JP2002268139A - Liquid crystal display device, liquid crystal projector device, and panel cooling method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal projector device which can efficiently cool a liquid crystal panel without causing any trouble due to fan noise and blown-up dust. SOLUTION: The liquid crystal panel 16 is cooled by using a polygonal dichroic prism 23 as a cool temperature bath by uniting the liquid crystal panel 16 with the light incidence surface of the dichroic prism 23 in close contact across a polarizing plate 26 and a glass substrate 27.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal display, a liquid crystal projector, and a panel cooling method.

[0002]

2. Description of the Related Art At present, a liquid crystal projector using a liquid crystal panel for a liquid crystal light valve is being actively developed. Liquid crystal projector devices mainly include data projector devices for personal computer applications, front projector devices for home theater applications, and rear projector devices for rear projection television applications.

[0003] The liquid crystal projector device has R (red), G
(Green), B (blue) Single-plate type using one liquid crystal light valve (liquid crystal panel) with three color filters, and monochrome liquid crystal light valve (liquid crystal panel) with R, G, B
The optical path is roughly divided into a three-plate type using three optical paths. In addition, the liquid crystal projector device is classified into a transmission type projector and a reflection type projector according to whether a central liquid crystal light valve is a transmission type or a reflection type.

Here, in the optical system of a three-panel transmissive liquid crystal projector, three light incident surfaces of a dichroic prism (cross prism) made of a polyhedron are provided on R, G, and B light incident surfaces.
The liquid crystal light valves corresponding to the respective colors are arranged in opposition to each other.
Light and B light are combined by a dichroic prism and incident on a projection lens.

At this time, the liquid crystal light valves of the respective colors generate heat due to light absorption or the like, so that the temperature during operation (hereinafter referred to as operating temperature) increases. On the other hand, in a liquid crystal light valve, in addition to the liquid crystal itself, an organic substance is used for an alignment film, a seal portion, a polarizing plate, a phase difference plate, and the like, and an organic substance is used for a flattening film on a thin film transistor (TFT). ing. For this reason, there is a concern that the reliability may be degraded due to a rise in temperature or an increase in the amount of light.

Therefore, conventionally, as a cooling method of a liquid crystal light valve (liquid crystal panel), an air cooling system using a fan has been proposed. In this air cooling system, the fan is rotated to blow air to the liquid crystal light valve to cool it.

[0007]

However, the air-cooling system has disadvantages such as generation of noise due to the rotation of the fan and flying of dust. In particular, in the future, the pixel density of the liquid crystal light valve (liquid crystal panel) and the density of the amount of light incident on the liquid crystal light valve will increase with the development of higher brightness, higher image quality, and higher definition of the liquid crystal projector device. The operating temperature of the light valve tends to increase. Therefore, in the air-cooling system, it is necessary to suppress noise and dust, so it is not possible to sufficiently suppress the temperature rise of the liquid crystal light valve, and it is expected that maintaining reliability will be difficult.

[0008]

A liquid crystal display device and a liquid crystal projector device according to the present invention have a structure in which a liquid crystal panel is attached to a light incident surface of a prism through a transparent substrate having high heat conductivity in a tightly contacting state and integrated. Has become.

In the liquid crystal display device and the liquid crystal projector device having the above-described structures, the liquid crystal panel is attached to the light incident surface of the prism via a transparent substrate having high thermal conductivity in a tightly contacted state and integrated, thereby generating the liquid crystal panel. Heat is absorbed by the transparent substrate, and the absorbed heat is dissipated by the prism. Thus, the liquid crystal panel is efficiently cooled by using the prism as a cooling / heating bath.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention when applied to, for example, a three-panel transmissive liquid crystal projector will be described in detail with reference to the drawings.

FIG. 1 is a schematic diagram showing an example of an optical system configuration of a liquid crystal projector to which the present invention is applied. In FIG. 1, a lamp 1 serves as a light source of a liquid crystal projector, and is constituted by, for example, a metal halide lamp. A UV-IR cut filter 2, an optical integrator 3, a polarization conversion element 4, a first lens 5, and a first total reflection mirror 6 are arranged in this order in the light emission direction of the lamp 1.

