.

2A to 2E show an example of a combination of the alignment treatment direction of the liquid crystal cell 12, the optical axes (in-plane stretching axes) of the complex refraction elements 21 and 22 and the transmission axes of the polarizing plates 23 and 24. FIG. 3 is a diagram schematically showing a plan view of each component.
Note that the alternate long and short dash line S in FIG. 2D is a reference line along the left-right direction of the display surface, and is for facilitating understanding.

As shown in FIG. 2D, the direction 18a of the alignment treatment applied to the lower alignment film 18 of the liquid crystal cell 12 is inclined 35 ° ± 10 ° with respect to the reference line S. 18
Liquid crystal molecules in the vicinity are arranged along the alignment processing direction 18a. The direction 17a of the alignment treatment applied to the upper alignment film 17 of the liquid crystal cell 12 is set to a direction intersecting at 70 ° ± 10 ° with the alignment treatment direction 18a of the lower alignment film 18 as a reference. Liquid crystal molecules in the vicinity of 17 are arranged along the alignment treatment direction 17a. As a result, the liquid crystal molecules are rotated in the clockwise direction from the lower glass substrate 14 side toward the upper glass substrate 13 side by 250 ° ± 20 ° (preferably ± 10 °).
A twisted orientation state is obtained.

As shown in FIG. 2A, the transmission axis 23a of the upper polarizing plate 23 is 50 ° ± 10 ° with respect to the alignment processing direction 18a of the lower alignment film 18 (85 ° ± with respect to the reference line S). 10
°) are set to intersect. As shown in FIG. 2B, the stretching axis 21 a of the complex refraction element 21 (the axis having the largest refractive index on the plane) 21 a is 25 ° ± 10 ° with respect to the alignment treatment direction 18 a of the lower alignment film 18. It is set to intersect the reference line S at 10 ° ± 10 °.
As shown in FIG. 2C, the stretching axis 2 of the complex refraction element 22 is
2a is 1 with respect to the alignment treatment direction 18a of the lower alignment film 18.
It is set to intersect at 5 ° ± 10 ° (50 ° ± 10 ° with respect to the reference line S). As shown in FIG. 2E, the transmission axis 24a of the lower polarizing plate 24 is 45 ° ± 10 ° with respect to the alignment treatment direction 18a of the lower alignment film 18 (10 ° ± 10 ° with respect to the reference line S). It is set to intersect at.

Next, the coloring principle of the birefringence control type color liquid crystal display device having the above structure will be described. Light incident on the color liquid crystal display element 11 from above in FIG. 1 becomes linearly polarized light by passing through the upper polarizing plate 23, and is further transmitted through the complex refracting elements 21 and 22. The elliptically polarized light having a different polarization state for each wavelength undergoes a birefringent action according to the optical arrangement conditions such as the positions of the stretching axes 21a and 22a and the retardation value. In the process of passing through the liquid crystal cell 12, the elliptically polarized light of each wavelength is subjected to a birefringence action according to the optical arrangement condition and the retardation value of the liquid crystal cell 12, and the polarization state thereof is further changed. When elliptically polarized light of each wavelength having different polarization states, which has been subjected to the birefringence effect by the complex refraction elements 21 and 22 and the liquid crystal cell 12, enters the lower polarization plate 24, the transmission axis 24 of the lower polarization plate 24.
Light having a polarization component matching a is transmitted through the lower polarizing plate 24.

The light transmitted through the lower polarizing plate 24 is reflected by the reflecting plate 25.
And is emitted to the upper surface side of the color liquid crystal display element 11 through a path opposite to the above-described optical path, and the color of the emitted light becomes a display color. The retardation of the complex refraction elements 21 and 22 is
It is a substantially constant value determined by the product Δn · t of the refractive index anisotropy Δn of the complex refraction elements 21 and 22 and the thickness t, and the retardation of the liquid crystal cell 12 is determined by the alignment state of the liquid crystal molecules. Therefore, similar to a normal birefringence control type color liquid crystal display element, the voltage applied between the opposing electrodes 15 and 16 is changed to change the alignment state of the liquid crystal molecules and change the polarization action of the liquid crystal cell 12. It is possible to change the hue and brightness of the display color.

