JP5139646B2 - Manufacturing method of light diffusion plate - Google Patents

Description

The present invention relates to a method for producing a polycarbonate resin light diffusion plate. The warp of the liquid crystal side, more particularly by water absorption and drying difference polycarbonate resin, by suppressing in the internal stress of a polycarbonate resin, luminance unevenness of the light-emitting surface has a stable surface-emitting property was excellent less shade polycarbonate The present invention relates to a method for manufacturing a resin light diffusion plate.

  In light diffusion plates that are part of the components of backlight units used as light sources for various liquid crystal displays such as liquid crystal televisions, acrylic resins and polycarbonate resins are used as matrix resins, and various light diffusing agents are used there. A light diffusing plate formed from a resin composition to which is added is used.

  As a polycarbonate resin composition suitably used as a matrix resin for a light diffusing plate of a liquid crystal display, a resin composition in which calcium carbonate and titanium oxide are added to a polycarbonate resin (Patent Document 1), calcium carbonate or crosslinked poly- carbonate is added to the polycarbonate resin. A resin composition in which an arylate resin is added (see Patent Document 2), a resin composition in which a bead-like crosslinked acrylic resin is blended with a polycarbonate resin (see Patent Document 3), a bead-like crosslinked acrylic resin and an optical brightener in a polycarbonate resin An added resin composition (see Patent Document 4) is disclosed.

  In recent years, liquid crystal displays and liquid crystal televisions, which have been increased in size to 20 to 50 inches, are becoming mainstream due to the increase in area. Large light diffusing plates used in these applications cause warpage fluctuations due to drying due to the heat of the light source, etc., and easily come into contact with the light control film and the liquid crystal panel placed on the light diffusing plate. Was sometimes observed. On the other hand, liquid crystal displays and liquid crystal televisions are becoming thinner, and the clearance between the light diffusing plate, the light adjusting film and the liquid crystal panel tends to be small, and a light diffusing plate having a small warp under heating conditions is required.

Japanese Patent Laid-Open No. 03-078701 Japanese Patent Laid-Open No. 05-257002 Japanese Patent Laid-Open No. 08-188709 Japanese Patent Laid-Open No. 09-020860

An object of the present invention, the backlighting light source, a polycarbonate resin light diffusion plate, light management films and suitable for direct backlight type liquid crystal display device free from uneven brightness comprising a liquid crystal panel, the liquid crystal surface side under heating It is providing the manufacturing method of the light-diffusion board made from a polycarbonate resin with small curvature to.

Another object of the present invention, the warping of the liquid crystal surface side due to the difference between the dry and the water of the polycarbonate resin diffuser that suppresses internal stress of a polycarbonate resin, the light-emitting surface of a stable surface emitting It is an object of the present invention to provide a method for producing a light diffusing plate with little luminance unevenness and excellent color tone, particularly a polycarbonate resin light diffusing plate suitable for a direct type backlight system of a large liquid crystal display or a large liquid crystal television.

As a result of intensive studies in order to achieve the above object, the present inventor can obtain a polycarbonate resin light diffusing plate having an internal stress such that the variation in warping due to heating is within a certain range under specific manufacturing conditions. As a result, the present invention has been completed.

That is, according to the present invention,
1. (I) A light-resistant layer is laminated on one side , and (ii) the warpage rate X ₂ (%) when heated at 150 ° C. for 10 minutes is in the range of 0.5 ≦ X ₂ ≦ 10 (convex to the light-resistant layer side) (Iii) warp rate Y ₂ (%) at 23 ° C. is in the range of 0.5 ≦ Y ₂ ≦ 5 (warp in the direction of convex toward the light-resistant layer) The method of manufacturing a polycarbonate resin light diffusing plate, wherein the light diffusing plate has a temperature of the polycarbonate resin sheet melt-extruded in a horizontal three-roll sheet forming machine. With respect to the next transition temperature (Tg), the temperature (T ₁ ° C) of the first cooling roll is (Tg-33) ≤T ₁ ≤ (Tg-27), and the temperature (T ₂ ° C) of the second cooling roll is ( Tg−35) ≦ T ₂ ≦ (Tg−29), the temperature of the third cooling roll (T ₃ ° C.) to _{(Tg-8) ≦ T 3} ≦ (Tg-3), and 22 ≦ _(T 3 -T ₂₎ is produced by controlling the range of ≦ 30, the manufacturing method of the light diffusion plate.
2. 2. The method for producing a light diffusing plate according to 1 above, wherein the polycarbonate resin is a bisphenol A type polycarbonate resin .
3. The said light diffusing plate is a manufacturing method of the light diffusing plate of the preceding clause 1 containing 0.1-10 weight part of light diffusing agents with respect to 100 weight part of polycarbonate resin .
4). The said light diffusing plate is a manufacturing method of the light diffusing plate of the preceding clause 1 containing 0.0005 to 0.1 weight part of fluorescent whitening agents with respect to 100 weight part of polycarbonate resin .
Is provided.

Hereinafter, a direct backlight type liquid crystal display device in which the light diffusion plate obtained by the production method of the present invention is suitably used will be described . Directly under type back light type liquid crystal display device includes a backlight source, a polycarbonate resin light diffusion plate, a light modulating film and the liquid crystal panel. The apparatus can be manufactured by arranging a backlight light source, a polycarbonate resin light diffusion plate, a light adjusting film and a liquid crystal panel in this order. Preferably, the apparatus has a protective film on the backlight source side of the light diffusion plate or on both surfaces of the light diffusion plate, if desired.

