JP5117899B2 - Manufacturing method of composite light diffusion plate - Google Patents

Description

  The present invention relates to a composite light diffusion plate made of thermoplastic resin. More specifically, the present invention relates to a composite light diffusing plate made of a thermoplastic resin that has excellent surface light emission useful for a diffusion sheet of a liquid crystal display, etc., has high luminance, has little luminance unevenness on the light emitting surface, and has excellent color tone.

  Aromatic polycarbonate resins have excellent mechanical properties, heat resistance, and weather resistance, and are used in a wide range of applications as resins having high light transmittance. For example, it is also used in large quantities in the construction field such as skydomes, top lights, arcades, condominium waistboards, and road side walls.

  Many of these uses are used as white light diffusing plates. Conventional white light diffusing plates made of polycarbonate resin are a method in which a light diffusing agent such as calcium carbonate and titanium oxide is added to and mixed with polycarbonate resin (see Patent Document 1). ), A method of adding and mixing polymer fine particles partially cross-linked to a polycarbonate resin (see Patent Document 2), a method of mixing and adding infusible acrylic polymer fine particles, titanium oxide and a silicon compound to a polycarbonate resin (see Patent Document 3) ) Has been proposed.

  The light diffusing plate is used as a surface light source body of an edge light system or a direct backlight type of a liquid crystal display and a liquid crystal television, a surface light source body of a scanner, etc. as other applications. When the light diffusing plate described in 3 is used as the surface light source, the light transmittance is low and the optical loss is large, so that there is a problem that the luminance is low and sufficient surface light emission cannot be obtained.

  In recent years, the use of edge light type or direct backlight type liquid crystal displays and light diffusion plates for televisions has increased in screen size, and light diffusion plates made of polycarbonate and acrylic / styrene resin with high dimensional stability compete. ing. In particular, it is known that a polycarbonate light diffusing plate has excellent performance in terms of quality (impact resistance, heat resistance and flame retardancy).

  Large LCDs and TVs use many functional films such as diffusion films, lens films, and brightness enhancement films in addition to the light diffusion plate, from the viewpoint of improving the brightness of the liquid crystal screen and reducing the brightness unevenness of the entire screen. ing. However, in order to reduce costs and simplify the assembly process, there is a strong demand for the development of a light diffusing plate that does not deteriorate brightness and diffusion performance even if the number of functional films is reduced.

  As a polycarbonate resin composition as an edge light type surface light source body of a liquid crystal display, a resin composition in which calcium carbonate or a crosslinked polyacrylate resin is added to a polycarbonate resin (see Patent Document 4), a bead-like crosslinked acrylic resin in a polycarbonate resin There are known resin compositions (see Patent Document 5), and resin compositions (see Patent Document 6) in which a bead-like crosslinked acrylic resin and a fluorescent whitening agent are added to a polycarbonate resin. Furthermore, a light diffusing plate for a liquid crystal display backlight manufactured by forming a fine cross-sectional sawtooth convex shape on at least one surface of a light diffusing sheet containing a bead-like crosslinked acrylic resin is disclosed (see Patent Document 7).

  However, even in these polycarbonate resin compositions, the optical loss becomes large due to the addition of a large amount of additives such as a light diffusing agent, so that the brightness cannot be increased when used in a direct type backlight or scanner of a liquid crystal display. There was a problem.

  In addition, a diffusion film, a lens film, etc. are generally placed and used as needed for the light diffusion plate. In Patent Document 8, a resin extruded in multiple layers is sandwiched between rolls having a prism shape. An integrated composite diffuser plate has been proposed by pressing.

  However, such a light diffusing plate does not have sufficient luminance performance, and there is a problem that the influence becomes remarkable particularly when used as a light diffusing plate for a direct type backlight for a large-sized liquid crystal display described later.

JP 50-146646 A Japanese Patent Laid-Open No. 03-143950 JP-A-10-017761 Japanese Patent Laid-Open No. 05-257002 Japanese Patent Laid-Open No. 08-188709 Japanese Patent Laid-Open No. 09-020860 Japanese Patent Laid-Open No. 09-304606 Japanese Patent Laid-Open No. 08-313708

  An object of the present invention is to provide a light diffusing plate that has excellent surface light emission useful for a light diffusing plate of a direct-type backlight type liquid crystal display, etc., has high luminance, and has little luminance unevenness on the light emitting surface. In particular, it is to provide a light diffusing plate useful as a light diffusing plate of a direct backlight type for a large liquid crystal display or a large liquid crystal television.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventor has obtained a diffusive film on the surface in order to improve luminance and reduce luminance unevenness on the upper surface of a conventional light diffusion plate in a direct backlight system. It is used by arranging multiple sheets, but by comparing the adhesive layer with a surface roughness of a specific range on either side of the thermoplastic resin plate or functional film that is in contact with the adhesive layer, As a result, it was found that a composite diffusion plate having excellent color tone, high luminance, low luminance unevenness and good light diffusivity was obtained, and the present invention was completed.

That is, according to the present invention,
1. A method for producing a composite light diffusing plate in which a functional film is laminated on one side or both sides of a thermoplastic resin plate via an adhesive layer,
When the thermoplastic resin plate and the functional film are bonded to each other, an adhesive layer made of a hot-melt transparent resin having a melt viscosity in the range of 10 to 500,000 mPa · s is applied to the linear pressure in the range of 60 to 150 ° C. bonded at 0.01~1,000kg / cm, and the thickness of the adhesive layer (x1 (μm)), the surface roughness of either side of the thermoplastic resin plate or a functional film in contact with the adhesive layer A method for producing a composite light diffusing plate, wherein the following formula (i) is satisfied in relation to (ten-point surface roughness Rz1 (μm)).
x1 <0.3Rz1 (i)
2. The method for producing a composite light diffusing plate according to item 1, wherein the thickness of the adhesive layer (x1 (μm)) is 0.5 to 100 μm,
3. The method for producing a composite light diffusing plate according to item 1, wherein at least 50% by weight of the thermoplastic resin is made of a polycarbonate resin.
4). 2. The composite according to item 1, wherein the thermoplastic resin plate contains 0.3 to 10 parts by weight of a light diffusing agent and 0.0005 to 0.1 parts by weight of a fluorescent whitening agent with respect to 100 parts by weight of the thermoplastic resin. Manufacturing method of light diffusion plate, and
5 . The method for producing a composite light diffusing plate according to the preceding item 1, wherein the thermoplastic resin plate formed by a shaping roll having a geometric pattern is bonded to the functional film in a cooling step after melt extrusion,
Is provided.

