JPH09281311A - Prism sheet and surface illumination device formed by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a prism sheet capable of sufficiently suppressing the occur rence of Newton rings, obscuring flaws and maintaining well the effect of con densing incident light in a front surface direction. SOLUTION: A prism array forming layer 14 is attached to the front surface side of a base body layer 12 and a light diffusion layer formed by supporting many glass microrods 16 sized <=30μm in diameter by a supporting layer 18 is attached to the rear surface side thereof. The front surfaces of the prism array forming layer 14 are formed as prism arrays arranged with plural isosceles triangle unit prisms 14a of 90 deg. in vertex angle θ.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a prism sheet technique and a planar illumination technique using the prism sheet, and more particularly to a rear illumination device used in a liquid crystal display device or the like, and its front face. Regarding a prism sheet used for improving brightness, between the prism sheet and another adjacent constituent member of the back lighting device, between the prism sheet and an adjacent constituent member of the liquid crystal unit, or a plurality of prism sheets are stacked. The present invention relates to a technology for preventing generation of interference fringes (Newton's rings) generated between prism sheets and a technology for making defects in the prism sheet and other components of the back lighting device inconspicuous.

[0002]

2. Description of the Related Art In recent years, a portable notebook personal computer equipped with a color liquid crystal display device or a portable liquid crystal television receiver or a video integrated liquid crystal television receiver using a color liquid crystal panel (color liquid crystal display device). In such products that are driven by batteries, the large power consumption of the liquid crystal display device is an obstacle to extending the driving time of the products by the batteries. Above all,
The ratio of power consumption of the back lighting device (backlight) used in the liquid crystal display device is large, and keeping it low is an important goal for extending the driving time of the product by the battery and increasing the practical value of the product. Has been done.

In order to achieve this goal, if the brightness of the backlight is lowered in order to keep the power consumption low, the screen of the display device becomes dark, which is not preferable. Therefore, as a means for improving the optical efficiency of the backlight in order to suppress the power consumption without sacrificing the brightness, one as shown in FIG. 5 is known. In FIG. 5, 5 is a liquid crystal unit, and a backlight unit is arranged below it. In the backlight unit, a prism sheet 1 in which a number of unit prisms are arranged on an upper surface to form a prism array is installed on a light guide 3 via a light diffusion sheet 4, and is opposed to a side surface of the light guide. The light source 2 is arranged. Light emitted from the light source 2 enters the light guide 3 from the side surface, exits from the upper surface of the light guide body, is diffused by passing through the light diffusion sheet 4, and enters the prism sheet 1 from the lower surface. The light is emitted from the prism row forming surface (upper surface) of the prism sheet, and the liquid crystal unit 5 is illuminated from the rear surface (lower surface). An observer of the liquid crystal display device is located above the front surface (upper surface) of the liquid crystal unit 5.

Although such a prism sheet is used as one sheet in the example of FIG. 5, in JP-B-1-37801, two prism sheets have a unit prism direction with a certain angle. There is described an example in which it is used by superimposing it on each other to improve the brightness.

[0005]

By the way, when two prism sheets are used in a stacked manner as described in Japanese Patent Publication No. 1-37801, the at least one of the two prism sheets is If the prism sheet has a curvature due to some reason such as being bent or warped, or if a foreign substance is interposed between them, the light passing through these prism sheets will have an optical path difference, It has been pointed out that Newton's rings appear, and it looks as if a defect had occurred in the liquid crystal display itself.

It has been pointed out that such a Newton's ring is also generated between the prism sheet and the surface of the light guide body and between the prism sheet and the glass surface constituting the liquid crystal unit.

Further, when the prism sheet is used for the above-mentioned applications, there is a problem that the yield is lowered due to scratches on the prism sheet itself. Initially, as the prism sheet for the above applications, one in which prism rows were formed by press molding on one surface of a thermoplastic transparent plastic plate was used, but nowadays, in order to accurately transfer a fine shape. The mainstream is the one in which a prism array is formed on an ultraviolet curable resin applied to one surface of a transparent resin sheet. In general, such a transparent resin sheet and an ultraviolet curable resin are easily scratched, and are easily scratched due to careless handling during manufacturing or assembly into a backlight. When light is emitted through such a scratch, the emitted light is sharply refracted, the scratch is recognized as a defect point that is significantly brighter than the surroundings, and becomes a defect that can be confirmed by an observer through the liquid crystal unit. This is a factor that reduces the yield of itself.

