JP2006091608A - Liquid crystal display device and projector device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem in which liquid crystal is not aligned since rubbing is not carried out sufficiently in some region owing to unevenness of a liquid crystal cell surface according as a pixel pitch decreases with the size of one pixel as a result of higher fineness when a cell gap is made partially narrow by forming a projection only between pixels in an effective pixel region. <P>SOLUTION: The retardation Δn×d and twist angle T(°) of liquid crystal meet conditions of (4.125×T+16.5)×0.95<Δn×d<(4.125×T+16.5)×1.05 and 80°<T<90° under liquid crystal conditions wherein the retardation Δn×d of the liquid crystal at a 550 nm wavelength in actual use is 300 to 450 nm, the wavelength is 400 to 700 nm, and wavelength dispersion of Δn is 0.9 to 1.3. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquid crystal display device and a projector device using the liquid crystal display device (liquid crystal panel) as a light valve.

  In recent years, development of projector devices (projection display devices) using light valves such as LCD (Liquid Crystal Display), DMD (Digital Micromirror Device), and LCOS (Liquid Crystal On Silicon) has been active. In these projector apparatuses, it is considered that higher brightness, higher definition, higher image quality, and lower prices will continue in the future. These are closely related to each other, and each problem must be solved together. For example, low prices and downsizing inevitably involve high definition along with narrowing and miniaturization of pixels even if the display device has the same format. While maintaining the utilization efficiency (high luminance), the image quality must be improved to the same level as before.

  Regarding high definition, at present, in the transmissive LCD light valve (liquid crystal display device) using a TFT (Thin Film Transistor) as an active element of a pixel, the main market has a pixel pitch of 18 to 14 μm □. In the future, it is considered that the pixel pitch will increase to 14 μm □ or less and about 10 μm □.

  At present, TN (Twisted Nematic) type liquid crystal is the mainstream in liquid crystal projector devices using a liquid crystal display device (liquid crystal panel) as a light valve. In the liquid crystal projector device using this TN type liquid crystal, black is displayed when a voltage is applied to the liquid crystal cell (during black display) because of the pretilt component of the liquid crystal molecules at the interface between the liquid crystal layer and the substrate of the liquid crystal display device. There is a problem that brightness is generated in a portion to be formed, black is not displayed as a complete black, so-called black floating phenomenon occurs, and contrast is lowered.

  As a countermeasure, for example, a retardation film having an optical axis inclined with respect to the interface, such as a wide viewing angle film made of discotic liquid crystal (for example, “WV film” (trade name) manufactured by Fuji Photo Film Co., Ltd.) By using two sheets, the pretilt component is optically compensated to realize high contrast. However, due to the lateral electric field caused by the voltage difference between adjacent pixels due to the difference in pixel potential polarity, reverse tilt domain (RTD), which is part of light leakage, occurs, resulting in narrow pixel pitch (high definition) In the present situation, the influence of the transverse electric field is becoming more remarkable.

  As a method of suppressing the reverse tilt domain, for example, there is a method of increasing the vertical electric field by narrowing the gap of the liquid crystal cell. However, if the cell gap is narrowed, the transmittance of the high wavelength region (570 to 700 nm) during white display decreases due to the wavelength dependence of the emission spectrum of the light source (for example, a lamp), and the white balance is lost. appear. In order to maintain the white balance by narrowing the cell gap, it is necessary to lower the transmittance in the blue to green wavelength region by providing an ND (Neutral Density) filter. It is not very practical because of the decrease.

  In general, in a liquid crystal projector device, in order to maintain contrast, it is desirable that the peak of contrast is at the center of the viewing angle, so the twist angle of the liquid crystal is set to about 92 ° (for example, Patent Document 1). reference). Therefore, in order to maintain the white balance, generally, retardation of the liquid crystal Δn · d (Δn: refractive index anisotropy (difference in refractive index between major and minor axes of liquid crystal), d: thickness of the liquid crystal cell (cell gap) ) Is about 380 to 410 nm.

  On the other hand, in order to suppress the reverse tilt domain without destroying the white balance, conventionally, for example, convex portions are formed only between pixels in the display effective pixel region, and the thickness of the liquid crystal cell is partially reduced ( By narrowing the cell gap, the vertical electric field is strengthened and the horizontal electric field is relatively weakened to suppress the influence of the horizontal electric field (see, for example, Patent Document 2).