<Backlight source>
The backlight light source may be any light source as long as it is disposed directly under the light emitting surface and can irradiate visible light. Incandescent light bulbs, fluorescent discharge tubes, light emitting diode elements, and fluorescent light emitting elements can be used. From the viewpoint of color temperature and the like, a fluorescent discharge tube, among them, a cold cathode fluorescent lamp is preferable. Particularly recently, cold cathode fluorescent lamps using three-wavelength phosphors with low power consumption and high luminance and high color rendering have been used.

  The structure of the cold cathode fluorescent lamp used in the backlight light source is that the phosphor is applied to the inner wall of a glass tube filled with an appropriate amount of mercury and inert gas (argon, neon, mixed gas, etc.), and both ends of the glass tube Is in a state where a columnar electrode is attached.

  The light emission mechanism of the cold cathode fluorescent lamp is that when a high voltage is applied between the electrodes, a slight amount of electrons in the tube are attracted to the electrode and collide at high speed, and at this time, secondary electrons are emitted and discharge occurs. Begins. Due to this discharge, electrons attracted by the anode collide with mercury molecules in the tube, and ultraviolet rays (wavelength λ = about 250 nm) are emitted, and the ultraviolet rays excite the phosphor to emit visible light.

<Light control film>
Examples of the light adjusting film include a film having a function of condensing, diffusing, or polarizing light emitted from the light diffusion plate. The light adjusting film is usually disposed between the light diffusing plate and the liquid crystal panel. Examples of the condensing film include a film having a prismatic surface (for example, BEF manufactured by Yamagata 3M). Examples of the diffusion film include a film containing a diffusing agent. Examples of the polarizing film include a reflective polarizing film (for example, Yamagata 3M). Manufactured D-BEF).
These are composed of, for example, a diffusion film, a condensing film, and a polarizing film in this order from the light diffusion plate side, and light transmitted through the polarizing film enters the liquid crystal panel unit.

<LCD panel>
The liquid crystal panel is configured to have a polarizing plate in at least one of the liquid crystal cells. It is preferable that the liquid crystal cell has an electrode and at least one surface thereof is transparent. Further, if desired, a color filter may be sandwiched between the liquid crystal cell and the polarizing plate. The liquid crystal cell can be made from a thermoplastic resin such as glass or a polymer film.

<Light diffusion plate made of thermoplastic resin>
The thermoplastic resin light diffusion plate of the present invention preferably has a thickness of 1.2 to 3.5 mm, more preferably a thickness of 1.5 to 3.0 mm, and even more preferably a thickness of 2.0 to 3.0 mm. It is. If it is thinner than 1.2 mm, the light diffusibility tends to be insufficient, and the rigidity is insufficient, so that it is not suitable. If it is thicker than 3.0 mm, the optical loss due to the thickness tends to increase, and it is not practical in weight. The optical loss here means a loss of luminance. That is, the backlight light source emits light from the cold-cathode tube, and light that is finally converged in the front direction of the screen while repeating transmission and reflection in all directions by the light diffusion plate and internal reflection plate. However, if some factor (additive, burn, etc.) that absorbs the light emitted from the cold cathode tube exists in the light diffusion plate, the absorption of the light is Since it occurs repeatedly on the reflector, the final result is a decrease in brightness.

  The thermoplastic resin light diffusing plate has light diffusibility, and includes a method of containing a light diffusing agent in a transparent thermoplastic resin sheet, and the surface shape of the transparent thermoplastic resin sheet is made uneven. Or a method using these in combination. The total light transmittance of the thermoplastic resin light diffusion plate is preferably 50% or more, and the haze is preferably 98% or more.

  The light diffusing agent is in the form of fine particles, and examples thereof include inorganic fine particles typified by glass fine particles, organic fine particles from polystyrene resin, (meth) acrylic resin, silicone resin, etc. Among them, 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 in the thermoplastic resin even when heated to the molding temperature of the thermoplastic resin (for example, the molding temperature of the polycarbonate resin is about 350 ° C.) are more preferable. Specifically, a crosslinked (meth) acrylic resin, silicone Organic fine particles of resin. Particularly preferred embodiments include polymer particles based on partially crosslinked methyl methacrylate, poly (butyl acrylate) core / poly (methyl methacrylate) shell polymer, rubbery vinyl polymer core and shell. Examples thereof include a polymer having a core / shell monoholgy [for example, trade name Paraloid EXL-5136 manufactured by Rohm and Hers Company] and a silicone resin having a crosslinked siloxane bond [for example, Tospearl 120 manufactured by Toshiba Silicone Co., Ltd.].

  The fine particle light diffusing agent preferably has an average particle diameter of 1 to 30 μm, more preferably 2 to 20 μm. The particle size of the light diffusing agent is a weight average particle size measured by a Cole counter method, and the measuring instrument is a particle number / particle size distribution analyzer MODEL Zm of Nikki Co., Ltd. If the weight average particle diameter is less than 1 μm, the light concealing action works, so that sufficient light diffusibility cannot be obtained and surface emission is inferior. If it exceeds 30 μm, sufficient light diffusibility cannot be obtained and surface emission is not good. Inferior, in order to obtain a sufficient light diffusion effect, the compounding amount increases, so that the extrusion moldability becomes unstable and the surface property is inferior, resulting in optical loss.