The general mechanism of the above Newton ring generation will be described. As shown in FIG. 6, when a smooth optical curved surface 6 having a spherical surface with a radius of curvature R and a smooth optical flat surface 7 are adjacent to each other, the Newton ring has a curved surface 6 and a flat surface 7.
It is observed as a concentric ring (Newton's ring) 9 as shown in FIG. 7 based on the formation of the air layer 8 having a gradually changing space between and.

Therefore, if the surface of the prism sheet on which the prism rows are not formed is not a smooth surface and fine irregularities are formed, the occurrence of Newton's rings can be prevented. For this reason, it is conceivable to roughen the surface on which the prism array is not formed with an abrasive such as sandpaper, but such a method remarkably scatters the incident light to the prism array, and the prism sheet Since the original function of condensing the incident light in the front direction is reduced, it is not an effective means for solving the problem.

On the other hand, as a general method for preventing scratches on the prism sheet,
The most widely used method is to attach a protective sheet until the backlight is assembled and prevent scratches, but as a result, the cost of the protective sheet that is thrown away increases the price of the backlight, and above all We cannot deal with the scratches that were made in the process before applying the protective sheet.

Therefore, the present invention solves the above-mentioned problems of the prior art and can sufficiently suppress the generation of Newton's rings even if the prism sheets are adjacent to each other or the prism sheet is adjacent to another member. Moreover, it is an object of the present invention to provide a prism sheet that can favorably maintain the effect of collecting incident light in the front direction.

A further object of the present invention is to make scratches on the prism sheet inconspicuous.

It is another object of the present invention to provide a planar lighting device using such a prism sheet.

A further object of the present invention is to make scratches on members other than the prism sheet less noticeable in such a surface illumination device.

[0015]

According to the present invention, in order to achieve the above object, the first surface side of a plate-shaped light-transmitting substrate having two main surfaces, a first surface and a second surface. A prism sheet is provided in which a prism array is formed, and a light diffusion layer including a large number of translucent microrods is formed on the second surface side of the base material.

In one aspect of the present invention, the base material includes a base layer and a prism row forming layer provided on the first surface side of the base layer, and the prism row forming layer is the first row. The prism array is formed on the surface on the surface side.

In one aspect of the present invention, the light diffusing layer is formed by adhering the microrods to a surface of the base material on the second surface side by a microrod supporting layer, and the light diffusing layer is the above. It has an uneven surface corresponding to the shape of the microrod.

In one aspect of the present invention, the base material includes a base layer and the light diffusing layer provided on the second surface side of the base layer, and the microrod is contained in the light diffusing layer. Are dispersed.

In one aspect of the present invention, the prism array is formed by repeating unit prisms formed along the first surface.

In one aspect of the present invention, the unit prism is an isosceles triangular prism.

In one aspect of the present invention, the apex angle of the unit prism is in the range of 60 ° to 130 °.

In one aspect of the present invention, the base layer has a parallel plate shape.

In one aspect of the present invention, the base layer and the prism array forming layer are integrated.

In one embodiment of the present invention, the base material is made of synthetic resin.

In one aspect of the present invention, the microrod is made of glass.

In one aspect of the present invention, the microrod has a diameter in the range of 1 μm to 30 μm.

In one aspect of the present invention, the length of the microrod is in the range of 1 to 100 times the diameter.

In one aspect of the present invention, the refractive index of the microrod is higher than the refractive index of other members constituting the base material.

Further, according to the present invention, in order to achieve the above object, light from the light source is made incident on the second surface of the prism sheet and light is emitted from the first surface. A planar lighting device is provided.

In one aspect of the present invention, the light from the light source is made to enter the prism sheet after passing through the light diffuser disposed on the second surface side of the prism sheet. .

According to one aspect of the present invention, there is provided a light guide body which is disposed on the second surface side of the prism sheet and has a first surface on the prism sheet side and a second surface on the opposite side of the first surface. On the other hand, the light from the light source is incident from one of the side surfaces crossing the first surface and the second surface, and the light guided in the light guide body is emitted from the first surface to form the prism. It is designed to be directed toward the seat.

In one aspect of the present invention, the light diffuser is located between the first surface of the light guide and the prism sheet.

