JP2953077B2 - 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 for projecting and displaying an image by using a liquid crystal light valve for image formation.

[0002]

2. Description of the Related Art In order to prevent the temperature of a liquid crystal light valve of a conventional projection type liquid crystal display device from rising due to light irradiation and preventing image quality from deteriorating, a method of cooling air by sending air using a fan is generally used. The air inlet was provided with a filter.

[0003]

However, in the above-mentioned prior art, dust or dirt that has passed through a filter or entered from other places is inside the projection type liquid crystal display device, and the liquid crystal light valve is mainly used for the fan of the fan. Dust and dust are attached by the static electricity due to the wind, and form an image on the screen because it is close to the image forming surface of the projection lens.

Accordingly, the present invention is to solve such a problem, and an object of the present invention is to provide a projection type liquid crystal display device for displaying a high quality image on a screen.

[0005]

A projection display apparatus according to the present invention comprises a light source, a light valve for modulating light emitted from the light source, and a projection lens for projecting light modulated by the light valve. In the projection display device provided with the light-emitting device, a layer having conductivity is provided on a light entrance / exit surface of the light valve, and the layer having conductivity is grounded. Further, in a projection display device including a light source, a light valve that modulates light emitted from the light source, and a projection lens that projects light modulated by the light valve, the light valve includes a polarizing element. A conductive layer is provided on the surface of the polarizing element, and the conductive layer is grounded.

[0006]

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing an example of a light valve used in the projection display device of the present invention. A liquid crystal 5 is sandwiched between the two glasses 4 on which the electrode 2 and the conductor layer 3 are formed via the electrode 2. The electrode 2 is connected to a drive circuit, and a drive voltage is applied in accordance with an input signal to modulate the liquid crystal 5 to form an image. As the liquid crystal 5, PDLC (Polymer-Dispersed Liquid Crystal) which performs display by scattering and transmitting light was used. As a method of the liquid crystal light valve 1, any method such as an active matrix and time division driving may be used.

The conductor layer 3 is made of ITO (Indium Thin Oxid).
e) It was formed by vacuum evaporation or sputtering. ITO is a typical substance of a conductor having a high transmittance, and other substances may be used as long as the conductor has a high transmittance. By grounding, the potential is always kept at zero, no static electricity is generated by the flow of air, and no dust or dust is absorbed. Further, in the case of the active matrix liquid crystal light valve 1, destruction of elements due to static electricity can be eliminated.

The thickness and the refractive index of the conductor layer 3 are set
By optimizing for the refractive index, the decrease in transmittance can be minimized. Conventionally, there is about 4% reflection at the boundary surface between the glass 4 and the air, which is one of the causes for reducing the brightness of the projection type liquid crystal display device. However, the conductor layer 3 also serves as the anti-reflection coating. If possible, it will also contribute to the increase in brightness.

FIG. 2 is a block diagram showing an example of the projection display device of the present invention. Light emitted from the light source 6 enters the color separation optical system 7 and is separated into three primary colors of red, green, and blue. The color separation optical system 7 includes two dichroic mirrors 10 and 11. The dichroic mirror 10 is obtained by vacuum-depositing a dielectric multilayer film, and the order of color separation and wavelength characteristics can be arbitrarily determined. Each color light enters the liquid crystal light valve 1 and is modulated according to each input signal. After that, the light enters the color combining optical system 8 and is combined,
The image is enlarged and projected by the projection lens 9 as a full-color image. The color combining optical system 8 also includes two dichroic mirrors 10.
And the mirror 1 to match the wavelength separation characteristics of the color separation optical system 7.

Although not shown, each of the liquid crystal light valves 1 is forcibly cooled by a fan to prevent deterioration in image quality due to a rise in temperature. It is clear that the present invention is effective not only for static electricity generated by a fan but also for static electricity generated by other factors.

Embodiment 2 FIG. 3 is a sectional view showing another example of a light valve used in the projection display device of the present invention.

The liquid crystal light valve 1 of this embodiment is composed of an electrode 2, a conductor layer 3, glass 4, and a liquid crystal 5, and is the same as the above-described embodiment. The difference is that a liquid crystal 5 of a mode using polarized light is used for display. Therefore, the polarizing element 12 is provided at the light entrance / exit portion. Here, a typical mode using polarization is TN (Twisted-Nemat).
ic) Although liquid crystal is used, any mode that requires the polarizing element 12 for display is effective. The polarizing element 12 is bonded by sandwiching a polarizing film 13 with a hard and transparent holding member 14 such as glass or plastic. The conductor layers 3 are formed on both surfaces in the same manner as in the first embodiment, and are grounded.

Generally, in a projection type liquid crystal display device, since the polarizing element 12 is installed near the liquid crystal light valve 1, dirt and dust adhering to the polarizing element 12 due to static electricity are displayed on the screen. However, according to the above-mentioned configuration, such a thing does not occur. Further, since the polarizing film 13 absorbs light and raises the temperature, there is a possibility of causing thermal destruction. However, the structure in which the polarizing film 13 is sandwiched by the holding members 14 allows heat to easily escape and leads to improvement in reliability. Also, in the conventional polarizing plate, while there is light attenuation due to the above-mentioned reflection,
By optimizing, the reflection becomes low and the transmittance can be increased.

By setting such a liquid crystal light valve 1 and the polarizing element 12 and assembling them into the projection type liquid crystal display device of FIG. 2, a high quality image can be displayed. Polarizing element 1
The same effect can be obtained even if 2 is directly adhered to the liquid crystal light valve 1.

Although the transmission type liquid crystal light valve 1 has been described above, it should be added that the reflection type liquid crystal light valve 1 produces exactly the same effect.

[0017]

As described above, according to the present invention, by providing a conductive layer on the surface of the light valve or the surface of the polarizing element and grounding the surface, the generation of static electricity due to the flow of air is prevented, and A high-quality image can be displayed without preventing the adhesion of dust and dust, and without displaying the shadow on the screen.

In addition to preventing the destruction of the element due to static electricity, the thickness and refractive index of the conductive layer are optimized to prevent attenuation due to light reflection, thereby increasing the brightness of an image.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of a light valve used in a projection display device of the present invention.

FIG. 2 is a configuration diagram illustrating an example of a projection display device of the present invention.

FIG. 3 is a sectional view showing another embodiment of the light valve used in the projection display device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Liquid crystal light valve 2 Electrode 3 Conductive layer 4 Glass 5 Liquid crystal 6 Light source 7 Color separation optical system 8 Color synthesis optical system 9 Projection lens 10 Dichroic mirror 11 Mirror 12 Polarizing element 13 Polarizing film 14 Holding member

Claims (3)

(57) [Claims] 1. A projection display device comprising: a light source; a light valve that modulates light emitted from the light source; and a projection lens that projects light modulated by the light valve. Is provided with a conductive layer, and the conductive layer is grounded. 2. A projection type display device comprising: a light source; a light valve for modulating light emitted from the light source; and a projection lens for projecting light modulated by the light valve. A projection display device comprising: an element; and a conductive layer is provided on a surface of the polarizing element, and the conductive layer is grounded. 3. The projection type display device according to claim 1, wherein the light valve is cooled by a fan.