JPH10197702A - Lens sheet and back light - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the luminance as a back light without using plural lens sheets by incorporating a fluorescent brightening agent into the lens sheet. SOLUTION: This lens sheet is constituted by arranging a light source 2, such as fluorescent lamp, on one end of a light transmission body 3 and placing the lens sheet 1 contg. the fluorescent brightening agent on the light transmission body 3. A diffusion sheet 4 is usually placed on the exit surface of the light transmission body 3 and a reflection layer is formed by a reflection film, etc., on the surface on the side opposite to the exit surface. The UV components of wavelengths 330 to 380nm which are released from the light source 2, i.e., a cold cathode tube, but are invisible and are, therefore, not effectively utilized heretofore for improving luminance are made into the fluorescence of the visible light components of wavelengths 400 to 450nm by the fluorescent brightening agent incorporated into the lens sheet 1 in such a manner, by which the luminance of the back light is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight used for a liquid crystal display device and the like, and a lens sheet used for improving the front luminance thereof. The present invention relates to a lens sheet that can be improved.

[0002]

2. Description of the Related Art In recent years, power consumption of portable notebook personal computers equipped with a color liquid crystal display device, and products such as a portable liquid crystal TV using a color liquid crystal panel or a video integrated liquid crystal TV, which is driven by a battery, has been reduced. Large liquid crystal display devices are an obstacle to extending battery drive time. Above all, the percentage of power consumption of the backlight used for this is large, and keeping it low is an important goal in extending battery drive time and increasing the practical value of the above products.

At this time, if the brightness of the backlight is reduced to suppress the power consumption, the screen becomes dark, which is not preferable. In order to suppress the power consumption without sacrificing the luminance, a lens sheet 1 having a lens array such as a prism array on one side as shown in FIG. A method of improving the luminance of the backlight by mounting the liquid crystal unit 5 between the diffusion sheet 4 and the liquid crystal unit 5 provided on the light emitting surface of the light emitting device 3 is adopted.

As shown in FIG. 1, such a lens sheet 1 may be used with one sheet placed on the light guide 3 as described in JP-A-7-218911. ,
There is also employed a method in which two lens sheets are placed on top of each other to further improve luminance.

[0005]

However, in such a system in which two lens sheets are stacked, the front luminance can be improved, but assembling work becomes complicated with an increase in the number of parts, and a backlight is not provided. There is a problem that it hinders downsizing and a problem that the cost is increased by using a plurality of relatively expensive lens sheets. Further, when two lens sheets are superimposed, an optical pattern such as Newton's ring or moiré often occurs, and there is a problem that the liquid crystal display itself appears to have a defect. doing.

[0006] For these reasons, there is a demand for improving the luminance of a backlight using a single lens sheet. Accordingly, it is an object of the present invention to provide a backlight having sufficiently high luminance even in a system using one lens sheet, and a lens sheet used for the backlight.

[0007]

That is, a lens sheet according to the present invention is a lens sheet in which a large number of lens rows are arranged in parallel on at least one surface, and the lens sheet contains a fluorescent whitening agent. It is characterized by having. Further, the backlight of the present invention, a light source, at least one side end surface facing the light source is a light incident surface,
A light guide whose one light exit surface is substantially perpendicular to the light incident surface, and a large number of lens arrays are arranged in parallel on at least one of the light guides provided on the light exit surface side. A backlight on which the lens sheet is mounted, wherein the lens sheet contains a fluorescent whitening agent.

As described above, according to the present invention, the wavelength 330 which has not been effectively used in the past to improve the luminance.
The luminance of the backlight can be improved by converting the ultraviolet light component having a wavelength of about 380 nm into fluorescent light of a visible light component having a wavelength of about 400 to 450 nm using a fluorescent whitening agent contained in the lens sheet.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A lens sheet 1 according to the present invention is shown in FIG.
As shown in the figure, a large number of lens rows 7 are provided on at least one surface.
Are arranged in parallel in a sheet shape, and the shape of the lens array 7 formed on the surface of the lens sheet 1 may be various shapes depending on the purpose. For example, a prism shape, Lenticular lens shape, corrugated shape, and the like.

