JPH07159606A - Light-diffusing plate - Google Patents

Abstract

PURPOSE:To obtain a light-diffusing plate having high surface hardness which is hardly stuck with dust or damaged by scratches. CONSTITUTION:This light-diffusing plate is produced by forming a transparent resin layer and a conductive layer comprised of conductive particles of <=3mum average particle size on a rough surface of a light-diffusing film or sheet comprised of a transparent resin film or sheet at least one surface of which is finely roughened. The transparent resin layer consists of a (meth)acrylate compd. having at least two or more (meth)acryloyl groups in the molecule and a photopolymn. initiator. The conductive layer is formed to 0.5-50mum thickness by applying a coating liquid for the conductive layer and irradiating the layer with active rays.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light diffusing plate used in displays, lighting covers and the like.

[0002]

2. Description of the Related Art A light diffusing plate is used for diffusing light from a point light source or a linear light source or adjusting the angle of outgoing light to obtain a uniform surface illumination with high front brightness. It is used for screens and lighting equipment covers.

Conventionally, the light diffusion plate has been manufactured by forming a large number of fine irregularities on the surface of an extruded film or sheet of a highly transparent thermoplastic resin.

The shape of the irregularities is a continuous prism shape,
It is disclosed, for example, in JP-A-60-100103 and JP-A-2-228689 that the corrugated or triangular pyramidal protrusions have a uniform and high front luminance.

As the above-mentioned thermoplastic resin, polymethyl methacrylate, polycarbonate, polyvinyl chloride or the like, which has good transparency and good moldability, is used.

However, the above-mentioned thermoplastic resin has a charging property, and dust and dirt are liable to be attached in the step of incorporating the light diffusing plate into the light diffusing unit, which lowers the light diffusing function and thus lowers the product yield. was there.

Polycarbonate and polyvinyl chloride are inexpensive and have excellent characteristics, but have a low surface hardness, and a light diffusing plate is rolled and stored in a roll shape, or cut to protect the light of a liquid crystal display. There is a problem in that the yield of the product is reduced because it is easy to be damaged in the process of incorporating it in the diffusion unit, and if it is damaged, the part becomes bright spots or shadows and the function is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above drawbacks, and an object of the present invention is to provide a light diffusing plate in which dust and dirt are not easily attached.

A further object of the present invention is to provide a light diffusing plate having a high surface hardness and being hard to be scratched on the surface.

[0009]

The light diffusing plate of the present invention can be obtained by providing a conductive layer on the surface of the light diffusing film or sheet having fine irregularities.

The transparent resin film or sheet is
Known materials can be used, for example, transparent materials such as polycarbonate, polymethylmethacrylate, polyvinyl chloride, polyester, cellulose acetate butyrate, polyethylene-based ionomer (trade name: Sarlin), etc. Examples thereof include a resin film or sheet provided with concavities and convexities of 0.05 to 5 mm in a continuous prism shape, a wave shape, or a triangular pyramid projection shape.

The conductive layer comprises a transparent resin binder and conductive powder.

The above transparent resin binder may be transparent, and for example, polymethylmethacrylic acid; polyvinyl alcohol such as polyvinyl acetal and polyvinyl butyral can be acetalized with an aldehyde compound. Polyacetal resin obtained by the above; polyester resin; urethane resin; thermoplastic resin such as epoxy resin, photopolymerizable resin, and the like, and a polymer of α, β-unsaturated ethylene-based monomer soluble in an organic solvent. Polymers, copolymers, photopolymerizable resins, etc. are preferably used.

Examples of the α, β-unsaturated ethylenic monomer include styrene, p-methylstyrene, α-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-hexylstyrene and p-hexylstyrene. -Octylstyrene, p-methoxystyrene, p-phenylstyrene,
Styrenes such as 3,4-dimethylchlorostyrene; α-
Vinylnaphthalene; ethylene, propylene, butylene or α-olefins such as C _{5 to} C ₃₀ ; vinyl halides such as vinyl chloride and vinyl bromide; vinyl esters such as vinyl acetate, vinyl propionate and vinyl butyrate; )
Methyl acrylate, propyl (meth) acrylate, butyl (meth) acrylate, octyl (meth) acrylate,
Isobutyl (meth) acrylate, lauryl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 2-chloroethyl (meth) acrylate, α-chloro (meth)
(Meth) acrylic acid esters such as methyl acrylate, phenyl (meth) acrylate, dimethylaminoethyl (meth) acrylate; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether; vinyl methyl ketone, vinyl ethyl ketone And the like; N-vinyl compounds such as N-vinylpyrrole and N-vinylindole; (meth) acrylonitrile; (meth) acrylic acid amides and the like, and these may be used alone. However, two or more kinds may be used in combination.

