JP2003186015A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress generation of a disclination line on an image. <P>SOLUTION: A reflective liquid crystal display device with liquid crystal molecules of a vertical alignment mode, is provided with a first means to convert incident light to linearly polarized light and a second means to convert the linearly polarized light to circularly or elliptically polarized light on an optical path of the incident light, and at the same time, is provided with a third means to convert circularly or elliptically polarized light to linearly polarized light and a fourth means to draw out linearly polarized light with an axis of polarization different to that of the linearly polarized light obtained with the first means by 90° on an optical path of the reflected light. <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, and more particularly to a reflective liquid crystal display device using liquid crystal molecules having a vertical alignment mode.

[0002]

2. Description of the Related Art In recent years, a projection type liquid crystal display device for displaying a large-scale and high-definition image for business or home has been receiving attention. In the case of the projection type, since an image is enlarged and projected, higher definition and higher contrast image performance is required as compared with a direct view type liquid crystal display device.

The liquid crystal display system is roughly classified into a reflective type and a transmissive type. In the reflective liquid crystal display system, since wirings and circuits can be formed under the reflective electrodes, pixels can be densely arranged. Widely used in projection type liquid crystal display devices because they can be integrated and can project a brighter and higher resolution image without the need to consider an opening like a transmission type liquid crystal element. .

Further, in recent projection type liquid crystal display devices, vertical alignment type (homeotropic alignment mode) liquid crystal molecules capable of obtaining high contrast are adopted as a liquid crystal layer. The vertical alignment type liquid crystal molecules exhibit negative dielectric anisotropy, and are aligned in a direction substantially perpendicular to the substrate surface in the initial state, and are aligned substantially parallel to the substrate surface by applying a voltage.

11 (a) and 11 (b) are schematic configuration diagrams showing the input / output relationship of light in a projection type liquid crystal display device using a conventional polarization beam splitter 200. As shown in FIG. Figure 11
11A shows a black display state, and FIG. 11B shows a white display state. The reflective liquid crystal element 1100 includes a transparent substrate 110 having a transparent electrode formed on the inner surface and a reflective substrate 130 having a reflective electrode on the inner surface, and a liquid crystal layer 120 is sandwiched between the substrates. The liquid crystal layer 120 exhibits alignment depending on the voltage between the substrates according to the alignment mode of the liquid crystal molecules used.

For example, linearly polarized light (s-polarized light) which is incident light
Enters the liquid crystal display device 1100 via the beam splitter (PBS) 200, and is then polarized by the liquid crystal layer 120 according to the alignment mode of the liquid crystal molecules. For example, when the liquid crystal layer 120 exhibits a birefringence effect, the incident linearly polarized light becomes elliptically polarized light, of which the PB polarized light is PB.
The light passes through S200 and is output as projection light via the projection lens 700.

FIG. 12 shows an example of the alignment state of liquid crystal molecules. The orientation of the liquid crystal molecules can be defined by the tilt angle θp and the plane azimuth angle θx. Here, the tilt angle θp is an angle obtained by subtracting the angle formed by the long axis of the liquid crystal molecule and the axis perpendicular to the substrate surface from π / 2, and the plane azimuth angle θx is the polarization axis direction of the incident light x. When referred to as an axis, it means an angle formed by the x-axis and the long axis of liquid crystal molecules in the plane of the liquid crystal substrate.

In general, liquid crystal molecules are given a plane azimuth angle θx of 45 degrees by rubbing the surface of the substrate.

[0009]

In the liquid crystal display device, the pixel density is decreasing year by year due to the demand for higher resolution. Particularly, in the projection type liquid crystal display device, it is required for the liquid crystal element in order to enlarge and project the image. The demand for miniaturization is high.

However, since the liquid crystal molecules change their orientation according to the applied voltage between the common electrode (transparent electrode) corresponding to each pixel and the pixel electrode, when the individual pixel size becomes small, they are adjacent to each other. The distance to the pixel becomes narrower,
It becomes easy to be influenced by the applied voltage applied to the adjacent pixel. In particular, when the target pixel is a pixel that should display white and the adjacent pixel is a pixel that should display black,
Since the applied voltage applied to each adjacent pixel is different, a potential gradient (horizontal electric field) due to the potential difference is generated between the adjacent pixels.

The plane azimuth angle of the liquid crystal molecules is usually set at an angle of 45 degrees with respect to the polarization axis of the incident light. However, when a lateral electric field is generated, the in-plane azimuth angle shifts at the peripheral portion of the pixel. Occurs.