Here, tentatively, the imaginary term of the complex refractive index of the complex refraction elements 21 and 22, that is, the light absorption coefficients k _x , k _y and k _z.
Is a constant value regardless of wavelength, electrodes 15 and 1
The output intensity of red (610 nm), green (550 nm), and blue (450 nm) light with respect to the voltage V applied during 6 is shown in FIG.
It changes like (A). That is, red light with a long wavelength
The cycle of the intensity change is long with respect to the change of the voltage V. On the other hand, green or blue light having a short wavelength changes its intensity with a shorter cycle with respect to the change of the voltage V. Therefore, the green or blue light has a certain intensity even in the voltage range in which the red light has a certain intensity or more. That is, FIG.
In the characteristic shown in (A), a region in which the intensity of green or blue light is relatively strong is located in a region in which the intensity of red emitted light is strong.
For this reason, green and / or blue light is emitted together with red light, and it is difficult to extract red with high color purity. Since the voltage region where the intensity of the emitted light of red is relatively weak is wide, it is possible to take out the emitted light of green or blue without color mixing in this voltage region.

On the other hand, as shown in FIG. 3, when the light absorption coefficient k (λ) has a negative wavelength dependency (its value decreases as the wavelength becomes longer), the longer the wavelength of light is, the more the ratio is absorbed. Get smaller. Therefore, as shown in FIG.
The intensity of green and blue light becomes relatively weaker than that of red light. For this reason, even if red light and green and / or blue light are emitted at the same time, and the color mixture occurs, the effect of the green and / or blue light is small, so that the effect is small and the red with high color purity is obtained. Can be displayed. On the other hand, the display of green and blue can be selected in a relatively wide voltage range in which the intensity of emitted light of red is weak, and since green and blue change in a relatively short cycle, separation of green and blue is easy. Yes, green and blue with high color purity can also be displayed.

As described above, according to the above embodiment, by controlling the voltage applied between the scanning electrode 15 and the signal electrode 16 to control the electric field (effective voltage) applied to the liquid crystal layer 20, By controlling the birefringence of the liquid crystal layer 20, it is possible to display a desired color, particularly three primary colors having high color purity. Further, according to the above configuration, since the complex refraction elements 21 and 22 having a phase difference also in the thickness direction are used, there is a difference between when light is transmitted vertically through the liquid crystal layer 20 and when it is transmitted obliquely. The phase difference is compensated by transmitting through the complex refraction elements 21 and 22, and the viewing angle is widened.

The display color is obtained not only by the birefringence effect of the liquid crystal layer 20 but also by the respective birefringence effects of the complex refraction elements 21 and 22. Since two complex refraction elements 21 and 22 in which the temperature dependence of the birefringence action is smaller than the temperature dependence of the birefringence action of the liquid crystal layer 20 are used, even if the retardation of the liquid crystal layer 20 changes due to the temperature change. , Its impact is relatively small. Therefore, it is possible to reduce the variation in display color due to the temperature change. In addition, as the applied voltage (effective voltage) to the liquid crystal layer 20 rises, the display color becomes white →
The color changes from red to blue to green, and the three primary colors and white can be displayed, making it possible to display a practically sufficient color image.

Concrete Example As a concrete example of the first embodiment, the alignment treatment directions 17a and 18a of the alignment films 17 and 18, the stretching axes 21a and 22a of the complex refraction elements 21 and 22, and the transmission axis 23 of the polarizing plates 23 and 24.
The arrangement angles of a and 24a are set to the central angles of the respective angles shown in FIGS. 2A to 2E, and the thickness d of the liquid crystal layer 20 is set to 6.8 μm.
m, Δn · d of 1390 nm, complex refraction element 2
The optical absorption coefficient of 1, 22 at a wavelength of 610 nm is 0.0
5, a color liquid crystal display element having a light absorption coefficient of 0.09 at a wavelength of 550 nm and a light absorption coefficient of 0.12 at a wavelength of 450 nm was prepared, and a signal supplied to the scanning electrode 15 and the signal electrode 16 was controlled to make static. Driven.

In this case, as shown in FIG. 5, when the static voltage, that is, the effective value of the applied voltage is less than 2.04 V, the display color of this color liquid crystal display element is white, and the effective value of the applied voltage is 2. At 12V to 2.18V, the display color is red, and the effective value of the applied voltage is 2.19V to 2.21.
At V, the display color is blue, and the effective value of the applied voltage is 2.
At 27V and above, the display color was green. Each display color had a high color purity as shown in the CIE chromaticity diagram of FIG.

Comparative Example As a comparative example, the wavelengths of the complex refraction elements 21 and 610n are 610n.
Signals to be supplied to the scanning electrodes 15 and the signal electrodes 16 were prepared by making a color liquid crystal display element having a light absorption coefficient at m, 550 nm, and 450 nm of about 0.10 and other configurations substantially the same as those of the first embodiment. Was controlled and driven statically. In this case, when the static voltage, that is, the effective value of the applied voltage is less than 2.04 V, the display color of this color liquid crystal display element is white, and the effective value of the applied voltage is 2.15 V to
At 2.17V, the display color is yellow (reddish yellow)
When the effective value of the applied voltage is 2.18V to 2.22V, the display color is blue, and the effective value of the applied voltage is 2.26.
Above V, the display color was green and the color purity of red was low.