In one embodiment of the present invention, at least one prism sheet is used in addition to the prism sheet to which the light from the light source is incident, and all prism sheets are adjacent to each other. The first surface and the second surface are arranged so as to face each other.

In one aspect of the present invention, a total of two prism sheets are used, and the prism sheets are arranged so that the first in-plane directions of the prism rows are substantially orthogonal to each other.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a first prism sheet according to the present invention.
FIG. 3 is a schematic perspective view showing the embodiment of FIG.

In FIG. 1, 12 is a base layer. As the base layer 12, a film made of a transparent synthetic resin such as an acrylic resin, a polycarbonate resin, a vinyl chloride resin, a polymethacrylimide resin or a polyethylene terephthalate resin can be used. Alternatively, as the base layer 12, a flexible glass plate that transmits ultraviolet rays can be used. The base layer 12 desirably has a smooth surface,
It is preferable that at least one surface has a coat layer for improving the adhesion to the active energy ray curable resin that forms the prism array, for example, the ultraviolet curable resin. Examples of such a coat layer include a vinyl chloride-vinyl acetate copolymer, a butyral-based primer, a urethane-based primer, a phenoxy-based primer, and a resin solution containing colloidal silica. The coat layer may have its surface subjected to treatment such as ozone treatment or hydrogen flame treatment.

The thickness T ₁ of the base layer 12 is, for example, 0.1 to 10.
0.5 mm.

A prism array forming layer 14 is provided on the upper surface side of the base layer 12. As the prism array forming layer 14, an active energy ray curable resin such as an ultraviolet curable resin can be used. The composition of this resin contains, for example, the following components (A), (B) and (C) as main components.

Component (A) [at least one monomer or oligomer capable of radical polymerization]: (A)
The component determines the optical performance of the manufactured prism, and is preferably selected as appropriate according to the desired performance of the prism. As the component (A), monomers or oligomers capable of radical polymerization are used alone or in combination of two or more kinds, but it is usually preferable to use two or more kinds,
The mechanical strength, impact resistance, heat resistance, surface hardness, chemical resistance and dyeability required for the prism sheet can be imparted. Further, by using a compound having an acryloyl group or a methacryloyl group as a radically polymerizable functional group in an amount of 60% by weight or more of the composition, partial co-polymerization by irradiation with active energy rays causes instant immobilization. Optical distortion due to convection in the row forming layer is reduced, which is preferable.

Specific examples of the component (A) include ester-type (meth) acrylates (a-obtained by condensation reaction of an aliphatic, alicyclic or aromatic mono- or polyalcohol with acrylic acid or methacrylic acid. 1) or a urethane poly (meth) acrylate (a-2) obtained by a urethanization 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, or , At least 2 in the molecule
Epoxy poly (meth) acrylate (a-3) obtained by glycidyl group ring-opening reaction of a compound having one epoxy group with acrylic acid or methacrylic acid, saturated or unsaturated polyvalent carboxylic acid, polyhydric alcohol and ( (Meth) acryloyl-functional monomer or oligomer such as polyester (meth) acrylate (a-4) obtained by condensation reaction with (meth) acrylic acid, vinyl such as styrene, chlorostyrene, bromostyrene, dibromostyrene, divinylbenzene Compound (a-5) and (meth) allyl compound (a- such as diethylene glycol bisallyl carbonate, diallyl phthalate and diallyl biphenylate
6) can be mentioned. These monomers may be used alone or in combination 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,
Alicyclic mono (meth) acrylates such as dicyclopentenyl (meth) acrylate, isobornyl (meth) acrylate, bornyl (meth) acrylate, 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, 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) acryloxydipropoxyphenyl) 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-
Esters of aromatic skeleton such as (meth) acryloylthiophenyl) sulfide, bis (4- (meth) acryloxyethylthiophenyl) sulfide, di (meth) acrylate, bis (4- (meth) acryloxycyclohexyl)
Methane, bis (4- (meth) acryloxyethoxycyclohexyl) methane, bis (4- (meth) acryloxydiethoxycyclohexyl) methane, bis (4- (meth) acryloxycyclohexyl) propane, bis (4
Ester di (meth) acrylate of alicyclic skeleton such as-(meth) acryloxyethoxycyclohexyl) propane, bis (4- (meth) acryloxydiethoxycyclohexyl) propane, dicyclopentadi (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 di (meth) acrylate, polybutylene glycol (n = 2-15) di (meth) acrylate, neopentyl glycol di (meth)
Acrylate, ester di (meth) acrylate of aliphatic skeleton such as di (meth) acrylate of neopentylglycol hydroxyester, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate , Other polyfunctionality of trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, etc. (Meth) acrylate is mentioned.