Above all, a prism shape is particularly preferable in view of the effect of improving the front luminance as a backlight. Further, the thickness of the lens sheet 1 is about 0.1 to 3 mm,
Is preferably about 30 μm to 0.5 mm. Further, when a prism sheet is used as the lens sheet 1, the prism apex angle is appropriately selected at an angle capable of sufficiently improving the front luminance according to the directional characteristics of the light emitted from the light guide. It is preferable that the angle be in the range of 50 to 150 °.

The present invention is characterized in that the brightness as a backlight is improved by including a fluorescent whitening agent in the lens sheet 1. That is, since the fluorescent whitening agent contained in the lens sheet 1 cannot be seen even though it is emitted from the cold-cathode tube as the light source, it has a wavelength of 330 to 380 nm which has not been effectively used for improving the brightness. The brightness of the backlight is improved by using the ultraviolet component as fluorescence of a visible light component having a wavelength of about 400 to 450 nm.

The fluorescent whitening agent used is not particularly limited. For example, Hakko manufactured by Showa Chemical Co., Ltd.
l BX, Kayacoll BB, Ka from Nippon Kayaku
yacoll BB cone, Kayall B
Fluorescent brightener using 4,4′-triazinylaminostilbene-2,2′-disulfonic acid derivative such as Icon, Whitex 4BM manufactured by Sumitomo Chemical Co., Ltd.,
Mikephor BE cone manufactured by Mitsui Chemicals, Inc.
Mikephor RFA cone, Mikepho
stilbene-based fluorescent whitening agents such as r TB cone, Sumitomo Chemical's Whitex ERN, Ciba-Geigy's Uvitex ERN cone, etc. oxazole-based fluorescent whitening agents; Sand's Leucopur EGM; Coumarin-based fluorescent whitening agents, pyrazoline-based fluorescent whitening agents such as Kayacoll C manufactured by Nippon Soda, Whitex NK manufactured by Sumitomo Chemical Co., Ltd.
R, Whitex SNP, Nippon Kayaku Kayaph
or an OLN or other bisoxazole-based brightener, an imidazone-based brightener, an imidazole-based brightener, a triazole-based brightener, a naphthalimide-based brightener, and the like. These optical brighteners are added in the lens sheet
% By weight or less, more preferably 0.0001 to 0.1% by weight,
More preferably, it is in the range of 0.001 to 0.05% by weight. This is because if the content of the fluorescent whitening agent is extremely small, a sufficient brightness improving effect tends not to be exerted. Conversely, if the content exceeds 1% by weight, the shaping of the lens sheet is inhibited. This is because the resin is fluorescent, and particularly when an ultraviolet curable resin is used, the resin does not tend to be sufficiently cured.

In the present invention, when a lens portion is formed on the surface of a transparent substrate as a lens sheet 1 as described later, the fluorescent whitening agent is contained in either the transparent substrate or the lens portion. May be.

The lens sheet 1 of the present invention is preferably manufactured by using a material having a high visible light transmittance and a relatively high refractive index. For example, an acrylic resin, a polycarbonate resin, a vinyl chloride resin, Energy ray-curable resins and the like. Among them, an active energy ray-curable resin is preferred from the viewpoints of scratch resistance, handleability, productivity and the like of the lens sheet. In the present invention, additives such as an antioxidant, an ultraviolet absorber, a yellowing inhibitor, a bluing agent, a pigment, and a diffusing agent may be added to the lens sheet as needed.