  The blending ratio of the thermoplastic resin and the light diffusing agent is preferably 0.1 to 10 parts by weight, more preferably 0.2 to 5 parts by weight with respect to 100 parts by weight of the thermoplastic resin. Although depending on the thickness of the light diffusing plate, if the amount of the light diffusing agent is less than 0.1 parts by weight, the light diffusibility may be insufficient and the light source may be seen through. On the other hand, if the blending amount of the light diffusing agent exceeds 10 parts by weight, the extrusion moldability may become unstable and the light transmittance of the light diffusing plate may be lowered, making it impossible to obtain the required luminance.

  As a method of making the surface shape of a transparent thermoplastic resin sheet uneven, a method of sandwiching a thermoplastic resin sheet melt-extruded with a cooling roll with a mold having a reverse pattern of a desired pattern on the roll surface, or heat There is a method in which a sheet made of a plastic resin is sandwiched between flat plates having a reverse pattern having a desired pattern on the surface, heated to a temperature higher than the heat distortion temperature, and then pressed.

The thermoplastic resin light diffusion plate of the present invention has a warp rate X ₁ (%) in the range of 0.5 ≦ X ₁ ≦ 10 when heated at 150 ° C. for 10 minutes (projects toward the backlight source). The direction warpage rate is positive). The warpage rate X ₁ (%) is preferably in the range of 0.5 ≦ X ₁ ≦ 6, and more preferably in the range of 0.5 ≦ X ₁ ≦ 3. By installing a light diffusion plate made of a thermoplastic resin having an internal stress such that the warpage fluctuation due to heating is in the above range, on the direct backlight type liquid crystal display device so that the convex direction is on the light source side. The direct-type backlight type liquid crystal display device can be provided in which the light diffusing plate, the light adjusting film and the liquid crystal panel do not come into contact with each other due to the influence of heat from the light source, and there is no luminance unevenness. If the warp rate becomes too large, the stability of the diffusion plate may be inferior during installation or operation of the liquid crystal display device.

The thermoplastic resin light diffusion plate of the present invention, Ri range der warp rate _Y 1 (%) is 0.5 ≦ _{Y 1} ≦ 5 at 23 ° C., a range of 0.5 ≦ _{Y 1} ≦ 3 it is good Mashiku is, more preferably in the range of 0.5 ≦ Y ₁ ≦ 2. Here, Y ₁ is the direction of the warp factor which is convex to the backlight source side is positive. Within such a range, the light diffusing plate, the light adjusting film and the liquid crystal panel are not in contact with each other even in the initial state. If the warp rate becomes too large, the stability of the diffusion plate may be inferior during installation or operation of the liquid crystal display device.
Furthermore, the range of 1 ≦ X ₁ + Y ₁ ≦ 9 is preferable, the range of 1 ≦ X ₁ + Y ₁ ≦ 6 is more preferable, and the range of 1 ≦ X ₁ + Y ₁ ≦ 5 is further preferable.

The thermoplastic resin light diffusion plate, light layer Ru light diffusion plate der stacked on the backlight light source.

Further, the present invention provides a thermoplastic resin light diffusion plate, light layer is laminated on one surface thereof, and the warp ratio when heated for 10 minutes at 150 ℃ X _{2 (%)} is 0.5 ≦ X ₂ There is provided a thermoplastic resin light diffusion plate characterized by being in the range of ≦ 10 (the warpage rate in the direction of convexing the light-resistant layer is positive). The warpage rate X ₂ (%) is preferably in the range of 0.5 ≦ X ₂ ≦ 6, and more preferably in the range of 0.5 ≦ X ₁ ≦ 3. By installing a light diffusion plate made of a thermoplastic resin having an internal stress such that the warpage fluctuation due to heating is in the above range, on the direct backlight type liquid crystal display device so that the convex direction is on the light source side. The direct-type backlight type that does not contact the light diffuser plate with the light control film and the liquid crystal panel due to the heat of the light source, suppresses the influence of the ultraviolet light of the light source, and does not have uneven brightness, and the change in color tone of the image is small A liquid crystal display device can be provided. If the warp rate becomes too large, the stability of the diffusion plate may be inferior during installation or operation of the liquid crystal display device.

The thermoplastic resin light diffusion plate of the present invention, Ri range der warp ratio _Y 2 (%) is 0.5 ≦ _{Y 2} ≦ 5 at 23 ° C., a range of 0.5 ≦ _{Y 2} ≦ 3 it is good Mashiku is, more preferably in the range of 0.5 ≦ Y ₁ ≦ 2. Here, Y ₂ is the direction of the warp factor which is convex in light layer and positive. Within such a range, the light diffusing plate, the light adjusting film and the liquid crystal panel are not in contact with each other even in the initial state. If the warp rate becomes too large, the stability of the diffusion plate may be inferior during installation or operation of the liquid crystal display device.
Furthermore, the range of 1 ≦ X ₂ + Y ₂ ≦ 9 is preferable, the range of 1 ≦ X ₁ + Y ₁ ≦ 6 is more preferable, and the range of 1 ≦ X ₁ + Y ₁ ≦ 5 is further preferable.