As is clear from this specific example and comparative example, according to this example, the three primary colors having high color purity, particularly,
Red with high color purity can be displayed. Further, in the color liquid crystal display element of this specific example, the change in display color due to the temperature change was small, and the viewing angle was wide.

(Second Embodiment) In the above embodiment, 2
Although the complex refracting elements 21 and 22 are arranged between the upper glass substrate 13 and the upper polarizing plate 23, the position of the complex refracting elements is arbitrary. For example, as shown in FIG. 7, one complex refraction element 21 is disposed between the upper glass substrate 13 and the upper polarizing plate 23, and the other complex refraction element 22 is disposed between the lower glass substrate 14 and the lower polarizing plate 24. It may be arranged. Alignment film 1 when complex refraction elements 21 and 22 are arranged in this way
7, 18 alignment treatment directions 17a, 18a, stretching axes 21a, 22a of the complex refraction elements 21, 22 and the polarizing plate 23,
The arrangement of the transmission axes 23a and 24a of 24 is shown in FIG.
It shows in (E).

As shown in FIG. 8C, the direction 18a of the alignment treatment applied to the lower alignment film 18 is 3 with respect to the reference line S.
The direction 17a of the alignment treatment applied to the upper alignment film 17 is inclined by 5 ° ± 10 °, and the alignment treatment direction 18a of the alignment film 18 is
Is set in a direction intersecting at 70 ° ± 10 °, and the liquid crystal molecules are 250 ° ± 20 in a clockwise direction from the lower glass substrate 14 side toward the upper glass substrate 13 side.
The orientation state is twisted by ° (desirably ± 10 °).

As shown in FIG. 8A, the transmission axis 23a of the upper polarizing plate 23 is 80 ° ± 10 ° with respect to the alignment treatment direction 18a of the lower alignment film 18 (45 ° ± with respect to the reference line S). 10
°) are set to intersect. As shown in FIG. 8B, the stretching axis 21a of the complex refraction element 21 (direction in which the refractive index is maximized on the plane) 21a is 35 ° ± 10 ° with respect to the alignment treatment direction 18a of the lower alignment film 18. It is set to intersect the reference line S at 0 ° ± 10 °. Figure 8
As shown in (D), the stretching axis 22a of the complex refraction element 22 (the direction in which the refractive index is maximized on the plane) 22a has a lower alignment film 18a.
It is set to intersect with the orientation processing direction 18a of 10 ° ± 10 ° (45 ° ± 10 ° with respect to the reference line S). As shown in FIG. 8E, the transmission axis 24a of the lower polarizing plate 24 is 45 ° ± 10 ° with respect to the alignment treatment direction 18a of the lower alignment film 18 (10 ° ± 10 ° with respect to the reference line S).
It is set to intersect at.

Δn · t of the complex refraction element 21 is 1600n
m ± 30 nm, Rz coefficient is 0.3 to 0.7 (preferably 0.45 ± 0.1), and Δn · d of the liquid crystal layer 20 is 1.
350 nm ± 100 nm, and Δ of the complex refraction element 22 is
n · t is 1600 nm ± 30 nm, Rz coefficient is 0.3 to
0.7 (preferably 0.45 ± 0.1).

With such a structure, a color image can be displayed by controlling the effective applied voltage of the liquid crystal layer 20 and the display color, and in particular, the three primary colors having high color purity can be displayed. Since the complex refraction elements 21 and 22 having a refractive index also in the thickness direction are used, the phase difference between when light vertically passes through the liquid crystal layer 20 and when it obliquely passes is complex refraction. It is compensated by transmitting through the elements 21 and 22, and the viewing angle is improved.

As described above, according to the birefringence control type color liquid crystal display element of the present invention, it is possible to display three primary colors having high purity. In addition, the viewing angle is increased,
Color shift due to temperature change can be reduced.

In the above embodiment, the invention of the present application has been described by taking a twisted nematic color liquid crystal display element of a simple matrix type having a large twist angle as an example. However, the present invention is, for example, an active element using a TFT (thin film transistor) or the like as an active element. It may be applied to a matrix type color liquid crystal display element.