As a result, for example, in the case of performing the stripe display in which the black display and the white display are alternately displayed for each pixel, a portion having a different orientation is generated in the peripheral portion of the pixel which should be the white display. This appears as a line-shaped display defect called a disclination line on the image.

In particular, when the liquid crystal molecules are in the vertical alignment mode, the liquid crystal molecules are almost perpendicular to the substrate surface.
The alignment regulating force of the alignment film with respect to the liquid crystal molecules becomes small, and it is easily affected by the lateral electric field. Therefore, a disclination line is likely to occur.

A color image is produced by synthesizing three liquid crystal elements (liquid crystal panels) for each of R, G, and B colors. When a disclination line occurs, not only the contrast is lowered, but also the contrast is lowered. When a white color or a complementary color is displayed, the misaligned portion of the disclination line looks colored, which deteriorates the image quality.

Therefore, an object of the present invention is to provide a liquid crystal display device capable of suppressing the occurrence of disclination lines on an image in a reflection type liquid crystal display device in order to solve these conventional problems. is there.

[0016]

A feature of the liquid crystal display device of the present invention is that a transparent substrate having a transparent electrode and a substrate having a drive circuit and a reflective electrode are arranged so that their electrode surfaces face each other. A reflection type liquid crystal element in which a liquid crystal layer containing liquid crystal molecules having a vertical alignment mode is sandwiched between the two substrates, and linearly polarized light is obtained on an incident light optical path to the reflection type liquid crystal element.
Means and second means for changing the linearly polarized light obtained by the first means into circularly polarized light or elliptically polarized light, and the circularly polarized light or the elliptically polarized light is substantially linearly polarized light on the optical path of the reflected light from the reflective liquid crystal element. The third means is provided, and the fourth means for extracting the linearly polarized light having a polarization axis different from the optical axis of the linearly polarized light obtained by the first means by 90 degrees is provided.

According to the above feature of the present invention, the influence of the plane orientation of the liquid crystal molecules on the intensity of light emitted from the reflective liquid crystal element is reduced by making circularly polarized light or elliptically polarized light incident on the reflective liquid crystal element. You can Therefore, due to the miniaturization of the pixel size, due to the influence of the lateral electric field from the adjacent element,
Even if the plane orientation of the liquid crystal molecules at the peripheral edge of the pixel changes, the influence on the output intensity can be suppressed, so the occurrence of disclination lines on the image due to the influence of the lateral electric field as in the past can be suppressed. it can.

The liquid crystal display device of the present invention is characterized in that, in the above characteristics, the first retardation plate is used as the second means and the third means is used.
When the second retardation plate is used as the means, the phase difference between the first retardation plate and the second retardation plate is different from the phase difference generated in the reflective liquid crystal element, and the center wavelength of the incident light is different. Is the sum of the retardations of the first retardation plate and the second retardation plate, the value obtained by subtracting the retardation generated in the reflective liquid crystal element is 0.8λ / 2 to 1.2λ / 2.
You may adjust so that it may become the range of.

In this case, the first retardation plate on the incident optical path and the first retardation plate on the outgoing optical path are considered in consideration of the phase difference generated in the reflective liquid crystal element itself due to the influence of the tilt angle given to the liquid crystal molecules in the initial state. Since the phase difference of the two phase difference plates is determined, the reflected light from the reflective liquid crystal element can be more reliably returned to the linearly polarized light. Therefore, not only the occurrence of disclination lines can be reduced, but also an image having high contrast can be obtained.

[0020]

DETAILED DESCRIPTION OF THE INVENTION (First Embodiment) FIG.
The projection type liquid crystal display device according to the first embodiment will be described with reference to FIGS.

As shown in FIGS. 1A and 1B, the projection type liquid crystal display device according to the first embodiment of the present invention is
A first polarizing plate 60a for extracting linearly polarized light from the incident light on the optical path of the incident light to the reflective liquid crystal element 100 and a first phase difference having a phase difference of λ / 4, which changes the linearly polarized light into circularly polarized light or elliptically polarized light, or a phase difference close thereto. The board 50a is provided. Further, on the optical path of the reflected light from the reflective liquid crystal element 100, the second retardation plate 50b having a phase difference of λ / 4 or close to it, which changes the circularly polarized light or the elliptically polarized reflected light into linearly polarized light, Two
And a polarizing plate (analyzer) 60b. Here, FIG. 1A shows a case of black display, and FIG. 1B shows a case of white display.