The photopolymerizable resin is a (meth) acrylate.
What comprises a compound and a photopolymerization initiator is preferably used.

Examples of the (meth) acrylate compound include (meth) acrylate compounds having at least two (meth) acryloyl groups in the molecule.

Examples of the (meth) acrylate compound include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate and nona. Ethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, tetrapropylene glycol di (meth) acrylate, nonapropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate 2,2-bis [4- (acryloxydiethoxy) phenyl] propane, 2,2-
Bifunctional (meth) acrylates such as bis [4- (methacryloxydiethoxy) phenyl] propane, 3-phenoxy-2-propanoyl acrylate, and 1,6-bis (3-acryloxy-2-hydroxypropyl) -hexyl ether. , Or pentaerythritol tri (meta)
Acrylate, trimethylolpropane tri (meth) acrylate, glycerol tri (meth) acrylate,
Trifunctional (meth) acrylates such as tris- (2-hydroxyethyl) -isocyanuric acid ester (meth) acrylate, other pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate. Examples include tetrafunctional or higher functional (meth) acrylates such as acrylates, and acrylic urethane oligomers having a urethane bond in the molecule.

The urethane oligomer having a (meth) acryloyl group in the molecule is obtained by, for example, reacting a compound having two or more isocyanate groups in one molecule with a (meth) acrylate having active hydrogen. To be

Examples of the compound having two or more isocyanates in one molecule include m-phenylene diisocyanate, p-phenylene diisocyanate, toluene-2,4-diisocyanate and toluene-2,6.
-Diisocyanate, toluene-2,5-diisocyanate, toluene-3,5-diisocyanate, m-xylylene diisocyanate, p-xylylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, isophorone diisocyanate, 4,4'-diphenylmethane diisocyanate , 4,4'-diisocyanate-3,3'-dimethylbiphenyl, 4,4'-diisocyanate-3,3 '
-Dimethylbiphenylmethane and the like.

Examples of the active hydrogen-containing (meth) acrylate include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, glycerin di (meth) acrylate, and 1,6-bis (3-). Examples thereof include acryloxy-2-hydroxypropyl) -hexyl ether, pentaerythritol tri (meth) acrylate, (meth) acrylic acid and the like. Is mentioned.

The above-mentioned photopolymerization initiator may be a (meth) acrylate by irradiation with actinic rays such as visible rays and ultraviolet rays.
As long as it initiates the polymerization of the compound, for example, sodium methyldithiocarbamate sulfide,
Sulfides such as diphenyl monosulfide, dibenzothiazoyl monosulfide and disulfide;
Thioxanthone derivatives such as thioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone and 2,4-diethylthioxanthone; azo compounds such as hydrazone and azobisisobutyronitrile; benzenediazonium salts; benzoin, benzoin methyl ether, benzoin ethyl ether, Aromatic carbonyl compounds such as benzophenone, dimethylaminobenzophenone, Michler's ketone, benzylanthraquinone, t-butylanthraquinone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-aminoanthraquinone, 2-chloroanthraquinone; methyl p-dimethylaminobenzoate, Dialkylamis such as ethyl p-dimethylaminobenzoate, butyl p-dimethylaminobenzoate and isopropyl p-diethylaminobenzoate. Benzoates; benzoyl peroxide, di-t- butyl peroxide, dicumyl peroxide, peroxides such as cumene hydroperoxide; 9-phenyl acridine, 9-p-methoxyphenyl acridine, 9-acetylamino acridine,
Acridine derivatives such as benzacridine; phenazine derivatives such as 9,10-dimethylbenzphenazine, 9-methylbenzphenazine, 10-methoxybenzphenazine; 4,4 ′, 4 ″ -trimethoxy-2,3-diphenylquinoxaline and the like. Quinoxaline derivative; 2,4
5-triphenylimidazoyl dimer, 2-nitrofluorene, 2,4,6-tris (trichloromethyl)-
1,3,5-triazine, 3,3′-carbonylbiscoumarin, thiomichler ketone and the like can be mentioned, and they may be used alone or in combination of two or more kinds.