Hereinafter, the present invention will be described in detail.
[Functional film]
The functional film used in the present invention has light diffusibility, preferably a film having a light diffusion performance of 50 to 99.5%, and more preferably 70 to 90%. If the haze is less than 50%, the diffusion performance is insufficient, so that it is difficult to obtain the effect of improving the brightness. If the haze exceeds 99.5%, the concealing effect increases, and the ratio of optical loss increases to increase the brightness. descend. The haze is a diffusion performance obtained by surface shaping, application or deflection of a light diffusing agent, or any combination thereof. There is no particular limitation on the shape of the surface shaping, but generally a geometric pattern is applied by embossing or the like, and if the ten-point average roughness Rz is in the range of 0.5 to 250 μm, diffusion performance can be imparted. Possible and preferred. When the molding is fine with Rz less than 0.5 μm, the diffusion performance is low, and when it is larger than 250 μm, the diffusion unevenness is large.

  In addition, a shape in which a certain fine uneven shape is continuously interposed, for example, a prism shape having an apex angle of 80 to 100 degrees on one side of the film is continuously given in one side direction within a groove pitch range of 50 to 500 μm. Since the light collecting property of the constituents and the like increases, it is more preferably used as a method for increasing the front luminance at the expense of the viewing angle in one side direction.

  As the surface shaping method of the functional film, a method of applying an electron beam curable resin to a flat film-shaped substrate, sandwiching it with a shaping roll, and curing it with an electron beam when the groove shape is transferred, or Examples include a method in which a thermoplastic resin is transferred and cooled and solidified while being sandwiched by a shaping roll during melt extrusion molding.

  As a method for applying a light diffusing agent to a functional film, an electron beam curable resin containing a light diffusing agent is applied to a flat film-like substrate and then cured by an electron beam, or a thermoplastic resin is melt extruded. For example, a method of adding a diffusing agent at the time of molding and cooling and solidifying can be used.

  As a method for imparting diffusion performance to the functional film with a light diffusing agent, a light diffusing agent having a refractive index difference of 0.01 to 0.2 with respect to the resin constituting the functional film is preferably used. . As will be described later with respect to the type of light diffusing agent, if the difference in refractive index is less than 0.01, sufficient diffusion performance cannot be obtained, and if it is greater than 0.2, the concealing effect is higher than the diffusion performance and the luminance is lowered. The average particle size of the light diffusing agent is preferably 0.5 to 50 μm. When the average particle size is less than 0.5 μm, the diffusion performance is lowered, and when it is more than 50 μm, the appearance and luminance unevenness are increased, which is not preferable.

As a method for imparting a polarizing function to the functional film, any method such as a cooling and solidification stage at the time of melt extrusion molding, or a reheating treatment and stretching is used as necessary.
The thermal linear expansion coefficient of the functional film should be close to the thermal linear expansion coefficient of the thermoplastic resin to be attached. The thermal linear expansion coefficient of the thermoplastic resin is F1 (/ ° C.), and the functional film is F (/ ° C.). In this case, it is preferable that 0.1F1 <F <10F1, more preferably 0.5F1 <F <5F1, and still more preferably 0.9F1 <F <2F1.
The thickness of the functional film is preferably 20 to 500 μm, and more preferably 30 to 150 μm.

  In the present invention, when the functional film is attached to the thermoplastic resin by thermocompression bonding, a certain amount of holes are provided between the adhesive layer and the thermoplastic resin or between the adhesive layer and the functional film. It is necessary to improve the appearance of the product, reduce the stress as much as possible, and suppress the occurrence of warpage.

  Specifically, when the functional film is attached to the thermoplastic resin by thermocompression bonding, the surface temperature Td (° C.) of the thermoplastic resin to be attached and the surface temperature Tf (° C.) of the functional film are as close as possible. Better, preferably Td-100 <Tf <Td + 100, more preferably Td-50 <Tf <Td + 50, and even more preferably Td-10 <Tf <Td + 10.

In the present invention, the thickness (x1 (μm)) of the adhesive layer and the surface roughness (ten-point surface roughness Rz1 (μm) of any surface of the thermoplastic resin plate or functional film in contact with the adhesive layer. )), The following formula (i) is satisfied, more preferably the following formula (ii) is satisfied.
x1 <0.3Rz1 (i)
x1 <0.1Rz1 (ii)

  When the surface roughness Rz1 of the adhesive layer thickness x1 and any surface of the thermoplastic resin plate or functional film in contact with the adhesive layer does not satisfy the above range (for example, x1 and Rz1 are substantially equal or x1). Since the pores between the adhesive layer and the thermoplastic resin or between the adhesive layer and the functional film are reduced or hardly seen, the functional film adhered on the optical characteristics is The problem that the effect becomes small or disappears is not preferable.

  As a method of increasing the surface roughness of the functional film surface or the thermoplastic resin plate surface, a forming roll with a reverse pattern such as embossed shape, prism shape (sawtooth shape), ridge shape or wave shape is used. For example, a method of shaping the surface, a method of blending transparent fine particles such as a light diffusing agent, and providing a fine uneven shape on the surface can be employed.

  The surface roughness (ten-point surface roughness Rz1 (μm)) of the functional film surface or the thermoplastic resin plate surface is preferably in the range of 2 to 350 μm, more preferably in the range of 10 to 200 μm, and in the range of 20 to 100 μm. Further preferred.

