JPH10186329A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a liquid crystal display device possible to display with high quality while preventing the generation of colors due to the change of visual field at the time of displaying white color, by forming plural liquid crystal layers whose layer thicknesses are different in one pixel. SOLUTION: In this liquid crystal display device 21, one pixel 22 is formed out of first and second subpixels 23, 24 and layer thicknesses of first and second liquid crystal layers 25, 26 forming these pixels 23, 24 individually are different. Concretely, since a printed thin film is protrudingly provided in the inner surface of an upper glass substrate at positions of the subpixels 23, 24, the layer thickness of the second liquid crystal layer 26 to be positioned here is made thinner than that of the first liquid crystal layer 25. Since layer thicknesses of the liquid crystal layers 25, 26 are made different in such a manner, transmissivities with respect to the wavelength of a transmission light are different and the wavelength-tranmissivity obtained by averaging wavelength-transmissivities of the first and second subpixels 23, 24 is made to be the wavelength- transmissivity characteristic of the whole of the pixel 22.

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 in which at least one of them is applied with a horizontal electric field to a liquid crystal layer between transparent substrates to control the display of pixels.

[0002]

2. Description of the Related Art The development of liquid crystal display devices has been remarkable. The liquid crystal display device has a structure in which a pair of glass substrates are bonded at an interval of several μm, and a liquid crystal layer is sealed in the gap. In the following description, the direction of the thickness of the liquid crystal layer, which is the direction of the gap between the glass substrates, is referred to as the vertical direction, and the direction perpendicular to the direction parallel to the surface of the glass substrate is referred to as the horizontal direction.

In a liquid crystal display device driven by a thin film transistor (TFT), a device called a twisted nematic (TN) liquid crystal has been often used. This TN type liquid crystal display device drives liquid crystal molecules in a liquid crystal layer by an electric field (an electric field in a vertical direction) between both glass substrates.
However, because of the vertical electric field, the liquid crystal molecules change their direction in the vertical direction, and thus have a large viewing angle dependency.

The reason will be described below with reference to FIG. FIG. 14 is a side view schematically showing a state in which the TN liquid crystal cell of the liquid crystal display device is observed from the side. In the liquid crystal display device 1 exemplified here, a liquid crystal layer 3 is formed between a pair of glass substrates 2, and a transparent electrode (not shown) is formed on the inner surface of the glass substrate 2. A pair of polarizing plates (not shown) are individually mounted on the outer surfaces of the pair of glass substrates 2, and the directions of the polarization transmission axes of these polarizing plates are orthogonal to each other. The liquid crystal molecules 4 of the liquid crystal layer 3 are oriented such that their major axes are parallel to the horizontal direction, and the major axes extend from the top to the bottom of the liquid crystal layer 3 corresponding to the polarizing plate. It is oriented so that it is twisted at right angles.

In the liquid crystal display device 1 having the above configuration,
For example, light rays are emitted upward from below in the figure,
The transmitted light is viewed from above. When the pixel 2 transmits a light beam, the pixel 2 displays white, and when the pixel 2 blocks the light beam, the pixel 2 displays black.

[0006] The control of such a monochrome display is performed by the liquid crystal layer 3.
Is realized. In other words, when no electric field is applied to the liquid crystal layer 3, the polarization direction of the light beam transmitted through the lower polarizer rotates at right angles due to the liquid crystal molecules 4 of the liquid crystal layer 3, so that this light beam also transmits through the upper polarizer. I do. However, when an electric field is applied, the liquid crystal molecules 4 are inclined in the vertical direction as shown in the figure, so that rotation of the polarization direction of the light beam by the liquid crystal layer 3 is inhibited, and the light beam is not transmitted through the upper polarizing plate. As described above, the transmittance of the liquid crystal display device 1 changes depending on the presence or absence of the application of the electric field.

