JP2003255322A - Liquid crystal display element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display element wide in viewing angle and capable of displaying a color image reduced in color change due to the change of a viewing angle. <P>SOLUTION: A plurality of viewing angle compensation films 21, 22 are arranged in each of the front and the rear of a liquid crystal cell 10 constituted by providing electrodes 13, 14 that form a plurality of pixels by areas opposed to each other on the inner surfaces of a pair of front and rear substrates 11, 12 to be opposed by clamping a liquid crystal layer 16 and providing color filters 15R, 15G, 15B of three colors as red, green and blue corresponding to each of a plurality of the pixels on the inner surface of the substrate 11 and thickness dB of a liquid crystal layer of a pixel to which the color filter 15B of the color in a wavelength band of which transmissivity to the viewing angle compensation films 21, 22 is lowered due to the change of the viewing angle to the diagonal direction to the front direction corresponds among a plurality of the pixels to which each of the color filters 15R, 15G, 15B of the three colors of the liquid crystal cell 10 corresponds is set as smaller than thickness dRG of a liquid crystal layer of pixels to which the color filters 15R, 15G of colors in other wavelength bands correspond. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device that displays a color image.

[0002]

2. Description of the Related Art A liquid crystal display device for displaying a color image such as a full-color image is provided with electrodes forming a plurality of pixels on the inner surfaces of a pair of front and rear substrates facing each other with a liquid crystal layer interposed therebetween. On the inner surface of one of the substrates, a plurality of colors corresponding to the plurality of pixels,
For example, a liquid crystal cell provided with three color filters of red, green, and blue is provided.

In this liquid crystal display element, the liquid crystal layer of the liquid crystal cell is composed of a nematic liquid crystal having an initial alignment state in which liquid crystal molecules are twisted substantially at a twist angle of 90 °. A TN (twisted nematic) type in which a pair of front and rear polarizing plates are arranged on the rear side and the rear side is widely used.

In the liquid crystal display element, the value of Δnd (the product of the refractive index anisotropy Δn of the liquid crystal and the thickness d of the liquid crystal layer) of the liquid crystal cell apparently changes depending on the viewing angle of the display. The viewing angle range where the display can be observed with good contrast is narrow.

Therefore, conventionally, for example, a viewing angle compensating film made of a discotic liquid crystal film or the like in which discotic liquid crystal molecules are gradually raised and oriented from one face to the other face from a collapsed state is used to form the liquid crystal display element. It is considered to widen the viewing angle.

[0006]

However, while a liquid crystal display device provided with a viewing angle compensation film such as the discotic liquid crystal film has a wide viewing angle, it does not emit light in a specific wavelength band of the visible light band. The transmittance of the viewing angle compensation film decreases as the viewing angle is changed obliquely with respect to the front direction, and the hue of the displayed color image changes.

An object of the present invention is to provide a liquid crystal display device capable of displaying a color image having a wide viewing angle and a small change in hue due to a change in viewing angle.

[0008]

A liquid crystal display device according to the present invention is provided with electrodes forming a plurality of pixels on respective inner surfaces of a pair of front and rear substrates facing each other with a liquid crystal layer interposed therebetween. A liquid crystal cell provided with color filters of a plurality of colors respectively corresponding to the plurality of pixels on the inner surface of one substrate, and a viewing angle compensation film disposed on at least one of the front side and the rear side of the liquid crystal cell. Further, according to the change of the transmittance of each wavelength light according to the viewing angle of the viewing angle compensation film, the color filter of the plurality of colors corresponds to the liquid crystal layer thickness of each pixel is compensated for the hue change depending on the viewing angle. It is characterized by setting as follows.

This liquid crystal display device has a wide viewing angle because it has a viewing angle compensation film on at least one of the front side and the rear side of the liquid crystal cell. The liquid crystal display device is configured such that the liquid crystal layer thickness of each pixel corresponding to the color filters of the plurality of colors is changed according to the change of the transmittance for each wavelength light depending on the viewing angle of the viewing angle compensation film. Since the change is set to be compensated, it is possible to display a color image with a small change in hue due to a change in viewing angle.

As described above, the liquid crystal display element of the present invention is provided with electrodes for forming a plurality of pixels on the inner surfaces of a pair of front and rear substrates that face each other with the liquid crystal layer interposed therebetween, and the electrodes for forming a plurality of pixels are provided on the front substrate. An inner surface is provided with a viewing angle compensation film on at least one of a front side and a rear side of a liquid crystal cell provided with color filters of a plurality of colors corresponding to the plurality of pixels, respectively, and each viewing angle compensation film has a viewing angle depending on a viewing angle. By setting the liquid crystal layer thickness of each pixel corresponding to the color filters of the plurality of colors according to the change of the transmittance for each wavelength light so that the hue change depending on the viewing angle of the display is compensated, the viewing angle is wide, In addition, it is possible to display a color image with a small change in hue with a change in viewing angle.

