JP2009199002A - Laminated film for diffusion sheet, diffusion sheet and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a luminance improving characteristic in addition to anti-sticking and Newton's ring preventive functions. <P>SOLUTION: The diffusion sheet 15 includes: a support 11 made of polyester; an easily bonding layer 12 formed on one surface of the support 11; a back layer 13 formed on the other surface of the support 11; and a diffusion layer 14 formed on the easily bonding layer 12. The easily bonded layer 12 includes a compound having a plurality of carbodiimide structures. The back layer 13 has an average reflectance of 3.5% or less to light having a wavelength of 380-780 nm. Since the easily bonding layer 12 includes a compound having a plurality of carbodiimide structures, the adhesion to the diffusion layer 14 is improved. The average reflectance of the back layer is thus set to 3.5% or less, whereby the luminance improving characteristic can be obtained in addition to anti-sticking and Newton's ring preventive functions. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a diffusion sheet laminated film, a diffusion sheet, and a display device that are suitably used as a diffusion sheet member for a liquid crystal display.

  Polyester films, particularly biaxially oriented polyester films, are widely used as various optical films because of their excellent transparency, dimensional stability, chemical resistance, and low moisture absorption. For example, in a liquid crystal display, it is used for base films such as a prism sheet, an antireflection sheet, a light diffusion sheet, and a hard coat sheet. Further, in plasma displays, they are used for base films such as IR absorbing sheets, electromagnetic wave shielding sheets, toning sheets, antireflection sheets, antiglare sheets, and hard coat sheets.

  In the use of a diffusion sheet for a liquid crystal display, a diffusion layer formed of a thermosetting resin or an ultraviolet curable resin is provided on one side of a polyester film. This diffusion layer is required to have adhesiveness with a polyester film. Recently, in order to improve the yield, UV curable resin type diffusion layers imparted with scratch resistance are often seen. Generally, when a diffusion layer is provided directly on a polyester film, good adhesion cannot be obtained. Therefore, a coating solution called an easy adhesion layer is provided on a polyester film, and a diffusion layer can be applied thereon. Has been done. For example, Patent Document 1 describes an easy-adhesion layer using polyester as a binder, and Patent Document 2 describes an easy-adhesion layer using polyester and urethane as a binder.

On the side opposite to the diffusion layer, a sticking prevention layer, a Newton ring (interference fringe) prevention layer, or the like can be provided. In order to prevent sticking or Newton's ring, it is known as a known technique to install a back surface layer in which fine particles of about 1 μm to 50 μm are added to a binder resin layer having a film pressure of about 1 μm to 10 μm (patent document) (See 3 and 4)
JP 2001-294826 A JP 2000-229395 A JP 2000-89007 A JP 2005-77448 A

  In the back surface layers shown in Patent Documents 3 and 4 above, the anti-sticking and Newton ring prevention functions can be obtained, but since the thickness of the binder resin layer is as thick as 1 μm or more, the surface reflectance of the back surface layer depends on the refractive index of the binder resin. It will be decided. That is, due to the relatively high back surface reflectance, the transmittance of the backlight light cannot be sufficiently improved, and a sufficient brightness enhancement effect cannot be obtained.

  The present invention has been made to solve the above-described problems, and provides a diffusion sheet laminated film, a diffusion sheet, and a display device that can obtain brightness enhancement characteristics in addition to the anti-sticking and Newton ring prevention functions. For the purpose.

  In order to achieve the above object, a laminated film for a diffusion sheet according to the present invention includes a support made of biaxially stretched polyester, and an easy-to-contain compound provided on one surface of the support and having a plurality of carbodiimide structures. It has an adhesive layer and a back layer provided on the other surface of the support and having an average reflectance of 3.5% or less with respect to light having a wavelength of 380 nm to 780 nm.

  The back layer is composed of one or more layers, and the refractive index n of the outermost layer in contact with air among the one or more layers is 1.20 to 1.51, and the film thickness of the outermost layer is (550 / (4n)) It is preferably within the range of ± 40 nm. The back layer is composed of a plurality of layers, and it is preferable to add matting agent particles to a first layer in contact with the support among the plurality of layers. It is preferable that the easy-adhesion layer and the back layer are provided after biaxially stretching the support.

  The diffusion sheet of the present invention is characterized in that a diffusion layer is provided on the easy-adhesion layer of the film for diffusion sheet described in the above item. The display device of the present invention is equipped with the laminated film for a diffusion sheet described above.

  According to the present invention, an easy-adhesion layer containing a compound having a plurality of carbodiimide structures is provided on one surface of the support, and the back surface has an average reflectance of 3.5% or less for light having a wavelength of 380 nm to 780 nm. By providing the layer on the other surface of the support, it is possible to obtain brightness enhancement characteristics in addition to the anti-sticking and Newton ring prevention functions.

  As shown in FIG. 1, a laminated film 10 for a diffusion sheet according to the present invention is formed on a support 11, an easy adhesion layer 12 formed on one surface of the support 11, and the other surface of the support 11. And a diffusion layer 14 formed on the easy-adhesion layer 14.

  As shown in FIG. 2, the diffusion sheet 15 of the present invention is configured by forming a diffusion layer 14 on the easy-adhesion layer 12 of the laminated film 10 for diffusion sheet shown in FIG.

[Support]
The support 11 is a polyester base film made of polyester. Polyester is not particularly limited, and polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polybutylene naphthalate, and the like can be used. Among these, polyethylene terephthalate is preferable from the viewpoint of cost and mechanical strength.

  The support 11 is preferably subjected to stretching in order to improve mechanical strength. Biaxially stretched is particularly preferable. Although there is no restriction | limiting in particular in a draw ratio, 1.5-7 times are preferable, More preferably, it is about 2-5 times. In particular, the film is preferably stretched at the same magnification in the vertical and horizontal directions, for example, about 2 to 5 times. If the draw ratio is smaller than this, sufficient mechanical strength cannot be obtained. Conversely, if it is too large, it is difficult to obtain a uniform thickness.

  As for the thickness of the support body 11, 20-400 micrometers is preferable, More preferably, it is 35-350 micrometers, More preferably, it is about 50-250 micrometers. Those having a thickness of less than 20 μm are difficult to handle because they are not elastic, and those having a thickness of more than 400 μm are not only hindering downsizing of the display device, but also are disadvantageous in terms of cost.

