JP2005062787A - Liquid crystal display device and projection display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize an excellent picture display by reducing deterioration of the optical characteristics of a quarter-wave plate in a liquid crystal display device used for a projection display device. <P>SOLUTION: The liquid crystal display device used for the projection display device comprises a transmissive liquid crystal panel 11, comprising a liquid crystal layer for displaying information interposed between a pair of transparent insulating substrates placed opposite to each other, a pair of optical retardation plates 13a, 13b disposed so as to pinch the liquid crystal panel 11 and consisting of a birefringent crystal having the function of a quarter-wave retardation and a pair of polarizing plates 14a, 14b disposed so as to pinch the pair of optical retardation plates 13a, 13b. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a liquid crystal display device and a projection display device using the liquid crystal display device.

In recent years, a so-called projector type projection display that realizes large-screen image display by selectively transmitting light emitted from a light source using a liquid crystal display device and projecting the transmitted light on a screen. The device is being used.
As a liquid crystal display device used for a projection display device, a liquid crystal display device including a transmissive liquid crystal panel in which a liquid crystal layer for displaying information is sandwiched between a pair of opposed transparent insulating substrates is known. Among them, a so-called VA (Vertically Aligned) type liquid crystal layer including liquid crystal molecules that are vertically aligned in a state where no voltage is applied has been devised and put into practical use. However, when such a VA liquid crystal display device is used, a quarter-wave plate is used as a countermeasure for disclination in the vertical alignment mode, and the alignment direction of the liquid crystal molecules is 45 ° with respect to the polarization axis of the polarizing portion. It has been proposed to prevent a decrease in maximum light transmittance that occurs when a corner is not formed (see, for example, Patent Document 1). The quarter wave plate refers to a wave plate having a function of causing a quarter wavelength phase difference in incident light. When the linearly polarized incident light is incident on the quarter-wave plate at an angle of θ = + 45 ° with respect to the optical axis direction of the quarter-wave plate, the emitted light is a clockwise circle. It becomes polarized light. Further, when the vibration direction of the incident light and the optical axis direction of the quarter wavelength plate form an angle of θ = −45 °, it becomes counterclockwise circularly polarized light. Therefore, when a VA liquid crystal display device is used for a projection display device, the projection display device has an incident side polarizing plate and a quarter wavelength for converting incident light into circularly polarized light in the order of the optical path from the light source. A plate, a transmissive liquid crystal panel, a quarter-wave plate having the same design as the incident side for converting light emitted from the liquid crystal panel into linearly polarized light, and an output side polarizing plate.
Of these, an organic material retardation film is usually used as the quarter-wave plate. Specific examples include films obtained by stretching PC (polycarbonate), PVA (polyvinyl alcohol), PS (polysulfone), and the like.

JP 2001-318371 A

  However, when an organic material-based retardation film as described above is used as a ¼ wavelength plate, the retardation film generates heat when light is transmitted through the retardation film. There exists a possibility that the optical characteristic in a film may deteriorate. In particular, in a projection display device, the intensity of light emitted from a light source is high, and the intensity (luminance) of light transmitted through a quarter-wave plate or the like is considerably high. Probability is high.

  Moreover, it cannot be said that the in-plane uniformity of refractive index anisotropy is necessarily good in the organic material type retardation film as described above. Therefore, when an organic material retardation film is used as the quarter wavelength plate, the retardation of the quarter wavelength plate arranged in a state perpendicular to the top and bottom of the liquid crystal display device is in-plane and on the incident side and the emission side. If it is not uniform or deviates from the orthogonal state, the light incident on the liquid crystal panel through the polarizing plate on the incident side partially becomes elliptically polarized light, or the light emitted from the liquid crystal panel is converted into linearly polarized light. There is a possibility that a part of the emitted light becomes slightly elliptically polarized light. This leads to the fact that the output side polarizing plate cannot completely cut the elliptically polarized light, so that the transmittance does not become zero even in a liquid crystal panel in a state where no voltage is applied, and on the display image by the projection display device. Should be avoided because it causes the occurrence of black float.