On the other hand, a first dichroic mirror 7 and a second total reflection mirror 8 are sequentially arranged in the light reflection direction of the first total reflection mirror 6. A second dichroic mirror 9, a second lens 10, and a third total reflection mirror 11 are sequentially arranged in the direction of light reflection by the first dichroic mirror 7. A third lens 12 and a fourth total reflection mirror 13 are sequentially arranged in the light reflection direction.

In the direction of light reflection by the second total reflection mirror 8, a liquid crystal light valve 14 for R (red) is provided.
A liquid crystal light valve 15 for G (green) is provided in the direction of light reflection by the second dichroic mirror 9, and a liquid crystal light valve 16 for B (blue) is provided in the direction of light reflection by the fourth total reflection mirror 13. , Respectively. Also,
On the light incident side of each of the liquid crystal light valves 14, 15, 16, lenses 17, 18, 19 and polarizing plates 20, 2, respectively.
1 and 22 are arranged. Liquid crystal light valve 14,1
As TFTs 5 and 16, TFT liquid crystal panels in which thin film transistors (TFTs) are arranged in a matrix can be used. Hereinafter, "liquid crystal light valve" is replaced by "liquid crystal panel".
This will be described.

A dichroic prism 23 is arranged in a region surrounded by each of the liquid crystal panels 14, 15, 16. The dichroic prism 23 constitutes the prism of the present invention, and is also called a cross prism. The dichroic prism 23 has a polygonal (hexahedral) rectangular block structure in which four prisms are bonded together. Dichroic prism 23
Has three light entrance surfaces and one light exit surface. The liquid crystal panels 14, 15, 16 are provided on the respective light incident surfaces.
Are arranged facing each other, and a polarizing plate 24 is attached to the light emitting surface.

A projection lens 25 is arranged in the light emission direction of the dichroic prism 23. The projection lens 25 includes a plurality of projection lenses 25 arranged on a common optical axis (for example,
(5 to 10) combination lenses.

In the optical system of the liquid crystal projector having the above configuration, the white light emitted from the lamp 1
The light enters the first total reflection mirror 6 through the V-IR cut filter 2, the optical integrator 3, the polarization conversion element 4, and the first lens 5, where it is reflected at a substantially right angle. that time,
The ultraviolet light and the infrared light included in the light emitted from the lamp 1 are as follows.
It is cut by the UV-IR cut filter 2.

The light reflected by the first total reflection mirror 6 is
The light is selectively transmitted and reflected by the first dichroic mirror 7. That is, the first dichroic mirror 7 transmits the R light and reflects the G and B lights. The R light transmitted through the first dichroic mirror 7 is converted into a second total reflection mirror 8.
After that, the light enters the liquid crystal panel 14 through the lens 17 and the polarizing plate 20.

On the other hand, the G and B lights reflected by the first dichroic mirror 7 are selectively transmitted and reflected by the second dichroic mirror 9. That is, in the second dichroic mirror 9, B light is transmitted and G light is reflected. The G light reflected by the second dichroic mirror is
8 and the liquid crystal panel 15 through the polarizing plate 21.

The B light transmitted through the second dichroic mirror 9 is incident on the third total reflection mirror 11 through the second lens 10, where it is reflected at a substantially right angle. Further, the B light reflected by the third total reflection mirror 11 enters the fourth total reflection mirror 13 through the third lens 12,
Then, after being reflected at substantially a right angle, the lens 19 and the polarizing plate 2
2 and enters the liquid crystal panel 16.

As described above, the light (white light) emitted from the lamp 1 is separated into R, G, and B, and each of the liquid crystal panels 14, 1 is separated.
5 and 16, the three liquid crystal panels 1
Optical images of the corresponding colors are formed on 4, 15, and 16, respectively. Liquid crystal panels 14, 15, 16
Is formed by controlling the amount of light transmission for each pixel in each panel.

Further, each of the liquid crystal panels 14, 15, 1
The R, G, and B lights transmitted through 6 enter the dichroic prism 23. In the dichroic prism 23, 3
The R, G, and B lights incident from the directions are combined, thereby generating one optical image composed of R, G, and B. The optical image thus generated is transmitted from the light exit surface of the dichroic prism 23 through the polarizing plate 24 to the projection lens 25.
Incident on. Then, the projection lens 25 enlarges the incident light (optical image) from the dichroic prism 23 and projects it on a screen (not shown). Incidentally, the first to third lenses 5, 10, and 12 serve to equalize the optical path lengths of R, G, and B.

