JPH09160131A - Reflection type polarizing screen - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a distinct video without blotting or blurring on a screen used for the projection of a liquid crystal projector. SOLUTION: This screen 4 is provided with a reflector 1, a polarizing element 2 laminated on the reflector 1, and a light diffusing layer 3 laminated on the element 2. In such a case, the total thickness (d) from the reflection surface 1a of the reflector 1 to the outermost layer of the light diffusing layer 3 is set to a value satisfying relation expressed by an expression d(μm)<150/tanθ (provided that θ is a half-power angle to the front reflection intensity of a diffused reflection angle on the reflection surface).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflective polarizing screen used for projection of a projection television or the like using a liquid crystal display device.

[0002]

2. Description of the Related Art In the case of projecting various images such as a television image, a slide image, and a movie image by a projector using a liquid crystal display device, or an overhead projector (OH) using the liquid crystal display device.
As a screen used for projecting an OHP image by P), there is a reflective screen. This reflection type screen is one in which the projection image emitted from the liquid crystal display device is reflected on the screen surface so that the projected image can be seen from the projection side. While the projected image that is emitted is linearly polarized, the ambient light that impairs the clarity of the projected image is usually non-polarized, and one of the screen components has a polarizing function. In the past, it has been proposed to be able to view an image in a bright room.

As an example thereof, Japanese Patent Laid-Open No. 62-26698.
No. 0 and Japanese Patent Application Laid-Open No. 63-267073 disclose a non-polarizing property by providing a polarizing plate on the surface of a screen that transmits linearly polarized light that forms a projected image and absorbs a polarized component orthogonal to this. A polarizing screen that reduces the amount of reflection of ambient light is disclosed. However,
In the screens described in these publications, for example, in order to protect a polarizer obtained by adsorbing iodine on uniaxially stretched PVA (polyvinyl alcohol), both sides of a polarizing plate are sandwiched by TAC (triacetyl cellulose) films. Since a laminated structure consisting of the above is used, if only the polarizing plate is attached to the front surface of the screen as described above, specular reflection occurs on the surface of the TAC, which is the outermost surface, and glare and the projection lens projection image of the projector are reflected. Easy to get crowded.

Therefore, in order to prevent such a problem,
For example, JP-A-4-301830 and JP-A-5-72
In the polarizing screen described in Japanese Patent No. 630 or the like, a light diffusion layer such as a diffusion sheet or a matte sheet is provided on the front surface of a polarizing plate. According to this, since the light reflected on the screen surface is transmitted through the polarizing plate and then diffused by the light diffusing layer, it is possible to prevent glare and reflection of the projection lens.

[0005]

However, in the conventional polarizing screen provided with the light diffusing layer as described above, glare and reflection of the projection lens are prevented, but the presence of the light diffusing layer causes a projected image to appear. Bleeding and blurring occur, resulting in a problem that a clear image cannot be obtained.

In addition to these points, the conventional polarizing screen has the following problems. In other words, in recent years, liquid crystal projectors have become higher-definition, and products having more than 900,000 pixels are being provided. However, when an image having more than 900,000 pixels is projected on a 100-inch size screen, for example, RGB three primary colors are displayed. The size of each pixel including a set of dots is about 1 mm in diameter on the screen. However, in the conventional polarizing screen, the relationship between the visual characteristics of the reflecting surface and the thickness of the polarizing plate and the light diffusion layer was not taken into consideration, and therefore, when the above-mentioned fine image was projected on the screen, There is a problem that the quality of the image is deteriorated due to blurring of contours and the like. This will be specifically described in the conventional reflective polarizing screen 14 having the cross-sectional structure shown in FIG.

In the figure, the light l projected from the liquid crystal projector is transmitted through the light diffusing layer 13 and the polarizing element 12 in the polarizing screen 14 and then diffused and reflected at the point b of the reflecting plate 11 to be viewed. Think about when you reach. In this case, for example, the light reflected in the direction of bl in the figure is diffused at the point a ′ on the surface of the light diffusion layer 13, and part of it reaches the point e. On the other hand, the light reflected in the direction of be diffuses at the point b ′ on the surface, and part of the light reaches the point e. Therefore, from the point e, one image is viewed at many points such as a'point and b'point (in other words, many directions such as aa 'direction, bb' direction), and the reflector plate. Due to the relationship between the visual characteristics of No. 11 and the total thickness d from the reflection surface to the outermost layer, blurring or blurring occurs in the image, and the image quality is deteriorated.

