JPH0310218A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To obtain the liquid crystal display device which is reliable under broad environmental temperature conditions by providing a polarization beam splitter between a light source and a light separating means, and providing a cooling fan independently in the common flow passage of wind between a liquid crystal light valve and a light source and an air suction hole in the enclo sure of the liquid crystal light valve. CONSTITUTION:The polarization beam splitter 2 is provided between the light source 1 and light separating means 3. Further, the cooling fan 15 is provided independently on the flow passage of wind used in common between the liquid crystal light valve 7 and light source 1 and the suction hole 16 for the wind is provided on the upper or lower enclosure of the liquid crystal light valve 7. Light emitted by the light source 1 is sent to the polarization beam splitter 2 to extract only a necessary polarized component, so unnecessary polarized components are hardly made incident on the light separating means 3. Air sucked from below or above the light valve 7 is discharged while absorbing heat from the liquid crystal light valve 7, light source 1, and polarization beam splitter 2. Consequently, the inexpensive liquid crystal display device which is reliable under broad environment temperature conditions is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid crystal display device using a liquid crystal light valve.

[Prior Art] FIG. 8 is a configuration diagram showing an optical system of a conventional liquid crystal display device. Conventionally, the light emitted from the light source 1 is directly transmitted to the light separating means 21.
and is separated into the three primary colors of red, green, and blue by the light separation means 21, and the liquid crystal light valve 22R corresponding to the three primary colors
, 22G, 22B, the light is modulated by the light combining means 23
There has been known a liquid crystal display device in which an enlarged image is projected onto the screen 12 in front by a rear projection lens 28 which is synthesized by the following. The liquid crystal light valves 22R, 22G, and 22B have polarizing plates 24 and 25 at the front and rear thereof, respectively, and the P polarized light component or the S polarized light component of the light is selectively transmitted by the incident side polarizing plate 24, and the liquid crystal light valves 22R, 22G , 22B, the light is selectively transmitted again by the output-side polarizing plate 25 to enable image display.

[Problem to be solved by the invention] However, in the conventional technology, P out of the light emitted from the light source 1
Polarized light components and S-polarized light components are taken into the light separating means 2], and unnecessary polarized light components are absorbed by the incident side polarizing plates 24 of the liquid crystal light valves 22R and 220° 22B. The incident-side polarizing plate 24 that absorbed the heat is transferred to the liquid crystal light valves 22R and 22 as shown in FIG.
Since it is installed just before G and 22B, LCD light valve 2
Since the heat conduction to 2R, 22G, and 22B is remarkable, in order to maintain reliability under a wide range of environmental temperature conditions, a high-speed cooling fan 26 with high cooling capacity is installed on the polarizing plate 2 as shown in Fig. 8.
4 and 25, liquid crystal light valves 22R, 22G, 22B
It was necessary to install it in the immediate vicinity of On the other hand, a halogen lamp, a metal halide lamp, etc. are used as the light source 1.
In order to achieve a long life as a light source, optimal color characteristics, etc., it was necessary to provide a cooling fan 27 nearby as shown in FIG. 8. When two cooling fans are used as described above, it is difficult to design the layout due to the mutual flow of air, and a corresponding structure is required for the housing and circuit design. Furthermore, a high-speed cooling fan is not suitable for use in today's AV-oriented liquid crystal display devices because it produces noise corresponding to the number of rotations.

The liquid crystal display device of the present invention solves the above problems.
The objective is to provide a low-cost liquid crystal display device that is highly reliable under a wide range of environmental temperature conditions, has low noise, is compatible with today's AV trends, and facilitates layout and housing 9 circuit design. be.

[Means for Solving the Problems] In order to solve the above problems, the liquid crystal display device of the present invention has the following features:
a light source, a light separation means for separating light from the light source, a liquid crystal light valve for modulating the light from the light separation means, and a light synthesis means for combining the modulated light from the liquid crystal light valve;
A liquid crystal display device having a projection lens for projecting light from a light synthesizing means, a cooling fan for cooling a liquid crystal light valve and a light source, characterized in that a polarizing beam splitter is provided between the light source and the light separating means. .