JP 2003-066457 A JP 2001-142414 A

  However, when a convex portion is formed only between pixels in the display effective pixel region and a structure in which the cell gap is partially narrowed is adopted, the size of one pixel is reduced with the increase in definition, and the pixel pitch is increased. When it becomes smaller, a region where the rubbing is not sufficiently performed due to the unevenness on the surface of the liquid crystal cell is formed, so that there is a problem that the liquid crystal is not aligned.

  The present invention has been made in view of the above problems, and its object is to align the liquid crystal and maintain the white balance while maintaining the white balance even when the pixel pitch is reduced. An object of the present invention is to provide a liquid crystal display device that can be suppressed and a projector device that uses the liquid crystal display device as a light valve.

The liquid crystal display device according to the present invention has a liquid crystal panel in which pixels including liquid crystal cells are arranged, and a liquid crystal retardation Δn · d (Δn: refractive index anisotropy, d (nm) at a wavelength of 550 nm in actual use. ): The thickness of the liquid crystal cell) is 300 nm to 450 nm, the wavelength is 400 nm to 700 nm and the wavelength dispersion of the refractive index anisotropy Δn is 0.9 to 1.3. Liquid crystal retardation Δn · d and twist angle T (°)
(4.125 · T + 16.5) × 0.95 <Δn · d <(4.125 · T + 16.5) × 1.05, 80 ° <T <90 °
The structure that satisfies the following conditions is adopted. This liquid crystal display device is used as a light valve in a projector device.

  Here, the chromatic dispersion of the refractive index anisotropy Δn means that refraction in the visible light wavelength region shows wavelength dependency. The chromatic dispersion of the refractive index anisotropy Δn is expressed as Δn1 / when the refractive index anisotropy Δn when the wavelength is 400 nm or more and 700 nm or less is Δn1, and the refractive index anisotropy Δn when the wavelength is 550 nm is Δn2. It is given by Δn2.

  In the liquid crystal display device having the above-described configuration or the projector device using the liquid crystal display device (liquid crystal panel) as a light valve, if the retardation Δn · d of the liquid crystal is reduced, specifically set within the above range, the vertical electric field is Strengthens and suppresses reverse tilt domain. However, if the retardation Δn · d of the liquid crystal is decreased, it is expected that the white balance will be lost. Therefore, if the twist angle T of the liquid crystal is set to be smaller than 92 °, specifically set to an angle of 80 ° <T <90 ° and the retardation Δn · d of the liquid crystal is reduced, the reverse is performed while maintaining the white balance. -Tilt domain (part of light leakage) can be suppressed.

  According to the present invention, by optimizing both the retardation Δn · d of the liquid crystal and the twist angle T of the liquid crystal, the reverse tilt domain can be suppressed while maintaining the white balance, and the display effective pixel region In FIG. 5, since it is not necessary to partially narrow the cell gap, the liquid crystal can be aligned even if the pixel pitch is reduced.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a configuration diagram showing an outline of an optical system of a projector apparatus to which the present invention is applied, for example, a three-plate liquid crystal projector apparatus.

  In FIG. 1, white light emitted from a light source 11 such as a white lamp is converted from P-polarized light to S-polarized light by a polarization conversion element 12, and then the illumination is made uniform by a fly-eye lens 13 to be applied to a dichroic mirror 14. Incident. Then, only a specific color component, for example, an R (red) light component is transmitted through the dichroic mirror 14, and the remaining color light components are reflected by the dichroic mirror 14. The R light component transmitted through the dichroic mirror 14 is changed in optical path by the mirror 15 and then enters the R liquid crystal panel 17R through the lens 16R.

  For the light component reflected by the dichroic mirror 14, for example, a G (green) light component is reflected by the dichroic mirror 18, and a B (blue) light component passes through the dichroic mirror 18. The G light component reflected by the dichroic mirror 18 enters the G liquid crystal panel 17G through the lens 16G. The B light component transmitted through the dichroic mirror 18 passes through the lens 19 and is then changed in the optical path by the mirror 20, and further passes through the lens 21 and is then changed in the optical path by the mirror 22, and enters the B liquid crystal panel 17B through the lens 16B. .