  Therefore, in order to solve the above-described problems in the prior art, the present invention realizes a good image display by reducing the deterioration of the optical characteristics of the quarter-wave plate in the liquid crystal display device used in the projection display device. An object of the present invention is to provide a liquid crystal display device and a projection display device that can be used.

  The present invention provides a liquid crystal display device devised to achieve the above object, a transmissive liquid crystal panel in which a liquid crystal layer for displaying information is sandwiched between a pair of opposed transparent insulating substrates, and the liquid crystal A pair of retardation plates made of a birefringent crystal having a quarter-wave phase difference function, and a pair of polarizing plates arranged to sandwich the pair of retardation plates; It is characterized by providing.

  The present invention also provides a transmissive liquid crystal panel in which a liquid crystal layer for displaying information is sandwiched between a pair of opposed transparent insulating substrates, in a projection display device devised to achieve the above object. A pair of retardation plates made of a birefringent crystal having a quarter-wave phase difference function and a pair of retardation plates arranged to sandwich the pair of retardation plates. A liquid crystal display device including a polarizing plate, a light source that emits light incident on one of the pair of polarizing plates in the liquid crystal display device, and an image projection with light emitted from the other of the pair of polarizing plates in the liquid crystal display device And a projection lens for performing the above.

In the liquid crystal display device configured as described above and the liquid crystal display device included in the projection display device described above, the phase difference plate disposed between the liquid crystal panel and the polarizing plate is a birefringence having a 1/4 wavelength phase difference function. It is formed by sex crystals.
Here, the 1/4 wavelength phase difference function refers to a function that causes a 1/4 wavelength phase difference in incident light. Therefore, if a pair of phase difference plates having a quarter wavelength phase difference function is arranged along an optical path that passes through the liquid crystal panel, the linearly polarized incident light is circularly polarized by the incident side phase difference plate. And converted into linearly polarized light again by the phase difference plate on the output side.
Birefringence means that when light passes, the speed changes according to the vibration direction of the light, that is, the refractive index changes depending on the orientation. A birefringent crystal has such properties. It refers to the crystals that have. Examples of the birefringent crystal include quartz and sapphire, all of which are superior in heat resistance, heat dissipation and light resistance compared to an organic phase retardation film, etc., and have an in-plane refractive index anisotropy. Good uniformity. Other known birefringent crystals include wurtzite, gold olivine, chili nitrate, tourmaline, and cadmium sulfide.
Therefore, if the retardation plate is formed of a birefringent crystal having a 1/4 wavelength phase difference function, the alignment direction in the liquid crystal panel is 45 ° with respect to the polarization axis of the polarizing plate due to the 1/4 wavelength phase difference function. While preventing the decrease of the maximum light transmittance that occurs when the corner is not formed (measures for disclination in the vertical alignment mode), the heat resistance, heat dissipation and light resistance of the birefringent crystal prevents heat generation due to light absorption. It can suppress that an optical characteristic changes with generation | occurrence | production or deterioration. Furthermore, due to the in-plane uniformity of the refractive index anisotropy of the birefringent crystal, it becomes easy to suppress the phase shift, and it is possible to avoid the occurrence of elliptically polarized light or the like in the emitted light.

  According to the liquid crystal display device and the projection display device using the liquid crystal display device of the present invention, the following technical effects can be obtained. That is, in the liquid crystal display device, it is possible to avoid the occurrence of elliptically polarized light or the like in the emitted light while preventing a decrease in the maximum light transmittance, and as a result, it is possible to realize a good image display. In addition, since heat generation, changes in optical characteristics, and the like can be suppressed, the reliability of the liquid crystal display device can be improved even when used in a projection display device with high intensity of transmitted light.

  Hereinafter, a liquid crystal display device and a projection display device according to the present invention will be described with reference to the drawings.

  First, a schematic configuration of the projection display device will be described. FIG. 1 is an explanatory diagram illustrating a schematic configuration example of a projection display device. As shown in the figure, in the projection display device, the light emitted from the light source 1 passes through a filter 2 that cuts infrared rays and ultraviolet rays, and a PS separation synthesizer 3 that converts a non-polarized wave into a polarized wave. The dichroic mirror 6 functions as a color separation means by reflecting only light in a specific wavelength band using the total reflection mirror 4 and the condenser lens 5 as necessary, and separated into RGB color component lights. The liquid crystal display devices 7R, 7G, and 7B are provided corresponding to the respective colors of RGB. Then, after light modulation according to the video signal is performed in each of the liquid crystal display devices 7R, 7G, and 7B, each of the light-modulated color component lights is synthesized by the dichroic prism 8 that functions as a color synthesizing unit, and the projection lens 9 is enlarged and projected onto the screen. With this configuration, the projection display device displays a color image on the screen.

