JP3389541B2 - Projection display device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection type liquid crystal display device using a liquid crystal light valve for image formation.

[0002]

2. Description of the Related 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 general.

[0003]

However, in the above-mentioned conventional technique, since the unnecessary polarization component of the light emitted from the light source is absorbed only by the polarizing plate and the absorbed unnecessary polarization component is converted into heat, Image deterioration due to deterioration of characteristics and thermal deformation, 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, which induces alignment failure. There is a problem that it is difficult to guarantee reliability when the operating environment temperature is high, such as image deterioration.

In order to take measures against the heat, it is necessary to provide a high-performance cooling device (for example, a blower fan). When using the cooling device, a high noise is generated, and the device becomes large in size. There is also the issue of high prices that must be secured. In particular, the problem of producing high noise is a problem to be solved, which causes an adverse effect of ruining a beautiful image, such as an image of a quiet scene. Further, when a high-output light source is used for improving the brightness, the above-mentioned problem is further expanded, and there is a big drawback that the brightness must be sacrificed in order to reduce the problem.

When using only the polarizing plate,
Not only does the light incidence efficiency due to surface reflection loss decrease, which leads to a reduction in the brightness of the device, but attaching a thin polarizing plate to a member such as sheet metal via double-sided tape is not only a perfect fixing method, but also a mounting method. The accuracy and assemblability are also poor, and this is a concern in the device design.

Furthermore, when a polarizing plate is stuck to a glass substrate of a liquid crystal light valve with a sticking jig such as a roller, too much force is applied to cause great damage, and the yield is reduced as a defective product. , Is another reason why the device becomes expensive. At that time, there is a high possibility that the glass substrate surface will be scratched or the polarizing plate will be stuck with impurities such as dust and oil on the hands. It is very close to the image display position of the bulb, and is projected as a shadow on the screen as information near the focal position by the projection lens.
This is a cause of image deterioration.

Therefore, the present invention solves the above-mentioned conventional problems, and its purpose is to provide a wide range of guaranteed environmental temperature, no image deterioration, and the like, which is highly reliable and easy to design. Therefore, it is an object of the present invention to provide a projection type liquid crystal display device which is bright, compact, low in noise and low in cost.

[0008]

A projection type display device of the present invention comprises a light source, a light valve for modulating and emitting light from the light source, and a projection means for projecting the light modulated by the light valve. A projection display device comprising:
The light valve includes a light modulating unit and a polarizing plate arranged on a light incident side of the light modulating unit, and the polarizing plate is
The light transmitting plate is arranged at a position distant from the light modulating means, and a light transmitting plate is attached to both surfaces of the polarizing plate, an antireflection film is vapor-deposited on one surface of the light transmitting plate, and The non-vapor-deposited surface side is attached to the polarizing plate.

Further, the projection type display device of the present invention comprises a light source, a light valve for modulating and emitting the light from the light source, and a projection means for projecting the light modulated by the light valve. In the display device, the light valve includes a light modulator, an incident side polarization plate disposed on a light incidence side of the light modulation unit, and an emission side polarization arranged on a light emission side of the light modulation unit. A plate, the emission side polarizing plate is arranged at a position away from the light modulating means, a light transmitting plate is attached to both surfaces of the emission side polarizing plate, and one side of the light transmitting plate is provided. An antireflection film is vapor-deposited, and the non-vapor-deposited surface side of the light transmission plate is attached to the emission side polarizing plate.

[0010]

Further, the thermal conductivity of the light transmitting plate is set higher than the thermal conductivity of the polarizing plate to which the light transmitting plate is attached, and a cooling device for cooling each of the light transmitting plates is further provided. It is characterized by having.

[0012]

In the projection type display device having the above-described structure, by attaching the light transmitting plate to the polarizing plate, it is possible to suppress the reflection that has occurred on the surface of the polarizing plate, so that the light incident efficiency can be improved. Further, by attaching the light transmitting plates to both surfaces of the polarizing plate, not only one surface but also both surface reflections can be suppressed, so that the light incident efficiency can be further enhanced.