As a method for producing the lens sheet 1 of the present invention, a usual molding method such as extrusion molding, injection molding and the like can be used. When manufacturing the lens sheet 1 using an active energy ray-curable resin, the lens portion 7 is formed on a transparent substrate 6 such as a transparent film or a sheet using the active energy ray-curable resin. First, an active energy ray-curable resin liquid is injected into a lens mold having a predetermined lens pattern formed thereon, and a transparent substrate is overlaid. Next, an active energy ray such as an ultraviolet ray or an electron beam is irradiated through the transparent base material, and the active energy ray-curable resin liquid is polymerized and cured to form a lens portion, and then separated from the lens mold to obtain the lens sheet 1.

The transparent substrate 6 may be a flexible glass plate through which active energy rays pass, but is generally made of a transparent synthetic resin such as an acrylic resin, a polycarbonate resin, a vinyl chloride resin, a polymethacrylimide resin, and a polyethylene terephthalate resin. Resin film can be used. These materials are desirably smooth, but it is necessary that a coating layer for improving adhesion to an active energy ray-curable resin forming a prism shape is disposed on one or both surfaces.

As the active energy ray-curable resin constituting the lens portion 7, a mixture mainly composed of the following components (A), (B) and (C) is polymerized and cured by irradiation with active energy rays. The component (A) is selected from at least one of a monomer and an oligomer capable of radical polymerization, and determines the optical performance of the manufactured lens sheet 1. It is preferable to select as appropriate. As the component (A), a monomer or an oligomer capable of radical polymerization is used alone or in combination of two or more. Usually, two or more are preferably used, and the mechanical strength required for the lens sheet 1 is preferable. , Impact resistance, heat resistance, surface hardness, chemical resistance, and dyeability. Further, by using a compound having an acryloyl group or a methacryloyl group as a radical polymerizable functional group in an amount of 60 parts by weight or more of the composition,
The irradiation with active energy rays causes partial copolymerization and instantaneous inflow, so that optical distortion due to convection in the molded lens portion is reduced, which is preferable.

Specific examples of the component (A) include ester-type (meth) acrylic compounds obtained by a condensation reaction of aliphatic, alicyclic, or aromatic mono- or polyalcohols with acrylic acid or methacrylic acid. (A-1), a urethane-forming reaction of an isocyanate compound having two or more isocyanate groups in the molecule with a (meth) acrylate containing a hydroxyl group or a thiol group. Urethane poly (meth) acrylate (a-2) or a compound having at least two epoxy groups in the molecule and acrylic acid or methacrylic acid, which is obtained by a glycidyl group ring-opening reaction. ) Acrylates (a-3), saturated or unsaturated polycarboxylic acids, polyhydric alcohols, and (meth)
(Meth) acryloyl-functional monomers and oligomers such as polyester (meth) acrylate (a-4) obtained by a condensation reaction with acrylic acid, styrene, chlorostyrene, bromostyrene, dibromostyrene, divinylbenzene, Vinyl compounds (a-4), diethylene glycol bisallyl carbonate, diallyl phthalate, etc.
(Meth) allyl compounds such as diallyl biphenylate (a
-5). These monomers may be used alone or as a mixture of two or more.