However, in the liquid crystal display device 1 as described above, as shown in the figure, the length of the liquid crystal molecules 4 appears to change even if the line of sight is inclined. In particular, the line of sight a from the rising direction of the liquid crystal molecules 4 and the line of sight b from the opposite direction appear to have significantly different lengths of the liquid crystal molecules 4. This is the cause of the viewing angle dependency that the transmittance changes as the viewing angle changes. Such a phenomenon is a common problem not only in TN liquid crystals but also in liquid crystal devices that move in the vertical direction.

On the other hand, a liquid crystal display device in which liquid crystal molecules are driven by a horizontal electric field has also been proposed.
No. 225388. This principle will be described below with reference to FIG. In the following description, the same portions as those of the liquid crystal display device 1 described above as the first conventional example are denoted by the same names and reference numerals, and detailed description is omitted.

First, in the liquid crystal display device 11 exemplified here, in order to apply an electric field to the liquid crystal molecules 4 in the horizontal direction, for example, an electrode of a predetermined shape is formed on the inner surface of one glass substrate 2. According to the above publication, the liquid crystal molecules 4 are aligned in a certain direction by an alignment process, and the direction of the polarization transmission axis of one of the polarizing plates coincides with the alignment direction. The polarization transmission axis of the other polarizing plate is orthogonal to this, and this direction corresponds to the major axis direction of the liquid crystal molecules 4 when an electric field is applied in the horizontal direction.

In the liquid crystal display device 11 having the above-described structure, light rays are not transmitted in an initial state where no electric field is applied to the liquid crystal molecules 4, and light rays are transmitted in a state where an electric field is applied. At this time, since the liquid crystal molecules 4 rotate in the horizontal direction, compared to the above-described liquid crystal display device 1 in which the liquid crystal molecules 4 rise in the vertical direction, the liquid crystal molecules having substantially the same length even in the case of the tilted line of sight a and the line of sight b. 4 will be observed. As mentioned above,
By rotating the liquid crystal molecules 4 in the plane of the substrate, even if the viewing angle changes, the change in pixel density is small, and a wide viewing angle characteristic can be obtained.

[0011]

As described above, the liquid crystal display device 11 that applies an electric field to the liquid crystal molecules 4 in the horizontal direction has less viewing angle dependence than the liquid crystal display device 1 that applies the electric field in the vertical direction. . However, a detailed examination reveals that the above-described lateral electric field method also has a viewing angle dependency.

This will be described below with reference to FIG. As described above, the liquid crystal molecules 4 are aligned in a certain direction, and the polarization transmission axis of one of the polarizing plates 5 is arranged so as to coincide with the alignment direction, and the other is set so that the polarization transmission axis is orthogonal to this. Are disposed. Therefore, in the initial state, the black pixel becomes transparent (white) by application of the horizontal electric field. When a horizontal electric field is applied by the pair of electrodes, the major axis of the liquid crystal molecules 4 is oriented in the direction of the electric field, and thus the liquid crystal molecules 4 are deviated from the polarization transmission axis of the orthogonally arranged polarizing plate 5, and light leakage occurs due to birefringence.

In general, the amount of transmitted light due to birefringence generally has wavelength dependence. This wavelength dependence is represented by the amount of birefringence d
・ Depends on △ n. Here, d is the layer thickness of the birefringent body, which here roughly corresponds to the layer thickness of the liquid crystal layer 3. Also,
Δn is the refractive index anisotropy and is an amount determined by the type of the liquid crystal material. As disclosed in JP-A-7-225388, if the amount of birefringence d · Δn can be set to about 0.21 to 0.36 μm, the wavelength dependence of the amount of transmitted light can be ignored. Therefore,
In this case, almost white display is possible at the front position.

However, if the user looks at the front position as the center during the white display, the pixels appear to be colored.
This can be explained by the viewing angle dependence of the refractive index anisotropy Δn and the layer thickness d. That is, xz in FIG.
When the line of sight is shaken in the plane, the layer thickness d of the cell appears to increase, but the refractive index anisotropy Δn does not change because the length of the liquid crystal molecules 4 does not change. Therefore, in this direction, the birefringence d · Δn appears to increase, and a color appears in the liquid crystal cell displaying white.

