JP2014092551A - Optical film and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical film which can be efficiently manufactured and offers a superior anti-glare property.SOLUTION: An optical film includes a transparent film and a hard coat layer which is formed on the transparent film and has a concavo-convex structure on a surface thereof, where the hard coat layer is made of a hardened curable composition containing a curable resin precursor and cellulose nanofibers. Protrusions on the surface of the hard coat layer contain cellulose nanofiber aggregates. The cellulose nanofibers constituting the cellulose nanofiber aggregates may be oriented to any direction and the aggregates may form bright spots in polarizing microscopic observation under a cross-Nicol configuration. An average particle diameter of the cellulose nanofiber aggregates may be roughly 1 to 20 μm.

Description

  The present invention relates to an optical film used in combination with a display device in a display unit of electrical / electronic or precision equipment, and a method for manufacturing the same.

  In recent years, liquid crystal displays (LCDs) have made remarkable progress as display devices in television (TV) applications or moving image display applications, and are rapidly spreading. For example, the development of high-speed liquid crystal materials and the improvement of driving methods such as overdrive have overcome the conventional video display that LCDs were not good at, and production technology innovations that responded to larger displays Yes.

  In these displays, in applications such as televisions and monitors that place importance on image quality, and video cameras that are used outdoors with strong external light, the surface is usually treated to prevent reflection of external light. It is. One of the techniques is anti-glare treatment, and for example, the surface of a liquid crystal display is usually subjected to anti-glare treatment. The anti-glare treatment is a treatment that creates a fine uneven structure on the surface, thereby scattering the reflected light on the surface and blurring the reflected image. Usually, an anti-glare treatment is applied to an LCD. A dazzling film is provided.

  JP 2009-265143 A As an anti-glare film which can display an excellent transmission image and has an excellent anti-glare property in a plasma display panel (PDP) which has been spreading in recent years along with LCD. The gazette (Patent Document 1) discloses an antiglare film comprising a transparent film and a hard coat layer formed on the transparent film, wherein (a) the primary particle size is 40 to 40 in the hard coat layer. 200 nm silica fine particles, (b) a silica fine particle having a primary particle size of 1 to 30 nm and a binder, and a silica fine particle aggregated structure, the center line average roughness Ra of the hard coat layer side surface of the antiglare film Is disclosed as an antiglare film having a roughness period λa of 40 to 200 μm and a haze value of the antiglare film of 0.1 to 3.0%. That. This document describes a method of using an aggregating agent such as alkyl acetoacetate aluminum diisopropylate as a method for forming an aggregated structure of silica fine particles. In the examples, a hard coat layer having a haze of 1.92 to 2.02% and an uneven period of 46 to 80 μm is formed.

  JP 2007-219485 A (Patent Document 2) has at least one hard coat layer containing a translucent resin and cohesive metal oxide particles on a transparent support, and has a surface haze value. Has an optical haze value of 0 to 12%, an internal haze value of 0 to 35%, and an Sm value of 50 to 200 μm.

  However, even in these optical films, since convex portions are formed by aggregation of inorganic fine particles, it is difficult to control the shape of the convex portions, the antiglare property is not sufficient, and external light is easily reflected. Further, in Patent Document 1, a plurality of particles having different particle diameters are required, and a large amount of silica fine particles are aggregated. Therefore, an aggregating agent is necessary, which causes bleeding out.

  On the other hand, in Japanese Patent No. 4213898 (Patent Document 3), a metal film is formed on the one surface of a long polymer film in which a hard coat layer and an antireflection layer are sequentially provided on one surface of a transparent support. In the method for producing an antiglare film, which is subjected to an uneven forming process continuously by an embossing roller having an embossed plate to make an antiglare film, the embossed plate is produced by electric discharge machining so as to form an irregular uneven pattern. The arithmetic average roughness Ra of the surface of the embossed plate is set to 0.3 to 1.0 μm, the average unevenness period RSm is set to 5 to 30 μm, and the peripheral surface is in contact with the transparent support to cool the polymer film. The polymer film is conveyed while being sandwiched by a backup roller and the embossing roller that heats the polymer film with a peripheral surface in contact with the antireflection layer. The polymer film is wound around the embossing roller upstream of the sandwiching position where the polymer film is sandwiched, and the polymer film is wound around the backup roller downstream of the sandwiching position. A method for producing a dazzling film is disclosed.