[Adhesive layer]
The resin used in the adhesive layer used in the present invention is preferably 40 wt% or more of a hot-melt transparent resin that generates an adhesive function in the range of 60 to 150 ° C, more preferably in the range of 80 to 150 ° C. Preferably, the composition contains 60% by weight or more.

  The hot melt type transparent resin is an adhesive that is bonded by generally bringing the member into close contact with each other in a heated state and solidifying by cooling, and is particularly limited as long as it can be used in the present invention. It is not a thing. Examples of the hot melt adhesive include hot melt adhesives such as ethylene vinyl acetate (EVA), polyamide, polyester, polyolefin, and styrene elastomer.

  A reactive hot melt adhesive generally refers to an adhesive that has been further improved in heat resistance, solvent resistance, etc. by imparting a crosslinked structure to the hot melt adhesive by some chemical reaction, and is used in the present invention. be able to.

  Further, as reactive hot melt adhesives, for example, moisture-reactive reactive hots such as urethane reactive hot melt adhesives containing isocyanate groups in the molecule and silicon hot melt adhesives containing silyl groups in the molecule. Examples include a melt adhesive, a radiation curable reactive hot melt adhesive that undergoes crosslinking upon irradiation with ultraviolet rays, electron beams, or the like. The urethane-based reactive hot melt adhesive has an isocyanate group in the molecule, and is preferable because it can exhibit excellent adhesive performance and durability by reacting with moisture and curing. Incidentally, for example, hot melt adhesives such as ethylene vinyl acetate (EVA) and polyamide generally need to be heated to about 180 ° C. in order to maintain a molten state, but reactive hot Since the melt adhesive can maintain its molten state by heating to a temperature of about 80 to 150 ° C., when a reactive hot melt adhesive is used, it is difficult to cause damage to the substrate due to heat. .

  Accordingly, a reactive hot melt adhesive is particularly preferable as the adhesive. As the reactive hot melt adhesive, one having a viscosity of 1000 to 30000 mPa · s (120 ° C.) that is melted by heating to 80 to 150 ° C. is preferable.

  Examples of the urethane-based reactive hot melt adhesive include, for example, an isocyanate-terminated urethane prepolymer in which an isocyanate group obtained by reaction of a polyol component and a polyisocyanate component remains, and an alkoxy having a hydrolyzable silyl group added to the urethane prepolymer. A silane terminal urethane prepolymer etc. can be illustrated.

  When the isocyanate-terminated urethane prepolymer is produced by reacting a polyol component and a polyisocyanate component, the equivalent ratio of the NCO group of the polyisocyanate component to the hydroxyl group of the polyol component (NCO group / hydroxyl group) is greater than 1. That is, it can be obtained by reacting the NCO group under an excessive condition. The equivalent ratio of NCO group / hydroxyl group is usually in the range of 1.1 to 5.0, preferably in the range of 1.5 to 3.0. Examples of such an isocyanate-terminated urethane prepolymer include Bond Master 170-7310 manufactured by Nippon NC and Perfect Lock MR70 manufactured by Nippon NC.

  The alkoxysilane-terminated urethane prepolymer can be obtained by reacting the above-mentioned isocyanate-terminated urethane prepolymer with a compound having both a functional group capable of reacting with an isocyanate group and a hydrolyzable silyl group. Examples of such alkoxysilane-terminated urethane prepolymers include urethane prepolymers described in JP-A Nos. 2003-193019 and 2769103.

  As the polyol component capable of producing the above-mentioned “urethane-based reactive hot melt adhesive”, polyol components that are usually used in the production of urethane-based reactive hot melt adhesives can be used, and are particularly limited. It is not a thing. Examples of such polyol components include polyester diols, polyether diols, and mixtures or copolymers thereof. Furthermore, for example, acrylic polyol, polycarbonate polyol, polyolefin polyol, castor oil polyol, polyhydric alcohol, and mixtures or copolymers thereof can be exemplified.

Further, as the polyisocyanate component capable of producing the urethane-based reactive hot melt described above, a polyisocyanate component usually used in the production of a urethane-based reactive hot melt adhesive can be used, and is particularly limited. It is not a thing. Examples of such polyisocyanate components include fragrances such as phenylene diisocyanate, tolylene diisocyanate (TDI), 4,4′-diphenylmethane diisocyanate, 2,4-diphenylmethane diisocyanate, naphthalene diisocyanate, xylylene diisocyanate, and tetramethylxylylene diisocyanate. Aliphatic or alicyclic diisocyanates such as aromatic diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate, and dicyclohexylmethane diisocyanate can be exemplified.
As the polyisocyanate component, those having a low vapor pressure during heating are preferable, and for example, diphenylmethane diisocyanate (MDI) is preferable.

  The urethane-based reactive hot melt adhesive is preferably one that melts in the range of 80 to 150 ° C. and has a viscosity of 1000 to 30000 mPa · s (120 ° C.). Moreover, since it is excellent in initial adhesive force, the urethane type reactive hot-melt-adhesive obtained using a polyester polyol as a polyol is preferable. Further, a reactive hot melt adhesive obtained by using a polyether polyol and / or other polyol (for example, acrylic polyol) in addition to the polyester polyol is preferable.

According to the present invention, in order to obtain retention of adhesive strength and porosity, the thickness of the adhesive layer is preferably 0.5-100 μm, more preferably 1-40 μm, even more preferably 1-10 μm. . If the thickness is less than 0.5 μm, it is difficult to have an adhesive strength that can withstand practical use at the interface between the rough surface and the adhesive layer, and if it exceeds 100 μm, the optical loss due to the adhesive layer increases, resulting in lower brightness. It is not preferable.

[Thermoplastic resin plate]
The resin thickness of the thermoplastic resin plate used in the present invention is preferably 0.5 to 5 mm, more preferably 0.7 to 3 mm, and still more preferably 1 to 2 mm. If it is less than 0.5 mm, the mechanical properties are low, so that it is difficult to use as a light diffusing plate for a large liquid crystal backlight. Moreover, when it exceeds 5 mm, an optical loss becomes large and a brightness | luminance falls.

