KR101759741B1 - Light guide sheet - Google Patents

Abstract

(assignment)
And is excellent in light transmittance, workability, and handling characteristics.
(Solution)
An acrylic resin layer, and a polycarbonate resin layer laminated on both sides of the acrylic resin layer. Wherein the acrylic resin layer is an acrylic resin containing 0.001 to 1 part by weight of at least one member selected from the group consisting of a malonic acid ester-based ultraviolet absorber, a oxalanilide-based ultraviolet absorber, and an acetic ester- Composition. The polycarbonate resin layer is preferably composed of a polycarbonate resin composition containing 0.01 to 1 part by weight of an acrylic resin with respect to 100 parts by weight of the polycarbonate resin.

Description

Light guide plate {LIGHT GUIDE SHEET}

The present invention relates to a light guide plate comprising an acrylic resin layer and a polycarbonate resin layer laminated on both sides thereof.

BACKGROUND ART Conventionally, a methyl methacrylate resin having excellent transparency has been widely used as a light guide plate. The methyl methacrylate resin can transmit light from a light source such as a cold cathode tube or an LED at a high transmittance. Therefore, a plate made of a methyl methacrylate resin having a thickness of about 3 to 5 mm is used as a light guide plate of a backlight such as a notebook PC and a liquid crystal monitor.

On the other hand, a light guide plate used for a mobile phone, a portable game machine, etc. is thinned to a thickness of about 1 to 2 mm, and not only a methyl methacrylate resin but also a polycarbonate resin having high strength or an ethylenically unsaturated monomer Resin is also used.

The tendency of thinning has been remarkable in recent years, and a light guide plate having a thickness of less than 1 mm is demanded in applications such as cellular phones and portable game machines. The light guide plate is often formed by injection molding, but such a thin light guide plate is difficult to injection mold. In addition, even in a notebook PC or a liquid crystal monitor in which a methacrylate-based resin has been widely used, it is necessary to form a relatively large screen thinly, making it difficult to cope with the conventional injection molding. The base resin has a characteristic of being easily cracked, and if it is thin, it becomes difficult in handling.

In order to cope with such a problem, a technique of using a film obtained by extruding a polycarbonate resin or an acrylic resin as a light guide plate and a technique of using a film in which rubber particles are dispersed in methacrylic resin as a light guide plate have been considered For example, Patent Document 1).

However, when a thin film obtained by extruding a polycarbonate resin is applied to a light guide plate, the polycarbonate resin tends to have insufficient light transmittance because the light emitted from the light source passes through a long optical path there was. This tendency becomes conspicuous when the area of the light guide plate is large. In addition, when a thin film obtained by extrusion molding an acrylic resin is applied to a light guide plate, cracks tend to be generated in the light guide plate when shaping the light guide plate obtained by punching or the like, and the handling characteristics of the resulting light guide plate are insufficient .

On the other hand, when a thin film obtained by dispersing rubber particles in a methacrylic resin is applied to a light guide plate, workability and handling characteristics by punching are good, but light transmittance is insufficient.

Japanese Patent Application Laid-Open No. 2008-218207

A problem to be solved by the present invention is to provide a light guide plate excellent in light transmittance, processability, and handling characteristics.

(1) A light guide plate comprising an acrylic resin layer and a polycarbonate resin layer laminated on both sides of the acrylic resin layer.

(2) The acrylic resin composition according to any one of (1) to (3), wherein the acrylic resin layer contains at least one kind of agent selected from the group consisting of malonic acid ester-based ultraviolet absorber, oxalanilide-based ultraviolet absorber and acetic ester- The light guide plate according to the above (1), wherein the light guide plate is made of an acrylic resin composition containing a weight part.

(3) The light guide plate according to (1) or (2), wherein the polycarbonate resin layer comprises a polycarbonate resin composition containing 0.01 to 1 part by weight of an acrylic resin per 100 parts by weight of the polycarbonate resin.

The light guide plate of the above (1) is excellent in light transmittance in a long optical path and is not easily cracked, so that it is excellent in workability and handling characteristics. Therefore, the light guide plate of the above (1) can be suitably used as a light guide plate such as a backlight of liquid crystal even when the thickness is thin.

In the light guide plate of (2), the acrylic resin layer contains a specific ultraviolet absorber at a specific ratio, so that the light resistance is high.

In the light guide plate of (3), since the polycarbonate resin layer contains an acrylic resin in a specific ratio, the adhesion of the polycarbonate resin layer to the acrylic resin layer is high.

1 is a schematic explanatory view showing a manufacturing method of a light guide plate according to an embodiment of the present invention.
2 is a schematic cross-sectional explanatory view showing a metal roll and an elastic roll according to an embodiment of the present invention.
3 is a schematic cross-sectional explanatory view showing an elastic roll according to another embodiment of the present invention.

The light guide plate of the present invention comprises an acrylic resin layer and a polycarbonate resin layer laminated on both sides of the acrylic resin layer.

The acrylic resin layer is a resin layer containing an acrylic resin as a main component.

The acrylic resin layer may be a layer made of only the acrylic resin, and preferably a layer made of an acrylic resin composition containing the acrylic resin.