  As a method for producing a light diffusion plate made of a thermoplastic resin having an internal stress applied in a specific direction according to the present invention, it can be produced by a method of obtaining a thermoplastic resin sheet by a melt extrusion method. Specifically, in the sheet molding machine using the horizontal three-roll system shown in FIG. 2, the temperature of the melt-extruded thermoplastic resin sheet is controlled by controlling the first to third cooling rolls and the preheater around the first and third cooling rolls. An internal stress in the direction can be applied. In particular, the temperature control of the second cooling roll and the third cooling roll is important. The lower the temperature of the second cooling roll, the higher the warpage rate with the convex bottom surface, and the lower the temperature of the third cooling roll, the upper surface. Since the warpage rate with the convex shape becomes higher, a light diffusion plate made of a thermoplastic resin having a desired warpage rate can be manufactured by adjusting the balance.

Specifically, the temperature (T ₁ ° C.) of the first cooling roll is (Tg−33) ≦ T ₁ ≦ (Tg−27), the second transition temperature (Tg) of the thermoplastic resin used. The temperature (T ₂ ° C) of the second cooling roll is (Tg−35) ≦ T ₂ ≦ (Tg−29), and the temperature (T ₃ ° C) of the third cooling roll is (Tg−8) ≦ T ₃ ≦ (Tg−). By controlling to 3) and 22 ≦ (T ₃ −T ₂ ) ≦ 30, the diffusion plate having the specific warpage rate of the present invention can be stably manufactured.

  As a light-resistant layer that is preferably laminated on the light source side for the purpose of preventing luminance deterioration and color tone change due to light of a thermoplastic resin light diffusion plate, a thickness of 0.1 to 50% by weight of an ultraviolet absorber is contained. A 500 μm organic polymer film is preferred.

  The organic polymer constituting the light-resistant layer is composed of any resin that is transparent, and the resin is preferably an acrylic resin, a polycarbonate resin, a polyethylene resin, or a polyester resin, and more preferably an acrylic resin or a polycarbonate resin. preferable.

  Acrylic resin is a resin obtained by polymerizing acrylic monomers. Examples of acrylic monomers include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl. Methacrylate, 2-ethylhexyl methacrylate, phenyl methacrylate and the like can be used alone or in combination.

  Examples of the polyester resin include polyethylene terephthalate resin, polybutylene terephthalate resin, and polyethylene naphthalate resin. Polyester elastomers can also be used.

  The light-resistant layer is made of any resin having ultraviolet absorption performance. The light-resistant layer preferably contains at least one ultraviolet absorber selected from the group consisting of benzophenone-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, and benzoxazine-based ultraviolet absorbers. Specific examples of these ultraviolet absorbers are the same as those described later. The concentration of the ultraviolet absorber in the light-resistant layer is preferably 0.1 to 50% by weight, more preferably 0.5 to 40% by weight, and further preferably 1 to 30% by weight.

  As a method of laminating a light-resistant layer on a thermoplastic resin sheet as a base material of a light diffusion plate, a laminate in which an organic polymer composition for forming a light-resistant layer is melt-extruded from a T-die on an extruded thermoplastic resin sheet. Method, a method of laminating a light-resistant layer previously formed into a film shape on the surface of a sheet using a heating roll in the course of the production process of the thermoplastic resin sheet, an organic polymer that forms the thermoplastic resin sheet and the light-resistant layer Co-extrusion method in which the composition is melt-extruded and laminated at the same time, thermoplasticity by coating methods such as dip coating method, flow coating method, roll coating method using paint containing organic polymer composition that forms light-resistant layer Lamination is carried out by a method of coating on a resin sheet or a method of transferring a transfer foil having a light-resistant layer on a thermoplastic resin sheet. The method and the like.

  As the transfer foil, one having a multilayer structure comprising a base film / release layer / protective layer / ultraviolet absorber-containing resin layer (the above light-resistant layer) / adhesive layer is preferably used. The transfer foil adhesive layer is adhered to the thermoplastic resin sheet and attached, the release layer is peeled off, and the adhesive layer / ultraviolet absorber-containing resin layer (the above light-resistant layer) / protective layer is formed on the thermoplastic resin sheet from the sheet side. A transferred light diffusion plate for direct type backlight can be obtained.

  When the laminating method and the coextrusion method are employed as a method for laminating the light-resistant layer on the thermoplastic resin sheet, the resin used for forming the light-resistant layer is preferably a thermoplastic resin, and among the thermoplastic resins, an acrylic resin is used. Or it is preferable that it is a polycarbonate resin.

  Further, when a coating method is employed as a method for laminating a light-resistant layer on a thermoplastic resin sheet, a thermoplastic resin or a thermosetting resin is preferably used as a material used for forming the light-resistant layer. Among the thermoplastic resins, an acrylic resin or a polycarbonate resin is preferable. Moreover, as a thermosetting resin, a melamine resin, a silicone resin, an acrylic resin, etc. are preferable.

  Furthermore, when a transfer foil is employed as a method of laminating a light-resistant layer on a thermoplastic resin sheet, it is easy to make the light-resistant layer a thin film, and an acrylic resin is preferably used as a material for forming the light-resistant layer Adopted.

  The thickness of the light-resistant layer is preferably in the range of 1 to 500 μm, more preferably in the range of 1 to 100 μm, and still more preferably in the range of 2 to 70 μm. Especially, in the case of the lamination method or the coextrusion method, the range of 10-500 micrometers is preferable and the range of 20-100 micrometers is more preferable. Moreover, when using a coating method or transfer foil, the range of 1-20 micrometers is preferable and the range of 1-10 micrometers is more preferable. In particular, when a transfer foil is used, a range of 1 to 5 μm is preferable. Further, it is preferable that the light-resistant layer is a thin film because a problem of warpage due to a difference in thermal shrinkage between the thermoplastic resin sheet and the light-resistant layer and a difference in water absorption rate is less likely to occur.