[Easily adhesive layer]
The easy-adhesion layer 12 has a two-layer structure including a first layer 12 a that emphasizes easy adhesion to the support 11 and a second layer 12 b that emphasizes easy adhesion to the diffusion layer 14. 20-300 nm is preferable and, as for the film thickness of the easily bonding layer 12 (total film thickness of the 1st layer 12a and the 2nd layer 12b), More preferably, it is about 40-200 nm. If it is less than 20 nm, sufficient adhesion performance with the diffusion layer 14 cannot be obtained, and if it exceeds 300 nm, coloring due to light interference becomes a problem. In the case of providing a scratch-resistant diffusion layer formed of an ultraviolet curable resin or the like as in the present invention, the easy-adhesion layer preferably has the above two-layer structure rather than a single layer.

  The first layer 12 a includes a binder such as a polyester resin having affinity for the support 11. The polyester resin is a general term for polymers having an ester bond in the main chain, and is usually obtained by a reaction of a dicarboxylic acid and a diol. Examples of the dicarboxylic acid include fumaric acid, itaconic acid, adipic acid, sebacic acid, terephthalic acid, and isophthalic acid. Examples of the diol include ethylene glycol, propylene glycol, glycerin, and hexanetriol. The polyester resin and its raw materials are described in, for example, “Polyester resin handbook” (Eiichiro Takiyama, Nikkan Kogyo Shimbun, published in 1988). More preferably, naphthalene dicarboxylic acid is used as the dicarboxylic acid component. By containing a naphthalene ring, the refractive index as a coating layer can be improved, and coloring due to light interference in a two-layer structure can be reduced. Moreover, the effect which prevents the oligomer precipitation of the support body 11 is acquired.

  The second layer 12b includes a binder having affinity for the diffusion layer 14. Since the diffusion layer 14 contains a large amount of acrylic thermosetting resin and ultraviolet curable resin, it is preferable to use an acrylic resin having an affinity for this and a polyurethane resin as a binder for the second layer 12b. Moreover, it is preferable to use a blend of acrylic resin and polyurethane resin as the binder of the second layer 12b.

  An acrylic resin is a polymer containing acrylic acid, methacrylic acid and derivatives thereof as components. Specifically, for example, acrylic acid, methacrylic acid, methyl methacrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, acrylamide, acrylonitrile, hydroxyl acrylate, etc. as main components and monomers copolymerizable therewith (for example, styrene, divinylbenzene) Etc.).

Polyurethane resin is a general term for polymers having a urethane bond in the main chain, and is usually obtained by reaction of polyisocyanate and polyol. Examples of the polyisocyanate include TDI, MDI, NDI, TODI, HDI, and IPDI. Examples of the polyol include ethylene glycol, propylene glycol, glycerin, and hexanetriol.
Furthermore, as the isocyanate of the present invention, a polymer obtained by subjecting a polyurethane polymer obtained by the reaction of polyisocyanate and polyol to chain extension treatment to increase the molecular weight can also be used. The polyisocyanate, polyol and chain extension treatment described above are described in, for example, “Polyurethane Resin Handbook” (edited by Keiji Iwata, Nikkan Kogyo Shimbun, published in 1987).

  As the binder of the first layer 12a and the second layer 12b, the above polymer may be used by dissolving in an organic solvent, or an aqueous dispersion may be used. Moreover, in order to suppress an environmental load, it is preferable to apply water-based coating using an aqueous dispersion. The following commercially available polymers may be used as the aqueous dispersion. Superflex 830, 460, 870, 420, 420NS (Polyurethane from Daiichi Kogyo Seiyaku Co., Ltd.), Hydran AP-40F, WLS-202, HW-140SF (Polyurethane from Dainippon Ink and Chemicals), Olester UD500, UD350 (Mitsui Chemicals Co., Ltd. polyurethane), Jurimer ET325, ET410, SEK301 (Nippon Pure Chemicals Co., Ltd. acrylic), Boncourt R3380E, SFA-33 (Dainippon Ink Chemical Co., Ltd. acrylic), Neokrill XK-12, XK-220 (Enomoto Kasei Co., Ltd. acrylic), Finetex ES650, ES2200 (Dainippon Ink Chemical Co., Ltd. polyester), Vironal MD1400, MD1480 (Toyobo Polyester), plus coat Z-221, Z-561, Z-730, RZ-142, Z-687 (polyester manufactured by Kyoyo Chemical Co., Ltd.).

  Although there is no restriction | limiting in particular in the molecular weight of the polymer used as a binder of the 1st layer 12a and the 2nd layer 12b, The thing of about 2000-1 million is preferable normally in a weight average molecular weight. When the weight average molecular weight is less than 2,000, the strength of the coating layer may be insufficient, and when the weight average molecular weight exceeds 1,000,000, the coated surface may be poor.

  The easy-adhesion layer 12 (the first layer 12a and the second layer 12b) includes a compound having a plurality of carbodiimide structures in the molecule (hereinafter referred to as “carbodiimide compound”). As the carbodiimide compound, any compound having a plurality of carbodiimide groups in the molecule can be used without particular limitation. By containing the carbodiimide compound in the easy adhesion layer 12, not only is the reactivity with the carboxyl group terminal of the polyester film excellent, but also the easy adhesion with the diffusion layer 14 is improved. This is estimated to be due to a decrease in the elastic modulus of the easy-adhesion layer 12.

  Polycarbodiimide is usually synthesized by a condensation reaction of organic diisocyanate. Here, the organic group of the organic diisocyanate used for the synthesis of the compound having a plurality of carbodiimide structures in the molecule is not particularly limited, and either aromatic or aliphatic, or a mixed system thereof can be used. An aliphatic system is particularly preferred from the viewpoint of reactivity.

  As the synthetic raw material, organic isocyanate, organic diisocyanate, organic triisocyanate and the like are used. As examples of organic isocyanates, aromatic isocyanates, aliphatic isocyanates, and mixtures thereof can be used.