On the other hand, when the user looks his / her eyes in the yZ plane of FIG. 16, the cell thickness d is increased in the same manner. However, looking at the liquid crystal molecules 4 arranged in this direction, the liquid crystal molecules 4 appear to be shorter, and the refractive index anisotropy Δn decreases.
Since the decrease of Δn is larger than the increase of d, the product, that is, the amount of birefringence d · Δn, appears to decrease, and the color appears to appear in the liquid crystal cell.

As described above, in the liquid crystal operated by the lateral electric field, the amount of birefringence d · Δn decreases with respect to the line of sight in the direction in which the horizontal electric field is applied, and the line of sight changes in the direction perpendicular to the line. On the other hand, the birefringence d · Δn increases. For this reason, even if it is seen as a white display on the front, it looks as if it is colored from an oblique direction.

In particular, since the human eye is insensitive to coloring in a dark state, but sensitive to coloring in a bright state, a high contrast of a single wavelength in a wide viewing angle range is obtained in the lateral electric field method. Although a ratio can be obtained, a color is generated in a white display image.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has been made in a liquid crystal display device of a lateral electric field type having a wide viewing angle range, in which the occurrence of color due to a change in viewing angle during white display is prevented. It is intended to provide a device.

[0019]

According to the first aspect of the present invention,
A pair of substrates at least one of which is transparent are arranged to face each other, a liquid crystal layer forming pixels is sealed in a gap between the substrates, and an electric field is applied to the liquid crystal layer in a direction parallel to the surface of the substrate to display pixels. In a controlled liquid crystal display device, a plurality of liquid crystal layers having different layer thicknesses are formed in one pixel.

Accordingly, the average of the wavelength-transmittance characteristics of the liquid crystal layers having a plurality of layer thicknesses is the wavelength-transmittance characteristic of the pixel. Therefore, each wavelength-transmittance characteristic is determined by the thickness of the plurality of liquid crystal layers forming the pixel. If the transmittance characteristics are appropriately set, even if the wavelength-transmittance characteristics of a plurality of liquid crystal layers change due to a change in the viewing angle, the change in the wavelength-transmittance characteristics as a pixel is small.

According to a second aspect of the present invention, a pair of substrates, at least one of which is transparent, are opposed to each other, a liquid crystal layer forming pixels is sealed in a gap between the substrates, and a liquid crystal layer parallel to the surface of the substrate is provided in the liquid crystal layer. In a liquid crystal display device in which the display of a pixel is controlled by applying an electric field in a direction, a dichroic dye is mixed in the liquid crystal layer.

Therefore, the change in the transmittance characteristic of the liquid crystal layer due to the change in the viewing angle can be offset by the absorption of the dichroic dye, so that the change in the wavelength-transmittance characteristic of the pixel due to the change in the viewing angle can be reduced. . The dichroic dye referred to in the present invention is a dye having a large absorptivity in a direction orthogonal to the long axis of the molecule. For example, "G-206, 207" manufactured by Japan Photographic Dye Laboratories, etc. is there.

According to a third aspect of the present invention, a pair of substrates, at least one of which is transparent, are opposed to each other, a liquid crystal layer forming pixels is sealed in a gap between the substrates, and the liquid crystal layer is parallel to the surface of the substrate. In a liquid crystal display device in which the display of a pixel is controlled by applying an electric field in a direction, a dichroic absorption plate is arranged in parallel with the substrate.

Therefore, the change in the transmittance characteristic of the liquid crystal layer due to the change in the viewing angle can be offset by the absorption of the dichroic absorption plate, so that the change in the wavelength-transmittance characteristic of the pixel due to the change in the viewing angle can be reduced. it can.

According to a fourth aspect of the present invention, a pair of substrates, at least one of which is transparent, are opposed to each other, a liquid crystal layer forming pixels is sealed in a gap between the substrates, and a liquid crystal layer parallel to the surface of the substrate is provided in the liquid crystal layer. In a liquid crystal display device in which display of a pixel is controlled by applying an electric field in at least one direction, at least one pair of liquid crystal layers whose rotation directions of liquid crystal molecules are opposite to each other due to the application of the electric field are formed in one pixel.

