JPH055881A - Liquid crystal projector - Google Patents

Abstract

PURPOSE:To prevent the thermal deterioration of polarizing plates and the degradation in transmittance by using the polarizing plates of dye systems only for the polarizing plates and using polarizing plates of iodine systems having excellent optical characteristics for the polarizing plates. CONSTITUTION:The respective rays of green (G), blue (B) and red (R) are made incident via a condenser lens 61 on the polarizing plates 62B, 62G, 62R of the dye systems dyed with the dyes polarizing the light of the same frequency bands as the frequency bands of the light to be spectrally split, respectively near a light source 50. Only the rays of the polarization in a specified direction are made incident on liquid crystal panels 55 to 57. The liquid crystal panels 55 to 57 are driven by respective color signals of blue (B), green (G), red (R) and change the polarization directions of the transmitted rays according to the color signal levels. The quantities of the light transmitted through the polarizing plates 63B, 63G, 63R of the iodine systems are the quantities corresponding to the respective signal levels of the blue (B), green (G), red (R). The polarizing plates 62B, 62G, 62R of the dye systems, the liquid crystal panels 55 to 57 and the polarizing plates 63B, 63G, 63R of the iodine systems of such optical system have respectively the same functions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal projector, and more particularly to a liquid crystal projector which prevents image deterioration in color.

[0002]

2. Description of the Related Art In recent years, with the spread and diversification of AV media, high pixel / large screens have been aimed. In particular, clear-vision and high-definition experimental broadcasts have begun, and projectors using three liquid crystal panels are receiving attention. As the literature, for example, Journal of the Television Society of Japan, Vol. 45, No. Two
(1991) "Liquid crystal projection display" and the like describe these technologies in detail.

FIG. 1 schematically shows a three-plate mirror type optical system. Light from a light source (50) such as a metal halide lamp passes through a reflection mirror (51), a heat ray, an ultraviolet ray cut filter (52), and a dichroic mirror (5).
Reach 3). This dichroic mirror (5
3) has a function of reflecting or transmitting light in a specific wavelength range, only blue (B) light changes its direction by 90 ° and is reflected, and other light is transmitted. The transmitted light is incident on the dichroic mirror (54), only the green (G) light is reflected, and the transmitted light becomes red (R). Thus, B. G. The respective lights dispersed in the order of R are the liquid crystal panels (55), (5
6) and (57). Each panel (55), (5
In 6) and (57), the video corresponding to each color is reproduced, and the incident light is combined for each color after being modulated.

The dichroic mirror (58) reflects the G light and combines it with the transmitted B light, and the dichroic mirror (59) combines it with the R light. The combined light is projected onto the screen by the projection lens (60). Here, (61) is a condenser lens for narrowing the light to the projection lens (60). Further, (61) is a reflection mirror.

On the other hand, dedicated liquid crystal panels (55), (5
6), the first polarizing plate (62B) on the incident surface of (57),
(62G) and (62R) are provided, and second polarizing plates (63B), (63G) and (63R) are provided on the opposite surface. As the first and second polarizing plates (62) and (63), a PVA film is dyed with an iodine solution, stretched in a certain direction, and PVA molecules and polyiodine are arranged in the stretching direction so as to have a polarizing function. Iodine-based polarizing plate, P
There is provided a dye-based polarizing plate having a polarizing function by adsorbing a dichroic dye on VA and then uniaxially stretching it to arrange the dye molecules together with the PVA molecules in the stretching direction. Generally, an iodine-based polarizing plate is more excellent in optical performance and a high contrast ratio can be obtained, so that the iodine-based polarizing plate is mainly used for a liquid crystal projector.

The first polarizing plate (62) is a light source (50).
The light beam from is decomposed into two linearly polarized light beams that are orthogonal to each other, the component parallel to the polarization direction is transmitted, and is incident on the liquid crystal panel. The second polarizing plate (63) transmits only the light beam polarized in a certain direction among the light beams transmitted through the liquid crystal panel.
When image information is input to the liquid crystal panel, the local orientation of the liquid crystal of the liquid crystal panel changes according to the image information,
It changes the plane of polarization of light rays incident on the liquid crystal panel. Then, the local alignment change of the liquid crystal of the liquid crystal panel is obtained as visible information from the second polarizing plate (63) and projected on the screen through the projection lens (60).

