JPH0792566A - Polarizing screen - Google Patents

Abstract

PURPOSE:To provide a polarizing screen which has a high video contrast and a high efficiency of utilizing video light and enables many viewers existing side by side and facing the screen to clearly view liquid crystal videos even in relatively bright environment. CONSTITUTION:This polarizing screen consists of a polarizing woven fabric woven with polarizing fibers 1 and non-polarizing fibers 2 respectively as warp and weft or weft and warp. The polarizing fibers 1 of this polarizing woven fabric are so arranged that the longitudinal direction thereof is approximately perpendicular to the horizontal plane to expand a horizontal visual field angle. The polarizing fibers 1 are woven as warp sating or weft satin in such a manner that the exposed surfaces faces the video viewers to enhance the function as the 'polarizing filter' of the polarizing woven fabric.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screen used in an image system or the like equipped with a liquid crystal display and having a polarizing function of selectively reflecting (transmitting) light in accordance with a polarization direction.

[0002]

2. Description of the Related Art A liquid crystal image system is "small in size so that it can be installed in a relatively narrow space", "lightweight and easy to move", and "digital image processing" as compared with a CRT image system. However, due to the low utilization efficiency of light, the contrast of the image is insufficient in the environment where the illumination light is strongly reflected on the screen, especially for large-screen liquid crystal projection images. The effect of low contrast is great, forcing us to view images in a dark room.

In a normal liquid crystal image system, non-polarizing white light generated by a light source made of a metal halide is divided into three primary colors by a dichroic prism and then converted into linearly polarized light by a light absorbing linear polarizer. Then, it is incident on the liquid crystal light valve, the voltage modulated by the video signal is applied to rotate the plane of polarization (electric field oscillation) of linearly polarized light, and then the plane of polarization is analyzed through the analyzer (linearly polarized light). Since the image is created by the method of emitting the rotation angle component, the amount of light loss is large.

[0004]

Therefore, in order to enhance the contrast of the image on the screen by reducing the reflection amount of the illumination light without impairing the image light, various techniques relating to the polarizing screen have been developed. For example, a technology in which a polarizer and a 1 / 4-wave plate are laminated to prevent the emission of illumination light that enters the screen (see US Pat. No. 2,362,573), the illumination light source is covered with a polarizer, and the electric field vibration surface of transmitted polarization is A technique for covering the screen with a polarizer that is orthogonal to the above (see US Pat. No. 2,793,361), a technique for covering the image light source with a polarizer, and a screen for covering the screen with a polarizer in which the electric field oscillating plane of the transmitted polarized light is aligned with it. U.S. Pat. No. 3,319,519), the image light source is covered with a polarizer, and the screen is covered with a polarizer in which the electric field vibration surface of the transmitted polarized light is matched with the electric field vibration surface of the transmitted polarized light. A technique for covering illumination light with a polarizer orthogonal to the polarizer (see Japanese Patent Laid-Open No. 50-98831), and a technique for disposing an analyzer for liquid crystal images on the surface of a screen (Japanese Patent Laid-Open No. 51-71697). , See the screen with a polarizer in which the electric field vibration plane of the transmitted polarized light matches the linearly polarized light of the liquid crystal image, and align the electric field vibration plane vertically.
A technology for efficiently removing the illumination light emitted from the ceiling of the projection room (see Japanese Patent Laid-Open No. 61-38976), and a screen with a polarization beam splitter array in which the electric field oscillation plane of the transmitted polarization is made to match the linear polarization of the liquid crystal image. Technology (Japanese Patent Laid-Open No. 3-2872)
No. 44), a technique for disposing a polarizer having light absorption characteristics adapted to wavelength dispersion of three primary colors generated in a liquid crystal panel on a surface of a screen (see JP-A-4-63333), and a fine polarizer. There is known a technique of arranging an alternating array of fine light absorbers on a screen (see Japanese Patent Laid-Open No. 4-29127). These film-based polarizing screens have a problem that the viewing angle in the horizontal direction is generally small and it is difficult for many people to view an image when they face the screen side by side.

On the other hand, in order to put a screen into which a liquid crystal image can be clearly seen in a bright environment into practical use, not only the contrast of the image is enhanced but also the screen can be easily enlarged and the winding property is high. Is also required. As a means to comprehensively realize these conditions,
A technique for forming a screen with a polarizing woven cloth having the function of a polarizing lens array (see Japanese Patent Application Laid-Open No. 5-197026) has been developed. In such a woven cloth type polarizing screen, it is necessary to further enhance the efficiency of removing illumination light and make the luminance of an image within a predetermined viewing angle as high and uniform as possible to enhance the utilization efficiency of the image light.