In the liquid crystal display device of the present invention, the viewing angle compensating film is made of a discotic liquid crystal film in which discotic liquid crystal molecules are gradually risen and oriented from one face to the other face in a collapsed state. Is preferred.

In this case, the liquid crystal layer of the liquid crystal cell is composed of a nematic liquid crystal having an initial alignment state in which liquid crystal molecules are substantially twisted at a twist angle of 90 °. Of the discotic liquid crystal film, the respective discotic liquid crystal molecules have the same orientation state face to each other, and the liquid crystal molecule orientation direction of the front discotic liquid crystal film is the liquid crystal molecules in the vicinity of the front substrate of the liquid crystal cell. It is preferable to arrange the liquid crystal molecules of the discotic liquid crystal film on the rear side so as to be substantially parallel to the alignment direction and to be substantially parallel to the liquid crystal molecule orientation direction near the rear substrate of the liquid crystal cell.

In this liquid crystal display device, when the color filters of a plurality of colors provided on the inner surface of one substrate of the liquid crystal cell are three color filters of red, green and blue, the red, green, It is preferable to set the liquid crystal layer thickness of the pixel corresponding to the blue filter to be smaller than the liquid crystal layer thickness of the pixels corresponding to the red filter and the green filter among the plurality of pixels corresponding to the blue color filters.

[0014]

1 to 4 show a first embodiment of the present invention. FIG. 1 is an exploded perspective view of a liquid crystal display device,
2 is a sectional view of a part of a liquid crystal cell of the liquid crystal display device,
FIG. 3 is a view showing the arrangement state of the viewing angle compensation film, and FIG. 4 is a perspective view showing the molecular orientation state of the viewing angle compensation film.

This liquid crystal display device comprises a liquid crystal cell 10, a pair of viewing angle compensation films 21 and 22 arranged on the front side and the rear side of the liquid crystal cell 10, which are the viewing sides, and the front side viewing angle compensation film. Polarizing plates 2 arranged on the front side of 21 and on the rear side of the viewing angle compensation film 22 on the rear side, respectively.
6 and 27, and a scattering plate 28 disposed between the front side viewing angle compensation film 21 and the liquid crystal cell 10.

The liquid crystal cell 10 includes electrodes 1 which form a plurality of pixels on the inner surfaces of a pair of front and rear substrates 11 and 12 which face each other with a liquid crystal layer 16 in between.
3, 14 are provided, and on the inner surface of the front substrate 11, which is either one of the substrates, a color filter 15 of a plurality of colors corresponding to the plurality of pixels, for example, three colors of red, green, and blue.
It has a configuration in which R, 15G, and 15B are provided.

The liquid crystal cell 10 is of an active matrix type, for example, and includes a pair of front and rear substrates 11, 1.
Electrode 14 provided on the inner surface of the rear substrate 12
Is a plurality of pixel electrodes arranged in a matrix in the row and column directions, and the electrodes 1 provided on the inner surface of the front substrate 11.
Reference numeral 3 is a single film-shaped counter electrode facing the plurality of pixel electrodes.

Although not shown in the drawing, on the inner surface of the rear substrate 12, a plurality of TFTs (thin film transistors) respectively connected to the plurality of pixel electrodes 14 and a gate signal for each row TFT are provided. A plurality of gate wirings for supplying data and a plurality of data wirings for supplying data signals to the TFTs in each column are provided.

Further, the color filters 15R, 15
G and 15B are formed on the inner surface of the front substrate 11, and the counter electrode 13 provided on the inner surface of the front substrate 11 is
It is formed on the color filters 15R, 15G, and 15B.

Further, alignment films 17 and 18 are provided on the inner surfaces of the pair of front and rear substrates 11 and 12 to cover the electrodes 13 and 14, respectively.

Then, the front side substrate 11 and the rear side substrate 12
Are bonded to each other via a frame-shaped sealing material (not shown) at their peripheral portions, and the liquid crystal layer 16 is provided in a region between these substrates 11 and 12 surrounded by the sealing material.

The liquid crystal layer 16 is made of nematic liquid crystal having a positive dielectric anisotropy, and its liquid crystal molecules 16a are
Orientation direction 11 in the vicinity of the respective substrates 11 and 12
a and 12a are regulated by the alignment films 17 and 18, and are twist-aligned between the substrates 11 and 12.