  The thermoplastic resin may be a single layer or a laminate in which layers having, for example, a UV cut function, an antistatic performance, an IR cut performance, and an electromagnetic wave cut performance are laminated on one side and both sides. As a method for obtaining a laminate, there are a method by co-extrusion or a method in which a laminate film or a transfer foil is thermocompression bonded after melt extrusion.

  The thermoplastic resin plate may contain a light diffusing agent. Examples of the transparent fine particles used as the light diffusing agent include inorganic fine particles typified by glass fine particles, organic fine particles from polystyrene resin, (meth) acrylic resin, silicone resin and the like, and organic fine particles are preferable. Such organic fine particles are preferably cross-linked organic fine particles, which are at least partially cross-linked in the production process, and are not practically deformed in the process of processing the thermoplastic resin and maintain the fine particle state. . That is, fine particles that do not melt into the resin even when heated to the molding temperature (350 ° C.) of the thermoplastic resin are more preferred, and more preferred are crosslinked (meth) acrylic resin and organic fine particles of silicone resin. Particularly preferred embodiments thereof include, for example, a polymer having a poly (butyl acrylate) core / poly (methyl methacrylate) shell based on partially cross-linked methyl methacrylate, and a core and shell of rubbery vinyl polymer. A polymer having a core / shell monoholgy [trade name Paraloid EXL-5136 manufactured by Rohm and Hers Company] and a silicone resin having a crosslinked siloxane bond [Tospearl 120 manufactured by Toshiba Silicone Co., Ltd.] A single substance or a mixture of two or more kinds of fine particles may be used.

  The average particle size of the transparent fine particles is 0.5 to 50 μm, preferably 1 to 20 μm, particularly preferably 1 to 10 μm. The average particle diameter of the transparent fine particles is a weight average particle diameter measured by a coal counter method, and the measuring instrument is a particle number / particle size distribution analyzer MODEL Zm of Nikki Co., Ltd. If the average particle diameter is less than 0.5 μm, sufficient light diffusibility cannot be obtained and surface emission is inferior, and if it exceeds 50 μm, sufficient light diffusibility cannot be obtained and surface emission is inferior. In order to obtain the effect, the amount is increased and the optical loss is increased.

  In addition, about a compounding ratio of a thermoplastic resin and a light-diffusion agent (transparent fine particle), a required amount can be arbitrarily changed with the thickness of a thermoplastic resin board, the particle size of a light-diffusion agent, and a refractive index difference. Preferably, it is desirable to mix 0.3 to 10 parts by weight of the light diffusing agent with respect to 100 parts by weight of the thermoplastic resin.

  The thermoplastic resin resin plate in the present invention may have a geometric pattern on its surface as described above, and as its surface shape, an embossed shape having excellent light diffusibility, a prism shape (sawtooth shape), Arbitrary shapes such as a saddle shape or a wave shape are applied. Alternatively, a layer having a thickness of 10 to 100 μm may be provided on one side or both sides, and the layer may contain a light diffusing agent having a particle size of 10 μm or more, mica, talc, or the like to form a random embossed pattern on the surface. By providing a pattern such as a concavo-convex shape on the surface of the thermoplastic resin plate, diffusion performance is improved, and when a functional film is bonded, appropriate pores can be provided, and luminance is increased.

  As a method of obtaining a thermoplastic resin plate having a geometric pattern on the surface, mold cooling with a reverse pattern of a desired pattern such as embossed shape, prism shape (sawtooth shape), saddle shape or wave shape on the roll surface A method of sandwiching a thermoplastic resin plate melt-extruded by a roll and a mirror surface roll is preferably employed. By such a method, a thermoplastic resin plate can be produced industrially stably.

  The thermoplastic resin in the present invention is an arbitrary resin that is generally highly transparent and can be melt-extruded. For example, styrene resins such as PMMA resins, MS resins, AS resins, PET resins, polycarbonate resins, etc. Among them, polycarbonate resins are particularly preferably used in terms of mechanical strength and optical properties. That is, as a resin component constituting the thermoplastic resin plate, 50 to 100% by weight is preferably a polycarbonate resin, more preferably 70 to 100% by weight is a polycarbonate resin, and 90 to 100% by weight is a polycarbonate resin. More preferably, it is a resin.

  The polycarbonate resin used in the present invention is obtained by reacting a dihydric phenol and a carbonate precursor by an interfacial polycondensation method or a melt polymerization method. Representative examples of the dihydric phenol include 2,2-bis (4-hydroxyphenyl) propane [commonly known as bisphenol A], 1,1-bis (4-hydroxyphenyl) ethane, and 1,1-bis (4-hydroxy). Phenyl) cyclohexane, 2,2-bis (3-methyl-4-hydroxyphenyl) propane, 2,2-bis (3,5-dimethyl-4-hydroxyphenyl) propane, bis (4-hydroxyphenyl) sulfide, bis (4-hydroxyphenyl) sulfone and the like can be mentioned, and among them, bisphenol A is preferable. These dihydric phenols can be used alone or in admixture of two or more.

  As the carbonate precursor, carbonyl halide, carbonate ester, haloformate or the like is used, and specific examples include phosgene, diphenyl carbonate, dihaloformate of dihydric phenol, and the like.

  In producing a polycarbonate resin by reacting the dihydric phenol and the carbonate precursor by an interfacial polycondensation method or a melt polymerization method, a catalyst, a terminal terminator, a dihydric phenol antioxidant, etc. are added as necessary. May be used. The polycarbonate resin may be a branched polycarbonate resin copolymerized with a trifunctional or higher polyfunctional aromatic compound, or may be a polyester carbonate resin copolymerized with an aromatic or aliphatic difunctional carboxylic acid, Moreover, the mixture which mixed 2 or more types of the obtained polycarbonate resin may be sufficient.

