JPH05210097A - Projection type liquid crystal display device - Google Patents

Abstract

PURPOSE:To improve the contrast of a projection image formed on a screen surface by absorbing light, which is reflected by the incidence-side lens surface of a projection lens system, without reflecting it by the glass substrate of a liquid crystal display panel. CONSTITUTION:A 1/4-wavelength plate 10 which rotates and polarizes transmitted light by nearly 45 deg. is provided between the liquid crystal display panel 1 and projection lens system 6; and reflected light which is reflected by the surface of the incidence-side lens (condenser Fresnel lens 8) of the projection lens system 6 and made incident on the liquid crystal display panel 1 is polarized into polarized light which crosses the transmission axis of the projection-side polarizing plate 2b of the liquid crystal display panel 1 almost at right angles, and the light is made incident on the liquid crystal panel 1.

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.

[0002]

2. Description of the Related Art Recently, a projection type liquid crystal display device has been considered as a liquid crystal display device for displaying a television image or the like using a liquid crystal display panel.

FIG. 5 shows a conventional projection type liquid crystal display device. In FIG. 5, reference numeral 1 denotes a liquid crystal display panel. As the liquid crystal display panel 1, generally, liquid crystal molecules are arranged in a twist arrangement and at the light incident surface side. Polarizing plate 2 on the output surface side
A TN (Twisted Nematic) type in which a and 2b are arranged is used.

A light source 3 is disposed on the liquid crystal display panel 1 so as to face the light incident surface. The light source 3 is a high-intensity light source lamp 4 such as a halogen lamp or a xenon lamp.
And the radiated light from the light source lamp 4 is applied to the liquid crystal display panel 1.
And a reflector 5 that reflects the light toward the.

Reference numeral 6 denotes a projection lens system for enlarging and projecting the display image of the liquid crystal display panel 1 on the screen 9. The projection lens system 6 projects the projection lens 7 and the image light transmitted through the liquid crystal display panel 1. It comprises a condenser Fresnel lens (circular Fresnel lens) 8 for condensing on the projection lens 7.

In this projection type liquid crystal display device, light emitted from a light source 3 is incident on a liquid crystal display panel 1, and image light passing through the liquid crystal display panel 1 is enlarged by a projection lens system 6 and projected on a screen 9 surface. According to this projection type liquid crystal display device, however, the display image on the liquid crystal display panel 1 having a small display screen can be greatly enlarged and viewed.

[0007]

However, in the above-mentioned conventional projection type liquid crystal display device, a part of the image light which passes through the liquid crystal display panel 1 and enters the projection lens system 6 has an incident side lens of the projection lens system 6. Surface, that is, the converging Fresnel lens 8 surface, is reflected toward the liquid crystal display panel 1 side, and the reflected light is reflected by the glass substrate of the liquid crystal display panel 1 and projected onto the screen 9 surface by the projection lens system 6, so that this reflection is performed. There is a problem that the contrast of the projected image formed on the screen 9 is deteriorated due to the influence of light.

That is, FIG. 6 shows a light trace between the liquid crystal display panel 1 and the surface of the condenser Fresnel lens 8 in the conventional projection type liquid crystal display device shown in FIG. Light traces when light transmitted through the display panel 1 is incident on the condenser Fresnel lens 8 in parallel with the lens optical axis O, (b) shows that light transmitted through the liquid crystal display panel 1 is oblique to the lens optical axis O. The trace of light when entering the condenser Fresnel lens 8 is shown.

Explaining this light trace, in the TN type liquid crystal display panel 1, the irradiation light from the light source is made incident as linearly polarized light by the incident side polarization plate 2a, and out of the light passing through the liquid crystal layer, the emission side polarization plate 2b. The polarized light (light in the vibrating direction along the transmission axis of the exit-side polarization plate 2b) that passes through is emitted as image light. The image light transmitted through the liquid crystal display panel 1 is condensed as shown by the solid line in the figure. It enters the Fresnel lens 8.

Most of the light incident on the condenser Fresnel lens 8 passes through the condenser Fresnel lens 8 and is incident on the projection lens, but a part of the light is condensed by the condenser Fresnel lens 8 as shown by a broken line in the figure. The eight surfaces are reflected at a reflection angle corresponding to the angle of this lens surface.