Specifically, 4,4′-diphenylmethane diisocyanate, 4,4-diphenyldimethylmethane diisocyanate, 1,4-phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hexamethylene diisocyanate, cyclohexane Diisocyanate, xylylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, 1,3-phenylene diisocyanate, etc. are used. As organic monoisocyanates, isophorone isocyanate, phenyl isocyanate are used. Cyclohexyl isocyanate, butyl isocyanate, naphthyl isocyanate and the like are used.
Moreover, the carbodiimide type compound which can be used for this invention is available as commercial items, such as carbodilite V-02-L2, V-02, V-04 (made by Nisshinbo Co., Ltd.), for example.

  The carbodiimide-based compound is preferably added in the range of 1 to 200% by mass and more preferably in the range of 5 to 100% by mass with respect to the binder of the easy adhesion layer 12. When the addition amount is less than 1% by mass, sufficient easy adhesion cannot be obtained, and when it exceeds 200% by mass, the coated surface state may be deteriorated.

  The easy-adhesion layer 12 contains a matting agent. The matting agent may be either organic or inorganic fine particles. For example, polymer fine particles such as polystyrene, polymethyl methacrylate, silicone resin, and benzoguanamine resin, and inorganic fine particles such as silica, calcium carbonate, magnesium oxide, and magnesium carbonate can be used. Among these, polystyrene, polymethyl methacrylate, and silica are preferable from the viewpoints of improving slipperiness and cost.

  The average particle size of the matting agent added to the easy-adhesion layer 12 is preferably 0.01 to 10 μm, more preferably 0.03 to 5 μm. When the average particle size is less than 0.01 μm, the effect of improving the slipperiness is insufficient, and when it exceeds 10 μm, the display quality of the display device may be deteriorated. Two or more kinds of matting agents having different average particle diameters can be used.

The addition amount of the matting agent varies depending average particle diameter is preferably 0.1 to 30 mg / ^{m 2,} more preferably in the range of 0.5-20 / ^{m 2.} If the amount added is 0.1 mg / m ² or less, the effect of improving slipperiness may be insufficient, and if it exceeds 30 mg / m ² , the display quality of the display device may be deteriorated.

[Back layer]
The back layer 13 is composed of a first layer 13a in contact with the support 11 and an outermost layer 13b formed on the first layer 13a and in contact with the air interface. In the back surface layer 13, it is preferable that the average reflectance with respect to light having a wavelength of 380 nm to 780 nm is 3.5% or less. By setting the average reflectance of the back layer 13 to 3.5% or less, sufficient low reflection performance can be obtained. When the average reflectance of the back layer 13 exceeds 3.5%, sufficient low reflection performance cannot be obtained. The back layer may have a single layer structure, but is preferably composed of a plurality of layers in order to obtain low reflection performance, prevention of sticking, and prevention of Newton rings.

  The refractive index n of the outermost layer 13b is preferably set in the range of 1.20 to 1.51, and more preferably set in the range of 1.28 to 1.50. By setting the refractive index n of the outermost layer 13b within the above range, sufficient low reflection performance can be obtained. It is technically difficult to make the refractive index n less than 1.20. On the other hand, when the refractive index n exceeds 1.51, sufficient low reflection performance cannot be obtained.

  From the viewpoint of preventing reflection in the visible light region centered on light having a wavelength of 550 nm, the thickness of the outermost layer 13b is preferably set within the range of (550 / (4n)) ± 40 nm, (550 / ( 4n)) It is more preferable to set within a range of ± 30 nm. By setting the film thickness of the outermost layer 13b within the above range, sufficient low reflection performance can be obtained without causing coloring. On the other hand, when the film thickness of the outermost layer exceeds (550 / (4n)) + 40 nm, sufficient low reflection performance cannot be obtained in the visible light region (380 nm to 780 nm), and remarkable coloring occurs. On the other hand, when the film thickness of the outermost layer is less than (550 / (4n))-40 nm, sufficient low reflection performance is obtained as in the case where the film thickness of the outermost layer exceeds (550 / (4n)) + 40 nm. In addition to being obtained, significant coloring occurs.

  The film thickness of the first layer 13 is preferably a binder film thickness of 0.1 μm or more and 3.0 μm or less. More preferably, the binder film thickness is 0.3 μm or more and 1.0 μm or less.

  As the binder of the outermost layer 13b of the back layer 13, a low refractive index material is preferable, and an acrylic resin, a polyurethane resin, a polyolefin resin, a fluorine resin, a silicone resin, or the like can be suitably used. In addition, a composite resin of the above resin, for example, a resin having a core / shell structure can be suitably used.

  As the acrylic resin and the polyurethane resin, those that can be used for the binder of the easy-adhesion layer 12 are used, but those that do not contain an aromatic ring or a heterocyclic structure are preferable from the viewpoint of lowering the refractive index.

  A polyolefin resin is a resin containing 50% by mass or more of an olefin-derived structural unit. For example, a homopolymer or copolymer of an olefin such as ethylene or propylene, an olefin mainly composed of ethylene or propylene, and other α -Copolymers of olefins, (multi-component) copolymers of olefins and carboxylic acid-containing monomers such as acrylic acid and maleic acid, carboxylic acid-containing monomers of these polymers, and modified products thereof with anhydrides. Specifically, polyethylene, polypropylene, propylene-ethylene copolymer, propylene-butene copolymer, propylene-ethylene-butene terpolymer, ethylene, propylene, butylene and other olefins and acrylic acid, methacrylic acid, crotonic acid , Copolymers of unsaturated monocarboxylic acids such as isocrotonic acid, unsaturated dicarboxylic acids such as maleic acid, fumaric acid and itaconic acid, and unsaturated carboxylic acid anhydrides such as maleic anhydride, fumaric anhydride and itaconic anhydride Or resins modified with these. These are resins produced by known polymerization methods, polymerization catalysts, and modification methods. Moreover, polyolefin resin is available as commercial products, such as Chemipearl S-120, S75N, M200 (made by Mitsui Chemicals), Hitec S-3121, S-3148 (made by Toho Chemical Co., Ltd.), for example. .

  The binder of the first layer 13a of the back layer 13 is preferably a resin having adhesiveness with the support 11 and showing a refractive index close to the refractive index in the surface direction of the support 11, such as polyester. Resins are preferred. When the refractive index of the first layer 13a is closer to the refractive index in the surface direction of the support 11, the influence of light interference from the interface between the support 11 and the first layer 13a can be reduced, and the lower reflectivity is achieved by the outermost layer 13b. The effect of increases.

