JPH10160914A - Lens film and surface light source device formed by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To widen a visual field angle by improving a luminance distribution. SOLUTION: The lens film 20 has a film-like base material 21, prism-like lens parts 22 formed on the light incident surface of this base material 21 and a light diffusion layer 23 which is disposed on the light exit surface of the base material 21 and has a diffusion effect. The surface light source device 10 has a light transmission member 11 which is formed to a wedge shape in the section of its one side, a linear light source 2 which is arranged on the end face on the thickness side of this light transmission member 11 and the lens film 20 which is disposed on the light exit surface side of the light transmission member 11 and is arranged with the ridge line direction of the prism-like lens parts 22 in parallel with the linear light source 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens film used for a back light source of a liquid crystal display device and the like, and a surface light source device using the same.

[0002]

2. Description of the Related Art FIG. 4A is a perspective view showing an example of a conventional surface light source device using a lens film, and FIG.
FIG. 9 is a diagram illustrating luminance characteristics of a surface light source device according to a conventional example.
The conventional surface light source device 10 has, for example, one wedge-shaped long side.
A light guide plate 21 having a size of 2.1 inches and a cold cathode tube (2φ, input 2) arranged on the short side (thick side) of the light guide plate 11
W), and a reflector 1 disposed on the outer periphery of the light source 12 to reflect and guide light toward the light guide plate 21
3 and disposed on the lower surface of the light guide plate 11 and on the light emitting surface side (upper surface)
A reflection film 14 for sequentially reflecting light to the light guide plate 11
And a lens film 30 disposed on the diffusion film 15 and the like.

A conventional lens film 30 is a PET film (A-4300 manufactured by Toyobo Co., Ltd., 125 μm thick).
m) or the like, and one side of the base material 31 is made of an ultraviolet curable resin (Z9002A, manufactured by Japan Synthetic Rubber Co., Ltd., refractive index n = 1.574), and its cross section is an isosceles triangle. The apex angle is 97 °, the lens pitch is 50 μm,
The lens height is 22 μm.
Lens part 3 formed by the manufacturing method according to
2 is provided.

[0004]

In the above-described conventional surface light source device, the lens film 30 is placed on the light guide plate 11 with the lens film 30 facing upward in order to make the light emitted from the light guide plate rise in the front direction. Therefore, as shown in FIG. 4B, the viewing angle [half-width at 68 ° (−33 ° to 35 °)] tends to be narrow. Further, the conventional surface light source device has many light guide plate units (11, 12, 13, 14), the light diffusion film 15, the lens film 30, and three members.

[0005] It is an object of the present invention to provide a lens sheet capable of improving the luminance distribution and widening the viewing angle, and a surface light source device using the same.

[0006]

In order to solve the above-mentioned problems, the invention of claim 1 is a film-like lens film, wherein a prism-like lens portion (2) formed on a light incident surface is provided.
2) and a light diffusion layer (23) having a diffusion effect provided on the light exit surface.

According to a second aspect of the present invention, in the lens film according to the first aspect, the light diffusion layer has a haze value of 70.
% Or more.

[0008] The invention of claim 3 is claim 1 or claim 2.
, The light diffusion layer has a total light transmittance of 70% or more, and more preferably 90% or more.

According to a fourth aspect of the present invention, there is provided a light guide member (11) having a wedge-shaped cross section on one side, a line light source (12) disposed on a thick end surface of the light guide member, and the light guide member. 2. The lens film (20) according to claim 1, wherein the lens film (20) is provided on a light exit surface side of the lens, and the ridge direction of the prism-shaped lens portion is arranged in parallel with the line light source.

[0010]

Embodiments of the present invention will be described below in more detail with reference to the drawings. FIG.
1A is a perspective view illustrating an embodiment of a surface light source device using a lens film according to the present invention, and FIG. 1B is a diagram illustrating luminance characteristics of the surface light source device according to the embodiment. The surface light source device 10 according to the present embodiment includes a light guide plate 11 and a light source 1.
2, the reflector 13, and the reflection film 14 are the same as those in the conventional example, and thus are denoted by the same reference numerals, and redundant description will be omitted.