  However, in this antiglare film, since the uneven period is small, the antiglare property decreases when the haze is low, and it is difficult to improve the visibility in an environment where strong light is reflected. Furthermore, it is difficult to prepare an embossed plate, and the manufacturing process is complicated, and the productivity is low.

JP 2009-265143 A (Claims, Examples) JP 2007-219485 A (Claims, Examples) Japanese Patent No. 4213898 (Claim 1)

  Accordingly, an object of the present invention is to provide an optical film having high productivity and excellent antiglare property and a method for producing the same.

  Another object of the present invention is to provide an optical film that can suppress reflection of external light and has excellent visibility, and a method for manufacturing the same.

  Still another object of the present invention is to provide an optical film excellent in scratch resistance and mechanical properties and a method for producing the same.

  Another object of the present invention is to provide an optical film in which bleeding out such as a flocculant is suppressed and a method for producing the same.

  Another object of the present invention is to provide a method for easily producing an optical film having low reflection and low haze.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors have formed a cured product of a curable composition containing a curable resin precursor and cellulose nanofibers on a transparent film, and the cellulose is formed on a convex portion. It was found that by forming a hard coat layer having a concavo-convex structure containing nanofiber aggregates on the surface, an optical film excellent in antiglare property (particularly an antiglare film) can be produced with high productivity, and the present invention was completed. .

  That is, the optical film of the present invention is an optical film including a transparent film and a hard coat layer formed on the transparent film and having an uneven structure on the surface, wherein the hard coat layer is a curable resin. It is formed of a cured product of a curable composition containing a precursor and cellulose nanofibers, and the convex portions on the surface of the hard coat layer contain cellulose nanofiber aggregates. The cellulose nanofibers constituting the cellulose nanofiber aggregate may be oriented in random directions, and the aggregate may form a bright spot portion by observation with a polarizing microscope using crossed Nicols. The cellulose nanofiber aggregate may be rod-shaped, and the average major axis of the cellulose nanofiber aggregate may be 15 μm or less. The cellulose nanofibers may be unevenly distributed in the convex portion. A concavo-convex structure having an average unevenness interval Sm of 80 μm or more and less than 600 μm, an arithmetic average roughness Ra of 0.05 to 1.5 μm, and an arithmetic average inclination Δa of 0.05 to 5 ° may be formed on the surface of the hard coat layer. The cellulose nanofibers may have an average fiber diameter of 10 to 500 nm. The ratio of the cellulose nanofiber may be about 0.01 to 3 parts by weight with respect to 100 parts by weight of the curable resin precursor. The curable composition may further contain a polymer (particularly a cellulose derivative) having no ethylenically unsaturated bond. The curable composition may further contain hollow silica particles. The hollow silica particles may be unevenly distributed around the cellulose nanofiber aggregate. The hard coat layer may contain substantially no flocculant.

  The present invention also includes a method for producing the optical film, in which a coating liquid for forming a hard coat layer is applied on a transparent film, dried, and then irradiated with active energy rays to be cured.

  In the present invention, the hard coat layer formed on the transparent film is formed of a cured product of a curable composition containing a curable resin precursor and cellulose nanofibers, and includes the cellulose nanofiber aggregates on the convex portions. Since the concavo-convex structure is provided on the surface, an optical film excellent in antiglare property can be obtained with high productivity. In particular, this optical film can suppress the reflection of external light and is excellent in visibility. For example, display of a display excellent in visibility can be obtained even in an environment where strong light is reflected. Moreover, since the hard coat layer is formed of a cured product of a curable composition containing a curable resin precursor and cellulose nanofibers, scratch resistance and mechanical properties can be improved. Moreover, since the uneven structure which expresses the outstanding optical characteristic can be formed without mix | blending an aggregating agent, the optical film with which bleeding out, such as an aggregating agent was suppressed, is obtained. Furthermore, when the curable composition contains cellulose nanofibers and hollow silica, an optical film having low reflection and low haze can be easily obtained.

