JPH05210098A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To obtain a high-brightness, high-contrast image by displaying an image with high brightness on a liquid crystal display panel by utilizing light from a light source without any waste. CONSTITUTION:A polarization beam splitter 8 which transmits the P-polarized component of the light from the light source 3 and reflects the S-polarized component toward the light source 3 is arranged between the light source 3 and liquid crystal panel 1, and a 1/4-wavelength plate which rotates and polarizes the transmitted beam by almost 45 deg. is provided between the polarization beam splitter 8 and light source 3; and the S-polarized component which is reflected by the polarization beam splitter 8 toward the light source 3 is made incident as P-polarized light on the liquid crystal display panel 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device.

[0002]

2. Description of the Related Art Recently, for example, 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 twist-arranged and emitted from the light incident side. Polarizers 2a on the side and
A TN (Twisted Nematic) type in which 2b is arranged is used.

A light source 3 is arranged 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.
The reflector 5 is a parabolic reflector that reflects the emitted light from the light source lamp 4 as parallel light parallel to the reflector optical axis. Further, 6 is a projection lens arranged to face the light emitting surface of the liquid crystal display panel 1, and 7 is a screen.

In this projection type liquid crystal display device, irradiation light 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 6 and projected on a screen 7 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.

[0006]

However, in the above-mentioned conventional liquid crystal display device, since the light emitted from the light source 3 is directly incident on the liquid crystal display panel 1, almost half of the light emitted from the light source 3 is emitted. Only the light of the above can be used for display on the liquid crystal display panel 1. Therefore, the brightness of the display image on the liquid crystal display panel 1 is low and the screen 7
There is a problem that the projected image enlarged and projected on the surface becomes a dark image with poor contrast.

This is because the light emitted from the light source 3 is random light in various vibration directions, whereas the liquid crystal display panel 1
However, since the display is performed by using only the linearly polarized light transmitted through the incident side polarizing plate 2a, the vibration of the irradiation light from the light source 3 along the transmission axis direction of the incident side polarizing plate 2a. The light in the direction is transmitted through the incident side polarizing plate 2a and is incident on the liquid crystal display panel 1, but the light in the vibration direction orthogonal to the transmission axis direction of the incident side polarizing plate 2a is absorbed in the incident side polarizing plate 2a. Therefore, the amount of light that actually enters the liquid crystal display panel 1 becomes almost half of the amount of light emitted from the light source 3.

The present invention has been made in view of the above situation, and an object of the present invention is to utilize most of the irradiation light from a light source for display on a liquid crystal display panel without waste and to display a liquid crystal display. An object of the present invention is to provide a liquid crystal display device capable of displaying an image with high brightness on a panel and forming an image with high brightness and high contrast.

[0009]

In order to achieve the above object, the present invention provides a light source comprising a liquid crystal display panel, a light source lamp and a reflector for reflecting light emitted from the light source lamp toward the liquid crystal display panel. In a liquid crystal display device including, between the light source and the liquid crystal display panel,
A polarization beam splitter that transmits the P-polarized component light of the irradiation light from the light source and reflects the S-polarized component light to the light source side is disposed, and is transmitted between the polarization beam splitter and the light source. It is provided with an optical rotator that rotates light by approximately 45 °.

[0010]

That is, in the liquid crystal display device of the present invention, the irradiation light from the light source is incident on the polarization beam splitter through the optical rotator, so that the P polarization component of the irradiation light from the light source which is transmitted through the polarization beam splitter is transmitted. The light is directly incident on the liquid crystal display panel, and the remaining light, that is, the S-polarized component light reflected to the light source side by the polarization beam splitter, is rotated by about 45 ° by the optical rotator to once become circularly polarized light. Is reflected by the reflector of the light source and passed through the optical rotator again to be further rotated by about 45 ° to be P-polarized light, and then the P-polarized light is incident on the polarization beam splitter.

As described above, when the light of the S-polarized component reflected on the light source side by the polarization beam splitter is made incident on the polarization beam splitter again as P-polarized light, this light also passes through the polarization beam splitter and is displayed on the liquid crystal display. It can be incident on the panel.

Since the light that passes through the polarization beam splitter and enters the liquid crystal display panel is the light of the P polarization component, the TN type liquid crystal display panel is displayed by using the linearly polarized light of the P polarization component as the incident light. Then, all the light transmitted through the polarization beam splitter can be used for display on the liquid crystal display panel.