Specific preferred examples of the component (a-2) include tris (isocyanatohexyl) isocyanurate, 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, 2
Examples include urethane poly (meth) acrylate, which is a reaction product with (meth) acrylate having a hydroxyl group such as -hydroxybutyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate.

Specific preferred examples of the component (a-3) include 2,2-bis (4-glycidyloxycyclohexyl) propane, 2,2-bis (4-glycidyloxyphenyl) propane, bisphenol A diglycidyl ether, An epoxy poly (meth) acrylate which is a reaction product of an epoxy compound such as bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, tetrabromobisphenol A diglycidyl ether, tetrabromobisphenol S diglycidyl ether and (meth) acrylic acid is used. Can be mentioned.

Specific preferred examples of the component (a-4) include at least one of maleic acid, fumaric acid, phthalic acid or succinic acid and at least one of ethylene glycol, propylene glycol, butylene glycol, trimethylolpropane or pentaerythritol. seed,
And polyester poly (meth) acrylate which is a reaction product with methacrylic acid or acrylic acid.

The above-mentioned various components (A) may be used alone or in combination of two or more kinds.

Component (B) [Active energy ray sensitive catalyst]: This component (B) is mainly used in the wavelength range of 200 to 400.
It is more preferable to generate a radical source in response to ultraviolet rays of nm, and specific examples thereof include benzoin, benzoin monomethyl ether, benzoin isopropyl ether,
Acetoin, benzyl, benzophenone, p-methoxybenzophenone, diethoxyacetophenone, benzyldimethylketal, 2,2-diethoxyacetophenone, 1-hydroxycyclohexylphenylketone, methylphenylglyoxylate, ethylphenylglyoxylate, 2-hydroxy- Carbonyl compounds such as 2-methyl-1-phenylpropan-1-one, sulfur compounds such as tetramethylthiuram monosulfide and tetramethylthiuram disulfide, acylphosphine oxides such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide Etc. can be mentioned.
These are used in one kind or in a mixture of two or more kinds. Among these, benzophenone, benzoin isopropyl ether, methylphenyl glyoxylate, 1-hydroxycyclohexyl phenyl ketone, benzyl dimethyl ketal, and 2,4,6-trimethylbenzoyldiphenylphosphine oxide are more preferable.

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

Component (C) [heat-sensitive catalyst]: As the component (C), an ordinary organic peroxide or an azo compound can be used. Specifically, benzoyl peroxide, octanoyl peroxide, diisopropyl peroxypercarbonate, bis (4-t-butylcyclohexyl)
Organic peroxides such as peroxydicarbonate, t-butylperoxyisobutyrate and t-butylperoxy-2-ethylhexanoate, 2,2′-azobis (2,2
4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis (2-methylbutyronitrile) Aromatic compounds such as ronitrile).

The proportion of the component (C) used is from (A) to (C).
The total amount of the components is 0.005 to 5 parts by weight, more preferably 0.02 to 2 parts by weight, based on 100 parts by weight. If the amount of the component (C) is less than 0.005 parts by weight, the curability tends to be insufficient, and if it exceeds 5 parts by weight, the mechanical strength of the prism tends to decrease and coloring may occur.

The resin composition of the prism array forming layer 14 may be, if necessary, an antioxidant, an anti-yellowing agent, an ultraviolet absorber, a bluing agent, a pigment, an anti-settling agent, an antifoaming agent, an antistatic agent. Various additives such as agents and antifogging agents may be included.

The prism array forming layer 14 has a smooth lower surface joined to the base layer 12, and has a unit prism 14a on the upper surface.
Is formed in parallel with each other to form a prism row 14b. The unit prism 14a is an isosceles triangular prism, and its apex angle θ is preferably in the range of 60 ° to 130 °, for example. That is, when perfect diffused light enters the prism sheet from the lower surface side, the apex angle θ is 9
The optimum angle is 0 °, but in actual use, incident light often has a certain degree of directionality.
By appropriately selecting within the range of 90 ° to 130 °, it is possible to enhance the light collecting effect in the front direction.