  The polyester resin is a general term for polymers having an ester bond in the main chain, and is usually obtained by a reaction of a dicarboxylic acid and a diol. Examples of the dicarboxylic acid include fumaric acid, itaconic acid, adipic acid, sebacic acid, terephthalic acid, and isophthalic acid. Examples of the diol include ethylene glycol, propylene glycol, glycerin, and hexanetriol. The polyester resin and its raw materials are described, for example, in “Polyester Resin Handbook” written by Eiichiro Takiyama, Nikkan Kogyo Shimbun, published in 1988.

  More preferably, naphthalene dicarboxylic acid is used as the dicarboxylic acid component. By including a naphthalene ring, the refractive index as a coating layer can be brought close to the refractive index in the surface direction of the support 11, and the influence of light interference from the interface between the support 11 and the first layer 13a is reduced. And the effect of lowering the reflectance is increased. Moreover, the effect which prevents the oligomer precipitation of the support body 11 is acquired.

  A matting agent is added to the first layer 13 a of the back layer 13. By adding a matting agent, it is possible to prevent sticking and Newton ring. In order to reliably prevent such sticking and Newton ring, the matting agent needs to protrude from the surface of the back layer 13. Therefore, a matting agent may be added to the outermost layer 13b. However, when the matting agent is added to the outermost layer 13b, the matting agent may fall off, so it is preferable to add the matting agent to the first layer 13a in contact with the support 11. .

  By adding a matting agent to the first layer 13a and overcoating the outermost layer 13b with a low refractive index design thereon, sufficient anti-sticking and Newton ring prevention effects can be obtained, and the matting agent can be removed. It can be effectively prevented. Therefore, it becomes possible to reduce the binder resin film thickness of the first layer 13a to which the matting agent is added, which is advantageous in terms of cost.

  As the type of matting agent, both organic and inorganic fine particles can be used. Moreover, you may blend and use both. Examples of the organic fine particles include polystyrene, polymethyl methacrylate, silicone resin, and benzoguanamine resin. Examples of the inorganic fine particles include silica, calcium carbonate, magnesium oxide, and magnesium carbonate. Among these, polystyrene, polymethyl methacrylate, and silica are preferable because they are excellent in the effect of improving slipperiness and are low in cost.

Regardless of the material, the average particle size of the fine particles is preferably 0.3 μm or more and 20 μm or less. More preferably, it is 0.5 μm or more and 15 μm or less. Thereby, the slipperiness can be improved while the fine particles are aggregated to ensure high transparency. Here, if fine particles having an average particle size of less than 0.3 μm are used, the effect of improving the slipperiness is weak, whereas if fine particles having an average particle size of more than 20 μm are used, the transparency is lowered or the display quality is reduced. This is not suitable because it may lead to a decrease in the temperature. The amount of fine particles, varies depending on the average particle diameter, 0.1 mg / ^{m 2} or more 30 mg / ^{m 2} or less, and more preferably 0.5 mg / ^{m 2} or more 20 mg / ^{m 2} or less. Here, if the addition amount of the fine particles is less than 0.1 mg / m ² , the effect of improving the slipping property is weak, whereas if it exceeds 30 mg / m ² , the transparency and the display quality may be deteriorated. There is.

  Here, the particle diameter of the fine particles refers to the diameter of a circle having the same area as the fine particles when the fine particles are photographed with a scanning electron microscope. And an average particle diameter says the average value of the particle diameter calculated | required about arbitrary 50 fine particles.

  The easy-adhesion layer 12 and the back surface layer 13 may contain a surfactant, a crosslinking agent, a slipping agent and the like as necessary.

As the surfactant that can be used for the easy adhesion layer 12 and the back surface layer 13, known anionic, nonionic, and cationic surfactants can be used. The surfactant is described in, for example, “Surfactant Handbook” (Nishi Ichiro, Imai Sachiichiro, Kasai Shozo edited by Sangyo Tosho Co., Ltd., 1960). The amount of the surfactant 0.1 to 30 mg / ^{m 2,} more preferably from 0.2 to 10 mg / ^{m 2.} If the addition amount is less than 0.1 mg / m ² , repelling may occur, and if it exceeds 30 mg / m ² , the surface state may deteriorate.

Examples of the slip agent that can be used for the easy adhesion layer 12 and the back layer 13 include synthetic or natural wax, silicone compound, RO-SO ₃ M (where R is a substituted or unsubstituted alkyl group, and the alkyl group has 3 carbon atoms. To an integer of 20 to M, and M represents a monovalent metal atom).

Specific examples of the slip agent include cellosol 524, 428, 732-B, 920, B-495, hydrin P-7, D-757, Z-7-30, E-366, F-115, D-336, D -337, Polylon A, 393, H-481, Hi-micron G-110F, 930, G-270 (manufactured by Chukyo Yushi Co., Ltd.), Chemipearl W100, W200, W300, W400, W500, W950 (above Mitsui Chemicals ( Co., Ltd.)), etc., KF-412, 413, 414, 393, 859, 8002, 6001, 6002, 857, 410, 910, 851, X-22-162A, X-22-161A, X-22 -162C, X-22-160AS, X-22-164B, X-22-164C, X-22-170B, X-22-800, X-22-819, X-22-820, X-22-821 (Shin-Etsu Chemical Co., Ltd.) and the like, and compounds represented by the above general formulas such as C ₁₆ H ₃₃ —O—SO ₃ Na and C ₁₈ —H ₃₇ —O—SO ₃ Na be able to. These slip agents are preferably 50 mg / ^{m 2} from 0.1, is more preferably in the range of 1 to 20 mg / ^{m 2.} If the amount added is too small, the slipping property may be insufficient. Conversely, if the amount is too large, surface deterioration may occur.

  As a crosslinking agent that can be used for the easy-adhesion layer 12 and the back surface layer 13, a general crosslinking agent such as epoxy, oxazoline, melamine, or isocyanate may be used in addition to the carbodiimide compound.