The molecular weight of the polycarbonate resin is represented by the viscosity-average molecular weight, preferably from ^{1.5 × 10 4 ~4.0 × 10 4} , more preferably ^{1.8 × 10 4 ~3.5 × 10 4} . The viscosity average molecular weight referred to in the present invention is obtained by inserting the specific viscosity (η _sp ) obtained from a solution obtained by dissolving 0.7 g of polycarbonate resin in 100 ml of methylene chloride at 20 ° C. into the following equation.
η _sp /c=[η]+0.45×[η] ² c
[Η] = 1.23 × 10 ⁻⁴ M ^0.83
(Where c = 0.7, [η] is the intrinsic viscosity)

  As a method for obtaining a thermoplastic resin plate (in particular, a polycarbonate resin plate), any method and apparatus can be used. For example, it is preferable to form a plate having a predetermined thickness by a melt extrusion method. In the case of melt extrusion, it is preferable to extrude by reducing the melting zone of the extruder to 1.33 to 66.5 kPa. When the melting zone of the extruder is not reduced in pressure, the resin and the blended additive may be thermally deteriorated due to the influence of oxygen and the light diffusion performance may be reduced. In addition, it is also possible to form by a conventionally known method, for example, injection molding, injection compression molding, blow molding, compression molding, powder molding or the like.

  In addition to the above components, other components such as fluorescent brightener, phosphorous acid, phosphoric acid, phosphorous ester, phosphoric ester, phosphone can be used as long as the thermoplastic resin plate is obtained. Heat stabilizers such as acid esters, mold release agents such as fatty acid ester compounds, UV absorbers such as triazoles, acetophenones, salicylates, bluing agents, tetrabromobisphenol A, low molecular weight polycarbonate of tetrabromobisphenol A, Additives such as flame retardants such as decabromodiphenylene ether and flame retardant aids such as antimony trioxide may be added to the thermoplastic resin as expressed.

  In the present invention, the fluorescent whitening agent appropriately blended in the thermoplastic resin plate is not particularly limited as long as it is used for improving the color tone of a synthetic resin to white or bluish white. , Benzimidazole, benzoxazole, naphthalimide, rhodamine, coumarin, and oxazine compounds. Here, the fluorescent whitening agent has an action of absorbing energy in the ultraviolet part of the light and radiating this energy to the visible part. The compounding amount of the fluorescent brightening agent is preferably in the range of 0.0005 to 0.1 parts by weight, more preferably in the range of 0.001 to 0.1 parts by weight, with respect to 100 parts by weight of the resin. The range of 0.05 parts by weight is more preferable, and the range of 0.005 to 0.02 parts by weight is particularly preferable. By blending the fluorescent brightening agent in the above range, the surface light emission is sufficient, the effect of improving the color tone of the light emitting surface is obtained, and there is no color tone unevenness, which is preferable.

  In the present invention, the heat stabilizer appropriately blended in the thermoplastic resin plate can be used for preventing a decrease in molecular weight and a deterioration in hue during molding of the polycarbonate resin. Examples of such heat stabilizers include phosphorous acid, phosphoric acid, phosphonous acid, phosphonic acid, and esters thereof.

  Specifically, triphenyl phosphite, tris (nonylphenyl) phosphite, tridecyl phosphite, trioctyl phosphite, trioctadecyl phosphite, didecyl monophenyl phosphite, dioctyl monophenyl phosphite, diisopropyl monophenyl phosphite Phyto, monobutyl diphenyl phosphite, monodecyl diphenyl phosphite, monooctyl diphenyl phosphite, tris (2,4-di-tert-butylphenyl) phosphite, bis (2,6-di-tert-butyl-4- Methylphenyl) pentaerythritol diphosphite, 2,2-methylenebis (4,6-di-tert-butylphenyl) octyl phosphite, bis (nonylphenyl) pentaerythritol diphosphite, bis 2,4-di-tert-butylphenyl) pentaerythritol diphosphite, distearyl pentaerythritol diphosphite, tributyl phosphate, triethyl phosphate, trimethyl phosphate, triphenyl phosphate, diphenyl monooxoxenyl phosphate, dibutyl phosphate, dioctyl phosphate , Diisopropyl phosphate, tetrakis (2,4-di-iso-propylphenyl) -4,4′-biphenylene diphosphonite, tetrakis (2,4-di-n-butylphenyl) -4,4′-biphenylene diphospho Knight, tetrakis (2,4-di-tert-butylphenyl) -4,4'-biphenylenediphosphonite, tetrakis (2,4-di-tert-butylphenyl) -4,3'-bi Enylene diphosphonite, tetrakis (2,4-di-tert-butylphenyl) -3,3′-biphenylenediphosphonite, tetrakis (2,6-di-iso-propylphenyl) -4,4′-biphenyl Range phosphonite, tetrakis (2,6-di-n-butylphenyl) -4,4'-biphenylene diphosphonite, tetrakis (2,6-di-tert-butylphenyl) -4,4'-biphenylene diphospho Knight, tetrakis (2,6-di-tert-butylphenyl) -4,3′-biphenylene diphosphonite, tetrakis (2,6-di-tert-butylphenyl) -3,3′-biphenylene diphosphonite, Bis (2,4-di-tert-butylphenyl) -biphenylphosphonite, benzene phosphonate dimethyl, benzene Suhon diethyl, dipropyl, and the like benzene phosphonic acid.

 Among them, tris (2,4-di-tert-butylphenyl) phosphite, tetrakis (2,4-di-tert-butylphenyl) -4,4′-biphenylenediphosphonite and bis (2,4-di-) tert-Butylphenyl) -biphenylphosphonite is preferred.

These heat stabilizers may be used alone or in combination of two or more. The amount of the heat stabilizer used is preferably 0.001 to 0.15 parts by weight with respect to 100 parts by weight of the resin.
In the present invention, a fatty acid ester compound can be used as a mold release agent that is appropriately blended in the thermoplastic resin plate for the purpose of improving mold release from the mold during molding.