  Although not shown in FIG. 1, polarizing plates are arranged on the incident side and the emission side of the liquid crystal panels 17R, 17G, and 17B, respectively. As is well known, a normally white mode can be set by installing a pair of polarizing plates on the incident side and the outgoing side so that the polarization directions are perpendicular to each other (crossed Nicols), and the polarization directions are parallel to each other (parallel Nicols) You can set the normally black mode. The R, G, and B light components that have passed through the liquid crystal panels 17R, 17G, and 17B are combined by the dichroic prism 23. Then, the light synthesized by the dichroic prism 23 enters the projection lens 24 and is projected (projected) onto the screen (not shown) by the projection lens 24.

  Next, specific examples of the liquid crystal panels 17R, 17G, and 17B used in the liquid crystal projector apparatus having the above configuration will be described.

Example 1
First, liquid crystal retardation Δn · d, which is the product of refractive index anisotropy Δn of liquid crystal and cell gap d, and twist angle T (°) during white display (Vsig = 0 V; Vsig is a voltage applied to the liquid crystal cell) The relationship will be described.

  FIG. 2 is a diagram illustrating the wavelength dependence of the refractive index anisotropy Δn of the liquid crystal in the liquid crystal panels 17R, 17G, and 17B according to the first embodiment. Here, the chromatic dispersion (Δn1 / Δn2) of the refractive index anisotropy Δn is the refractive index anisotropy at each wavelength (400 to 700 nm) when the refractive index anisotropy Δn2 at the wavelength of 550 nm is Δn2 = 1. It is a relative ratio of Δn1. The wavelength dispersion Δn1 / Δn2 is higher than 1 in the low wavelength region (400 to 500 nm), and the wavelength dispersion Δn1 / Δn2 is lower than 1 in the high wavelength region (600 to 700 nm). This tendency is a general property of liquid crystal materials.

  In the liquid crystal projector device, considering the emission spectrum of the lamp and white balance during white display, the retardation Δn · d of the liquid crystal is usually 395 ± 5% at a wavelength of 550 nm and a twist angle of 92 ° of the liquid crystal.

  FIG. 3 shows the spectral transmittance according to the combination of the retardation Δn · d of the liquid crystal and the twist angle. Here, the retardation Δn · d of the liquid crystal is 396 nm, the twist angle T of the liquid crystal is T = 92 °, the cell gap d is narrowed, the retardation Δn · d is 380 nm and 364 nm, and the twist angle T of the liquid crystal is 84 °. , 88 °, and 92 ° are shown.

  From FIG. 3, it can be seen that the cell gap d can be reduced by reducing the twist angle T without destroying the white balance during white display. (Δn · d (nm), twist angle (°)) = (396, 92), (380, 88), (364, 84), it can be considered that the spectral transmittance is substantially equal.

That is, the retardation Δn · d of the liquid crystal and the twist angle T are
Δn · d = 4.125 · T + 16.5
If the above relationship is satisfied, it can be considered that the white balance is substantially the same and a narrow cell gap is possible.

  FIG. 4 shows the relationship between the twist angle T of the liquid crystal and the retardation Δn · d without breaking the white balance. From FIG. 4, if the twist angle T and retardation Δn · d of the liquid crystal are set within a range of ± 5% (broken line) with respect to Δn · d = 4.125 · T + 16.5 (solid line), the white balance It can be seen that a narrow cell gap can be achieved without destroying.

  Conventionally, the liquid crystal twist angle T is set to about 92 ° and the liquid crystal retardation Δn · d is about 395 nm. In other words, it was designed in the range indicated by hatching in FIG. When white balance is taken into consideration, in the present invention, it is possible to set Δn · d = 370 nm or less by setting the twist angle to 90 ° or less. In other words, it is possible to design even the area shown by hatching in FIG.

  By the way, in a liquid crystal projector apparatus, generally, when the peak of contrast is brought to the center of the viewing angle (polar angle: 0 °), the contrast becomes high. Therefore, the twist angle T of the liquid crystal is set to about 92 °, and the contrast peak is set to the center of the viewing angle. The reason why the twist angle T of the liquid crystal is slightly larger (2 °) than 90 ° is that the twist angle component due to the chiral pitch of the liquid crystal is taken into consideration so that the effective twist angle becomes 90 °.

