JP2005107363A - Image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the lowering of contrast due to temperature rise occurring when an optical compensating film for improving the angle characteristic of a liquid crystal panel is constituted in such a way that it is integrated with a polarizing plate in a picture display device such as a liquid crystal projector. <P>SOLUTION: The image display device having at least one image display element and displaying an image has an incident-side base plate 33, the optical compensating film 35 provided in tight-contact with the base plate 33 and the polarizing plate 34 provided in tight-contact with the film 35 on the light incident side of at least one image display element 24. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a technique for cooling a polarizing plate provided with an optical compensation film for improving a contrast angle characteristic of liquid crystal in a liquid crystal projector that projects an image on a screen or the like.

  In an optical system of a liquid crystal projector, white light emitted from a light source is decomposed into three colors of red, green, and blue by a wavelength selective dielectric film, and three liquid crystal elements for a single color are used. A three-plate type liquid crystal projector is known in which transmitted light is further synthesized by a dielectric film to create a color image, and is projected on a screen or the like by a projection lens. A high-intensity lamp such as an ultra-high pressure mercury lamp is used as a light source of the liquid crystal projector, and the reflector surface of the lamp becomes high temperature.

  Also, the temperature of the liquid crystal panel rises due to the light from the light source. The liquid crystal panel uses polarized light, and a pair of polarizing plates is used on the incident side and the emission side of the liquid crystal panel. Since the polarizing plate uses a film type due to cost problems, the transmittance is worse than that of crystals, and light is easily absorbed as heat. When the light whose polarization plane is rotated with respect to the transmission optical axis of the liquid crystal passes through the polarizing plate by driving the liquid crystal, the polarized light is absorbed by the polarizing plate and changed to heat.

  As described above, when the amount of heat absorbed by the liquid crystal panel and the polarizing plate is cooled from the outside and is not used below a temperature at which reliability can be maintained, the display contrast may be lowered by heat. Therefore, in Japanese Patent Laid-Open No. 01-302387 shown in FIG. 13, there is a method in which one axial fan is placed under the dichroic prism to simultaneously cool the three color liquid crystal panels, or Japanese Patent Laid-Open No. 05-053200 shown in FIG. Has developed a liquid crystal projector that consists of a sirocco fan and an air chamber that feeds outside air drawn from the fan into a three-color panel.

  In the conventional liquid crystal projector, as shown in Japanese Patent Laid-Open No. 62-109024, the polarizing plate is arranged away from the liquid crystal element so that the temperature of the liquid crystal element and the polarizing plate does not increase.

  Further, as disclosed in JP-A-10-039138, JP-A-10-039139 and JP-A-10-048590, a polarizing plate is attached to a glass support substrate, and the polarizing plate is deformed by heat. In general, it is configured to prevent this.

  Furthermore, Japanese Patent Application Laid-Open No. 2000-352615 also refers to a material for a polarizing plate substrate. Recently, an attempt has been made to further increase the contrast by inserting an optical compensation film (WV (WideView) film) for correcting unevenness in contrast caused by viewing angle characteristics of the liquid crystal element. The WV film is a hybrid alignment discotic liquid crystal film that improves the viewing angle characteristics of TN (twisted nematic) liquid crystal. As shown in FIG. 15, the disc surface of the discotic structural unit having negative birefringence is oriented so that the angle formed with the transparent support substrate changes in the thickness direction (optical axis direction). The viewing angle characteristics can be improved by canceling the positive birefringence generated by the pretilt orientation and the angle characteristics.

  Details are disclosed in Japanese Patent Application Laid-Open No. 08-050206. Japanese Patent Laid-Open No. 2000-352615 introduces an example in which a WV film is attached to a transparent substrate and inserted alone in the vicinity of a liquid crystal panel as shown in FIG.