Therefore, the average of the wavelength-transmittance characteristics of a plurality of liquid crystal layers in which the rotation directions of the liquid crystal molecules are opposite to each other is the wavelength-transmittance characteristic of the pixel, and the transmittance characteristics of the plurality of liquid crystal layers are changed by a change in the viewing angle. Since the directions changing with respect to the wavelength are also opposite, changes in the transmittance characteristics due to changes in the viewing angle can be canceled out to prevent changes in the wavelength-transmittance characteristics of the pixel.

According to a fifth aspect of the present invention, there is provided the liquid crystal display device according to the fourth aspect, further comprising electric field control means for controlling at least two directions in which electric field is applied to the liquid crystal layer in one pixel. I have.

Therefore, since an electric field is applied to the liquid crystal layer in two directions, the liquid crystal molecules rotate in opposite directions in these portions.

According to a sixth aspect of the present invention, in the liquid crystal display device according to the fifth aspect, the electric field control means comprises a convex portion protruding from one of a pair of electrodes opposed to each other via a liquid crystal layer.

Therefore, since an electric field is applied from the convex portion of one electrode to the other electrode, the application direction of the electric field is controlled in two directions.

[0031]

FIG. 1 shows a first embodiment of the present invention.
The application will be described with reference to FIGS. FIG. 1 is a schematic exploded perspective view showing a liquid crystal cell of one pixel of the liquid crystal display device, FIG. 2 is a side view schematically showing a state where the liquid crystal cell is observed from the side, and FIG. 4 and 5 are graphs showing the relationship between the wavelength of the transmitted light and the transmittance of each sub-pixel when the viewing angle is inclined, and FIG. 6 is a graph showing the relationship between the transmittance and the transmittance. 7 is a graph showing the relationship between the wavelength of transmitted light and the transmittance of one pixel in the case.

First, in the liquid crystal display device 21 according to the present embodiment, as shown in FIG. 1, one pixel 22 is formed by first and second sub-pixels 23 and 24.
The thicknesses of the first and second liquid crystal layers 25 and 26 that individually form No. 4 are different. More specifically, as shown in FIG.
At the position of the first and second sub-pixels 23 and 24, a printed thin film 27 is projected from the inner surface of the upper glass substrate 2, so that the second liquid crystal layer 26 located here is the first liquid crystal layer 26. The layer thickness is smaller than that of the liquid crystal layer 25.

In the liquid crystal display device 21 of the present embodiment, the liquid crystal molecules 4 of the first and second liquid crystal layers 25 and 26 are aligned in the x direction orthogonal to the y direction, which is the direction in which the liquid crystal layers 25 and 26 are connected. Are oriented so as to have a long axis, and a pair of electrodes (not shown) is individually formed in each of the pixels 22 so that a horizontal electric field is applied in the y direction.

In the liquid crystal display device 21 of the present embodiment, the first and second liquid crystal layers 25 and 26 have different transmittances with respect to the wavelength of transmitted light due to different layer thicknesses. As shown, the average of the wavelength-transmittance characteristics of the first and second sub-pixels 23 and 24 is the entire wavelength-transmittance characteristic of the pixel 22. As shown in FIGS. 4 and 5, the wavelength-transmittance characteristics of the first and second liquid crystal layers 25 and 26 change with a change in the viewing angle. The thickness is selected so that the characteristic of the transmittance of the pixel 22 does not vary much with a change in the viewing angle.

In the above configuration, in the liquid crystal display device 1 of the present embodiment, in the initial state where no lateral electric field is applied to the pixel 22, the first and second liquid crystal layers 25 and 26 are oriented in the x direction. The transmission of light is blocked by the pair of polarizing plates 5, and the pixel 22 displays black. When a horizontal electric field is applied to the pixel 22, the liquid crystal molecules 4 of the first and second liquid crystal layers 25 and 26 rotate in the y direction, so that light is transmitted through the pair of polarizing plates 5 and the pixel 22 becomes white. Is displayed.

