Thermoplastic resin composition and method for producing pellets

Abstract

The present disclosure provides a thermoplastic resin composition for an optical film, the thermoplastic resin composition containing a thermoplastic resin and an inorganic light diffusing agent dispersed in the thermoplastic resin, wherein the inorganic light diffusing agent is characterized in that an aspect ratio D50 at which a cumulative frequency is 50% in a number-based aspect ratio distribution is 2.0 to 5.0 inclusive, and a major axis D50 at which a cumulative frequency is 50% in a number-based major axis distribution is 5.0 μm to 10.0 μm inclusive.

Description

Thermoplastic resin composition and method for producing pellets

[0001] The present disclosure relates to a thermoplastic resin composition and a method for producing pellets.

[0002] Optical films having a light diffusion function are known. For example, Patent Document 1 describes a light diffusion film including an isotropic transparent resin matrix and inorganic needle-like fillers having a refractive index different from that of the isotropic transparent resin matrix, which are dispersed in a certain direction within the isotropic transparent resin matrix. The inorganic needle-like fillers are so-called light diffusing agents.

[0003] The light diffusion film in Patent Document 1 is produced by applying a dope in which a resin and a light diffusing agent are dissolved or dispersed in a solvent onto a transparent substrate, a release sheet, or various optical elements, and then drying and removing the solvent.

[0004] Japanese Patent Application Laid-Open No. 2008-129546

[0005] By the way, a melt extrusion method is known as another method for producing an optical film. The melt extrusion method is a method of forming a thermoplastic resin composition in a molten state into a film shape, and unlike the solution casting method, it is not necessary to volatilize a solvent. It has an advantage that an apparatus for recovering the volatilized solvent can be omitted as compared with the solution casting method.

[0006] In view of the above, the present disclosure aims to solve problems such as providing a thermoplastic resin composition suitable for producing an optical film by a melt extrusion method.

[0007] This disclosure includes the following configurations: [1] A thermoplastic resin composition for optical films, comprising a thermoplastic resin and an inorganic light-diffusing agent dispersed in the thermoplastic resin, wherein the inorganic light-diffusing agent has an aspect ratio D50 at which the cumulative frequency in the number-based aspect ratio distribution reaches 50% is 2.0 or more and 5.0 or less, and a major axis D50 at which the cumulative frequency in the number-based major axis distribution reaches 50% is 5.0 μm or more and 10.0 μm or less. [2] The thermoplastic resin composition according to [1], wherein the inorganic light-diffusing agent has an aspect ratio D10 at which the cumulative frequency in the number-based aspect ratio distribution reaches 10% is 1.3 or more and less than 2.0. [3] The thermoplastic resin composition according to [1] or [2], wherein the inorganic light-diffusing agent has an aspect ratio D90 at which the cumulative frequency in the number-based aspect ratio distribution reaches 90% is greater than 5.0 and 9.0 or less. [4] The thermoplastic resin composition according to any one of [1] to [3], wherein the inorganic light diffuser is such that the proportion of particles with an aspect ratio of 5 or more is greater than 10% and less than or equal to 35% on a number basis. [5] The thermoplastic resin composition according to any one of [1] to [4], wherein the inorganic light diffuser is such that the major axis D10 at which the cumulative frequency in the major axis distribution on a number basis is 10% is 2.0 μm or more and less than 5.0 μm. [6] The thermoplastic resin composition according to any one of [1] to [5], wherein the inorganic light diffuser is such that the major axis D90 at which the cumulative frequency in the major axis distribution on a number basis is 90% is greater than 10.0 μm and less than or equal to 25.0 μm. [7] The thermoplastic resin composition according to any one of [1] to [6], wherein the thermoplastic resin comprises a (meth)acrylic resin. [8] The thermoplastic resin composition according to [7], wherein the (meth)acrylic resin comprises a ring structure unit having a heterocycle that shares two or more carbon atoms with the main chain. [9] The thermoplastic resin composition according to [8], wherein the ring structural unit comprises at least one selected from the group consisting of lactone ring structural units, glutarimide structural units, and succinimide structural units.

[10] The thermoplastic resin composition according to any one of [1] to [9], wherein the inorganic light diffusing agent comprises at least one selected from the group consisting of calcium carbonate, titanium dioxide, magnesium sulfate, and aluminum borate.

[11] The thermoplastic resin composition according to any one of [1] to

[10] , wherein the content of the inorganic light diffusing agent is 1% by mass or more and 5% by mass or less.

[12] A thermoplastic resin composition according to any one of [1] to

[11] , wherein the glass transition temperature is 110°C or higher and 160°C or lower.

[13] A thermoplastic resin composition according to any one of [1] to

[12] , wherein the composition is a pellet.

[14] A method for producing pellets made of a thermoplastic resin composition for optical films, comprising a thermoplastic resin and an inorganic light-diffusing agent containing a needle-shaped light-diffusing agent, wherein a melt extruder is used, comprising a cylinder extending in the axial direction, a screw disposed in the cylinder, a main feed port provided in the cylinder, a side feed port provided downstream of the main feed port in the extrusion direction, a die with nozzle holes formed therein, and a polymer filter provided upstream of the die, the method comprising the steps of: feeding the thermoplastic resin into the melt extruder from the main feed port and feeding the inorganic light-diffusing agent into the melt extruder from the side feed port to melt-knead the thermoplastic resin and the inorganic light-diffusing agent to obtain a thermoplastic resin composition; and filtering the thermoplastic resin composition with a polymer filter and then extruding it from the melt extruder, wherein the inorganic light-diffusing agent fed into the side feed port has an aspect ratio D50 of 3.0 or more at which the cumulative frequency in the number-based aspect ratio distribution reaches 50%.

[15] The method for producing pellets according to

[14] , wherein the needle-shaped light diffusing agent is a particle with an aspect ratio of 2.0 or more.

[16] The method for producing pellets according to

[14] or

[15] , wherein the thermoplastic resin contains a (meth)acrylic resin.

[17] L is the distance from the side feed opening to the polymer filter in the axial direction. １ The outer diameter including the screw threads between the side feed port and the polymer filter is D. １ As the ratio (L １ / D １ A method for manufacturing pellets according to any one of

[14] to

[16] , wherein the ratio is 8 or more and 30 or less.

[18] The distance from the main feed port to the polymer filter in the axial direction is L ２ For example, the distance from the side feed port to the polymer filter is 0.15L ２ 0.55L ２The method for producing pellets according to any one of

[14] to

[17] below. The inorganic light diffusing agent introduced into the side feed port has an aspect ratio D50 of 6.0 or less at which the cumulative frequency is 50% in the aspect ratio distribution based on the number of particles, according to the method for producing pellets according to any one of

[14] to

[18] . The inorganic light diffusing agent introduced into the side feed port has a major axis D50 of 6.0 μm or more and 10.5 μm or less at which the cumulative frequency is 50% in the major axis distribution based on the number of particles, according to the method for producing pellets according to any one of

[14] to

[19] . An optical film comprising the thermoplastic resin composition according to any one of [1] to

[13] above. An optical film containing a thermoplastic resin and an inorganic light diffusing agent containing a needle-like light diffusing agent, having a pair of first sides extending in a first direction and a pair of second sides extending in a second direction perpendicular to the first direction, wherein when light is irradiated perpendicular to the main surface of the optical film, the first average light transmittance that is refracted and transmitted at an angle of 10° or more and 15° or less in the first direction is T １ Let it be, and the second average light transmittance that is refracted and transmitted at an angle of 10° or more and 15° or less in the second direction is T ２ Let it be, when the ratio (T ２ / T １ ) is 2.5 or more and 10 or less, and the second average light transmittance T ２ is 1.5% or more and 5.0% or less. An optical film characterized by the above. An optical film comprising a thermoplastic resin composition containing a thermoplastic resin and an inorganic light diffusing agent, wherein the inorganic light diffusing agent has an aspect ratio D50 of 1.6 or more and 5.0 or less at which the cumulative frequency is 50% in the aspect ratio distribution based on the number of particles, and a major axis D50 of the cumulative frequency of 50% in the major axis distribution based on the number of particles is 4.0 μm or more and 10.0 μm or less.

[0008] According to the present disclosure, it is possible to provide a thermoplastic resin composition suitable for producing an optical film by a melt extrusion method, and the like.

[0009] This disclosure is described below. However, this disclosure is not limited to the following description. In the following description, (meth)acrylic resin is a term that encompasses both methacrylic resin and acrylic resin. Similarly, for example, (meth)acrylate is a term that encompasses both methyl methacrylate and methyl acrylate.

[0010] <Thermoplastic Resin Composition> The first embodiment of the present disclosure is a thermoplastic resin composition for optical films, comprising a thermoplastic resin and an inorganic light diffusing agent dispersed in the thermoplastic resin, wherein the inorganic light diffusing agent has an aspect ratio D50 at which the cumulative frequency in the number-based aspect ratio distribution reaches 50% is 2.0 or more and 5.0 or less, and a major axis D50 at which the cumulative frequency in the number-based major axis distribution reaches 50% is 5.0 μm or more and 10.0 μm or less.

[0011] [Thermoplastic Resin] The thermoplastic resin composition according to this embodiment contains a thermoplastic resin with excellent transparency. Specific examples of the thermoplastic resin are not particularly limited, but include, for example, polyolefin resin, polyester resin, polyamide resin, (meth)acrylic resin, polyvinyl chloride resin, polystyrene resin, polyphenylene ether resin, polyacetal resin, polycarbonate resin, polysulfone resin, polyetherimide resin, polyethersulfone resin, polyetheretherketone resin, and polyetherketone resin. The thermoplastic resin preferably contains a (meth)acrylic resin.

[0012] (Meth)acrylic resin contains structural units (p) derived from alkyl (meth)acrylate monomers. Alkyl (meth)acrylate monomers are esters composed of (meth)acrylic acid and a monohydric alkyl alcohol. Specific examples of structural units (p) are not particularly limited, but include structural units derived from monomers such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, and n-hexyl (meth)acrylate. Structural units (p) may contain only one of these structural units, or two or more.

