JPS62257123A - Projection type display device - Google Patents

Abstract

PURPOSE:To obtain an excellent gradational display and a projection image with a little color deviation by using liquid crystal to which dichroic coloring matter having a 580-650nm wavelength of absorption is added and mixed for a twisted nematic liquid crystal valve. CONSTITUTION:A projection display device consists of three twisted nematic (TN) liquid crystal light valves equipped with polarizing plates 1 which form images by using color beams of red, green, and blue, an optical system which mixes the color light beams, and a projection optical system; and the TN liquid crystal 5 to which the dichroic coloring matter 5 having a 580-650nm main wavelength of absorption is used for the three TN liquid crystal valves. Further, 0.5-3.0wt% dichroic coloring matter 4 is added and mixed. The dichroic coloring matter 4 has its long-axis direction arrayed in parallel to molecule axes of the liquid crystal and incident light is absorbed according to the coefficient of absorption in the long-axis direction of the coloring matter when propagated in the liquid crystal in the absence of an electric field and at the time of low voltage application. Consequently, the wavelength dependency of transmissivity is reduced and color deviation is decreased.

Description

[Detailed description of the invention] [Industrial application fields] 1. The present invention relates to a projection display device.

[Summary of the Invention] The present invention provides a projection display device using three twisted nematic liquid crystal light valves each equipped with a polarizing plate in order to form an image using red, green, and blue colored lights. Among the bulbs, at least the red light bulb uses a TN liquid crystal with 0.5 to 3.0% by weight of dichroic dye, which has a main absorption wavelength of 580 to 650 nm, to improve brightness. It is possible to reduce the wavelength dependence of transmittance due to birefringence of twisted nematic liquid crystals in intermediate tones without damaging the image quality, making it possible to obtain projected images with good gradation display and excellent color purity. That is.

[Prior Art] A projection type display device using a plurality of conventional twisted nematic liquid crystal light valves converts collimated light from a light source into red (R), green (G), and blue (B) through a guichroic mirror. ) is separated into each color component, each color component is light switched using a twisted nematic liquid crystal light valve, the R-G-B color components are combined again via a dichroic mirror, and a projection optical system produces a projected image. It forms the The above twisted nematic liquid crystal light valve has a polarizing plate arranged so that the incident light side is parallel to the alignment axis, and the output light side is arranged perpendicular to the alignment axis, and the threshold voltage (vth) The light transmittance is controlled by applying the above voltage.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional technology, due to wavelength dependence due to optical rotational dispersion of liquid crystal, the safe light shielding region where the residual transmittance is 0 in the absence of an electric field is smaller than the visible wavelength region. It is limited to a narrow wavelength range, and there is residual transmission in other wavelength ranges, so black is not completely black, and furthermore, at low applied voltage, long wavelength light 580 ~ 65
There is a problem in that the transmission around 0 nm, that is, the transmission of the liquid crystal light valve for red light takes priority, resulting in a reddish display.

The present invention is intended to solve these problems, and its purpose is to reduce residual transmission to bring black closer to complete black, and to reduce long wavelength light (58%) at low applied voltages.
By reducing the transmission of wavelengths (0 to 650 nm), it is possible to provide a projected image with good gradation display and less color shift.

[Means for Solving the Problems] The projection type display device of the present invention comprises three twisted nematic liquid crystal light valves each equipped with a polarizing plate to form an image using red, red, and blue colored lights, and the above-mentioned colored lights. In a projection display device consisting of an optical system for synthesizing and a projection optical system, a TN liquid crystal containing a dichroic dye having a main absorption wavelength of 580 to 650 nm is used in the three TN liquid crystal light valves. # sign.

Furthermore, the dichroic dye is added in an amount of 0.5 to 3.0% by weight.

[Function] When a dichroic dye having a dominant absorption wavelength of 580 to 650 nm is added and mixed with twisted nematic liquid crystal, the dichroic dye is aligned so that its long sleeve direction is parallel to the molecular axis of the liquid crystal. Therefore, when there is no electric field or when a low applied voltage is applied, when incident light propagates through the liquid crystal, it is absorbed according to the absorption coefficient in the long axis direction of the dye, so the wavelength dependence of transmittance is reduced and color shift is reduced. On the other hand, when a voltage higher than the saturation electric field is applied, the molecular axes of the liquid crystal are aligned in the direction of the electric field, and the long sleeve direction of the dye molecules is also aligned in the direction of the electric field. At this time, the incident light is absorbed and emitted according to the absorption coefficient in the short axis direction of the dye. However, in reality, the absorption coefficient of the pigment in the minor axis direction is small, and the color shift is not corrected because the pigment is emitted without being absorbed.
By adding and mixing a dichroic dye having a main absorption wavelength of 650 nm, good gradation display with less color shift can be achieved.