Of the polarizing plates 26 and 27, the front polarizing plate 26 has its absorption axis 26a substantially parallel to the alignment direction 11a of the liquid crystal molecules 16a near the front substrate 11 of the liquid crystal cell 10. The rear polarizing plate 27 provided
The absorption axis 27a of the rear substrate 1 of the liquid crystal cell 10.
The liquid crystal molecules 16a in the vicinity of 2 are provided substantially in parallel with the alignment direction 12a of the liquid crystal molecules 16a, and the liquid crystal cell 10 and the polarizing plates 26 and 27 constitute a TN type liquid crystal display system.

In this embodiment, the liquid crystal cell 1
The liquid crystal layer 16 of 0 has an initial alignment state in which the liquid crystal molecules 16a are substantially twisted at a twist angle of 90 °, and the viewing angle direction (the highest contrast is Obtained observation direction) F
However, each of the substrates 11 and 12 of the liquid crystal cell 10 is arranged so as to be in a direction slightly inclined to the lower edge direction of the screen with respect to an axis Z (hereinafter, referred to as a vertical axis) perpendicular to the screen of the liquid crystal display element.
Direction 11a, 12 of the liquid crystal molecule 16a in the vicinity of
a is set.

That is, as shown in FIG. 1, the alignment direction 11a of the liquid crystal molecules 16a in the vicinity of the front substrate 11 of the liquid crystal cell 10 is counterclockwise when viewed from the front side with respect to the horizontal axis X of the screen of the liquid crystal display element. Is substantially 45 °, the alignment direction 12a in the vicinity of the rear substrate 12 is substantially 45 ° clockwise when viewed from the front side with respect to the horizontal axis X, and the liquid crystal molecules 16a are The twist orientation is substantially 90 degrees clockwise when viewed from the front side from the rear substrate 12 to the front substrate 11.

Therefore, the viewing angle direction F of the liquid crystal display system is
Is substantially parallel to a plane including the vertical axis Y of the screen and the vertical axis Z, and is slightly inclined to the lower edge direction of the screen with respect to the vertical axis Z. In addition, in this embodiment, the liquid crystal display system is arranged in one direction with respect to the vertical axis Z by approximately 2 °.
It is designed so that the viewing angle is in the direction tilted by approximately 5 °.

The pair of viewing angle compensating films 21 and 22 arranged on the front side and the rear side of the liquid crystal cell 10 are composed of discotic liquid crystal films 23 and 24, respectively.

The discotic liquid crystal film 23,
Reference numeral 24 denotes a discotic polymer liquid crystal having a disk-like molecular shape, and the discotic liquid crystal molecules 25 are gradually raised and oriented from one side to the other side, as shown in FIG. Each of the discotic liquid crystal molecules 25 has a central axis (axis passing through the center of the disc of the discotic molecule and orthogonal to the disc surface) 25a. , On the same plane perpendicular to the film surface and along one direction.

That is, the liquid crystal molecule alignment directions 23a and 24a of the discotic liquid crystal films 23 and 24 are
The film surface on the side where the central axis 25a of the discotic liquid crystal molecules 25 oriented so as to stand up with respect to the film surface is along the projection line O projected on the film surface and the discotic liquid crystal molecules 25 are vertically oriented. Is the direction toward the intersection P of the extension line of the central axis 25a of the discotic liquid crystal molecule 25 oriented so as to stand upright with respect to the film surface and the projection line O.

As shown in FIG. 3, the pair of discotic liquid crystal films 23 and 24 have the same orientation state of the discotic liquid crystal molecules 25,
For example, the surfaces in which the discotic liquid crystal molecules 25 are in the collapsed state are faced to each other, and
The discotic liquid crystal film 23 on the front side has its liquid crystal molecule alignment direction 23a in the front substrate 11 of the liquid crystal cell 10.
0 ° ± with respect to the alignment direction of the liquid crystal molecules 16a in the vicinity of
The discotic liquid crystal film 24 on the rear side is arranged substantially parallel to each other in the deviation angle range of 5 °, and the liquid crystal molecule alignment direction 24a is set to the liquid crystal molecule 16a alignment direction near the rear substrate 12 of the liquid crystal cell 10. Are arranged substantially parallel to each other within a deviation angle range of 0 ° ± 5 °.

That is, in this embodiment, the discotic liquid crystal film 23 on the front side is aligned with the alignment direction 23.
a is oriented substantially 45 ° counterclockwise when viewed from the front side with respect to the horizontal axis X of the screen, and the discotic liquid crystal film 24 on the rear side is oriented so that its orientation direction 24a is the horizontal axis X of the screen.
On the other hand, they are arranged in a clockwise direction substantially 45 ° when viewed from the front side.