[0013] The alkyl group of the alkyl (meth)acrylate is preferably an alkyl group having 1 to 5 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, even more preferably an alkyl group having 1 to 3 carbon atoms, particularly preferably an alkyl group having 1 to 2 carbon atoms, and most preferably an alkyl group having 1 carbon atom (methyl group). The numerical range indicated as X to Y means that it is between X and Y.

[0014] The structural unit (p) preferably includes a structural unit derived from methyl (meth)acrylate.

[0015] The content of structural units (p) in the (meth)acrylic resin is preferably 60% by mass or more and 90% by mass or less, and more preferably 65% ​​by mass or more and 85% by mass or less.

[0016] The (meth)acrylic resin preferably contains a ring structure unit (q) having a heterocycle that shares two or more carbon atoms with the main chain. That is, the heterocycle contained in the ring structure unit (q) preferably constitutes the main chain of the (meth)acrylic resin.

[0017] The heterocyclic ring constituting the main chain of the ring structure unit (q) may be any of the following: a four-membered ring structure, a five-membered ring structure, a six-membered ring structure, a seven-membered ring structure, an eight-membered ring structure, etc., but a five-membered ring structure or a six-membered ring structure is preferred.

[0018] The heterocycle constituting the main chain of the ring structure unit (q) may be introduced by polymerizing a (meth)acrylic monomer having a heterocycle, or by polymerizing a (meth)acrylic monomer having a group for forming a heterocycle and then introducing it by a chemical reaction.

[0019] Specific examples of the ring structural unit (q) are not particularly limited, but include, for example, lactone ring structural units, lactam ring structural units, glutaric acid anhydride structural units, glutarimide structural units, succinic acid anhydride structural units, and succinimide structural units. The ring structural unit (q) may contain only one of these structural units, or it may contain two or more.

[0020] The lactone ring structural unit has a lactone ring in its main chain. The number of members in the lactone ring structure is not particularly limited, but for example, it can be any of four-membered to eight-membered rings. From the viewpoint of increasing the stability of the ring structure, the lactone ring structure is preferably a five-membered or six-membered ring, and more preferably a six-membered ring. The lactam ring structural unit has a lactam in its main chain. The number of members in the lactam ring structure is not particularly limited, but for example, it can be any of four-membered to eight-membered rings. From the viewpoint of increasing the stability of the ring structure, the lactam ring structure is preferably a five-membered or six-membered ring, and more preferably a five-membered ring.

[0021] The lactone ring structural unit is preferably a structural unit represented by the following formula (1a). The lactam ring structural unit is preferably a structural unit represented by the following formula (1b).

[0022]

[0023] In formula (1a), R １１ and R １２ Each of these is independently and not particularly limited, but for example, a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms. The hydrocarbon group may be linear, branched, or cyclic. The hydrocarbon group may be either an aliphatic hydrocarbon group or an aromatic hydrocarbon group. １３ This is either a hydrogen atom or a methyl group.

[0024] In formula (1b), R １５ and R １６ Each of these is independently and not particularly limited, but for example, a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms. The hydrocarbon group may be linear, branched, or cyclic. The hydrocarbon group may be either an aliphatic hydrocarbon group or an aromatic hydrocarbon group. １４ This is either a hydrogen atom or a methyl group.

[0025] In equation (1a), R １１ and R １２ Each is preferably independently a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and each is more preferably independently a hydrogen atom or a methyl group. In formula (1b), R １５ and R １６Each of these is preferably a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and each is more preferably a hydrogen atom or a methyl group.

[0026] The structural unit represented by formula (1a) can be formed, for example, by polymerizing a group of monomers including methyl 2-(hydroxymethyl)acrylate and methyl (meth)acrylate, followed by de-alcoholization condensation between the hydroxyl group and the ester bond. The structural unit represented by formula (1b) can be formed, for example, by polymerizing a group of monomers including N-vinylacetamide and methyl (meth)acrylate, followed by de-alcoholization condensation between the amide group and the ester bond.

[0027] The ring structure unit (q) may contain only one lactone ring structure unit represented by formula (1a), or it may contain two or more. The ring structure unit (q) may contain only one lactam ring structure unit represented by formula (1b), or it may contain two or more.

[0028] The glutaric acid anhydride structural unit is preferably the structural unit represented by the following formula (2a). The glutarimide structural unit is preferably the structural unit represented by the following formula (2b).

[0029]

[0030] In formula (2a), R ２１ ~R ２３ Each of these is independently either a hydrogen atom or a methyl group.

[0031] In formula (2b), R ２４ ~R ２６ Each of these is independently either a hydrogen atom or a methyl group. ２７ This is not particularly limited, but for example, it is a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms. The hydrocarbon group may be linear, branched, or cyclic. The hydrocarbon group may be either an aliphatic hydrocarbon group or an aromatic hydrocarbon group. ２７ The group is preferably a hydrogen atom, a methyl group, a cyclohexyl group, a phenyl group, or a tolyl group, and more preferably a hydrogen atom or a methyl group.

[0032] The structural unit represented by formula (2a) can be formed, for example, by polymerizing a group of monomers including a (meth)acrylic acid monomer and a (meth)methyl acrylate monomer, followed by dehydration condensation between the carboxyl group and the ester bond. The structural unit represented by formula (2b) can be formed, for example, by polymerizing a group of monomers including a (meth)methyl acrylate monomer, followed by imidation between the two ester bonds.

[0033] The ring structure unit (q) may contain only one glutaric acid anhydride structure unit represented by formula (2a), or it may contain two or more. The ring structure unit (q) may contain only one glutarimide structure unit represented by formula (2b), or it may contain two or more.

[0034] The succinic anhydride structural unit (a structural unit derived from the maleic anhydride monomer) is preferably the structural unit represented by the following formula (3a). The succinimide structural unit (a structural unit derived from the maleimide monomer) is preferably the structural unit represented by the following formula (3b).

[0035]

[0036] In formula (3a), R ３１ and R ３２ Each of these is independently either a hydrogen atom or a methyl group.

[0037] In formula (3b), R ３３ and R ３４ Each of these is independently either a hydrogen atom or a methyl group. ３５ This is not particularly limited, but for example, it is a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms. The hydrocarbon group may be linear, branched, or cyclic. The hydrocarbon group may be either an aliphatic hydrocarbon group or an aromatic hydrocarbon group. ３５ The group is preferably a methyl group, an ethyl group, a cyclohexyl group, a phenyl group, a naphthyl group, or a benzyl group, and more preferably a cyclohexyl group or a phenyl group.

[0038] The structural unit represented by formula (3a) can be formed, for example, by polymerizing a group of monomers including maleic anhydride. The structural unit represented by formula (3b) can be formed, for example, by polymerizing a group of monomers including maleimide or N-substituted maleimide.

[0039] The ring structure unit (q) may contain only one succinic anhydride structure unit represented by formula (3a), or it may contain two or more. The ring structure unit (q) may contain only one succinimide structure unit represented by formula (3b), or it may contain two or more.

[0040] The ring structural unit (q) preferably includes at least one selected from the group consisting of lactone ring structural units, glutarimide structural units, and succinimide structural units, more preferably includes at least one selected from the group consisting of lactone ring structural units and glutarimide structural units, and even more preferably includes lactone ring structural units.

[0041] The content of ring structural units (q) in the (meth)acrylic resin is preferably 10% by mass or more and 40% by mass or less, and more preferably 15% by mass or more and 35% by mass or less.

[0042] The (meth)acrylic resin may further contain other structural units (r) derived from monomers copolymerizable with structural unit (p). Specific examples of structural unit (r) are not particularly limited, but include structural units derived from monomers such as styrene, vinyltoluene, α-methylstyrene, α-hydroxymethylstyrene, α-hydroxyethylstyrene, acrylonitrile, methacrylonitrile, ethylene, propylene, 4-methyl-1-pentene, vinyl acetate, 2-hydroxymethyl-1-butene, methyl vinyl ketone, N-vinylpyrrolidone, and N-vinylcarbazole. Structural unit (r) may contain only one of these structural units, or two or more.

[0043] The structural unit (r) may include, for example, structural units derived from styrene, with respect to adjusting the optical properties of the (meth)acrylic resin.

[0044] The content of structural units (r) in the (meth)acrylic resin may be 0% by mass or more and 20% by mass or less, or 0% by mass or more and 10% by mass or less.

[0045] Structural unit (r) can be defined as structural unit other than structural unit (p) and ring structural unit (q). When (meth)acrylic resin contains structural unit (p), ring structural unit (q), and structural unit (r), the total content of structural unit (p), ring structural unit (q), and structural unit (r) in the (meth)acrylic resin is 100% by mass.

[0046] Furthermore, the content of each structural unit in (meth)acrylic resin is determined by dissolving the (meth)acrylic resin in a deuterated solvent. １ This can be determined by measuring H-NMR and calculating the area ratio of the peaks corresponding to each structural unit.

[0047] The glass transition temperature of the (meth)acrylic resin is preferably 110°C to 160°C, more preferably 115°C to 150°C, and even more preferably 120°C to 140°C. The glass transition temperature of the (meth)acrylic resin can be measured by the method described in the examples below.

[0048] The weight-average molecular weight of the (meth)acrylic resin is preferably 80,000 to 350,000, more preferably 100,000 to 250,000, and even more preferably 120,000 to 200,000. The weight-average molecular weight of the (meth)acrylic resin can be measured by the method described in the examples below.

[0049] The number-average molecular weight of the (meth)acrylic resin is preferably 30,000 to 160,000, more preferably 40,000 to 130,000, and even more preferably 50,000 to 100,000. The number-average molecular weight of the (meth)acrylic resin can be measured by the method described in the examples below.

[0050] The content of (meth)acrylic resin in the thermoplastic resin composition is preferably 65% ​​by mass or more and 99% by mass or less, more preferably 70% by mass or more and 95% by mass or less, and even more preferably 75% by mass or more and 90% by mass or less. Such a thermoplastic resin composition mainly composed of (meth)acrylic resin can also be called a (meth)acrylic resin composition.