Next, the liquid crystal display devices 7R, 7G, and 7B used in the projection display device configured as described above, that is, the liquid crystal display device according to the present invention will be described. FIG. 2 is an explanatory diagram showing a configuration example of a main part of the liquid crystal display device according to the present invention.
As illustrated, the liquid crystal display device described here includes a transmissive liquid crystal panel 11, a pair of dustproof plates 12a and 12b arranged so as to sandwich the liquid crystal panel 11, and the pair of dustproof plates 12a, A pair of retardation plates 13a and 13b arranged so as to sandwich 12b, and a pair of polarizing plates 14a and 14b arranged so as to sandwich the pair of retardation plates 13a and 13b. That is, the polarizing plate 14a, the phase difference plate 13a, the dustproof plate 12a, the liquid crystal panel 11, the dustproof plate 12b, the phase difference plate 13b, and the polarizing plate 14b sequentially overlap along the optical path from the light source 1 of the projection display device. Become. In addition, as will be described later, the arrangement order of the phase difference plates 13a and 13b and the dustproof plates 12a and 12b may be switched.

  The liquid crystal panel 11 is a VA type in which a liquid crystal layer for displaying information is sandwiched between a pair of opposing transparent insulating substrates, and the liquid crystal layer includes liquid crystal molecules that are vertically aligned in a state in which no voltage is applied. It is. Therefore, in the liquid crystal panel 11, when a voltage is applied between the opposed electrodes, the director alignment direction of the liquid crystal molecules is unidirectional, and the uniaxial birefringence anisotropy is expressed. With such a mechanism, the liquid crystal panel 11 performs light modulation according to the video signal with respect to the incident light from the light source 1 of the projection display device.

The dust-proof plates 12a and 12b prevent the display image from the liquid crystal panel 11 and the focal length of the surface-attached foreign matter of the liquid crystal panel 11 from matching with each other in order to prevent deterioration of the projected image quality due to the foreign matter attached to the surface of the liquid crystal panel 11. Is. For this purpose, the dustproof plates 12a and 12b are made of a transparent plate-like material having a certain thickness, and are disposed between the liquid crystal panel 11 and the pair of polarizing plates 14a and 14b.
An example of the transparent plate-like material forming the dustproof plates 12a and 12b is a glass plate. However, it is also conceivable to use a birefringent crystal that is excellent in heat resistance, heat dissipation and light resistance and has good in-plane uniformity of refractive index anisotropy, as in the later-described retardation plates 13a and 13b. When using a birefringent crystal, the dustproof plates 12a and 12b may be the same or different from the phase difference plates 13a and 13b, and may be formed separately from the phase difference plates 13a and 13b. However, it may be formed integrally with the retardation plates 13a and 13b by the same birefringent crystal as the retardation plates 13a and 13b.

The phase difference plates 13a and 13b are provided as countermeasures for disclination because the liquid crystal panel 11 is of the VA type. That is, the phase difference plates 13a and 13b have a ¼ wavelength phase difference function that is a function of causing a ¼ wavelength phase difference in incident light. By this ¼ wavelength phase difference function, incident light that has been linearly polarized is converted into circularly polarized light by the phase difference plate 13a on the incident side, and converted into linearly polarized light again by the phase difference plate 13b on the output side. become.
The retardation films 13a and 13b are formed of a birefringent crystal having not only a quarter wavelength phase difference function but also a quarter wavelength phase difference function. Birefringence means that when light passes, the speed changes according to the vibration direction of the light, that is, the refractive index changes depending on the orientation. A birefringent crystal is a crystal with such properties. I mean. Examples of such birefringent crystals include quartz and sapphire, all of which are superior in heat resistance, heat dissipation, and light resistance as compared to conventionally used organic material-based retardation films, etc. In-plane uniformity of refractive index anisotropy is good.