FIG. 2 is a top view showing an example of the main structure of the liquid crystal projector according to the first embodiment of the present invention.
FIG. 3 is a partial sectional view thereof. First, as shown in FIG. 2, liquid crystal panels 14, 15, and 16 are attached to three light incident surfaces of the dichroic prism 23, respectively.
3 and the respective liquid crystal panels 14, 15, 16 are integrated.

Hereinafter, a specific mounting structure of the liquid crystal panels 14, 15, 16 to the dichroic prism 23 will be described with reference to the liquid crystal panel 16 shown in FIG. 3 as an example. A polarizing plate 26 and a transparent glass substrate 27 are interposed between the dichroic prism 23 and the liquid crystal panel 16. The transparent glass substrate 27 is made of a substrate material having high thermal conductivity,
For example, it is made of sapphire glass, Vycol, Zerodeure, Tempax glass, or the like. Incidentally, as a material of the transparent glass substrate 27, a material having no birefringence is more preferable.

A dust-free plate 28 is arranged on the light incident side of the liquid crystal panel 16 (on the side opposite to the dichroic prism 23). Dust free plate 28
Is made of glass, and has a function of defocusing dust existing on the optical path from the focal length of the projection lens 25.

On the light incident surface of the dichroic prism 23, the above-described polarizing plate 26, transparent glass substrate 27, and dust-free plate 28 are mounted together with the liquid crystal panel 16 in surface contact with each other. That is,
One surface of the polarizing plate 26 is in contact with the light incident surface of the dichroic prism 23. The other surface of the polarizing plate 26 is in contact with one surface of the transparent glass substrate 27. On the other hand, one surface of the liquid crystal panel 16 is in contact with the other surface of the transparent glass substrate 27. The other surface of the liquid crystal panel 16 is in contact with one surface of the dust-free plate 28.

The dichroic prism 23, the polarizing plate 26, the transparent glass substrate 27, the liquid crystal panel 16, and the dust-free plate 28 are fixed to each other using a transparent adhesive. As the adhesive, a refractive index substantially equal to that of the material of the dichroic prism 23 (for example, n
= 1.4 to 1.6) (e.g., an ultraviolet curable resin). The reason is to suppress light reflection (interface reflection) at the contact interface between components. Examples of the resin used for the adhesive include an acrylic resin, a urethane resin, an epoxy resin, a silicone resin, and the like, and further, a silicone gel, oil, or the like can be used.

In the above configuration, since the transparent glass substrate 27 having high thermal conductivity is interposed between the dichroic prism 23 and the liquid crystal panel 16, the thermal resistance between the liquid crystal panel 16 and the dichroic prism 23 is reduced. It can be kept small. Further, the heat generated in the liquid crystal panel 16 is sucked by the transparent glass substrate 27, and the sucked heat can be efficiently radiated from the transparent glass substrate 27 and the dichroic prism 23. The same applies to the other liquid crystal panels 14 and 15.

As a result, each of the liquid crystal panels 14, 15,
Since the dichroic prism 23 having a large heat capacity is efficiently cooled as a cooling / heating bath, the operating temperature of the liquid crystal panels 1, 4, 15, and 16 can be reduced without cooling the liquid crystal panel using a fan as in the related art. It can be reduced sufficiently. In addition, a transparent glass substrate 27 is interposed between the liquid crystal panel 1 and the dichroic prism 23.
In the configuration in which 4, 15 and 16 are attached, a plurality of liquid crystal panels are formed on the glass substrate using a large-diameter glass substrate, and then the glass substrate is cut along a predetermined line, whereby the individual substrates are cut. Application to a manufacturing method such as obtaining a plurality of liquid crystal panels divided into pieces simultaneously is also possible.

FIG. 4 is a partial cross-sectional view showing a main part of a liquid crystal projector according to a second embodiment of the present invention, and FIG. 5 is an exploded perspective view thereof. In the second embodiment as well, a specific mounting structure of the liquid crystal panels 14, 15, 16 to the dichroic prism 23 will be described using the liquid crystal panel 16 as an example.

4 and 5, the polarizing plate 26, the transparent glass substrate 27, the liquid crystal panel 16, and the dust-free plate 28 are fixed to each other using an adhesive. Further, the liquid crystal panel 16 is detachably attached to the dichroic prism 23 by a crimping method.