  Such a fatty acid ester is preferably a partial ester or a total ester of a monovalent or polyhydric alcohol having 1 to 20 carbon atoms and a saturated fatty acid having 10 to 30 carbon atoms. Such partial esters or total esters of monohydric or polyhydric alcohols and saturated fatty acids include stearic acid monoglyceride, stearic acid diglyceride, stearic acid triglyceride, stearic acid monosorbate, behenic acid monoglyceride, pentaerythritol monostearate, pentaerythritol. Tetrastearate, pentaerythritol tetrapelargonate, propylene glycol monostearate, stearyl stearate, palmityl palmitate, butyl stearate, methyl laurate, isopropyl palmitate, biphenyl biphenate, sorbitan monostearate, 2-ethylhexyl stearate Such as stearic acid monoglyceride, stearic acid triglyceride, pentaerythris Tall tetrastearate are preferably used. The amount of the fatty acid ester used is preferably 0.001 to 0.5 parts by weight with respect to 100 parts by weight of the resin.

  In the present invention, an ultraviolet absorber is appropriately blended in the thermoplastic resin plate for the purpose of improving weather resistance and cutting harmful ultraviolet rays. Examples of such ultraviolet absorbers include benzophenone-based ultraviolet absorbers represented by 2,2′-dihydroxy-4-methoxybenzophenone, 2- (4,6-diphenyl-1,3,5-triazin-2-yl)- Triazine-based ultraviolet absorbers typified by 5-hexyloxyphenol, 2- (2H-benzotriazol-2-yl) -4-methylphenol, 2- (2H-benzotriazol-2-yl) -4-tert- Octylphenol, 2- (2H-benzotriazol-2-yl) -4,6-bis (1-methyl-1-phenylethyl) phenol, 2- (2H-benzotriazol-2-yl) -4,6-di -Tert-pentylphenol, 2- (5-chloro-2H-benzotriazol-2-yl) -4-methyl-6-tert-buty Phenol, 2- (5-chloro-2H-benzotriazol-2-yl) -2,4-tert-butylphenol and 2,2′-methylenebis [6- (2H-benzotriazol-2-yl) -4- ( 1,1,3,3-tetramethylbutyl) phenol] and the like are exemplified.

Preferably, 2- (2-hydroxy-5-methylphenyl) benzotriazole, 2- (2-hydroxy-5-tert-octylphenyl) benzotriazole, 2- (2-hydroxy-3,5-dicumyl) Phenyl) phenylbenzotriazole, 2- (2-hydroxy-3-tert-butyl-5-methylphenyl) -5-chlorobenzotriazole, 2,2′-methylenebis [4- (1,1,3,3-tetra Methylbutyl) -6- (2H-benzotriazol-2-yl) phenol], 2- [2-hydroxy-3- (3,4,5,6-tetrahydrophthalimidomethyl) -5-methylphenyl] benzotriazole And more preferably 2- (2-hydroxy-5-tert-octylphenyl) benzotriazole, 2,2′- A Chirenbisu [4- (1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl) phenol].
Such ultraviolet absorbers may be used alone or in combination of two or more, and are preferably used in an amount of 0.01 to 10 parts by weight, more preferably 0.05 to 5 parts by weight, based on 100 parts by weight of the resin.

  In the present invention, when the thermoplastic resin is molded into a light diffusing resin plate, a bluing agent can be blended in order to counteract the yellowness of the resin plate based on the resin or the ultraviolet absorber. Any bluing agent can be used without any problem as long as it is used for a resin. In general, anthraquinone dyes are preferred because they are readily available.

Specific examples of the bluing agent include the general name Solvent Violet 13 [CA. No. (Color Index No.) 60725; Trade names “Macrolex Violet B” manufactured by Bayer, “Diaresin Blue G” manufactured by Mitsubishi Chemical Corporation, “Sumiplast Violet B” manufactured by Sumitomo Chemical Co., Ltd.], general name Solvent Violet 31 [CA. No. 68210; Trade name “Diaresin Violet D” manufactured by Mitsubishi Chemical Corporation], generic name Solvent Violet 33 [CA. No. 60725; Trade name “Diaresin Blue J” manufactured by Mitsubishi Chemical Corporation], generic name Solvent Blue 94 [CA. No. 61500; trade name “Diaresin Blue N” manufactured by Mitsubishi Chemical Corporation, generic name Solvent Violet 36 [CA. No. 68210; Trade name “Macrolex Violet 3R” manufactured by Bayer, Inc., generic name Solvent Blue 97 [trade name “Macrolex Violet RR” manufactured by Bayer, Inc.] and generic name Solvent Blue 45 [CA. No. 61110; trade name “Tetrazole Blue RLS” manufactured by Sand Corp.] is a typical example. These bluing agents are preferably blended at a ratio of 0.3 × 10 ⁻⁴ to 2 × 10 ⁻⁴ parts by weight per 100 parts by weight of the resin.

  As a method for laminating the functional film and the thermoplastic resin plate, any method can be adopted as long as it can be thermocompression bonded. Examples thereof include a method of thermocompression bonding with a laminating machine, a press machine, etc., and a method of pressure bonding to a polycarbonate resin plate in a molten state immediately after extrusion. In particular, a method of pressure bonding to a polycarbonate resin plate in a molten state immediately after extrusion is preferable. Thermocompression bonding conditions vary depending on the properties of the adhesive layer used and cannot be specified unconditionally. However, the temperature condition where the viscosity of the adhesive layer is preferably 10 to 500,000 mPa · s, more preferably 1,000 to 50,000 mPa · s. Thus, a method of thermocompression bonding by applying a linear pressure of preferably 0.01 to 1,000 kg / cm, more preferably 0.03 to 100 kg / cm, and still more preferably 1 to 10 kg / cm is employed.

  The composite diffuser plate of the present invention is a composite diffuser plate having higher luminance and less luminance unevenness than a conventional single diffuser plate, and is continuously integrated. Therefore, it is suitable for a light diffusion plate of a direct backlight type of a liquid crystal display or a liquid crystal television currently used in the market, and the performance of the liquid crystal television is improved by using the composite diffusion plate of the present invention, or the film member Not only can the cost be reduced by reducing assembly man-hours, but also the automation of backlight unit assembly, which was difficult due to the large number of future components, is also considered, so the industrial effect brought by the present invention is exceptional. Is.