  The polarizing plates 14a and 14b are arranged so that their optical axes are orthogonal to each other on the incident side and the emission side. However, since the polarizing plates 14a and 14b are provided with the retardation plates 13a and 13b between the polarizing plates 14a and 14b, the polarizing axis of one polarizing plate 14a and the position where it is disposed on the polarizing plate 14a side. The angle formed by the optical axis of the phase difference plate 13a is 45 °, and the angle formed by the polarization axis of the other polarizing plate 14b and the optical axis of the phase difference plate 13b arranged on the polarizing plate 14b side is also 45 °. It is arranged to be.

  Reflective light that causes stray light at the interface is reduced on each surface of the liquid crystal panel 11, the dustproof plates 12a and 12b, the phase difference plates 13a and 13b, and the polarizing plates 14a and 14b, or at least one of these surfaces. Therefore, it is conceivable to apply an antireflection film 15 for reducing the reflection at the interface. In addition, even if the antireflection film 15 is applied, a slight amount of reflected light exists as return light, so that the phase difference plates 13a and 13b (or dust proof plates) are particularly provided between the liquid crystal panel 11 and the phase difference plates 13a and 13b. 12a, 12b) and the polarizing plates 14a, 14b, it is desirable to exclude the presence of an air layer. From this, at least between the retardation plates 13a and 13b (or the dustproof plates 12a and 12b) and the polarizing plates 14a and 14b, for example, a birefringent crystal or a polarizing plate base material is refracted in order to eliminate the air layer. It is conceivable to fix using an adhesive or the like that does not greatly differ in rate.

  In the liquid crystal display device configured as described above, when light from the light source 1 enters the liquid crystal display device, the light linearly polarized by the polarizing plate 14a is converted into circularly polarized light by the retardation plate 13a, The liquid crystal panel 11 performs optical modulation according to the video signal. The light emitted from the liquid crystal panel 11 is converted into linearly polarized light by the phase difference plate 13b and then emitted through the polarizing plate 14b. As a result, light having an optical axis orthogonal to the incident side is emitted. Will be. Therefore, the maximum light transmission that occurs when the alignment direction in the VA liquid crystal panel 11 does not form a 45 ° angle with the polarization axes of the polarizing plates 14a and 14b by the ¼ wavelength phase difference function in the phase difference plates 13a and 13b. It becomes possible to prevent a decrease in rate.

  In addition, at this time, since the retardation plate 13b is formed of a birefringent crystal having a 1/4 wavelength phase difference function, the phase difference due to the in-plane uniformity of the refractive index anisotropy of the birefringent crystal is reduced. It becomes easy to suppress the phase difference, and it is possible to avoid the occurrence of elliptically polarized light or the like in the emitted light. That is, for example, the retardation is not uniform in the plane and on the incident side and the emission side, or deviates from the orthogonal state, so that the light incident on the liquid crystal panel 11 is partially elliptically polarized, or is emitted from the liquid crystal panel 11. It is possible to avoid the fact that the light to be converted cannot be converted into linearly polarized light, and elliptical polarized light or the like does not occur in the emitted light. Accordingly, since the linearly polarized light can be completely cut by the polarizing plate 14b on the emission side, the transmittance in the liquid crystal panel 11 in a state where no voltage is applied can be made zero. There is no occurrence of black float on the display image.

  Furthermore, since the phase difference plates 13a and 13b are formed of a birefringent crystal having a 1/4 wavelength phase difference function, light absorption due to the heat resistance, heat dissipation and light resistance of the birefringent crystal. It is possible to suppress the generation of heat due to or the change in optical characteristics due to deterioration. That is, for example, when light passes through the phase difference plates 13a and 13b, the phase difference plates 13a and 13b generate heat, thereby deteriorating optical characteristics of the phase difference plates 13a and 13b. Absent. This is very effective particularly when used in a projection display device in which the intensity of light emitted from the light source 1 is high.