When the lateral electric field is applied in this manner, the average of the wavelength-transmittance characteristics of the first and second sub-pixels 23 and 24 becomes the wavelength-transmittance characteristic of the pixel 22, as described above. As shown in FIG. 3, when observing the pixel 22 from the front, it can be seen that light is transmitted around a wavelength of 0.6 to 0.65 (μm).

In such a state, when the line of sight is inclined in the yz plane of FIG. 1, the apparent length of the liquid crystal molecules 4 becomes shorter, and the effective birefringence d · Δn becomes smaller. Therefore, as shown in FIG. 4, the maximum value of the wavelength-transmittance characteristic of each of the sub-pixels 23 and 24 moves to the shorter wavelength side. On the other hand, when the line of sight is inclined in the XZ plane of FIG. 1, the apparent thickness of the pixel 22 increases, so that the effective birefringence d · Δn increases, and as shown in FIG. The maximum value of the wavelength-transmittance characteristics of the pixels 23 and 24 moves to the longer wavelength side.

However, as described above, since the wavelength-transmittance characteristic of one pixel 22 is an average of the wavelength-transmittance characteristics of both sub-pixels 23 and 24, as shown in FIG. Thus, each of the sub-pixels 23 and 2 is changed according to the change of the viewing angle.
Even if the characteristic of No. 4 changes, the change of the characteristic as the pixel 22 is small. Therefore, in the liquid crystal display device 21 of the present embodiment, even when the viewing angle changes while displaying white, the rate of occurrence of color is extremely small, and an image can be displayed with high quality.

The present invention is not limited to the above-described embodiment, but allows various modifications without departing from the scope of the invention. For example, in the above embodiment, the liquid crystal layers 25 and 26 having different layer thicknesses are formed by projecting the printed thin film 27 on the inner surface of the glass substrate 2 only in half of the region of the pixel 22, as shown in FIG. As described above, this is also possible by using one glass substrate as the uneven substrate 28. In the above embodiment, two liquid crystal layers 2 having different thicknesses in the region of the pixel 22 are provided.
Although the arrangement of 5 and 26 has been described as an example, it is also possible to increase the number to 3 or more.

Next, a second embodiment of the present invention will be described with reference to FIG.
This will be described below with reference to FIG. FIG. 8 is a side view schematically showing a state in which a liquid crystal cell of one pixel of the liquid crystal display device is observed from the side, and FIG. 9 is a graph showing wavelength-transmittance characteristics of the pixel.

In the liquid crystal display device 31 of the present embodiment, as shown in FIG. 8, a dichroic dye 33 is mixed in a liquid crystal layer 32 made of aligned nematic liquid crystal. The dichroic dye 33 is a dye having a large absorptivity in a direction orthogonal to the long axis.

In the configuration described above, in the liquid crystal display device 31 of the present embodiment, the dichroic dye 3
3 rotates at high speed around the long axis. For this reason, the dichroic dye 33 generates a large absorptivity in the alignment direction of the liquid crystal molecules 4 and a small absorptivity in the two directions orthogonal thereto. Therefore, when this absorptivity is schematically illustrated, it can be represented as an absorption ellipsoid 34 flat in the alignment direction of the liquid crystal molecules 4 as shown in FIG.

FIG. 9 shows the transmittance characteristics of the liquid crystal alone and the absorption spectrum of the dichroic dye 33 during white display on the front. When viewed from the front, the dichroic dye 33 has a small absorption coefficient, so that it hardly affects the displayed image. When the line of sight is inclined from such a state, the transmittance characteristic of the single liquid crystal moves to the short wavelength side, but the absorption coefficient of the dichroic dye 33 at the short wavelength increases. For this reason, an increase in transmittance at a short wavelength due to a change in the viewing angle can be offset, and the rate of generation of white color is extremely small.

The liquid crystal display device 31 of the present embodiment is designed so that the change in the transmittance characteristic of the liquid crystal layer 32 and the change in the absorptivity of the dichroic dye 33 due to the change in the viewing angle cancel each other as described above. In addition, the generation of color due to a change in the viewing angle can be reduced, and an image can be displayed with high quality. Note that, in the liquid crystal display device 31 of the present embodiment, the absorption by the dichroic dye 33 remains even when displaying black,
Since human eyes are insensitive to coloring in a dark state, coloring cannot be recognized and no practical problem occurs.