The thickness T ₂ of the prism array forming layer 14 is, for example, about 4 to 100 μm, and the height H of each unit prism 14a is, for example, about 4 to 50 μm.
The arrangement pitch P of 4a is, for example, about 20 to 100 μm.

A large number of translucent microrods 16 are supported on the lower surface side of the base layer 12. Micro rod 1
A support layer 18 is used for the support of 6. The supporting layer 18 may be made of the same resin as the prism array forming layer 14 described above.

The micro rod 16 may be made of glass, for example. As the microrod 16, specifically, non-alkali glass, synthetic fused silica, general optical glass, crown glass, Pyrex (borosilicate glass), synthetic sapphire, silicon and the like can be used. Examples of components that can be contained in the glass microrod include lead oxide, zinc oxide, boron oxide, silicon oxide, calcium oxide, aluminum oxide, sodium oxide, lithium oxide, magnesium oxide, iron oxide and the like.

The size of the microrod 16 is, for example, about 1 to 30 μm in diameter, and the length is about 1 to 100 times the diameter, for example, about 1 to 30 μm. Micro rod 16
Is preferably distributed as evenly as possible on the lower surface of the base layer 12, and its distribution density is, for example, 0.01 to 1 g / c.
m ² . If the microrod distribution density is too small, the effect of adding the microrods may be insufficient, and if the microrod distribution density is too large, the condensing effect of the prism may decrease or the brightness of the illumination device may decrease.

The support layer 18 preferably has a refractive index difference of about 0.5% or more with the microrod 16. Support layer 1
8 preferably has a lower refractive index than the base layer 12 and the microrod 16. In that case, the support layer 18 functions as an antireflection film. The refractive index of the support layer 18 is preferably 1.2 to 1.65. Also, the micro rod 1
The refractive index of 6 is preferably 1.5 to 1.85, more preferably 1.5 to 1.65.

The thickness of the support layer 18 can be set to such an extent that the microrods 16 form an unevenness on the surface of the sheet by a portion having a diameter of half or more. That is, the light diffusion layer formed by the microrod 16 and the support layer 18 has an uneven surface corresponding to the shape of the microrod 16.

The above base layer 12 and prism array forming layer 14
The transparent base material 10 is configured to include the microrods 16 and the supporting layer 18 thereof.

Next, a method for manufacturing the above prism sheet will be described.

First, an ultraviolet curable resin used for the prism array forming layer 14 is prepared. The ultraviolet curable resin is prepared by mixing the refractive index adjusting component [(A) component] and the catalyst [(B) component and (C) component] and defoaming in advance.
Filter the dust in the liquid with a filter. After injecting the ultraviolet curable resin composition prepared in this way into a mold having a prism shape engraved thereon, the transparent substrate layer is superposed and irradiated with ultraviolet rays from an ultraviolet light source through the transparent substrate layer to polymerize,
Peel from the mold. As a result, a preformed body is obtained.

As a mold used for forming the prism array, a metal mold such as aluminum, brass, steel or the like, a silicone resin, a urethane resin, an epoxy resin, an ABS resin,
A mold made of a synthetic resin such as a fluorine resin or polymethylpentene resin, an electroforming mold made by the Ni electroforming method, or a plated product of the above materials can be used, but a metal is used in terms of heat resistance and strength. It is desirable to use a mold made of.

Next, an ultraviolet curable resin composition used for the support layer 18 is prepared, an auxiliary agent and a catalyst are mixed, and defoaming is performed.
After filtration, stir well. The ultraviolet curable resin composition thus obtained was preliminarily used in the prism array 14
Application is performed on the above preform placed on a table on which a soft sheet is laid so that b is on the lower side. As a coating method, a general coating method such as a roll coating method, a doctor blade coating method, a bar coating method, a spray coating method, a curtain coating method, a flow coating method or a dip coating method can be used. Next, an appropriate amount of glass microrods are scattered, and ultraviolet rays are irradiated in a state of blocking air in an inert gas to polymerize and cure the resin composition to obtain a prism sheet.

As the ultraviolet light source, a usual ultraviolet light source such as a fluorescent lamp, a chemical lamp, a high pressure mercury lamp, a low pressure mercury lamp, a metal halide lamp or the like can be used.