  When the twist angle T of the liquid crystal is made smaller than 92 °, the contrast peak is shifted from the center of the viewing angle, so that the contrast is expected to decrease. In view of this point, Example 2 described below is made.

(Example 2)
FIG. 5 is a configuration diagram illustrating a configuration of a main part of the optical system of the three-plate liquid crystal projector apparatus according to the second embodiment.

  In the three-plate liquid crystal projector device according to the second embodiment, between the two polarizing plates 33 (33R, 33G, 33B) and 34 (34R, 34G, 34B) on the light incident side and the light emitting side of the liquid crystal panel 17R, Similarly, two optical compensation films 31R and 32R whose optical axes are inclined with respect to the main surface of the liquid crystal panel 17R are arranged on the light incident side and the light emission side of the liquid crystal panel 17G. Is configured such that two optical compensation films 31B and 32B are arranged on the light incident side and the light emitting side of the liquid crystal panel 17B.

  Then, by adjusting the angle between the optical axes of the two optical compensation films 31 (31R, 31G, 31B) and 32 (32R, 32G, 32B) so as to correspond to the twist angle of the liquid crystal, the peak of contrast is obtained. To the center of the viewing angle. That is, by arranging the two optical compensation films 31 and 32 in the optical path between the two polarizing plates 33 and 34 before and after the liquid crystal panels 17R, 17G, and 17B, the optical tilt compensation of the liquid crystal is optically compensated. By optimizing the angle between the optical axes between the two optical compensation films 31 and 32, optical compensation is performed for the deviation of the contrast peak from the center of the viewing angle caused by making the twist angle T of the liquid crystal smaller than 92 °. Will do.

  FIG. 6 shows the viewing angle characteristics with and without the optical compensation film when the twist angle of the liquid crystal is changed (twist angles: 92 °, 88 °, 84 °). At this time, the applied voltage Vsig to the liquid crystal cell is set to Vsig = 5V. In FIG. 6, the thick solid line on the inside indicates the case where the contrast ratio is 2000: 1, the one-dot chain line indicates the case where the contrast ratio is 1000: 1, the broken line indicates the case where the contrast ratio is 500: 1, and the two-dot chain line indicates the contrast ratio. = 200: 1, the thin outer solid line indicates the case where the contrast ratio is 100: 1.

  Here, as the optical compensation films 31 and 32, for example, “WV film” (trade name) manufactured by Fuji Photo Film Co., Ltd. is used to obtain viewing angle characteristics up to 30 ° polar angle. The viewing angle characteristic with the optical compensation film is such that the angle of the optical axis of the two WV films is changed so that the contrast peak becomes the center of the viewing angle. Specifically, the angle between the axes of the WV film is 90 ° with respect to the twist angle of the liquid crystal: 92 °, and the angle between the axes of the WV film is 86 ° with respect to the twist angle of the liquid crystal: 88 °. Angle: The angle between the axes of the WV film is 82 ° with respect to 84 °.

  As described above, even if the twist angle of the liquid crystal is smaller than 92 °, the angle between the axes of the two optical compensation films 31 and 32 is adjusted so as to correspond to the twist angle of the liquid crystal. As is apparent from the viewing angle characteristic diagram, it can be seen that the peak of contrast can be brought to the center of the viewing angle.

  Here, the “WV film” manufactured by Fuji Photo Film Co., Ltd. has been described as an example of the optical compensation film. However, the present invention is not limited to this, and the two optical compensation films 31 and 32 to be used are average. There is no particular problem as long as the optical axis is inclined with respect to the liquid crystal interface. For example, quartz, sapphire, or “NH film” (trade name) manufactured by Nippon Oil Corporation may be used.

  Next, a simulation result about a change in light leakage around the pixel when the twist angle is changed will be described. Here, the retardation of the liquid crystal is Δn · d = 364, and the twist angle of the liquid crystal and the inter-axis angle of the WV film are (the twist angle of the liquid crystal and the inter-axis angle of the WV film) = (92 °, 90 °), ( 88 [deg.], And (84 [deg.], 82 [deg.]), The pixel periphery was simulated.