The concentration of the dichroic dye used in the present invention is 0.5 by weight.
If it is less than 3%, the dye absorption will not be sufficient and the color shift will be corrected considerably, so the effect of addition will not be obtained.On the other hand, if it exceeds 3:0%, the dye absorption will increase, the brightness will decrease, and at the same time the driving voltage will change. The above-mentioned range is desirable because the

[Example 1] This example will be described below based on drawings and tables. 1st
The figure is a cross-sectional view of a twisted nematic liquid crystal light valve, in which a polysilicon thin film transistor (TP) is mounted on a transparent quartz substrate 2 as a means to control the electro-optic effect of the liquid crystal.
T) 3 was formed into a matrix shape to create a TPT substrate 0
Next, a light-shielding layer 8 was formed on the transparent substrate 9 by metal vapor deposition to shield parts other than the pixel electrodes, and a transparent electrode 7 was formed on the light-shielding layer by physical vapor deposition to create a counter substrate. After spin-coding polyimide as an alignment film on the above TPT substrate and counter substrate, a rubbing treatment was performed, and a liquid crystal cell was fabricated using the spacer 6 and a gap agent under the manufacturing conditions shown in Table 1. Table 1 also shows the conditions for the liquid crystal 5 to be sealed and the dichroic dye 4 to be added and mixed.

The polarizing plate 1 was arranged so that the incident light side was parallel to the rubbing direction, and the output light side was arranged perpendicular to the rubbing direction.

FIG. 2 is a graph of the dependence of the display characteristics of the light valve on the concentration of the dichroic dye, where 1 is the dependence of brightness on the concentration and 2 is the dependence of color shift on the concentration. As is clear from this graph, the amount of dichroic dye added is 0.5
The twisted nematic liquid crystalline of the present invention is in the range of ~3.0 wt%!・The valve is! The low C of 1 degree is slight, and on the other hand, the color shift in the middle tone is large.

By using a liquid crystal containing a dichroic dye with a main absorption wavelength of 580 to 650 nm, the wavelength dependence of transmittance is reduced, and the red region, which was conventionally transmitted preferentially at low applied voltages, is used. This is thought to be the result of suppressing the penetration of Note that if the amount of dichroic dye added is less than 0.5 wt%, color shift will be large and the effect of addition will not be obtained, and conversely, 3.
If it exceeds 0 wt%, the brightness will decrease and this is not practical.

A projection type display device was fabricated using three twisted nematic liquid crystal light bulbs fabricated under conditions 2 in Table 1. The optical system configuration diagram is shown in FIG. and separate into R, G, and B components. The separated components are transferred to R-
The light is made incident on the twisted nematic liquid crystal light valve for G and B, and is combined again by the guichroic mirrors 5 and 6, and a projected image is obtained by the projection lens 8.

Figure 3(a) is a transmittance characteristic diagram of a twisted nematic liquid crystal light valve with dichroic dye added.
b) is a transmittance characteristic diagram of a conventional twisted nematic liquid crystal light valve.

As is clear from these two drawings, the wavelength dependence of transmittance is significantly reduced by using a twisted nematic liquid crystal light valve with a dichroic dye added and mixed with a dichroic dye having a main wavelength of absorption in the range of 580 to 650 nm. The spectral curve was reduced and neutral optical switching became possible.

Figure 4 shows the chromaticity diagram of C, I, and E, where l is the conventional T.
2 is a chromaticity curve when the voltage of the N liquid crystal light valve is varied, and 2 is a chromaticity curve when the voltage of the TN liquid crystal light valve mixed with a dichroic dye is varied. It can also be seen from this figure that the color shift is clearly reduced. Therefore, the projected image of the projection image display device of this example, which was manufactured using three TN liquid crystal light valves to which a dichroic dye having a main absorption wavelength of 580 to 650 nm is added, is as follows.