Therefore, according to the liquid crystal display device of the present invention, most of the irradiation light from the light source is used for display on the liquid crystal display panel without waste, and an image with high brightness is displayed on the liquid crystal display panel and is displayed on the screen surface. The projected image that is magnified and projected can be a bright image with high contrast.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS.

In FIGS. 1 and 2, reference numeral 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, and 3 is a light source lamp 4 and a parabolic reflector 5.
A light source consisting of, a projection lens 6 and a screen 7 are the same as those of the conventional projection type liquid crystal display device shown in FIG.

Reference numeral 8 is a polarization beam splitter arranged between the light source 3 and the liquid crystal display panel 1. The polarization beam splitter 8 transmits the S-polarized component light of the irradiation light from the light source 3 in the random vibration direction and reflects the P-polarized component light to the light source side 3. , Three prisms 8a, 8b, 8 as shown
It is configured by combining c.

Numeral 9 is a quarter-wave plate which is provided between the polarization beam splitter 8 and the light source 3 and rotates the transmitted light by about 45 °. The quarter-wave plate 9 is its optical component. The axis is approximately 45 with respect to the vibration direction of the light of the S-polarized component.
It is arranged according to the direction of °.

In this projection type liquid crystal display device, irradiation light from the light source 3 is irradiated with a quarter wavelength plate 9 and a polarization beam splitter 8.
The image light that has passed through the liquid crystal display panel 1 is magnified by the projection lens 6 and projected onto the screen 7 surface. The light emitted from the light source 3 is as shown in FIG. The light enters the liquid crystal display panel 1 through various paths.

That is, random light A 0 emitted from the light source 3 in various vibration directions first enters the polarization beam splitter 8 through the quarter-wave plate 9. In this case, 1 /
The light transmitted through the four-wave plate 9 is subjected to the optical rotation effect by the quarter-wave plate 9, but the irradiation light from the light source 3 is the random light A
Since it is 0, the light transmitted through the quarter-wave plate 9 is still random light.

The random light A 0 that has entered the polarization beam splitter 8 is P-polarized light (on the drawing) on the beam splitter surface of the polarization beam splitter 8 (the boundary surface between the entrance side prism 8a and the exit side prisms 8b and 8c). It is separated into a linearly polarized light in the vibration direction parallel to the paper surface Ap and an S-polarized light (a linearly polarized light in the vibration direction perpendicular to the paper surface in the figure) As, and the P-polarized light Ap passes through the polarization beam splitter 8 as it is. Then, the light enters the liquid crystal display panel 1. The remaining light, that is, the S-polarized light As, is reflected by the beam splitter surface of the polarization beam splitter 8 and further reflected by the beam splitter surface inclined in the opposite direction, and travels toward the light source 3 side.

The S-polarized light As reflected by the polarization beam splitter 8 toward the light source 3 first passes through the quarter-wave plate 9 and is rotated by about 45 ° by the optical rotation action of the quarter-wave plate 9 to be circularly polarized. It becomes light Ar. The circularly polarized light Ar is reflected by the parabolic reflector 5 of the light source 3, passes through the center of the reflector 5 (center of the light source lamp 4), is reflected again by the parabolic reflector 5, and is again 1/4 wavelength. It is incident on the plate 9.

The circularly polarized light Ar is further rotated by about 45 ° by the optical rotation effect of the quarter-wave plate 9 to become P-polarized light Ap, and this P-polarized light Ap enters the polarization beam splitter 8. Since the light that has entered the polarization beam splitter 8 is P-polarized light Ap, it passes through the polarization beam splitter 8 as it is and enters the liquid crystal display panel 1.

That is, in the projection type liquid crystal display device, the irradiation light from the light source 3 is incident on the polarization beam splitter 8 through the quarter-wave plate 9 so that the polarization beam splitter out of the irradiation light from the light source 3 is incident. The light P of the P-polarized component that passes through 8 is incident on the liquid crystal display panel 1 as it is, and the remaining light, that is, the light As of the S-polarized component reflected to the light source 2 side by the polarization beam splitter 8 is a quarter wavelength plate 9 Once the circularly polarized light Ar has been converted into the circularly polarized light Ar, the circularly polarized light Ar is reflected by the reflector 5 of the light source 3 and again passed through the quarter-wave plate 9 to become the S-polarized light As.
Is incident on the polarization beam splitter 8.