Further, when the light transmitting plate having the antireflection film deposited thereon is used, the surface reflection loss of the light transmitting plate can be substantially eliminated, so that the light incident efficiency can be further improved.
A bright device can be realized.

[0014]

Further, since the heat conductivity of the light transmitting plate is higher than that of the polarizing plate, the heat absorbed by the polarizing plate can be released to the light transmitting plate.

By attaching the light transmitting plates to both sides of the polarizing plate, the heat can be released from two sides, so that the temperature rise can be further reduced.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings.

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

In FIG. 1, of the white light emitted from a light source 1 such as a metal halide lamp, a xenon lamp, a halogen lamp or the like, heat rays (light in a wavelength range of about 720 nm or more) are reflected by a heat ray cut filter 2, and other light rays are reflected. (Light in the wavelength range of about 720 nm or less) is transmitted. The transmitted light is incident on the light separation optical system 3 and is transmitted by the red light transmitting dichroic mirror 4 to the red light (from about 590 nm to about 7 nm).
Light in the wavelength range up to 00 nm) is transmitted. The transmitted red light changes its traveling direction by the reflection mirror 5, is transmitted through the polarizing plate glass 7, and the unnecessary polarizing component is absorbed by the polarizing plate 10.
Liquid crystal light valve for red 1 that selectively transmits a single polarization component
It is incident on 3. On the other hand, the red light transmitting dichroic mirror 4 reflects light other than red light (cyan color light) and makes it incident on the green light reflecting dichroic mirror 6.
The green light reflecting dichroic mirror 6 has a green light (about 51
It reflects light in the wavelength range from 0 nm to about 590 nm) and transmits blue light (light in the wavelength range of about 510 nm or less) which is the other light. The reflected green light and the transmitted blue light are
Similar to the above-mentioned red light, the light is transmitted through the polarizing plates 8 and 9, respectively, and the single polarized component is selectively transmitted by the polarizing plates 11 and 12, and is incident on the green liquid crystal light valve 14 and the blue liquid crystal light valve 15.

The functions of the polarizing plate and the liquid crystal light valve will be described below. The liquid crystal light valve serves as a light waveguide as a light modulation element. Simply speaking, the form of incident light is changed 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 directly enter the liquid crystal light valve, the lights of the respective polarization planes are optically modulated and emitted. The light cannot be transmitted or blocked and cannot fulfill the above-mentioned role. Therefore, in order for the liquid crystal light valve to function satisfactorily, it is necessary to select the light component of a single plane of polarization (single polarization component) from the above lights. If it is a single polarization component,
Since it is only necessary to modulate one type of light, it is possible to control transmission and blocking. A polarizing plate is used as a means for selecting the single polarization component. Polarizing plates 10, 11, 1
Reference numeral 2 is used for selection of a single polarization component, and polarizing plates 16, 17, and 18 are used for detection of polarization component optically modulated by the 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 polarization component, they absorb other polarization components (about 60% of 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, the polarization plates 16, 17, and 18 are polarized when the polarization plane direction (polarization axis direction) of itself is not coincident with the polarization plane direction of the polarization light modulated by the liquid crystal light valves 13, 14, and 15. Part of or all of is absorbed and the temperature rises. Further, the temperature rise of each polarizing plate causes the temperature rise of the liquid crystal light valve between the two polarizing plates due to the radiant heat from each polarizing plate. Therefore, by the blower fan 22 which is a cooling device installed below or above the liquid crystal light valves, the liquid crystal light valves 13, 14, 15 and the polarizing plates 10, 11, 12 are provided.
, And between the polarizing plates 16, 17, and 18, the light incident sides of the polarizing plates 7, 8, and 9 and the polarizing glasses 19, 20, and 2.
It is necessary to pass air through the light emitting side of No. 1 to forcibly remove heat.