[0051] The thermoplastic resin composition may contain a thermoplastic resin other than the (meth)acrylic resin (another thermoplastic resin). The other thermoplastic resin is a thermoplastic resin that exhibits excellent transparency, similar to the (meth)acrylic resin. Specific examples of the other thermoplastic resin are not particularly limited, but include, for example, styrene-based resins (polystyrene, acrylonitrile-styrene resin, methyl methacrylate-styrene resin, etc.), polycarbonate resin, polyvinylidene fluoride resin, and polyimide resin. The content of the other thermoplastic resin in the (meth)acrylic resin composition may be 0% by mass or more and 30% by mass or less, 0% by mass or more and 20% by mass or less, or 0% by mass or more and 10% by mass or less.

[0052] [Inorganic Light Diffuser] The thermoplastic resin composition according to this embodiment contains an inorganic light diffuser. By doing so, the light diffusivity of the optical film produced from the thermoplastic resin composition can be improved.

[0053] The inorganic light diffusing agent has an aspect ratio D50 of 2.0 to 5.0 at which the cumulative frequency in the number-based aspect ratio distribution reaches 50%. This ensures that the optical film produced from the thermoplastic resin composition exhibits good anisotropy and excellent light diffusing properties. The aspect ratio D50 may also be between 2.2 and 4.5, or between 2.4 and 4.0.

[0054] The inorganic light diffusing agent may have an aspect ratio D10 at which the cumulative frequency in the number-based aspect ratio distribution reaches 10% be between 1.3 and less than 2.0, between 1.4 and 1.9, or between 1.5 and 1.8. This configuration allows the optical film manufactured from the thermoplastic resin composition to exhibit better anisotropy and light diffusion. Of course, the aspect ratio D10 is smaller than the aspect ratio D50.

[0055] The inorganic light diffusing agent may have an aspect ratio D90, where the cumulative frequency in the number-based aspect ratio distribution reaches 90%, be greater than 5.0 and 9.0 or less, or between 5.5 and 8.0, or between 6.0 and 7.0. This configuration allows the optical film manufactured from the thermoplastic resin composition to exhibit better anisotropy and light diffusion properties. Of course, the aspect ratio D90 is greater than the aspect ratio D50.

[0056] The inorganic light diffusing agent may have a maximum aspect ratio of 10.0 to 20.0, or 12.0 to 19.0. This configuration allows the optical film produced from the thermoplastic resin composition to exhibit better anisotropy and light diffusion properties.

[0057] The inorganic light diffusing agent may have a particle ratio of 5 or higher that accounts for more than 10% but 35% or less on a number basis, or more than 12% but 30% or less. By doing so, the optical film manufactured from the thermoplastic resin composition has better anisotropy for light diffusion.

[0058] The inorganic light diffusing agent has a major axis D50 of 5.0 μm or more and 10.0 μm or less at which the cumulative frequency in the number-based major axis distribution reaches 50%. This ensures that the optical film produced from the thermoplastic resin composition exhibits good anisotropy and excellent light diffusing properties. The major axis D50 may also be 5.2 μm or more and 9.5 μm or less, or 5.4 μm or more and 9.0 μm or less.

[0059] The inorganic light diffusing agent may have a major axis D10 at which the cumulative frequency in the number-based major axis distribution reaches 10% be between 2.0 μm and 5.0 μm, or between 2.2 μm and 4.0 μm, or between 2.4 μm and 3.0 μm. By doing so, the optical film manufactured from the thermoplastic resin composition has better anisotropy for light diffusion. Of course, the major axis D10 is smaller than the major axis D50.

[0060] The inorganic light diffusing agent may have a major axis D90, where the cumulative frequency in the number-based major axis distribution is 90%, be greater than 10.0 μm and less than or equal to 25.0 μm, or it may be between 10.5 μm and 20.0 μm, or between 11.0 μm and 15.0 μm. By doing so, the optical film manufactured from the thermoplastic resin composition has better anisotropy for light diffusion. Of course, the major axis D90 is greater than the major axis D50.

[0061] The inorganic light diffusing agent may have a maximum major axis of 20.0 μm to 50.0 μm, or 25.0 μm to 45.0 μm. This configuration results in an optical film manufactured from a thermoplastic resin composition that exhibits better anisotropy and light diffusion properties.

[0062] When the aspect ratio D50 of the inorganic light diffusing agent is 2.0 or more and 5.0 or less, the major axis D50 may be 5.2 μm or more and 9.5 μm or less, or 5.4 μm or more and 9.0 μm or less.

[0063] When the major axis D50 of the inorganic light diffusing agent is 5.0 μm or more and 10.0 μm or less, the aspect ratio D50 may be 2.2 or more and 4.5 or less, or 2.4 or more and 4.0 or less.

[0064] The aspect ratio and major axis mentioned above can be measured by the method described in the examples below.

[0065] The inorganic light diffusing agent may have an absolute difference in refractive index between it and the thermoplastic resin of 0.5 or more and 1.5 or less. If the inorganic light diffusing agent has different refractive indices depending on the direction, the absolute value of the maximum difference may be 0.5 or more and 1.5 or less. The refractive index of the thermoplastic resin can be measured according to Method A described in JIS K-7142 (1996). The refractive index of the inorganic light diffusing agent can be measured according to Method B described in JIS K-7142 (1996).

[0066] Specific examples of inorganic light diffusing agents are not particularly limited, but include, for example, calcium carbonate, strontium carbonate, titanium dioxide, zirconium oxide, zinc oxide, silicon dioxide, silicon carbide, calcium sulfate, barium sulfate, magnesium sulfate, zinc sulfide, magnesium hydroxide, aluminum borate, calcium silicate, potassium titanate, zonolite, and glass fibers. An inorganic light diffusing agent may contain only one of these, or two or more.

[0067] The inorganic light diffusing agent is preferably colorless or white. The inorganic light diffusing agent preferably contains at least one selected from the group consisting of calcium carbonate, titanium dioxide, magnesium sulfate, and aluminum borate, and more preferably contains calcium carbonate.

[0068] Inorganic light diffusing agents include needle-shaped light diffusing agents because their aspect ratio D50 satisfies the above range. In this disclosure, needle-shaped light diffusing agents may be particles with an aspect ratio of 2.0 or more, particles with an aspect ratio of 2.7 or more, or particles with an aspect ratio of 3.0 or more. As long as the above aspect ratio is satisfied, needle-shaped light diffusing agents are not limited to a needle shape, but may also have shapes such as columnar or spindle-shaped.

[0069] Specific examples of needle-shaped light diffusers are not particularly limited, but include, for example, calcium carbonate, strontium carbonate, titanium dioxide, zirconium oxide, zinc oxide, silicon dioxide, silicon carbide, calcium sulfate, barium sulfate, magnesium sulfate, zinc sulfide, magnesium hydroxide, aluminum borate, calcium silicate, potassium titanate, zonolite, and glass fibers. The needle-shaped light diffuser may contain only one of these, or two or more.

[0070] The needle-shaped light diffuser is preferably colorless or white. The needle-shaped light diffuser preferably contains at least one selected from the group consisting of calcium carbonate, titanium dioxide, magnesium sulfate, and aluminum borate, and more preferably contains calcium carbonate.

[0071] The calcium carbonate may be heavy calcium carbonate or light calcium carbonate. Furthermore, the calcium carbonate may be aragonite.

[0072] Calcium carbonate may be surface-treated. Surface treatment of calcium carbonate is not particularly limited, but examples include surface coating with organophosphorus-based surface treatment agents, inorganic phosphate-based surface treatment agents, polycarboxylic acid-based surface treatment agents, and coupling agent-based surface treatment agents.

[0073] The inorganic light diffusing agent may contain a non-acupuncture light diffusing agent. The non-acupuncture light diffusing agent is not particularly limited, but may have shapes such as spherical or irregular shapes (shapes that do not clearly show needle-like or spherical shapes). The non-acupuncture light diffusing agent may also be formed when the acupuncture light diffusing agent breaks off.

[0074] The content of the inorganic light diffusing agent in the thermoplastic resin composition is preferably 1% by mass or more and 5% by mass or less. This allows for a good balance between the light diffusing properties and total light transmittance of the optical film produced from the thermoplastic resin composition.

[0075] [Additives] The thermoplastic resin composition may contain additives other than inorganic light diffusing agents. Specific examples of additives are not limited to, but include, for example, organic fillers, ultraviolet absorbers, antioxidants, processing aids, plasticizers, impact aids, phase difference adjusters, matting agents, antibacterial agents, antifungal agents, and antistatic agents. The additive content in the (meth)acrylic resin composition may be 0% by mass or more and 30% by mass or less, 0% by mass or more and 20% by mass or less, 0% by mass or more and 10% by mass or less, or 0% by mass or more and 5% by mass or less.

[0076] [Characteristics of the Thermoplastic Resin Composition] The glass transition temperature of the thermoplastic resin composition is preferably 110°C to 160°C, more preferably 115°C to 150°C, and even more preferably 120°C to 140°C. The glass transition temperature of the thermoplastic resin composition can be measured by the method described in the examples below.

[0077] [Pellets] The thermoplastic resin composition is preferably in pellet form. A thermoplastic resin composition in pellet form can be more preferably used in the manufacture of optical films by melt extrusion. Specific examples of optical films are not particularly limited, but include, for example, polarizer protective films, anti-glare films, and light-diffusing films.

[0078] The thermoplastic resin composition according to this embodiment may be applicable to other uses, insofar as it is suitably used for the manufacture of optical films by the melt extrusion method. For example, it may be used for the manufacture of optical films by the solution casting method. It may also be used for the manufacture of optical components other than optical films (such as sheet-like or plate-like molded bodies, cover members, etc.). The optical components may be injection-molded bodies.