  The following examples further illustrate the present invention. The evaluation items and methods are as follows.

(1) Front luminance: The obtained composite light diffusing plate was cut into a length of 318 mm and a width of 418 mm, and this was incorporated into a 20-inch direct type backlight unit, and the luminance (cd / m ² ) at one center was calculated by Topcon Corporation. It measured with the luminance meter BM-7 made from. The evaluation apparatus is shown in FIGS.
In addition, about Examples 1-6 and Comparative Examples 3-5, only the composite light diffusing plate was incorporated in the backlight unit and evaluated. Comparative Example 1 was evaluated by incorporating only a polycarbonate resin light diffusion plate that was not combined. Comparative Example 2 was evaluated by incorporating a light diffusion plate made of a polycarbonate resin that was not complexed and placing a prism film thereon. For Examples 1 to 6 and Comparative Examples 2 to 5, composite light diffusion plates were prepared so that the direction of the BEFII prism was parallel to the cold cathode tube.

(2) Luminance unevenness: When incorporated in the backlight unit in (1) above, visually observe the light emitting surface, and if the luminance unevenness (lamp unevenness) cannot be visually confirmed or difficult to confirm, The items that can be confirmed were evaluated with x.

(3) Ten-point surface roughness (Rz (μm)): The resin light diffusion plate and the functional film surface were measured with a color 3D laser microscope VK-9700 (manufactured by Keyence Corporation).

(4) Dimensional change due to heat: The obtained composite light diffusing plate was cut into a length of 560 mm and a width of 960 mm, and this was incorporated into a 42-inch backlight unit and left for 100 hours with the lamp turned on in an atmosphere at 80 ° C. Thereafter, the lamp was turned off at room temperature for 24 hours, and then the lamp was turned on, the composite diffuser plate was removed, and the dimensions thereof were measured with calipers. A sample in which the dimensional change of the composite diffusion plate before and after the treatment was less than 2 mm was evaluated as ○, and a sample in which the change was 2 mm or more was evaluated as ×.

  In addition, about Examples 1-6 and Comparative Examples 3-5, only the composite light diffusing plate was incorporated in the backlight unit and evaluated. Comparative Example 1 was evaluated by incorporating only a polycarbonate resin light diffusion plate that was not combined. Comparative Example 2 was evaluated by incorporating a light diffusion plate made of a polycarbonate resin that was not complexed and placing a prism film thereon. For Examples 1 to 6 and Comparative Examples 2 to 5, composite light diffusion plates were prepared so that the direction of the BEFII prism was parallel to the cold cathode tube.

In addition, the functional films A shown in Table 1 and the adhesives B and C used as the adhesive layer are as follows.
Functional film A: Prism film BEFII 90/50 Sumitomo 3M Co., Ltd. Adhesive B: Hot melt adhesive Bondmaster 170-7141 Nippon NS Co., Ltd. Adhesive C: Hot melt adhesive Perfect Lock MR150 Nihon NS Made by Sea Co., Ltd.

[Example 1]
[Diffusion plate manufacturing method]
100 parts by weight of a polycarbonate resin having a viscosity average molecular weight of 24,300 obtained from bisphenol A and phosgene, 0.8 parts by weight of a light diffusing agent [TOSPARAL 120 manufactured by Toshiba Silicone Co., Ltd., weight average particle size 2 μm], fluorescent whitening agent [Nippon Kayaku Kogyo Kayalite OS] 0.02 parts by weight, trimethyl phosphate [Daihachi Chemical Industry Co., Ltd.] 0.01 parts by weight, tetrakis-2,4-di-t-butylphenyl-4 , 4'-biphenylenediphosphinic acid [Sand stub P-EPQ manufactured by Sand Co., Ltd.] 0.05 parts by weight was previously added and mixed, and the temperature of the extruder was 250 to 300 ° C. with a vented T-die extruder. Melting a polycarbonate resin light diffuser plate with a die temperature of 260-300 ° C and a vent section vacuum of 26.6 kPa, with a thickness of 2 mm and a width of 1,000 mm Extruded (Figure 3). At that time, a rough surface roll was used as the cooling roll 2 so that one side was a rough surface and one side was a mirror surface (FIG. 4).

[Production method of composite diffuser]
In the cooling process of the light diffusion plate made of the polycarbonate resin, the functional film A having a smooth surface (non-prism surface) previously provided with a 2 μm adhesive layer B under the conditions of a pressing roll temperature of 130 ° C. and a linear pressure of 10 kg / cm The adhesive layer was attached to the rough surface side of the polycarbonate resin light diffusion plate to obtain a composite diffusion plate (FIGS. 3 and 5). The evaluation results of this composite diffusion plate are shown in Table 1.

[Example 2]
[Production method of diffusion plate and composite diffusion plate]
A composite diffuser plate was obtained in the same manner as in Example 1 except that the functional film A provided with 1 μm adhesive layer B was used (FIG. 5). The evaluation results of this composite diffusion plate are shown in Table 1.

[Example 3]
[Production method of diffusion plate and composite diffusion plate]
A composite diffusion plate was obtained by performing the same operation as in Example 1 except that the amount of the light diffusing agent was changed to 2.1 parts by weight and the thickness of the light diffusion plate made of polycarbonate resin was changed to 1 mm (FIG. 5). ). The evaluation results of this composite diffusion plate are shown in Table 1.