The reflective liquid crystal element 100 has a transparent substrate 10 and a reflective substrate 30 which are arranged to face each other, and a liquid crystal layer 20 is sandwiched between them. Although not shown, a transparent electrode that is a common electrode is formed on the facing surface of the transparent substrate 10, and a MOS transistor or a TFT or the like formed for each pixel is driven on the facing surface of the reflecting substrate 30. The circuits and the reflective electrodes are formed in a matrix. As the pixel size, for example, fine pixels of about 10 μm × 10 μm square are formed.

As the liquid crystal molecules constituting the liquid crystal layer 20,
Vertically aligned nematic liquid crystal having negative dielectric anisotropy is used.

On the surfaces of the transparent substrate 10 and the reflective substrate 30 in contact with the liquid crystal layer 20, liquid crystal molecules are oriented,
For example, an alignment film (not shown) made of a rubbing-treated polyimide film is formed, and a liquid crystal molecule in an initial state has a tilt angle of, for example, about 80 to 85 degrees and a surface of about 45 degrees with respect to the polarization axis of the polarizing plate. Azimuth is given.

FIG. 2 is a device perspective view showing the relationship between incident light and emitted light in the projection type liquid crystal display device according to the first embodiment shown in FIGS. 1 (a) and 1 (b). Here, a normally black (NB) mode in which black is displayed in a state where no electric field is applied to each pixel electrode (initial state) is shown.

Incident light output from a light source (not shown) is
First, only linearly polarized light having a polarization axis in the x-axis direction is extracted by the first polarizing plate 60a, and further, in the process of passing through the first retardation plate 50a having a phase difference of λ / 4 or close thereto, a counterclockwise direction is obtained. Circularly polarized light or elliptically polarized light is incident on the reflective liquid crystal element 100 in this state.

The light incident on the reflective liquid crystal element 100 passes through the liquid crystal layer, is reflected by the reflective electrode, and further passes through the liquid crystal layer to be emitted. The emitted light is output by the second retardation plate 50b whose optical axis differs from that of the first retardation plate 50a by approximately 90 degrees
It is returned to linearly polarized light. When this linearly polarized light passes through the second polarizing plate (analyzer) 60b, it is enlarged and projected on a screen (not shown) through a projection lens (not shown).

In the normally black mode, the second polarizing plate 60b is arranged so that its polarization axis differs from that of the first polarizing plate 60a by 90 degrees. Therefore, when the liquid crystal molecules of the reflective liquid crystal element 100 show an alignment (vertical alignment mode) substantially perpendicular to the substrate surface in the initial state, the linearly polarized light returned by the second retardation plate 50b is the second polarizing plate 60.
b cannot be passed, and black display occurs.

FIG. 3A shows an example of an image on the screen obtained by the projection type liquid crystal display device according to the first embodiment. An example of an enlarged projected image when bright and dark vertical lines are displayed every other pixel in the horizontal direction is shown. The lower part of the figure shows the light output value of each pixel. FIG. 3B is a projection-type liquid crystal display device in which the first retardation plate 50a and the second retardation plate 50b are removed from the projection-type liquid crystal display device according to the first embodiment, that is, a conventional type in which linearly polarized light is incident. 3 shows an example of an image on a screen obtained by the projection type liquid crystal display device of FIG.

As can be seen by comparing the two, according to the projection type liquid crystal display device of the first embodiment, FIG.
Since the occurrence of disclination lines in the white display image as shown in (4) is suppressed, the display quality can be significantly improved.

The disappearance of the disclination line in the projection type liquid crystal display device according to the first embodiment is explained as follows.

[0032] In the conventional projection type liquid crystal display device, the incident light intensity of the reflection type liquid crystal element 100 I _{i n,} the output light intensity I
_{If out} , it is expressed by the following equation.

I _out = I _in · sin ² (2θ _x ) × sin ² (δ / 2) ··· (1) where θ _x is the plane azimuth angle of the liquid crystal molecules, and δ is the phase difference (= 2πΔnd / λ). Here, Δnd is a value called retardation. Therefore, if the plane azimuth θ _x of the liquid crystal molecules is set to 45 degrees, sin
^{Since 2} (2θ _x ) becomes 1, the emitted light intensity I _out is not affected by the plane azimuth angle θ _x . However, when the plane orientation angle theta _x of the liquid crystal molecules deviates from 45 ° by a lateral electric field due to the influence of adjacent elements, fluctuates exit light intensity I _out by plane orientation angle theta _x, partially emission intensity I _{ou t} is It becomes low, and this becomes a cause of the disclination line.