Since this reflected light is the light that has passed through the exit side polarization plate 2b of the liquid crystal display panel 1, its vibration direction is along the transmission axis of the exit side polarization plate 2b, and therefore this lens surface The reflected light from is transmitted through the emission side polarizing plate 2b and is incident on the liquid crystal display panel 1.

The reflected light that enters the liquid crystal display panel 1 enters the liquid crystal display panel 1 at an angle, so that the light is reflected by the glass substrate of the liquid crystal display panel 1 and the exit side polarization plate 2b. Through the condenser Fresnel lens 8 and is projected onto the screen surface by the projection lens.

Therefore, in the above-mentioned conventional projection type liquid crystal display device, in addition to the regular image light projected on the screen 9 surface by the projection lens system 6 without being reflected by the light collecting Fresnel lens 8 surface, the light collecting light is condensed. The light reflected by the Fresnel lens 8 surface and further reflected by the glass substrate of the liquid crystal display panel 1 is also projected on the screen 9 surface, so that the contrast of the projected image formed on the screen 9 surface is deteriorated. ..

There is also a type of the projection type liquid crystal display device in which the projection lens system 6 is only the projection lens 7 and the image light transmitted through the liquid crystal display panel 1 is directly incident on the projection lens 7. Also in the case of the projection type liquid crystal display device of the type, a part of the image light incident on the projection lens 7 is reflected by the incident side lens surface of the projection lens 7, and the reflected light is reflected by the glass substrate of the liquid crystal display panel 1. Projection lens 7
As a result, the projection image formed on the screen 9 surface is enlarged and projected, so that the contrast of the projected image formed on the screen 9 surface is deteriorated.

The present invention has been made in view of the above situation, and an object thereof is to reflect the light reflected by the incident side lens surface of the projection lens system on the glass substrate of the liquid crystal display panel. It is an object of the present invention to provide a projection-type liquid crystal display device that can be absorbed without being absorbed to improve the contrast of a projection image formed on the screen surface.

[0016]

In order to achieve the above object, the present invention transmits transmitted light at an angle of about 45 ° between a liquid crystal display panel having a polarizing plate on at least an emitting side and a projection lens system.
It is provided with a rotatory body that rotates the light.

[0017]

That is, in the projection type liquid crystal display device of the present invention, the linearly polarized image light transmitted through the exit side polarization plate of the liquid crystal display panel is rotated by about 45 ° by the optical rotator and then is incident on the projection lens system. At the same time, the light reflected on the liquid crystal display panel side by the incident side lens surface of the projection lens system is further rotated by about 45 ° by the above-mentioned optical rotator. The reflected light that is reflected by the incident side lens surface of the lens system and enters the liquid crystal display panel becomes polarized light that is substantially orthogonal to the transmission axis of the exit side polarizing plate of the liquid crystal display panel due to the two rotations by the optical rotator. Incident on the liquid crystal display panel, the reflected light is absorbed by the exit side polarization plate of the liquid crystal display panel, and this reflected light is reflected on the glass substrate of the liquid crystal display panel and enters the projection lens system. Can be prevented.

Therefore, according to this projection type liquid crystal display device, the light projected on the screen surface is not reflected by the incident side lens surface of the projection lens system, but is projected onto the screen surface by the projection lens system. Since only the image light is used, the contrast of the projected image formed on the screen surface can be improved.

[0019]

EXAMPLES Examples of the present invention will be described below.

1 and 2 show a first embodiment of the present invention, in which 1 is a TN type liquid crystal display panel having polarizing plates 2a and 2b on a light incident surface and a light emitting surface, respectively. Reference numeral 3 is a light source including a light source lamp 4 and a reflector 5, 6 is a projection lens system including a projection lens 7 and a condenser Fresnel lens 8, and 9 is a screen, which are the conventional projection type liquid crystal displays shown in FIG. It is the same as the device.

Reference numeral 10 denotes a quarter wave plate which is arranged between the liquid crystal display panel 1 and the projection lens system 6 so as to face the light emitting surface of the liquid crystal display panel 1. This quarter wave plate 1
0 is to rotate the transmitted light by about 45 °.
The four-wave plate 10 is arranged with its optical axis aligned with the direction of approximately 45 ° with respect to the transmission axis of the exit-side polarization plate 2b of the liquid crystal display panel 1. The quarter wave plate 10 is supposed to have its surface subjected to a surface treatment for eliminating light reflection.