As the acrylic resin constituting the acrylic resin layer, methacrylic resin is generally used. The methacrylic resin may be a methyl methacrylate homopolymer of 100% by weight of a methyl methacrylate unit, or may be a copolymer of methyl methacrylate and at least one other monomer capable of copolymerizing with methyl methacrylate . Among them, a resin containing a methyl methacrylate unit as a main component is preferable. Specifically, it is preferably a methyl methacrylate resin containing 50% by weight or more of methyl methacrylate units, and the methyl methacrylate unit is preferably 70 More preferably a methyl methacrylate resin containing at least% by weight.

Examples of the other monomer copolymerizable with the methyl methacrylate include ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethyl methacrylate Methacrylic acid esters other than methyl methacrylate such as hexyl and 2-hydroxyethyl methacrylate, methacrylic acid esters such as methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate And acrylate esters such as 2-hydroxyethyl. Further, styrene and substituted styrenes such as halogenated styrenes such as chlorostyrene and bromostyrene, alkylstyrenes such as vinyltoluene and? -Methylstyrene, and the like can be mentioned. Further, unsaturated acids such as methacrylic acid and acrylic acid, acrylonitrile, methacrylonitrile, maleic anhydride, phenylmaleimide, cyclohexylmaleimide and the like are also exemplified.

It is preferable that the acrylic resin composition contains at least one ultraviolet absorber in order to increase the light resistance of the light guide plate. The content of the ultraviolet absorber is preferably 0.001 to 1 part by weight, more preferably 0.005 to 0.5 part by weight, still more preferably 0.005 to 0.1 part by weight, based on 100 parts by weight of the acrylic resin. If the content of the ultraviolet absorber is too small, the resulting light guide plate may have insufficient light resistance to ultraviolet rays generated from the light source, and if the content of the ultraviolet absorber is too large, such a cost is increased.

As the ultraviolet absorber, an ultraviolet absorber having a maximum absorption wavelength in the range of 250 to 320 nm is preferable, and a maximum absorption wavelength (hereinafter also referred to as "? _Max " The ultraviolet absorbent having the maximum absorption wavelength can improve the light resistance of the light guide plate and can inhibit the coloring of the light guide plate due to the absorption of visible light of the ultraviolet absorbent and the coloring of the light emitted from the light guide plate. The ultraviolet absorber is preferably an ultraviolet absorber having a molar absorptivity (hereinafter sometimes referred to as "? _Max ") at a maximum absorption wavelength of 10000 mol ^-1 cm ^-1 or more, particularly 15000 mol ^-1 cm ^-1 or more An ultraviolet absorber having a molecular weight (hereinafter sometimes referred to as " Mw ") of 400 or less is preferable from the viewpoint of reducing the weight used.

Examples of the ultraviolet absorber include benzophenone ultraviolet absorbers, cyanoacrylate ultraviolet absorbers, salicylate ultraviolet absorbers, nickel complex salt ultraviolet absorbers, benzoate ultraviolet absorbers, benzotriazole ultraviolet absorbers, horse A phosphoric acid ester-based ultraviolet absorber, an oxalanilide-based ultraviolet absorber, and an acetic acid ester-based ultraviolet absorber. Among them, a benzophenone-based ultraviolet absorber, a benzotriazole-based ultraviolet absorber, a malonic ester-based ultraviolet absorber, a oxalanilide-based ultraviolet absorber and an acetic acid ester-based ultraviolet absorber are preferable, and a malonic ester- , The acetic acid ester-based ultraviolet absorber can improve the light resistance of the light guide plate and suppress the coloring of the light guide plate and the outgoing light due to the absorption of visible light by the ultraviolet absorber.

Examples of the benzophenone-based ultraviolet absorber include 2,4-dihydroxybenzophenone (Mw: 214, λ _max : 288 nm, ε _max : 14100 mol ^-1 cm ^-1 ) methoxybenzophenone _{(Mw: 228, λ max:} 289 ㎚, ε max: 14700 ㏖ -1 ㎝ -1), 2- hydroxy-4-methoxybenzophenone-5-sulfonic acid (Mw: 308, λ _{max: 292 ㎚, ε max: 12500 ㏖} -1 ㎝ -1), 2- hydroxy-4-octyloxy-benzophenone _{(Mw: 326, λ max:} 291 ㎚, ε max: 15300 ㏖ -1 ㎝ -1), 4 -Dodecyloxy-2-hydroxybenzophenone (Mw: 383,? _Max : 290 nm,? _Max : 16200 mol ^-1 cm ^-1 ), 4-benzyloxy-2-hydroxybenzophenone ? _max : 289 nm,? _max : 15900 mol ^-1 cm ^-1 ), 2,2'-dihydroxy-4,4'-dimethoxybenzophenone (Mw: 274,? _max : 289 nm,? _max : 11800 ㏖ ^-1 ㎝ ^-1), 1,6- bis (4-benzoyl-3-hydroxyphenoxy) -pentanoic _{(Mw: 511, λ max:} 290 ㎚, ε max: 30100 ㏖ -1 ㎝ -1) , 4-benzoyl-3-hydroxyphenoxy) -butane (Mw: 483,? _Max : 290 nm,? _Max : 28500 ㏖ ^-1 cm ^-1 ).