  The simulation result at that time is shown in FIG. At this time, the rubbing on the pixel electrode side is performed from the minus direction to the plus direction. From this simulation result, it can be seen that as the twist angle is decreased, light leakage around the negative pixel increases. From this result, it is expected that if the twist angle is reduced, light leakage on the negative side around the gate line (scanning line) increases, and the reverse contrast may be lowered. That is, it is expected that there is a lower limit of the twist angle.

  In the second embodiment, the two optical compensation films 31 (31R, 31G, 31B) and 32 (32R, 32G, 32B) are arranged on the light incident side and the light emitting side of the liquid crystal panels 17R, 17G, 17G. However, the present invention is not limited to this, and the two optical compensation films 31 and 32 are both placed between the two polarizing plates 33 and 34, or only on the light incident side of the liquid crystal panels 17R, 17G, and 17G. It is also possible to dispose only on the emission side, and it is possible to obtain the same operational effects as when arranged on the light incident side and the light emission side.

As described above, the chromatic dispersion of the refractive index anisotropy Δn is 0 when the retardation Δn · d of the liquid crystal at a wavelength of 550 nm in actual use is 300 nm to 450 nm and the wavelength is 400 nm to 700 nm. In a liquid crystal condition of 0.9 to 1.3, the retardation Δn · d of the liquid crystal is made small and the twist angle of the liquid crystal is made small. Specifically, (4.125 · T + 16.5) × 0.95 < Δn · d <(4.125 · T + 16.5) × 1.05, 80 ° <T <90 °
By satisfying these conditions, light leakage around the pixel can be suppressed without changing the white balance during white display.

  In addition, the optical axis between the two optical compensation films 31 and 32 is optically compensated for the pretilt component at the interface of the liquid crystal, corresponding to the deviation of the contrast peak from the center of the viewing angle caused by reducing the twist angle of the liquid crystal. By optimizing the angle, it is possible to optically compensate for the deviation of the contrast peak from the viewing angle center.

  Next, measurement examples 1 and 2 in the case where a liquid crystal panel is actually manufactured and the above-described effects are confirmed will be described.

(Measurement Example 1)
In the liquid crystal panels 17R, 17G, and 17B in which the size of one pixel is 12.5 μm, the liquid crystal retardation Δn · d and the twist angle are set as shown in the condition table shown in FIG. 8, and a three-plate liquid crystal projector device (FIG. 1). And the panel transmittance and contrast ratio (Vsig = 5V for black display) when white display (Vsig = 0V) is measured.

  As a method for measuring the retardation Δn · d and twist angle of the liquid crystal, a method using a Stokes parameter method (see, for example, Japanese Patent Laid-Open No. 11-83730), a rotating analyzer method, or the like is known. Here, the retardation Δn · d and twist angle of the liquid crystal are measured using an LCD analyzer (manufactured by Meiryo Technica Co., Ltd.) using the Stokes parameter method. The measurement results of the retardation Δn · d and the twist angle at that time are shown in FIG. 9, the panel transmittance ratio of each of the R, G, and B lights is shown in FIG. 10, and the panel contrast of the G light is shown in FIG.

  From this measurement result, the panel transmittance of the liquid crystal twist angle of 88 ° when Δn · d = 380 nm and the twist angle of liquid crystal of 84 ° when Δn · d = 364 nm is the panel transmittance when the twist angle is 92 ° and Δn · d = 396 nm. On the other hand, in all of the R light, G light, and B light, the panel transmittance ratio is ± 2%, and it can be seen that the white balance is not lost. It can also be seen that the contrast is increased by reducing the retardation Δn · d of the liquid crystal.

(Measurement example 2)
Next, in order to check the lower limit value of the twist angle of the liquid crystal, in the liquid crystal panels 17R, 17G, and 17B in which the size of one pixel is 12.5 μm, the retardation Δn · d of the liquid crystal and the twist angle are shown in a condition table shown in FIG. Then, the image is projected using a three-plate liquid crystal projector (FIG. 1), and the contrast ratio is measured. The result of multiple regression analysis of the measured contrast ratio is shown in FIG.

  From this measurement result, it can be seen that when the twist angle of the liquid crystal is 80 ° or more, the contrast increases as the retardation Δn · d of the liquid crystal is decreased. On the other hand, it can be seen that when the twist angle of the liquid crystal is 80 ° or less, the contrast decreases. As a result, the twist angle of the liquid crystal is desirably 80 ° or more.