[0079] <Method for Manufacturing Pellets> The second embodiment of the present disclosure is a method for manufacturing pellets made of a thermoplastic resin composition for optical films, comprising a thermoplastic resin and an inorganic light-diffusing agent including a needle-shaped light-diffusing agent, and uses a melt extruder comprising a cylinder extending in the axial direction, a screw disposed in the cylinder, a main feed port provided in the cylinder, a side feed port provided downstream of the main feed port in the extrusion direction, a die with nozzle holes formed therein, and a polymer filter provided upstream of the die, and comprises the steps of: feeding the thermoplastic resin into the melt extruder from the main feed port and feeding the inorganic light-diffusing agent into the melt extruder from the side feed port to melt-knead the thermoplastic resin and the inorganic light-diffusing agent to obtain a thermoplastic resin composition; and filtering the thermoplastic resin composition with a polymer filter and then extruding it from the melt extruder, wherein the inorganic light-diffusing agent fed into the side feed port has an aspect ratio D50 of 3.0 or more at which the cumulative frequency in the number-based aspect ratio distribution reaches 50%.

[0080] [Thermoplastic Resin] The thermoplastic resin may be one of those listed in the description of the thermoplastic resin composition according to the first embodiment. The thermoplastic resin preferably contains a (meth)acrylic resin. The (meth)acrylic resin preferably contains the above-described ring structural unit (q). The ring structural unit (q) preferably contains at least one selected from the group consisting of lactone ring structural units, glutarimide structural units, and succinimide structural units, more preferably contains at least one selected from the group consisting of lactone ring structural units and glutarimide structural units, and even more preferably contains lactone ring structural units.

[0081] The content of (meth)acrylic resin in the thermoplastic resin composition is preferably 65% ​​by mass or more and 99% by mass or less, more preferably 70% by mass or more and 95% by mass or less, and even more preferably 75% by mass or more and 90% by mass or less.

[0082] [Inorganic Light Diffuser] The inorganic light diffuser and needle-shaped light diffuser may be those listed in the description of the thermoplastic resin composition according to the first embodiment. The inorganic light diffuser preferably contains at least one selected from the group consisting of calcium carbonate, titanium dioxide, magnesium sulfate, and aluminum borate, and more preferably contains calcium carbonate. The needle-shaped light diffuser preferably contains at least one selected from the group consisting of calcium carbonate, titanium dioxide, magnesium sulfate, and aluminum borate, and more preferably contains calcium carbonate.

[0083] The needle-shaped light diffuser may be particles with an aspect ratio of 2.0 or greater, particles with an aspect ratio of 2.7 or greater, or particles with an aspect ratio of 3.0 or greater. As long as the above aspect ratios are met, the needle-shaped light diffuser is not limited to a needle shape, but may also have columnar or spindle-shaped forms.

[0084] The inorganic light diffusing agent may have an aspect ratio D50 at which the cumulative frequency in the number-based aspect ratio distribution reaches 50% be between 2.0 and 5.0, between 2.2 and 4.5, or between 2.4 and 4.0.

[0085] The inorganic light diffusing agent may have a major axis D50 of 5.0 μm or more and 10.0 μm or less at which the cumulative frequency in the number-based major axis distribution reaches 50%, or it may have a major axis D50 of 5.2 μm or more and 9.5 μm or less, or it may have a major axis D50 of 5.4 μm or more and 9.0 μm or less.

[0086] When the aspect ratio D50 of the inorganic light diffusing agent is 2.0 or more and 5.0 or less, the major axis D50 may be 5.0 μm or more and 10.0 μm or less, 5.2 μm or more and 9.5 μm or less, or 5.4 μm or more and 9.0 μm or less.

[0087] When the major axis D50 of the inorganic light diffusing agent is 5.0 μm or more and 10.0 μm or less, the aspect ratio D50 may be 2.0 or more and 5.0 or less, 2.2 or more and 4.5 or less, or 2.4 or more and 4.0 or less.

[0088] The aspect ratio D10, aspect ratio D90, maximum aspect ratio, percentage of particles with an aspect ratio of 5 or more, major axis D10, major axis D90, and maximum major axis of the inorganic light diffusing agent may be those listed in the description of the thermoplastic resin composition according to the first embodiment.

[0089] The content of the inorganic light diffusing agent in the thermoplastic resin composition is preferably 1% by mass or more and 5% by mass or less. This allows for a good balance between the light diffusing properties and total light transmittance of the optical film produced from the pellets (thermoplastic resin composition).

[0090] [Characteristics of the Thermoplastic Resin Composition] The glass transition temperature of the thermoplastic resin composition is preferably 110°C to 160°C, more preferably 115°C to 150°C, and even more preferably 120°C to 140°C.

[0091] [Melting Extruder] In the pellet manufacturing method according to this embodiment, a melting extruder is used. The melting extruder comprises a cylinder extending in the axial direction, a screw disposed inside the cylinder, a main feed port provided in the cylinder, a side feed port provided downstream of the main feed port in the extrusion direction, a die with nozzle holes formed therein, and a polymer filter provided upstream of the die.

[0092] The main feed port is an opening into the cylinder, located at the upstream end in the extrusion direction. The main feed port is connected via piping to, for example, a resin hopper, polymerization vessel, or other melt extruder. The polymerization vessel is a manufacturing apparatus for preparing thermoplastic resin to be fed into the melt extruder.

[0093] The screw is connected to a drive device for driving the screw. Specific examples of the screw are not particularly limited, but for example, it may have, in order from the upstream side, a feed section with the smallest groove diameter, a compression section where the groove diameter increases as it moves downstream, and a metering section with the smallest groove diameter. The screw is not particularly limited, but for example, it may be a full-flight screw or a dalmage screw. The L / D ratio of the screw may be 30 to 60 or 40 to 55. There may be one screw or two screws. There may be one screw or two screws. If there are two screws, the two screws may rotate in the same direction or in opposite directions.

[0094] A side feed port is an opening to the cylinder, located downstream of the main feed port in the extrusion direction. The side feed port is connected to, for example, a known side feeder. There may be one side feed port or two or more side feed ports.

[0095] The melt extruder may be equipped with vents for removing volatile components. The vents may be vacuum vents connected to known pumps such as rotary pumps or diffusion pumps, or open vents that are open to the atmosphere. There may be one vent or two or more vents.

[0096] Polymer filters are typically located at the downstream end of the cylinder. Specific examples of polymer filters are not limited to leaf-disk type filters or candle-type filters. The filtration accuracy of the polymer filter may be between 20 μm and 60 μm, or between 30 μm and 50 μm. This allows for the suppression of clogging of the polymer filter by inorganic light diffusing agents and the removal of foreign matter.

[0097] The die is located at the downstream end of the melt extruder. It is configured so that the thermoplastic resin composition, filtered through the polymer filter, is extruded from the melt extruder through the nozzle holes.

[0098] A pelletizer is positioned downstream of the melt extruder. The pelletizer may be of the strand-cutting type, the hot-cutting type, or the underwater-cutting type. The pelletizer may also be configured as part of the melt extruder.

[0099] [Melting and Mixing Process] In the pellet manufacturing method according to this embodiment, a thermoplastic resin is introduced into a melt extruder from the main feed port, and an inorganic light diffusing agent is introduced into the melt extruder from the side feed port, thereby melting and mixing the thermoplastic resin and the inorganic light diffusing agent to obtain a thermoplastic resin composition containing an inorganic light diffusing agent including needle-shaped light diffusing agents. This method makes it possible to suppress the breakage of the needle-shaped light diffusing agents during melting and mixing.

[0100] The method of feeding the thermoplastic resin is not particularly limited, but for example, a resin hopper may be connected to the main feed port and thermoplastic resin pellets may be fed into the resin hopper, a polymerization vessel may be connected to the main feed port and thermoplastic resin prepared in the polymerization vessel may be fed in, or another melt extruder may be connected to the main feed port and thermoplastic resin pre-treated in the other melt extruder may be fed in. The feeding rate of the thermoplastic resin may be 30 kg / hour or more and 900 kg / hour or less in terms of resin volume. Inside the cylinder, the thermoplastic resin may be heated to a temperature of, for example, 200°C or more and 300°C or less.

[0101] The method for introducing the inorganic light diffusing agent is not particularly limited, but for example, it may be introduced using a side feeder. The introduction rate of the inorganic light diffusing agent may be between 0.3 kg / hour and 40 kg / hour.

[0102] This section describes the side feed port (A), which is the input port for the inorganic light diffusing agent. The distance from the side feed port (A) to the polymer filter in the axial direction of the cylinder is L. １ The outer diameter of the screw, including the threads, between the side feed port (A) and the polymer filter is D. １ As the ratio (L １ / D １The ratio of the needle-shaped light diffuser during melt mixing is preferably 8 to 30, and more preferably 10 to 25. This further suppresses the breakage of the needle-shaped light diffuser during melt mixing. The position of the side feed port (A) is set to the center of the side feed port (A) in the axial direction of the cylinder. In addition, the outer diameter D including the screw threads is set between the side feed port (A) and the polymer filter. １ If the outer diameter D is not constant, the average of the maximum and minimum values ​​is used. １ Let's assume that.

[0103] The distance from the main feed port to the polymer filter in the axial direction of the cylinder is L. ２ For example, the distance from the side feed port (A) to the polymer filter is 0.15 L ２ 0.55L ２ The following is also preferable. This makes it possible to further suppress the breakage of the needle-shaped light diffuser during melt mixing.

[0104] It is also preferable to add the inorganic light diffusing agent to a thermoplastic resin heated to a temperature of (Tg + 120)°C or higher and 300°C or lower, with the glass transition temperature of the thermoplastic resin being Tg (°C). This method further suppresses the breakage of the needle-shaped light diffusing agent during melt mixing.

[0105] The inorganic light diffusing agent introduced into the side feed port (A) has an aspect ratio D50 of 3.0 or higher at which the cumulative frequency in the number-based aspect ratio distribution reaches 50%. Since such an inorganic light diffusing agent has an aspect ratio D50 of 3.0 or higher, it includes needle-shaped light diffusing agents. The aspect ratio D50 may be between 3.0 and 6.0, between 3.2 and 5.8, or between 3.4 and 5.5.