The lens film 20 of this embodiment comprises a substrate 21 and a prism-shaped lens portion 22 formed on the light incident surface.
And a light diffusion layer 23 having a diffusion effect provided on the light exit surface.

The substrate 21 serves as a carrier of the film lens film 20 and is a film used for a backlight mechanism of an ordinary optical display or a liquid crystal display, and is at least one which is transparent to ionizing radiation. Can be used as appropriate, but a film made of a synthetic resin such as polyester such as polyethylene terephthalate, an acrylic resin such as polymethyl (meth) acrylate, polycarbonate, polyallylate, a fluorine-based resin, polyimide, or polypropylene is preferable.

As the prism-shaped lens portion 22, a known ultraviolet ray or electron beam curable resin, typically in a molecule,
(Meth) acryloyl group ((meth) acryloyl
The same shall apply hereinafter in the meaning of acryloyl or methacryloyl. ), A polymer having a polymerizable group such as a (meth) acryloyloxy group, an epoxy group, a thiol group and / or
Or a monomer. For example, polyfunctional prepolymers such as urethane (meth) acrylate, epoxy (meth) acrylate, and silicon (meth) acrylate; and polyfunctional monomers such as tritylolpropane tri (meth) acrylate and dipentaerythritol hexa (meth) acrylate And the like as a main component, and a highly crosslinked type is preferably used.
The resin is basically a solvent-free resin, but may be diluted with a solvent if necessary.

As a method of providing the light diffusion layer 23, FIG.
As shown in (1), a coating type (A), a base kneading type (B), an embossing type (C), a sand plast type (D), and an adhesive type (E) are preferably used.

The light diffusion layer of the coating type (A)
It is composed of a light-transmitting resin and a light-diffusing material. As the light-transmitting resin, for example, a polyester resin, an acrylic resin,
Polystyrene resin, polyvinyl chloride resin, polyvinyl chloride resin, polyethylene resin, polypropylene resin, polyurethane resin, polyamide resin, polyvinyl acetate resin, polyvinyl alcohol resin, epoxy resin, cellulose resin For example, an organosiloxane resin, a polyimide resin, a polysulfone resin, a polyarylate resin, or the like is used.

The light diffusing material is desirably beads or fillers containing acrylic, organic silicone, polystyrene, polyethylene, urea resin, silica, calcium carbonate, titanium oxide as a main component, or hollow beads thereof. Among them, acrylic beads are particularly desirable from the viewpoint of weather resistance and the like.
~ 50μ is desirable. Further, these light diffusing agents may be used alone or in combination of two or more.

The substrate kneading type (B) is a type in which a diffusing agent is kneaded inside the substrate. The emboss type (C) and the sand blast type (D) are obtained by roughening the surface of a substrate by a hot emboss method or a sand blast method. The adhesive type (E) is a type in which a single lens film and a single light diffusion film are bonded with an adhesive. As the pressure-sensitive adhesive, a rubber-based, acrylic, or silicone-based pressure-sensitive adhesive is used. The optical characteristics of the diffusion layer 23 are preferably such that the haze value (Hz) is 70% or more, and the total light transmittance (Tt) is 70% or more, and further preferably 90% or more.

Next, the shape of the prism lens section 22 will be described. In Table 1, the light output angle θ is the light output peak angle from the light guide plate [see FIG. 2A], and represents the optimal lens shape at that time.