Next, a third embodiment of the present invention will be described with reference to FIG.
0 will be described below. FIG. 10 is a side view schematically showing a state where the liquid crystal cell of one pixel of the liquid crystal display device is observed from the side.

In the liquid crystal display device 41 of the present embodiment, the dichroic absorption plate 42 in which the dichroic dyes 33 are arranged is arranged between the upper glass substrate 2 and the polarizing plate 5. The dichroic absorption plate 42 is formed, for example, by uniaxially or biaxially stretching a polymer substrate dyed with the dichroic dye 33, or by dyeing a uniaxially or biaxially stretched polymer film with the dichroic dye 33. It is formed by that. The dichroic absorption plate 42 thus formed is used for the dichroic dye 33.
Are oriented with the predetermined direction as the long axis, and here, the dichroic dye 33 and the liquid crystal molecules 4 are arranged such that the long axes of the liquid crystal molecules 4 coincide.

In the above-described configuration, in the liquid crystal display device 41 of the present embodiment, the alignment direction of the dichroic absorption plate 42 where the absorption is small corresponds to the alignment direction of the liquid crystal molecules 4 during white display (FIG. 10). In the y direction), it is possible to prevent the occurrence of color due to a change in the viewing angle as in the liquid crystal display device 31 described in the second embodiment.

The present invention is not limited to the above-described embodiment, but allows various modifications without departing from the gist of the present invention. For example, in the above-described embodiment, the dichroic absorbing plate 42 is arranged between the upper glass substrate 2 and the polarizing plate 5 as an example. However, this can be arranged at any position where light rays are transmitted. it can. In the above embodiment, the dichroic absorption plate 42 is provided separately from the glass substrate 2 and the polarizing plate 5. However, for example, the dichroic absorption plate 42 may also be used as a glass substrate. It is also possible.

Next, a fourth embodiment of the present invention will be described with reference to FIG.
This will be described below with reference to FIGS. FIG.
1 is a plan view schematically showing a state in which a liquid crystal cell of one pixel of a liquid crystal display device is observed from above, FIG. 12 is a plan view schematically showing the structure of an electrode, and FIG. 13 is a graph showing wavelength-transmittance characteristics. It is.

In the liquid crystal display device 51 according to the present embodiment, as shown in FIG. 11, first and second regions 52 and 53 are present in the liquid crystal layer 3 forming one pixel 22. , 53 are formed as a pair of liquid crystal layers in which the directions of rotation of the liquid crystal molecules 4 by application of an electric field are opposite.
In order to realize this, as shown in FIG. 12, a pair of electrodes 54 and 55 is provided with a protrusion 56 on one side as electric field control means, and an electric field is radially formed around the protrusion 56. The voltage is applied to the liquid crystal layer 3.

In the liquid crystal display device 51 of the present embodiment, when a horizontal electric field is applied to the liquid crystal layer 3 from the electrodes 54 and 55 in the liquid crystal display device 51 according to the present embodiment, the first The liquid crystal molecules 4 in the region 52 rotate clockwise, while the liquid crystal molecules 4 in the second region 53 rotate counterclockwise. When the electric field strength increases, the liquid crystal molecules 4 in both regions 52 and 53 are inclined at 45 ° with respect to the application direction of the lateral electric field, and the pixel 22 exhibits the maximum transmittance.

At this time, the directions of the liquid crystal molecules 4 in the first and second regions 52 and 53 are orthogonal to each other. Then
As shown in FIG. 12, the transmittance characteristics at the front of both regions 52 and 53 are the same, but the movement direction of the transmittance characteristics with respect to the wavelength in the opposite direction when viewed obliquely is opposite.
In other words, even if the viewing angle changes, the average transmittance characteristic of the pixel 22 does not change, so that the liquid crystal display device 51 of the present embodiment may generate color due to the change in the viewing angle when displaying white. And images can be displayed with high quality.

