JP2006313215A - Lens sheet for wide visual field angle liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens sheet with which a liquid crystal display can be provided, which is suitable for a face-shaped light source, has high luminance over a visual field angle ±35° and is uniform, like the liquid crystal display using a triangular prism lens sheet. <P>SOLUTION: A large number of projections of about a triangular pyramid shape are arranged on one surface of a base material consisting of a transparent polymer material and the triangular pyramids are arranged at a light transmission plate side of the base material. By arranging the lens sheet in a prescribed direction, the face-shaped light source which has improved luminance and can improve uniformity of luminance in a necessary and required angle range can be obtained. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a lens sheet that provides a uniform liquid crystal display device with a high luminance over a viewing angle of ± 35 degrees, which is suitable for a planar light source, such as an in-vehicle liquid crystal display device.

  As a conventional planar light source (for example, a backlight of a liquid crystal display device), as shown in FIG. 1, light from the light source is transmitted through a light guide plate and reflected by a reflection sheet, and an upward triangular prism is formed through a diffusion plate. There is a sidelight system in which light is collected by being incident on a prism lens. In addition, there is a direct type system in which light from a light source as shown in FIG. 2 is directly incident on a triangular prism lens through a diffusion plate. In either case, a diffusion plate may be disposed so as to make the light intensity (luminance) uniform within a desired light emission radiation angle.

Particularly in the case of a side light type surface light source, most of the light emitted from the light guide plate is emitted in a direction of about 60 degrees from the normal direction. The same applies to the case where light enters the lens from the light guide plate via the diffusion plate.

Therefore, in recent years, a concave or convex prism lens having a substantially triangular pyramid shape or a substantially quadrangular pyramid shape on at least one surface on a plastic film has been proposed.
JP 2005-44642 A

  However, even when these methods are used, there is a problem in that the luminance difference is large when the luminances of normal angles of −35 degrees to 35 degrees are compared as shown in FIG.

  The lens sheet for a wide viewing angle liquid crystal display device according to the present invention provides a planar light source that increases the luminance of the surface light source and has a uniform luminance distribution in a desired angle range (approximately ± 35 degrees). To do.

By disposing the lens sheet of the present invention in a predetermined direction, it is possible to obtain a planar light source that can increase the luminance of the planar light source and improve the uniformity of the luminance in a desired angle range.

  The present invention has been made to solve the above problems, and the inventions described in claim 1, claim 2, claim 3, claim 4 and claim 5 are made of a polymer material having transparency. A large number of substantially triangular pyramid-shaped protrusions are arranged on one side of the base material, and the triangular pyramids are arranged on the light guide plate side in the base material.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not limited to this Example.

(Example 1)
A highly transparent resin (acrylic resin) is filled into a prism plate, cured onto a polyester terephthalate (PET) 100 μm, adhered and transferred, and cured by irradiating with ultraviolet rays, to form a prismatic right triangle (vertical angle 90 degrees, pitch 150 μm). Lens sheet FIGS. 4 and 5 were prepared.

With respect to the sample prepared in the example, the luminance in the normal direction was measured using a luminance meter (manufactured by BM-7 Topcon) with the configuration shown in FIG. 6 (FIGS. 3 and 7). Incidentally, BEF2 (manufactured by Sumitomo 3M (vertical angle 90 degrees)) was used on the lens sheet in such a manner that the direction of the triangular pyramid was parallel to the lamp.

It is the figure which modeled the sidelight type backlight It is the figure which modeled the direct type backlight It is the figure which measured the normal angle brightness | luminance of the backlight of a conventional structure, and an Example. Enlarged view of lens sheet for wide viewing angle liquid crystal display (Example) Overall view of lens sheet for wide viewing angle LCD (Example) It is the figure which imitated the structure using the lens sheet for wide viewing angle liquid crystal display devices of an Example. It is the figure which measured the brightness | luminance deviation by an angle on the basis of the normal angle of 0 degree | times for the backlight of the structure which used the backlight sheet | seat of the conventional structure, and the lens sheet for wide viewing angle liquid crystal display devices which are an Example.

Explanation of symbols

1, 6, 11 ... Lamp 2, 13 ... Light guide plate 3, 7, 12 ... Reflector plate 4, 9 ... Diffusion A
5, 10, 15 ... lens sheet 8 ... diffusion B
14 ... Lens sheet for wide viewing angle liquid crystal display device

Claims (5)

A lens sheet disposed between a light guide plate and an upward prism lens having an apex angle of 90 degrees in a backlight unit used in a liquid crystal display device having at least a light guide plate and an upward prism lens having an apex angle of 90 degrees.   A sheet having a number of substantially triangular pyramid-shaped protrusions on one surface.   The substantially triangular pyramid provided is disposed on the light guide plate side in the base material. A sheet characterized in that the apex angle of the provided substantially triangular pyramid is 85 to 95 degrees.   The surface light source provided is a sheet having a difference between a maximum value and a minimum value of less than 10% at a normal angle of −35 degrees to 35 degrees.

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