[0106] The inorganic light diffusing agent introduced into the side feed port (A) may have a major axis D50 of 6.0 μm or more and 10.5 μm or less at which the cumulative frequency in the number-based major axis distribution reaches 50%, or it may have a major axis D50 of 6.5 μm or more and 10.3 μm or less, or it may have a major axis D50 of 7.0 μm or more and 10.0 μm or less.

[0107] The inorganic light diffusing agent introduced into the side feed port (A) may have a major axis D50 of 6.0 μm to 10.5 μm, 6.5 μm to 10.3 μm, or 7.0 μm to 10.0 μm, when the aspect ratio D50 is 3.0 to 6.0.

[0108] The inorganic light diffusing agent introduced into the side feed port (A) has a major axis D50 of 6.0 μm or more and 10.5 μm or less, and its aspect ratio D50 may be 3.0 or more and 6.0 or less, 3.2 or more and 5.8 or less, or 3.4 or more and 5.5 or less.

[0109] The inorganic light diffusing agent introduced into the side feed port is melt-mixed with the thermoplastic resin inside the cylinder. In this way, a thermoplastic resin composition containing the thermoplastic resin and the inorganic light diffusing agent can be obtained.

[0110] [Pelletization Process] In the pellet manufacturing method according to this embodiment, the thermoplastic resin composition is filtered through a polymer filter and then extruded from a melt extruder through nozzle holes formed in a die. The thermoplastic resin composition extruded from the melt extruder is subjected to a pelletizer to be pelletized.

[0111] The aspect ratio D50 of the inorganic light diffusing agent introduced into the side feed port (A) is set to X １ As such, the aspect ratio D50 of the inorganic light diffusing agent contained in the pellet is set to X ２ As the ratio (X ２ / X １ ) may be 0.65 or more and 0.99 or less, 0.70 or more and 0.98 or less, or 0.75 or more and 0.97 or less.

[0112] The major axis D50 of the inorganic light diffusing agent introduced into the side feed port (A) is Y １ As such, the major axis D50 of the inorganic light diffusing agent contained in the pellet is Y ２ As the ratio (Y ２ / Y １ ) may be 0.40 or more and 0.99 or less, 0.50 or more and 0.95 or less, or 0.60 or more and 0.90 or less.

[0113] <Optical Film> A third embodiment of this disclosure is an optical film containing a thermoplastic resin and an inorganic light diffusing agent. The optical film according to this embodiment may be an optical film made of the thermoplastic resin composition according to the first embodiment.

[0114] [Thermoplastic Resin] The thermoplastic resin may be one of those listed in the description of the thermoplastic resin composition according to the first embodiment. The thermoplastic resin preferably contains a (meth)acrylic resin. The (meth)acrylic resin preferably contains the above-described ring structural unit (q). The ring structural unit (q) preferably contains at least one selected from the group consisting of lactone ring structural units, glutarimide structural units, and succinimide structural units, more preferably contains at least one selected from the group consisting of lactone ring structural units and glutarimide structural units, and even more preferably contains lactone ring structural units.

[0115] The thermoplastic resin content in the thermoplastic resin composition is preferably 65% ​​by mass or more and 99% by mass or less, more preferably 70% by mass or more and 95% by mass or less, and even more preferably 75% by mass or more and 90% by mass or less.

[0116] [Inorganic Light Diffuser] The inorganic light diffuser may be one of those listed in the description of the thermoplastic resin composition according to the first embodiment. The inorganic light diffuser preferably contains at least one selected from the group consisting of calcium carbonate, titanium dioxide, magnesium sulfate, and aluminum borate, and more preferably contains calcium carbonate. The content of the inorganic light diffuser in the thermoplastic resin composition is preferably 1% by mass or more and 5% by mass or less.

[0117] [Characteristics of the Thermoplastic Resin Composition] The glass transition temperature of the thermoplastic resin composition is preferably 110°C to 160°C, more preferably 115°C to 150°C, and even more preferably 120°C to 140°C.

[0118] The thickness of the optical film is preferably 10 μm or more and 100 μm or less. This allows for a good balance between the light diffusion and total light transmittance of the optical film. The thickness of the optical film can be measured by the method described in the examples below.

[0119] The total light transmittance of the optical film is preferably 85% or higher, and more preferably 90% or higher. This allows for a good balance between the light diffusion properties and total light transmittance of the optical film. The total light transmittance of the optical film can be measured by the method described in the examples below.

[0120] [First Optical Film] An example of an optical film according to the third embodiment, the first optical film, will be described. The first optical film contains a thermoplastic resin and an inorganic light diffusing agent including a needle-shaped light diffusing agent, and is a rectangular optical film having a pair of first sides extending in a first direction and a pair of second sides extending in a second direction perpendicular to the first direction, wherein when light is irradiated perpendicularly to the main surface of the optical film, the first average light transmittance transmitted by refracting at an angle of 10 degrees or more and 15 degrees or less in the first direction is T １ Let T be the second average light transmittance that is refracted and transmitted in the second direction at an angle of 10 degrees to 15 degrees. ２ When this is the case, the ratio (T ２ / T １ ) is 2.5 or more and 10 or less, and the second average light transmittance T ２ This optical film is characterized by having a concentration of 1.5% or more and 5.0% or less.

[0121] First average light transmittance T １This can be measured using a variable-angle photometer. First, the light source is placed on one side of the optical film and the light receiver on the other side, such that the optical axis from the light source to the light receiver is perpendicular to the principal surface of the optical film. The position of the light receiver at this time is defined as the "position with a receiving angle of 0°". Then, the light transmittance is measured while moving the light receiver on the circumference of a virtual circle that is included in the plane containing the first direction, with the intersection point of the optical axis and the optical film as the center, including the "position with a receiving angle of 0°", and the distance from the intersection point to the "position with a receiving angle of 0°" as the radius. Next, the light transmittance is measured by moving the light receiver 10 degrees in the circumferential direction. The light transmittance at this time is defined as the light transmittance at the "position with a receiving angle of 10°". Then, the light transmittance is measured again by moving it another 0.1 degrees in the same circumferential direction. The light transmittance at this time is defined as the light transmittance at the "position with a receiving angle of 10.1°". Next, the light transmittance is measured from the "receiving angle of 10°" to the "receiving angle of 15°" while shifting the position of the light receiver by 0.1 degrees at a time. Then, the light transmittance is measured again by moving the light receiver 10 degrees in the opposite direction circumferentially from the "receiving angle of 0°" position. The light transmittance at this point is taken as the light transmittance at the "receiving angle of -10°" position. Similarly, the light transmittance is measured from the "receiving angle of -10°" to the "receiving angle of -15°" while shifting the position of the light receiver by 0.1 degrees at a time. The average of the 102 measurement results is then taken as the first average light transmittance T. １ Let's assume that.

[0122] Second average light transmittance T ２ is also the first average light transmittance T １ The second average light transmittance T can be calculated using the same method. ２ To measure this, the light transmittance should be measured while moving the photodetector along the circumference of a virtual circle that is included in a plane containing the second direction, with the intersection point of the optical axis and the optical film as the center, including the "position with a light receiving angle of 0°", and the distance from the intersection point to the "position with a light receiving angle of 0°" as the radius.

[0123] Typically, optical films are incorporated into image display devices so that their longitudinal direction is horizontal. The image display devices are then installed at a height similar to the user's eye level. Considering this usage scenario, it is preferable that the optical film has its short-length direction as the first direction and its longitudinal direction as the second direction. This enhances light diffusion in the horizontal direction, allowing for the provision of beautiful images and videos to people viewing the image display device from an oblique angle.

[0124] Image display devices may be installed at a height well above the user's eye level, depending on their purpose. Considering such usage scenarios, it is preferable that the optical film has its longitudinal direction in the first direction and its short direction in the second direction. This enhances light diffusion in the vertical direction, allowing for the provision of beautiful images and videos to people viewing the image display device from an oblique angle.

[0125] The needle-shaped light diffuser may be one of those listed in the description of the thermoplastic resin composition according to the first embodiment. The needle-shaped light diffuser may be particles with an aspect ratio of 2.0 or more, particles with an aspect ratio of 2.7 or more, or particles with an aspect ratio of 3.0 or more. As long as the above aspect ratios are satisfied, the needle-shaped light diffuser is not limited to a needle shape, but may also have a columnar or spindle shape. The needle-shaped light diffuser preferably contains at least one selected from the group consisting of calcium carbonate, titanium dioxide, magnesium sulfate, and aluminum borate, and more preferably contains calcium carbonate.

[0126] The inorganic light diffusing agent may have an aspect ratio D50 at which the cumulative frequency in the number-based aspect ratio distribution reaches 50% be between 1.6 and 5.0, between 1.8 and 4.5, or between 2.0 and 4.0.

[0127] The inorganic light diffusing agent may have a major axis D50 of 4.0 μm or more and 10.0 μm or less at which the cumulative frequency in the number-based major axis distribution reaches 50%, or it may have a major axis D50 of 4.5 μm or more and 9.5 μm or less, or it may have a major axis D50 of 5.0 μm or more and 9.0 μm or less.

[0128] When the aspect ratio D50 of the inorganic light diffusing agent is 1.6 or more and 5.0 or less, the major axis D50 may be 4.0 μm or more and 10.0 μm or less, 4.5 μm or more and 9.5 μm or less, or 5.0 μm or more and 9.0 μm or less.

[0129] When the major axis D50 of the inorganic light diffusing agent is 4.0 μm or more and 10.0 μm or less, the aspect ratio D50 may be 1.6 or more and 5.0 or less, 1.8 or more and 4.5 or less, or 2.0 or more and 4.0 or less.

[0130] The aspect ratio D10, aspect ratio D90, maximum aspect ratio, percentage of particles with an aspect ratio of 5 or more, major axis D10, major axis D90, and maximum major axis of the inorganic light diffusing agent may be as described in the description of the thermoplastic resin composition according to the first embodiment.

[0131] [Second Optical Film] A second optical film, which is another example of the optical film according to the third embodiment, will now be described. The second optical film is an optical film made of a thermoplastic resin composition containing a thermoplastic resin and an inorganic light diffusing agent, wherein the inorganic light diffusing agent has an aspect ratio D50 at which the cumulative frequency in the number-based aspect ratio distribution reaches 50% is 1.6 or more and 5.0 or less, and a major axis D50 at which the cumulative frequency in the number-based major axis distribution reaches 50% is 4.0 μm or more and 10.0 μm or less.