[0007]

FIG. 3 shows the initial and 70 states.
The parallel and orthogonal transmittances of the iodine type polarizing plate after storage at 200 ° C. for 200 hours are shown. As shown in the figure, the orthogonal transmittance of the iodine type polarizing plate has a wavelength of 600 nm due to the sublimability of iodine molecules.
Greater than above. Therefore, it is used in a poor environment,
Although high cost is required as a polarizing plate for in-vehicle liquid crystal display devices that require reliability, dye-based polarizing plates are used, and low cost is required for polarizing plates for liquid crystal projectors that require high resolution and high brightness. An iodine-based polarizing plate, which has good optical characteristics in the initial stage, is mainly used.

However, with the increase in screen size and brightness of liquid crystal projectors, deterioration of heat generated by the polarizing plates of the liquid crystal projector has become an important issue. Further, the deterioration tendency of the optical characteristics is particularly remarkable on the long wavelength side, and there is also a problem that the color tone of the projected image changes (especially, a red void occurs) with the deterioration of the polarizing plate. On the other hand, since the dye wants to transmit all wavelengths, a large number of first dyes that polarize red light, second dyes that polarize green light, and third dyes that polarize blue light are mixed. In addition, a gray color was made and used as a polarizing plate (black dye type polarizing plate).

However, the dyes are the first, second and third dyes.
Since the dye etc. are mixed, the dye is substantially tripled or more, and the absorptivity of this dye increases correspondingly, and there is a problem that the transmittance decreases as a whole. The same can be said for other optical systems, especially when displaying white, there was a problem that the screen became dark.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and is a dye-based polarizing plate comprising a dye that polarizes light in a frequency band substantially the same as the frequency band of each transmitted light. If the problem is solved by providing the above, and the deterioration of optical characteristics is considered, the problem can be solved by using this dye-based polarizing plate as the polarizing plate on the light incident side and the iodine-based polarizing plate on the other side. is there.

[0011]

Since the principle is the same for all optical systems, the blue optical system will be described here. In particular, the yellow or red dichroic dye blocks light in the blue frequency band when the two polarizing plates are stretched at 90 degrees, and cuts light in the blue frequency band when the stretching directions are parallel. To Penetrate. Therefore, if a dye that polarizes light of substantially the same frequency band as this light into the polarizing plate used for the B (blue) optical system when the polarization directions are parallel is used, most of the incident blue light is , Not absorbed but transmitted. Moreover, since the dye is not mixed with the first, second and third dyes and is independent, the dye is practically 1/3 times or less, and the absorptivity of this dye is reduced accordingly. The transmittance is increased as a whole.

The same applies to the other two polarizing plates. On the other hand, when the dye-based polarizing plate is used only in the polarizing plate arranged near the light source, the problem of aging due to heat generation is solved, and in consideration of thermal deterioration of the iodine-based polarizing plate, it is sufficient as a whole. Optical performance can be achieved.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described with reference to FIG.
The output light of the optics (50) using a metal halide lamp is a cold mirror reflector (51) and an ultraviolet ray cut filter (52) to cut infrared rays and ultraviolet rays, and then blue (B) with a first dichroic cllar (53). Are separated, and green (G) is separated by the second dichroic mirror (54) to be separated into three primary colors.

Light rays of green (G), blue (B), and red (R) are incident on dye-based polarizing plates (62B), (62G), and (62R) through a condenser lens (61), respectively. , Liquid crystal panel (5
5), (56), and (57). The liquid crystal panels (55), (56), (57) are blue (B), green (G),
It is driven by each color signal of red (R) and changes the polarization direction of the transmitted light beam according to the color signal level. Therefore, the amount of light transmitted through the iodine type polarizing plates (63B), (63G) and (63R) depends on the signal level of each color of blue (B), green (G) and red (R). In this optical system, dye-based polarizing plates (62B), (62G) and (62R), liquid crystal panels (55), (56) and (57), and iodine-based polarizing plates (63B) and (63G), (63R) have the same function.

Next, iodine type polarizing plates (63B), (63
The blue (B), green (G), and red (R) rays that have passed through G) and (63R) are sequentially combined by the third dichroic mirror (58) and the fourth dichroic mirror (59). Then, it is projected on a screen (not shown) through the projection lens (60). FIG. 2 shows a polarizing plate (62
B), (62G), (62R) and polarizing plate (63B),
(63G) and (63R) show the parallel spectral characteristics and orthogonal spectral characteristics of a conventional example using all iodine-based polarizing plates, and the broken line shows the characteristics after 200 hours at 70 ° C. Further, FIG. 3 shows the optical characteristics when a dye-based polarizing plate was used for all of the polarizing plates and after storage at 70 ° C. for 200 hours,
In FIG. 4, dye-based polarizing plates are used for the polarizing plates (62B), (62G) and (62R), and the polarizing plates (63B) and (63B) are used.
G) and (63R) show optical characteristics at the initial stage and at 70 ° C. for 200 hours when iodine type polarizing plates are used. The horizontal axis of the figure represents wavelength (unit: nm), and the vertical axis represents transmittance (unit:%).