  By including an ultraviolet absorber in the light-resistant layer, it is possible to effectively suppress deterioration of the resin of the thermoplastic resin light diffusion plate due to light from the backlight light source, and to prevent a decrease in luminance and a change in color tone. is there. Since deterioration of the resin of the thermoplastic resin light diffusion plate due to light from the backlight light source proceeds from the surface of the light diffusion plate on the backlight light source side, it is preferable to increase the density of the ultraviolet absorber on the surface.

<Thermoplastic resin sheet>
In the present invention, as the thermoplastic resin of the thermoplastic resin sheet used as the base material of the light diffusion plate for the direct type backlight, the glass transition point is a resin having a heat resistance of 20 ° C. or higher than the actual use temperature, Specifically, a polycarbonate resin is used because it is excellent in heat resistance and water absorption. Hereinafter, the polycarbonate resin that is used will be described.

  The polycarbonate resin suitably used in the present invention is usually obtained by reacting a dihydric phenol and a carbonate precursor by an interfacial polymerization method or a melt polymerization method. Representative examples of dihydric phenols include 2,2-bis (4-hydroxyphenyl) propane (commonly called bisphenol A), 2,2-bis {(4-hydroxy-3-methyl) phenyl} propane, 2,2 -Bis (4-hydroxyphenyl) butane, 2,2-bis (4-hydroxyphenyl) -3-methylbutane, 2,2-bis (4-hydroxyphenyl) -3,3-dimethylbutane, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, 9,9- Bis {(4-hydroxy-3-methyl) phenyl} fluorene and α, α'-bis (4-hydroxyphenyl) -m-diisopropylbenzene 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 polycarbonate resin by reacting the above dihydric phenol and carbonate precursor by interfacial polymerization method or melt polymerization method, a catalyst, a terminal terminator, a dihydric phenol antioxidant, etc. are used as necessary. May be. 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 usually 15,000 to 40,000, preferably 18,000 to 35,000, expressed as a viscosity average molecular weight. 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)

<Additives blended in thermoplastic resin sheet>
The thermoplastic resin sheet used in the present invention has other components such as fluorescent brightener, phosphorous acid, phosphoric acid, phosphorous ester, phosphoric acid as long as the purpose and effect are not impaired in addition to the above components. Heat stabilizers such as esters and phosphonic acid esters, mold release agents such as fatty acid ester compounds, UV absorbers, bluing agents, tetrabromobisphenol A, tetrabromobisphenol A low molecular weight polycarbonate, and decabromodiphenylene ether Additives such as flame retardants and flame retardant aids such as antimony trioxide may be added as required.

  A fluorescent whitening agent can be blended in the thermoplastic resin sheet. The fluorescent whitening agent has an effect of improving the color tone of the resin to white or bluish white and improving the luminance of the light diffusion plate of the present invention. Examples of the fluorescent brightener include stilbenzene, 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 optical brightener is preferably 0.0005 to 0.1 parts by weight, more preferably 0.001 to 0.1 parts by weight, and still more preferably 0.005 parts by weight with respect to 100 parts by weight of the thermoplastic resin. It is 001-0.05 weight part, Most preferably, it is 0.002-0.02 weight part. 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 unevenness in the color tone (hue).

  In the thermoplastic resin sheet used in the present invention, a phosphorus-containing heat stabilizer can be used in order to prevent a decrease in molecular weight and a deterioration in hue during molding. 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, 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′-biphenylenediphosphonite, tetrakis (2,4-di-n-butylphenyl) -4,4′-biphenylenediphosphonite, tetrakis ( 2,4-di-tert-butylphenyl) -4,4′-biphenylenediphosphonite, tetrakis (2,4-di-tert-butylphenyl) -4,3′-biphenylenediphosphonite, tetrakis (2, 4-di-tert-butylphenyl) -3,3′-biphenylenediphosphonite, tetrakis (2,6-di-iso-propylphenyl) -4,4′-biphenylenediphosphonite, tetrakis (2,6- Di-n-butylphenyl) -4,4′-biphenylenediphosphonite, tetrakis (2,6-di-tert-butylphenyl) -4,4 '-Biphenylenediphosphonite, tetrakis (2,6-di-tert-butylphenyl) -4,3'-biphenylenediphosphonite, tetrakis (2,6-di-tert-butylphenyl) -3,3'- Biphenylene diphosphonite, bis (2,4-di-tert-butylphenyl) -biphenyl phosphonite, benzene phosphonate dimethyl, benzene phosphonate diethyl, benzene phosphonate dipropyl, etc., among others, tris (2,4- Di-tert-butylphenyl) phosphite, distearyl pentaerythritol diphosphite, trimethyl phosphate, tetrakis (2,4-di-tert-butylphenyl) -4,4′-biphenylenediphosphonite and bis (2,4 -Di-tert-butylphenyl) -biphenylpho Suphonite 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 0.5 parts by weight with respect to 100 parts by weight of the thermoplastic resin.

In the thermoplastic resin sheet used in the present invention, a fatty acid ester compound can be used for the purpose of improving the releasability 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 Rate, etc. Among them, 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 thermoplastic resin.