[Diffusion layer]
The diffusion layer 14 improves the luminance of the screen of the display device by uniformly diffusing the light from the easy adhesion layer 13. The diffusion layer 14 includes a large amount of acrylic thermosetting resin, ultraviolet curable resin, and the like. Specifically, the diffusion layer 14 includes a light diffusion layer coating solution and a crosslinking agent solution having the following composition. Examples of the light diffusion layer coating solution include methyl ethyl ketone, acrylic resin (Acridic A811BE, manufactured by Dainippon Ink and Chemicals, 50% by weight solution, hydroxyl value 17, acid value 3), Jurimer MB-20X (polymethyl methacrylate). Cross-linked organic fine particles, Nippon Pure Chemical Industries, Ltd., spherical fine particles with an average particle size of 18 μm, F780F (Dainippon Ink Chemical Co., Ltd., 30 wt% solution of methyl ethyl ketone) and the like. Examples of the crosslinking agent include methyl ethyl ketone and isocyanate compounds (Takenate D110N, manufactured by Mitsui Takeda Chemical Co., Ltd.).

[Coating method for easy adhesion layer and back layer]
There is no restriction | limiting in particular in the method of coating the easily bonding layer 12 and the back surface layer 13 with respect to the support body 11, For example, well-known methods, such as bar coater application | coating and slide coater application | coating, are used. As the coating solvent, water, toluene, methyl alcohol, isopropyl alcohol, methyl ethyl ketone and the like, and aqueous and organic solvent based coating solvents such as a mixed system thereof can be used. Among these, the method using water as a coating solvent is preferable in view of cost and ease of production.

  Application is performed after biaxial stretching to enable recovery of the ears of the support 11 after lateral stretching. The second layer 12b of the easy adhesion layer 12 may be applied and dried simultaneously with the first layer 12a, or may be applied after the first layer 12a is applied and dried. The first layer 13 a and the outermost layer 13 b of the back layer 13 are also applied in the same manner as the easy-adhesion layer 12.

  In the above embodiment, the easy-adhesion layer has a two-layer structure including a first layer and a second layer. However, the present invention is not limited to this, and a plurality of layers or a single layer may be used. For example, when the easy-adhesion layer is composed of a single layer, as the binder, either the first layer binder or the second layer binder in a two-layer configuration may be used. You may use what blended the binder of the 2nd layer. Even when the easy-adhesion layer is composed of a single layer, it is preferable to contain the carbodiimide compound, matting agent, surfactant, slipping agent and the like shown in the above embodiment.

[Example 1]
The following examples further illustrate the present invention in detail but are not to be construed to limit the scope thereof.

[Support]
A polyethylene terephthalate (hereinafter referred to as “PET”) resin having an inherent viscosity of 0.66 polycondensed using a Ge compound as a catalyst was dried to a moisture content of 50 ppm or less and melted in an extruder at a heater temperature of 280 to 300 ° C. The melted PET resin was discharged from a die part onto a chill roll electrostatically applied to obtain an amorphous base. The obtained amorphous base was stretched 3.1 times in the base traveling direction and then stretched 3.8 times in the width direction to obtain a PET support having a thickness of 188 μm.

[Easily adhesive layer]
One surface of the PET support (surface direction refractive index: 1.66) was subjected to corona discharge treatment, and an easy-adhesion layer first layer coating solution X having the following composition was applied onto the PET support by the bar coating method. . The coating amount was 7.1 cc / m ² and the coating was dried at 185 ° C. for 1 minute. Thereby, the 1st layer of the easily bonding layer was formed.
[First layer coating solution X for easy adhesion layer]
45.1 parts by mass of polyester resin binder (manufactured by Kyoyo Chemical Co., Ltd., plus coat Z-687, solid content 25%)
Compound having a plurality of carbodiimide structures 15.8 parts by mass (Nisshinbo Co., Ltd., Carbodilite V-02-L2, solid content 40%)
7.0 parts by mass of oxazoline compound (Nippon Shokubai Co., Ltd., Epocros K2020E, solid content 40%)
Surfactant A 12.7 parts by mass (Nippon Yushi Co., Ltd., 1% aqueous solution of Lapisol B-90, anionic)
Surfactant B 15.5 parts by mass (Sanyo Chemical Industry Co., Ltd., 1% aqueous solution of NAROACTY CL-95, nonionic)
Add distilled water to 1000 parts by mass

Subsequent to the formation of the first layer of the easy adhesion layer, a corona discharge treatment was performed on the first layer. And the 2nd layer coating liquid Y for easily bonding layers which consists of the following composition was apply | coated by the bar-coat method. The coating amount was 7.1 cc / m ² and the coating was dried at 165 ° C. for 1 minute. Thereby, the 2nd layer of the easily bonding layer was formed.
[Second layer coating liquid Y for easy adhesion layer]
22.8 parts by mass of polyurethane resin binder (manufactured by Mitsui Chemicals, Olester UD-350, solid content 38%)
2.6 parts by mass of acrylic resin binder (manufactured by Daicel Chemical Industries, EM48D, solid content 27.5%)
Compound having a plurality of carbodiimide structures 4.7 parts by mass (Nisshinbo Co., Ltd., Carbodilite V-02-L2, solid content 40%)
Surfactant A 12.7 parts by mass (manufactured by NOF Corporation, 1% aqueous solution of Lapisol B-90, anionic)
Surfactant B 15.5 parts by mass (manufactured by Sanyo Chemical Industries, 1% aqueous solution of NAROACTY CL-95, nonionic)
Silica fine particle dispersion 1.6 parts by mass (manufactured by Nippon Aerosil Co., Ltd., water dispersion of Aerosil OX-50, solid content 10%)
Colloidal silica 3.5 parts by mass (manufactured by Nissan Chemical Industries, Snowtex XL, solid content 40.5%)
Sliding agent 1.6 parts by mass (manufactured by Chukyo Yushi Co., Ltd., carnauba wax dispersion cellosol 524 solid content 30%)
Add distilled water to 1000 parts by mass