An amine compound may be added to the above-mentioned photopolymerizable resin in order to prevent a decrease in photosensitivity due to oxygen. Such an amine may be any one having a low volatility, for example, Aliphatic amines such as triethanolamine and methyldiethanolamine; aromatic amines such as dialkylaminobenzoic acid esters and Michler's ketone.

If the amount of the above-mentioned photopolymerization initiator added is small, the polymerization rate becomes slow and it takes a long time to cure, or the curing becomes insufficient and a conductive layer having high hardness and excellent scratch resistance cannot be obtained. If so, heat resistance and weather resistance of the conductive layer are deteriorated, and coloring and whitening occur. Therefore, 0.01 to 20 parts by weight is preferable with respect to 100 parts by weight of the (meth) acrylate compound, and particularly preferably 0. 1 to 10 parts by weight.

The conductive powder may be, for example, SnO.
₂ , In ₂ O ₃ , ZnO, CdSnO ₄ , Sb ₂ O ₃ ,
Examples thereof include fine particle metal oxides such as Al ₂ O ₃ and TiO ₂ , and fine particle BaSO ₄ which is coated with metal oxide on the surface to be conductive, mica, glass fiber, ceramic whiskers and the like.

As the above-mentioned particulate metal oxide, SnO
A metal oxide containing ₂ as a main component is preferable, and SnO ₂ containing 0.1 to 20 wt% of antimony is particularly preferably used.

The average particle size of the above-mentioned conductive powder is 3 μm or less, because when it becomes large, visible rays are scattered and the transparency of the obtained conductive layer decreases.

When the amount of the above-mentioned conductive powder added is small, the conductivity of the obtained conductive layer is lowered and the antistatic effect is insufficient, and when it is increased, the transparency of the conductive layer is lowered and abrasion resistance and scratches are caused. Since mechanical properties such as properties are deteriorated, it is 20 to 1000 parts by weight with respect to 100 parts by weight of the transparent resin binder.

To form the conductive layer used in the present invention, for example, a transparent resin binder other than the photopolymerizable resin and the conductive powder are dissolved and mixed in an organic solvent to prepare a coating liquid for the conductive layer. .

The organic solvent is the transparent resin binder.
As long as it does not swell or dissolve the transparent resin film or sheet having the surface layer provided therein, such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, ethylene glycol monomethyl ether (methyl cellosolve), ethylene glycol monoethyl ether. (Ethyl cellosolve), butyl acetate, isopropyl alcohol, acetone, anisole and the like can be mentioned.

The composition of the conductive layer is as described above,
If necessary, in order to improve the dispersion of the conductive powder in the transparent resin binder, the coating liquid contains sodium phosphate, sodium sulfonate, sodium oleate,
Surfactants such as sodium citrate, silane compounds such as alkylsilanes and alkoxysilanes, titanate coupling agents such as alkyl titanates and acrylic titanates, etc. may be added to such an extent that the transparency of the conductive layer is not impaired. .

In addition, various known additives such as a leveling agent, a surface modifier and a defoaming agent may be added to the coating liquid for the conductive layer.

As a method for producing the coating liquid for the conductive layer, a known method is used. For example, an organic solvent is added to a transparent resin binder to dissolve it, and then conductive powder and additives are added. Examples thereof include a method of mixing and dispersing using a sand mill, a ball mill, an attritor, a high speed rotary stirring device, a triple roll, or the like.

As a method for forming the conductive layer along the surface of the transparent resin film or the sheet having fine irregularities using the coating solution for the conductive layer, a known method is used.
Examples thereof include a spray method, a bar coating method, a doctor blade method, a roll coating method, a spin coating method, a dipping method, and the like, and a method of removing an organic solvent by drying. A dipping method that can be applied uniformly along the surface is preferably used.

In order to form a conductive layer on the transparent resin binder by using the above-mentioned photopolymerizable resin, a publicly known method such as photopolymerization can be used in the same manner as the method for producing a coating liquid for the above conductive layer. After adding an organic solvent to the conductive resin and dissolving it, conductive powder,
Additives are mixed and dispersed using a sand mill, a ball mill, an attritor, a high-speed rotary stirring device, a three-roll mill, etc. to produce a coating liquid for the conductive layer.

Then, using the obtained coating liquid, a light diffusion film or a screen is formed by a known method such as a spray method, a bar coating method, a doctor blade method, a roll coating method, a spin coating method or a dipping method. -Coating along the surface having fine irregularities, heating to remove the organic solvent to form a coating film, and exposure and curing to form a conductive layer.

The above-mentioned coating is particularly preferably carried out by a dipping method capable of uniformly coating along the surface having fine irregularities.