  As described above, according to the liquid crystal display device described here and the projection display device using the liquid crystal display device, the retardation plates 13a and 13b are made of a birefringent crystal having a 1/4 wavelength phase difference function. As it is formed, the in-plane uniformity of refractive index anisotropy is better than when using an organic material phase difference film as in the past, and the increase in black illuminance due to phase difference is suppressed. it can. In addition, changes in optical characteristics due to heat generation and deterioration due to light absorption can be reduced, and the reliability of the liquid crystal display device or the projection display device can be improved. Furthermore, since the birefringent crystal has a higher thermal conductivity than ordinary glass or the like, the light absorption of the liquid crystal panel 11 due to the heat dissipation effect on the liquid crystal panel 11 placed in contact with the phase difference plates 13a and 13b. It can also be expected to reduce the temperature rise due to the above, and this can also improve the reliability of the liquid crystal display device or the projection display device.

Further, as in the liquid crystal display device described here and the projection display device using the liquid crystal display device, if dustproof plates 12a and 12b are provided, the display image by the liquid crystal panel 11 and the foreign matter adhered to the surface of the liquid crystal panel 11 are provided. Therefore, even when a foreign object adheres to the surface of the liquid crystal panel 11, it is possible to prevent the deterioration of the projected image quality due to the foreign object as much as possible.
Further, if the antireflection film 15 for reducing the reflection at the interface is attached as in the liquid crystal display device described here and the projection display device using the liquid crystal display device, stray light due to the phase inversion of the reflected light is prevented. It is possible to suppress the deterioration of characteristics in the liquid crystal display device.

  By the way, in the liquid crystal display device as described above, it is desired that the set angle between the optical axes of the phase difference plates 13a and 13b and the polarization axes of the polarizing plates 14a and 14b be realized with extremely high accuracy. Is very important in getting. Therefore, the angle between the optical axis and the polarization axis is adjusted between the phase difference plate 13a and the polarizing plate 14a arranged adjacent to each other and between the phase difference plate 13b and the polarizing plate 14b. It is desirable to provide an angle adjustment mechanism for this purpose.

Here, the angle adjustment mechanism will be briefly described. As described above, the angle adjusting mechanism is provided between the phase difference plate 13a and the polarizing plate 14a and between the phase difference plate 13b and the polarizing plate 14b. The angle adjusting mechanism provided between the polarizing plate 14a will be described as an example. It is assumed that the angle adjustment mechanism provided between the phase difference plate 13b and the polarizing plate 14b is configured in exactly the same manner.
FIG. 3 is a perspective view illustrating a schematic configuration example of the angle adjustment mechanism. As shown in the figure, the angle adjustment mechanism includes a frame body portion 16 that is a skeleton attached to the polarizing plate 14a, and a phase difference plate 13a via an elastic body 17 such as a spring or rubber. Further, for example, fine adjustment screws 18 are disposed at two opposing positions of the frame body portion 16, for example. The fine adjustment screw 18 presses the edge of the phase difference plate 13a, thereby moving the support position of the phase difference plate 13a in the frame body portion 16. By moving the retardation plate 13a using the fine adjustment screw 18, the angle adjustment mechanism finely adjusts the set angle between the optical axis of the retardation plate 13a and the polarization axis of the polarizing plate 14a.

  By providing such an angle adjustment mechanism, in the liquid crystal display device and the projection display device using the liquid crystal display device, the optical axis of the retardation plate 13b can be accurately set to the optimum angle. Accordingly, it is possible to obtain desired transmittance and contrast characteristics, which is very effective in suppressing the deterioration of the characteristics of the liquid crystal display device due to the deviation of the optical axis.

  Next, specific configuration examples of the liquid crystal display device will be described using Examples 1 to 7 as examples. FIG. 4 is an explanatory diagram showing a specific configuration example of the liquid crystal display device according to the present invention.