Further, in this liquid crystal display device, as shown in FIG. 2, the liquid crystal layer thickness of the pixels corresponding to the red filter 15R and the green filter 15G of the liquid crystal cell 10 is set to be substantially equal, and the blue filter is set. 15B corresponds to the liquid crystal layer thickness d _B of the pixel by the red filter 15
The R and green filters 15G are set to be smaller than the liquid crystal layer thickness d _RG of the corresponding pixel.

In this embodiment, the total value of the product Δn′d ′ of the refractive index anisotropy Δn ′ of the liquid crystal 25 of the pair of discotic liquid crystal films 23 and 24 and the film thickness d ′ is The product Δn of the refractive index anisotropy Δn of the liquid crystal 16a of the liquid crystal cell 10 and the liquid crystal layer thickness d _RG of the pixel corresponding to the red filter 15R and the green filter 15G.
The Δn′d ′ value of each discotic liquid crystal film is set so as to be substantially the same as the value of d _RG .

In this embodiment, the refractive index anisotropy Δn of the liquid crystal of the liquid crystal cell 10 is 0.08 ± 0.01, and the liquid crystal layer thickness d _RG of the pixel corresponding to the red filter 15R and the green filter 15G is 1. .5 ± 0.2 μm, and the value of Δnd _RG of the pixel corresponding to the red filter 15R and the green filter 15G is set to about 0.12 μm. This liquid crystal display element is composed of discotic liquid crystal films 23 and 24 on the front side and the rear side of the liquid crystal cell 10, in which discotic liquid crystal molecules 25 are gradually risen and aligned from one face to the other face in a collapsed state. Since the viewing angle compensation films 21 and 22 are arranged, the viewing angle is wide.

In this embodiment, the initial alignment state of the liquid crystal molecules 16a of the liquid crystal layer 16 of the liquid crystal cell 10 is substantially 9
The twist alignment having a twist angle of 0 ° is used, and the pair of front and rear discotic liquid crystal films 23 and 24 are faced to each other with their surfaces in which the discotic liquid crystal molecules 25 have the same laid state, and the front discotic liquid crystal Liquid crystal molecule orientation direction 23a of film 23
Is substantially parallel to the liquid crystal molecule alignment direction 11a in the vicinity of the front substrate 11 of the liquid crystal cell 10, and the liquid crystal molecule alignment direction 24a of the rear discotic liquid crystal film 24 is
Are arranged substantially parallel to the liquid crystal molecule alignment direction 12a in the vicinity of the rear substrate 12 of the liquid crystal cell 10, so that the residual retardation when a voltage is applied to the liquid crystal cell 10 to make the liquid crystal molecules rise. Is compensated, and the viewing angle can be widened and the contrast can be improved.

That is, the direction along the vertical line Z is 0.
When the direction of the liquid crystal display device is in the direction of °, the upper edge direction and the right edge direction from the viewer of the screen are + directions, and the lower edge direction and the left edge direction of the screen are − directions, the liquid crystal display element without the discotic liquid crystal film is , The vertical viewing angle of the screen is + 12 ° to -31 °, the horizontal viewing angle is -37 ° to
In contrast to + 35 °, the liquid crystal display device of the above-mentioned embodiment in which the pair of discotic liquid crystal films 23 and 24 are arranged with the liquid crystal cell 10 interposed therebetween has a vertical viewing angle of + 51 ° to −61 °. Horizontal viewing angle is -60 °-
It is 61.5 °, and the viewing angle is wide in both the vertical and horizontal directions.

In this liquid crystal display element, the liquid crystal cell 10 has a blue color among a plurality of pixels corresponding to the red, green and blue color filters 15R, 15G and 15B formed on the inner surface of the front substrate 11. Since the liquid crystal layer thickness d _B of the pixel corresponding to the filter 15B is set smaller than the liquid crystal layer thickness d _RG of the corresponding pixel of the red filter 15R and the green filter 15G, the hue change due to the change of the viewing angle is reduced. A small color image can be displayed.

