JP3049752B2 - Projection display device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a projection type liquid crystal display device using a liquid crystal light valve for image formation.

[Prior Art] Conventionally, as shown in FIG. 5, a polarizing plate is attached to a glass substrate of a liquid crystal light valve or a polarizing plate alone is attached to a member connected to the liquid crystal light valve via a double-sided tape. The structure was common.

[Problems to be Solved by the Invention] However, in the above-described conventional technology, the unnecessary polarized light component of the light emitted from the light source is absorbed only by the polarizing plate, and the absorbed unnecessary polarized light component is converted into heat. Deterioration of characteristics, thermal deformation, etc., resulting in image deterioration, and heat absorbed by the polarizing plate is conducted to the glass substrate of the liquid crystal light valve to increase the temperature rise of the liquid crystal light valve, thereby inducing poor alignment. There is a problem that it is difficult to guarantee the reliability when the operating environment temperature is high, such as deterioration of the image.

In addition, it is necessary to provide a high-performance cooling device (for example, a blowing fan) for the heat countermeasures. In using the device, it is necessary to secure a large space in design because it emits high noise and the device becomes large. We have to deal with the problem of high price. In particular, the problem of noisy noise has the negative effect of losing a beautiful image, such as when the image is quiet,
This is a problem to be solved. Further, when a high-output light source is used for improving brightness, the above-described problem is further increased, and there is a major disadvantage that the brightness must be sacrificed to reduce the problem.

In addition, when using only a polarizing plate, the light incident efficiency due to surface reflection loss is reduced, which not only leads to a reduction in the brightness of the device, but also a flaky polarizing plate is attached to a member such as a sheet metal via a double-sided tape. Attachment is not only completely fixed, but also has poor attachment accuracy and assemblability, and is also a concern in device design.

Furthermore, when a polarizing plate is attached to a glass substrate of a liquid crystal light valve with an attaching jig such as a roller, excessive force is applied to cause serious damage, and the yield is reduced as a defective product. This is another cause of high prices. Also, at this time, it is highly possible that small scratches are made on the surface of the glass substrate or a polarizing plate is attached while impurities such as dust and hand grease are attached. It is very close to the image display position of the bulb and is enlarged and projected as a shadow on the screen as information near the focal position by the projection lens, causing image deterioration.

Therefore, the present invention is to solve the above-mentioned conventional problems, the purpose is to ensure a wide range of environmental temperature, there is no image degradation, etc., high reliability, easy design, An object of the present invention is to provide a bright, small, low-noise, low-cost projection type liquid crystal display device.

Means for Solving the Problems The present invention provides a projection type including a light source, a light valve that modulates and emits light from the light source, and a projection unit that projects the light modulated by the light valve. In a display device, the light valve includes a light modulating unit and a polarizing plate disposed on a light incident side of the light modulating unit, and a side of the polarizing plate opposite to a surface facing the modulating unit. In terms of
A light transmitting plate having a higher thermal conductivity than this is attached, and the polarizing plate is arranged at a position away from the light modulating means, between the light modulating device and the polarizing plate, and It is characterized by having a cooling device that allows air to flow on the light incident side of the light transmitting plate.

Further, the present invention is a projection display device comprising: a light source; a light valve that modulates and emits light from the light source; and a projection unit that projects light modulated by the light valve. The light valve includes a light modulator, and a polarizing plate disposed on a light emission side of the light modulator,
On the surface of the polarizing plate opposite to the surface facing the modulating means, a light transmitting plate having a higher thermal conductivity is attached, and the polarizing plate is separated from the light modulating means. A cooling device that is disposed at a position and that allows air to flow between the light modulation device and the polarizing plate and to the light exit side of the light transmission plate.

In the above-mentioned projection display device, an anti-reflection film is deposited on the light transmitting plate.

[Operation] In the projection type liquid crystal display device configured as described above, since the thermal conductivity of the glass plate is higher than the thermal conductivity of the polarizing plate, the heat absorbed by the polarizing plate can be released to the light transmitting plate.
Also, when attaching a light transmitting plate to only one side of the polarizing plate,
By arranging the polarizing plate side to be the light modulating unit side, the direction of heat conduction is opposite to the light modulating unit side (the direction away from the light modulating unit). Temperature rise can be reduced. Then, the above-mentioned heat is taken away by the wind generated by the cooling device, and the temperatures of the polarizing plate and the light modulating means are lowered.