On the other hand, like the projection type liquid crystal display device according to the first embodiment, the incident light on the reflection type liquid crystal element 100 is changed into circularly polarized light or elliptically polarized light by the λ / 4 retardation plate and is incident. In that case, the intensity I _{out of the} output light is expressed by the following equation (2) that does not depend on the plane azimuth angle θx of the liquid crystal molecule by the calculation of the Jones vector known to those skilled in the art.

I _out = I _in · sin ² (δ / 2) (2) Therefore, when circularly polarized light or elliptically polarized light is used as the incident light, the intensity of the emitted light is determined when the wavelength of the incident light is determined. Is determined only by the retardation Δnd of the liquid crystal layer, not by the plane azimuth angle θ _x of the liquid crystal molecules, so that even if the plane azimuth angle θ _x of the liquid crystal molecules changes due to the lateral electric field from the adjacent element, the output intensity will have an effect. Since it receives almost no noise, it is possible to reduce the occurrence of disclination lines.

Therefore, the brightness of the image does not decrease, and the MTF (Modulation Transfer) is high even if the pixel is made finer.
Function) can be maintained, so that it is possible to provide a liquid crystal display device suitable for a projection type liquid crystal display device that requires high definition.

(Second Embodiment) In the above-described first embodiment, for example, when the phase difference between the first retardation plate and the second retardation plate is λ / 4, the disclination line is Although it is possible to suppress the occurrence of the above, the image contrast may not be sufficiently obtained in some cases.

On the other hand, the projection type liquid crystal display device according to the second embodiment is different from the liquid crystal display device according to the first embodiment described above in that the first phase difference plate and the second phase difference plate are included. The retardation (= Δnd) is further optimized to provide an image with higher contrast.

FIG. 4 shows the configuration of the projection type liquid crystal display device according to the second embodiment. The basic layout of each part is 1st
This is almost the same as the projection type liquid crystal display device according to the embodiment. That is, the first polarizing plate 61a and the first retardation plate 51a are arranged on the incident light optical path to the reflective liquid crystal element 100, and the second retardation plate 5 is disposed on the reflected light optical path from the reflective liquid crystal element 100.
1b and the 2nd polarizing plate 61b are arrange | positioned.

The reflective liquid crystal element 100 having the same structure is used. Here, it is assumed that the liquid crystal molecules of the liquid crystal layer are of vertical alignment type, and the plane azimuth angle thereof is 45 degrees with respect to the polarization axis (x axis) of the first polarizing plate 61a. In addition, this projection type liquid crystal display device is in the normally black mode, and includes the first polarizing plate 61a and the second polarizing plate 61b.
The polarization axes of are arranged so as to intersect.

The incident light passing through the first retardation plate 51a becomes counterclockwise circular or elliptically polarized light, and the reflection type liquid crystal element 100
The light reflected by is circularly polarized light in the clockwise direction or elliptically polarized light.

In the liquid crystal display device according to the second embodiment, the phase difference of the second phase difference plate 51b is larger than that of the first phase difference plate 51a, and more specifically, the phase difference of the second phase difference plate 51b. Is increased by the phase difference generated in the reflective liquid crystal element 100.

Usually, the vertical alignment type liquid crystal molecules in the initial state are
The tilt angle (θp) and the plane azimuth angle (θx) are given by the alignment film in order to define the direction in which the pixel is tilted when an electric field is applied, rather than being completely perpendicular to the substrate surface. Therefore, even in the initial state, a phase difference occurs in the light reflected from the reflective liquid crystal element due to the influence of the tilt angle. Therefore, in the case of the normally black mode, the phase difference between the first retardation plate and the second retardation plate is taken into consideration in consideration of the retardation of light generated by the alignment of the liquid crystal molecules in the initial state, that is, the state where no electric field is applied. Determining the phase difference will allow better black display and improve the image contrast.

Specifically, for example, in the vertical alignment type liquid crystal molecules in the initial state, 45 with respect to the polarization axis (x-axis direction) of the polarizing plate.
When the retardation of the first retardation plate 51a is λ / 4, the second retardation plate 51a has a surface azimuth angle (θx) of 80 degrees and a tilt angle (θp) of 80 degrees.
The retardation of b is more than that of the first retardation plate 51a.
The retardation generated because the tilt angle of the liquid crystal is given, that is, in this case, it is increased by about 0.1 × λ / 4. When the central wavelength λ of the incident light is 550 nm, the retardation of the first retardation plate 51a is 13/4 nm because it is λ / 4, and the retardation of the second retardation plate 51b is 0.1 × λ / It is set to about 150 nm by adding 15 degrees which is 4.