As a light source for the above exposure, ultraviolet rays,
It may be any as long as it can generate active light such as visible light that initiates the polymerization of a photopolymerizable resin, and examples thereof include a halogen lamp, a metal halogen lamp, a xenon lamp, a (super) high pressure mercury lamp, and a mercury xenon lamp. The irradiation amount is preferably 50 to 5000 mJ / cm ² .

When the thickness of the conductive layer is thin, sufficient conductivity cannot be obtained, and when the thickness is thick, fine irregularities of the light diffusing film or the sheet are filled, and the light diffusing function is deteriorated. preferable.

Since the conductive layer contains conductive powder, extremely fine irregularities are formed on the surface layer. These irregularities enhance the light diffusion effect, but such irregularities are generally used as needed. It is preferable that the light diffusing plate is smoothed by a buffing process using a different polishing machine.

[0039]

EXAMPLES Next, examples of the present invention will be described. In the following, "parts" means "parts by weight".

(Example 1) (1) Production of coating liquid for conductive layer Vinyl chloride / vinyl acetate copolymer (weight ratio 9: 1) 40
Parts were dissolved in 460 parts of a mixed solvent of methyl cellosolve and methyl ethyl ketone (weight ratio 4: 1), and an attritor was used to
100 parts of SbO ₂ -containing SnO ₂ powder (trade name: T-1 manufactured by Mitsubishi Materials) having an average particle size of 0.02 μm was mixed and dispersed for 10 hours to produce a coating liquid for a conductive layer. (2) Formation of Conductive Layer A transparent resin sheet made of polycarbonate having a pitch of 350 μm and a depth of 220 μm on one surface and a prism-shaped cross section is dipped in the above-mentioned conductive layer coating solution and pulled up at room temperature. For 30 minutes, and then hot air drying at 50 ° C. for 10 minutes to form a conductive layer, thereby manufacturing a light diffusion plate.

(Embodiment 2) The conductive layer of the light diffusing plate manufactured in the same manner as in Embodiment 1 is used with a polisher made of wool for 300 times.
Polished under the condition of 0 RPM.

(Example 3) Polymethylmethacrylic acid 20
Parts are methyl cellosolve and cyclohexanone (weight ratio 9:
Dissolved in 400 parts of the mixed solvent of 1), average particle size 0.02μ
100 parts by weight of antimony (Sb) -containing SnO ₂ powder (manufactured by Mitsubishi Materials, trade name; T-1) was added, and mixed and dispersed for 10 hours with an attritor to prepare a coating liquid for the conductive layer.

A light diffusing plate was manufactured in the same manner as in Example 1 except that the coating liquid for the conductive layer in Example 1 was changed to that obtained in Example 3. (Example 4) The surface of a light diffusing plate manufactured in the same manner as in Example 3 was polished in the same manner as in Example 2.

Example 5 In 500 parts of methyl cellosolve were dissolved 50 parts of pentaerythritol triacrylate, 0.2 part of hydroquinone, 2 parts of thioxanthone, 2 parts of ethyl p-dimethylaminobenzoate and 15 parts of acrylic acid,
Charge into an attritor and, while stirring, add 100 parts of antimony (Sb) -containing SnO ₂ powder (manufactured by Mitsubishi Materials, trade name; T-1) having an average particle diameter of 0.02 μm, and mix and disperse for 10 hours. A coating liquid for the conductive layer was produced.

As in the first embodiment, the pitch is 350 μ on one side.
m, a depth of 220 .mu.m, a polycarbonate light diffusion sheet having a prism-shaped recess in the cross section, was dipped in the above coating solution for the conductive layer, pulled up, dried at room temperature for 30 minutes, and further at 50.degree. It was dried with hot air for 10 minutes, and then was irradiated with ultraviolet rays by a high-pressure mercury lamp so that the irradiation amount was 1800 mJ / cm ² , and cured to manufacture a light diffusion plate.

(Example 6) A light diffusing plate obtained in the same manner as in Example 5 was subjected to 3000R using a wool polisher.
The surface was polished under PM conditions.

Example 7 500 parts of methyl cellosolve,
45 parts of pentaerythritol triacrylate, 0.2 part of hydroquinone, 2 parts of thioxanthone, 2 parts of ethyl p-dimethylaminobenzoate, 5 parts of bis (2-methacryloyloxyethyl) acid phosphate were dissolved in 50 parts of cyclohexanone, and dissolved in an attritor. I prepared it. While stirring this, Sb-containing Sn having an average particle size of 0.02 μm
O ₂ powder (manufactured by Mitsubishi Materials, trade name; T-1) 100
Parts, vinyl alcohol component 35 mol%, average degree of polymerization 24
A conductive paint was produced by adding 11 parts of acetoacetal resin No. 00 and dispersing for 10 hours.