[0132] The inorganic light diffusing agent may have an aspect ratio D50, where the cumulative frequency in the number-based aspect ratio distribution reaches 50%, be between 1.8 and 4.5, or between 2.0 and 4.0.

[0133] The inorganic light diffusing agent may have a major axis D50 of 4.5 μm or more and 9.5 μm or less at which the cumulative frequency in the number-based major axis distribution reaches 50%, or it may have a major axis D50 of 5.0 μm or more and 9.0 μm or less.

[0134] When the aspect ratio D50 of the inorganic light diffusing agent is 1.6 or more and 5.0 or less, the major axis D50 may be 4.5 μm or more and 9.5 μm or less, or 5.0 μm or more and 9.0 μm or less.

[0135] When the major axis D50 of the inorganic light diffusing agent is 4.0 μm or more and 10.0 μm or less, the aspect ratio D50 may be 1.8 or more and 4.5 or less, or 2.0 or more and 4.0 or less.

[0136] The aspect ratio D10, aspect ratio D90, maximum aspect ratio, percentage of particles with an aspect ratio of 5 or more, major axis D10, major axis D90, and maximum major axis of the inorganic light diffusing agent may be as described in the description of the thermoplastic resin composition according to the first embodiment.

[0137] The inorganic light diffusing agent preferably contains a needle-shaped light diffusing agent. The needle-shaped light diffusing agent may be one of those listed in the description of the thermoplastic resin composition according to the first embodiment. The needle-shaped light diffusing agent may be particles with an aspect ratio of 2.0 or more, particles with an aspect ratio of 2.7 or more, or particles with an aspect ratio of 3.0 or more. As long as the above aspect ratio is satisfied, the needle-shaped light diffusing agent is not limited to a needle shape, but may also have a columnar or spindle shape. The needle-shaped light diffusing agent preferably contains calcium carbonate.

[0138] The optical film may be a stretched film, specifically a uniaxially stretched film or a biaxially stretched film.

[0139] The optical film may be in roll form, or it may be processed to a size that can be incorporated into an image display device.

[0140] The optical film is rectangular in shape, having a pair of first sides extending in a first direction and a pair of second sides extending in a second direction perpendicular to the first direction. When light is shone perpendicularly onto the main surface of the optical film, the first average light transmittance is defined as the light that is refracted and transmitted in the first direction at an angle of 10 degrees to 15 degrees. １ Let T be the second average light transmittance that is refracted and transmitted in the second direction at an angle of 10 degrees to 15 degrees. ２ When this is the case, the ratio (T ２ / T １ ) is 2.5 or more and 10 or less, and the second average light transmittance T ２It is preferable that the amount is 1.5% or more and 5.0% or less. First average light transmittance T １ and the second average light transmittance T ２ The measurement method may be one of those described in the first optical film description.

[0141] [Method for Manufacturing Optical Films] An example of a method for manufacturing optical films according to this embodiment will be described. This manufacturing method is a so-called melt extrusion method (T-die method).

[0142] The melt extruder used in this melt extrusion method may be the same as that described in the description of the pellet manufacturing method according to the second embodiment, except that a T-die is positioned downstream instead of a pelletizer. The filtration accuracy of the polymer filter provided in the melt extruder may be 20 μm or more and 60 μm or less, or 30 μm or more and 50 μm or less. This makes it possible to suppress clogging of the polymer filter by the inorganic light diffuser and to make it easier to orient the inorganic light diffuser by passing it through the polymer filter.

[0143] The thermoplastic resin composition extruded from the melt extruder is formed into a film (sheet). For the sake of explanation, the thermoplastic resin composition formed into a film is referred to here as the raw material film.

[0144] The raw film roll is stretched using a stretcher located downstream of the T-die. The stretcher may consist of only a longitudinal stretcher, only a transverse stretcher, or both in that order. This explanation will focus on the case where the longitudinal stretcher and transverse stretcher are arranged in that order.

[0145] The raw film roll is transported to a longitudinal stretching machine using transport rollers and subjected to longitudinal stretching (MD stretching). The longitudinal stretching machine stretches the raw film roll by utilizing the difference in peripheral speed of the transport rollers that transport the film. In other words, by making the peripheral speed of the downstream roller faster than the peripheral speed of the upstream roller in two consecutive transport rollers, the raw film roll can be stretched longitudinally.

[0146] In longitudinal stretching, the stretching ratio may be 1.4 times or more and 3.5 times or less, or 1.6 times or more and 3.0 times or less. If the glass transition temperature of the thermoplastic resin composition forming the base film is Tg (°C), the stretching temperature may be Tg + 7°C or more and Tg + 30°C or less, or Tg + 10°C or more and Tg + 24°C or less. The stretching speed may be 10% / min or more and 20000% / min or less.

[0147] The primary stretched film, which is obtained by stretching the raw film roll longitudinally, is transported to a transverse stretching machine using transport rollers and stretched transversely (TD stretching). The transverse stretching machine is also called a tenter stretching machine. The transverse stretching machine stretches the primary stretched film by gripping both ends in the width direction of the primary stretched film with clips. In other words, the primary stretched film can be stretched transversely by increasing the distance between the clips while transporting the primary stretched film.

[0148] In transverse stretching, the stretching ratio may be 1.3 times or more and 3.0 times or less, or 1.4 times or more and 2.7 times or less. If the glass transition temperature of the thermoplastic resin composition forming the primary stretched film is Tg (°C), the stretching temperature may be Tg + 7°C or more and Tg + 30°C or less, or Tg + 10°C or more and Tg + 24°C or less. The stretching speed may be 10% / min or more and 2000% / min or less.

[0149] By adjusting the stretching ratio and stretching temperature for longitudinal stretching, and for transverse stretching, the orientation of the inorganic light diffuser can be adjusted, thereby controlling the anisotropy of light diffusion in the manufactured optical film. For example, by setting the longitudinal stretching ratio higher than the transverse stretching ratio, the inorganic light diffuser becomes more likely to orient in the longitudinal stretching direction. Similarly, by setting the longitudinal stretching temperature lower than the transverse stretching temperature, the inorganic light diffuser becomes more likely to orient in the longitudinal stretching direction.

[0150] After transverse stretching, heat treatment (annealing) may be performed as needed. When heat treatment is performed, the heat treatment temperature is preferably between Tg -10°C and Tg +10°C, and more preferably between Tg -5°C and Tg +5°C.

[0151] Furthermore, a primer layer may be applied to the primary stretched film between longitudinal and transverse stretching. The primer layer is also called an easy-adhesion layer or an easy-slip layer. There are no particular limitations on specific examples of the primer layer, but for example, as described in Japanese Patent Publication No. 2009-193061 and Japanese Patent Publication No. 2010-55062, it may contain a matrix resin, a crosslinking agent and fine particles, or it may not contain a crosslinking agent and / or fine particles. The thickness of the primer layer may be adjusted as appropriate.

[0152] The secondary stretched film (optical film), which is obtained by transversely stretching the primary stretched film, is transported to a winding machine using transport rollers, where it is made into a film roll.

[0153] [Applications of the optical film] The optical film according to this embodiment is not particularly limited, but can be suitably used as, for example, a polarizer protective film, an anti-glare film, or a light-diffusing film.

[0154] <Image Display Device Components and Image Display Devices> This disclosure also includes an image display device component comprising an optical film according to the third embodiment and an image display device comprising the same. Specific examples of the image display device component include, but are not limited to, polarizing plates and light diffusing plates. Specific examples of the image display device include, but are not limited to, liquid crystal displays.

[0155] This disclosure will be described in detail with reference to examples. However, this disclosure is not limited to these examples.

[0156] (1) Glass transition temperature of thermoplastic resins The glass transition temperature of thermoplastic resins was measured in accordance with the provisions of Japanese Industrial Standard (JIS) K 7121. Specifically, a differential scanning calorimeter (Rigaku Corporation, Thermo plus EVO DSC-8230) was used to measure the temperature from the starting point method by heating approximately 10 mg of a sample from room temperature to 200°C (heating rate 20°C / min) in a nitrogen gas atmosphere using the DSC curve obtained. α-alumina was used as the reference.

[0157] (2) Weight-average molecular weight and number-average molecular weight of thermoplastic resins The weight-average molecular weight and number-average molecular weight of thermoplastic resins were measured using gel permeation chromatography (GPC) on a polystyrene basis. The measurement equipment and conditions are as follows: Measurement system: GPC system HLC-8220, manufactured by Tosoh Corporation Measurement side column configuration: ・Guard column (TSK Gel guard column Super HZ-L, manufactured by Tosoh Corporation) ・Separation column (TSK Gel Super HZM-M, manufactured by Tosoh Corporation), two connected in series Reference side column configuration: ・Reference column (TSK gel Super H-RC, manufactured by Tosoh Corporation) Developing solvent: Chloroform (Special grade, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Flow rate of developing solvent: 0.6 mL / min Standard sample: TSK standard polystyrene (PS-oligomer kit, manufactured by Tosoh Corporation) Column temperature: 40°C

[0158] (3) Aspect ratio and major diameter of inorganic light diffuser (raw material) fed into the melt extruder The aspect ratio and major diameter of the inorganic light diffuser (raw material) fed into the melt extruder were measured using a particle shape image analyzer (Seishin Co., Ltd., PITA-04). Specifically, the following was done: - Preparation of the measurement sample A dispersion was prepared by dispersing 0.09 g of inorganic light diffuser (raw material) in 4.50 g of acetone. 0.02 g of anionic surfactant (Kao Corporation, Neoperex G-15) was added to 0.6 g of the dispersion. Ultrapure water was added to make a total of 7.5 g, and then dispersed with ultrasound for 5 minutes to prepare the measurement sample. - Measurement Approximately 2 to 5 ml of the measurement sample was placed in the particle shape image analyzer, and 5000 inorganic light diffusers were measured. The aspect ratio D50 at which the cumulative frequency of 50% of the number-based aspect ratio of 5000 inorganic light diffusers was measured, with the cumulative aspect ratio of 5000 inorganic light diffusers set to 100%. Similarly, the major axis D50 at which the cumulative frequency of 50% of the number-based major axis of 5000 inorganic light diffusers was measured, with the cumulative major axis of 500% set to 100%. *Analysis conditions: Only inorganic light diffusers meeting the following conditions were counted: Area: 0–70 (μm²) ２ ) Minor axis: 0 to 7 (μm) Perimeter: 1 to 100 (μm) Circularity: 0 to 1