That is, in a liquid crystal display element in which a pair of discotic liquid crystal films are arranged with a liquid crystal cell in which a plurality of pixels having corresponding red, green, and blue color filters respectively have the same liquid crystal layer thickness, the viewing angle is in the front direction ( The transmittance of light in the blue wavelength band of the discotic liquid crystal film decreases with the change in the oblique direction with respect to the direction (along the vertical line Z), and the display is performed obliquely with respect to the front direction. When observed, the intensity of the blue emission light from the pixel corresponding to the blue filter 15B becomes weaker than the intensity of the red and green emission light from the corresponding pixel of the red filter 15R and the green filter 15G, and is displayed. The hue of the color image changes to a yellowish hue. This is because the emission intensity of the blue wavelength light is reduced due to the longer optical path. Therefore, in order to prevent the hue of the image from becoming yellowish, the light transmittance in the blue pixel of the liquid crystal cell increases or decreases when the viewing angle becomes oblique and Δnd increases, and the degree of decrease in the liquid crystal layer thickness decreases. You can set it to.
Here, when the liquid crystal layer thickness of all pixels is the same, when the viewing angle is inclined, the hue becomes yellowish,
The thickness of the liquid crystal layer is the known light transmittance for each wavelength light-Δnd.
In the characteristic curve, the characteristic curve of blue light has a relatively steep downward slope (the light transmittance decreases as Δnd increases), and the characteristic curve of other green light and red light has a gentle maximum value. It is a value in the range that is in the vicinity. Therefore, by reducing only the liquid crystal layer thickness of the blue pixel, red,
The rate of change of the light transmittance with respect to Δnd in each of the green and blue pixels becomes almost the same.

Therefore, in the liquid crystal display element of this embodiment, the color filter of the color of the wavelength band in which the intensity of the emitted light becomes weaker as the viewing angle is changed obliquely with respect to the front direction, that is, the blue filter 15B is provided. The liquid crystal layer thickness d _B of the corresponding pixel is set to be smaller than the liquid crystal layer thickness d _RG of the corresponding pixel of the red and green filters 15R and 15G which are color filters of colors in other wavelength bands, and the blue filter 15B is set. .DELTA.nd _B of the pixel corresponding to is smaller than .DELTA.nd _{RG of} the pixel corresponding to the red and green filters 15R and 15G. As a result, the decrease in the transmittance of the pixel corresponding to the blue filter 15B of the liquid crystal cell 10 due to the change of the viewing angle in an oblique direction,
The red filter and the green filters 15R and 15G are less than the decrease in the transmittance of the corresponding pixels.

Therefore, according to this liquid crystal display element,
Blue filter 15B formed by the discotic liquid crystal films 23 and 24 as the viewing angle is changed obliquely.
Compensates for the decrease in the intensity of blue light emitted from the corresponding pixel,
It is possible to display a color image with a small change in hue with a change in viewing angle.

[0041] Figure 5, the liquid crystal layer thickness difference _d B -d the pixels pixel and the red filter 15R and the green filter 15G for the blue filter 15B corresponding to the liquid crystal cell 10 corresponding
The relationship between _RG and the hue change of the display accompanying the change of the viewing angle in the left-right direction of the screen in the 20% gray display (display in the vertical axis Z direction) is shown.

Further, FIG. 6 shows that the liquid crystal layer thickness d of the pixel corresponding to the red filter 15R and the green filter 15G.
CIE1976u showing 5.09Myuemu, the hue change due to change in viewing angle of the liquid crystal layer thickness _{d B} of the pixel blue filter 15B corresponding to the horizontal direction of the screen at 20% gray displayed when a 4.54μm an _RG It is a'v 'chromaticity diagram.
In FIG. 6, W is the white point (u ′ = 0.197).
8, v ′ = 0.4683).

In FIG. 6, with a point (u ₀ , v ₀ ) representing the chromaticity in the vertical axis Z direction of the screen as the center, the viewing angle within the range of ± 60 ° with respect to the vertical axis Z in the horizontal direction of the screen. Assuming a circle that includes all points (u, v) representing chromaticity when is changed, the radius r of this circle is an index indicating the degree of hue change with respect to the change in viewing angle of each liquid crystal display element, In FIG. 5, this radius r is adopted on the vertical axis.

It should be noted that the horizontal direction ±
Among the points (u, v) showing the chromaticity when the viewing angle is changed in the range of 60 °, the point farthest from the point (u ₀ , v ₀ ) showing the chromaticity in the vertical axis Z direction is selected. Assuming that (u ₁ , v ₁ ), the radius r of hue change on the chromaticity diagram is expressed by the following equation.

[0045]

[Equation 1]

As shown in FIG. 5, the blue filter 15B
When the value of the liquid crystal layer thickness difference d _B −d _RG between the pixel corresponding to the pixel and the pixel corresponding to the red filter 15R and the green filter 15G is set to −, the liquid crystal layer thickness difference d _B −d _RG becomes 0.
When the radius r indicating the hue change on the chromaticity diagram is smaller than when μm, and conversely the value of the liquid crystal layer thickness difference d _B −d _RG is +, the hue on the chromaticity diagram is The radius r indicating the change becomes large.