It had excellent color purity and gradation display.

Also, the color shift of the image due to the coloring of the halogen lamp itself,
In particular, color shift when self-displaying was performed by applying a voltage higher than the saturation electric field could be corrected by mixing the dichroic dye. This is thought to be due to absorption in the minor axis direction of the dichroic dye suppressing transmission of the red region of the halogen lamp, resulting in flat spectral characteristics.

[Example 2] A liquid crystal cell was obtained in the same manner as in Example 1. However, in this example, only the light bulb for red light has a wavelength of 850 to 650 nm.
is filled with TN liquid crystal mixed with 1.0% by weight of dichroic dye having the main wavelength of absorption, and the remaining green and blue light bulbs are filled with TN liquid crystal with no dichroic dye added. was sealed to obtain three R-G-B twisted nematic liquid crystal light valves. A projection type display device was manufactured using three twisted nematic liquid crystal light valves.

FIG. 5 is a diagram showing the configuration of the optical system. Incident light a from a metal halide lamp with an elliptical mirror is passed through a heat ray reflection filter 2, separated into B, R, and G by a dichroic mirror 9, and R and G by a dichroic mirror IO. R passes through a heat ray transmission filter 11, and G-B
is directly focused by the lens 3. The R and B lights condensed by the lens 3 are reflected by the mirror 4, and the G lights are made to enter the respective light valves 7 in a straight line.

The light emitted from each light valve was combined through dichroic mirrors 5 and 6 and combined again, and a projected image was obtained through a projection lens 8.

The projected image obtained in this example also had excellent one-color purity and gradation display.

[Effects of the Invention] As explained above, the present invention uses a twisted nematic liquid crystal light valve with a dichroic dye having a main wavelength of absorption in the range of 580 to 650 nm, thereby producing a neutral color with no hue. Optical switching becomes possible, and the projected image of the projection display device using the above three light valves has excellent color purity and gradation display, and also has the effect of correcting the chromaticity of the backlight itself. It is characterized in that an RGB correction circuit is not required and the panel manufacturing process is further simplified.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a twisted nematic liquid crystal light valve 1, polarizing plate 2, quartz substrate 3, polysilicon thin film transistor 4, dichroic dye 5, twisted nematic liquid crystal 6, spacer 7, transparent conductor Mt, film 8. Light shielding layer 9, transparent substrate FIG. 2 is a graph of the dependence of the display characteristics of a light valve on the concentration of dichroic dye. 1. Dependence of # degree on density 2. Dependence of coloring on density S3 Figure (a) is a transmittance characteristic diagram of a twisted nematic liquid crystal light valve to which a dichroic dye is added. FIG. 3(b) is a transmittance characteristic diagram of a conventional twisted nematic liquid crystal light valve. Figure 4 is a chromaticity diagram of C, 1, and H. 1. Chromaticity curve of conventional TN liquid crystal light valve 2. Chromaticity curve of TN liquid crystal light pulp mixed with dichroic dye FIG. 5 is a diagram of the optical system configuration of a projection display device. °1. Halogen lamp 2, heat transmission filter 3, lens 4, mirror 5.6. Tychroic mirror 7, twisted nematic liquid crystal light valve 8, projection lens 9, incident light FIG. 6 is a diagram showing the configuration of the optical system of the projection type display device. 1, metal halide lamp 2, heat ray reflection filter 3, lens 4, mirror 5.6.9.10. Guicroic mirror 7, twisted nematic liquid crystal light valve 8, projection lens 11, heat ray transmission filter 12, more than incident light Applicant Seiko Epson Corporation 1-10 Figure 2'; Figure 3 (b) Father 41st! !

Claims (2)

[Claims] (1) A projection type display consisting of three Twistedmatic (TN) liquid crystal light valves equipped with polarizing plates to form images using red, green, and blue colored lights, an optical system that combines the colored lights, and a projection optical system. In the device, at least the red light bulb among the three liquid crystal light bulbs,
A projection type display device characterized by using a TN liquid crystal mixed with a dichroic dye having a main absorption wavelength of 580 to 650 nm. (2) The projection type display device according to claim 1, wherein the dichroic dye is added and mixed in a weight ratio of 0.5 to 3.0%.