More specifically, a support member 30 is provided upright at four corners of a base plate 29 having a rectangular shape in a plan view. The base plate 29 can be formed integrally with the chassis of the liquid crystal projector. Each support member 30 has a long L-shaped plate structure, and is preferably made of a metal material having high thermal conductivity (for example, aluminum, steel, or the like).

Of the base plate 29 and the four support members 30, two support members 30 corresponding to the mounting position of the liquid crystal panel 16 have a total of eight screw holes H1.
To H8, and the base plate 29 is provided with two screw holes H9 and H10. Of these, screw hole H
1 to H4 are for fixing the liquid crystal panel 16 to the dichroic prism 23 by a crimping method. The screw holes H5 to H8, H9, and H10 are provided in the liquid crystal panel 1.
6 to adjust the mounting position in the horizontal direction (X direction in FIG. 5), the vertical direction (Y direction in FIG. 5), and the rotation direction (θ direction in FIG. 5).

When the liquid crystal panel 16 is mounted on the dichroic prism 23 by using the base plate 29 and the four support members 30 having the above configuration, first, the dichroic prism 23 is positioned and fixed at a predetermined position on the base plate 29. . The dichroic prism 23 is fixed by fixing the bottom surface of the dichroic prism 23 to the upper surface of the base plate 29 with an adhesive. Thus, the dichroic prism 23 is disposed in a space surrounded by the four support members 30.

Next, the polarizing plate 26 and the transparent glass substrate 2
7. An integrated component in which the liquid crystal panel 16 and the dust-free plate 28 are fixed to each other is arranged close to the light incident surface of the dichroic prism 23. At this time, the integrated component is assembled from above by inserting the transparent glass substrate 27 between two support members 30 having eight screw holes H1 to H8. Thereby, four screw holes H1
H4 outside the liquid crystal panel 16 (other than the effective pixel area)
And is disposed on the front surface of the transparent glass substrate 27 so as to face the front surface of the transparent glass substrate 27 via a predetermined gap. Also, the four screw holes H5 to H8 are
The two screw holes H <b> 9 and H <b> 10 are arranged on the side end surface of the transparent glass substrate 27 so as to face each other with a predetermined gap therebetween.

Subsequently, the corresponding screws S1 to S10 are screwed into the respective screw holes H1 to H10, and the screws S1 to S10 are appropriately rotated to adjust the mounting position of the liquid crystal panel 16. I do. Screws S1 to S1
Regarding 0, it may be screwed to the support member 30 in advance before fixing the dichroic prism 23 or before incorporating an integrated component including the liquid crystal panel 16.

The position of the liquid crystal panel 16 is adjusted while viewing the image actually displayed on the screen. As the adjustment procedure, first, the screws S1 to S4 screwed into the four screw holes H1 to H4 are brought into contact with the front surface of the transparent glass substrate 27, and the transparent glass substrate 27 is pressed by the screws S1 to S4. Lightly press against the dichroic prism 23 side. Thus, the polarizing plate 26 is lightly pressed against the light incident surface of the dichroic prism 23. When the screws S5 to S8, S9, and S10 are rotated in this state, the position of the transparent glass substrate 27 fluctuates according to the rotation direction and the amount of rotation of each screw, and the position of the liquid crystal panel 16 fluctuates integrally therewith. I do. Therefore, the mounting position of the liquid crystal panel 16 with respect to the dichroic prism 23 can be adjusted (finely adjusted) in multiple directions.

That is, by appropriately rotating the screws S5 to S8, the mounting position of the liquid crystal panel 16 can be shifted in the left-right direction (FIG. 5).
In the X direction). Also, screws S9,
By appropriately rotating S10, the mounting position of the liquid crystal panel 16 can be adjusted in the vertical direction (Y direction in FIG. 5). Further, by appropriately rotating the screws S5 to S8, S9, and S10, the mounting position of the liquid crystal panel 16 can be adjusted (tilt adjustment) in the rotation direction (the θ direction in FIG. 5).