Therefore, in the liquid crystal display element of this embodiment,
Is the liquid crystal layer of the pixel corresponding to the blue filter 15B.
Thickness d_BTo the red and green filters 15R, 1
The liquid crystal layer thickness d of the pixel corresponding to 5G_RGSet smaller than
Then, the liquid crystal layer thickness difference d_B-D _RGThe value of can be changed to the value of-
And by reducing the radius r of the hue change on the chromaticity diagram
can do.

Here, for example, the liquid crystal layer thickness d of the pixel corresponding to the red and green filters 15R and 15G.
5.09μm and _RG, for the liquid crystal display device of the present embodiment blue filter 15B sets the liquid crystal layer thickness _{d B} of the corresponding pixel to 4.54Myuemu, of ± 60 ° in the lateral direction with respect to the vertical axis Z of the screen The radius r indicating the hue change when the viewing angle is changed in the range is r = 0.
It is 048.

On the other hand, the liquid crystal layer thickness difference d _B -d
_{When RG} is 0 μm, for example, r = 0.079 when the liquid crystal layer thickness of each pixel is 5.09 μm. (See FIG. 5) That is, the red filter and the green filter 15
The liquid crystal layer thickness d _RG of the pixel corresponding to R and 15 G is 5.09.
μm, the liquid crystal layer thickness d of the pixel corresponding to the blue filter 15B
_The liquid crystal display element in which _B is set to 4.54 μm has a liquid crystal layer thickness of each pixel set to 5.09 μm,
The radius r of hue change on the chromaticity diagram is about 40% smaller.

Therefore, according to this liquid crystal display element,
It is possible to display a color image in which the hue change is small with the change of the viewing angle in the horizontal axis direction X (see FIG. 1) of the screen.

As described above, the liquid crystal display element of the above-described embodiment has a pair of front and rear substrates 11 facing each other with the liquid crystal layer 10 interposed therebetween.
Electrodes 13 and 14 for forming a plurality of pixels are provided on the inner surface of 12 respectively, and the plurality of pixels 1 are formed on the inner surface of one of the substrates (front substrate 11 in the embodiment).
Liquid crystal cell 10 provided with color filters 15R, 15G, and 15B of three colors of red, green, and blue respectively corresponding to three pixels.
And the viewing angle compensation films 21 and 22 arranged on the front side and the rear side of the liquid crystal cell 10, and the red, green and blue color filters 15R and 15 of the liquid crystal cell 10 are provided.
G and 15B are color filters of the color of the wavelength band in which the transmittance of the viewing angle compensation films 21 and 22 becomes lower as the viewing angle is changed obliquely with respect to the front direction among the corresponding pixels. the liquid crystal layer thickness d _B of the pixel blue filter 15B corresponding a color filter of the other wavelength bands red and green filters 15R, 15G
Since it is set to be smaller than the liquid crystal layer thickness d _RG of the corresponding pixel, it is possible to display a color image having a wide viewing angle and a small change in hue with a change in viewing angle.

In the above embodiment, the light in the blue wavelength band, which is the low wavelength band, of the liquid crystal layer thickness of each pixel corresponding to the red, green, and blue color filters 15R, 15G, and 15B of the liquid crystal cell 10. The liquid crystal layer thickness of the pixel corresponding to the blue filter 15B for transmitting the light is made smaller than the liquid crystal layer thickness of the pixels corresponding to the red filter 15R and the green filter 15G for transmitting the light of the other wavelength bands.
The liquid crystal layer thicknesses of the pixels corresponding to 5R and the green filter 15G are the same, but the viewing angle compensation film 21, which is required when the viewing angle is changed obliquely to the front direction,
The decrease in the transmittance of No. 22 increases from the high wavelength band side toward the low wavelength band side, so the liquid crystal layer thickness of the pixel corresponding to the green filter 15G that transmits light in the green wavelength band, which is the intermediate wavelength band, can be reduced. The thickness may be smaller than the liquid crystal layer thickness of the pixel corresponding to the red filter 15R that transmits light in the red wavelength band, which is a high wavelength band.

FIG. 7 is a sectional view of a part of a liquid crystal cell showing a second embodiment of the present invention. In this embodiment, red, green and blue color filters 15R, 15G and 15B of the liquid crystal cell are shown.
The thickness of the liquid crystal layer in each pixel corresponding to _{d R, d G,} is _{d B, d B}
The relationship is set to <d _G <d _R.
Since the other structure is the same as that of the first embodiment described above, the duplicated description will be omitted by giving the same reference numerals to the drawings.