The present invention has been made in view of the above problems and has a high image contrast and a high utilization efficiency of image light, and even in a relatively bright environment, a large number of viewers face each other side by side. It is an object of the present invention to provide a polarizing screen that allows clear viewing of liquid crystal images.

[0007]

A polarizing screen of the present invention for solving the above-mentioned problems comprises a polarizing woven fabric in which polarizing fibers and non-polarizing fibers are woven as warps and wefts or wefts and warps, respectively. The polarizing fibers in the cloth are arranged such that the longitudinal direction thereof is substantially vertical to the horizontal plane, and the polarizing fibers are arranged so that the exposed surface of the polarizing fibers faces the image viewer. Alternatively, it is woven as a weaving satin.

[0008]

[Function] In a normal projection environment, the half-value width of the vertical viewing angle is 10
Around 1 ° is sufficient, but it is desirable that the horizontal viewing angle is as large as possible (half-value width of 30 ° or more). Regarding a polarizing fiber that constitutes a screen made of a polarizing woven fabric in which the weaving density of the polarizing fiber is increased by the satin weaving structure, the cross-sectional structure is a minute circular or elliptical shape, whereas the fiber axial direction (longitudinal direction) is Since the swell is relatively gentle, the light incident on the fiber is likely to be emitted at a wide angle in the fiber cross section rather than in the fiber axial plane. Therefore, when the axes of the polarizing fibers of the polarizing woven fabric are arranged vertically with respect to the horizontal plane, the vertical viewing angle of the image light becomes relatively small and the horizontal viewing angle becomes considerably large. In addition, since the polarizing woven fabric is woven by weaving the polarizing fiber as warp or weft satin so that the surface where the polarizing fiber is exposed faces the image viewer, a polarizing woven fabric is a high filter. The effect can be exerted and the reflection of the illumination light on the screen surface can be suppressed.

According to the present invention, it is possible to particularly efficiently remove light that is incident substantially horizontally from the window provided on the side wall of the projection room. Note that the incident angle of the illumination light on the screen by an electric light or the like in a normal projection state is the Brewster polarization angle (for example, the polarization angle at the reflecting surface having a refractive index of 1.52 is 56 °.
Since it is often smaller than 40 '), the practical obstacle caused by such illumination light can be ignored.

[0010]

[Example] Transparent single fiber having no polarization (non-polarization fiber)
Fig. 1 shows a polarizing woven fabric in which weft satin weaving using warp yarns and polarized single fibers as weft yarns. As shown in FIG. 1, the structure of this woven fabric is mainly the surface where the polarizing fiber 1 is exposed (hereinafter, this surface is referred to as “surface”).
It is defined as ) And the surface where the transparent fiber 2 is mainly exposed (hereinafter,
This side is defined as "back side". ) Depends on. This polarizing woven fabric is calendered to shape the cross section of the fiber into an elliptical shape, and then, as shown in FIG. 2, both sides of the polarizing woven fabric are covered with transparent resin 3, and visible on the resin layer on the back surface. The light reflection layer 4 was formed. Next, the resin sheet 6 was attached to the visible light reflection layer 4 using the adhesive 5. The polarizing woven fabric subjected to the above processing was cut, and the winding jig 7 was mounted on the polarizing woven fabric to prepare a reflective polarizing screen 8. FIG. 4 shows an example in which the reflective polarizing screen 8 is arranged in the projection space. Here, the polarizing fibers 1 in the polarizing woven fabric are arranged such that the longitudinal direction thereof is substantially vertical to the horizontal plane, and the surface is arranged so as to face the image viewer. According to the reflective polarizing screen 8 of this embodiment,
Most of the image light 12 and the illumination light 13 having the polarization direction (electrolytic vibration plane) orthogonal to the longitudinal direction of the polarizing fiber 1 projected from the liquid crystal image projector 10 passed through the polarizing fiber 1 on the image viewer side. After entering the transparent fiber 2, the polarization fiber 1 of the illumination light 13
Since light having the same polarization direction (electrolytic vibration plane) as the longitudinal direction of is absorbed by the polarizing fiber 1, the surface reflection of the illumination light can be effectively suppressed. It is to be noted that the illumination light source is covered with a polarizer in which the electric field oscillation plane of the transmitted light is orthogonal to the polarizing screen (for example, a polarizing curtain made of the polarizing woven fabric used in the present invention, a polarizing blind, a polarizing louver, etc.), and the illumination light is linearized. By converting to polarized light, surface reflection of illumination light can be further suppressed.