Further, as described above, the electric field control means for reversing the rotation direction of the liquid crystal molecules 4 is realized with a simple structure by the convex portion 56 of the electrode 54, so that the liquid crystal display device 51 of the present embodiment is Also, the productivity is good.

[0054]

According to the first aspect of the present invention, a pair of substrates, at least one of which is transparent, are opposed to each other, a liquid crystal layer forming pixels is sealed in a gap between the substrates, and the surface of the substrate is filled in the liquid crystal layer. In a liquid crystal display device in which display of a pixel is controlled by applying an electric field in a parallel direction, a plurality of liquid crystal layers having different layer thicknesses are formed in one pixel, so that a plurality of liquid crystal layers are formed. If the thickness is appropriately selected, even if the wavelength-transmittance characteristics of a plurality of liquid crystal layers change due to a change in the viewing angle, the change in the wavelength-transmittance characteristics as a pixel is small. An image can be displayed with high quality by preventing the generation of color due to the change.

According to a second aspect of the present invention, a pair of substrates, at least one of which is transparent, are opposed to each other, a liquid crystal layer forming pixels is sealed in a gap between the substrates, and a liquid crystal layer parallel to the surface of the substrate is provided in the liquid crystal layer. In a liquid crystal display device in which the display of a pixel is controlled by applying an electric field in a direction, a change in the transmittance characteristic of the liquid crystal layer due to a change in the viewing angle is caused by mixing a dichroic dye in the liquid crystal layer. Can be offset by the absorption of the dichroic dye, so that the change in the wavelength-transmittance characteristic of the pixel due to the change in the viewing angle can be reduced, and that the color is generated due to the change in the viewing angle when displaying white. It is possible to display the image with high quality by preventing it.

According to a third aspect of the present invention, a pair of substrates, at least one of which is transparent, are arranged to face each other, a liquid crystal layer forming pixels is sealed in a gap between the substrates, and a liquid crystal layer parallel to the surface of the substrate is provided in the liquid crystal layer. In a liquid crystal display device in which the display of pixels is controlled by applying an electric field in the direction, the dichroic absorption plate is arranged in parallel with the substrate, so that the transmittance characteristic of the liquid crystal layer due to a change in viewing angle is reduced. Since the change can be offset by the absorptivity of the dichroic absorption plate, the change in the wavelength-transmittance characteristic of the pixel due to the change in the viewing angle can be reduced, and the color is generated by the change in the viewing angle when displaying white. The image can be displayed with high quality by preventing such a situation.

According to a fourth aspect of the present invention, a pair of substrates, at least one of which is transparent, are arranged to face each other, a liquid crystal layer forming pixels is sealed in a gap between the substrates, and a liquid crystal layer parallel to the surface of the substrate is provided in the liquid crystal layer. In a liquid crystal display device in which the display of a pixel is controlled by applying an electric field in a direction, at least a pair of liquid crystal layers in which the rotation directions of the liquid crystal molecules by application of the electric field are opposite to each other are formed in one pixel. Since the change in the wavelength-transmittance characteristic due to the change in the viewing angle of the plurality of liquid crystal layers in which the rotation directions of the liquid crystal molecules are opposite to each other can be offset, the change in the wavelength-transmittance characteristic of the pixel due to the change in the viewing angle can be prevented. Thus, it is possible to prevent a color from being generated due to a change in the viewing angle when displaying white, and to display an image with high quality.

According to a fifth aspect of the present invention, there is provided the liquid crystal display device according to the fourth aspect, wherein electric field control means for controlling at least two directions in which electric field is applied to the liquid crystal layer in one pixel is provided. Accordingly, the rotation directions of the liquid crystal molecules when applying an electric field to at least a pair of liquid crystal layers in one pixel can be reversed.

According to a sixth aspect of the present invention, in the liquid crystal display device of the fifth aspect, the electric field control means comprises a convex portion protruding from one of a pair of electrodes opposed to each other via a liquid crystal layer. Thereby, the application direction of the electric field can be controlled in two directions with a simple structure.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view schematically illustrating a liquid crystal cell of one pixel of a liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a side view schematically showing a liquid crystal cell.