The retardation of the first retardation plate 51a is not limited to λ / 4 and may take a value other than λ / 4.

Table 1 is obtained on each screen of the projection type liquid crystal display device and each retardation of the suitable second retardation plate 51b when various values are adopted as the retardation of the first retardation plate 51a. The results of simulations of image contrast and disclination line disappearance effect are shown.

[0047]

[Table 1] As can be seen from Table 1, when both the retardations of the first retardation plate 51a and the second retardation plate 51b are set to λ / 4 as in the projection type liquid crystal display device of the first embodiment, the disclination is Although the line extinction effect is high, the contrast ratio is not sufficient. On the other hand, if the retardation of the second retardation plate is made larger than the retardation of the first retardation plate by about 0.1λ / 2, the contrast can be improved. However, the first and second retardation plates 51a and 51b
If the retardation of is out of λ / 4, the effect of eliminating the disclination line is reduced. Therefore,
The value obtained by subtracting the difference between the first retardation plate and the second retardation plate from the sum of the retardations is 0.8λ / 2 to 1.2.
By setting the range of λ / 2, more preferably λ / 2, it is possible to obtain a projection type liquid crystal display device which has a high contrast and has the highest effect of eliminating disclination lines.

In order to make the phase difference between the first retardation plate 51a and the second retardation plate 51b equal to the phase difference generated in the reflective liquid crystal display element, the first retardation plate 51a and the second retardation plate 51b can be adjusted. This is equivalent to adjusting the phase difference of the phase difference plate 51b so that the output of the emitted light during black display is minimized.

(Third Embodiment) The projection type liquid crystal display device according to the third embodiment is a modification of the projection type liquid crystal display device according to the second embodiment.

Similar to the reflective liquid crystal display device according to the second embodiment, the retardations of the first retardation plate and the second retardation plate are optimized in consideration of the retardation caused by the reflective liquid crystal element. It has a structure.

FIG. 5 shows the configuration of a projection type liquid crystal display device according to the third embodiment. The arrangement of basic parts is the second
This is almost the same as the projection type liquid crystal display device according to the embodiment. That is, the first polarizing plate 62a and the first retardation plate 52a are provided on the incident light optical path to the reflective liquid crystal element 100, and the second retardation plate 52b is provided on the reflected light optical path from the reflective liquid crystal element 100.
And a second polarizing plate 62b, and the reflective liquid crystal element 1 is provided.
The same configuration is used as 00.

However, in the reflective liquid crystal element 100 of the third embodiment, the point that the plane azimuth angle is given to the liquid crystal molecules in the direction intersecting the optical axis of the first retardation plate 52a by 90 degrees. different. In this case, the phase difference generated in the reflective liquid crystal element 100 is in the opposite direction to that in the second embodiment,
The phase difference at the second retardation plate 52b is calculated by the first retardation plate 51a.
It is desirable to make the phase difference generated in the reflective liquid crystal element smaller than the phase difference of.

For example, the plane orientation given to the liquid crystal molecules is −
When the central wavelength of incident light is 550 nm, λ / 4 is 137.5 nm when the tilt wavelength is 45 ° and the tilt angle is 80 °, but the necessary retardation in the second retardation plate 52b is λ. Approximately 123 nm, which is obtained by subtracting retardation 0.1 × λ / 4 generated in the reflective liquid crystal element from / 4, is a standard.

(Fourth Embodiment) The projection type liquid crystal display device according to the fourth embodiment is also a modification of the projection type liquid crystal display device according to the second embodiment.

Similar to the projection type liquid crystal display device according to the second and third embodiments, the retardation of the first retardation plate and the second retardation plate is set in consideration of the phase difference caused by the reflection type liquid crystal element. It has an optimized configuration.

FIG. 6 shows the structure of a projection type liquid crystal display device according to the fourth embodiment. The arrangement of basic parts is the second
This is almost the same as the projection type liquid crystal display device according to the embodiment. That is, the first polarizing plate 63a and the first retardation plate 53a are provided on the incident light optical path to the reflective liquid crystal element 100, and the second retardation plate 53b is provided on the reflected light optical path from the reflective liquid crystal element 100.
And a second polarizing plate 63b having a polarization axis crossing the polarization axis of the first polarizing plate 63a, and the reflective liquid crystal element 100 having the same configuration is used.