  The liquid crystal display device described in Example 1 is No. 1 in FIG. As shown in the column 1, a polarizing plate 14a, a retardation plate 13a, a dustproof plate 12a, a liquid crystal panel 11, a dustproof plate 12b, a retardation plate 13b, and a polarizing plate 14b are arranged in this order from the light incident side. . And the phase difference plates 13a and 13b are formed using sapphire which is a birefringent crystal having a quarter wavelength phase difference function, and the dustproof plates 12a and 12b have a quarter wavelength phase difference function. It is formed using quartz which is a birefringent crystal. That is, with respect to the polarizing plates 14a and 14b arranged so that the polarization axes are orthogonal to each other with the liquid crystal panel 11 interposed therebetween, on the incident light side, the polarizing plate 14a-the retardation plate 13a made of sapphire-the dustproof plate 12a made of crystal. -It arrange | positions so that it may become the order of the liquid crystal panel 11, and is arrange | positioned so that it may become the reverse on the emitted light side. At this time, the slow axes of sapphire and quartz that are both birefringent crystals are matched as much as possible, and the slow axes of the incident light side and the outgoing light side sandwiching the liquid crystal panel 11 are orthogonal to each other. Further, it is assumed that the respective slow axes are arranged at 45 ° with the transmission axes of the adjacent polarizing plates 14a and 14b.

  The thicknesses of sapphire and quartz forming the phase difference plates 13a and 13b and the dustproof plates 12a and 12b may be 0.2 to 0.6 mm, and particularly preferably 0.3 to 0.5 mm. Further, it is most preferable that sapphire = 0.468 mm and quartz = 0.400 mm. If formed with this thickness, the total thickness of the two sheets on each of the incident light side and the outgoing light side becomes less than 1 mm while giving the retardation plates 13a and 13b a circular polarization function. This is because it is possible to provide a function as a dustproof plate without causing an increase in thickness.

  The liquid crystal display device described in Example 2 is No. 1 in FIG. As shown in the column 2, the polarizing plate 14a, the phase difference plate 13a, the dustproof plate 12a, the liquid crystal panel 11, the dustproof plate 12b, the phase difference plate 13b, and the polarizing plate 14b are sequentially arranged from the light incident side. . And the phase difference plates 13a and 13b are formed using sapphire which is a birefringent crystal having a quarter wavelength phase difference function, and the dustproof plates 12a and 12b are formed using glass. Then, for example, a glass plate of about 1 mm thickness sandwiches the liquid crystal panel 11 with respect to the polarizing plates 14a and 14b arranged so that the polarization axes are orthogonal to each other with the liquid crystal panel 11 provided as the dustproof plates 12a and 12b interposed therebetween. The slow axis of sapphire, which is a birefringent crystal, is orthogonal to each other on the incident light side and the outgoing light side, and each slow axis is disposed at 45 ° with the transmission axis of the adjacent polarizing plates 14a and 14b. Has been.

Sapphire thickness to form the phase difference plate 13a, and 13b is the thickness d _s, the wavelength of the transmitted light lambda, the refractive index anisotropy of sapphire when the [Delta] n _s, holds the following equation (1) It is desirable to set as follows.

Δn _s · d _s = λ / 4 + Nλ (N = 0, 1, 2,...) (1)

Specifically, when N = 0, it is conceivable that d _s = 0.016 mm.

  The liquid crystal display device described in Example 3 is No. 1 in FIG. As shown in the column 3, the polarizing plate 14a, the phase difference plate 13a, the dustproof plate 12a, the liquid crystal panel 11, the dustproof plate 12b, the phase difference plate 13b, and the polarizing plate 14b are sequentially arranged from the light incident side. . And the phase difference plates 13a and 13b are formed using the crystal | crystallization which is a birefringent crystal | crystallization which has a 1/4 wavelength phase difference function, and the dustproof plates 12a and 12b are formed using glass. Then, for example, a glass plate of about 1 mm thickness sandwiches the liquid crystal panel 11 with respect to the polarizing plates 14a and 14b arranged so that the polarization axes are orthogonal to each other with the liquid crystal panel 11 provided as the dustproof plates 12a and 12b interposed therebetween. The slow axis of the quartz crystal, which is a birefringent crystal, is orthogonal to each other on the incident light side and the outgoing light side, and each slow axis is disposed at 45 ° with the transmission axis of the adjacent polarizing plates 14a and 14b. Has been.

The thickness of the crystal forming the phase difference plates 13a and 13b is _expressed by the following equation (2), where d _n is the thickness, λ is the wavelength of transmitted light, and Δn _n is the refractive index anisotropy of the crystal. It is desirable to set as follows.