Although the complex refracting elements 21 and 22 are arranged between the polarizing plates 23 and 25 in the first and second embodiments, for example, one or three or more complex refracting elements are polarized. It may be arranged between the plates 23 and 25. In the first and second embodiments, the complex refraction element 21,
As the element 22, a material having different refractive indexes in three directions orthogonal to each other was used, but the material is not limited to this. Further, although the light absorption coefficients k _x , k _y , and k _z of the imaginary term of the complex refractive index have been described as substantially the same value, these values may be different. In addition, FIG. 3 shows an example in which the light absorption coefficients k _x , k _y , and k _z of the imaginary term of the complex refractive index become substantially uniform as the wavelength λ becomes longer. If the absorption coefficient is smaller than the light absorption coefficients in the green and blue wavelength regions, the mode and degree of change are arbitrary.

In the above embodiment, the reflection plate 25 is used as the lower polarization plate 2
Although the reflective type color liquid crystal display element provided on the fourth side has been described, the same effect can be obtained even if the reflection plate 25 is arranged on the upper polarizing plate 23 side. Further, in the above embodiment, the reflective type color liquid crystal display device provided with the reflection plate 25 has been described, but the present invention is also applicable to a transmissive type color liquid crystal display device.

[0046]

As described above, according to the present invention, the three primary colors with high color purity can be displayed, the viewing angle is large, and
In addition, it is possible to provide a color liquid crystal display element in which color shift due to temperature change is reduced.

[Brief description of drawings]

FIG. 1 is a sectional view of a birefringence control type color liquid crystal display element according to a first embodiment of the present invention.

FIG. 2 is a plan view showing a positional relationship between an alignment direction of liquid crystal molecules, a transmission axis direction of a polarizing plate, and a plane stretching axis of a complex refraction element in the color liquid crystal display element according to the first example.

FIG. 3 is a diagram showing wavelength dependence of a light absorption coefficient k that constitutes an imaginary part of a complex refractive index of a complex refraction element.

FIG. 4 is a diagram showing a relationship between a voltage applied between electrodes facing each other and intensities of emitted lights of red, green, and blue. FIG. 4A is a light absorption coefficient of an imaginary term of a complex refractive index of a complex refractive element. Is constant regardless of wavelength, (B) is a case where the optical absorption coefficient of the imaginary term of the complex refractive index of the complex refraction element is made smaller as the wavelength becomes longer (in the case of the first embodiment). For example:

FIG. 5 is a diagram showing a relationship between an applied voltage and a display color of the color liquid crystal display element according to the first example.

FIG. 6 is a chromaticity diagram of a color liquid crystal display element according to a specific example of the first example.

FIG. 7 is a sectional view of a color liquid crystal display element according to a second embodiment of the present invention.

FIG. 8 is a plan view showing a relationship among an alignment direction of liquid crystal molecules, a transmission axis direction of a polarizing plate, and a stretching axis position of a complex refraction element in a color liquid crystal display element according to a second example.

[Explanation of symbols]

11 ... Color liquid crystal display element, 12 ... Liquid crystal cell, 13 ...
・ Upper glass substrate, 14 ... Lower glass substrate, 15 ... Scan electrode, 16 ... Signal electrode, 17 ... Alignment film, 18 ... Alignment film, 19 ... Sealing material, 20 ... ..Liquid crystal layer, 21 ... Complex refraction element, 22 ... Complex refraction element, 23 ... Upper polarizing plate, 24
... Lower polarizing plate, 25 ... Reflector

Claims (4)