  The thermoplastic resin sheet used in the present invention can contain an ultraviolet absorber for the purpose of improving light resistance. Examples of UV absorbers include benzophenone UV absorbers, triazine UV absorbers, benzotriazole UV absorbers, and cyclic imino ester UV absorbers. These UV absorbers may be used alone or in combination of two or more. Also good.

  Specifically, as the ultraviolet absorber, in the benzophenone series, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2-hydroxy-4-benzyloxybenzophenone, 2-hydroxy-4-methoxy-5-sulfoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfoxytrihydridolate benzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2 ', 4 4'-tetrahydroxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxy-5-sodiumsulfoxybenzophenone, bis (5-benzoyl- 4-hydroxy-2-methoxy Phenyl) methane, 2-hydroxy -4-n-dodecyloxy benzophenone, 2-hydroxy-4-methoxy-2'-carboxy benzophenone, and the like. Examples of the triazine ultraviolet absorber include 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5-hexyloxyphenol.

  In the benzotriazole system, 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-3,5-di-tert-butylphenyl) benzotriazole, 2- (2-hydroxy-3,5 -Di-tert-butylphenyl) -5-chlorobenzotriazole, 2- (2-hydroxy-3,5-di-t rt-amylphenyl) benzotriazole, 2- (2-hydroxy-5-tert-octylphenyl) benzotriazole, 2- (2-hydroxy-5-tert-butylphenyl) benzotriazole, 2- (2-hydroxy-4 -Octoxyphenyl) benzotriazole, 2,2'-methylenebis (4-cumyl-6-benzotriazolephenyl), 2,2'-p-phenylenebis (1,3-benzoxazin-4-one), 2- [2-hydroxy-3- (3,4,5,6-tetrahydrophthalimidomethyl) -5-methylphenyl] benzotriazole.

  In the cyclic imino ester system, 2,2′-p-phenylenebis (3,1-benzoxazin-4-one), 2,2 ′-(4,4′-diphenylene) bis (3,1-benzoxazine- 4-one), 2,2 ′-(2,6-naphthalene) bis (3,1-benzoxazin-4-one).

  Preferably, 2-hydroxy-4-n-octoxybenzophenone, 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5-hexyloxyphenol, 2- (2-hydroxy- 5-tert-octylphenyl) benzotriazole, 2- (2-hydroxy-3,5-dicumylphenyl) phenylbenzotriazole, 2- (2-hydroxy-3-tert-butyl-5-methylphenyl) -5 Chlorobenzotriazole, 2,2′-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol], 2,2′-p-phenylene Bis (3,1-benzoxazin-4-one), more preferably 2-hydroxy-4-n-octoxybenzophenone, 2 (4,6-diphenyl-1,3,5-triazin-2-yl) -5-hexyloxyphenol, 2- (2-hydroxy-5-tert-octylphenyl) benzotriazole, 2,2'-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol], 2,2′-p-phenylenebis (3,1-benzoxazine-4 -ON).

  The blending amount of the ultraviolet absorber is preferably 0.01 to 1 part by weight, more preferably 0.05 to 0.8 part by weight with respect to 100 parts by weight of the thermoplastic resin.

  When the thermoplastic resin sheet used in the present invention is formed into a light diffusing plate, it is blue within a range that does not cause an optical loss in order to counteract the yellowness of the light diffusing plate based on a thermoplastic resin or an ultraviolet absorber. Ingredients can be blended. Any bluing agent can be used without any problem as long as it is used for thermoplastic resins. In general, anthraquinone dyes are preferred because they are readily available.

Specific examples of the bluing agent include, for example, the general name Solvent Violet 13 [CA.No (Color Index No) 60725; trade name “Macrolex Violet B” manufactured by Bayer, “Diaresin Blue G” manufactured by Mitsubishi Chemical Corporation, “Sumiplast Violet B” manufactured by Sumitomo Chemical Co., Ltd., generic 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 Co., Ltd., generic name: Solvent Blue 94 [CA.No 61500; Trade name: “Diaresin Blue N” manufactured by Mitsubishi Chemical Co., Ltd.], generic name: Solvent Violet 36 [CA. No 68210; Standard name “Macrolex Violet 3R” manufactured by Bayer AG, generic name Solvent Blue97 [trade name “Macrolex Violet RR” manufactured by Bayer AG] and generic name Solvent Blue45 [CA.No 61110; Blue RLS "]" is a typical example. These bluing agents are usually blended at a ratio of 0.1 × 10 ^{−4 to} 6 × 10 ⁻⁴ parts by weight per 100 parts by weight of the thermoplastic resin.

  The light diffusion plate made of the thermoplastic resin of the present invention has a stable surface light-emitting property by suppressing warpage of the resin to the liquid crystal surface side due to water absorption and drying difference by the internal stress of the resin, and uneven luminance of the light emitting surface. Therefore, the present invention is particularly suitable for a light diffusing plate of a direct backlight type of a large liquid crystal display or a large liquid crystal television of 20 to 50 inches, and the industrial effect brought about by the present invention is exceptional.

  The following examples further illustrate the present invention. The evaluation method is as follows.