FIG. 1 is a polarized micrograph of the cellulose nanofiber dispersion A obtained in the example using crossed Nicols. FIG. 2 is a polarized micrograph of the cellulose nanofiber dispersion B obtained in the example using crossed Nicols. FIG. 3 is a polarized micrograph of the cellulose nanofiber dispersion H obtained in the example using crossed Nicols. FIG. 4 is a polarized micrograph of the hard coat layer surface obtained in Example 7 by open Nicol. FIG. 5 is a polarized micrograph of the hard coat layer surface obtained in Example 7 by crossed Nicols. FIG. 6 is a polarized micrograph of the hard coat layer surface obtained in Comparative Example 2 by open Nicol. FIG. 7 is a polarized micrograph of the hard coat layer surface obtained in Comparative Example 2 by crossed Nicols. FIG. 8 is a polarized micrograph of the hard coat layer surface obtained in Comparative Example 3 by open Nicol. FIG. 9 is a polarized micrograph of the hard coat layer surface obtained in Comparative Example 3 by crossed Nicols.

[Hard coat layer]
The optical film of the present invention includes a hard coat layer formed on a transparent film. This hard coat layer is formed of a cured product of a curable composition containing a curable resin precursor and cellulose nanofibers, and has a concavo-convex structure on the surface.

(Surface structure of hard coat layer)
In the concavo-convex structure on the surface of the hard coat layer, each convex portion formed on the surface contains a cellulose nanofiber aggregate. The cellulose nanofiber aggregates only need to be included in the region constituting the convex portion, and may exist (distributed) over the entire convex portion, or exist as a plurality of aggregates in one convex portion. May be. Moreover, the said aggregate may exist as one aggregate in the approximate center part vicinity of a convex part. In the present invention, as will be described later, the cellulose nanofiber and the resin component before curing are combined together by a convection action in the production process to aggregate on the surface of the hard coat layer to form a convex portion, thereby simplifying the production. By this method, a concavo-convex structure excellent in optical characteristics (particularly a concavo-convex structure having steep and fine convex portions) can be formed on the surface of the hard coat layer. Moreover, since the aggregate is composed of nanofibers, it does not affect visible light and does not impair the optical properties.

  The shape of the cellulose nanofiber aggregate contained in each convex portion is not particularly limited, and may be any of isotropic shapes (such as substantially spherical shapes) and anisotropic shapes (bar shapes, fibrous shapes, irregular shapes, etc.) Usually, it has an anisotropic shape such as a substantially rod shape. The average particle diameter of the aggregate is, for example, about 1 to 10 μm, preferably 1.5 to 9 μm, more preferably about 2 to 8 μm (particularly 2.5 to 7 μm).

  When the aggregate is anisotropic (particularly rod-shaped), the average major axis of the aggregate may be 15 μm or less, for example, 3 to 15 μm, preferably 5 to 12 μm, and more preferably about 6 to 10 μm. The average aspect ratio (average major axis / average minor axis) of the anisotropic aggregate is, for example, about 1.5 to 20, preferably about 2 to 15, and more preferably about 3 to 10. In the present invention, a moderately fine and steep concavo-convex structure can be formed by generating such an anisotropic aggregate.

  When the particle size of the aggregate is too small, the uneven structure tends to be too small, and when it is too large, the uneven structure tends to be too large.

  The average particle diameter of the aggregate can be obtained as an average value of any 10 or more aggregates based on a polarizing microscope. In detail, it can measure by the method as described in an Example.

  The cellulose nanofibers constituting the cellulose nanofiber aggregate may be oriented in an arbitrary direction, but are usually oriented in a random direction. Regarding the orientation direction of the cellulose nanofibers, when the orientation direction of the cellulose nanofibers is oriented in a random direction, the aggregate forms a bright spot portion by observation with a polarizing microscope using crossed Nicols, so that the orientation direction can be easily set. I can confirm. Therefore, the presence or absence of aggregates at the convex portions can be easily confirmed by combining with observation with a polarizing microscope using open Nicols.

  The cellulose nanofibers may be unevenly distributed on the convex portions on the surface of the hard coat layer. For example, the ratio of cellulose nanofibers (cellulose nanofiber aggregates) existing in the convex portions to the whole cellulose nanofibers is It may be 30% by weight or more, for example, 30 to 90% by weight, preferably 40 to 85% by weight, more preferably about 50 to 80% by weight (particularly 60 to 70% by weight). If the proportion of cellulose nanofibers present in the convex portions is small, it becomes difficult to form a sufficient concave-convex structure (particularly, a concave-convex structure having steep and fine convex portions).

  In addition, when cellulose nanofiber exists also in area | regions other than a convex part, the cellulose nanofiber which exists in areas other than a convex part may be any of an aggregate and a non-aggregate (for example, uniform dispersion). Usually, it is non-aggregated.