Examples of the cyanoacrylate ultraviolet absorber include ethyl 2-cyano-3,3-diphenylacrylate (Mw: 277, λ _max : 305 nm, ε _max : 15600 mol ^-1 cm ^-1 ) 2-ethylhexyl 2-cyano-3,3-diphenylacrylate (Mw: 362,? _Max : 307 nm,? _Max : 14400 mol ^-1 cm ^-1 ).

Examples of the salicylate-based ultraviolet absorber include phenyl salicylate (Mw: 214, λ _max : 312 nm, ε _max : 5000 mol ^-1 cm ^-1 ), 4-tert-butylphenyl salicylate : 270,? _Max : 312 nm,? _Max : 5400 mol ^-1 cm ^-1 ).

Examples of the nickel complex salt ultraviolet absorber include (2,2'-thiobis (4-tert-octylphenolate)) -2-ethylhexylamine nickel (II) (Mw: 629, λ _max : 298 nm,竜_max : 6600 mol ^-1 cm ^-1 ).

Benzoate-based ultraviolet absorbers include, for example, 2 ', 4'-di -tert- butylphenyl-3,5-di -tert- butyl-4-hydroxybenzoate _{(Mw: 436, λ max:} 267 ㎚ ,? _max : 20200 mol ^-1 cm ^-1 ).

As the benzotriazole-based ultraviolet absorber, for example, 2- (2-hydroxy-5-methylphenyl) -2H-benzotriazole (Mw: 225, λ _max : 300 nm, ε _max : 13800 mol ^-1 cm ^-1 ), 5-chloro-2- (3,5-di -tert- butyl-2-hydroxyphenyl) -2H- benzotriazole _{(Mw: 358, λ max:} 312 ㎚, ε max: 14600 ㏖ -1 ㎝ ^-1), 2- (3-tert- butyl-2-hydroxy-5-methylphenyl) -5-chloro -2H- benzotriazole _{(Mw: 316, λ max:} 354 ㎚, ε max: 14300 ㏖ -1 ㎝ ^-1), 2- (3,5- di -tert- pentyl-2-hydroxyphenyl) -2H- benzotriazole _{(Mw: 352, λ max:} 305 ㎚, ε max: 15200 ㏖ -1 ㎝ - ^1), 2- (3,5-di -tert- butyl-2-hydroxyphenyl) -2H- benzotriazole _{(Mw: 323, λ max:} 303 ㎚, ε max: 15600 ㏖ -1 ㎝ -1) (Mw: 388,? _Max : 304 nm,? (?), _max : 14100 mol ^-1 cm ^-1 ), 2- (2-hydroxy-5-tert-octylphenyl) -2H-benzotriazole (Mw: 323, λ _max : 301 nm, ε _max : 14700 mol ^-1 Cm ^-1 ) And the like.

As the malonic acid ester-based ultraviolet absorber, 2- (1-arylalkylidene) malonic acid esters, particularly compounds represented by the following general formula (1), are preferably used.

[Chemical Formula 1]

(Wherein X ¹ represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms, and R ¹ and R ² are the same or different and each represents an alkyl group having 1 to 6 carbon atoms)

In the general formula (1), the alkyl group represented by X ¹ and the alkyl group represented by X ¹ in the alkoxy group may be linear or branched and branched, for example, methyl, ethyl, n-propyl, isopropyl An n-butyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group. X ¹ is preferably a hydrogen atom, an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms, and the substitution position of X ¹ is preferably a para position.

In the general formula (1), the alkyl groups represented by R ¹ and R ² may be linear or branched, and examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, An isobutyl group, a sec-butyl group, and a tert-butyl group. R ¹ and R ² are each preferably an alkyl group having 1 to 4 carbon atoms.

As the compound represented by the general formula (1), dimethyl 2- (paramethoxybenzylidene) malonate (Mw: 250, λ _max : 308 nm, ε _max : 24200 mol ^-1 cm ^-1 ) .

As the oxalanilide-based ultraviolet absorber, alkoxyoxanilides, particularly compounds represented by the following general formula (2), are preferably used.

(2)

(Wherein R ³ and R ⁴ are the same or different and each is an alkyl group having 1 to 6 carbon atoms)

In the general formula (2), the alkyl groups represented by R ³ and R ⁴ may be linear or branched, and examples thereof include a methyl group, ethyl group, n-propyl group, isopropyl group, An isobutyl group, a sec-butyl group, and a tert-butyl group. R ³ and R ⁴ are each preferably an alkyl group having 1 to 4 carbon atoms, and the substitution positions of R ³ and R ⁴ are each preferably ortho.

As the compound represented by the above general formula (2), 2-ethoxy-2'-ethyloxalanilide (Mw: 312, λ _max : 298 nm, ε _max : 16700 mol ^-1 cm ^-1 ) is particularly preferable.

As the acetate ester-based ultraviolet absorber, 2- (1-arylalkylidene) acetic acid esters, among which compounds represented by the following general formula (3), are preferably used.