[Back layer]
After forming an easy-adhesion layer on one side of the PET support, a back layer coating solution A having the following composition was applied to the other side by a bar coating method. The coating amount was 8.9 cc / m ² and dried at 180 ° C. for 1 minute. Thereby, the 1st layer of the back surface layer was formed in the opposite side to the surface in which the easily bonding layer was formed.
[Back surface layer coating liquid A]
213.9 parts by mass of polyester resin binder (manufactured by Kyoyo Chemical Co., Ltd., plus coat Z-687, containing naphthalene ring, Tg = 110 ° C., solid content 25%)
Compound having a plurality of carbodiimide structures 26.2 parts by mass (Nisshinbo Co., Ltd., Carbodilite V-02-L2, solid content 40%)
Surfactant A 17.4 parts by mass (Nippon Yushi Co., Ltd., 1% aqueous solution of Lapisol B-90, anionic)
Surfactant B 42.9 parts by mass (Sanyo Chemical Industry Co., Ltd., NAROACTY CL-95 1% aqueous solution, nonionic)
Matting agent 0.8 part by mass (manufactured by Soken Chemical Co., Ltd., cross-linked PMMA particles MX-501α, average particle size 5.4 μ)
Add distilled water to 1000 parts by mass

Next, after forming the first layer of the back layer, a corona discharge treatment was performed on the first layer of the back layer, and a back layer coating solution B having the following composition was applied by a bar coating method. The coating amount was 7.1 cc / m ² and the coating was dried at 165 ° C. for 1 minute. Thereby, the outermost layer of the back surface layer was formed on the first layer of the back surface layer.
[Back surface layer coating solution B]
Acrylic resin binder 42.6 parts by mass (manufactured by Daicel Chemical Industries, EM48D, solid content 27.5%)
Compound having a plurality of carbodiimide structures 4.8 parts by mass (Nisshinbo Co., Ltd., Carbodilite V-02-L2, solid content 40%)
Surfactant A 15.8 parts by mass (Nippon Yushi Co., Ltd., 1% aqueous solution of Lapisol B-90, anionic)
Surfactant B 15.8 parts by mass (Sanyo Chemical Industry Co., Ltd., 1% aqueous solution of NAROACTY CL-95, nonionic)
Silica fine particle dispersion 1.9 parts by mass (manufactured by Nippon Aerosil Co., Ltd., aqueous dispersion of Aerosil OX-50, solid content 10%)
Colloidal silica 0.8 parts by mass (manufactured by Nissan Chemical Industries, Snowtex XL, solid content 40.5%)
Sliding agent 1.9 parts by mass (manufactured by Chukyo Yushi Co., Ltd., carnauba wax dispersion cellosol 524 solid content 30%)
Add distilled water to 1000 parts by mass

[Light diffusion layer]
A light diffusion coating solution and a crosslinking agent solution having the following composition were fed by a pump. At that time, while the liquid diffusion coating solution was fed at a flow rate of 100 g and the crosslinking agent solution at a flow rate of 9.98 g, both were mixed with a static mixer (φ3.4-N60S-523-F, Noritake Company Limited). Mixed). And 3 minutes after producing this liquid mixture, it apply | coated so that an application quantity might be 64.4cc / m < ² > on the 2nd layer of an easily bonding layer, and this was dried for 2 minutes at 120 degreeC. As a result, a light diffusion layer was formed.
[Coating liquid for light diffusion layer]
Methyl ethyl ketone 1,130g
Acrylic resin 501.6g
(Acridic A811BE, manufactured by Dainippon Ink & Chemicals, Inc., 50% by mass solution, hydroxyl value 17, acid value 3)
Jurimar MB-20X 421.3g
(Polymethylmethacrylate cross-linked organic fine particles, manufactured by Nippon Pure Chemical Industries, Ltd., spherical fine particles with an average particle size of 18 μm)
F780F 0.97g
(Dainippon Ink & Chemicals, Inc., 30% by weight methyl ethyl ketone solution)
[Crosslinking agent solution]
Methyl ethyl ketone 1039g
Isocyanate compound 352g
(Takenate D110N, manufactured by Mitsui Takeda Chemical Co., Ltd.)

[Example 2]
Each layer was formed in the same manner as in Example 1 except that the back surface layer coating liquid C having the following composition was used instead of the back surface layer coating liquid B.
[Back surface layer coating liquid C]
42.3 parts by mass of polyolefin resin binder (Mitsui Chemicals, Chemipearl S-120, solid content 27%)
Epoxy compound 162.4 parts by mass (manufactured by Nagase Chemical Co., Ltd., 1% aqueous solution of Denacol EX-614B)
Surfactant A 11.0 parts by mass (Nippon Yushi Co., Ltd., 1% aqueous solution of Lapisol B-90, anionic)
Surfactant B 13.4 parts by mass (Sanyo Chemical Industry Co., Ltd., 1% aqueous solution of NAROACTY CL-95, nonionic)
Silica fine particle dispersion 1.4 parts by mass (manufactured by Nippon Aerosil Co., Ltd., Aerosil OX-50 aqueous dispersion, solid content 10%)
Colloidal silica 0.5 parts by mass (manufactured by Nissan Chemical Industries, Snowtex XL, solid content 40.5%)
Sliding agent 1.4 parts by mass (manufactured by Chukyo Yushi Co., Ltd., carnauba wax dispersion cellosol 524 solid content 30%)
Add distilled water to 1000 parts by mass

[Example 3]
Each layer was formed in the same manner as in Example 1 except that the back layer coating solution D having the following composition was used instead of the back layer coating solution A.
[Back layer coating liquid D]
213.9 parts by mass of polyester resin binder (manufactured by Kyoyo Chemical Co., Ltd., plus coat Z-561, solid content 25%)
Compound having a plurality of carbodiimide structures 26.2 parts by mass (Nisshinbo Co., Ltd., Carbodilite V-02-L2, solid content 40%)
Surfactant A 17.4 parts by mass (Nippon Yushi Co., Ltd., 1% aqueous solution of Lapisol B-90, anionic)
Surfactant B 42.9 parts by mass (Sanyo Chemical Industry Co., Ltd., NAROACTY CL-95 1% aqueous solution, nonionic)
Matting agent 0.8 part by mass (manufactured by Soken Chemical Co., Ltd., cross-linked PMMA particles MX-501α, average particle size 5.4 μ)
Add distilled water to 1000 parts by mass