Incidentally, the number of screws and screw holes may be arbitrarily set as long as the mounting position of the liquid crystal panel 16 can be adjusted in the horizontal direction, the vertical direction, and the rotation direction. Further, with respect to the panel position in the optical axis direction (Z direction in FIG. 5) with respect to the dichroic prism 23, the liquid crystal panel 16 is attached to the light incident surface of the dichroic prism 23 via the polarizing plate 26 and the transparent glass substrate 27 in a close contact state. Thereby, positioning can be performed with high accuracy.
Therefore, panel position adjustment in the optical axis direction becomes unnecessary. Further, it is not necessary to adjust the parallelism of the panel to the light incident surface of the dichroic prism 23.

After adjusting the mounting position of the liquid crystal panel 16 as described above, the liquid crystal panel 16 is fixed to the dichroic prism 23 integrally with the transparent glass substrate 27 by tightening the screws S1 to S4. At this time, the transparent glass substrate 27 may be fixed with screws S1 to S4 using packing or the like. Further, in order to prevent the liquid crystal panel 16 from being displaced due to the loosening of the screw or the like, a screwing portion between the screws S1 to S4 and the support member 30 (in the case where packing is used) using a fixing means such as an instant adhesive or the like. May be reinforced).

As described above, in the liquid crystal projector device according to the second embodiment, the dichroic prism 23
On the other hand, since the liquid crystal panel 16 is configured to be detachably attached by a crimping method using screws, it is possible to easily replace parts. Thereby, for example, even when some trouble occurs in the liquid crystal panel, it is possible to easily cope with replacement of the defective product and reproduction of the liquid crystal panel. In addition, since the integrated component including the polarizing plate 26, the transparent glass substrate 27, the liquid crystal panel 16, and the dust-free plate 28 is not directly bonded to the dichroic prism 23 with an adhesive, the handling in the assembly process is simplified, It is easy to maintain a clean environment, and it is possible to effectively suppress generation of dust and dust.

Further, since a position adjusting mechanism for adjusting the mounting position of the liquid crystal panel is provided, three liquid crystal panels 1 are provided.
The mutual positions of 4, 15, and 16 can be accurately and simply adjusted. This makes it possible to form a good image by accurately matching the red (R), green (G), and blue (B) pixels on the screen.

The method of fixing the liquid crystal panels 14, 15, 16 to the dichroic prism 23 is not limited to the above-mentioned crimping method using screws. For example, an uncured state or a semi-cured state is bonded to the light incident surface of the dichroic prism 23. The transparent glass substrate 27 is pressed together with the polarizing plate 26 via the agent layer, and after adjusting the position of the panel in this state as described above, the adhesive layer is completely cured (fully cured) to fix the panel. It is also possible to employ a bonding method.

Various modifications are also conceivable for the structure for attaching the liquid crystal panels 14, 15, 16 to the dichroic prism 23. For example, as shown in FIG. 6, the dichroic prism 23 and the liquid crystal panel 14,
The phase difference plate 35, the sapphire substrate 3
A structure is conceivable in which these components are integrated in a close contact state with the polarizing plate 37 and the polarizing plate 37 interposed therebetween. In this case, the sapphire substrate 3
6 and the phase difference plate 35 are preferably larger than the liquid crystal panel size in order to increase the thermal conductivity. As shown in FIG. 7, a retardation plate 38 and a polarizing plate 39 are provided between the dichroic prism 23 and each of the liquid crystal panels 14, 15, and 16.
Further, a structure in which these are integrated in a close contact state with the sapphire substrate 40 interposed therebetween is also conceivable.

As another modified example, as shown in FIG. 8, the dichroic prism 23 and each liquid crystal panel 1
4, 15 and 16, a phase difference plate 41, a first sapphire substrate 42, a polarizing plate 43, and a second sapphire substrate 4
4 or a structure in which these are integrated in a close contact state, or as shown in FIG. 9, a first sapphire substrate 45, a retardation plate 46, a polarizing plate 47, and a second sapphire substrate 48. It is also conceivable to have a structure in which are integrated in a close contact state.

Further, by interposing sapphire glass or Tempax glass between optical element substrates such as a polarizing plate and a retardation plate, thermal conductivity can be made uniform. In addition, a transparent conductive film (I
By using a substrate coated with a TO film or the like), an improvement in thermal conductivity can be expected.

In the above embodiment, an example of application to a liquid crystal projector device has been described. However, the present invention is not limited to this, and a liquid crystal having a configuration in which a liquid crystal panel is arranged on a light incident surface of a prism in an opposed state is adopted. It can be applied to all display devices.

