JP3047578B2 - Transmission screen - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission screen. In particular, the present invention relates to a transmission screen for a rear liquid crystal projector constituted by a TN liquid crystal panel.

[0002]

2. Description of the Related Art Transmissive screens used in TV projectors have the highest performance because they satisfy the performance requirements of screen brightness, uniformity, wide field of view in the horizontal direction, and low light loss in the vertical direction. In many cases, a sheet made up of two sheets, a Fresnel lens sheet and a lenticular lens sheet with black stripes, is used.

A configuration of a conventional transmission screen is shown in FIG. 3 and described (for example, see Japanese Patent Publication No. 3-52049). That is, two lens sheets, a Fresnel lens sheet 21 and a lenticular lens sheet 22 with black stripes, are combined. The Fresnel lens sheet 21 includes a Fresnel lens 21a on the incident side and a hairline processed surface 21b on the exit side. The hairline processing surface 21b is provided in place of the lenticular lens, and imparts a diffusion characteristic in the vertical direction of the projection screen. The hairline processed surface 21b is formed with a vertical diffusion characteristic (αv) (when the maximum luminance on the optical axis is 1, representing an angle range where the luminance is １ ／ or more) ± 4 ° or less. . On the other hand, the lenticular lens sheet 22
A lenticular lens 22a having a direction perpendicular to the processing direction of the fair line of the hairline processing surface as a longitudinal direction of the lenticular lens is formed on the incident side of the lenticular lens. The lenticular lens 22a has a normal horizontal diffusion characteristic (αH).
Are ± 35 ° to ± 50 ° to expand the left and right visual fields.
On the emission side, a black stripe 22b is provided at a non-light-collecting portion of the lenticular lens. Black stripe 2
2b has the effect of blocking stray light and reducing the reflection of external light on the emission side.

According to the above-mentioned structure, a transmissive screen is obtained in which the diffusion characteristics in the vertical direction as well as the horizontal direction are regulated. Furthermore, excellent image quality free from moiré and reflected images is obtained without any reduction in resolution in any direction.

[0005]

When this type of transmissive screen is used for a liquid crystal projector, it has the following problems. That is, the TN for the liquid crystal projector
Since the liquid crystal panel includes a thin film transistor and a driving wiring for each pixel, there is an area where the liquid crystal does not operate. A light shielding layer called a black matrix is provided to shield this region from light. The problem is that moire occurs on the projection screen due to the interaction between the black matrix and the black stripes of the transmission screen. The CRT type projector does not have the above-mentioned problem because the CRT has no black matrix, and is a problem newly generated in the liquid crystal projector.

As a countermeasure against the above-mentioned problem, there is a method of making the pitch of the black stripes fine. In this case, since the lenticular lens and the black stripe are molded, fine processing is difficult. For example, when the number of horizontal pixels is 640 on a 40-inch screen, a black matrix is projected on a screen at a pitch of 1.3 mm. In order to prevent moire with black stripes, 0.2 to
A black stripe and a lenticular lens with a fine pitch of 0.3 mm or less are required. Therefore, the processing cost becomes expensive. In addition, because of the fine pitch, the projection screen loses its gloss and has a problem that the screen becomes poorly sharpened. The present invention has solved the above problem by focusing on the fact that a TN-type liquid crystal projector is composed of only a polarization component. SUMMARY OF THE INVENTION An object of the present invention is to provide a transmissive screen which is inexpensive in processing cost and can obtain a glossy and well-projected image.

[0007]

In order to achieve the above-mentioned object, a transmission screen according to the present invention comprises a combination of two lens sheets, a Fresnel lens sheet and a lenticular lens sheet. A Fresnel lens is formed only on one surface, and a first lenticular lens or a directional hairline processing surface is provided on a surface of the Fresnel lens sheet opposite to the Fresnel lens forming surface, and the lenticular lens sheet is Forming a second lenticular lens having a longitudinal direction in a direction orthogonal to a longitudinal direction of the first lenticular lens on a surface opposing the Fresnel lens sheet, and a surface opposite to the second lenticular lens is 1 / A four-wavelength plate and a polarizing plate are sequentially laminated.

[0008]

The operation of this configuration is as follows. That is, in the liquid crystal projector using the TN liquid crystal, the projection light is usually composed of linearly polarized light due to the characteristics of the liquid crystal. Therefore, the projection light of the liquid crystal projector is converted into right circularly polarized light or left circularly polarized light by using a quarter wavelength plate in the projection optical system. For example, a case where the projection light is converted into left circularly polarized light will be described. The projection light is condensed by the Fresnel lens, and is diffused by ± 5 ° at the first lenticular lens or the hairline processing surface.