(1) Warpage rate A sample of 500 mm square with the light diffusing plate left at 23 ° C. for 24 hours and a central part of one side sandwiched between clips and left in the air for 10 minutes and then left at 23 ° C. for 24 hours. A 500 mm square sample was prepared. Each light diffusing plate was suspended vertically at the center of one side L (mm), and a straight ruler was applied parallel to the side. The straight ruler was applied to the concave surface of the light diffusing plate, and the distance between the straight ruler and the light diffusing plate was measured to the 1 mm unit with a metal straight scale. The other sides were also measured sequentially, and the largest distance was taken as the maximum warp D (mm), and the warpage rate W ₁₀₀₀ with respect to 1000 mm was determined by the following formula (conforming to JIS K6911). In addition, about the curvature rate, the case where it convexed to the light-resistant layer side was displayed as positive. The warpage rate W ₁₀₀₀ (%) when treated at 150 ° C. for 10 minutes is represented by X (%) in Table 1, and the warpage rate W ₁₀₀₀ (%) at 23 ° C. is represented by Y (%) in Table 1. .
W ₁₀₀₀ = (D _1000/1000 ) × 100 (%)
D ₁₀₀₀ = D × 1000 ² / L ²
(L (mm): the length of the portion of the measuring plate where the straight ruler is applied)

(2) Warpage fluctuation A 17-inch direct-type backlight unit in which six cold cathode tubes having a light energy of 5300 Cd / cm ² are arranged at an equal interval of 2.5 cm is installed so that the screen portion is vertical. The light diffusing plate (230 mm long and 320 mm wide) having the warp rate described in Table 1 exposed for 168 hours in an atmosphere of 85 ° C. and 95% RH is backed at the position where the distance from the cold cathode tube is 30 mm. Built in the light side. Furthermore, a 1.0 mm clearance is provided outside the light diffusion plate (opposite the backlight side), and a 1.5 mm thick glass (length: 235 mm, width: 325 mm) with a 5 mm diameter hole at one central portion. It was set as the state kept sealed. The distance between the glass and the diffusion plate at this time was measured (initial value). Thereafter, the cold cathode tube was continuously turned on, and the fluctuation amount (mm) of the light diffusing plate up to 5 hours was measured with a dial gauge in units of 0.1 mm to obtain the maximum fluctuation amount (see FIG. 1). In addition, the case where it became convex on the backlight side was shown as positive, and the case where it became convex on the glass side was shown as negative.

(3) Luminance unevenness In the backlight unit used in (2) above, a liquid crystal panel is installed under the same clearance conditions instead of glass before and after the test of the light diffusing plate, the backlight is turned on, and the white light is turned on. The appearance of the liquid crystal panel over time was evaluated. The case where the liquid crystal part was pushed up by the light diffusing plate and interference fringes were generated was indicated as x, and the case where no abnormality was observed in the appearance was indicated as ◯.

[Example 1]
To 100 parts by weight of a polycarbonate resin (Tg; 145 ° C.) having a viscosity average molecular weight of 24,300 obtained from bisphenol A and phosgene, infusible acrylic polymer fine particles [Paraloid EXL-5136, manufactured by Rohm and Hers Company, weight Average particle diameter 7 μm] 3.5 parts by weight and fluorescent whitening agent [Kayalite OS manufactured by Nippon Kayaku Kogyo Co., Ltd.] 0.01 parts by weight were added and mixed. The polycarbonate resin was continuously melt-extruded while maintaining a temperature of 300 ° C., a die temperature of 260 to 300 ° C., and a degree of vacuum of the vent portion at 26.6 kPa. Using a horizontal three-roll type sheet molding machine (see FIG. 2), the melt-extruded polycarbonate resin was sandwiched between two pairs of rolls (Q1 and Q2) having a diameter of 300 mm and pressurized at 0.05 MPa. A polycarbonate resin sheet having a thickness of 2 mm and a width of 1,000 mm was obtained under the roll temperature condition described in 1. Further, a light-resistant acrylic film [HBS006 made by Mitsubishi Rayon] having a thickness of 50 μm was thermocompression bonded to one surface (lower surface) of the sheet. The obtained light diffusion plate having the light-resistant layer was cut into a size of 230 mm in length and 320 mm in width and evaluated. The measurement results are shown in Table 1.

[Example 2]
In Example 1, a light diffusing plate was obtained in the same manner as in Example 1 except that the amount of infusible acrylic polymer fine particles was changed to 2.0 parts by weight and the roll temperature conditions shown in Table 1 were used. It was. The obtained light diffusion plate was cut into a size of 230 mm in length and 320 mm in width and evaluated. The measurement results are shown in Table 1.

[Example 3]
In Example 1, except that the blending amount of the infusible acrylic polymer fine particles is changed to 0.5 parts by weight, and the roll temperature conditions shown in Table 1 are used, the thickness is 2 mm and the width is the same as in Example 1. A 1,000 mm polycarbonate resin sheet was obtained. Further, a light-resistant transfer foil film (Oike Industrial 25-PUVS, light-resistant layer (acrylic layer) thickness 2.0 μm) was thermocompression bonded to one surface (lower surface) of the sheet. Subsequently, the release layer was peeled off to obtain a light diffusion plate having a light resistant layer. The obtained light diffusion plate was cut into a size of 231 mm in length and 321 mm in width and evaluated. The measurement results are shown in Table 1.