Further, by attaching the light transmitting plate to the polarizing plate, reflection occurring on the surface of the polarizing plate can be suppressed, so that the light incidence efficiency can be increased. Further, when a light transmitting plate on which an anti-reflection film is deposited is used, the surface reflection loss of the light transmitting plate can be almost eliminated, so that the light incidence efficiency can be further improved,
A bright device can be realized.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a configuration diagram of an optical system of a projection type liquid crystal display device according to an embodiment of the present invention. FIG. 1 also shows an embodiment in which a glass plate attached to a polarizing plate is arranged on the polarizing plate side on the liquid crystal light valve side.

In FIG. 1, among white light emitted from a light source 1 such as a metal halide lamp, a xenon lamp, a halogen lamp, etc., a heat ray (about 720 nm) is applied by a heat ray cut filter 2.
The light in the above wavelength range is reflected, and other light (about 720 nm)
The following wavelength regions are transmitted. The transmitted light is incident on the light separation optical system 3, and red light (light in a wavelength region from about 590 nm to about 700 nm) is transmitted by the red light transmitting dichroic mirror 4. The transmitted red light is changed its traveling direction by the reflection mirror 5 and is transmitted through the polarizing plate glass 7 to form a polarizing plate.
Unnecessary polarized light components are absorbed at 10 and single polarized light components are selectively transmitted and incident on the red liquid crystal light valve 13. On the other hand, light other than red light (cyan light) is reflected by the red light transmitting dichroic mirror 4 and enters the green light reflecting dichroic mirror 6. The green light reflecting dichroic mirror 6 reflects green light (light in a wavelength region from about 510 nm to about 590 nm) and blue light (about 510 nm) as other light.
Light in the following wavelength range). The reflected green light and the transmitted blue light pass through the polarizing plate glasses 8 and 9, respectively, selectively transmit a single polarization component through the polarizing plates 11 and 12, similarly to the red light, and the liquid crystal light valve 14 for green light. Incident on the blue liquid crystal light valve 15.

Here, the functions of the polarizing plate and the liquid crystal light valve will be described. The liquid crystal light valve serves as a light waveguide as a light modulation element. Simply put, the incident light is changed in form and emitted. The role of this device is to transmit or block light by controlling it electrically. However, since light having an infinite number of polarization planes is mixed in the light source 1, when all of these lights are directly incident on the liquid crystal light valve, the lights of the respective polarization planes are respectively light-modulated and emitted. Cannot transmit or block the light, and cannot fulfill the above role. Therefore,
In order for the liquid crystal light valve to function satisfactorily, it is necessary to select a light component of a single plane of polarization (single polarization component) from the above light. In the case of a single polarization component, only one type of light needs to be modulated, so that transmission and cutoff can be controlled. A polarizing plate is used as a means for selecting the single polarization component. The polarizing plates 10, 11, and 12 are used for selecting a single polarized light component, and the polarizing plates 16, 17, and 18 are used for detecting a polarized light component light-modulated by a liquid crystal light valve. Therefore, the light modulation is normally performed by the combination of the two polarizing plates on the light incident side and the light emitting side and the liquid crystal light valve. Here, since the polarizing plates 10, 11, and 12 selectively transmit only a single polarized light component, they absorb other polarized light components (about 60% of the incident light).
Since the absorbed polarized component (unnecessary polarized component) is converted into heat, the temperature of the polarizing plate must be increased. In addition, polarizing plates 16, 1
7 and 18 denote part or all of the polarized light when the polarization plane direction (polarization axis direction) of the liquid crystal light valves 13, 14 and 15 does not coincide with the polarization plane direction of the liquid crystal light valves 13, 14 and 15. Absorbs and experiences temperature rise. Further, the rise in temperature of each polarizing plate causes the temperature of the liquid crystal light valve between the two polarizing plates to rise due to radiant heat from each polarizing plate. Therefore, by the blower 22 which is a cooling device installed at the lower or upper part of the liquid crystal light valve, the liquid crystal light valves 13, 14, 15 and the polarizers 10, 11, 12 and the polarizers 16, 17, 18 are connected. Between, polarizing plate glass 7, 8, 9
It is necessary to allow air to pass through the light incident side of the substrate and the light exit side of the polarizing plate glasses 19, 20, and 21 to forcibly remove heat.