A pitch of 350 μ is provided on one surface as in the first embodiment.
m, a depth of 220 .mu.m, a polycarbonate light diffusion sheet having a prism-shaped recess in the cross section, was dipped in the above coating solution for the conductive layer, pulled up, dried at room temperature for 30 minutes, and further at 50.degree. It was dried with hot air for 10 minutes, and then was irradiated with ultraviolet rays by a high-pressure mercury lamp so that the irradiation amount was 1800 mJ / cm ² , and cured to manufacture a light diffusion plate.

(Embodiment 8) A light diffusing plate obtained in the same manner as in Embodiment 7 is subjected to 3000R using a wool polisher.
The surface was polished under PM conditions.

Example 9 A conductive layer coating solution was prepared in the same manner as in Example 5, except that 50 parts of pentaerythritol triacrylate of Example 5 was changed to 30 parts of dipentaerythritol hexaacrylate.

A pitch of 350 μ is provided on one surface as in the first embodiment.
m, a depth of 220 .mu.m, a polycarbonate light diffusion sheet having a prism-shaped recess in the cross section, was dipped in the above coating solution for the conductive layer, pulled up, dried at room temperature for 30 minutes, and further at 50.degree. It was dried with hot air for 10 minutes, and then was irradiated with ultraviolet rays by a high-pressure mercury lamp so that the irradiation amount was 1800 mJ / cm ² , and cured to manufacture a light diffusion plate.

(Embodiment 10) The light diffusing plate obtained in the same manner as in Embodiment 9 is 3,000 using a wool polisher.
The surface was polished under the RPM condition.

(Comparative Example 1) A conductive layer is not provided on a polycarbonate light diffusion sheet having a concave portion having a pitch of 350 μm, a depth of 220 μm and a prism-shaped cross section on one surface as in the case of Example 1. I used one.

With respect to the light diffusing plates obtained in Examples 1 to 10 and the transparent resin sheet of Comparative Example 1, the surface hardness and the front luminance, the measurement of surface specific resistance and the dust resistance were evaluated, and the results are shown in the table. Shown in 1.

[0055]

[Table 1]

The test method is as follows. (1) Measurement of surface hardness The surface hardness was measured by the JIS K-5400 pencil hardness test method.

(2) Measurement of front luminance On the light guide plate of the backlight module for a liquid crystal display panel in which one cold cathode tube is installed at the end, a light diffusing plate is used as a cold cathode tube in the direction of the groove-shaped recess. They were placed parallel to each other, a luminance meter (trade name; LS-100, manufactured by Minolta) was installed at a distance of 30 cm, and the front luminance was measured.

(3) Measurement of surface resistivity It was measured according to ASTM-D257.

(4) Dust resistance The conductive layer of the light diffusing plate was rubbed with a cloth, and a piece to which a fine piece of paper adhered was marked with X, and a piece without sticking to paper was marked with ◯.

[0060]

The light diffusing plate of the present invention is a film or sheet of highly transparent polymethylmethacrylate, polycarbonate, or polyvinyl chloride having a large number of fine irregularities on at least one side. Since a conductive layer having a thickness of 0.5 to 50 μm is provided along the surface having, it is difficult for dust and dirt to adhere.

Since a conductive layer composed of a (meth) acrylate compound, a photopolymerization initiator, and a conductive powder having an average particle size of 3 μm or less is provided, the surface hardness is high and the conductivity is high. Has excellent scratch resistance and does not easily adhere to dust.

Therefore, the light diffusing plate of the present invention is a display,
In particular, it can be preferably used for a lighting cover and the like, and can be used for a liquid crystal display, a transmission screen, a cover of a lighting device, and the like.

Claims (2)

[Claims] 1. A transparent resin binder or 100 parts by weight of a transparent resin film or sheet and an average of at least one surface of the transparent resin film or sheet are provided on the uneven surface of the sheet. A light diffusing plate provided with a conductive layer comprising 20 to 1000 parts by weight of conductive powder containing a metal oxide having a particle diameter of 3 μm or less as a main component. 2. A light diffusing plate, wherein the transparent resin binder according to claim 1 is made of a photopolymerizable resin.