However, in the development of portable liquid crystal projectors, downsizing of the illumination optical system is indispensable, and with the downsizing of the illumination optical system, there is a gap through which the air necessary for cooling the polarizing plate and the liquid crystal panel is passed. Less cooling is becoming difficult. Therefore, as shown in FIG. 17, a configuration in which a polarizing plate and an optical compensation film, which are partially employed in Japanese Patent Application Laid-Open No. 2001-235747 and a direct-view display, can reduce the number of parts and reduce the cooling space. It is effective because it does not narrow. However, as described above, in the liquid crystal projector, the configuration of the polarizing plate is deeply related to the thermal problem, and these thermal problems are not sufficiently discussed.
Japanese Patent Laid-Open No. 01-302387 JP 05-053200 A Japanese Patent Laid-Open No. 62-109024 JP 10-039138 A Japanese Patent Laid-Open No. 10-039139 JP 10-048590 A JP 2000-352615 A Japanese Patent Laid-Open No. 08-050206 JP 2001-235747 A

  As described above, the cooling of the liquid crystal panel and the polarizing plate in the liquid crystal projector solves the problem related to the cooling when the optical compensation film for improving the angle characteristic of the contrast of the liquid crystal panel is integrated with the polarizing plate. .

  In order to solve the above-described problems, an image display device of the present invention is an image display device that has at least one image display element and displays an image, on the light incident side of the at least one image display element. And an incident side substrate, an optical compensation film provided in close contact with the substrate, and a polarizing plate provided in close contact with the optical compensation film.

  Here, on the light exit side of the at least one image display element, an exit side substrate, an optical compensation film provided in close contact with the substrate, and a polarizing plate provided in close contact with the optical compensation film It is preferable to have. Furthermore, it is preferable to have a blower that sends air between the emission side substrate and the at least one image display element and / or to the light emission side of the emission side substrate.

  Further, it is preferable to have a blower that sends air between the incident side substrate and the at least one image display element and / or to the light incident side of the incident side substrate.

  The image display device of the present invention is an image display device that has at least one image display element and displays an image, and an emission side substrate on the light emission side of the at least one image display element, An optical compensation film provided in close contact with the substrate and a polarizing plate provided in close contact with the optical compensation film are provided.

  Here, it is preferable to have a blower that sends air between the emission side substrate and the at least one image display element and / or to the light emission side of the emission side substrate. The optical compensation film preferably has a birefringence effect.

  The image display device of the present invention has a projection lens, a light modulation element, and means for illuminating the element, and the illumination light divided by the color dividing means provided in the illumination means is the light of each color. In the projection display device that illuminates the modulation element, further synthesizes the illumination light modulated by the light modulation element by the color synthesizing means, and projects the enlarged image by the projection lens, the polarizing plate is attached to a transparent substrate, An optical compensation film is provided between the transparent substrate and the polarizing plate, the optical compensation film has birefringence, and the angle between the principal axis of the refractive index ellipsoid indicating the refractive index of the optical compensation film and the transparent substrate is the thickness of the optical compensation sheet. It is characterized by having a cooling device that cools the polarizing plate.

  Here, it is preferable that the optical compensation film is provided on the surface of the transparent substrate opposite to the polarizing plate attached to the transparent substrate, and has a cooling device for cooling the polarizing plate.

  In addition, the transparent substrate includes a polarizing plate that is flat on one side and is attached to the flat side of the transparent substrate, and includes an optical element having the optical compensation film between the substrate and the polarizing plate. It is preferable to have a cooling device for cooling the water. The photoelastic constant of the transparent substrate is preferably smaller than that of glass. The transparent substrate is preferably a crystal, and the crystal structure of the crystal belongs to an equiaxed crystal system. The cooling means is preferably a fan blower.

  With the above configuration, it is possible to provide a liquid crystal projector with good contrast.

  Hereinafter, preferred embodiments will be described in detail with reference to the drawings.

  FIG. 1 shows a top view of a projection type display apparatus which is the first embodiment of the present invention. Reference numeral 1 denotes a light source, which includes, for example, a high-intensity ultra-high pressure lamp, a metal halide lamp, and the like. The light emitted from the lamp is reflected by the reflector 2 and input to the first fly-eye lens 3 which is a group of lens groups arranged in a grid pattern. The light reflected by the total reflection mirror 5 is further reflected by the second fly-eye. Each light beam collected by the eye lens 4 enters the polarization conversion element 4, and the light whose polarization direction is aligned is guided by the condenser lens 7 and then guided to the dichroic mirror 8 that reflects the blue frequency band.