In this projection type liquid crystal display device, linearly polarized image light that has passed through the exit side polarization plate 2b of the TN type liquid crystal display panel 1 is rotated by a quarter wavelength plate 10 at an angle of about 45 ° and then a projection lens system. The light reflected on the liquid crystal display panel 1 side by the incident side lens surface of the projection lens system 6, that is, the converging Fresnel lens 8 surface is further rotated by 45 ° by the ¼ wavelength plate 10 while being incident on the liquid crystal display panel 6. If the quarter wave plate 10 is provided, it is reflected by the surface of the condenser Fresnel lens 8 of the projection lens system 6 and enters the liquid crystal display panel 1 as shown by the broken line in FIG. The vibrating direction of the reflected light is a direction rotated by 90 ° with respect to the vibrating direction when the liquid crystal display panel 1 is emitted by the 2 ° optical rotation by the quarter-wave plate 10.

For this reason, the reflected light reflected by the surface of the condenser Fresnel lens 8 becomes polarized light which is substantially orthogonal to the transmission axis of the exit side polarizing plate 2b of the liquid crystal display panel 1 and enters the liquid crystal display panel 1. This reflected light is absorbed by the exit side polarization plate 2b of the liquid crystal display panel 1, so that the reflected light is prevented from being reflected by the glass substrate of the liquid crystal display panel 1 and entering the projection lens system 6. be able to.

Therefore, according to this projection type liquid crystal display device, the light projected on the surface of the screen 9 is shown by the solid line in FIG. 2 without being reflected by the surface of the condenser Fresnel lens 8. Since only the normal image light is transmitted as described above, it is possible to improve the contrast of the projection image formed on the screen 7 surface.

Although FIG. 2 shows light traces when the light transmitted through the liquid crystal display panel 1 is incident on the condenser Fresnel lens 8 in parallel with the lens optical axis O, the light transmitted through the liquid crystal display panel 1 is shown. Even when is incident on the condenser Fresnel lens 8 obliquely with respect to the lens optical axis O, the reflected light reflected by the surface of the condenser Fresnel lens 8 is absorbed by the emission side polarizing plate 2b of the liquid crystal display panel 1 in the same manner as described above. To be done.

In the above embodiment, the projection type liquid crystal display device using one liquid crystal display panel 10 has been described, but the present invention is a projection type liquid crystal display device provided with a plurality of liquid crystal display panels, for example, Projection for enlarging and projecting a full-color image that combines the red, green, and blue images displayed by each of the liquid crystal display panels by using three liquid crystal display panels that display red, green, and blue images, respectively. Type liquid crystal display device.

That is, FIG. 3 shows a second embodiment of the present invention, in which 1R, 1G and 1B are three TN type liquid crystal display panels, 1R is for red image display and 1G is for For green image display, 1B is for blue image display.

Each of these liquid crystal display panels 1R, 1G, 1B
Displays the same image of different colors. In each of the liquid crystal display panels 1R, 1G, 1B, three light incidences are made by the image combining dichroic prism 11 provided with the light exit surface facing the projection lens system 6. They are arranged so as to face each other. In this embodiment, each liquid crystal display panel 1
R, 1G, 1B from the light source not shown respectively red, green,
By making the blue colored lights R, G, B incident, red, green, and blue images are displayed on the respective liquid crystal display panels 1R, 1G, 1B.

In this projection type liquid crystal display device, the red, green and blue image lights transmitted through the respective liquid crystal display panels 1R, 1G and 1B are combined into one full color image by a dichroic prism 11, and this full color image is projected by a projection lens. The system 6 magnifies and projects on the screen surface, and the quarter-wave plate 10 is arranged between each liquid crystal display panel 1R, 1G, 1B and the dichroic prism 11.