Next, FIG. 1 will be described. Each color light incident on the liquid crystal light valve for each color is light-modulated as described above, and analyzed by the polarizing plates 16, 17, and 18, and the polarizing plate glass 1
After passing through 9, 20, and 21, the light enters the photosynthetic optical system.
The incident red light is reflected by a green light reflecting dichroic mirror 24.
Then, the light is combined with the green light reflected by the green light reflecting dichroic mirror 24 to become yellow light, and passes through the blue light reflecting dichroic mirror 26. The incident blue light changes its traveling direction by the reflection mirror 25, is reflected by the blue light reflection dichroic mirror 26, and is combined with the yellow light to become white light. The white light synthesized in this manner enters the projection optical system, and is enlarged and projected by a projection lens 27 on a screen (not shown).

In FIG. 1, the position of the light source 1 can be on the extension of the optical axis 28, and the position of the projection lens 27 can be on the extension of the optical axis 32. At this time, the characteristics of the dichroic mirror may be changed so that light separation and photosynthesis are performed smoothly. Furthermore, the liquid crystal light valves for each color 13, 14, 15
Can be freely selected, and it is only necessary to change the characteristics of the four dichroic mirrors corresponding to each position.

FIG. 2 is a detailed view around the liquid crystal light valve of the embodiment of FIG. The thermal conductivity of the polarizing plate glasses 7 and 19 is about
The heat conductivity of the polarizing plates 10 and 16 is about 0.22 kcal / m · h · deg, whereas the heat conductivity is 0.68 kcal / m · h · deg. Accordingly, heat is conducted from the low thermal conductivity polarizers 10 and 16 to the higher thermal conductivity polarizer glasses 7 and 19. Arrows 33 and 34 in the figure indicate the direction of heat conduction, and the direction pointed to is the light separation optical system 3 or the photosynthesis optical system 23 which is opposite to the liquid crystal light valve side. That is, it is clear that the temperature rise of the liquid crystal light valve 13 is greatly reduced. As described above with reference to FIG. 1, the wind from the blower fan 22 installed below or above the liquid crystal light valve (the lower part in FIG. 2) causes the liquid crystal light valve 13, the polarizing plates 10 and 16 to be polarized. Arrows 35, 36, 37, and 38 show how heat is forcibly removed from the glass sheets 7 and 19 as they pass through the area. As described above, the heat to be forcibly taken away is reduced by the reduced temperature rise. Therefore, the capacity of the cooling device can be reduced, and a small-sized, low-noise, inexpensive blower fan can be used. This is because of the miniaturization and low noise of the projection type LCD,
This leads to lower prices and facilitates device design. In addition, since the cooling capacity of the cooling device can be sufficient, the output of the light source can be increased, and a bright device can be realized.