Further, the polarizing beam splitter is characterized in that a plurality of glass plates are stacked in parallel so that the large angle of incidence on the glass plates is the Frewster angle.

Further, the present invention is characterized in that a cooling fan is used alone in a common air flow path between the liquid crystal light valve and the light source, and the air intake hole is provided in the housing below or above the liquid crystal light valve.

[Function] In the liquid crystal display device configured as described above, before the light emitted from the light source enters the light separation means, only the necessary polarized light components are extracted by the polarizing beam splitter, and the unnecessary polarized light components are extracted by the light separation means. Almost no components are incident.

Also, the air taken in from below or above the liquid crystal light valve cools the liquid crystal light valve and the surface of the polarizing plate around it, removes the heat from the light source and polarizing beam splitter, and is emitted to the outside of the cooling fan. .

[Example] Examples of the present invention will be described below based on the drawings. 1st
The figure is a configuration diagram of an optical system in an embodiment of the present invention.

In FIG. 1, light emitted from a light source 1 enters a polarizing beam splitter 2, and at the reflecting surface of the polarizing beam splitter 2, the P (S) polarized light component is transmitted and the S (P) polarized light component is reflected.

The P(S) polarized light component transmitted through the polarizing beam splitter 2 enters the light splitting means 3, where the blue light (light of approximately 500 nm or less) is reflected by the blue reflecting dichroic mirror 4, and the other light (yellow light) is reflected. ). The reflected blue light changes direction by the reflection mirror 5 and enters the blue liquid crystal light valve 7B.

The light transmitted through the blue reflecting dichroic mirror 4 enters the red transmitting dichroic mirror 6, where it becomes green light (approximately 500
It reflects red light (light between about 600 nm and about 600 nm) and transmits other light (light about 600 nm or more). The reflected green light enters the green liquid crystal light valve 7G, and the transmitted red light enters the red liquid crystal light valve 7R.
incident on . The incident color light is transmitted through the liquid crystal light valve 7R.
, 7G, and 7B, the blue light enters the light combining means 8, and the blue light passes through the blue-transmitting dichroic mirror 9 to the red-transmitting dichroic mirror 10.
The green light is reflected by the blue-transmitting dichroic mirror 9.
The red light is reflected by the red-transmitting dichroic mirror 10, and the red light is reflected by the reflecting mirror 5 and then transmitted through the red-transmitting dichroic mirror 10.

The light color-combined as described above enters the projection lens 11 and is enlarged and projected onto the screen 12 in front.

The liquid crystal light valves 7R, 7G, and 7B enable image display by receiving selection of polarization components by polarizing plates 13 and 14 located before and after each, and the polarizing plate 13 is used as an auxiliary polarizing plate for the polarizing beam splitter 2. For,
It is not necessary if the degree of polarization of the polarizing beam splitter 2 is close to 100%.

FIG. 2 shows an embodiment of the polarizing beam splitter 2. The polarizing beam splitter 2 is generally a cuuff-shaped one in which the slopes of a pair of right-angled prisms are glued together, and since a degree of polarization of about 98% can be achieved, the polarizing plate 13 is not necessary, but it is expensive. I end up. The polarizing beam splitter shown in FIG. 2 is a low-cost device, and its principle will be explained in FIG. 3. In FIG. 3, the refractive index of the glass plate 17 is n, the incident angle of light is θ, and θ=ja
When the glass plate 17 is provided in the relationship n−'n, the P polarized light component 18
is transmitted 100%, and approximately 15% of the S-polarized component 19 is reflected. (θ at this time is the Frewster angle.) Therefore, if a plurality of glass plates 17 are stacked in parallel and configured as shown in FIG. 2, ideally the P polarized light component 18 will be 1
00% transmission, and 100% S polarization component 19 is reflected. In actual measurements, if the horizontal axis is the number of 170 glass plates and the vertical axis is the degree of polarization, the relationship is as shown in Figure 4, and the glass plate 17 is 8
A degree of polarization of about 80% can be achieved by using 10 to 10 sheets. FIG. 5 shows another embodiment of the polarizing beam splitter 2. In the figure, 20 is a small glass plate similar to the glass plate 17 in FIG. The same effect can be obtained while occupying approximately 1/2 the space, so it is effective for downsizing the device. As mentioned above, a degree of polarization of about 80% can be achieved by placing 8 to 10 parallel glass plates 17 so that the incident angle of the superimposed light is Brewster's angle. The absorption of the S-polarized light component by the side polarizing plate 13 is 30
%, and the increase in itching of the polarizing plate 13 can be minimized. Therefore, this polarizing plate 13 is
Even if the liquid crystal light valves 7R, 7G, 7B are placed immediately before the polarizing plate 13, the influence of the temperature of the polarizing plate 13 on the liquid crystal light valves 7R, 7G, 7B is extremely small, even if environmental temperature conditions are taken into account. A dedicated cooling fan is not required.