  The blue light transmitted through the concave lens 10 having the effect of shortening the optical path length is reflected by the total reflection mirror 11, passes through the field lens 20 and the incident side polarizing plate 23, and reaches the blue panel 26. The light transmitted through the blue reflecting dichro 8 is separated into green light and red light by the dichroic mirror 12 that reflects the green frequency band. The reflected green light passes through the field lens 19 and the incident side polarizing plate 22 and reaches the green panel 25. Unnecessary light is removed from the transmitted red light by the red transmissive dichroic filter, and the red light is transmitted through the red incident polarizing plate 21 by the field lenses 14 and 18, the relay lens 16, and the total reflection mirrors 15 and 16, and reaches the red panel 24. The three colors of _ light that have reached the liquid crystal panel are modulated by the liquid crystal panels 24, 25, and 26 into light intensity corresponding to the image signal, and then transmitted through the panel, through the output side polarizing plates 27, 28, and 29, and dichroic. Color synthesis is performed by the cross prism 30 on which the film is deposited. Further, the light emitted from the prism 29 is enlarged and projected on the screen by the projection lens 31. These optical systems are attached to the illumination optical box 32 so that the incident-side polarizing plates 21, 22, 23, the outgoing-side polarizing plates 27, 28, 29, and the liquid crystal panels 24, 25, 26 have good ventilation. In addition, a cooling fan or a blower duct can be attached to the upper or lower portion of the illumination optical box 32.

  Next, the schematic diagram of the polarizing plate and panel in the present invention is shown in FIG. The polarizing plate is a diagram in the case where the polarizing plate is separated from the field lenses 18, 19, 20 and the prism 30. In the substrate 33 on the incident side of the liquid crystal panel, the incident side WV film 35 is attached to the surface opposite to the liquid crystal panel 24. Further, a polarizing plate 34 is attached on the WV film 35. Similarly, on the substrate 36 on the emission side of the liquid crystal panel, the emission side WV film 37 is attached to the surface opposite to the liquid crystal panel. Further, a polarizing plate 38 is attached on the WV film 37.

  Accordingly, the polarizing plate is exposed to the outside air without being covered with the WV film or the like. Further, it is directly cooled by, for example, an axial fan or a sirocco fan 39 that winds on the surface of the polarizing plate. Moreover, the structure which makes a wind guide structure and sends the wind from a sirocco fan may be used.

  Here, the WV film is a hybrid alignment discotic liquid crystal film that improves the viewing angle characteristics of TN (twisted nematic) liquid crystal. As shown in FIG. 15, the disc surface of the discotic structural unit having negative birefringence is oriented so that the angle formed with the transparent support substrate changes in the thickness direction (optical axis direction) (thickness If the position of the direction changes, the angle formed by the disk surface and the transparent support base changes. In other words, the angle formed by the disk surface and the transparent support base differs from each other at two points that are different from each other in the thickness direction. The viewing angle characteristics can be improved by canceling the positive birefringence generated by the pretilt alignment of the TN liquid crystal and the angular characteristics. The description regarding the WV film is applicable to the examples described later.

  As shown in FIG. 3, in the transparent substrate 33 on the incident side of the liquid crystal panel, the incident side WV film 40 is pasted on the surface opposite to the liquid crystal panel 24, and the polarizing plate 41 is pasted on the surface on the liquid crystal panel 24 side. Similarly, in the transparent substrate 36 on the liquid crystal panel emission side, the WV film 42 may be attached to the surface on the liquid crystal panel 24 side, and the polarizing plate 42 may be attached to the surface on the liquid crystal panel 24 side. With this configuration, heat is transferred directly to the transparent substrates 33 and 36 as shown in FIG. 3 without passing through the WV film as shown in FIG. 2, so when using a transparent substrate with good thermal conductivity, Heat is transmitted effectively and is advantageous. In the wind guide structure, since the heat absorption by the WV film is slight, it is possible to attach a wind guide plate so as to actively cool the polarizing plate and the liquid crystal panel.

  FIG. 4 describes the case where the WV film is used only on the incident side. As a result, the exit-side polarizing plate can be attached to the substrate alone with the conventional configuration, and the substrate 45 to which the exit-side polarizing plate 44 is attached may be a color synthesis prism. At this time, on the substrate 46 on the incident side of the liquid crystal panel 24, the WV film is attached to the surface opposite to the liquid crystal panel 24, and the WV film 47 for the incident side and the WV film 48 for the emission side are attached. The incident side polarizing plate 49 is affixed. It has been reported that there is almost no change in the viewing angle improvement effect of the WV film when two sheets are stacked. Accordingly, the polarizing plate is exposed to the outside air without being covered with the WV film or the like. Further, it is directly cooled by, for example, an axial fan or a sirocco fan 39 where the wind is applied to the surface of the polarizing plate. Moreover, the structure which makes a wind guide structure and sends the wind from a sirocco fan may be used. Further, since the number of substrates disposed between the polarizing plates 44 and 49 sandwiching the liquid crystal panel is reduced as compared with the configuration of FIG. 4, the change in contrast due to the slight thermal stress generated on the substrate by heat is also minimized. It is possible to hold down. Although the case where two WV films are used on the incident side has been described above, a configuration in which two WV films are also used on the exit side polarizing plate is also possible.