FIG. 2 shows a second prism sheet according to the present invention.
FIG. 3 is a schematic perspective view showing the embodiment of FIG. In this figure, members having the same functions as those in FIG. 1 are denoted by the same reference numerals.

In this embodiment, a large number of microrods 1 are used.
6 is dispersed and supported in the support layer 18. The composition of the support layer 18 is the same as that of the first embodiment, but the thickness is different. In this embodiment, the support layer 1
The thickness of 8 is, for example, 5 to 100 μm. The lower surface of the light diffusion layer formed by the microrods 16 and the support layer 18 may have an uneven shape based on a part of the glass microrods 16, preferably a protrusion of less than half the diameter thereof. Good.

The method of manufacturing the prism sheet of this embodiment is the same as that of the first embodiment until the preformed body is obtained. Next, an ultraviolet curable resin composition used for the support layer 18 is prepared, an auxiliary agent, a catalyst and the like are mixed, and after defoaming and filtering, an appropriate amount of glass microrods are charged and sufficiently stirred. The glass microrod-containing UV-curable resin composition thus obtained is applied onto the above-mentioned preform which has been placed on a table on which a soft sheet is laid in advance so that the prism rows 14b face downward, A prismatic sheet is obtained by superimposing a transparent release substrate having good releasability with a curable resin and irradiating with ultraviolet rays in a state of blocking air to polymerize and cure the resin composition. In this case, the transparent release substrate used is preferably as thin as possible in order not to prevent the occurrence of irregularities on the surface of the light diffusion layer.

FIG. 3 shows a third prism sheet according to the present invention.
FIG. 3 is a schematic perspective view showing the embodiment of FIG. In this figure, members having the same functions as those in FIGS. 1 and 2 are designated by the same reference numerals.

In this embodiment, the base layer 12 and the prism array forming layer 14 in the second embodiment are integrated to form a prism array forming base layer 20. The prism row forming base layer 20 is made of the same material as the prism row forming layer 14 in the second embodiment. In order to obtain a preformed body composed of the prism row forming base layer 20, the releasability with the ultraviolet curable resin is used instead of the transparent base layer used when the prism row forming layer 14 of the first embodiment is prepared. Using a good transparent release substrate (having a good flat surface)
It may be peeled after the resin is cured by ultraviolet irradiation.

FIG. 4 is a schematic perspective view showing an embodiment of a planar lighting device using a prism sheet according to the present invention.
In this figure, members having the same functions as those in FIGS. 1 to 3 are designated by the same reference numerals.

In this embodiment, the two prism sheets 30 and 32 of the embodiment shown in FIG. 2 are arranged such that the prism row forming layer 14 is located on the upper surface side and the support layer 20 is located on the lower surface side. Overlaid. The prism direction of the prism sheet 30 (Y direction) and the prism direction of the prism sheet 32 (X direction) are orthogonal to each other. A backlight unit is arranged below the prism sheet 32. The backlight unit includes a diffusion film 34, a light guide 36, and a light source 38. The diffusion film 34 is located between the prism sheet 32 and the light guide 36, and the light guide 36 has a wedge shape whose thickness gradually changes in the X direction. Light source 3 extending in the Y direction adjacent to the end face
8 are arranged. 40 is a liquid crystal unit.

The light emitted from the light source 38 is transmitted to the light guide 36.
Light from the side surface, is emitted from the upper surface of the light guide body, is diffused by passing through the light diffusion sheet 34, is emitted through the prism sheets 32 and 30, and illuminates the liquid crystal unit 40 from the rear surface (lower surface). To do.

In this embodiment, the prism directions of the prism sheets 30 and 32 are orthogonal to each other, but if these directions are in the range of 50 ° to 130 °, especially 70 ° to 110 °, good functions are exhibited. It Further, the planar illumination device may be configured by using only one prism sheet (in the arrangement as shown in FIG. 5).

[0074]

The present invention will be described below with reference to examples.

[Example 1] Composition 1 below * 50 parts by weight of "FA-321M" manufactured by Hitachi Chemical Co., Ltd. * 20 parts by weight of "KAYARAD R-604" manufactured by Nippon Kayaku Co., Ltd. * "Viscoat # 192" manufactured by Osaka Organic Chemical Co., Ltd. 30 parts by weight * An ultraviolet-curable resin liquid consisting of 1.5 parts by weight of "Darocur 1173" manufactured by Ciba-Geigi (photocuring catalyst) was prepared.