[Table 1] Emission angle θ: 85 80 75 Lens shape: 47.5 (5 + 42.5) 50 (10 + 40) 52.5 (15 + 37.5)

FIG. 2 is a diagram showing an optical path in the prism-shaped lens according to the present embodiment in comparison with a conventional example. FIG.
(A) is an optical path in the prism-shaped lens portion 22 when light emitted from the light guide plate 11 rises in the front direction. FIG.
(B) shows the light diffusion layer 23 on the light exit surface of the lens film 20.
This is the optical path in the prismatic lens when there is. FIG.
(C) is an optical path in the prism-shaped lens part 32 when the conventional lens film 30 is used upward.

[0021]

The present invention will be further described below with reference to specific examples. As the substrate 21, a PET film (A-4300, manufactured by Toyobo Co., Ltd., thickness 125 μm) was used. The prism-shaped lens portion 22 is made of an ultraviolet curable resin (KZ9771 manufactured by Japan Synthetic Rubber Co., Ltd.), and the vertex angle of the trapezoid is 47.33 ° (32.5 ° and 12.5 ° with respect to the normal direction).
(4.83 °), a lens pitch of 40 μm and a lens height of 40 μm were formed by the manufacturing method described in Japanese Patent Application Laid-Open No. 5-169015.

The light diffusion layer 23 was formed on the upper surface of the substrate 21 at a coating amount of 9 g / m ² using the following diffusion agent (BL mat varnish (BAC79) manufactured by The Intec). The ink composition of this diffusing agent is as follows.

Light transmitting resin: 43 parts by weight of Byron 200 polyester resin manufactured by Toyobo Co., Ltd. Light diffusing agent: MBX-10 manufactured by Sekisui Plastics Co., Ltd. (PMMA beads having an average particle diameter of 10 μm, refractive index = 1. 49) 100 parts by weight Diluent solvent: methyl ethyl ketone 60 parts by weight Toluene 60 parts by weight

The light diffusion layer 23 of this embodiment has a haze value of 9
The light transmittance was 4.7% and the total light transmittance was 91.3%. Further, as shown in FIG. 1B, the surface light source device 10 of the present embodiment
Compared with the conventional example, the viewing angle [half-width is 82 ° (−43 °)
３９39 °)].

[0025]

As described above in detail, according to the present invention, since the light emitting surface of the lens film has a diffusion effect, a backlight having a wide viewing angle and high luminance can be realized.
This has the effect. Further, the light guide plate unit, the light diffusion film, the lens film and the number of members are three as in the conventional surface light source device. However, according to the present invention, the light guide plate unit, the lens film with the diffusion layer and the member number are two. Can be reduced to one.

[Brief description of the drawings]

FIG. 1A is a perspective view illustrating an embodiment of a surface light source device using a lens film of the present invention, and FIG. 1B is a diagram illustrating luminance characteristics of the surface light source device according to the embodiment. .

FIG. 2 is a diagram showing an optical path in a prism-shaped lens according to the present embodiment in comparison with a conventional example.

FIG. 3 is a view showing another embodiment of the lens film according to the present invention.

FIG. 4A is a perspective view illustrating an example of a conventional surface light source device using a lens film, and FIG. 4B is a diagram illustrating luminance characteristics of a surface light source device according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Surface light source device 11 Light guide plate 12 Light source 13 Reflector 14 Reflection film 20, 20A-20E Lens film 21 Base material 22 Prism-shaped lens part 23, 23A-23E Light diffusion layer

Claims (4)

[Claims] 1. A lens film having a prismatic lens portion formed on a light incident surface and a light diffusion layer having a diffusion effect provided on a light exit surface. 2. The lens film according to claim 1, wherein the light diffusion layer has a haze value of 70% or more. 3. The lens film according to claim 1, wherein the light diffusion layer has a total light transmittance of 70% or more. 4. A light guide member having a wedge-shaped cross section on one side, a line light source disposed on an end face on a thick side of the light guide member, and a prism-shaped member provided on a light exit surface side of the light guide member. A surface light source device using a lens film comprising: the lens film according to any one of claims 1 to 3, wherein a ridge direction of the lens unit is arranged in parallel with the line light source.