The present invention addresses the above-mentioned problems in the prior art, and is a screen used for projection of a projector (hereinafter referred to as a liquid crystal projector) using a liquid crystal display device, which is clear without blurring or blurring. It is an object of the present invention to provide a reflective polarizing screen that can obtain various images.

[0009]

In order to achieve the above object, the present invention is, as shown in FIG. 1, a reflector 1, a polarizing element 2 laminated on the reflector 1, and a polarizing element. In the reflective polarizing screen 4 having the light diffusing layer 3 laminated on top of the light diffusing layer 3, the total thickness d from the reflecting surface 1a of the reflecting plate 1 to the outermost layer of the light diffusing layer 3 is expressed by the following equation (1). It is characterized in that it is set to a value that satisfies it.

D (μm) <150 / tan θ (1) Here, d represents the total thickness from the reflecting surface 1 to the outermost layer surface of the light diffusing layer 3, and therefore on the reflecting plate 1. When a pressure-sensitive adhesive or an adhesive is provided between the respective layers when the polarizing element 2 and the light diffusion layer 3 are laminated on the above, the thickness thereof is also included.

Further, as shown in FIG. 2, for example, θ is 1 with respect to the reflection intensity to the front (vertical incidence direction) when the light vertically incident on the reflecting surface is diffusely reflected with a certain angular distribution. The angle (half-value angle) at which the intensity becomes / 2 is represented. Therefore, when θ is large, it means that the angular range of diffuse reflection is wide, and when θ is small, it means that the angular range of diffuse reflection is narrow.

The components of the present invention will be described in more detail below. Regarding θ and d By determining the above θ and d so as to satisfy the relationship of the equation (1), a clear image without bleeding or blurring can be obtained as will be described later. The half-value angle θ can be appropriately set finally from the required viewing angle of the screen, and is generally 2 to 60 °, preferably 5 to 45 °. θ is 5 °
In the following cases, the obtained screen has a too narrow viewing angle and is not suitable for practical use. When it is 45 ° or more, the viewing angle becomes too wide and the brightness in the front direction is lowered, which is not preferable.

Therefore, from the equation (1), d is, for example, θ
A screen for obtaining a clear image can be designed by setting it to 150 μm or less when = 45 ° and 850 μm or less when θ = 10 °. The lower limit of d is not specified, but it can be applied to a polarizing element or a light diffusing layer laminated on the reflecting surface, and an adhesive layer or an adhesive layer provided as necessary. This is because it is naturally determined by the minimum thickness.

Regarding Reflective Plate In the present invention, a reflective plate having diffuse reflectivity is used. As such a diffuse reflective material, for example, an aluminum plate (or foil) having a hairline-processed surface, in other words, a large number of fine linear grooves formed, or a surface-roughening treatment is used. Aluminum plate (or foil), paint coated with aluminum powder or pearl pigment, etc. coated on a plastic sheet such as a polyester film, or aluminum deposited on a plastic sheet roughened by embossing etc. The ones that have been made are listed.

Of these, particularly when an aluminum plate having a hairline finish is used, light can be diffusely reflected in a horizontal direction orthogonal to the hairline and narrowly in a vertical direction parallel to the hairline, in other words. Since anisotropy can be imparted to the diffuse reflection direction, the projected image can be selectively reflected within the range required for the screen, and as a result, the reflection brightness can be increased, which is preferable.

About Polarizing Element The polarizing element laminated on the reflecting surface is a uniaxially stretched PV.
A polarizing element obtained by adsorbing iodine to A, or a polarizing plate provided with a protective layer made of a TAC film on both surfaces of such a polarizing element, or as described in JP-A-3-9303, for example. Any polarizing plate having a polarizing function can be used, such as a polarizing plate formed by rubbing a plastic film such as a TAC film in an arbitrary direction and then subjecting it to corona treatment and then coating a dye thereon.

Light Diffusing Layer The light diffusing layer laminated on the polarizing element is, for example, a film whose surface is matt-treated and whose material is TAC,
A transparent thermoplastic resin such as polyvinyl chloride, polyethylene, polypropylene, or polyethylene terephthalate is used. <Operation> For example, in FIG. 3, the distance between a ′ and b ′ is d × tan.
Therefore, the larger the value of d × tan θ, the more the image looks blurred. However, according to the present invention, the total thickness d from the reflecting surface to the outermost layer of the light diffusing layer is d.
Since it is set to satisfy <150 / tan θ (equation (1)), the distance between a ′ and b ′ (d × tan
θ) is always less than 150 μm. Therefore, strictly speaking, even if one image is seen at different points a ′ and b ′, it is recognized by the naked eye as a clear image without blurring or blurring.