  In the substrate 46 shown in FIG. 4, the two WV films can be moved to the liquid crystal panel 24 side, and the polarizing plate 49 can be directly attached to the substrate 46. As a result, the heat is transmitted directly from the thermal polarizing plate 49 to the substrate 46 without passing through the WV film, so that it is advantageous to use a transparent substrate having good thermal conductivity for cooling the polarizing plate 49. In the wind guide structure, since the heat absorption by the WV film is slight, it is possible to attach a wind guide plate so as to actively cool the polarizing plate and the liquid crystal panel.

  In the configuration shown in FIG. 4, the convex surface of the field lens 50 having a plano-convex shape as shown in FIG. 6 is arranged so that the convex surface is on the liquid crystal panel side, and the flat surface is on the light source side. , 2 of the emission side WV film 48 may be attached, and the polarizing plate 43 may be attached thereon. Furthermore, it is directly cooled by, for example, an axial fan or a sirocco fan that winds on the surface of the polarizing plate. Moreover, the structure which makes a wind guide structure and sends the wind from a sirocco fan may be used.

  Examples 1 and 2 were configured only with a polarizing plate and a WV film, but when a half-wave plate is used due to the configuration of the illumination optical system, for example, as shown in FIG. In the transparent substrate thus formed, a WV film is pasted on the opposite side of the transparent substrate 33 from the liquid crystal panel, a half-wave plate 51 is further pasted, and a polarizing plate 34 is pasted thereon. Thus, the surface of the polarizing plate is not covered and can be cooled by directly blowing cooling air with a cooling device. Similarly, the WV film 37 is attached to the opposite side of the transparent substrate 36 from the liquid crystal panel, the half-wave plate 52 is further attached, and the polarizing plate 38 is further attached thereon. Further, in FIG. 8, a half-wave plate 51 is attached to the liquid crystal panel side of the transparent substrate 33 arranged on the incident side and the emission side of the liquid crystal panel, and a WV film 35 is attached thereon, and then the liquid crystal panel and The polarizing plate 34 may be attached to the opposite surface. Similarly, a half-wave plate 52 is pasted on the liquid crystal panel side of the transparent substrate 36 disposed on the emission side of the liquid crystal panel, a WV film 37 is pasted thereon, and then on the surface opposite to the liquid crystal panel. A polarizing plate 38 may be attached. As a result, the surface of the polarizing plate is not covered and can be cooled by blowing the cooling air directly with the cooling device. Furthermore, the heat from the polarizing plate is directly transferred to the transparent substrate, so it can be cooled more efficiently. It is. Next, when two WV films are used on the incident side or the emission side, as shown in FIG. 9, the incident side WV film 48, the emission side WV film 47, the half-wave plate 53, and the polarizing plate 49 are arranged in this order on the substrate 46. paste. Accordingly, the polarizing plate 49 is exposed to the outside air. In addition, as shown in FIG. 10, the incident side WV film 48, the emission side WV film 47, and a half-wave plate are attached to the liquid crystal panel side of the substrate 46, and the polarizing plate 49 is attached to the surface opposite to the liquid crystal. By doing so, it becomes possible to cool the polarizing plate effectively. It is cooled directly by, for example, an axial fan or a sirocco fan 39 that winds on the surface of the polarizing plate. Moreover, the structure which makes a wind guide structure and sends the wind from a sirocco fan may be used.

  In the first to third embodiments, another optical member that covers the polarizing plate surface is not attached, and cooling of the polarizing plate is promoted by sending air directly to the polarizing plate surface by a cooling device. When the WV film is attached to the polarizing plate surface, as shown in FIG. 11, a polarizing plate 54 that is sufficiently larger than the size of the WV film 55 having a shape larger than the illumination light effective portion 56 is formed on the substrate 53. Some cooling can be promoted by sticking and blowing air to the polarizing plate part. The heat generated in the central portion of the polarizing plate is made uniform over the entire polarizing plate with time, and heat can be expected to escape from the portion where the WV film is not attached.