FIG. 3 shows details of the surface reflection loss of the liquid crystal light valve, the polarizing plate, and the polarizing plate glass. When light passes between media having different refractive indices, it reflects at the interface (surface of the medium) and loses incident light. The loss depends on the incident angle of light, the refractive index of the medium, the surface state, etc., but the surface reflection loss is R, the refractive index of the medium on the light incident side is n0,
Assuming that the refractive index of the medium on the light incident side is n1, the approximate surface reflection loss R when light is incident at right angles is: It can be expressed as. Therefore, as the ratio of the refractive indices is larger,
The surface reflection loss increases. In FIG. 3A, when the incident light enters the polarizing plate glass 7 from the air layer, surface reflection loss 101 occurs, and the polarizing plate 10
Between the surface reflection loss 102 when entering the adhesive layer, the surface reflection loss 103 when entering the polarizing plate 10, the surface reflection loss 103 when entering the adhesive layer again, and when entering the glass plate 42. A surface reflection loss 102 occurs when the light enters the air layer, and a surface reflection loss 104 occurs when the light further enters the liquid crystal light valve 13. Fig. 3 [B]
3A, the process up to the surface reflection loss 103 when the light enters the polarizing plate 10 is the same as that in FIG. 3A. Thereafter, the surface reflection loss 105 occurs when the light enters the air layer, and the liquid crystal light valve 13 , A surface reflection loss 104 occurs.
In FIG. 3C, when the incident light is incident on the polarizing plate 10, a surface reflection loss 105 occurs, and when the incident light is incident on an air layer, the surface reflection loss 105 occurs.
When the light is incident on 3, a surface reflection loss 104 occurs. In any of the above cases, the light emitted from the liquid crystal light valve 13 is
Through the reverse process to the incidence, each surface reflection loss occurs. Since an antireflection film is deposited on the polarizing plate glass 7, the surface reflection loss 101 is R (101) = 0 (2). The refractive index of the air layer is 1.00. Here, the refractive index of the polarizing plate glass 7 is 1.52, the refractive index of the adhesive layer is 1.48, and the refractive index of the polarizing plate 10 is 1.49. Then, the respective surface reflection losses are as follows: R (102) = 1.78 × 10 ^-4 (3) R (103) = 0.11 × 10 ^-4 (4) R (105) = 0.039 ... (5) From the results of the above equations (1) to (5), the total surface reflection loss until the light enters the air layer immediately before the liquid crystal light valve 13 is R (FIG. 3A) = 3.78 × 10 ^−4. (6) R (FIG. 3 [B]) = 0.0392 (7) R (FIG. 3 [C]) = 0.078 (8) As can be seen from the equations (6), (7) and (8), the surface reflection loss is reduced to about half by attaching a glass plate on which an antireflection film is deposited to the polarizing plate, as compared with the case of using the polarizing plate alone. can do. Further, when a glass plate on which an antireflection film is deposited is attached to both surfaces of the polarizing plate, the surface reflection loss can be reduced by orders of magnitude, and is close to zero. Since there is the above-mentioned surface reflection loss even before the light passes through the liquid crystal light valve 13 and enters the photosynthetic optical system 23, the polarizing plate alone and the glass plate on which the antireflection film is deposited are attached to one side of the polarizing plate. Or the difference in surface reflection loss when pasting on both sides,
Appears more prominently. Therefore, a brighter projection type liquid crystal display device can be realized.

FIG. 4 shows a configuration diagram of an optical system of a projection type liquid crystal display device according to another embodiment of the present invention. In the figure, the same components as those in FIG. 1 are denoted by the same reference numerals. The process until light passes through the heat ray cut filter 2 from the light source 1 is the same as in the above-described embodiment. The transmitted white light is transmitted through the polarizing plate glass 7, the single polarized light component is selectively transmitted by the polarizing plate 10, and enters the light separation optical system 3. The light-polarized components of each color are separated into the liquid crystal light valves 13 and 1 for each color.
The light is modulated by 4 and 15 and is incident on the photosynthetic optical system 23.
The white light that has undergone photosynthesis is analyzed by the polarizing plate 16, passes through the polarizing plate glass 19, and is enlarged and projected on the screen by the projection lens 27. In this, the processes in the light separation optical system 3 and the photosynthesis optical system 23 are the same as those in the above-described embodiment, and thus the description is omitted. By arranging the polarizing plate 10 and the polarizing plate glass 7 at the entrance of the light separating optical system 3 and the polarizing plate 16 and the polarizing plate glass 19 at the exit of the photosynthetic optical system 23, each color is more than the same as the embodiment of FIG. The temperature rise of the liquid crystal light valve can be reduced.

[Effects of the Invention] As described above, the projection display device of the present invention attaches a polarizing plate to a light transmitting plate having a higher thermal conductivity than this,
It is arranged at a position away from the light modulation means, between the light modulation device and the polarizing plate, and by providing a cooling device that allows air to flow on the opposite side of the light transmission plate from the polarization plate, by a simple structure,
The temperature rise of the polarizing plate and the light modulator can be reduced.