[Claims] 1. A first substrate and a second substrate which are arranged to face each other, a first electrode and a second electrode which are respectively formed on opposing faces of the first substrate and the second substrate, and the first electrode. A first alignment film formed on the first substrate and subjected to an alignment treatment in a first alignment direction; a second alignment film formed on the second electrode and the second substrate; Between the first and second alignment films and the second alignment film that has been oriented in the direction, and its molecules are twisted according to the alignment treatment of the first and second alignment films. A liquid crystal that is oriented and changes the orientation state of molecules according to the voltage applied between the first and second electrodes, and changes the polarization state of transmitted light according to the orientation state of the molecules; A first polarizing plate arranged outside the first substrate; a second polarizing plate arranged outside the second substrate; Disposed between the plate and the second polarizing plate,
A property that the birefringence is provided and the refractive index is n and the light absorption coefficient is k, and a complex refractive index N represented by a complex number in Expression 1 is provided, and the light absorption coefficient k becomes smaller as the wavelength becomes longer. A color liquid crystal display element comprising: an optical element having: and N = n-ik (i is an imaginary number). 2. A first and a second substrate which are arranged to face each other, a first and a second electrode which are respectively formed on opposing faces of the first and the second substrate, and the first and the second electrode. A liquid crystal that is sealed between two substrates and has an alignment state that changes according to a voltage applied between the first and second electrodes; and a first polarizing plate that is disposed outside the first substrate. A second polarizing plate arranged outside the second substrate, and arranged between the first polarizing plate and the second polarizing plate,
A property that the birefringence is provided and the refractive index is n and the light absorption coefficient is k, and a complex refractive index N represented by a complex number in Equation 2 is provided, and the light absorption coefficient k becomes smaller as the wavelength becomes longer. A color liquid crystal display device comprising: an optical element having: and N = n-ik (i is an imaginary number). 3. A first and a second substrate which are arranged to face each other, a first and a second electrode which are respectively formed on opposing faces of the first and the second substrate, and the first electrode. A first alignment film formed on the first substrate and subjected to an alignment treatment in a first alignment direction; a second alignment film formed on the second electrode and the second substrate; Between the first and second alignment films and the second alignment film that has been oriented in the direction, and its molecules are twisted according to the alignment treatment of the first and second alignment films. A liquid crystal that is oriented and changes the orientation state of molecules according to the voltage applied between the first and second electrodes, and changes the polarization state of transmitted light according to the orientation state of the molecules; A first polarizing plate arranged outside the first substrate; a second polarizing plate arranged outside the second substrate; Disposed between the plate and the second polarizing plate,
When it has birefringence and its refractive index is n and its light absorption coefficient is k, it has a complex refractive index N represented by a complex number in Expression 3, and the light absorption coefficient k for red light has a wavelength of green and A color liquid crystal display element comprising an optical element having a characteristic smaller than a light absorption coefficient k for blue light, and N = n-ik (i is an imaginary number). 4. A first substrate and a second substrate which are arranged to face each other, a first electrode and a second electrode which are respectively formed on opposing faces of the first substrate and the second substrate, and the first electrode. A first alignment film formed on the first substrate and subjected to an alignment treatment in a first alignment direction; a second alignment film formed on the second electrode and the second substrate; Between the first and second alignment films and the second alignment film that has been subjected to the alignment treatment in the direction, and the molecules thereof are 230 ° to 230 ° according to the alignment treatment of the first and second alignment films. Two
A liquid crystal that is twisted at 70 ° and oriented, and has a product Δn · d of optical anisotropy Δn and thickness d of 1250 nm to 1450 nm, the liquid crystal being disposed outside the first substrate and having an optical axis A first polarizing plate arranged to intersect with the second alignment treatment direction at 40 ° to 60 °, and an optical axis arranged on the outer side of the second substrate with respect to the second alignment treatment direction. A second polarizing plate arranged to intersect at 35 ° to 55 °, and arranged between the first substrate and the first polarizing plate and having birefringence and having a refractive index of n and light absorption. When the coefficient is k, the complex refractive index N represented by a complex number in Equation 4 is provided, and the refractive index n in a plane orthogonal to the thickness direction.
_Represents the complex index of refraction N _x1 in the largest direction, and the complex index of refraction N _y1 in the direction orthogonal to the maximum index direction in the plane is represented by Formula 6, and the complex index of refraction N _{z1 in the} thickness direction. Is expressed by Equation 7, the relationship of n _x1 > n _z1 > n _y1 is satisfied, and the light absorption coefficients k _x1 , k _y1 , and k _z1 have characteristics that become smaller as the wavelength becomes longer. A first optical element disposed so as to intersect the second alignment treatment direction at 15 ° to 35 °, and N = n-ik (i is an imaginary number) N _x1 = n _x1 −ik _x1 (i is an imaginary number) N _y1 = n _y1 −ik _y1 (i is an imaginary number) N _z1 = n _z1 −ik _z1 (i is an imaginary number) The first substrate and the above Disposed between the first optical elements,
Equipped with a complex refractive index N represented by a complex number in Expression 8 and having birefringence, the complex refractive index N _x2 in the direction in which the refractive index n is the largest in the plane orthogonal to the thickness direction is represented by Expression 9, and the maximum When the complex refractive index N _y2 in the direction orthogonal to the refractive index direction is expressed by Expression 10, and the complex refractive index N _z2 in the thickness direction is expressed by Expression 11, the relationship of n _x2 > n _z2 > n _y2 And the light absorption coefficients k _x2 , k _y2 , and k _z2 decrease as the wavelength increases, and the maximum refractive index direction is intersected with the second alignment treatment direction by 5 ° to 25 °. And a second optical element arranged as follows, N = n-ik (i is an imaginary number) N _x2 = n _x2 -ik _x2 (i is an imaginary number) N _y2 = n _y2 −ik _y2 (i is an imaginary number) [Formula 11] N _z2 = n _z2 −ik _z2 (i is an imaginary number) Characteristic liquid crystal display device.