FIG. 1 also shows an embodiment in which a cooling fan 15 is provided so that the air flow path for cooling the liquid crystal light valves 7R, 7G, and 7B and the air flow path for cooling the light source 1 are common. No. 16 is missing the air intake holes provided in the housing directly below the liquid crystal light valves 7R, 7G, and 7B. FIG. 6 is a schematic vertical cross-sectional view of the intake air, showing how the air sucked from the intake hole 16 passes through the polarizing plate 13, 14 and the surface of the liquid crystal light valve 7 and is sucked into the cooling fan 15. The air sucked in through the only intake hole 16 cools the polarizing plate 13, 14 and the liquid crystal light valves 7R, 7G, 7B as shown in FIGS. Therefore, sufficient cooling is possible with a single cooling fan 15.

[Effects of the Invention] As explained above, in the liquid crystal display device of the present invention, a polarizing beam splitter such as a glass plate is provided between the light source and the light separation means, and a common air flow between the liquid crystal light valve and the light source is provided. By providing a separate cooling fan in the path and providing cooling intake holes in the housing below or above the liquid crystal light valve, it is possible to minimize the temperature rise of the polarizing plate and liquid crystal light valve, making it possible to Since it is possible to use a low-speed cooling fan even under environmental temperature conditions,
It is possible to realize a low-cost liquid crystal display device that is highly reliable, has low noise, is compatible with today's AV trends, and facilitates layout and housing two-circuit design.

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[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an optical system of a liquid crystal display device of the present invention, FIG. 2 is a schematic diagram of a polarizing beam splitter of the present invention, and FIG. 3 is a principle diagram of a polarizing beam splitter of the present invention. FIG. 4 is a diagram showing the relationship between the number of glass plates and the degree of polarization in the polarizing beam splitter of the present invention, FIG. 5 is a schematic diagram of another polarizing beam splitter of the present invention, and FIG. A schematic vertical cross-sectional diagram showing the flow of wind in a liquid crystal display device.
FIG. 7 is a schematic plan view showing wind flow in the liquid crystal display device of the present invention, and FIG. 8 is a configuration diagram of the optical system of a conventional liquid crystal display device. 1 ・ 2 ・ 3 ・ 7 ・ 8 ・ 1 5 Light source Polarizing beam splitter Light separating means Liquid crystal light valve Light combining means Projection lens Cooling fan 2- 6 7 8 9 0 ・Intake hole・Glass plate・P polarized light component・S polarized light component・Glass plate or higher

Claims (3)

[Claims] (1) A light source, a light separation means for separating light from the light source, a liquid crystal light valve for modulating the light from the light separation means, and a light synthesis means for combining the modulated light from the liquid crystal light valve. , a liquid crystal display device having a projection lens for projecting light from the light combining means, and a cooling fan for cooling the liquid crystal light valve and the light source, wherein a polarizing beam splitter is provided between the light source and the light separating means. A liquid crystal display device characterized by: (2) The liquid crystal display device according to claim 1, wherein the polarizing beam splitter is a plurality of glass plates stacked in parallel so that the incident angle of light with respect to the glass plates is Brewster's angle. (3) The cooling fan is used solely for a common air flow path between the liquid crystal light valve and the light source, and the air intake hole is provided in the housing below or above the liquid crystal light valve. The liquid crystal display device according to claim 1.