The reflective liquid crystal element 100 of the fourth embodiment.
The liquid crystal molecules in (1) are given the same orientation as in the second embodiment, but the optical axis of the first retardation plate 53a is arranged in a direction intersecting the plane orientation of the liquid crystal molecules by 90 degrees. Different. Therefore, the light that has passed through the first retardation plate 53a becomes clockwise circular or elliptically polarized light, and the reflective liquid crystal element 1
Light incident on the liquid crystal element 100 and reflected by the liquid crystal element 100 becomes counterclockwise circular or elliptically polarized light.

In this case, the phase difference in the second retardation plate 53b is made smaller than that in the first retardation plate 53a. That is, when the liquid crystal molecules are provided with an orientation of +45 degrees and a tilt angle of 80 degrees, λ / 4 is 137.5 nm when the center wavelength of incident light is 550 nm. 2 Phase difference plate 5
The required retardation in 2b is about 123 nm, which is obtained by subtracting the retardation 0.1 × λ / 4 generated in the reflective liquid crystal element from λ / 4.

(Fifth Embodiment) The projection type liquid crystal display device according to the fifth embodiment is also a modification of the projection type liquid crystal display device according to the second embodiment.

Similar to the reflective liquid crystal display devices according to the second to fourth embodiments, the retardation of the first retardation plate and the second retardation plate is set in consideration of the retardation caused by the reflective liquid crystal element. It has an optimized configuration.

FIG. 7 shows the configuration of a projection type liquid crystal display device according to the fifth embodiment. The arrangement of basic parts is the second
This is almost the same as the projection type liquid crystal display device according to the embodiment. That is, the first polarizing plate 64a and the first retardation plate 54a are provided on the incident light optical path to the reflective liquid crystal element 100, and the second retardation plate 54b is provided on the reflected light optical path from the reflective liquid crystal element 100.
And a second polarizing plate 64b having a polarization axis intersecting with the polarizing axis of the first polarizing plate 64a, and the reflective liquid crystal element 100 having the same configuration is used.

The reflective liquid crystal device 100 of the fifth embodiment.
The liquid crystal molecules in are given the same orientation as in the third embodiment, and are different in that the optical axis of the first retardation plate 54a is arranged in a direction substantially parallel to the plane orientation of the liquid crystal molecules. . The light passing through the first retardation plate 54a becomes clockwise circular or elliptically polarized light and enters the reflective liquid crystal element 100, and the light reflected by the liquid crystal element 100 becomes counterclockwise circular or elliptically polarized light.

In this case, the phase difference in the second retardation plate 54b is made larger than that in the first retardation plate 53a. That is, when the liquid crystal molecules are provided with an orientation of +45 degrees and a tilt angle of 80 degrees, λ / 4 is 137.5 nm when the center wavelength of incident light is 550 nm. The required retardation in the two phase difference plate 52b is from λ / 4 to the retardation of 0.1 × λ / 4 generated in the reflective liquid crystal element.
150 nm, which is calculated by adding

(Sixth Embodiment) The projection type liquid crystal display device according to the sixth embodiment is also a modification of the projection type liquid crystal display device according to the second embodiment.

Similar to the reflective liquid crystal display devices according to the second to fifth embodiments, the retardation of the first retardation plate and the second retardation plate is set in consideration of the retardation caused by the reflective liquid crystal element. It has an optimized configuration.

FIG. 8 shows the structure of a projection type liquid crystal display device according to the fifth embodiment. A basic first polarizing plate 65a,
The arrangement of the first retardation plate 55a, the reflective liquid crystal element 100, the second retardation plate 55b, and the second polarizing plate 65b is almost the same as that of the projection type liquid crystal display device according to the second embodiment. The arrangement of the plate 65a and the second polarizing plate 65b is rotated while maintaining the relationship in which the polarization axes are orthogonal to each other. Thus, if the two polarizing plates have a relationship in which the polarization axes are orthogonal (crossed Nicols), the two polarizing plates take a free angle regardless of the orientation of the liquid crystal molecules of the retardation plate and the reflective liquid crystal element. Is also good.

Orientation of liquid crystal molecules of the reflective liquid crystal element 100,
For the arrangement of the first retardation plate 55a and the second retardation plate 55b and each retardation, the same conditions as in the second embodiment can be used.