A brass A4 size plate conforming to JIS 2804 has a pitch P = 50 μm and an apex angle θ = 90 °.
A prism-shaped mold was prepared.

After injecting an ultraviolet curable resin liquid into the prism type, a 125 μm-thick PET sheet (one-sided easy-adhesion type film manufactured by Toyobo Co., Ltd.) of approximately the same size was overlaid, and then 300 mm above the sheet. 80 installed
The resin was cured by irradiating it with ultraviolet rays for 30 seconds using a 6.4 kW ultraviolet lamp manufactured by Western Quartz Co., which has an irradiation intensity of W / cm, to obtain a preform.

The preform thus obtained was placed on a table on which a soft sheet was laid so that the prism rows were on the lower side, and a large number of glass microrods having a diameter of 10 μm and a length of 50 μm were mixed on the upper surface side. The following composition 2 * Hitachi Chemical Co., Ltd. "FA-321M" 75 parts by weight * Osaka Organic Chemical Co., Ltd. "Viscoat # 192" 25 parts by weight * Ciba-Geigy Co. (light curing catalyst) "Darocur 1173" 1.5 parts by weight UV curable resin liquid consisting of
It was applied so as to have a thickness of 0 μm. The distribution density of the glass microrods was 0.5 g / cm ² .

Next, a PET sheet (a film without easy adhesion treatment manufactured by Toyobo Co., Ltd.) having a thickness of 15 μm, which is slightly larger than the prism sheet, is superposed, and then 30 sheets above the sheet.
After irradiating UV rays for 30 seconds by a 6.4 kW UV lamp manufactured by Western Quartz Co., Ltd. with an irradiation intensity of 80 W / cm installed at 0 mm to cure the resin, PE
Only the T sheet was peeled off to obtain the prism sheet of the second embodiment in which the glass microrod dispersion supporting light diffusing layer was formed on the back surface side.

Next, as shown in FIG. 4, a light source 38 comprising a cold cathode tube manufactured by Stanley, an acrylic resin light guide 36 manufactured by Mitsubishi Rayon, and a diffusion film 34 manufactured by Toray.
The above-mentioned two prism sheets 30 and 32 were set in a backlight unit consisting of and so that the prism directions formed an angle of 90 ° with each other to fabricate a planar illumination device.
Then, the liquid crystal unit 40 was arranged on the prism sheet 30 of this planar lighting device, and the liquid crystal unit was driven under the illumination of the planar lighting device to see the occurrence state of Newton's rings. There wasn't.

The light guide 36 and the prism sheet 3 are also provided.
The planar illumination device of this example was manufactured by using an in-house scratch generator having a length of about 5 mm, a width of about 250 μm, and a depth of 500 μm, which was scratched by an in-house scratch generator using a design knife. Then, the liquid crystal unit 40 was arranged and the scratches were visually observed in the same manner, but it could not be confirmed at a level which would be a defect as a product.

Example 2 A preformed body was manufactured in the same manner as in Example 1, and the preformed body was placed on a table on which a soft sheet was laid so that the prism rows were on the lower side, and the preformed body was placed on the upper surface of the preformed body. A slight amount of the ultraviolet curable resin liquid excluding the microrods from the above composition 2 is applied and the thickness is about 2 by a bar coater.
It was adjusted to 0 μm.

Next, a glass microrod (PF-90 manufactured by Nippon Electric Glass Co., Ltd.) was added in an amount of 3 g / from above the preform.
After spraying to a density of about cm ² , put the whole stand in an acrylic box, replace the nitrogen in the box to shut off the air, and then install it at 300 mm above 80 W /
The resin was cured by irradiating the resin with ultraviolet rays for 40 seconds by using an ultraviolet irradiation device having an ultraviolet lamp of 6.4 kW having an irradiation intensity of cm and made by Western Quartz Co., Ltd. to obtain the prism sheet of the first embodiment.

Then, in the same manner as in Example 1, a planar illumination device as shown in FIG. 4 was produced using the prism sheet produced in Example 2. Then, in the same manner as in Example 1, the state of occurrence of Newton's rings was observed, but Newton's rings were not confirmed at all.

Further, the surface illumination device of this example was manufactured by using the scratched member in the same manner as in Example 1. Then, the scratches were visually observed in the same manner as in Example 1, but the scratches could not be confirmed at the level of defects.