In the liquid crystal display device of this embodiment, for example, the liquid crystal layer thickness d _R of the pixel corresponding to the red filter 15R is 5.09 μm, and the liquid crystal layer thickness d _G of the pixel corresponding to the green filter 15G is 4. 80 [mu] m, the liquid crystal layer thickness _{d B} of the pixel in which the blue filter 15B corresponding 4.54μm
When set to, CIE1976 indicates a hue change associated with a change in the viewing angle in the left-right direction of the screen when displaying 20% gray.
u'v 'The r value on the chromaticity diagram is 0.042, and the hue change on the chromaticity diagram is larger than that in the case where the liquid crystal layer thickness of each pixel is 5.09 μm (see FIG. 5). The radius r can be reduced by about 47%.

Therefore, according to the liquid crystal display element of this embodiment, it is possible to display a color image having a wide viewing angle and a smaller hue change due to the change of the viewing angle.

In the above first and second embodiments,
The viewing angle compensation films 21 and 22 are arranged on the front side and the rear side of the liquid crystal cell 10, respectively.
1, 22 may be arranged on at least one of the front side and the rear side of the liquid crystal cell 10.

Further, the viewing angle compensation film is not limited to a discotic liquid crystal film, and when other viewing angle compensation films such as various retardation films are used,
The present invention can be applied.

Further, in the above-mentioned embodiment, the liquid crystal layer thickness of the pixel for generating the wavelength band light, that is, the blue light, in which the transmittance is lowered when the viewing angle is inclined from the front direction by using the discotic liquid crystal film, is reduced to display. Although the hue change depending on the viewing angle is compensated, the invention is not limited to this.
For example, when another viewing angle compensation film is used and the transmittance of red light is lowered by tilting the viewing angle, the liquid crystal layer thickness of the red pixel is smaller than the liquid crystal layer thickness of pixels of colors in other wavelength bands. It may be appropriately reduced or increased. That is, in the liquid crystal display device of the present invention, the liquid crystal layer thickness of each pixel corresponding to the color filters of a plurality of colors is appropriately set according to the hue change characteristic of the transmitted light depending on the viewing angle of the viewing angle compensation film.

In addition, the liquid crystal display element is not limited to the active matrix type liquid crystal display element, but can be applied to a simple matrix type liquid crystal display element.

[0060]

According to the liquid crystal display element of the present invention, electrodes for forming a plurality of pixels are provided on the inner surfaces of a pair of front and rear substrates facing each other with a liquid crystal layer interposed therebetween, and the inner surface of the front substrate is provided with Arranging a viewing angle compensation film on at least one of the front side and the rear side of a liquid crystal cell provided with color filters of a plurality of colors corresponding to the plurality of pixels,
In addition, according to the change of the transmittance of each wavelength light depending on the viewing angle of the viewing angle compensation film, the hue change depending on the viewing angle of the liquid crystal layer thickness of each pixel corresponding to the plurality of color filters is compensated. Therefore, it is possible to display a color image having a wide viewing angle and a small change in hue due to the change in the viewing angle.

In the liquid crystal display device of the present invention, the viewing angle compensating film is made of a discotic liquid crystal film in which discotic liquid crystal molecules are gradually risen and oriented from one face to the other face in a collapsed state. Is preferable, and by doing so, the viewing angle can be made wider.

In this case, the liquid crystal layer of the liquid crystal cell is made of nematic liquid crystal having an initial alignment state in which liquid crystal molecules are substantially twisted at a twist angle of 90 °. Of the discotic liquid crystal film, the respective discotic liquid crystal molecules have the same orientation state face to each other, and the liquid crystal molecule orientation direction of the front discotic liquid crystal film is the liquid crystal molecules in the vicinity of the front substrate of the liquid crystal cell. Substantially parallel to the alignment direction, the liquid crystal molecule alignment direction of the rear discotic liquid crystal film is preferably arranged substantially parallel to the liquid crystal molecule alignment direction in the vicinity of the rear substrate of the liquid crystal cell. By doing so, the viewing angle can be further widened.

In the liquid crystal display device of the present invention, when the color filters of a plurality of colors provided on the inner surface of one substrate of the liquid crystal cell are color filters of three colors of red, green and blue, the red, Of the plurality of pixels to which the green and blue color filters respectively correspond, it is preferable to set the liquid crystal layer thickness of the pixel corresponding to the blue filter smaller than the liquid crystal layer thickness of the pixel corresponding to the red filter and the green filter, By doing so, it is possible to display a color image in which the hue change with the change of the viewing angle is small.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a liquid crystal display element showing a first embodiment of the present invention.