In addition, the temperature rise of the light modulation device can be reduced without disposing the polarizing plate on the light modulation device and by arranging the glass plate attached to the polarization plate so that the polarization plate side is the light modulation device side. It becomes possible. This reduction in temperature rise prevents deterioration of the image quality due to deterioration of the polarization characteristics of the polarizing plate, thermal deformation, and malfunction of the light modulation device, so that the guaranteed range of the environmental temperature can be widened and the reliability of the device increases, as well as cooling. The capacity of the device can be reduced. Lowering the capacity means that a small, low-noise and inexpensive blower fan can be used, and this leads to a reduction in the size, constant noise, and lower cost of the projection display device. In addition, this reduction in temperature rise has the effect that the cooling device has a margin in cooling capacity, the output of the light source can be increased accordingly, and the device can be brightened. In addition, the downsizing of the cooling device does not affect the other components in terms of space, thereby facilitating the design.

In addition, by adopting a structure in which a light transmitting plate is attached to a polarizing plate, it becomes a part with a certain level of mechanical strength from a flake-like part, it can be completely fixed, the mounting accuracy is improved, and the assemblability is good. is there. Therefore, the design is also easy from this point.

Further, the yield is improved without disposing the polarizing plate on the light modulating means, and arranging the polarizing plate at a position distant from the light modulating means and sticking the polarizing plate on the light transmitting plate. This also contributes to lowering the price of the apparatus. Further, since the light modulating means can be prevented from being damaged, the state in which impurities remain adhered, and the like, there is obtained an effect that there is no image deterioration and the reliability of the projection display device can be further increased. Furthermore, since the light transmitting plate is directly cooled by the cooling means, the temperature rise of the polarizing plate can be reduced very efficiently.

Further, by attaching a light transmitting plate on which an anti-reflection film is deposited to one surface of the polarizing plate, the surface reflection loss of light can be suppressed, the light incidence efficiency can be increased, and a bright device can be realized.

[Brief description of the drawings]

FIG. 1 is a structural view of an optical system of a projection type liquid crystal display device according to one embodiment of the present invention, FIG. 2 is a detailed view around the liquid crystal light valve of FIG. 1, and FIG. Detailed illustration of surface reflection loss of polarizing plate and polarizing plate glass, FIG.
FIG. 5 is a configuration diagram of an optical system of a projection type liquid crystal display device according to another embodiment of the present invention, and FIG. 5 is a configuration diagram of an optical system of a conventional projection type liquid crystal display device. 1 light source 3 light separation optical system 7,8,9,19,20,21,42,43 polarizing plate glass 10,11,12,16,17,18 polarizing plate 13,14,15 Liquid crystal light valve 22 Air blower 23 Photosynthesis optical system 27 Projection lens 28, 32 Optical axis 33, 34 Heat transfer direction 35, 36, 37, 38 Wind flow 101, 102, 103, 104, 105 ...... Surface reflection loss

Claims (3)

(57) [Claims] 1. A projection display device comprising: a light source; a light valve that modulates and emits light from the light source; and a projection unit that projects light modulated by the light valve, wherein the light is The valve includes a light modulating means, and a polarizing plate disposed on the light incident side of the light modulating means. The surface of the polarizing plate opposite to the surface facing the modulating means has a higher heat than the light modulating means. A light transmitting plate having high conductivity is attached, and the polarizing plate is disposed at a position distant from the light modulation unit, between the light modulating device and the polarizing plate, and of the light transmitting plate. A projection display device comprising a cooling device that allows air to flow on a light incident side. 2. A projection display apparatus comprising: a light source; a light valve that modulates and emits light from the light source; and a projection unit that projects the light modulated by the light valve. The valve includes a light modulating means and a polarizing plate disposed on the light emitting side of the light modulating means. The surface of the polarizing plate opposite to the surface facing the modulating means has a higher heat than the light modulating means. A light transmitting plate having high conductivity is attached, and the polarizing plate is disposed at a position distant from the light modulation unit, between the light modulating device and the polarizing plate, and of the light transmitting plate. A projection display device, comprising: a cooling device that passes air to a light emission side. 3. The projection display according to claim 1, wherein an anti-reflection film is deposited on the light transmitting plate.