Δn _n · d _n = λ / 4 + Nλ (N = 0, 1, 2,...) (2)

Specifically, it is conceivable that d _n = 0.014 mm when N = 0.

  The liquid crystal display device described in Example 4 is No. 1 in FIG. As shown in the column 4, the arrangement order of the phase difference plate 13a and the dustproof plate 12a on the incident light side described in the third embodiment is switched. That is, on the incident light side, the polarizing plate 14a, the dustproof plate 12a made of glass, the retardation plate 13a made of crystal, and the liquid crystal panel 11 are arranged in this order. Even in such an arrangement order, the function as the dust-proof plate 12a and the circular polarization function by the retardation plate 13a in the liquid crystal display device are not affected at all.

  The liquid crystal display device described in Example 5 is No. 1 in FIG. As shown in the column 5, on the incident light side, the polarizing plate 14a, the phase difference plate 13a made of quartz, the dustproof plate 12a made of sapphire, and the liquid crystal panel 11 are arranged in this order. Even in such an arrangement order, the function as the dust-proof plate 12a and the circular polarization function by the retardation plate 13a in the liquid crystal display device are not affected at all. The slow axes of sapphire and quartz, which are both birefringent crystals, are matched as much as possible, and the slow axes of the incident light side and the outgoing light side sandwiching the liquid crystal panel 11 are orthogonal to each other, Furthermore, each slow axis is arrange | positioned so that 45 degree may be made with the transmission axis of adjacent polarizing plate 14a, 14b.

Even in such a configuration, the thickness of the crystal and sapphire forming the phase difference plate 13a and the dustproof plate 12a may be 0.2 to 0.6 mm as in the case of the first embodiment, and particularly 0.3. It is desirable to set it to -0.5 mm. Further, it is most preferable that sapphire = 0.468 mm and quartz = 0.400 mm. If formed with this thickness, the total thickness of the phase difference plate 13a and the dust-proof plate 12a becomes less than 1 mm while giving the phase difference plate 13a a circular polarization function, leading to an increase in the thickness of the entire liquid crystal display device. This is because it becomes possible to provide a function as a dustproof plate. Further, sapphire is used as a complete dust-proof plate and has a thickness of about 1 mm, and the crystal has a thickness as in Example 3. Specifically, d _n = 0.014 mm when N = 0 in Equation (2). Good. In this case, since the heat dissipation efficiency is further increased, the deterioration of the liquid crystal panel 11 and the phase difference plate 12a can be reduced.

The liquid crystal display device described in Example 6 is No. 1 in FIG. As shown in the column 6, the arrangement order of the phase difference plate 13a and the dustproof plate 12a on the incident light side described in the fifth embodiment is switched. That is, on the incident light side, the polarizing plate 14a, the dustproof plate 12a made of sapphire, the retardation plate 13a made of crystal, and the liquid crystal panel 11 are arranged in this order. Even in such an arrangement order, the function as the dust-proof plate 12a and the circular polarization function by the retardation plate 13a in the liquid crystal display device are not affected at all.
However, the incident light side is greatly affected by heat due to incident light having a high light intensity. Therefore, if sapphire having better thermal conductivity than quartz is disposed on the side closer to the light source 1, it is preferable in that the influence of heat by incident light can be suppressed.

The liquid crystal display device described in Example 7 is No. 1 in FIG. As shown in the column 7, the retardation plate 13a and the dust-proof plate 12a, and the dust-proof plate 12b and the retardation plate 13b are integrally formed of sapphire that is the same birefringent crystal.
For example, in the formula (1) described in the second embodiment, when N is 17 or more, the thickness d _{s of} sapphire exceeds 1 mm. Therefore, the retardation plate 13a formed with that thickness, 13b can also serve as the dustproof plates 12a and 12b. That is, in such a case, the dustproof plates 12a and 12b can be formed integrally with the retardation plates 13a and 13b by the same birefringent crystal as the retardation plates 13a and 13b. In this case, the slow axis of the birefringent crystal is exactly the same as in Example 2.
Thus, when the retardation plates 13a and 13b and the dustproof plates 12a and 12b are integrally formed of the same birefringent crystal, the retardation plates 13a and 13b also function as the dustproof plates 12a and 12b. As a result, it is possible to improve the reliability of the liquid crystal display device by avoiding a decrease in contrast due to an increase in black display, while simplifying the configuration without increasing the number of components.

