JPH0651268A - Projection liquid crystal display - Google Patents

Abstract

PURPOSE:To make effective use of light from a light source and to reduce the rate of heating of a polarizer. CONSTITUTION:In a projection liquid crystal display which uses as a light valve a liquid crystal panel 5 equipped with a polarizer, an optical element 4 such as a quarter wavelength plate for converting circularly and elliptically polarized light into rectilinearly polarized one is disposed between a light source 1 for illuminating the liquid crystal panel 5 and the light-source side polarizer 10 provided to the liquid crystal panel, so that the direction of rectilinear polarization achieved by the optical element 4 coincides with that of polarization by the light-source side polarizer 10.

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 in which a liquid crystal panel is used as a light valve, an optical image formed on the liquid crystal panel is irradiated with light from a light source, and is projected on a screen by a lens.

[0002]

2. Description of the Related Art In order to display an image on a large screen, an optical image is formed on a small light valve as a change in optical characteristics according to an image signal, and the optical image is irradiated with light from a light source.
2. Description of the Related Art There is known a projection type liquid crystal display device that enlarges and projects on a screen by a projection lens. Conventionally, a CRT has been used as a light valve, but recently, a liquid crystal panel in which picture elements are arranged in a matrix tends to be used. A configuration diagram of a general projection type liquid crystal display device is shown in FIG. In FIG. 3, a part of the light source light emitted from the light source 31 is directly reflected, and the rest is reflected by the reflecting mirror 32, passes through the lens 33, and is applied to the light valve including the liquid crystal panel 34. Illuminate the optical image of the light valve with the light source,
The optical image is magnified by the projection lens 36 and formed on the surface of a transmissive or reflective screen 37. Next, FIG. 4 shows a configuration diagram of a general liquid crystal panel. LCD panel 34
In the above, a nematic liquid crystal 41 is sandwiched between two plate glasses coated with a transparent conductive film in a thickness of about 10 μm. In addition, a polarizing plate in which a support such as an acetate cellulose-based film is attached by an adhesive to both surfaces of a polarizer manufactured by adsorbing a polarizing element such as iodine on a polarizing substrate such as a stretched polyvinyl alcohol film. One 42 is provided on each of the incident light side and the outgoing light side. Light is transmitted (illustrated) when a voltage is not applied to the transparent electrodes of the liquid crystal panel, and light is blocked when a voltage is applied. Also, two-dimensional images and characters are displayed by patterning the two transparent conductive films so that they are orthogonal to each other, or by providing active elements such as transistors and switch elements at the intersections of the picture elements.

[0003]

In the projection type liquid crystal display device using the above liquid crystal panel, since the light source is natural light having no polarization property, the polarizer on the light source side of the liquid crystal panel has a direction other than the polarization direction. Since the light is absorbed, there are problems that the light from the light source cannot be effectively used and that the polarizer generates heat and needs to be cooled.

An object of the present invention is to provide a projection type liquid crystal display device in which light from a light source is effectively used and heat generation of a polarizer is reduced.

[0005]

In order to solve the above problems, according to the present invention, a light source for illuminating a liquid crystal panel of a projection type liquid crystal display device and a light source side polarizer provided on the liquid crystal panel are provided. An optical element for converting circularly polarized light and elliptically polarized light into linearly polarized light, so that the polarization direction of the linearly polarized light converted by the optical element matches the polarization direction of the light source side polarizer,
It is arranged. As such an optical element, it is preferable to use a quarter-wave plate made of a birefringent plate such as a quartz plate.

[0006]

In the projection type liquid crystal display device of the present invention, since the polarization direction of the linearly polarized light converted by the above optical element matches the polarization direction of the light source side polarizer, the light source side polarization Light absorption by the child is reduced, the light utilization efficiency of the light source is improved, and heat generation of the polarizer is reduced.

[0007]

Embodiments of the projection type liquid crystal display device of the present invention will be specifically described below. A schematic configuration diagram of a projection type liquid crystal display device according to the present invention is shown in FIG. In this projection type liquid crystal display device, circularly polarized light and elliptically polarized light are converted into linearly polarized light between the light source 1 and the light source side polarizer 10 of the two polarizers 10 and 11 provided in the liquid crystal panel 5. An optical element 4 for converting is provided. A part of the light source light emitted from the light source 1 is directly reflected, and the remaining part is reflected by the reflecting mirror 2, transmitted through the lens 3, converted into parallel rays, and applied to the liquid crystal panel 5. The optical image of the liquid crystal panel is irradiated with light from the light source, and the optical image is enlarged by the projection lens 6 and formed on the surface of the transmissive or reflective screen 7. That is, the circularly polarized light and the elliptically polarized light 8 of the natural light from the light source 1 and the natural light reflected by the reflecting mirror 2 which are converted into parallel rays by the lens 3
Is converted into linearly polarized light 9 by the optical element 4 described above. Here, the above optical element is arranged so that the polarization direction of the linearly polarized light 9 matches the polarization direction of the polarizer 10 on the light source side.

An example in which a quarter wave plate is used as the above optical element will be described with reference to FIG. When the circularly polarized light 22 is incident on the quarter-wave plate 21 shown in FIG. 2, the ordinary ray and the extraordinary ray have a phase difference corresponding to a quarter-wavelength after they are transmitted. On the other hand, linearly polarized light 23 having an azimuth angle of 45 ° is emitted from the quarter-wave plate. A birefringent plate made of quartz, calcite, or the like can be used as such a quarter-wave plate.

[0009]

As described above, the projection type liquid crystal display device of the present invention is an optical device for converting circularly polarized light and elliptically polarized light into linearly polarized light between the light source and the light source side polarizer provided in the liquid crystal panel. Since the element is provided, light absorption by the light source side polarizer is reduced. Therefore, in the projection type liquid crystal display device of the present invention, the light utilization efficiency of the light source is improved and the heat generation of the polarizer is reduced.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a projection type liquid crystal display device of the present invention.

FIG. 2 is a perspective view showing an embodiment of an optical element (1/4 wavelength plate) used in the present invention.

FIG. 3 is a schematic configuration diagram of a general projection type liquid crystal display device.

FIG. 4 is a schematic configuration diagram of a liquid crystal panel.

[Explanation of symbols]

1, 31 ... Light source, 2, 32 ... Reflecting mirror, 3, 33 ... Lens, 4 ... Optical element, 5, 34 ... Liquid crystal panel, 6, 36 ...
Projection lens, 7, 37 ... Screen, 10, 12 ... Polarizer

Claims (2)

[Claims] 1. A projection type liquid crystal display device using a liquid crystal panel having a polarizer as a light valve, wherein a light source for illuminating the liquid crystal panel and a light source side polarizer provided in the liquid crystal panel. And an optical element for converting circularly polarized light and elliptically polarized light into linearly polarized light is arranged so that the polarization direction of the linearly polarized light converted by the optical element matches the polarization direction of the light source side polarizer. Characteristic projection type liquid crystal display device. 2. The projection type liquid crystal display device according to claim 1, wherein the optical element for converting circularly polarized light and elliptically polarized light into linearly polarized light is a quarter-wave plate.