  In Examples 1 to 7, the material used as the transparent substrate is preferably glass or crystal having a small photoelastic constant. A crossed Nicol optical system is formed by the polarizing plate disposed on the incident side of the liquid crystal panel and the polarizing plate disposed on the output side. The birefringence of the transparent substrate itself deteriorates the contrast or causes uneven color and is projected on the screen. This can occur where there is such an element between the PS conversion element and the exit side polarizing plate. Therefore, the optical member used preferably has a small photoelastic constant. By using an optical member having a small photoelastic constant, light leakage due to birefringence caused by thermal stress or mechanical stress can be reduced. Further, when using crystals, fluorite belonging to the equiaxed system with little difference in polarization characteristics even when obliquely incident is effective. In particular, with respect to oblique incidence, when a substrate is made of a uniaxial crystal such as sapphire, the light leakage with respect to oblique incidence increases as the thickness increases. However, crystals belonging to the equiaxed crystal system, such as fluorite, have the same refractive index when viewed from any crystal axis. Therefore, even if the thickness is increased, light leakage is small and advantageous. In general, by increasing the thickness of the substrate, the heat capacity increases and the amount of heat generated by the polarizing plate can be absorbed. Therefore, it is advantageous to use a crystal belonging to the equiaxed crystal system.

  In Examples 1-8, although the method of laminating | stacking a WV film, a polarizing plate, and a half-wave plate has been described, each element is normally by the TAC (triacetylcellulose triacetylcellulose) layer 68 as shown in FIG. It is sandwiched and maintains strength. Therefore, when the layers are stacked, the elements sandwiched between the TAC layers are bonded to each other, so that there is a problem that the effect of the cooling air 67 is not sufficiently transmitted because the thickness is increased and heat is easily trapped. Therefore, when laminating these optical elements, it is possible to reduce the thickness by omitting the TAC layer as much as possible, and this can be expected to improve the cooling efficiency. Actually, in the conventional example shown in FIG. 18, when the WV film and the polarizing plate are bonded, either one of the TAC layers 68 to be bonded to each other or the integrated TAC layer is omitted. The omitted figure is shown in FIG. By providing only the minimum TAC layer that can maintain the strength, the thickness can be reduced, and the cooling efficiency by the cooling air 60 is improved.

  According to the embodiments as described above, regarding cooling of the liquid crystal panel and the polarizing plate in the liquid crystal projector, the cooling in the case where the optical compensation film for improving the angle characteristic of the contrast of the liquid crystal panel is integrated with the polarizing plate. In order to solve the above problems, a configuration in which a polarizing plate and a WV film as an optical compensation film are attached, a material for the substrate, and a cooling method for the polarizing plate have been described. This makes it possible to provide a liquid crystal projector with good contrast.