[Example 4]
[Diffusion plate manufacturing method]
A PC / AS alloy resin in which 70 parts by weight of a polycarbonate resin having a viscosity average molecular weight of 24,300 obtained from bisphenol A and phosgene is mixed with 30 parts by weight of an AS resin (HF5670 manufactured by Daiichi Woolen Co., Ltd.) ) Tospearl 120, weight average particle diameter 2 μm] 2.1 parts by weight, fluorescent brightener [Kayalite OS, Nippon Kayaku Kogyo Co., Ltd.] 0.02 parts by weight, trimethyl phosphate [Daihachi Chemical Industries, Ltd. ] 0.01 parts by weight, tetrakis-2,4-di-t-butylphenyl-4,4'-biphenylenediphosphinic acid [Sand Stub P-EPQ manufactured by Sand Corp.] 0.05 parts by weight previously mixed Were added and mixed, and with a T-die extruder with a vent, the extruder temperature was 250 to 300 ° C., the die temperature was 260 to 300 ° C., and the degree of vacuum at the vent was 26.6 kPa. A polycarbonate resin light diffusion plate having a thickness of 1 mm and a width of 1,000 mm was melt-extruded (FIG. 3). At that time, one side was a rough surface and one side was a mirror surface (FIG. 4).

[Production method of composite diffuser]
The same operation as in Example 1 was performed to obtain a composite diffusion plate (FIG. 5).

[Example 5]
[Production method of diffusion plate and composite diffusion plate]
Except that the adhesive layer B was changed to the adhesive layer C, the same operation as in Example 1 was performed to obtain a composite diffusion plate (FIG. 5). The evaluation results of this composite diffusion plate are shown in Table 1.

[Example 6]
[Production method of diffusion plate and composite diffusion plate]
A 2 μm adhesive layer B was applied to the mirror surface of the polycarbonate resin light diffusing plate obtained in Example 1, and a small laminator [MCK Halder Laminator MRK650Y] was used. Pressing roll temperature 130 ° C., linear pressure 5 kg / Under the conditions of cm, the prism surface of the functional film A was bonded to the adhesive layer to obtain a composite diffusion plate (FIG. 7). The evaluation results of this composite diffusion plate are shown in Table 1.

[Comparative Example 1]
The polycarbonate resin light diffusion plate (FIG. 4) obtained in Example 1 was collected, and the evaluation results are shown in Table 1.

[Comparative Example 2]
The functional film was placed on the polycarbonate resin light diffusion plate obtained in Example 1 without any treatment (FIG. 8) and evaluated. The evaluation results are shown in Table 1.

[Comparative Example 3]
[Production method of diffusion plate and composite diffusion plate]
A composite diffusion plate was obtained by performing the same operation as in Example 1 except that the adhesive layer of the functional film A provided with the 2 μm adhesive layer B was attached to the mirror surface side of the polycarbonate resin light diffusion plate ( FIG. 6). The evaluation results of this composite diffusion plate are shown in Table 1.

[Comparative Example 4]
[Production method of diffusion plate and composite diffusion plate]
A composite diffusion plate was obtained by performing the same operation as in Example 1 except that the thickness of the adhesive layer B was changed to 20 μm (FIG. 5). The evaluation results of this composite diffusion plate are shown in Table 1.

[Comparative Example 5]
A composite diffusion plate was obtained by performing the same operation as in Example 6 except that the thickness of the adhesive layer B was changed to 50 μm (FIG. 7). The evaluation results of this composite diffusion plate are shown in Table 1.

FIG. 1 is a simplified cross-sectional view of the evaluation apparatus of the present invention. FIG. 2 is a simplified plan view of the evaluation apparatus of the present invention. FIG. 3 is a simplified cross-sectional view of the extrusion and cooling steps used to produce the diffusion plates and composite diffusion plates in the examples and comparative examples. FIG. 4 is a simplified cross-sectional view of the light diffusing plate used in Examples 1-6 and Comparative Examples 1-5. FIG. 5 is a simplified cross-sectional view of the composite light diffusing plate used in Examples 1 to 5 and Comparative Example 4. FIG. 6 is a simplified cross-sectional view of the composite light diffusing plate used in Comparative Example 3. FIG. 7 is a simplified cross-sectional view of the composite light diffusing plate used in Example 6 and Comparative Example 5. FIG. 8 is a simplified cross-sectional view of the composite light diffusing plate used in Comparative Example 2.

Explanation of symbols

1 Test piece 2 White reflective resin plate 3 to 10 Light source (cold cathode tube)
11 Measurement point 12 T die 13 Cooling roll 1
14 Cooling roll 2
15 Cooling roll 3
16 Swing roll 17 Conveying roll 18 Heating heater 19 Expander roll 20 Pressing roll 1
21 Extruded resin 22 Functional film for pasting 23 Resin plate 24 Light diffusion plate 25 Rough surface side of light diffusion plate 26 Mirror surface side of light diffusion plate 27 Prism film 28 Adhesive layer

Claims (5)

A method for producing a composite light diffusing plate in which a functional film is laminated on one side or both sides of a thermoplastic resin plate via an adhesive layer,
When the thermoplastic resin plate and the functional film are bonded to each other, an adhesive layer made of a hot-melt transparent resin having a melt viscosity in the range of 10 to 500,000 mPa · s is applied to the linear pressure in the range of 60 to 150 ° C. bonded at 0.01~1,000kg / cm, and the thickness of the adhesive layer (x1 (μm)), the surface roughness of either side of the thermoplastic resin plate or a functional film in contact with the adhesive layer A method for producing a composite light diffusing plate, wherein the following formula (i) is satisfied in relation to (ten-point surface roughness Rz1 (μm)).
x1 <0.3Rz1 (i)   The method for producing a composite light diffusing plate according to claim 1, wherein the adhesive layer has a thickness (x1 (µm)) of 0.5 to 100 µm.   2. The method for producing a composite light diffusing plate according to claim 1, wherein at least 50% by weight of the thermoplastic resin is made of a polycarbonate resin. The thermoplastic resin plate contains 0.3 to 10 parts by weight of a light diffusing agent and 0.0005 to 0.1 parts by weight of a fluorescent whitening agent with respect to 100 parts by weight of the thermoplastic resin. A method for manufacturing a composite light diffusion plate .   The method for producing a composite light diffusing plate according to claim 1, wherein the thermoplastic resin plate formed by a shaping roll having a geometric pattern is bonded to the functional film in a cooling step after melt extrusion. .

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