[Comparative Example 1] A similar planar illumination device was produced using the prism sheet obtained by the same method as in Example 1 except that the glass microrods were not dispersed in the support layer. Then, in the same manner as in Example 1, when the state of occurrence of Newton rings was observed, Newton rings with a diameter of about 2 cm and a pitch of about 4 mm were confirmed.

Further, a surface illumination device of this comparative example was manufactured by using the scratched member in the same manner as in Example 1. Then, when the scratches were visually observed in the same manner as in Example 1,
It could be easily confirmed at the level of a defect as a product.

[0088]

As described above, according to the present invention, the light diffusion layer including a large number of light-transmissive microrods is formed on the side opposite to the side where the prism rows are formed. The appropriate light diffusion is achieved by this, and it is possible to prevent the occurrence of Newton rings between the prism sheets or between the prism sheet and other members without reducing the light collection effect in the front direction and the amount of transmitted light. Further, even if the prism sheet or other member is scratched, it can be made inconspicuous, and thus, the manufacturing allowable accuracy of the prism sheet and the planar lighting device can be loosened, and these products and the planar lighting can be made. The yield of products such as liquid crystal display devices using the device can be improved.

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing a first embodiment of a prism sheet according to the present invention.

FIG. 2 is a schematic perspective view showing a second embodiment of the prism sheet according to the present invention.

FIG. 3 is a schematic perspective view showing a third embodiment of the prism sheet according to the present invention.

FIG. 4 is a schematic perspective view showing an embodiment of a planar lighting device using a prism sheet according to the present invention.

FIG. 5 is a schematic perspective view showing a liquid crystal display device using a conventional backlight.

FIG. 6 is an explanatory diagram of occurrence of Newton's rings.

FIG. 7 is an explanatory diagram of Newton ring generation.

[Explanation of symbols]

 10 Transparent Base Material 12 Base Layer 14 Prism Row Forming Layer 14a Unit Prism 14b Prism Row 16 Glass Micro Rod 18 Glass Micro Rod Support Layer 20 Prism Row Forming Base Layer 30, 32 Prism Sheet 34 Light Diffusing Film 36 Light Guide 38 Light Source 40 LCD unit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location G02F 1/1335 530 G02F 1/1335 530

Claims (9)

[Claims] 1. A prism array is formed on a first surface side of a plate-shaped translucent base material having two main surfaces, a first surface and a second surface, and a prism row is formed on a second surface side of the base material. A prism sheet, wherein a light diffusion layer including a large number of translucent microrods is formed. 2. The base material is a base layer and the first base layer.
The prism row forming layer provided on the surface side, wherein the prism row is formed on the surface of the prism row forming layer on the first surface side. Prism sheet. 3. The light diffusing layer is formed by adhering the microrods to the surface of the base material on the second surface side by a microrod supporting layer, and the light diffusing layer is formed according to the shape of the microrods. The prism sheet according to claim 1, which has an uneven surface. 4. The base material is a base layer and the second base layer.
The prism sheet according to any one of claims 1 to 3, further comprising: the light diffusion layer provided on the surface side, wherein the microrods are dispersed in the light diffusion layer. . 5. The microrod has a diameter of 1 μm to 30.
The prism sheet according to any one of claims 1 to 4, wherein the prism sheet is in the range of µm. 6. The microrod has a length within a range of 1 to 100 times a diameter.
6. The prism sheet according to any one of 5 to 5. 7. The prism sheet according to claim 1, wherein a refractive index of the microrod is higher than a refractive index of other members constituting the base material. 8. A prism sheet according to claim 1, wherein the prism sheet has a first surface disposed on the second surface side and a prism sheet-side first surface opposite to the first surface. Light from a light source is incident on one of the side surfaces crossing the first surface and the second surface with respect to the light guide, and the light guided in the light guide is emitted from the first surface. A planar illumination device, characterized in that it is adapted to be directed toward the prism sheet. 9. A prism sheet according to any one of claims 1 to 7 is additionally used in addition to the prism sheet to which light from the light source is incident, and these two prism sheets are used. First of neighboring things
9. The planar illuminating device according to claim 8, wherein the surface and the second surface are opposed to each other and the first in-plane directions of the prism rows are arranged substantially orthogonal to each other.