[Example 4]
In Example 3, 0.3 parts by weight of a cross-linked silicone resin [Toshiba Silicone Tospearl 120, weight average particle size 2 μm] was added instead of 0.5 parts by weight of the infusible acrylic polymer fine particles. A light diffusing plate having a light-resistant layer was obtained in the same manner as in Example 3 except that a polycarbonate resin sheet having a thickness of 3 mm was obtained as the roll temperature condition. The obtained light diffusion plate was cut into a size of 231 mm in length and 321 mm in width and evaluated. The measurement results are shown in Table 1.

[Example 5]
To 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 crosslinked silicone resin [TOSHIBA Silicone Tospearl 120, weight average particle size 2 μm] and a fluorescent whitening agent [Nipponka Kayalite OS, manufactured by Yakuhin Kogyo Co., Ltd.] was added and mixed in an amount of 0.01 parts by weight. Using a T-die extruder with a vent, the extruder temperature was 250-300 ° C., the die temperature was 260-300 ° C., and the degree of vacuum in the vent was 26. While holding at 6 kPa and melting, supplying light-resistant acrylic resin (Acrypet IRS404 K001 manufactured by Mitsubishi Rayon) to the auxiliary extruder, melting at an extruder temperature of 250 to 300 ° C., via a feed block and a T-die The thickness of the light-resistant layer is 100 μm, the thickness of the polycarbonate resin sheet is 2 mm, and the width is 1,000 mm. The (polycarbonate resin light diffusion plate having a light layer) was coextruded. The obtained light diffusion plate was cut into a size of 231 mm in length and 321 mm in width and evaluated. The measurement results are shown in Table 1.

[Comparative Example 1]
In Example 1, the light diffusing plate was obtained by the same method as Example 1 except having changed into the roll temperature conditions of Table 1. The obtained light diffusion plate was cut into a size of 230 mm in length and 320 mm in width and evaluated. The measurement results are shown in Table 1.

[Comparative Example 2]
In Example 2, the light diffusing plate was obtained by the same method as Example 2 except having changed into the roll temperature conditions of Table 1. The obtained light diffusion plate was cut into a size of 230 mm in length and 320 mm in width and evaluated. The measurement results are shown in Table 1.

[Comparative Example 3]
In Example 4, a light diffusion plate having a thickness of 2 mm was obtained in the same manner as in Example 4 except that the amount of the crosslinked silicone resin was changed to 0.8 parts by weight and the roll temperature conditions shown in Table 1 were used. . The obtained light diffusion plate was cut into a size of 231 mm in length and 321 mm in width and evaluated. The measurement results are shown in Table 1.

In addition, the transparent fine particles A and B and the weather resistant layers C, D and E used in Table 1 are as follows.
Transparent fine particles A: Infusible acrylic polymer fine particles [Paraloid EXL-5136, manufactured by Rohm & Hers Company, weight distribution average particle size 7 μm]
Transparent fine particle B: cross-linked silicone resin [TOSHIBA Silicone Tospearl 120, weight average particle size 2 μm]
Light-resistant layer C: Weather-resistant acrylic laminate film [Mitsubishi Rayon HBS006 layer thickness 50 μm]
Light resistant layer D: Weather resistant transfer foil film [Oike Industrial 25-PUVS layer thickness 2 μm]
Light-resistant layer E: Coextruded layer [Mitsubishi Rayon IRS404 K001 Layer thickness 100 μm]

It is a simplification figure of the evaluation apparatus for measuring the curvature fluctuation | variation of the light diffusing plate in the Example of this invention. It is a simplified diagram of a melt extrusion device for producing a light diffusion plate of the present invention.

Explanation of symbols

1. Glass 2. Diffusion plate Dial gauge Cold Cathode Tube A. Dice C.I. Heater D. Rubber roll E. Light-resistant film Q ₁ . First cooling roll Q ₂ . Second cooling roll Q ₃ . Third cooling roll

Claims (4)

(I) A light-resistant layer is laminated on one side , and (ii) the warpage rate X ₂ (%) when heated at 150 ° C. for 10 minutes is in the range of 0.5 ≦ X ₂ ≦ 10 (convex to the light-resistant layer side) (Iii) warp rate Y ₂ (%) at 23 ° C. is in the range of 0.5 ≦ Y ₂ ≦ 5 (warp in the direction of convex toward the light-resistant layer) The method of manufacturing a polycarbonate resin light diffusing plate, wherein the light diffusing plate has a temperature of the polycarbonate resin sheet melt-extruded in a horizontal three-roll sheet forming machine. With respect to the next transition temperature (Tg), the temperature (T ₁ ° C) of the first cooling roll is (Tg-33) ≤T ₁ ≤ (Tg-27), and the temperature (T ₂ ° C) of the second cooling roll is ( Tg−35) ≦ T ₂ ≦ (Tg−29), the temperature of the third cooling roll (T ₃ ° C.) to _{(Tg-8) ≦ T 3} ≦ (Tg-3), and 22 ≦ _(T 3 -T ₂₎ is produced by controlling the range of ≦ 30, the manufacturing method of the light diffusion plate. The method for producing a light diffusing plate according to claim 1, wherein the polycarbonate resin is a bisphenol A type polycarbonate resin. The said light diffusing plate is a manufacturing method of the light diffusing plate of Claim 1 containing 0.1-10 weight part of light diffusing agents with respect to 100 weight part of polycarbonate resin. The said light diffusing plate is a manufacturing method of the light diffusing plate of Claim 1 containing 0.0005 to 0.1 weight part of fluorescent whitening agents with respect to 100 weight part of polycarbonate resin.

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