Specific preferred examples of the component (a-1) include methyl (meth) acrylate, butyl (meth) acrylate, hydroxyethyl (meth) acrylate,
Aliphatic mono (meth) acrylates such as hydroxypropyl (meth) acrylate, cyclohexyl (meth) acrylate, dicyclopentanyl (meth) acrylate;
Dicyclopentenyl (meth) acrylate, isobornyl (meth) acrylate, bornyl (meth) acrylate
Alicyclic mono (meth) acrylate such as phenyl, (meth) acrylate, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, phenoxy-2
-Methylethyl (meth) acrylate, 3-phenoxy-2-hydroxypropyl (meth) acrylate, 2-
Phenylphenyl (meth) acrylate, 2-phenylphenoxyethyl (meth) acrylate, 4-phenylphenoxyethyl (meth) acrylate, 2-phenylphenyl-2-methyloxyethyl (meth) acrylate, 2-naphthyl (meth) acrylate, 2-bromophenyl (meth) acrylate, 4-bromophenyl (meth) acrylate, 2,4-dibromophenyl (meth)
Aromatic mono (meth) acrylates such as acrylate, 2,4,6-tribromophenyl (meth) acrylate, phenylthioethyl (meth) acrylate, and phenylthioethoxyethyl (meth) acrylate; Bis (4- (meth) acryloxyethoxyphenyl) methane, bis (4- (meth) acryloxydiethoxyphenyl) methane, 2,2-bis (4- (meth) acryloxyethoxyphenyl) propane, 2,2 -Bis (4- (meth) acryloxydiethoxyphenyl) propane, 2,
2-bis (4- (meth) acryloxypentaethoxyphenyl) propane, 2,2-bis (4- (meth) acryloxypropoxyphenyl) propane, 2,2-bis (4- (meth) acryloxydipropoxy) Phenyl) propane, 2,2-bis (4- (meth) acryloxyethoxy-3,5-dibromophenyl) propane, 2,2-
Bis (4- (meth) acryloxydiethoxy-3,5-
Dibromophenyl) propane, 2,2-bis (4- (meth) acryloxypentaethoxy-3,5-dibromophenyl) propane, bis (4- (meth) acryloxyethoxyphenyl) sulfone, bis (4- (meth ) Acryloxydiethoxyphenyl) sulfone, bis (4-
Ester di (meth) acrylyl having an aromatic skeleton such as (meth) acryloylthiophenyl) sulfide and bis (4- (meth) acryloxyethylthiophenyl) sulfide
G, bis (4- (meth) acryloxycyclohexyl)
Methane, bis (4- (meth) acryloxyethoxycyclohexyl) methane, bis (4- (meth) acryloxydiethoxycyclohexyl) methane, bis (4- (meth) acryloxycyclohexyl) propane, bis (4
-Di (meth) acrylate of an alicyclic skeleton such as (meth) acryloxyethoxycyclohexyl) propane, bis (4- (meth) acryloxydiethoxycyclohexyl) propane, dicyclopentanedi (meth) acrylate , Ethylene glycol di (meth) acrylate,
Diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol (n = 4 to 15) di (meth) acrylate
Propylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, polypropylene glycol (n = 4 to 15) di (meth) acrylate, 1,4-butanediol Ru (meth) acrylate, polybutylene glycol (n = 2 to 15) di (meth) acrylate, neopentyl glycol di (meth)
Acrylate, di (meth) acrylate of hydroxyhivalic acid neopentyl glycol ester, 1,6-hexanediol di (meth) acrylate, 1,9-nonandiodiol di (meth) acrylate, etc. Ester di (meth) acrylate having an aliphatic skeleton, other trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, ditrimethylol Propanetetra (meth) acrylate, dipentaerythritol
And polyfunctional (meth) acrylates such as rupenta (meth) acrylate.

Specific preferred examples of the component (a-2) include tris (isocyanatohexyl) isocyanurate.
G, isophorone diisocyanate, bis (4,4'-isocyanatocyclohexyl) methane, 1,3-bis (isocyanatomethyl) cyclohexane, metaxylylene diisocyanate, 2,4-tolylene diisocyanate −
Polyisocyanate compounds such as 2,6-tolylene diisocyanate and 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate,
Urethane poly (meth) acrylate which is a reaction product with a hydroxyl group-containing (meth) acrylate such as 2-hydroxybutyl (meth) acrylate or 4-hydroxybutyl (meth) acrylate is used. No.

Specific preferred examples of the component (a-3) include 2,2-bis (4-glycidyloxycyclohexyl) propane, 2,2-bis (4-glycidyloxyphenyl) propane, and bisphenol A diglycidyl. Epoxy poly (a reaction product of (meth) acrylic acid with an epoxy compound such as ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, tetrabromobisphenol A diglycidyl ether, tetrabromobisphenol S diglycidyl ether, etc. (Meth) acrylates.