[0159] (4) Aspect ratio and major diameter of inorganic light diffusing agent contained in pellets and optical film The aspect ratio and major diameter of inorganic light diffusing agent contained in pellets and optical film were measured using a particle shape image analyzer (Seishin Co., Ltd., PITA-04). Specifically, the following was done: - Preparation of measurement sample 3 g of pellet or optical film (approximately 0.09 g in terms of inorganic light diffusing agent) was dissolved in chloroform and filtered under reduced pressure through a PTFE membrane filter with a mesh size of 0.5 μm. The residue was dispersed in 4.50 g of acetone to prepare a dispersion. 0.02 g of anionic surfactant (Kao Corporation, Neoperex G-15) was added to 0.6 g of the dispersion. Ultrapure water was added to make a total of 7.5 g, and then dispersed with ultrasound for 5 minutes to prepare the measurement sample. - Measurement Approximately 2 to 5 ml of the measurement sample was placed in the particle shape image analyzer, and 5000 inorganic light diffusing agents were measured. The aspect ratio D50, where the cumulative aspect ratio of 5000 inorganic light diffusers was set to 100%, was measured. In addition, aspect ratios D10, D90, the maximum aspect ratio, and the percentage of particles with an aspect ratio of 5 or greater were measured. Similarly, the major axis D50, where the cumulative major axis of 5000 inorganic light diffusers was set to 100%, was measured. In addition, major axis D10, D90, and the maximum major axis were measured. Only particles meeting the following conditions were counted: Area: 0-70 (μm²) ２ ) Minor axis: 0 to 7 (μm) Perimeter: 1 to 100 (μm) Circularity: 0 to 1

[0160] (5) Thickness of the optical film The thickness of the optical film was measured using a Digimatic micrometer (manufactured by Mitutoyo Corporation).

[0161] (6) Total light transmittance of optical film The total light transmittance of optical film was measured in accordance with the provisions of JIS K 7361. Specifically, it was measured using a haze meter (Nippon Denshoku Industries, NDH-1001DP).

[0162] (7) The first average light transmittance T of the optical film １ and the second average light transmittance T ２ The first average light transmittance T of the optical film １ and the second average light transmittance T２ The measurement was performed using a variable-angle photometer (Murakami Color Technology Laboratory, Goniophotometer GP-5). After placing the optical film between the light source and the light receiver, the amount of light emitted from the light source was set so that the transmitted light intensity detected by the light receiver at the "receiving angle 0° position" was 1700. The horizontal direction when the optical film is placed so that the transverse extension (TD) direction is aligned with the vertical direction, i.e., the MD direction of the optical film, was defined as the first direction, and the first average light transmittance T of light refracted and transmitted in the first direction at an angle of 10 degrees or more and 15 degrees or less was defined. １ The second direction was defined as the horizontal direction, i.e., the TD direction of the optical film, when the optical film is positioned so that the longitudinal extension (MD) direction is aligned with the vertical direction. The second average light transmittance T of light that is refracted and transmitted in the second direction at an angle of 10 to 15 degrees was measured. ２ We measured it.

[0163] [Experimental Example 1-1] In a reaction vessel equipped with a stirrer, temperature sensor, condenser, and nitrogen inlet tube, 83.5 parts by mass of methyl methacrylate, 12 parts by mass of methyl 2-(hydroxymethyl)acrylate, 88.7 parts by mass of toluene, and 0.05 parts by mass of tris(2,4-di-t-butylphenyl) phosphite (ADEKA Corporation: ADEKA Stab® 2112), an antioxidant, were charged, and the mixture was heated to 105°C while nitrogen was passed through it. When reflux began as the temperature rose, 0.435 parts by mass of a toluene solution (Arkema Yoshitomi Co., Ltd.: Lupelox® 570T20), in which the polymerization initiator t-amyl peroxyisononanoate was concentrated at a concentration of 20% by mass, was added. Subsequently, a solution consisting of 4.5 parts by mass of styrene and 0.15 parts by mass of n-dodecyl mercaptan was added dropwise over 2 hours. Furthermore, 0.865 parts by mass of a toluene solution containing 20% ​​by mass of t-amyl peroxyisononanoate was added dropwise over 4 hours. During the addition, the mixture was refluxed at approximately 105-110°C to allow solution polymerization to proceed. After the addition was complete, the mixture was aged at the same temperature for a further 2 hours.

[0164] 0.075 parts by mass of stearyl phosphate (SC Organic Chemicals: Phoslex A-18) was added to the obtained polymerization solution, and a cyclization-condensation reaction to form a lactone ring structure was carried out under reflux at approximately 90-110°C for 2 hours. The obtained polymerization solution was passed through a multi-tube heat exchanger heated to 240°C to complete the cyclization-condensation reaction.

[0165] The obtained polymerization solution was introduced into the main feed port of a melt extruder (vented-type screw twin-screw extruder (L / D = 49, D = 47 mm)) at a rate of 100 parts by mass / hour (35.9 kg / hour) in terms of resin volume. The melt extruder is equipped with one rear vent and four fore vents (referred to as the first, second, third, and fourth vents from the upstream side), and also has a side feed port with a side feeder connected between the third and fourth vents, and a leaf disc type filter (filtration accuracy 40 μm) and die are located downstream. Devastation was performed with the cylinder internal temperature set to 250°C, the pressure at the rear vent set to 798 hPa, the pressure at the first vent set to 266 hPa, and the pressure at the second to fourth vents set to 27 hPa. Furthermore, ion-exchanged water was introduced at a rate of 1.5 parts by mass / hour from the downstream of the second and third vents, needle-shaped calcium carbonate was introduced at a rate of 3 parts by mass / hour from the side feed port, and a solution of 0.66 parts by mass of ultraviolet absorber (ADEKA Corporation: ADEKA Stub LA-F70) dissolved in 1.23 parts by mass of toluene was introduced at a rate of 1.89 parts by mass / hour from the downstream of the fourth vent. Finally, the molten mixture filtered through a leaf-disc type filter was extruded from a molten extruder to obtain pellets of a methacrylic resin composition containing lactone ring structural units and needle-shaped calcium carbonate. Measurements of the obtained pellets showed a glass transition temperature of 122°C, a weight-average molecular weight of 133,000, and a number-average molecular weight of 52,000.

[0166] [Experimental Example 1-2] Except for changing the position of the side feed port for introducing needle-shaped calcium carbonate, pellets of a methacrylic resin composition containing lactone ring structural units and needle-shaped calcium carbonate were obtained in the same manner as in Experimental Example 1-1. When the obtained pellets were measured, the glass transition temperature was 122°C, the weight-average molecular weight was 133,000, and the number-average molecular weight was 52,000.

[0167] [Experimental Example 1-3] In a reaction vessel equipped with a stirrer, temperature sensor, condenser, and nitrogen inlet tube, 83.5 parts by mass of methyl methacrylate, 12 parts by mass of methyl 2-(hydroxymethyl)acrylate, 88.7 parts by mass of toluene, and 0.05 parts by mass of tris(2,4-di-t-butylphenyl) phosphite (ADEKA Corporation: ADEKA Stab® 2112), an antioxidant, were charged, and the mixture was heated to 105°C while nitrogen was passed through it. When reflux began as the temperature rose, 0.435 parts by mass of a toluene solution (Arkema Yoshitomi Co., Ltd.: Lupelox® 570T20), in which the polymerization initiator t-amyl peroxyisononanoate was concentrated at a concentration of 20% by mass, was added. Subsequently, a solution consisting of 4.5 parts by mass of styrene and 0.15 parts by mass of n-dodecyl mercaptan was added dropwise over 2 hours. Furthermore, 0.865 parts by mass of a toluene solution containing 20% ​​by mass of t-amyl peroxyisononanoate was added dropwise over 4 hours. During the addition, the mixture was refluxed at approximately 105-110°C to allow solution polymerization to proceed. After the addition was complete, the mixture was aged at the same temperature for a further 2 hours.

[0168] 0.075 parts by mass of stearyl phosphate (SC Organic Chemicals: Phoslex A-18) was added to the obtained polymerization solution, and a cyclization-condensation reaction to form a lactone ring structure was carried out under reflux at approximately 90-110°C for 2 hours. The obtained polymerization solution was passed through a multi-tube heat exchanger heated to 240°C to complete the cyclization-condensation reaction.

[0169] The obtained polymerization solution was introduced into the main feed port of a melt extruder (vented-type screw twin-screw extruder (L / D = 49, D = 47 mm)) at a rate of 100 parts by mass / hour (35.9 kg / hour) in terms of resin volume. The melt extruder is equipped with one rear vent and four fore vents (referred to as the first, second, third, and fourth vents from the upstream side), and also has a side feed port with a side feeder connected between the third and fourth vents, and a leaf disc type filter (filtration accuracy 5 μm) and die are located downstream. Devastation was performed with the cylinder internal temperature set to 250°C, the pressure at the rear vent set to 798 hPa, the pressure at the first vent set to 266 hPa, and the pressure at the second to fourth vents set to 27 hPa. Furthermore, ion-exchanged water was introduced at a rate of 1.5 parts by mass / hour downstream of the second and third vents, and a solution of 0.66 parts by mass of ultraviolet absorber (ADEKA Corporation: ADEKA Stub LA-F70) dissolved in 1.23 parts by mass of toluene was introduced at a rate of 1.89 parts by mass / hour downstream of the fourth vent. Finally, the molten mixture filtered through a leaf-disc type filter was extruded from a melt extruder to obtain pellets of a methacrylic resin composition containing methacrylic resin with lactone ring structural units. Measurements of the obtained pellets showed a glass transition temperature of 122°C, a weight-average molecular weight of 133,000, and a number-average molecular weight of 52,000.