(3)

(Wherein X ² represents a hydrogen atom, an alkyl group or an alkoxyl group, and R ⁵ represents an alkyl group)

The alkoxyl group as the substituent X ² may be linear or branched and may be branched, for example, methoxy, ethoxy, n-propoxy, isopropoxy, n- An alkoxyl group having about 1 to 6 carbon atoms such as a butoxy group, a tert-butoxy group, and an n-pentoxy group, and is preferably an alkoxyl group having about 1 to 4 carbon atoms. The alkyl group may be linear or branched and may be branched, for example, a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec- - pentyl group, n-hexyl group, and the like, preferably an alkyl group having about 1 to 4 carbon atoms, and more preferably a methoxy group. The substituent X ² is preferably an alkoxyl group.

The alkyl group as the substituent R ⁵ is usually an alkyl group having about 1 to 10 carbon atoms, and examples thereof include a methyl group, an ethyl group, a n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, An n-pentyl group, a 1-methylpentyl group, a 1-ethylpentyl group, a 1-ethylhexyl group, an isobutyl group, An alkyl group having about 1 to 10 carbon atoms such as a methylhexyl group and a 2-ethylhexyl group, and the like, preferably a methyl group, a 2-ethylhexyl group and the like.

The acrylic resin composition preferably contains a compound having at least one kind of hindered amines, especially a 2,2,6,6-tetraalkylpiperidine skeleton, in order to further improve the light resistance. The content of the hindered amines is usually not more than 2 times by weight, preferably from 0.01 to 1 time by weight, of the ultraviolet absorber contained in the acrylic resin layer.

Examples of the hindered amines include polycondensates of dimethyl succinate / 1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine, poly ((6- , 1,3,3-tetramethylbutyl) imino-1,3,5-triazine-2,4-diyl) ((2,2,6,6-tetramethyl-4-piperidyl) imino ), Hexamethylene ((2,2,6,6-tetramethyl-4-piperidyl) imino), 2- (2,3-di-tert- butyl-4-hydroxybenzyl) -2- -Butylmalonic acid bis (1,2,2,6,6-pentamethyl-4-piperidyl), 2- (3,5-di-tert- Butylmalonic acid bis (1,2,2,6,6-pentamethyl-4-piperidyl), N, N'-bis (3-aminopropyl) ethylenediamine / 2,4- (1,2,2,6,6-pentamethyl-4-piperidyl) amino) -6-chloro-1,3,5-triazine condensate, bis (2,2,6,6- Tetramethyl-4-piperidyl sebacate, bis succinic acid (2,2,6,6-tetramethyl-4-piperidyl), and compounds represented by the following general formula (4).

[Chemical Formula 4]

(Wherein Y represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, a carboxyalkyl group having 2 to 20 carbon atoms, an alkoxyalkyl group having 2 to 25 carbon atoms, or an alkoxycarbonylalkyl group having 3 to 25 carbon atoms)

In the general formula (4), two alkyl groups (an alkyl group substituted with an alkyl group and an alkoxy group of an alkoxy group) in the alkyl group, a carboxyalkyl group and an alkoxyalkyl group represented by Y, and two alkyl groups Group and an alkyl group substituted with an alkoxycarbonyl group) may be linear or branched. Y is preferably a hydrogen atom or an alkoxycarbonylalkyl group having 5 to 24 carbon atoms, more preferably a hydrogen atom or an alkoxycarbonylethyl group. Examples of the alkoxycarbonylethyl group include a dodecyloxycarbonylethyl group, a tetradecyloxycarbonylethyl group, a hexadecyloxycarbonylethyl group, and an octadecyloxycarbonylethyl group.

The polycarbonate resin layer is a layer containing a polycarbonate resin as a main component.

The polycarbonate resin layer may be a layer made of only the polycarbonate resin, and is preferably a layer made of a polycarbonate resin composition containing the polycarbonate resin.

The polycarbonate resin constituting the polycarbonate resin layer is a polymer in which all of the bonding sites of the monomer units are composed of a carbonate group (-O- (C = O) -O-).

Examples of the polycarbonate resin include polycarbonate resins obtained by polymerizing a resin or a carbonate prepolymer obtained by reacting one or more divalent phenols with at least one carbonylating agent by an interfacial polycondensation method or a melt transesterification method by a solid- A resin obtained by polymerization of a cyclic carbonate compound by a ring-opening polymerization method, and the like.

Examples of the dihydric phenol include hydroquinone, resorcinol, 4,4'-dihydroxydiphenyl, bis (4-hydroxyphenyl) methane, bis { (4-hydroxyphenyl) ethane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 2,2- Propane (commonly known as bisphenol A), 2,2-bis {(4-hydroxy-3-methyl) phenyl} propane, 2,2- Bis {(3-isopropyl-4-hydroxy) phenyl} propane, 2,2-bis { (4-hydroxyphenyl) propane, 2,2-bis (4-hydroxyphenyl) butane, 2,2- Bis (4-hydroxyphenyl) pentane, 2,2-bis (4-hydroxyphenyl) Bis (4-hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) Phenyl) -4-isopropylcyclohexane, 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, 9,9- (4-hydroxyphenyl) -o-diisopropylbenzene,?,? '- bis (4-hydroxyphenyl) Diisopropylbenzene,?,? '-Bis (4-hydroxyphenyl) -p-diisopropylbenzene, 1,3-bis (4-hydroxyphenyl) There may be mentioned adamantane, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl sulfoxide, 4,4'-dihydroxydiphenyl sulfide, 4,4'- 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl ester, and the like.