(Seventh Embodiment) The projection type liquid crystal display device according to the seventh embodiment is also a modification of the projection type liquid crystal display device according to the second embodiment.

FIG. 9 shows the structure of a projection type liquid crystal display device according to the seventh embodiment. Similar to the reflective liquid crystal display devices according to the second to fifth embodiments, the retardations of the first retardation plate and the second retardation plate are optimized in consideration of the retardation caused by the reflective liquid crystal element. Although it has a configuration, the feature here is that a transmissive liquid crystal cell 80 is used instead of the second retardation plate. The other components, that is, the first polarizing plate 66a, the first retardation plate 56a, the reflective liquid crystal element 100, and the second polarizing plate 66b are arranged in the same manner as in the second embodiment. The configuration is not limited to this, and may have the same configuration as the third to sixth embodiments.

The transmissive liquid crystal cell 80 itself can be used as a variable retardation plate. Therefore, the first
Alternatively, if any of the second retardation plates is replaced with a transmissive liquid crystal cell, the retardation can be freely adjusted by the applied voltage applied between the liquid crystal layers.

For example, in the case of the projection type liquid crystal display device shown in FIG. 9, the plane orientations of the liquid crystal molecules in the liquid crystal cell 80 are aligned in the direction of −45 degrees, and the upper and lower substrates are arranged in opposite parallel orientations, that is, antiparallel. It should be arranged so that If a predetermined voltage is applied between the transparent electrodes (not shown) of the liquid crystal cell 80, the orientation of the liquid crystal molecules changes according to the electric field, and the required phase difference is obtained.

It is also possible to make the liquid crystal molecule orientation of the liquid crystal cell 80 correspond to the pixel of the reflection type liquid crystal element 100 and perform the retardation adjustment according to the state of the liquid crystal molecule for each pixel.

(Relationship between Tilt Angle and Phase Difference of Retardation Plate) FIG. 10 shows tilt angles given to liquid crystal molecules corresponding to the second to seventh embodiments, preferred first retardation plate and first retardation plate. It is a graph which calculated | required the relationship with the difference of the retardation of 2 phase plates by simulation. As shown in the graph,
When the liquid crystal molecules are perfectly vertically (90 degrees) aligned, the retardation difference between the first retardation plate and the second retardation plate is 0, that is, the retardation of the first retardation plate is λ.
/ 4, the retardation of the second retardation plate is λ / 4, and the optical axes may be arranged to be orthogonal to each other. However, when the liquid crystal molecules have a tilt angle, the reflection type liquid crystal generated by the tilt angle. The retardation difference between the first retardation plate and the second retardation plate is determined in consideration of the retardation of the substrate.

For example, the difference in retardation is about 0.03 · λ / 4 when the tilt angle of the liquid crystal molecule is 85 degrees, and about 0.1 · λ / 4 when the tilt angle of the liquid crystal molecule is 80 degrees. ,
When the tilt angle of the liquid crystal molecules is 75 degrees, it is about 0.23.
・ It becomes λ / 4. It should be noted that the retardation of the second retardation plate takes into consideration the plane azimuth angle of the liquid crystal molecules, and in the case where the optical axis of the first retardation plate and the plane orientation of the liquid crystal molecules are orthogonal,
When the retardation of the retardation plate is made smaller by the difference of the retardation, and the optical axis of the first retardation plate and the plane orientation of the liquid crystal molecules are substantially parallel to each other, the retardation of the second retardation plate is set to the above value. It is better to increase the difference in phase difference.

The projection type liquid crystal display device of the present invention has been described above according to the embodiment. However, the projection type liquid crystal display device of the present invention is not limited to the description of the above embodiment. It is obvious to those skilled in the art that various modifications and improvements can be made.

For example, in the first to seventh embodiments, vertically aligned liquid crystal molecules exhibiting a negative dielectric anisotropy are used, and a normally displayed black display is obtained in the initial state where no electric field is applied to the pixel. The black mode was explained. However, the occurrence of disclination lines is likely to occur when the liquid crystal molecules are in the vertical alignment mode with respect to the substrate surface, so that not only vertical alignment type liquid crystal molecules but also liquid crystal molecules with positive dielectric anisotropy are used. Also, the configuration according to the present embodiment is applied to an NW (Normally White) type liquid crystal display device that exhibits a vertical alignment mode when an electric field is applied and displays black, and the disclination is similarly performed. The effect of suppressing line generation can be obtained.