Specific preferred examples of the component (a-4) include at least one of maleic acid, fumaric acid, phthalic acid, and succinic acid and ethylene glycol, propylene glycol, butylene glycol, and trimethylol. At least one of lupropane or pentaerythritol
Species and polyester poly (meth) acrylates which are reactants with methacrylic or acrylic acid.
As the above-mentioned various components (A), one kind may be used alone, or two or more kinds may be used in combination.

The component (B) is an active energy ray-sensitive catalyst, more preferably one that generates a radical source mainly in response to ultraviolet rays having a wavelength of 200 to 400 nm. Specific examples thereof include benzoin, benzoin monomethyl ether,
Benzoin isopropyl ether, acetoin, benzyl, benzophenone, p-methoxybenzophenone, diethoxyacetophenone, benzyldimethyl ketal,
2,2-diethoxyacetophenone, 1-hydroxycyclohexylphenyl ketone, methylphenylglyoxyle
Carbonyl compounds such as ethylphenylglyoxylate and 2-hydroxy-2-methyl-1-phenylpropan-1-one; sulfur compounds such as tetramethylthiuram monosulfide and tetramethylthiuram disulfide; Acylphosphine oxides such as 6-trimethylbenzoyldiphenylphosphine oxide and the like can be mentioned. These are used in one kind or in a mixture of two or more kinds. Among them, benzophenone, benzoin isopropyl ether, methylphenylglyoxylate, 1-hydroxycyclohexylphenylketone, benzyldimethylketal, 2,4,6-
Trimethylbenzoyldiphenylphosphine oxide is more preferred.

The proportion of the component (B) used is (A) to (C)
The amount is preferably 0.005 to 5 parts by weight, more preferably 0.02 to 2 parts by weight, per 100 parts by weight of the total amount of the components. If the amount of the component (B) is less than 0.005 parts by weight, the curability tends to be insufficient. If the amount exceeds 5 parts by weight, the deep part curability tends to decrease and coloring tends to occur. .

The component (C) is a heat-sensitive catalyst, and ordinary organic peroxides or azo compounds can be used. Specifically, benzoyl peroxide, octanoyl peroxide, diisopropyl peroxypercarbonate, bis (4-t-butylcyclohexyl) peroxydica carbonate, t-butyl peroxyisobutyrate, t Organic peroxides such as -butylperoxy-2-ethylhexanoate, 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile,
Azo compounds such as 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile) and 2,2'-azobis (2-methylbutyronitrile) are exemplified. (C)
The proportion of the components used is 100% of the total amount of components (A) to (C).
The amount is preferably 0 to 5 parts by weight, more preferably 0.005 to 2 parts by weight. If the amount of the component (C) exceeds 5 parts by weight, the mechanical strength of the lens portion 7 tends to decrease, and the lens portion 7 tends to be colored.

As shown in FIG. 1, the backlight of the present invention has a light source 2 such as a fluorescent lamp disposed at one end of a light guide 3 and a fluorescent light as described above on the light guide 3. The lens sheet 1 containing a whitening agent is mounted. In addition, the light guide 3 is usually provided with a diffusion sheet 4 on an emission surface, and a reflection layer formed of a reflection film or the like on a surface opposite to the emission surface. The backlight of the present invention is not limited to the configuration shown in FIG. 1, but may have various configurations according to the purpose of use and the like. For example, the light source 2 may be arranged at at least one end of the light guide 3, but a plurality of light sources 2 may be arranged as necessary. Further, the light emitting surface of the light guide 3 may be formed as a diffusion surface or a lens surface, or a light amount adjusting mechanism may be provided so that light can be uniformly emitted from the entire light guide 3 by printing or the like. Further, as the shape of the light guide 3, various shapes such as a sheet shape, a cross-sectional wedge shape, and a hull shape can be used.