Among them, bisphenol A, 2,2-bis {(4-hydroxy-3-methyl) phenyl} propane, 2,2- Phenyl) -3-methylbutane, 2,2-bis (4-hydroxyphenyl) -3,3-dimethylbutane, 2,2- Bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane and?,? '-Bis (4-hydroxyphenyl) -m-diisopropylbenzene. It is preferable to use bisphenol A alone, use of bisphenol A in combination with 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, use of bisphenol A and 2,2 Of at least one divalent phenol selected from the group consisting of bis (4-hydroxy-3-methyl) phenyl} propane and α, α'-bis (4-hydroxyphenyl) Combined use is more preferable.

Examples of the carbonylating agent include a carbonyl halide such as phosgene, a carbonate ester such as diphenyl carbonate, and a haloformate such as dihaloformate of divalent phenol.

The polycarbonate resin composition preferably contains an acrylic resin in order to improve adhesion with the acrylic resin layer. Specifically, it is preferable that the polycarbonate resin composition constituting the polycarbonate resin layer contains 0.01 to 1 part by weight of an acrylic resin with respect to 100 parts by weight of the polycarbonate resin. As the acrylic resin, the same acrylic resin as that used for the acrylic resin layer described above can be used. The acrylic resin contained in the polycarbonate resin composition preferably has a molecular weight in the range of 1,000 to 100,000. If the molecular weight is too low, the acrylic resin may volatilize during extrusion molding. If the molecular weight is excessively high, the acrylic resin may cause phase separation from the polycarbonate resin, which may lower the light transmittance of the light guide plate .

The composition of the one polycarbonate resin layer and the composition of the other polycarbonate resin layer among the polycarbonate layers laminated on both sides of the acrylic resin layer may be the same or different from each other. The acrylic resin composition and the polycarbonate resin composition may contain at least one additive such as a light stabilizer, an antioxidant, and a release agent within a range not to deteriorate the performance of the light guide plate to be obtained.

The light guide plate of the present invention is preferably formed by laminating a polycarbonate resin layer on both sides of an acrylic resin layer by coextrusion molding.

The light guide plate of the present invention is produced by laminating and integrating an acrylic resin layer and a polycarbonate resin layer by coextrusion molding. In this co-extrusion molding, the above-mentioned material of the acrylic resin layer and the material of the polycarbonate resin layer are melt-kneaded by using two or three single-screw or twin-screw extruders, And the like. Then, the laminated integrated sheet-like molten resin is cooled and solidified by using, for example, a roll unit to obtain the light guide plate of the present invention. Hereinafter, one embodiment of a method of manufacturing a light guide plate according to the present invention will be described in detail with reference to the drawings.

1 is a schematic explanatory view showing a manufacturing method of a light guide plate according to the embodiment. Fig. 2 is a schematic cross-sectional explanatory view showing the metal roll and the elastic roll according to the embodiment. Fig. First, as shown in Fig. 1, an acrylic resin and a polycarbonate resin are extruded from a die for co-extrusion molding 3 while being heated and melted and kneaded in separate extruders 1 and 2, respectively.

Next, the sheet-shaped molten resin 4 co-extruded from the die 3 is sandwiched between two cooling rolls 5 arranged in the substantially horizontal direction and cooled to obtain the light guide plate 11.

2, the cooling roll 5 is composed of a high-rigidity metal roll 6 and an elastic roll having a metal thin film 9 on the outer periphery thereof, that is, a metal elastic roll 7. At least one of the metal roll 6 and the metal elastic roll 7 is connected to a rotary drive means such as a motor, and both rolls are configured to rotate at a predetermined main speed.

The highly rigid metal roll 6 is a roll roll in which the sheet-like light guide plate 11 after being sandwiched between the metal roll 6 and the metal elastic roll 7 is wound. The metal roll 6 is not particularly limited, and a conventional metal roll which is conventionally used in extrusion molding can be employed. Specific examples include drilled rolls and spiral rolls. The surface state of the metal roll 6 may be, for example, a mirror surface, a shape, or irregularities.

The metal elastic roll 7 is provided with a shaft roll 8 formed so as to be freely rotatable in a substantially cylindrical shape and a cylindrical metal member 8 disposed so as to cover the outer peripheral surface of the shaft roll 8 and in contact with the molten resin 4 And a thin film 9. The fluid 10 is sealed between the shaft roll 8 and the metal thin film 9 so that the metal elastic roll 7 can exhibit elasticity. The shaft roll 8 is not particularly limited and is made of, for example, stainless steel.

The metal thin film 9 is made of, for example, stainless steel or the like, and preferably has a thickness of about 2 to 5 mm. The metal thin film 9 preferably has flexibility and flexibility, and is preferably a seamless structure having no welded joints. The metallic elastic roll 7 provided with the metallic thin film 9 is excellent in durability and can be handled in the same manner as a usual mirror roll when the metallic thin film 9 is mirror-finished, If a shape or unevenness is imparted, it is a roll that can transfer the shape, so that it is convenient to use.

The metallic thin film 9 is fixed at both end portions of the shaft roll 8 and the fluid 10 is enclosed between the shaft roll 8 and the metallic thin film 9. Examples of the fluid 10 include water, oil and the like. By controlling the temperature of the fluid 10, the temperature of the metal elastic roll 7 can be controlled. For the temperature control, for example, a known control method such as PID control or ON-OFF control may be employed. Instead of the fluid 10, a gas such as air may be used.