[0047]

As described above, according to the present invention, a liquid crystal panel is attached to and integrated with a light incident surface of a prism via a transparent substrate having high thermal conductivity.
The liquid crystal panel can be efficiently cooled without causing a problem due to fan noise and dust winding.
As a result, in a liquid crystal projector device using a liquid crystal panel as a liquid crystal light valve, it becomes possible to project a high-quality image on a screen in a very quiet use environment. Further, since the cooling effect of the liquid crystal panel is enhanced by the integrated structure with the prism, the operating temperature of the liquid crystal panel can be significantly reduced. Further, in order to cope with downsizing of the apparatus, downsizing of the liquid crystal panel accompanying the downsizing, and enhancement of image brightness, it becomes possible to keep the operating temperature of the liquid crystal panel low and maintain high reliability.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of an optical system configuration of a liquid crystal projector device to which the present invention is applied.

FIG. 2 is a top view illustrating an example of a main structure of the liquid crystal projector device according to the first embodiment of the present invention.

FIG. 3 is a partial sectional view of FIG. 2;

FIG. 4 is a partial cross-sectional view illustrating a main configuration of a liquid crystal projector device according to a second embodiment of the invention.

FIG. 5 is an exploded perspective view illustrating a main configuration of a liquid crystal projector device according to a second embodiment of the invention.

FIG. 6 is a plan view (part 1) showing an example of an integrated structure of a prism and a liquid crystal panel.

FIG. 7 is a plan view (part 2) illustrating an example of an integrated structure of a prism and a liquid crystal panel.

FIG. 8 is a plan view (part 3) showing an example of an integrated structure of a prism and a liquid crystal panel.

FIG. 9 is a plan view (part 4) illustrating an example of an integrated structure of a prism and a liquid crystal panel.

[Explanation of symbols]

14, 15, 16 ... liquid crystal panel (liquid crystal light valve),
23: dichroic prism, 27: transparent glass substrate, 29: base plate, 30: support member, H1 to H
10: screw holes, S1 to S10: screws

Continued on the front page F term (reference) 2H088 EA14 EA15 EA19 HA13 HA18 HA21 HA24 MA20 2H091 FA05X FA21X FA41Z FD12 FD15 LA04 MA07 5C058 AB06 BA35 EA01 EA02 EA11 EA26

Claims (13)

[Claims] 1. A liquid crystal display device wherein a liquid crystal panel is attached to and integrated with a light incident surface of a prism via a transparent substrate having high thermal conductivity through a transparent substrate. 2. The liquid crystal display device according to claim 1, wherein at least one interface between said prism, said transparent substrate and said liquid crystal panel is brought into close contact with an adhesive. 3. The liquid crystal panel according to claim 1, wherein the liquid crystal panel is detachably attached to the prism.
The liquid crystal display device as described in the above. 4. The liquid crystal display device according to claim 1, further comprising a position adjusting mechanism for adjusting a mounting position of the liquid crystal panel. 5. The liquid crystal display device according to claim 1, wherein the transparent substrate is an optical element substrate or a glass substrate. 6. The liquid crystal display device according to claim 2, wherein the adhesive is made of a transparent resin having substantially the same refractive index as the prism, the transparent substrate, and the liquid crystal panel. 7. A liquid crystal projector device wherein a liquid crystal panel is attached to and integrated with a light incident surface of a prism via a transparent substrate having high thermal conductivity. 8. The liquid crystal projector device according to claim 7, wherein at least one interface between said prism, said transparent substrate and said liquid crystal panel is brought into close contact with an adhesive. 9. The liquid crystal panel according to claim 7, wherein said liquid crystal panel is detachably attached to said prism.
The liquid crystal projector device as described in the above. 10. The apparatus according to claim 7, further comprising a position adjusting mechanism for adjusting a mounting position of said liquid crystal panel.
The liquid crystal projector device as described in the above. 11. The liquid crystal projector according to claim 7, wherein the transparent substrate is an optical element substrate or a glass substrate. 12. The liquid crystal projector according to claim 8, wherein the adhesive is made of a transparent resin having substantially the same refractive index as the prism, the transparent substrate, and the liquid crystal panel. 13. A panel cooling method, wherein the liquid crystal panel is cooled by attaching and integrating the liquid crystal panel on a light incident surface of a prism via a transparent substrate having high thermal conductivity.