Further, in the above-described first to seventh embodiments, a diagram in which a polarizing plate and a retardation plate are arranged at almost the same height so that the incident light is incident from the right or left of the reflective liquid crystal element. However, the structure may be such that at least the incident light optical path and the outgoing light optical path are independently obtained. Therefore, a polarizing plate or a retardation plate may be arranged so that light is obliquely input to the reflective liquid crystal element from the lower side and reflected light is obliquely output to the upper side.

Further, in the above-mentioned first to seventh embodiments, the polarizing plate is used as the means for obtaining the linearly polarized light from the incident light, but it is also possible to use a beam splitter or a wire grid. .

[0079]

As described above, according to the liquid crystal display device of the present invention, it is possible to reduce the occurrence of disclination lines on an image, so that a good image can be obtained even when the image has a higher resolution. The characteristics can be obtained. Therefore,
A liquid crystal display device can be provided that is suitable for use in a liquid crystal display device that requires a high pixel density for magnified projection.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a projection type liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a partial perspective view of the projection type liquid crystal display device according to the first embodiment of the present invention and showing the relationship between incident light and output light.

FIG. 3 compares an image on the screen and an output value obtained by the projection type liquid crystal display device according to the first embodiment of the present invention with an image on the screen and an output value obtained by the conventional projection type liquid crystal display device. FIG.

FIG. 4 is a partial perspective view of a projection type liquid crystal display device according to a second embodiment of the present invention and showing the relationship between incident light and output light.

FIG. 5 is a partial perspective view of a projection type liquid crystal display device according to a third embodiment of the present invention and showing the relationship between incident light and output light.

FIG. 6 is a partial perspective view of a projection type liquid crystal display device according to a fourth embodiment of the present invention and showing the relationship between incident light and output light.

FIG. 7 is a partial perspective view of a projection type liquid crystal display device according to a fifth embodiment of the present invention and showing the relationship between incident light and output light.

FIG. 8 is a partial perspective view of a projection type liquid crystal display device according to a sixth embodiment of the present invention and showing the relationship between incident light and output light.

FIG. 9 is a partial perspective view of a projection type liquid crystal display device according to a seventh embodiment of the present invention and showing the relationship between incident light and output light.

FIG. 10 is a graph showing the relationship between the retardation difference of the first and second retardation plates and the tilt angle of liquid crystal molecules in the projection type liquid crystal display device according to the second to seventh embodiments of the present invention. .

FIG. 11 is a schematic configuration diagram of a conventional projection type liquid crystal display device.

FIG. 12 is a diagram showing an alignment state of liquid crystal molecules.

[Explanation of symbols]

10 Transparent substrate 20 Liquid crystal layer 30 reflective substrate 50a to 56a First retardation plate 50b to 56b Second retardation plate 60a-66a 1st polarizing plate 60b to 66b Second polarizing plate 70 Projection lens 100 reflective liquid crystal element

Continued front page    F-term (reference) 2H049 BA02 BA03 BA04 BA06 BA07                       BB03 BC22                 2H091 FA08X FA08Z FA11X FA11Z                       FA14Z FA26X GA01 GA02                       GA06 GA11 KA02 LA30 MA07

Claims (2)

[Claims] 1. A liquid crystal molecule having a transparent substrate and a drive circuit and a reflective electrode, the substrates being arranged so that their electrode surfaces face each other, and having a vertical alignment mode between the two substrates. A reflective liquid crystal element sandwiching a liquid crystal layer containing a liquid crystal layer, first means for providing linearly polarized light from the incident light provided on the optical path of the incident light to the reflective liquid crystal element, and the first means Second means for converting linearly polarized light into circularly polarized light or elliptically polarized light; and provided on the optical path of reflected light from the reflective liquid crystal element,
Third means for converting circularly polarized light or elliptically polarized light into substantially linearly polarized light, and the optical axis of the linearly polarized light obtained by the first means and 9
And a fourth means for extracting linearly polarized light having polarization axes different by 0 degrees. 2. The second means is a first retardation plate, the third means is a second retardation plate, and the phase difference between the first retardation plate and the second retardation plate is , The phase difference generated in the reflective liquid crystal element is different, and when the central wavelength of incident light is λ, the reflective liquid crystal element is calculated from the sum of retardations of the first retardation plate and the second retardation plate. The liquid crystal display device according to claim 1, wherein the value obtained by subtracting the retardation generated in (1) is in the range of 0.8λ / 2 to 1.2λ / 2.