FIG. 2 is a sectional view of a part of a liquid crystal cell of the liquid crystal display device.

FIG. 3 is a diagram showing an arrangement state of a viewing angle compensation film of the liquid crystal display device.

FIG. 4 is a perspective view showing a molecular orientation state of the viewing angle compensation film.

FIG. 5 is a liquid crystal layer thickness difference d _B − between a pixel corresponding to a blue filter and a pixel corresponding to a red filter and a green filter.
shows the d _RG, the relationship between the radius r of the color change in CIE 1976 u'v 'chromaticity diagram in accordance with changes in the viewing angle in the horizontal direction of the screen when a white display.

FIG. 6 is a screen in white display when the liquid crystal layer thickness d _RG of the pixels corresponding to the red filter and the green filter is 4.80 μm and the liquid crystal layer thickness d _B of the pixels corresponding to the blue filter is 4.54 μm. CIE1976u'v 'chromaticity diagram showing the hue change with the change of the viewing angle in the left-right direction.

FIG. 7 is a partial sectional view of a liquid crystal cell showing a second embodiment of the present invention.

[Explanation of symbols]

10 ... Liquid crystal cell 11, 12 ... Substrate 11a, 12a ... Liquid crystal molecule alignment direction 13, 14 ... Electrode 15R, 15G, 15b ... Color filter 16 ... Liquid crystal layer 16a ... Nematic liquid crystal molecule 21, 22 ... Viewing angle compensation film 23, 24 ... Discotic liquid crystal films 23a, 24a ... Liquid crystal molecule orientation direction 25 ... Discotic liquid crystal molecules 26, 27 ... Polarizing plates 26a, 27a ... Absorption axis d _B ... Liquid crystal layer thickness d _{RG of} pixel to which blue filter corresponds ... Red filter and Liquid crystal layer thickness of pixel corresponding to green filter d _R Liquid crystal layer thickness of pixel corresponding to red filter d _G Liquid crystal layer thickness of pixel corresponding to green filter

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G09F 9/30 349 G09F 9/30 349B 9/35 9/35 F term (reference) 2H048 BA02 BB02 BB07 BB08 BB10 BB42 2H049 BA06 BA42 BB03 BB61 BC12 BC22 2H091 FA02Y FA11X FA11Z FB02 FD06 FD24 HA07 LA19 LA20 5C094 AA08 AA12 BA03 BA43 CA19 CA24 DA09 ED03 FA02 5G435 AA01 AA04 BB12 CC09 DD11 GG12 HH02

Claims (4)

[Claims] 1. An electrode for forming a plurality of pixels is provided on an inner surface of a pair of front and rear substrates that face each other with a liquid crystal layer interposed therebetween, and an electrode for forming a plurality of pixels is provided on the inner surface of any one of the substrates. A liquid crystal cell provided with color filters of a plurality of corresponding colors, and a viewing angle compensation film arranged on at least one of the front side and the rear side of the liquid crystal cell, and the viewing angle of the viewing angle compensation film. A liquid crystal display characterized by setting the liquid crystal layer thickness of each pixel corresponding to the color filters of the plurality of colors according to the change of the transmittance for each wavelength light so that the hue change depending on the viewing angle of the display is compensated. element. 2. The viewing angle compensation film is made of a discotic liquid crystal film in which discotic liquid crystal molecules are oriented so as to gradually rise from one face to the other face in a collapsed state. The liquid crystal display device according to item 1. 3. A liquid crystal layer of a liquid crystal cell is composed of a nematic liquid crystal having an initial alignment state in which liquid crystal molecules are substantially twisted at a twist angle of 90 °. Tick liquid crystal films face each other with the same alignment state of each discotic liquid crystal molecule, and align the liquid crystal molecule alignment direction of the front discotic liquid crystal film with the liquid crystal molecule alignment direction in the vicinity of the front substrate of the liquid crystal cell. And the liquid crystal molecule orientation direction of the discotic liquid crystal film on the rear side is substantially parallel to the liquid crystal molecule orientation direction near the rear substrate of the liquid crystal cell. The liquid crystal display element according to claim 2. 4. The liquid crystal cell is provided with color filters of three colors of red, green and blue, and among a plurality of pixels respectively corresponding to these color filters, a pixel corresponding to a blue filter has a liquid crystal layer thickness of The liquid crystal display element according to claim 3, wherein the red filter and the green filter are set to be smaller than the liquid crystal layer thickness of the corresponding pixel.