As is clear from the comparative reference of FIGS. 2 to 4, the liquid crystal projector of the present invention whose optical characteristics are shown in FIG. 4 has the same durability as the case where dye-based polarizing plates are used for all the polarizing plates. Is obtained. Further, although the optical initial characteristics are inferior to the case where iodine type polarizing plates are used for all the polarizing plates, considering that the orthogonal transmittance greatly changes in the wavelength region of 600 nm or more of the iodine type polarizing plates, it is The optical characteristics are superior to those of the liquid crystal projector.

On the other hand, in the above-mentioned constitution, the dye is an azo type or anthraquinone type, and the dye type polarizing plate (63B) is dyed with a yellow dichroic dye or a red dichroic dye. , The dye-based polarizing plate (63G) is dyed with a red dichroic dye or a blue dichroic dye, and the dye-based polarizing plate (63R) is dyed with a blue-green dichroic dye or blue. The dichroic dye is dyed.

Since the dyes used in each of these optical systems have the same principle, the dye used in the blue optical system will be described below. FIG. 5 is a diagram showing the spectral characteristics of a polarizing plate that polarizes blue to which a yellow dichroic dye is adsorbed, and FIG. 6 is a polarizing plate that polarizes blue to which a red dichroic dye is adsorbed. It is a figure which shows a spectral characteristic.
Here, the solid line is when the stretching direction is 90 degrees, and the dotted line is when the stretching direction is parallel. As is clear from this characteristic diagram, when the polarization directions are parallel, light in the blue frequency band is transmitted. Therefore, when a dye of this color is used in the liquid crystal panel of the blue optical system, the projection lens (60) can be used. The image of the blue light projected through the screen becomes brighter than that when a conventional black polarizing plate is used. Moreover, since the amount of the dye is about 1/3 or less than that of the conventional one, the absorptivity of the dye as a whole is lowered and the dye becomes brighter. Further, even when the stretching direction is 90 degrees, the absorbance of blue light becomes large, so that good contrast can be obtained.

Although the liquid crystal projector of the mirror sequential arrangement system has been described as the embodiment, the present invention can be applied to the liquid crystal projector of the prism system. In addition, the present application
A dye-based polarizing plate was used as the polarizing plate disposed near the light source. However, if one polarizing plate is used, the transmittance can be improved although the optical characteristics are inferior.

[0020]

According to the present invention, the dye type polarizing plate is used only for the polarizing plate which is arranged at a position close to the light source, absorbs half of the incident light as heat energy and generates heat, and is arranged behind the liquid crystal panel, Since an iodine-based polarizing plate having excellent optical characteristics is used as a polarizing plate in which heat generation is hardly a problem, the problems of optical performance, reliability and cost can be solved at the same time.

Moreover, by using the dye of the above-mentioned color for the dye-based polarizing plate of each optical system, the color of the frequency band substantially the same as the light of each optical system is polarized, so that the transmittance in the optical characteristics is Has the effect of increasing the brightness and finally making the projected image brighter.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is an optical characteristic diagram of a conventional liquid crystal projector using an iodine-based polarizing plate.

FIG. 3 is an optical characteristic diagram of a liquid crystal projector using a dye-based polarizing plate.

FIG. 4 is an optical characteristic diagram of an example of the invention.

FIG. 5 is a spectral characteristic diagram of a polarizing plate that polarizes blue light to which a yellow dye is adsorbed.

FIG. 6 is a spectral characteristic diagram of a polarizing plate that polarizes blue light to which a red dye is adsorbed.

[Explanation of symbols]

 50 light source 51 cold mirror reflector 52 ultraviolet cut filter 53, 54 dichroic mirror 55, 56, 57 liquid crystal panel 58, 59 dichroic mirror 60 projection lens 61 condenser lens 62 dye-based polarizing plate 63 iodine-based polarizing plate

Claims (1)

Claims: 1. A liquid crystal panel dedicated to each of the three primary colors of red, green, and blue is provided, and light modulated by each liquid crystal panel is combined and projected onto a screen by a projection lens. In the liquid crystal projector, the liquid crystal panel is provided with a dye-based polarizing plate made of a dye that polarizes light having a frequency band substantially the same as the frequency band of each separated light. .. 2. The deflection plate is provided on a light incident side,
2. The liquid crystal projector according to claim 1, wherein the other deflection plate is an iodine deflection plate.