[Comparative Example 1]
In the same manner as in Example 1, the first layer and the second layer of the easy adhesion layer were formed on one surface of the PET support. Thereafter, the other surface of the PET support was subjected to corona discharge treatment, and a back layer coating solution E having the following composition was applied by a bar coating method. The coating amount was 24.5 cc / m ² and the coating was dried at 185 ° C. for 2 minutes. Thereby, the outermost layer of the back surface layer was formed on the side opposite to the surface on which the easy adhesion layer was formed. Thereafter, a diffusion layer was formed in the same manner as in Example 1.
[Back layer coating liquid E]
Acrylic resin binder 437.4 parts by mass (manufactured by Daicel Chemical Industries, Ltd., EM48D, solid content 27.5%)
Compound having a plurality of carbodiimide structures 60.0 parts by mass (Nisshinbo Co., Ltd., Carbodilite V-02-L2, solid content 40%)
Surfactant A 39.1 parts by mass (Nippon Yushi Co., Ltd., 1% aqueous solution of Lapisol B-90, anionic)
Surfactant B 96.5 parts by mass (Sanyo Chemical Industry Co., Ltd., 1% aqueous solution of NAROACTY CL-95, nonionic)
8.2 parts by mass of colloidal silica (manufactured by Nissan Chemical Industries, Snowtex XL, solid content 40.5%)
Matting agent 0.3 part by mass (manufactured by Soken Chemical Co., Ltd., crosslinked PMMA particles MX-501α, average particle size 5.4 μm)
Sliding agent 19.5 parts by mass (manufactured by Chukyo Yushi Co., Ltd., carnauba wax dispersion cellosol 524 solid content 30%)
Add distilled water to 1000 parts by mass

[Comparative Example 2]
Each layer was formed in the same manner as in Example 1 except that the back layer coating solution F having the following composition was used instead of the back layer coating solution B.
[Back surface layer coating solution F]
46.8 parts by mass of polyester resin binder (manufactured by Kyoyo Chemical Co., Ltd., plus coat Z-561, solid content 25%)
Compound having a plurality of carbodiimide structures 4.8 parts by mass (Nisshinbo Co., Ltd., Carbodilite V-02-L2, solid content 40%)
Surfactant A 15.8 parts by mass (Nippon Yushi Co., Ltd., 1% aqueous solution of Lapisol B-90, anionic)
Surfactant B 15.8 parts by mass (Sanyo Chemical Industry Co., Ltd., 1% aqueous solution of NAROACTY CL-95, nonionic)
Silica fine particle dispersion 1.9 parts by mass (manufactured by Nippon Aerosil Co., Ltd., aqueous dispersion of Aerosil OX-50, solid content 10%)
Colloidal silica 0.8 parts by mass (manufactured by Nissan Chemical Industries, Snowtex XL, solid content 40.5%)
Sliding agent 1.9 parts by mass (manufactured by Chukyo Yushi Co., Ltd., carnauba wax dispersion cellosol 524 solid content 30%)
Add distilled water to 1000 parts by mass

[Comparative Example 3]
Each layer was formed in the same manner as in Example 1 except that the back layer coating solution G having the following composition was used instead of the back layer coating solution B.
[Back surface layer coating liquid G]
Acrylic resin binder 19.8 parts by mass (manufactured by Daicel Chemical Industries, EM48D, solid content 27.5%)
Compound having a plurality of carbodiimide structures 2.7 parts by mass (Nisshinbo Co., Ltd., Carbodilite V-02-L2, solid content 40%)
Surfactant A 7.4 parts by mass (Nippon Yushi Co., Ltd., 1% aqueous solution of Lapisol B-90, anionic)
Surfactant B 9.0 parts by mass (Sanyo Chemical Industry Co., Ltd., 1% aqueous solution of NAROACTY CL-95, nonionic)
0.9 parts by mass of silica fine particle dispersion (manufactured by Nippon Aerosil Co., Ltd., aqueous dispersion of Aerosil OX-50, solid content 10%)
Colloidal silica 0.4 parts by mass (manufactured by Nissan Chemical Industries, Snowtex XL, solid content 40.5%)
0.9 part by mass of slip agent (manufactured by Chukyo Yushi Co., Ltd., carnauba wax dispersion cellosol 524 solid content 30%)
Add distilled water to 1000 parts by mass

[Comparative Example 4]
Each layer was formed in the same manner as in Example 1 except that the back layer coating solution H having the following composition was used instead of the back layer coating solution B.
[Back surface layer coating solution H]
Acrylic resin binder 67.2 parts by mass (manufactured by Daicel Chemical Industries, Ltd., EM48D, solid content 27.5%)
Compound having a plurality of carbodiimide structures 9.3 parts by mass (Nisshinbo Co., Ltd., Carbodilite V-02-L2, solid content 40%)
Surfactant A 25.0 parts by mass (Nippon Yushi Co., Ltd., 1% aqueous solution of Lapisol B-90, anionic)
Surfactant B 30.6 parts by mass (Sanyo Chemical Industry Co., Ltd., 1% aqueous solution of NAROACTY CL-95, nonionic)
Silica fine particle dispersion 3.1 parts by mass (manufactured by Nippon Aerosil Co., Ltd., aqueous dispersion of Aerosil OX-50, solid content 10%)
1.3 parts by mass of colloidal silica (manufactured by Nissan Chemical Industries, Snowtex XL, solid content 40.5%)
Sliding agent 3.1 parts by mass (manufactured by Chukyo Yushi Co., Ltd., carnauba wax dispersion cellosol 524 solid content 30%)
Add distilled water to 1000 parts by mass

[Evaluation]
The following evaluation was performed about the diffusion sheet obtained by the said Examples 1-3 and Comparative Examples 1-4.

[Thickness of easy adhesion layer and back layer]
First, the film thickness of the diffusion sheet laminated film having no back layer was measured at a magnification of 200,000 times with a transmission electron microscope (JEM2010 (JEOL Ltd.)).

  The film thickness of the laminated film for diffusion sheet having only one back layer (the film obtained in Comparative Example 1) was measured with a transmission electron microscope in the same manner as described above. From the film thickness obtained by this measurement, the film thickness of the back layer was determined by subtracting the film thickness of the laminated film for diffusion sheet having no back layer described above.