Next, the light is diffused in the horizontal and vertical directions by the second lenticular lens and the light diffusing agent. This transmitted light is again converted into linearly polarized light by passing through a quarter-wave plate, and passes through a polarizing plate having a polarization axis that matches the polarization axis of the linearly polarized light. Therefore, the projection light can display the screen only by the loss relating to the transmittance of the polarizing plate.

On the other hand, since external light is natural light, it is composed of right-handed circularly polarized light and left-handed circularly polarized light. Subsequently, for example, if it is set to be converted into left-handed circularly polarized light by a quarter-wave plate, the external light reflected by the diffusing agent changes to right-handed circularly polarized light, passes through the quarter-wave plate again, and is absorbed by the polarizing plate. Since the linearly polarized light having the polarization direction in the axial direction is converted, the external light is completely absorbed. Therefore, the projected image is hardly affected by external light.

With the above structure, since there is no black stripe, there is no generation of moire due to the interaction with the black matrix of the liquid crystal panel. Further, since the surface is formed of a polarizing plate, the projected image is glossy and sharp.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 is a perspective view showing the structure of the present invention. In the Fresnel lens sheet 11, a circular Fresnel lens 11 is formed on the incident side of the projection light, and a first lenticular lens 11b is formed on the entire exit side in the horizontal direction. The lenticular sheet 12 is perpendicular to the entire surface on the incident side, that is, the Fresnel lens sheet 11
The second lenticular lens 12a is formed in the direction perpendicular to the longitudinal direction of the first lenticular lens, and the quarter-wave plate 12b and the polarizing plate 12c are sequentially laminated on the emission side. The lenticular lens sheet 12 has a light diffusing agent 12d provided inside and is visualized (FIG. 2). The light diffusing agent 12d adjusts the amount of the diffusing agent and the surface light diffusing layer so as to control the vertical diffusion characteristic (αV) of the lenticular lens sheet 12 to ± 5 ° to ± 10 °. In order to provide the lenticular lens sheet 12 with a vertical diffusion characteristic, as shown in FIG.
2d may be provided, or these may be used in combination.

With the above arrangement, the projection light from the liquid crystal panel was converted into circularly polarized light by a quarter-wave plate in advance and evaluated. As a result, no moire occurred and there was no black stripe, so the projected image was transparent. Moreover, a sharp image could be obtained. It was confirmed that the display was hardly affected by external light even in black display. In this embodiment, a lenticular lens is used for the Fresnel lens sheet, but the same effect can be obtained by using a hairline processed surface.

Further, the image quality can be further improved by applying an antireflection coating to the surface of the polarizing plate. Even if a hard coating is applied for surface protection, there is no problem in the effect according to the present invention.

[0016]

When the transmissive screen according to the present invention is used in a liquid crystal projector, there is no moiré, there is no translucency, and there is almost no influence of external light, so that the liquid crystal projector is excellent in sharpness and sharpness. This has the effect that an improved image quality can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view of a transmission screen according to an embodiment of the present invention.

FIG. 2 is a sectional view of a lenticular lens sheet according to one embodiment of the present invention.

FIG. 3 is a perspective view showing a conventional transmission screen.

[Explanation of symbols]

 Reference Signs List 11 Fresnel lens sheet 11a Circular Fresnel lens 11b First Fresnel lens 12 Lenticular lens sheet 12a Second lenticular lens 12b Quarter wave plate 12c Polarizing plate 12d Light diffusion layer 21 Fresnel lens sheet 21a Fresnel lens 21b Hairline processed surface 22 Lenticular Lens sheet 22a Lenticular lens 22b Light shielding layer (black stripe)

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-78840 (JP, A) JP-A-58-5030 (JP, U) JP-A-3-5147 (JP, U) (58) Investigation Field (Int.Cl. ⁷ , DB name) G03B 21/62

Claims (2)

(57) [Claims] 1. A Fresnel lens sheet comprising two lens sheets, a Fresnel lens sheet and a lenticular lens sheet, wherein the Fresnel lens sheet has a Fresnel lens formed on only one surface, and the Fresnel lens forming surface of the Fresnel lens sheet. A first lenticular lens or a directional hairline processing surface is provided on a surface opposite to the first surface, and the lenticular lens sheet has a direction perpendicular to a longitudinal direction of the first lenticular lens on a surface opposed to the Fresnel lens sheet. A second lenticular lens having a longitudinal direction, and a quarter-wave plate and a polarizing plate are sequentially laminated on a surface opposite to the second lenticular lens. 2. The transmission screen according to claim 1, wherein the lenticular lens sheet has a light diffusing agent therein.