When the molten resin 4 is sandwiched between the metal roll 6 and the metal elastic roll 7 as described above, the metal elastic roll 7 is recessed along the outer peripheral surface of the metal roll 6 via the molten resin 4 And the metal elastic roll 7 and the metal roll 6 are brought into contact with each other through the molten resin 4 with a predetermined contact length L. [

The contact length L may be 1 to 20 mm, preferably 1 to 10 mm, and more preferably 1 to 7 mm. In order to set the contact length L to a predetermined value, it may be arbitrarily performed by adjusting the thickness of the metal thin film 9, the amount of enclosed fluid 10, and the like. The contact length L means a length of a straight line connecting a point where the metal elastic roll 7 and the metal roll 6 start to contact each other via the molten resin 4 and a point at which the contact ends .

When the metal elastic roll 7 and the metal roll 6 come into contact with each other via the molten resin 4 with the contact length L, the metal roll 6 and the metal elastic roll 7 are pressed against the molten resin 4, And the molten resin 4 sandwiched between these rolls is uniformly pressurized in the form of a face to form a film. When the film is formed in this way, the deformation can be prevented from remaining in the light guide plate 11, and the heat shrink property of the resulting light guide plate 11 tends to be reduced. Therefore, the light guide plate 11 has the effect of suppressing deformation such as warpage and undulation in use in a place where the temperature environment is strict.

Specifically, the shrinkage ratio S1 (%) in the extrusion direction and the shrinkage ratio S2 (%) in the width direction of the light guide plate 11 when the light guide plate 11 is left in a thermal atmosphere at 160 DEG C for 30 minutes are all 0 to 5% . When the shrinkage rates S1 and S2 are negative, that is, less than 0%, the light guide plate expands due to the heat of the light source and contacts the housing of the backlight when used as a light guide plate, so that the light guide plate itself is deformed, So that deformation also easily occurs. If the shrinkage rates S1 and S2 exceed 5%, the shrinkage of the light guide plate increases as the internal temperature rises due to lighting of the light source, and the shrinkage of the light guide plate may be accompanied by deformation, so that light leakage may occur from the light source portion, . The calculation method of the shrinkage rates S1 and S2 will be described later.

Tr

(Th+20 ℃), 바람직하게는 (Th-15 ℃)

Tr

(Th+10 ℃), 보다 바람직하게는 (Th-10 ℃)

Tr

(Th+5 ℃) 의 범위로 하는 것이 바람직하다.When the molten resin 4 is sandwiched and held between the metal roll 6 and the metal elastic roll 7 in order to reduce the heat shrinkage characteristics of the light guide plate 11, It is advisable to sandwich both rolls during the cooling and solidification process. Concretely, the surface temperature Tr of the metal roll 6 and the metal elastic roll 7 is set to (Th-20 占 폚) relative to the thermal deformation temperature Th of the acrylic resin or polycarbonate resin,

Tr

(Th + 20 占 폚), preferably (Th-15 占 폚)

Tr

(Th + 10 占 폚), more preferably (Th-10 占 폚)

Tr

(Th + 5 占 폚).

On the other hand, when the surface temperature Tr is lower than (Th-20 占 폚), the shrinkage rate S2 tends to decrease. Further, when the surface temperature Tr becomes higher than (Th + 20 deg. C), the shrinkage rate S1 tends to increase. In addition, there is a tendency that the peeling marks from the roll remain on the light guide plate to deteriorate the appearance.

The surface temperature Tr is based on a resin having a higher heat distortion temperature (Th) among the acrylic resin and polycarbonate resin. The heat distortion temperature (Th) is not particularly limited and is usually about 60 to 200 占 폚. The heat distortion temperature (Th) is a temperature measured in accordance with ASTM D-648.

After the sheet-like light guide plate 11 sandwiched between the metal roll 6 and the metal elastic roll 7 is wound around the metal roll 6, the sheet is taken on the transport roll while being cooled by a drawing roll , Whereby the light guide plate 11 is obtained.

Next, another embodiment of a manufacturing method of a light guide plate according to the present invention will be described. 3 is a schematic cross-sectional explanatory view showing the elastic roll according to the present embodiment. In Fig. 3, the same components as those in Figs. 1 and 2 are denoted by the same reference numerals, and a description thereof will be omitted.

As shown in Fig. 3, the metal elastic roll 15 according to the present embodiment has a structure in which the outer circumferential surface of the shaft roll 16 formed so as to be freely rotatable in a substantially columnar shape is covered with a metal thin film 17 Elastic roll.

The shaft roll 16 is, for example, a rubber roll made of rubber such as silicone rubber, whereby the elastic roll 15 can exhibit elasticity. The contact length L can be set to a predetermined value even by adjusting the hardness of the rubber.

The metal thin film 17 is made of, for example, stainless steel or the like, and its thickness is preferably about 0.2 to 1 mm.

In order to control the temperature of the metal elastic roll 15, for example, a backup cooling roll may be mounted on the metal elastic roll 15. The rest of the configuration is the same as that of the above-described embodiment, and a description thereof will be omitted.