Continuing with FIG. Each color light incident on the liquid crystal light valve for each color is optically modulated as described above and detected by the polarizing plates 16, 17, and 18.
After passing through the polarizing plate glasses 19, 20, and 21, the light enters the photosynthesis optical system 23. The incident red light is transmitted through the green light reflecting dichroic mirror 24 and then combined with the green light reflected by the green light reflecting dichroic mirror 24 to become yellow light, and the blue light reflecting dichroic mirror 26.
Through. The incident blue light changes its traveling direction by the reflection mirror 25, and the blue light reflection dichroic mirror 26
Is reflected, and is combined with the above yellow light to become white light. The white light combined in this way enters the projection optical system, and is enlarged and projected by a projection lens 27 onto a screen (not shown in the drawing).

In FIG. 1, the position of the light source 1 is the optical axis 2
8 is also possible, and the position of the projection lens 27 is also possible on the extension of the optical axis 32. At that time, the characteristics of the dichroic mirror may be changed so that the light separation and the light combination are smoothly performed. Further, the positions of the liquid crystal light valves 13, 14, 15 for each color can be freely selected, and the characteristics of the four dichroic mirrors need only be changed correspondingly.

FIG. 2 shows a detailed view around the liquid crystal light valve of the embodiment of FIG. The thermal conductivity of the polarizing plate glass 7 and 19 is about 0.68 kcal / m · h · deg, whereas the polarizing plate 1
The thermal conductivity of 0 and 16 is about 0.22 kcal / m · h · deg. Therefore, heat is generated from the polarizing plates 10 and 16 having low thermal conductivity and the polarizing glass plates 7 and 19 having higher thermal conductivity.
Conduct to. Arrows 33 and 34 in the figure represent the heat conduction direction, and the pointing direction is the light separation optical system 3 or the photosynthesis optical system 23 side, which is the direction opposite to the liquid crystal light valve side. That is, it is obvious that the temperature rise of the liquid crystal light valve 13 is greatly reduced. As described above with reference to FIG. 1, the blower fan 2 installed below or above the liquid crystal light valve (bottom in FIG. 2).
When the wind from 2 passes around the liquid crystal light valve 13, the polarizing plates 10 and 16 and the polarizing plate glasses 7 and 19,
Arrow 3 shows how heat is forcibly taken from them and flows out.
5, 36, 37, 38. This heat to be forcibly taken is, as explained above, due to the reduced temperature rise,
Less. Therefore, it is possible to reduce the capacity of the cooling device, and it is possible to use a small-sized, low-noise and inexpensive blower fan. This leads to downsizing, noise reduction and cost reduction of the projection type liquid crystal display device, and the device design becomes easy. Further, since the cooling capacity of the cooling device can be afforded, 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 causes reflection at the interface (surface of the medium), and the incident light is lost. 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, and the refractive index of the medium of the light incident example is n1. Then, the approximate surface reflection loss R when light is incident at right angles is

[0025]

[Equation 1]