It is a top view of the liquid crystal projector in Examples 1-9 of this invention. It is a side view of the liquid crystal projector liquid crystal panel part in Example 1 of this invention. It is a side view of the liquid crystal projector liquid crystal panel part in Example 2 of this invention. It is a side view of the liquid crystal projector liquid crystal panel part in Example 3 of this invention. It is a side view of the liquid crystal projector liquid crystal panel part in Example 4 of this invention. It is a side view of the liquid crystal projector liquid crystal panel part in Example 5 of this invention. It is a side view of the liquid crystal projector liquid crystal panel part in Example 6 of this invention. It is a side view of the liquid crystal projector liquid crystal panel part in Example 6 of this invention. It is a side view of the liquid crystal projector liquid crystal panel part in Example 6 of this invention. It is a side view of the liquid crystal projector liquid crystal panel part in Example 6 of this invention. It is a perspective view of the polarizing plate and polarizing plate substrate part in Example 7 of this invention. It is sectional drawing of the polarizing plate and polarizing plate substrate part in Example 9 of this invention. It is the cooling method of the panel part in a prior art example. It is the cooling method of the panel part in a prior art example. It is a structural diagram of a viewing angle improving film (WV film) in a conventional example. It is a usage example of the viewing angle improvement film (WV film) in a prior art example. It is a usage example of the viewing angle improvement film (WV film) in a prior art example. It is sectional drawing of the polarizing plate and board | substrate part in a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 2 Reflector 3 Fly eye lens 4 Fly eye lens 5 Mirror 6 PS conversion element 7 Condenser lens 8 Blue reflection dichroic mirror 9 Concave lens 10 Concave lens 11 Blue reflection mirror 12 Green reflection dichroic mirror 13 Red transmission dichroic mirror 14 Field lens 15 Red reflection Mirror 16 Relay lens 17 Red reflection mirror 18 Red field lens 19 Green field lens 20 Blue field lens 21 Red incident side polarizing plate 22 Green incident side polarizing plate 23 Blue incident side polarizing plate 24 Red liquid crystal panel 25 Green liquid crystal panel 26 Blue liquid crystal panel 27 Red output side polarizing plate 28 Green output side polarizing plate 29 Blue output side polarizing plate 30 Color composition prism 31 Projection lens 32 Optical box 33 Incident side transparent substrate 34 Incident side polarizing plate 35 Incident side WV film 36 Outgoing side transparency Substrate 37 Outgoing side WV film 38 Outgoing side polarizing plate 39 Axial fan 40 Incident side WV film 41 Incident side polarizing plate 42 Outgoing side WV film 43 Outgoing side polarizing plate 44 Outgoing side polarizing plate 45 Outgoing side transparent substrate 46 Incoming side transparent substrate 47 Emission side WV film 48 Incident side WV film 49 Incident side polarizing plate 50 1/2 wavelength plate 51 1/2 wavelength plate 52 1/2 wavelength plate 53 1/2 wavelength plate 54 Polarizing plate 55 WV film 56 Light beam effective part 57 Substrate 58 Adhesive layer 59 Protective film 60 Cooling air 61 TAC layer 62 WV layer 63 Polarizing layer 64 Substrate 65 Adhesive layer 66 Protective film 67 Cooling air 68 TAC layer 69 WV film 70 Change layer

Claims (13)

An image display device that has at least one image display element and displays an image,
The light incident side of the at least one image display element has an incident side substrate, an optical compensation film provided in close contact with the substrate, and a polarizing plate provided in close contact with the optical compensation film. A characteristic image display device.   The light emitting side of the at least one image display element has an emission side substrate, an optical compensation film provided in close contact with the substrate, and a polarizing plate provided in close contact with the optical compensation film. The image display device according to claim 1, wherein:   The image display apparatus according to claim 2, further comprising a blower that sends air between the emission side substrate and the at least one image display element and / or to the light emission side of the emission side substrate.   4. The image according to claim 1, further comprising a blower that sends air between the incident side substrate and the at least one image display element and / or to a light incident side of the incident side substrate. 5. Display device. An image display device that has at least one image display element and displays an image,
The light emitting side of the at least one image display element has an emission side substrate, an optical compensation film provided in close contact with the substrate, and a polarizing plate provided in close contact with the optical compensation film. A characteristic image display device.   The image display apparatus according to claim 5, further comprising a blower that sends air between the emission side substrate and the at least one image display element and / or to a light emission side of the emission side substrate.   The image display device according to claim 1, wherein the optical compensation film has a birefringence function.   A projection lens, a light modulation element, and means for illuminating the element, and the illumination light divided by the color dividing means provided in the illumination means illuminates the light modulation element of each color, and further the light modulation element In a projection display device that synthesizes illumination light modulated by the color by means of color synthesizing means and enlarges and projects by the projection lens, a polarizing plate is attached to a transparent substrate, and an optical compensation film between the transparent substrate and the polarizing plate The optical compensation film has birefringence, the angle of the principal axis of the refractive index ellipsoid indicating the refractive index of the optical compensation film and the transparent substrate is changed in the thickness direction of the optical compensation sheet, and An image display device comprising a cooling device for cooling a polarizing plate.   9. The cooling apparatus according to claim 8, further comprising a cooling device that includes the optical compensation film on a surface of the transparent substrate opposite to the polarizing plate attached to the transparent substrate and cools the polarizing plate. Image display device.   The transparent substrate is provided with a polarizing plate formed on only one flat surface and attached to the flat surface of the transparent substrate, an optical element having the optical compensation film between the substrate and the polarizing plate, and the polarizing plate is cooled. The image display device according to claim 8, further comprising a cooling device.   The image display device according to claim 8, wherein the transparent substrate has a photoelastic constant smaller than that of glass.   12. The image display device according to claim 8, wherein the transparent substrate is a crystal, and the crystal structure of the crystal belongs to an equiaxed crystal system.   The image display device according to claim 8, wherein the cooling unit is a fan blower.

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