  In the above embodiment, in Example 2, the optical compensation films 31 and 32 are provided to correct the deviation of the contrast peak from the viewing angle center caused by the liquid crystal twist angle T being smaller than 92 °. However, the optical compensation films 31 and 32 are not necessarily essential constituent elements, and it is possible to correct the deviation of the contrast peak from the viewing angle center by adjusting the optical system of the liquid crystal projector apparatus.

It is a block diagram which shows the outline of the optical system of the 3 plate-type liquid crystal projector device to which this invention is applied. FIG. 4 is a diagram showing the wavelength dependence of the refractive index anisotropy Δn of the liquid crystal in the liquid crystal panel according to Example 1. It is a figure which shows the spectral transmittance by the combination of retardation (DELTA) n * d of a liquid crystal, and a twist angle. It is a figure which shows the relationship between the twist angle | corner T of liquid crystal and retardation (DELTA) n * d which does not destroy a white balance. 6 is a configuration diagram illustrating a configuration of a main part of an optical system according to Example 2. FIG. It is a figure which shows the viewing angle characteristic in the case with and without an optical compensation film when changing the twist angle of a liquid crystal. It is a figure which shows the simulation result about the change of the light leakage of the pixel periphery when changing a twist angle | corner. FIG. 6 is a diagram showing a condition table for liquid crystal retardation Δn · d and twist angle in Measurement Example 1; It is a figure which shows the measurement result of retardation (DELTA) n * d and twist angle in each conditions. It is a figure which shows the panel transmittance | permeability ratio of R, G, B each light. It is a figure which shows the panel contrast of G light. FIG. 10 is a diagram showing a condition table for liquid crystal retardation Δn · d and twist angle in Measurement Example 2. It is a figure which shows the result of having performed the multiple regression analysis of contrast ratio.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Light source, 12 ... Polarization conversion element, 14, 18 ... Dichroic mirror, 17R, 17G, 17B ... Liquid crystal panel, 23 ... Dichroic prism, 24 ... Projection lens, 31 (31R, 31G, 31B), 32 (32R, 32G) 32B) Optical compensation film,

Claims (4)

It has a liquid crystal panel in which pixels including a liquid crystal cell are arranged, and has a retardation Δn · d (Δn: refractive index anisotropy, d (nm): thickness of the liquid crystal cell) of liquid crystal at a wavelength of 550 nm in actual use. In the liquid crystal conditions where the wavelength dispersion of the refractive index anisotropy Δn is 0.9 or more and 1.3 or less in a range of 300 nm to 450 nm and a wavelength of 400 nm to 700 nm.
Liquid crystal retardation Δn · d and twist angle T (°)
(4.125 · T + 16.5) × 0.95 <Δn · d <(4.125 · T + 16.5) × 1.05
80 ° <T <90 °
A liquid crystal display device characterized by satisfying the following conditions. 2. The optical compensation film according to claim 1, wherein the optical compensation film is disposed on at least one of a light incident side and a light emitting side of the liquid crystal panel, and an optical axis is inclined with respect to a main surface of the liquid crystal panel. The liquid crystal display device described. A projector device using a liquid crystal panel in which pixels including liquid crystal cells are arranged as a light valve,
The liquid crystal panel is
Liquid crystal retardation Δn · d (Δn: refractive index anisotropy, d (nm): liquid crystal cell thickness) at a wavelength of 550 nm in actual use is in the range of 300 nm to 450 nm and the wavelength is in the range of 400 nm to 700 nm. In a liquid crystal condition where the wavelength dispersion of the refractive index anisotropy Δn is 0.9 or more and 1.3 or less,
Liquid crystal retardation Δn · d and twist angle T (°)
(4.125 · T + 16.5) × 0.95 <Δn · d <(4.125 · T + 16.5) × 1.05
80 ° <T <90 °
A projector device characterized by satisfying the following conditions. The optical compensation film is provided on at least one of a light incident side and a light outgoing side of the liquid crystal panel, and has an optical axis inclined with respect to a main surface of the liquid crystal panel. The projector apparatus as described.

Images