It can be expressed as Therefore, the larger the refractive index ratio, the larger the surface reflection loss. In FIG. 3A, when the incident light enters the polarizing plate glass 7 from the air layer, the surface reflection loss 101 occurs and the polarizing plate glass 7
Surface reflection loss 102 when entering the adhesive layer between the polarizing plate 10 and the polarizing plate 10, and surface reflection loss 1 when entering the polarizing plate 10
03, surface reflection loss 10 even when incident on the adhesive layer again
3, the surface reflection loss 102 when entering the glass plate 42,
Furthermore, surface reflection loss 101 occurs when entering the air layer, and surface reflection loss 104 occurs when entering the liquid crystal light valve 13. In FIG. 3B, the polarizing plate 1
The process up to the surface reflection loss 103 when entering 0 is the same as that in FIG. 3A, and thereafter, when entering the air layer, surface reflection loss 105 occurs, and when entering the liquid crystal light valve 13. Surface reflection loss 104 occurs. Also, FIG.
In [C], when incident light enters the polarizing plate 10, surface reflection loss 105 occurs, and when incident light enters the air layer, surface reflection loss 105 also occurs, and the liquid crystal light valve 1
The surface reflection loss 104 occurs when the light enters the No. 3 plane. In any of the above cases, the light emitted from the liquid crystal light valve 13 undergoes a process opposite to that when the light is incident, and each surface reflection loss occurs. Since the antireflection film is vapor-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, where the refractive index of the polarizing plate glass 7 is 1.52, and the refractive index of the adhesive layer is
1.48, and the refractive index of the polarizing plate 10 is 1.49. Therefore, when substituting into the equation (1), the surface reflection loss of each is 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 before entering the air layer immediately before the liquid crystal light valve 13 is R (FIG. 3 [A]) = 3.78 × 10 ⁻⁴・ ・ ・ (6) R (Fig. 3 [B]) = 0.0392 ・ ・ ・ ・ (7) R (Fig. 3 [C]) = 0.078 ・ ・ ・ ・ (8) is there. As can be seen from the equations (6), (7), and (8), the surface reflection loss is reduced to about half by attaching the glass plate on which the antireflection film is vapor-deposited to the polarizing plate as compared with the case of the polarizing plate alone. can do. Furthermore, when glass plates having an antireflection film deposited thereon are attached to both surfaces of the polarizing plate, the surface reflection loss can be reduced by an order of magnitude, which is close to zero. Since there is the above-mentioned surface reflection loss until the light passes through the liquid crystal light valve 13 and enters the photosynthetic optical system 23, the glass plate on which the antireflection film is vapor-deposited is used when the polarizing plate is used alone. Alternatively, the difference in the surface reflection loss when sticking to both surfaces becomes more remarkable. Therefore, a brighter projection type liquid crystal display device can be realized. FIG. 4 is a block 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 parts as those in FIG. 1 are designated by the same reference numerals. The process until the light passes from the light source 1 to the heat ray cut filter 2 is the same as in the above-described embodiment. The transmitted white light passes through the polarizing plate glass 7, the single polarized component is selectively transmitted by the polarizing plate 10, and enters the light separation optical system 3. The color-separated polarization components of the respective lights are light-modulated by the liquid crystal light valves 13, 14 and 15 for the respective colors, and enter the photosynthesis optical system 23. The photosynthesized white light 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. Among these, the processes in the light splitting optical system 3 and the photosynthesis optical system 23 are
The description is omitted because it is similar to the above-described embodiment. The polarizing plate 10 and the polarizing plate glass 7 are provided at the entrance of the light separation optical system 3.
By arranging the polarizing plate 16 and the polarizing plate glass 19 at the exit of the photosynthetic optical system 23, the temperature rise of the liquid crystal light valve for each color can be reduced more than that of the embodiment of FIG.

[0027]