[0027]

【Example】

Example 1 100 parts by weight of a mixture composed of 50% by weight of "FA-321M" manufactured by Hitachi Chemical Co., 20% by weight of "KAYARADR-604" manufactured by Nippon Kayaku Co., and 30% by weight of "Biscoat # 192" manufactured by Osaka Organic Chemicals. 0.005 parts by weight of "Leucopur EGM" manufactured by Sando as a fluorescent whitening agent and "Darocur 1173" manufactured by Merck as a photocuring catalyst.
(Photo-curing catalyst) A UV-curable resin liquid containing 1.5 parts by weight of a brass JIS 2804-compliant 3 mm × 300
After a prism array having a pitch of 50 μm and an apex angle of 95 ° was cut continuously in parallel on a plate of mm × 400 mm, a lens mold provided with Kanigen plating was prepared. Then, after injecting an ultraviolet curable resin liquid into the lens mold, a thickness 12 of approximately the same size is obtained.
A 5 μm polyester film (one-sided easy-adhesion type film A4250 manufactured by Toyobo) was overlaid. Then, the resin was irradiated with ultraviolet rays for 45 seconds by three 6.4 kw ultraviolet lamps of 80 w / cm and installed at the upper part of the lens mold manufactured by Western Quartz Co., Ltd. to cure the resin. I got a sheet.

A diffusion film "# 432" manufactured by Toray Industries Co., Ltd. is placed on a light guide made of Acrylite "# 000" manufactured by Mitsubishi Rayon Co., Ltd. having a cold cathode tube manufactured by Stanley on one end face. A backlight was constructed by mounting the lens sheet obtained above. With a BM-7 type luminance measuring device manufactured by Tokyo Kogaku Co., Ltd. installed at a position 1 m in front of the backlight,
When the front luminance was measured, it was found to have a luminance of 610 cd / m ² . Similarly, when the luminance without the prism sheet was measured, it was 370 cd / m ² , and the luminance improvement rate by the prism sheet was 65%.

Comparative Example 1 A mixture 100 comprising 50% by weight of "FA-321M" manufactured by Hitachi Chemical Co., Ltd., 20% by weight of "KAYARADR-604" manufactured by Nippon Kayaku Co., Ltd. and 30% by weight of "Biscoat # 192" manufactured by Osaka Organic Chemicals. A prism sheet was obtained in the same manner as in Example 1 by adding a UV curable resin liquid in which 1.5 parts by weight of “Darocur 1173” (photocuring catalyst) manufactured by Merck as a photocuring catalyst was added to the weight part. A backlight was constructed in the same manner as in Example 1 using the obtained prism sheet.
When the front luminance was measured by a BM-7 type luminance measuring device manufactured by Tokyo Kogaku Co., Ltd., which was installed at a position 1 m in front of the backlight, the luminance was 549 cd / m ² . Similarly, when the luminance without the prism sheet was measured, it was 371 cd / m ² , and the luminance improvement rate by the prism sheet was 48%.

[0030]

According to the present invention, an ultraviolet component having a wavelength of 330 to 380 nm, which has not contributed to the improvement of the conventional luminance, is obtained by incorporating a fluorescent whitening agent into a lens sheet.
By using fluorescent light having a wavelength of 400 to 450 nm, the brightness as a backlight can be improved without using a plurality of lens sheets.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a structure of a backlight.

FIG. 2 is a schematic view showing the structure of a lens sheet.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Lens sheet 2 ... Light source 3 ... Light guide 4 ... Diffusion film 5 ... Liquid crystal unit 6 ... Transparent base material 7 ... Lens part

Claims (2)

[Claims] 1. A lens sheet comprising a lens sheet in which a large number of lens rows are arranged in parallel on at least one surface, wherein the lens sheet contains a fluorescent whitening agent. 2. A light source and at least one light source facing the light source.
A light guide having one side end surface as a light incident surface and one surface substantially orthogonal to the light incident surface as a light exit surface, and a plurality of light guides disposed on at least one surface provided on the light exit surface side of the light guide. A backlight in which a lens sheet in which the lens rows are arranged in parallel is mounted, wherein the lens sheet contains a fluorescent whitening agent.