In this way, if the light As of the S-polarized component reflected by the polarization beam splitter 8 toward the light source 3 side is made to enter the polarization beam splitter 8 again as the P-polarized light Ap, this light is also polarized. Can be transmitted and made incident on the liquid crystal display panel 1.

The light transmitted through the polarization beam splitter 8 and incident on the liquid crystal display panel 1 is the light Ap of the P-polarized component.
Therefore, if the TN type liquid crystal display panel 1 is used for displaying by using linearly polarized light of P polarization component as incident light, all the light Ap of P polarization component transmitted through the polarization beam splitter 8 is generated by the liquid crystal display panel 1. Since the light is transmitted through the incident side polarization plate 2a and is incident on the liquid crystal display panel 1, all the light Ap transmitted through the polarization beam splitter 8 can be used for display on the liquid crystal display panel 1.

Therefore, according to the above-mentioned projection type liquid crystal display device, most of the irradiation light from the light source 3 is utilized for display on the liquid crystal display panel 1 without waste, and an image with high brightness is displayed on the liquid crystal display panel 1. The projection image enlarged and projected on the screen 7 surface can be a bright image with high contrast.

In the above embodiment, the liquid crystal display panel 1
Although the incident side polarization plate 2a is provided on the light incident surface of the liquid crystal display panel, the light that passes through the polarization beam splitter 8 and enters the liquid crystal display panel 1 is only the light P of the P polarization component as described above. Even if the incident side polarizing plate 2a is not provided on the light incident surface of the panel 1, the same linearly polarized light as the light transmitted through the incident side polarizing plate 2a is made incident on the liquid crystal display panel 1 and is incident on the liquid crystal display panel 1. Display can be performed.

In the above embodiment, the polarization beam splitter 8 is a combination of three prisms 8a, 8b and 8c.
Even if the two prisms 8d and 8e having the multi-striped prism portions are combined as in the second embodiment shown in FIG. 3, as in the third embodiment shown in FIG. The two triangular prisms 8f and 8g may be combined and the mirror 10 may be provided on the side surface of the incident side prism 8f.

Further, in the above embodiment, the quarter wave plate 9 is used as the optical rotator provided between the polarization beam splitter 8 and the light source 3. As this optical rotator, liquid crystal molecules are twisted at about 45 °. An aligned liquid crystal panel may be used.

[0030]

According to the liquid crystal display device of the present invention, between the light source and the liquid crystal display panel, the light of the P-polarized component of the irradiation light from the light source is transmitted, and the light of the S-polarized component is reflected to the light source side. A polarizing beam splitter that allows the transmitted light to pass through between the polarizing beam splitter and the light source.
By providing an optical rotator for rotating the light, the light of the S-polarized component reflected to the light source side by the polarization beam splitter is also made incident on the liquid crystal display panel as P-polarized light. It is possible to display an image with high brightness on the liquid crystal display panel by utilizing most of the light for display on the liquid crystal display panel without waste, and to obtain an image with high brightness and high contrast.

[Brief description of drawings]

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

FIG. 2 is an enlarged view of a light source unit in FIG.

FIG. 3 is a side view of a light source section of a liquid crystal display device showing a second embodiment of the present invention.

FIG. 4 is a side view of a light source section of a liquid crystal display device showing a third embodiment of the present invention.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... TN type liquid crystal display panel 2a, 2b ... Polarizing plate 3 ... Light source 4 ... Light source lamp 5 ... Parabolic reflector 6 ... Projection lens 7 ... Screen 8 ... Polarizing beam splitter 9 ... Quarter wave plate (optical rotator) 10 ... Mirror A0 ... Random light Ap ... P-polarized light As ... S-polarized light Ar ... Circularly-polarized light

Claims (1)

[Claims] 1. A liquid crystal display device comprising a liquid crystal display panel, a light source comprising a light source lamp and a reflector for reflecting light emitted from the light source lamp toward the liquid crystal display panel, wherein the light source and the liquid crystal display panel are provided. A polarizing beam splitter that transmits the P-polarized component light of the irradiation light from the light source and reflects the S-polarized component light toward the light source is disposed between the two, and the polarization beam splitter and the light source are separated from each other. A liquid crystal display device characterized in that an optical rotator for rotating transmitted light by about 45 ° is provided therebetween.