  Needless to say, the above-described first to seventh embodiments are merely specific examples of the present invention, and the present invention is not limited thereto. For example, on the outgoing light side, there is no problem if the order of the liquid crystal panel 11 -the dustproof plate 12 b -the retardation plate 13 b is changed in the order of the liquid crystal panel 11 -the retardation plate 13 b -the dustproof plate 12 b. That is, the order of arrangement of the phase difference plate and the dustproof plate described in Examples 1 to 7, the types of these forming materials, and the like are appropriately combined and selected in various ways without departing from the spirit of the present invention. Is possible.

It is explanatory drawing which shows the schematic structural example of a projection type display apparatus. It is explanatory drawing which shows the principal part structural example of the liquid crystal display device which concerns on this invention. It is a perspective view which shows the schematic structural example of an angle adjustment mechanism. It is explanatory drawing which shows the specific structural example of the liquid crystal display device which concerns on this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Light source, 6 ... Dichroic mirror, 7R, 7G, 7B ... Liquid crystal display device, 8 ... Dichroic prism, 9 ... Projection lens, 11 ... Liquid crystal panel, 12a, 12b ... Dustproof plate, 13a, 13b ... Phase difference plate 14a, 14b ... Polarizing plate, 15 ... Antireflection film

Claims (9)

A transmissive liquid crystal panel in which a liquid crystal layer for displaying information is sandwiched between a pair of opposing transparent insulating substrates;
A pair of retardation plates made of birefringent crystals having a quarter-wave phase difference function, arranged so as to sandwich the liquid crystal panel;
A liquid crystal display device comprising: a pair of polarizing plates arranged so as to sandwich the pair of retardation plates. 2. The liquid crystal display device according to claim 1, wherein the retardation plate is made of sapphire or quartz crystal that is the birefringent crystal and has in-plane uniformity. Of the pair of retardation plates and the pair of polarizing plates, the retardation plate and the polarizing plate arranged adjacent to each other are formed by the optical axis between the retardation plates and the polarization axis of the polarizing plate. The liquid crystal display device according to claim 1, further comprising an angle adjusting mechanism for adjusting the angle. The liquid crystal display device according to claim 1, wherein the liquid crystal layer in the liquid crystal panel includes liquid crystal molecules that are vertically aligned in a state in which no voltage is applied. Between the liquid crystal panel and the polarizing plate is disposed a dustproof plate for preventing the display image by the liquid crystal panel and the focal length of the surface adhering foreign matter of the liquid crystal panel to coincide with each other,
The liquid crystal display device according to claim 1, wherein the dustproof plate is made of a birefringent crystal. The liquid crystal display device according to claim 5, wherein the dustproof plate is formed integrally with the retardation plate using the same birefringent crystal as the retardation plate. At least one of the surface of the liquid crystal panel, the surface of the retardation plate, the surface of the polarizing plate, or the surface of the dustproof plate is provided with an antireflection film for reducing interface reflection. The liquid crystal display device according to claim 5. A transmissive liquid crystal panel in which a liquid crystal layer for displaying information is sandwiched between a pair of opposing transparent insulating substrates, and a multiple wavelength quarter phase difference function disposed so as to sandwich the liquid crystal panel. A liquid crystal display device comprising a pair of retardation plates made of a refractive crystal and a pair of polarizing plates arranged so as to sandwich the pair of retardation plates;
A light source that emits light to be incident on one of the pair of polarizing plates in the liquid crystal display device;
A projection display device comprising: a projection lens that projects an image with light emitted from the other of the pair of polarizing plates in the liquid crystal display device. A color separation means arranged on an optical path between the light source and the polarizing plate on the light incident side of the pair of polarizing plates, and color-separating incident light from the light source into RGB color component lights;
A color synthesizing unit arranged on an optical path between a polarizing plate on a light emitting side of the pair of polarizing plates and the projection lens, and color-synthesizing the RGB color component lights into one. The projection display device according to claim 8.

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