[0018]

Embodiments of the present invention will be described below. First, the following reflectors having different half-value angles θ of the diffuse reflection intensity were prepared as the reflectors constituting the reflective polarizing screen having the sectional structure shown in FIG.

A: Extremely rough surface treated aluminum foil (manufactured by Toyo Aluminum Co., Ltd., θ = 10 °) B: Hairline processed aluminum plate (θ = 30 °) C: Shot blasted aluminum plate (θ = 45)
°) Further, the following polarizing elements having different thicknesses were prepared.

D: Polarizer (25 μm thick) obtained by adsorbing iodine on uniaxially stretched PVA E: Polarizing plate of iodine adsorption type (trade name: NPF-F1
205, manufactured by Nitto Denko Corporation, thickness 120 μm) Further, the following light-diffusing layers having different thicknesses were prepared.

F: Matt-treated polypropylene film (manufactured by Toyobo Co., Ltd., thickness: 25 μm) G: Matt-treated polyvinyl chloride sheet (Achilles Co., Ltd., thickness: 80 μm) H: Matt-treated polyvinyl chloride Sheet (manufactured by Achilles Co., Ltd., thickness: 200 μm) When laminating each layer, a pressure-sensitive adhesive layer (thickness: 25 μm, made of an acrylic pressure-sensitive adhesive between the layers so that they are bonded in a predetermined state ) Was intervened.

A reflective polarizing screen as shown below was produced by combining the above materials. (Example 1) A reflective polarizing screen of Example 1 was obtained by laminating a polarizing element E and a light diffusing layer F on the reflecting surface of a reflecting plate B in this order with an adhesive layer in between. . This screen has a total thickness d from the reflecting surface to the outermost surface of the light diffusing layer of 195 μm, and has the above formula (1).
Was satisfied.

When an image was projected on this screen by using a liquid crystal projector, a clear image without bleeding or blurring was obtained. (Examples 2 to 5) Similarly, screens were produced by combining the above materials so as to satisfy the formula (1) and evaluated. Table 1 shows combinations and evaluation results in this case. The results of Example 1 are also shown in the table for easy comparison. (Comparative Examples 1 to 4) Furthermore, as comparative examples, screens were produced in combinations that did not satisfy the formula (1), and the obtained screens were evaluated. The combinations and the evaluation results are shown in Table 1.

[0024]

[Table 1]

As shown in Table 1, for Examples 2 to 5 satisfying the formula (1), clear images could be viewed in all cases, as in Example 1. On the other hand, in each of Comparative Examples 1 to 4 in which the combination that does not satisfy the expression (1), the contour of the image was blurred, and only a low quality image was obtained.

[0026]

As described above, according to the present invention, in the reflection type polarizing screen in which the polarizing element and the light diffusing layer are sequentially laminated on the reflecting surface having the diffuse reflectivity, the light diffusing is performed from the reflecting surface. Since the total thickness d of the layers up to the outermost layer satisfies the following expression d (μm) <150 / tan θ (where θ is the half-value angle of the diffuse reflection angle on the reflection surface with respect to the front reflection intensity), blurring and blurring It is possible to obtain a clear image with no difference.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view used for explaining a reflective polarizing screen according to the present invention and schematically showing an example of a cross-sectional structure of the screen.

FIG. 2 is a graph used for explaining a half value angle in diffuse reflection.

FIG. 3 is an explanatory diagram used to explain problems in a conventional reflective polarizing screen.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Reflector 1a ... Reflecting surface 2 ... Polarizing element 3 ... Light diffusing layer 3a ... Outermost layer surface of light diffusing layer 4 ... Reflecting polarizing screen

Claims (2)

[Claims] 1. A reflection type polarizing screen comprising a polarizing element and a light diffusing layer sequentially laminated on a reflecting surface having a diffusive reflectivity, and a total thickness d from the reflecting surface to the outermost layer of the light diffusing layer is as follows. A reflective polarizing screen represented by the formula (1). d (μm) <150 / tan θ (1) (where θ is the half-value angle of the diffuse reflection angle on the reflection surface with respect to the front reflection intensity) 2. The reflection type polarizing screen according to claim 1, wherein the reflecting surface is made of hairlined aluminum.