[0170] 97 parts by mass of pellets and 3 parts by mass of needle-shaped calcium carbonate were fed into the main feed port of a twin-screw extruder (L / D = 34, D = 37 mm) and melt-kneaded at 260°C. Finally, the molten mixture was extruded from the extruder to obtain pellets of a methacrylic resin composition containing lactone ring structural units and needle-shaped calcium carbonate. Measurements of the obtained pellets showed a glass transition temperature of 122°C, a weight-average molecular weight of 133,000, and a number-average molecular weight of 52,000.

[0171] [Experimental Example 1-4] Using the same method as in Experimental Example 1-3, pellets of a methacrylic resin composition containing a methacrylic resin with lactone ring structural units were obtained. The obtained pellets were measured and found to have a glass transition temperature of 122°C, a weight-average molecular weight of 133,000, and a number-average molecular weight of 52,000.

[0172] 97 parts by mass of pellets and 3 parts by mass of needle-shaped calcium carbonate were fed into the main feed port of a twin-screw extruder (L / D = 41, D = 48 mm) and melt-kneaded at 260°C. Finally, the molten mixture was extruded from the extruder to obtain pellets of a methacrylic resin composition containing lactone ring structural units and needle-shaped calcium carbonate. Measurements of the obtained pellets showed a glass transition temperature of 122°C, a weight-average molecular weight of 133,000, and a number-average molecular weight of 52,000.

[0173] For Experimental Examples 1-1 to 1-4, the aspect ratio and major axis of the calcium carbonate fed into the melt extruder as raw material, the aspect ratio and major axis of the calcium carbonate contained in the pellets, and the distance from the side feed port to the polymer filter (referred to as the position of the side feed port in Table 1) and ratio (L) are indicators of the mixing conditions. １ / D １ ), as well as a ratio (X) which serves as an indicator of the degree of fracture of calcium carbonate. ２ / X １ ) and ratio (Y ２ / Y １ Table 1 shows the results. Note that in Experimental Examples 1-3 and 1-4, calcium carbonate is introduced from the main feed port, so the distance from the main feed port to the polymer filter is the same as the distance L from the side feed port to the polymer filter. １ That was my assessment.

[0174]

[0175] From the above, it was found that fracture of the inorganic light diffusing agent can be suppressed by introducing the inorganic light diffusing agent through the side feed port, as shown in Experimental Examples 1-1 to 1-2.

[0176] [Experimental Example 2-1] The pellets obtained in Experimental Example 1-1 were supplied to a single-screw extruder (L / D = 32) equipped with a leaf-disk type filter with a filtration accuracy of 40 μm and a T-die at its tip, and melt-molded at 265°C to produce a raw film with a thickness of 114 μm. The raw film was then transported directly to an oven longitudinal stretcher for longitudinal stretching, and subsequently to a tenter transverse stretcher for transverse stretching to obtain an optical film with a thickness of 40 μm.

[0177] The glass transition temperature of the (meth)acrylic resin composition was defined as Tg. For longitudinal stretching, the stretching temperature was Tg + 16°C, and the stretching ratio was 2.0 times. For transverse stretching, the stretching temperature was Tg + 16°C in the preheating zone, Tg + 16°C in the stretching zone, and Tg - 2°C in the heat treatment zone, with a stretching ratio of 2 times. After slits were made at both ends in the width direction of the optical film, a polyethylene protective film was laminated to form a film roll.

[0178] [Experimental Example 2-2] An optical film with a thickness of 30 μm was obtained using the same method as in Experimental Example 2-1, except that the thickness of the raw film was changed to 86 μm.

[0179] [Experimental Example 2-3] An optical film with a thickness of 60 μm was obtained using the same method as in Experimental Example 2-1, except that the thickness of the raw film was changed to 170 μm.

[0180] [Experimental Example 2-4] An optical film with a thickness of 40 μm was obtained using the same method as in Experimental Example 2-1, except that the pellets obtained in Experimental Example 1-2 were used.

[0181] [Experimental Example 2-5] An optical film with a thickness of 40 μm was obtained using the same method as in Experimental Example 2-1, except that the pellets obtained in Experimental Example 1-3 were used.

[0182] [Experimental Example 2-6] An optical film with a thickness of 40 μm was obtained using the same method as in Experimental Example 2-1, except that the pellets obtained in Experimental Example 1-4 were used.

[0183] For Experimental Examples 2-1 to 2-6, the aspect ratio and major axis of the calcium carbonate contained in the optical film, the thickness of the optical film, the total light transmittance, and the ratio (T) which serves as an indicator of the anisotropy of light diffusion were measured. ２ / T １), and the second average light transmittance T ２ is shown in Table 2.

[0184]

[0185] From the above, as in Experimental Examples 2-1 to 2-4, an optical film containing an inorganic light diffusing agent having a sufficiently large aspect ratio D50 and major diameter D50 has a ratio (T ２ / T １ ) that is sufficiently large, so the anisotropy of light diffusion is good, and since the second average light transmittance T ２ is sufficiently large, it was found that a sufficient amount of light diffuses.

Claims

1. A thermoplastic resin composition for optical films, comprising a thermoplastic resin and an inorganic light diffusing agent dispersed in the thermoplastic resin, wherein the inorganic light diffusing agent has an aspect ratio D50 of 2.0 or more and 5.0 or less at which the cumulative frequency in the number-based aspect ratio distribution reaches 50%, and a major axis D50 of 5.0 μm or more and 10.0 μm or less at which the cumulative frequency in the number-based major axis distribution reaches 50%.

2. The thermoplastic resin composition according to claim 1, wherein the inorganic light diffusing agent has an aspect ratio D10 at which the cumulative frequency in the number-based aspect ratio distribution reaches 10% is 1.3 or more and less than 2.

0.

3. The thermoplastic resin composition according to claim 1, wherein the inorganic light diffusing agent has an aspect ratio D90, which is greater than 5.0 and less than or equal to 9.0, at which point the cumulative frequency in the number-based aspect ratio distribution reaches 90%.

4. The thermoplastic resin composition according to claim 1, wherein the inorganic light diffusing agent has a particle ratio of 5 or more, and the proportion of such particles is more than 10% and 35% or less on a number basis.

5. The thermoplastic resin composition according to claim 1, wherein the inorganic light diffusing agent has a major axis D10 of 2.0 μm or more and less than 5.0 μm at which the cumulative frequency in the number-based major axis distribution reaches 10%.

6. The thermoplastic resin composition according to claim 1, wherein the inorganic light diffusing agent has a major axis D90 of more than 10.0 μm and 25.0 μm or less at which the cumulative frequency in the number-based major axis distribution reaches 90%.

7. The thermoplastic resin composition according to claim 1, wherein the thermoplastic resin comprises a (meth)acrylic resin.

8. The thermoplastic resin composition according to claim 7, wherein the (meth)acrylic resin comprises a ring structure unit having a heterocycle that shares two or more carbon atoms with the main chain.

9. The thermoplastic resin composition according to claim 8, wherein the ring structural unit comprises at least one selected from the group consisting of lactone ring structural units, glutarimide structural units, and succinimide structural units.

10. The thermoplastic resin composition according to claim 1, wherein the inorganic light diffusing agent comprises at least one selected from the group consisting of calcium carbonate, titanium dioxide, magnesium sulfate, and aluminum borate.

11. The thermoplastic resin composition according to claim 1, wherein the content of the inorganic light diffusing agent is 1% by mass or more and 5% by mass or less.

12. The thermoplastic resin composition according to claim 1, wherein the glass transition temperature is 110°C or higher and 160°C or lower.

13. The thermoplastic resin composition according to claim 1, which is a pellet.

14. A method for producing pellets made of a thermoplastic resin composition for optical films, comprising a thermoplastic resin and an inorganic light-diffusing agent containing a needle-shaped light-diffusing agent, wherein a melt extruder is used, comprising a cylinder extending in the axial direction, a screw disposed in the cylinder, a main feed port provided in the cylinder, a side feed port provided downstream of the main feed port in the extrusion direction, a die with nozzle holes formed therein, and a polymer filter provided upstream of the die, the method comprising the steps of: feeding the thermoplastic resin into the melt extruder from the main feed port and feeding the inorganic light-diffusing agent into the melt extruder from the side feed port to melt-knead the thermoplastic resin and the inorganic light-diffusing agent to obtain a thermoplastic resin composition; filtering the thermoplastic resin composition with the polymer filter and then extruding it from the melt extruder, wherein the inorganic light-diffusing agent fed into the side feed port has an aspect ratio D50 of 3.0 or more, at which the cumulative frequency in the number-based aspect ratio distribution reaches 50%.

15. The method for producing pellets according to claim 14, wherein the needle-shaped light diffusing agent is a particle with an aspect ratio of 2.0 or more.

16. The method for producing pellets according to claim 14, wherein the thermoplastic resin includes a (meth)acrylic resin.

17. The distance from the side feed port to the polymer filter in the axial direction is L. １ The outer diameter of the screw, including the threads, between the side feed port and the polymer filter is D. １ As the ratio (L １ / D １ A method for producing pellets according to claim 14, wherein the ratio is 8 or more and 30 or less.

18. The distance from the main feed port to the polymer filter in the axial direction is L. ２ The distance from the side feed port to the polymer filter is 0.15 L. ２ 0.55L ２ The method for producing pellets according to claim 14, as follows:

19. The method for producing pellets according to claim 14, wherein the inorganic light diffusing agent introduced into the side feed port has an aspect ratio D50 of 6.0 or less at which the cumulative frequency in the number-based aspect ratio distribution reaches 50%.

20. The method for producing pellets according to claim 14, wherein the inorganic light diffusing agent introduced into the side feed port has a major axis D50 of 6.0 μm or more and 10.5 μm or less at which the cumulative frequency in the number-based major axis distribution reaches 50%.

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