FIG. 3 is a graph showing wavelength-transmittance characteristics when a pixel is visually recognized from the front.

FIG. 4 is a graph showing wavelength-transmittance characteristics when the first and second sub-pixels are visually recognized in the xz plane.

FIG. 5 is a graph showing wavelength-transmittance characteristics when the first and second sub-pixels are visually recognized in the yz plane.

FIG. 6 is a graph showing wavelength-transmittance characteristics when a pixel is viewed from each direction.

FIG. 7 is a side view schematically showing a liquid crystal cell of a liquid crystal display device according to a modification.

FIG. 8 is a side view schematically showing a liquid crystal cell of a liquid crystal display device according to a second embodiment of the present invention.

FIG. 9 is a graph showing wavelength-transmittance characteristics when a pixel is viewed from each direction.

FIG. 10 is an exploded perspective view schematically illustrating a liquid crystal cell of a liquid crystal display device according to a third embodiment of the present invention.

FIG. 11 is a plan view schematically showing a liquid crystal cell of a liquid crystal display device according to a fourth embodiment of the present invention.

FIG. 12 is a plan view schematically showing a structure of an electrode.

FIG. 13 is a graph showing wavelength-transmittance characteristics of first and second regions of a liquid crystal layer.

FIG. 14 is a side view schematically showing a liquid crystal cell of the liquid crystal display device of the first conventional example.

FIG. 15 is a side view schematically showing a liquid crystal cell of a liquid crystal display device of a second conventional example.

FIG. 16 is an exploded perspective view schematically showing a liquid crystal cell.

[Explanation of symbols]

 2 Glass substrate 3, 32 Liquid crystal layer 4 Liquid crystal molecule 5 Polarizer 21, 31, 41, 51 Liquid crystal display device 22 Pixel 23 First subpixel 24 Second subpixel 25 First liquid crystal layer 26 Second liquid crystal layer 27 Printed thin film 28 Uneven substrate 33 Dichroic dye 34 Absorption ellipsoid 42 Dichroic absorption plate 52 First region 53 Second region 54, 55 Electrode 56 Projection

Claims (6)

[Claims] A pair of substrates, at least one of which is transparent, are opposed to each other, a liquid crystal layer forming pixels is sealed in a gap between the substrates, and an electric field is applied to the liquid crystal layer in a direction parallel to the surface of the substrate. A liquid crystal display device wherein the display of pixels is controlled by a plurality of liquid crystal layers, wherein a plurality of liquid crystal layers having different layer thicknesses are formed in one pixel. 2. A pair of substrates, at least one of which is transparent, is disposed to face each other, a liquid crystal layer forming pixels is sealed in a gap between the substrates, and an electric field is applied to the liquid crystal layer in a direction parallel to the surface of the substrate. A liquid crystal display device wherein a display of pixels is controlled by mixing a dichroic dye into the liquid crystal layer. 3. A pair of substrates, at least one of which is transparent, is opposed to each other, a liquid crystal layer forming pixels is sealed in a gap between the substrates, and an electric field is applied to the liquid crystal layer in a direction parallel to the surface of the substrate. 1. A liquid crystal display device according to claim 1, wherein a dichroic absorption plate is arranged in parallel with said substrate. 4. A pair of substrates, at least one of which is transparent, is disposed to face each other, a liquid crystal layer forming pixels is sealed in a gap between the substrates, and an electric field is applied to the liquid crystal layer in a direction parallel to the surface of the substrate. A liquid crystal display device in which display of a pixel is controlled by using at least a pair of liquid crystal layers in which rotation directions of liquid crystal molecules are opposite to each other by application of an electric field, are formed in one pixel. 5. The liquid crystal display device according to claim 4, further comprising electric field control means for controlling at least two directions in which electric field is applied to the liquid crystal layer in one pixel. 6. The liquid crystal display device according to claim 5, wherein said electric field control means comprises a convex portion protruding from one of a pair of electrodes opposed to each other with a liquid crystal layer interposed therebetween.