Here, as the polarizing woven fabric, 6-nylon transparent single fiber (fineness 30dr) is used as warp (woven density 95 / inch),
Polarized monofilament of polyvinyl alcohol (fineness 90dr) spun and stretched by adding 0.10% of dichroic dye was used as weft (weaving density 220 yarns / inch) under the condition of 3 fly 8 weft satin weave and weave width 1760mm. Using a woven fabric, polyurethane resin 3 (15 g / m ² ) is used as the transparent resin 3 coated on both sides of the polarized woven fabric, and aluminum is vapor-deposited (thickness: about 1000 angstrom) to form a resin layer on the back surface. The reflection type polarizing screen produced by forming the visible light reflecting layer 4 formed on the above and using a soft polyvinyl chloride sheet (thickness 0.30 mm) for the resin sheet 6 is composed of linearly polarized light whose electric field vibration surface is horizontal. The result of measuring the luminance distribution with respect to the image light is shown in FIG. As shown in Figure 3, the horizontal viewing angle
The full width at half maximum of 14 was significantly larger than that at vertical viewing angle 15. Further, it can be seen that the image brightness is distributed smoothly within a predetermined horizontal viewing angle, and is drastically reduced outside this horizontal viewing angle, and the utilization efficiency of the image light is high.

As raw material fibers, transparency to visible light is indispensable, and it is required that the warp yarns have sufficient strength for weaving and the weft yarns have the flexibility to withstand high-density weaving, but these conditions are satisfied. The type of fiber material is not limited, as long as it is 6-nylon and polyvinyl alcohol, 6,6-nylon, ethylene-vinyl alcohol copolymer, cellulose, polyethylene terephthalate, polybutylene terephthalate and other fibers. Can be used. As the polarizing fiber, the high dispersibility of dichroic dye and 70
It is preferable to have a polarization degree of not less than%.

A transmission type polarizing screen can be manufactured by omitting the steps after the formation of the visible light reflecting layer in the step of manufacturing the above-mentioned reflection type polarizing screen. FIG. 5 shows an example in which the transmissive polarizing screen 9 is arranged in the projection space. In FIG. 5, a transmissive polarizing screen 9 is used as the screen of the rear projection type liquid crystal image display device 11. In this video system,
If moire fringes occur on the image surface due to the interaction between the fiber array of the polarized woven fabric and the pixel array of the projected image due to the short distance from the liquid crystal panel to the screen, the maximum fiber diameter should be This can be solved by making the pixel period on the projection plane as small as possible.

[0014]

As described above, in the polarizing screen of the present invention, since the polarizing fiber is installed on the viewer side of the image, the illumination light can be easily removed. Further, in this polarizing screen, since the polarizing fibers are arranged vertically with respect to the horizontal plane, the horizontal viewing angle of the image becomes large, and the image brightness is distributed comparatively gently within a predetermined horizontal viewing angle. However, this luminance is significantly reduced outside the predetermined viewing angle. As a result, the contrast of the image and the utilization efficiency of the image light are significantly improved, and even in a relatively bright environment, a large number of viewers can see the liquid crystal image clearly side by side facing the screen.

[Brief description of drawings]

FIG. 1 is a diagram showing a front surface and a back surface of a polarizing woven fabric adopted in the present invention.

FIG. 2 is a cross-sectional view showing a layer structure of a reflective polarizing screen according to the present invention.

FIG. 3 is a characteristic diagram illustrating a luminance distribution of a reflective polarizing screen according to the present invention with respect to image light composed of linearly polarized light whose electric field vibration surface is horizontal.

FIG. 4 is a perspective view showing an example of use of a reflective polarizing screen according to the present invention.

FIG. 5 is a perspective view showing an example of use of the transmissive polarizing screen according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Polarizing fiber, 2 ... Transparent fiber, 3 ... Transparent resin, 4 ... Visible light reflective layer, 5 ... Adhesive layer, 6 ... Backing sheet, 7 ... Winding jig, 8 ... Reflective polarizing screen, 9 ... Transmissive type Polarizing screen, 10 ... Liquid crystal image projector, 11 ... Rear projection type liquid crystal image display device, 12 ... Linearly polarized image light having horizontal electric field vibrating surface, 13 ... Straight line having non-polarizing or vertical electric field vibrating surface Polarized light, 14… horizontal viewing angle, 15… vertical (vertical)
Viewing angle

Claims (1)

[Claims] 1. A polarizing woven fabric in which a polarizing fiber and a non-polarizing fiber are woven as warps and wefts or wefts and warps, respectively, and the longitudinal direction of the polarizing fibers in the polarizing woven fabric is substantially perpendicular to a horizontal plane. The polarizing screen is characterized in that the polarizing fibers are woven as warp satin or weft satin so that the surface where the polarizing fiber is mainly exposed faces the image viewer.