Even in this projection type liquid crystal display device, however, part of the full-color image light that is combined by the dichroic prism 11 and is incident on the projection lens system 6 is the incident side lens surface of the projection lens system 6, that is, the converging Fresnel lens. The reflected light is reflected by the eight surfaces and returns to the liquid crystal display panels 1R, 1G, 1B side through the dichroic prism 11, but as described above,
If the quarter wave plate 10 is provided on each of the light emitting surfaces of G and 1B, the reflected light reflected by the surface of the condenser Fresnel lens 8 and incident on the liquid crystal display panel 1 is the quarter wave plate. By the optical rotation of 2 by 10, the polarized light becomes substantially orthogonal to the transmission axis of the exit side polarizing plate 2b of the liquid crystal display panel 1 and enters the liquid crystal display panel 1, so this reflected light is emitted from the exit side of the liquid crystal display panel 1. It is possible to improve the contrast of the projection image which is absorbed by the polarizing plate 2b and is focused on the screen surface.

In the second embodiment, each of the liquid crystal display panels 1R, 1G and 1B has a quarter of the light emission surface side.
Although the wave plate 10 is provided, the quarter wave plate 10 is
As in the third embodiment shown in FIG. 4, only one sheet may be arranged on the light emitting surface side of the image combining dichroic prism 11.

In this case, each liquid crystal display panel 1R, 1
The transmission axes of the G and 1B emission side polarization plates 2b are all in the same direction, and the optical axis of the quarter wavelength plate 10 is the emission side polarization plate 2b.
It is enough to match the direction of about 45 ° to the transmission axis of
By doing so, the reflected light reflected by the surface of the condenser Fresnel lens 8 passes through the quarter-wave plate 10 and the liquid crystal display panel 1
The polarized light is substantially orthogonal to the transmission axis of the exit side polarization plate 2b and enters the liquid crystal display panels 1R, 1G, 1B through the dichroic prism 11, so that the reflected light is reflected by the liquid crystal display panel 1. It can be absorbed by the emission side polarizing plate 2b.

In each of the above embodiments, the projection lens system 6
Although the projection type liquid crystal display device including the projection lens 7 and the converging Fresnel lens 8 is shown, the present invention uses the projection lens system 6 only as the projection lens 7 and directly transmits the image light transmitted through the liquid crystal display panel 1. Needless to say, the present invention can be applied to a projection type liquid crystal display device in which the light is incident on the projection lens 7.

In the above embodiment, the quarter wave plate 10 is used as the optical rotator provided between the liquid crystal display panel and the projection lens system. As the optical rotator, liquid crystal molecules are approximately 45 °. A twisted liquid crystal panel may be used.

[0035]

According to the projection type liquid crystal display device of the present invention, an optical rotator for rotating transmitted light by about 45 ° is provided between at least the liquid crystal display panel having a polarizing plate on the exit side and the projection lens system. , Reflected light that is reflected by the incident side lens surface of the projection lens system and enters the liquid crystal display panel is made into polarized light that is substantially orthogonal to the transmission axis of the exit side polarization plate of the liquid crystal display panel, and then enters the liquid crystal display panel. Since this is done, the light reflected by the incident side lens surface of the projection lens system is absorbed without being reflected by the glass substrate of the liquid crystal display panel, improving the contrast of the projected image formed on the screen surface. Can be made

[Brief description of drawings]

FIG. 1 is a side view of a projection type liquid crystal display device showing a first embodiment of the present invention.

FIG. 2 is a light trace diagram similarly between the liquid crystal display panel and the lens surface.

FIG. 3 is a side view of a projection type liquid crystal display device showing a second embodiment of the present invention.

FIG. 4 is a side view of a projection type liquid crystal display device showing a third embodiment of the present invention.

FIG. 5 is a side view of a conventional projection type liquid crystal display device.

FIG. 6 is a light trace diagram between a liquid crystal display panel and a lens surface in a conventional projection type liquid crystal display device.

[Explanation of symbols]

 1, 1R, 1G, 1B ... TN type liquid crystal display panel 2a, 2b ... Polarizing plate 3 ... Light source 6 ... Projection lens system 7 ... Projection lens 8 ... Condensing Fresnel lens 9 ... Screen 10 ... Quarter wave plate (optical rotator) ) 11 ... Dichroic prism

Claims (1)

[Claims] 1. A projection type liquid crystal display device for enlarging a display image of a liquid crystal display panel by a projection lens system and projecting it on a screen surface, at least between a liquid crystal display panel having a polarizing plate on the exit side and the projection lens system. And the transmitted light is almost 45
A projection type liquid crystal display device, which is provided with an optical rotator for rotating light.