As described above, the projection type liquid crystal display device of the present invention can reduce the temperature rise of the polarizing plate by the very simple structure of attaching the light transmitting plate to the polarizing plate. Further, by attaching the light transmitting plates to not only one surface but also both surfaces of the polarizing plate, there are two surfaces that radiate heat, so that the temperature rise can be further reduced. Further, by disposing the polarizing plate on the liquid crystal light valve without attaching it, it is possible to reduce the temperature rise of the liquid crystal light valve. This reduction in temperature rise prevents deterioration of the polarization characteristics of the polarizing plate, thermal deformation, and deterioration of image quality due to poor alignment of the liquid crystal light valve, so that the environmental temperature guarantee range can be expanded, increasing the reliability of the device, and cooling the device. The capacity of the device can be reduced. The reduction in capacity means that a blower fan that is small, low in noise and inexpensive can be used, which leads to downsizing, noise reduction and cost reduction of the projection type liquid crystal display device. In addition, this reduction in temperature rise has an effect that the cooling device has a margin in cooling capacity, the output of the light source can be increased correspondingly, and the device can be brightened. And
The miniaturization of the cooling device simplifies the design because it does not affect other components in space.
Also, by adopting a structure in which a light transmitting plate is attached to the polarizing plate,
From a thin piece, it becomes a part with some mechanical strength, can be completely fixed, the mounting accuracy is improved, and the assemblability is good. Therefore, the design is easy also from this point. Further, by attaching the light transmitting plate having the antireflection film deposited thereon to both surfaces of the polarizing plate, the surface reflection loss of light can be suppressed, the light incident efficiency is increased, and a bright device can be realized. Furthermore, by attaching the polarizing plate to the light transmitting plate that is away from the liquid crystal light valve without attaching the polarizing plate to the glass substrate of the liquid crystal light valve, the yield is improved without treating the liquid crystal light valve as a defective product. This point also contributes to the cost reduction of the device. Furthermore, it is possible to avoid scratching the glass substrate of the liquid crystal light valve, avoiding a state where impurities remain attached, and the like, so that there is no image deterioration and the reliability of the projection type liquid crystal display device can be further increased. .

[Brief description of 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. 2 is a detailed view around the liquid crystal light valve of FIG.

FIG. 3 is a detailed explanatory diagram of surface reflection loss of a liquid crystal light valve, a polarizing plate and a polarizing plate glass.

FIG. 4 is a configuration diagram of an optical system of a projection type liquid crystal display device according to another embodiment of the present invention.

FIG. 5 is a configuration diagram of an optical system of a conventional projection type liquid crystal display device.

[Explanation of symbols]

1 ... Light source 3 ... Light separation optical system 7, 8, 9, 19, 20, 21, 42, 43 ... Polarizing glass 10, 11, 12, 16, 17, 18, ... Polarizing plates 13, 14, 15 ... Liquid crystal light valve 22 ... Blower fan 23 ... ... Photosynthesis optical system 27 ... Projection lenses 28, 32 ... Optical axes 33, 34 ... Heat conduction directions 35, 36, 37 , 38 ・ ・ ・ ・ Wind flow 101, 102, 103, 104, 105 ・ ・ ・ Surface reflection loss

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI H04N 5/74 H04N 5/74 K (56) References JP-A 64-28619 (JP, A) JP-A 1-105216 ( JP, A) JP-A-1-158480 (JP, A) Actual opening Flat 2-69316 (JP, U) Actual opening Sho 61-29578 (JP, U) Actual opening Sho 61-86702 (JP, U) Actual opening Showa 62-193289 (JP, U) Actually open 2-102502 (JP, U) Patent 3049752 (JP, B2)

Claims (3)

(57) [Claims] 1. A projection type display device 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 bulb includes a light modulating unit and a polarizing plate arranged on the light incident side of the light modulating unit, the polarizing plate is arranged at a position distant from the light modulating unit, and on both surfaces of the polarizing plate, A light-transmitting plate is attached, an antireflection film is vapor-deposited on one surface of the light-transmitting plate, and the non-vapor-deposited surface side of the light-transmitting plate is attached to the polarizing plate. Type display device. 2. 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 the light modulated by the light valve. The bulb includes a light modulator, an incident side polarization plate arranged on the light incidence side of the light modulation unit, and an emission side polarization plate arranged on the light emission side of the light modulation unit. The plate is arranged at a position distant from the light modulator, both sides of the emission side polarizing plate, a light transmitting plate is attached, an antireflection film is vapor-deposited on one surface of the light transmitting plate, and The projection display device, wherein the non-vapor-deposited surface side of the light transmitting plate is attached to the emission side polarizing plate. 3. The thermal conductivity of the light transmitting plate according to claim 1, wherein the thermal conductivity of the light transmitting plate is set higher than the thermal conductivity of a polarizing plate to which the light transmitting plate is attached. A projection type display device further comprising a cooling device for cooling the liquid crystal display device.