  About the laminated film for diffusion sheets having two back layers (films obtained in Examples 1 to 3 and Comparative Examples 2 to 4), first, the film thickness after forming the first layer of the back layer is described above. In the same manner as described above, the measurement was performed with a transmission electron microscope. From the film thickness obtained by this measurement, the film thickness of the first layer of the back layer was determined by subtracting the film thickness of the laminated film for diffusion sheet having no back layer described above. Next, the film thickness after forming the outermost layer of the back layer was measured with a transmission electron microscope in the same manner as described above. The film thickness of the outermost layer of the back surface layer was determined by subtracting the film thickness of the first layer of the back surface layer from the film thickness obtained by this measurement.

[Refractive index of coating layer]
On the silicon wafer, coating liquids A to H for the back layer were applied so that the dry film thickness was 3 to 4 μm, and dried at 105 ° C. for 10 minutes. The sample was subjected to refractive index measurement by a prism coupler method using SPA-400 (manufactured by Sairon Technology, Inc.) at wavelengths of 660 nm, 850 nm, 1310 nm, and 1550 nm. The refractive index at 550 nm was determined from the Cermeier formula from these refractive indices and wavelengths.

[Backside reflectance]
Applying magic ink (artline oil-based marker supplement ink KR-20 black, manufactured by shachihata Co., Ltd.) on the easy-adhesion layer side of the laminated film for diffusion sheet, and drying it, the transmittance of light at 500 nm is 1 A pre-treatment sample that was less than or equal to% was prepared. Then, using a spectrophotometer (V-550 manufactured by JASCO Corporation) and an absolute reflectance measuring device (ARV-474 manufactured by JASCO Corporation), an incident angle of 5 °, a wavelength range of 380 to 780 nm, sampling While measuring the absolute reflectance on the back layer side of the pretreated sample under the conditions of pitch 1 nm, slit width 1 nm, scanning speed 200 nm / min, and response medium, the average value of absolute reflectances of 380 to 780 nm was obtained.

[Total light transmittance]
Using a haze meter (NDH-2000, Nippon Denshoku Industries Co., Ltd.), the total light transmittance and haze value were measured according to JIS-K-7105.

[Luminance]
A laminated film for a diffusion sheet is placed on the diffusion plate of a direct-type backlight unit for a liquid crystal television composed of a reflection sheet, a cold cathode tube, and a diffusion plate, and a color luminance meter (BM-7, Topcon Techno House Co., Ltd.). )), The front luminance on the diffusion layer side was measured. The luminance when measured without placing the laminated film for diffusion sheet was taken as 100%, and the rate of increase in luminance when placed was evaluated according to the following criteria.
○: Brightness increase rate is 128% or more Δ: Brightness increase rate is 127% or more and less than 128% ×: Brightness increase rate is less than 127%

[Adhesion with diffusion layer]
Using a single-edged razor on the surface of the diffusion layer, six vertical and horizontal scratches were made to form 25 squares. The width of the scratch was 3 mm both vertically and horizontally. A cellophane tape (No. 405 manufactured by Nichiban Co., Ltd., 24 mm width) was affixed on this, and then completely adhered by rubbing with poppy rubber. Thereafter, the squares peeled off in the 90-degree direction were counted, and the following ranking was performed according to the number of peeled squares.
Rank A: No peeling Rank B: Number of peeled squares is less than 1 Rank C: Number of peeled squares is 1 or more and less than 3 D Rank: Number of peeled squares is 3 or more and less than 20 E Rank: Number of peeled squares is 20 or more

[Matting agent detachment]
The detachment property of the matting agent was evaluated in an abrasion resistance tester (manufactured by Shinto Chemical Co., Ltd.). Specifically, a black paper (manufactured by FUJIFILM Corporation, SKBT3 90BIG0) is brought into contact with the coated surface on the back side, and a load of 3 kg per 30 mm × 25 mm is applied, and a distance of 10 cm is set to 100 cm / min. Rubbed with. After the rubbing test, the level of white powder adhering to the black paper was visually evaluated.
○: No white powder adherence or very small Δ: Some white powder adherence is observed.
X: White powder adheres remarkably.

[result]
The results of the above evaluation are shown in Table 1 below.

  As shown in Table 1, in Examples 1 to 3, the luminance increase rate was improved to 128% or more by setting the back surface average reflectance to 3.5% or less.

  On the other hand, in Comparative Example 1, since the film thickness of the outermost layer on the back surface was very large compared with Examples 1 to 3, the luminance improvement characteristics were not good. Further, in Comparative Example 3, since the film thickness was small as compared with Examples 1 to 3, the luminance enhancement characteristics were not good. Further, in Comparative Example 4, although the film thickness was not as large as that in Comparative Example 1, the brightness enhancement characteristics were not good because the film thickness was larger than those in Examples 1 to 3. Moreover, in Comparative Example 2, since the refractive index of the back outermost layer was large as compared with Examples 1 to 3, the luminance enhancement characteristics were not good.

It is principal part sectional drawing of the laminated | multilayer film for diffusion sheets. It is principal part sectional drawing of a diffusion sheet.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Diffusion sheet laminated film 11 Support 12 Easy adhesion layer 12a First layer 12b Second layer 13 Back surface layer 13a First layer 13b Outermost layer 14 Diffusion layer 15 Diffusion sheet

Claims (6)

A support made of biaxially stretched polyester;
An easy-adhesion layer comprising a compound having a plurality of carbodiimide structures provided on one surface of the support;
A laminated film for a diffusion sheet, comprising a back layer provided on the other surface of the support and having an average reflectance of 3.5% or less with respect to light having a wavelength of 380 nm to 780 nm.   The back layer is composed of one or more layers, and the refractive index n of the outermost layer in contact with air among the one or more layers is 1.20 to 1.51, and the film thickness of the outermost layer is (550 / (4n)) The laminated film for a diffusion sheet according to claim 1, which is within a range of ± 40 nm.   The laminated film for a diffusion sheet according to claim 1 or 2, wherein the back surface layer comprises a plurality of layers, and matting agent particles are added to a first layer in contact with the support among the plurality of layers.   The laminated film for a diffusion sheet according to any one of claims 1 to 3, wherein the easy adhesion layer and the back surface layer are provided after the support is biaxially stretched.   The diffusion sheet is provided with a diffusion layer on the easy-adhesion layer of the film for diffusion sheet according to claim 1.   A display device comprising the laminated film for a diffusion sheet according to any one of claims 1 to 4.

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