The light guide plate of the present invention is in the form of a sheet and its thickness is usually 0.05 to 1 mm, preferably 0.1 to 0.8 mm, more preferably 0.2 to 0.7 mm. In the light guide plate of the present invention, the thickness of the acrylic resin layer is preferably 50% or more of the total thickness, more preferably 70% or more, and even more preferably 80% or more. As a result, the light transmission characteristics are improved. The thickness of the acrylic resin portion is usually 95% or less, preferably 90% or less, with respect to the total thickness.

When the workability of the light guide plate is emphasized, the thickness of the polycarbonate resin layer is preferably 10 占 퐉 or more, more preferably 10 to 50 占 퐉. The thickness of the one polycarbonate resin layer and the thickness of the other polycarbonate resin layer may be the same or different. The thickness of the light guide plate can be adjusted by the thickness of the molten resin 4 extruded from the die 3, the spacing of the two cooling rolls 5, and the like.

The light guide plate of the present invention thus obtained is excellent in light transmittance and excellent in workability and handling characteristics because it is not easily broken even when the thickness is thin. Therefore, it is used as a light guide plate for a backlight of a car navigation system, a portable information terminal, an operation panel of an industrial machine, a portable game machine, a notebook PC, a liquid crystal monitor, and a liquid crystal television. In particular, it is considered that the backlight is preferably used for a light guide plate having a size of 5 inches or more because the backlight is becoming thinner and larger.

The light guide plate of the present invention can be subjected to processes such as cutting by sawing, Thomson knife, etc., heating by bending or vacuum, press forming, end face polishing or the like. Further, the light guide plate of the present invention may be given a shape by, for example, dot printing, press molding, curable resin coating or the like.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited thereto. The configuration of the extrusion apparatus used in the following Examples and Comparative Examples is as follows.

Extruder 1: screw diameter 65 mm, uniaxial, with vent (manufactured by TOSHIBA MACHINERY CO., LTD.).

Extruder 2: screw diameter 45 mm, uniaxial, with vent (manufactured by Hitachi, Ltd.).

Feed block: Class 2 three-layer distribution (manufactured by Hitachi, Ltd.).

Die 3: T die, lip width 1400 mm, lip interval 1 mm (manufactured by Hitachi, Ltd.).

Roll: Two horizontal rolls, 1400 mm in surface length and 300 mm in diameter.

The extruders 1 and 2 and the die 3 were arranged as shown in Fig. 1, and the feed block was arranged at a predetermined position. Next, of the two cooling rolls, the roll closest to the extruder 1 and 2 was rolled once, and the roll was rolled twice, and each roll was constructed as follows.

<Roll configuration 1>

The roll configuration 1 shown in Fig. 2 was used. Specifically, rolls No. 1 and No. 2 were constructed as follows.

(Roll # 1)

The metallic thin film 9 was disposed so as to cover the outer peripheral surface of the shaft roll 8 and the metallic elastic roll 7 in which the fluid 10 was sealed between the shaft roll 8 and the metallic thin film 9 was rolled once . The shaft roll 8, the metal thin film 9 and the fluid 10 are as follows.

Axial roll (8): Stainless steel

Metal thin film (9): 2 mm thick stainless steel specular metal sleeve

Fluid (10): oil, temperature control of the oil enables temperature control of the metal elastic roll (7). More specifically, the oil is heated and cooled by the ON / OFF control of the temperature regulator so that the temperature can be controlled, and circulated between the shaft roll 8 and the metal thin film 9.

(Roll 2)

A stainless steel spiral roll having a specular surface is used as the high-rigidity metal roll 6, which is rolled twice.

The contact length L, in which the metal elastic roll 7 and the metal roll 6 are in contact with each other via the molten resin 4, is 4 mm.

<Roll configuration 2>

The rolls No. 1 and No. 2 were both made of a high-rigidity metal roll (a stainless steel spiral roll having a mirror-finished surface state).

Resins used in the following Examples and Comparative Examples are as follows.

Resin 1: 100 parts by weight of an aromatic polycarbonate ("Carrie 200-13" manufactured by Sumitomo DOW Co., Ltd.) was added 100 parts by weight of a methyl methacrylate resin ("DANAAL BR83" manufactured by Mitsubishi Rayon Co., Ltd.) Was added to the polycarbonate resin composition in an amount of 0.1 part by weight. The heat distortion temperature (Th) is 140 占 폚.

Resin 2: An acrylic resin composition obtained by adding 0.01 part by weight of a malonic acid ester-based ultraviolet absorber to 100 parts by weight of a copolymer of methyl methacrylate / methyl acrylate = 94/6 (weight ratio).

The heat distortion temperature (Th) is 100 deg. The malonic acid ester-based ultraviolet absorber is a compound represented by the general formula (1) wherein X ¹ is a methoxy group, its substitution position is a para position, and R ¹ and R ² are a methyl group compound. Dimethyl malonate (trade name "Sanduvor PR-25" manufactured by Clariant) was used.

[Examples 1 to 8 and Comparative Example 3]

&Lt; Preparation of light guide plate &

The resin of the kind shown in Table 1 as the resin layer A was melted and kneaded by the extruder 1 and supplied to the feed block. On the other hand, the resin of the kind shown in Table 1 as the resin layer B was melted and kneaded by the extruder 2 and supplied to the feed block. The resin layer A supplied from the extruder 1 to the feed block was an intermediate layer and the resin layer B supplied from the extruder 2 to the feed block was coextruded to be both surface layers.

The melted resin 4 extruded from the die 3 was formed into a film by sandwiching the rolls 1 and 2 in the roll configuration shown in Table 1 to obtain a light guide plate having a three-layer structure shown in Table 1. The surface temperature of the first roll was 130 캜, and the surface temperature of the second roll was 140 캜. These temperatures are values obtained by measuring the surface temperature of each roll. The "thickness" in the extruders 1 and 2 in Table 1 indicates the respective thicknesses of the resin layers A and B, and the "total thickness" indicates the total thickness of the obtained light guide plate.

[Comparative Examples 1 and 2]

The resin of the kind shown in Table 1 was melted and kneaded by the extruder 1, and fed in the order of the feed block and the die 3. The melted resin 4 extruded from the die 3 was formed while sandwiching the melted resin 4 in a roll 1 and a roll 2 of the roll configuration shown in Table 1 to obtain a light guide plate having a single layer structure shown in Table 1. [ In Comparative Example 1, the surface temperature of the No. 1 roll was 130 占 폚, and the surface temperature of the No. 2 roll was 140 占 폚. In Comparative Example 2, the surface temperature of the first roll was 100 占 폚, and the surface temperature of the second roll was 95 占 폚.

<Evaluation>

Each of the obtained light guide plates (Examples 1 to 8 and Comparative Examples 1 to 3) was subjected to shrinkage percentage, long optical path transmittance and cutter evaluation. The evaluation methods are shown below, and the results are also shown in Table 1.

(Shrinkage ratio)

First, test pieces were cut out from the obtained light guide plate in a size of 10 cm in length and width, and the dimension (MD0) in the extrusion direction and the dimension (TD0) in the width direction of the test piece were measured. Then, baby powder ("Sikarol High", manufactured by Wako Pure Chemical Industries, Ltd.) was placed on a metal bat, and the test piece was placed thereon and placed in an oven at 160 ° C for 30 minutes.

Thereafter, the dimensions (MD) and (TD) in the extrusion direction and the width direction (TD) of the naturally cooled test piece were measured and the obtained respective dimensions were expressed by the formula: shrinkage ratio S1 = {1- (MD / MD0) : Shrinkage ratio S2 = {1- (TD / TD0)} 100), shrinkage rates S1 and S2 were calculated. The ratio (S1 / S2) was calculated from the calculated shrinkage rates S1 and S2. In the shrinkage rates S1 and S2 in Table 1, the result of + indicates shrinkage and the result of - indicates expansion.

(Long optical path transmittance)

First, test pieces were cut out from the obtained light guide plate to a size of 10 cm x 4 cm, and the four sides of the test pieces were polished by using an edge grinder ("PB-500" manufactured by Megalotech Co., Ltd.). Then, the light transmittance of this test piece was measured at intervals of 5 nm on an optical path of 10 cm and a wavelength of 300 to 800 nm using a spectrophotometer ("U4000 type" manufactured by Hitachi, Ltd.) The average transmittance of 780 nm light was obtained, and this was regarded as a long optical path transmittance.

(Cutter evaluation)

The obtained light guide plate was cut with a cutter and visually observed for the occurrence of cracks. In addition, the following criteria were used as criteria.

?: No crack occurred.

X: Cracks occurred.

As is apparent from Table 1, the light guide plates of Examples 1 to 8 are excellent in light transmission characteristics in a long optical path and are not well divided. Particularly, the light guide plates of Examples 1, 3 to 6 and 8 employing the roll configuration 1 had a small shrinkage percentage.

On the other hand, the light guide plate of Comparative Example 1 having a single-layer structure of a polycarbonate resin layer and the light guide plate of Comparative Example 3 having an acrylic resin layer laminated on both sides of the polycarbonate resin layer all had inferior light transmission characteristics . In addition, the light guide plate of Comparative Example 2 having a single-layer structure of an acrylic resin layer showed a tendency to be easily cracked.

1, 2: extruder
3: Die
4:
5: Cooling roll
6: metal roll
7, 15: Metal elastic roll
8, 16: Axial roll
9, 17: metal thin film
10: Fluid
11:

Claims (3)

A light guide plate comprising an acrylic resin layer and a polycarbonate resin layer laminated by co-extrusion molding on both sides of the acrylic resin layer, wherein the thickness of the light guide plate is 0.1 to 0.8 mm and the thickness of the acrylic resin layer is A light guide plate having a thickness of 50% or more. The method according to claim 1,
Wherein the acrylic resin layer contains 0.001 to 1 part by weight of at least one agent selected from malonic acid ester-based ultraviolet absorbers, oxalanilide-based ultraviolet absorbers and acetic ester-based ultraviolet absorbers per 100 parts by weight of the acrylic resin The light guide plate being made of an acrylic resin composition. 3. The method according to claim 1 or 2,
Wherein the polycarbonate resin layer is made of a polycarbonate resin composition containing 0.01 to 1 part by weight of an acrylic resin per 100 parts by weight of the polycarbonate resin.

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