  The concavo-convex structure on the surface can be selected from a range where the average interval Sm of the concavo-convex is 80 μm or more and less than 600 μm depending on the application. In the antiglare film, Sm is, for example, about 85 to 500 μm, preferably 90 to 400 μm, and more preferably about 95 to 300 μm (particularly 100 to 300 μm). Further, in a low reflection antiglare film in which inorganic particles having a low refractive index are blended in a hard coat layer, Sm is, for example, about 100 to 550 μm, preferably 150 to 500 μm, more preferably about 200 to 450 μm (especially 250 to 420 μm). It is. When Sm is too small, the antiglare property is lowered and reflection is likely to occur, and when Sm is too large, glare is likely to occur.

  The arithmetic average roughness Ra of the concavo-convex structure can be selected from a range of about 0.05 to 1.5 μm depending on the application. In the antiglare film, Ra may be 0.1 to 1.5 μm, for example, 0.12 to 1 μm, preferably 0.13 to 0.5 μm, more preferably 0.15 to 0.3 μm (particularly 0). .15 to 0.25 μm). Further, in the low reflection antiglare film, Ra may be 0.05 to 0.3 μm, for example, 0.06 to 0.25 μm, preferably 0.07 to 0.2 μm, and more preferably 0.08. It is about -0.15 micrometer (especially 0.09-0.12 micrometer). If Ra is too small, the antiglare property is lowered and reflection is likely to occur. If Ra is too large, the sharpness of the image is lowered and the production becomes difficult.

  The arithmetic average slope Δa of the concavo-convex structure can be selected from a range of about 0.05 to 5 ° depending on the application. In the antiglare film, Δa is, for example, about 0.1 to 5 °, preferably about 0.3 to 4.5 °, more preferably about 0.5 to 4 ° (particularly 1 to 3.5 °). In a low reflection antiglare film, Δa is, for example, about 0.05 to 5 °, preferably 0.06 to 4 °, and more preferably about 0.07 to 3 ° (particularly 0.08 to 2 °). is there. In the present invention, since Δa is large and the concavo-convex structure is steep (or sharp), an excellent scattering effect can be exhibited and the antiglare property can be improved. When Δa is too small, the antiglare property is lowered. If Δa is too large, the sharpness of the image decreases.

  In the present invention, the concavo-convex structure (Sm, Ra and Δa) useful as an antiglare film can be formed on the hard coat layer surface by a simple method using a curable resin composition containing cellulose nanofibers.

  In the present invention, the average distance between tops Sm, the arithmetic average roughness Ra, and the arithmetic average slope Δa can be measured by a method based on JIS B0601.

(Curable composition)
The hard coat layer having the concavo-convex structure formed on the surface only needs to be formed of a transparent and hard material, and is hardened from the point that a hard coat layer excellent in optical characteristics and mechanical characteristics can be easily produced. It is formed with the hardened | cured material of the curable composition containing a curable resin precursor and a cellulose nanofiber. By forming the cured product of the curable composition, mechanical properties such as scratch resistance can be improved, and by containing cellulose nanofibers, the concavo-convex structure can be obtained by a simple method without impairing optical properties. Can be formed.

(A) Curable resin precursor The curable resin precursor is a compound having a functional group that reacts with heat or active energy rays (such as ultraviolet rays or electron beams) and is cured or crosslinked with heat or active energy rays. Thus, various curable compounds capable of forming a resin (particularly a cured or crosslinked resin) can be used. Examples of the resin precursor include a thermosetting compound or a resin [low molecular weight compound having an epoxy group, a polymerizable group, an isocyanate group, an alkoxysilyl group, a silanol group, etc. (for example, an epoxy resin, an unsaturated polyester, a polyurethane, Silicone resins, etc.)], photocurable compounds curable with actinic rays (such as ultraviolet rays) (photocurable monomers, ultraviolet curable compounds such as oligomers, etc.), and the like. ) A curable compound may be used. Note that a photocurable compound such as a photocurable monomer, an oligomer, or a photocurable resin that may have a low molecular weight may be simply referred to as a “photocurable resin”.

  Examples of the photocurable compound include monomers and oligomers (or resins, particularly low molecular weight resins). The monomer can be classified into, for example, a monofunctional monomer having one polymerizable group and a polyfunctional monomer having at least two polymerizable groups.

  Examples of the monofunctional monomer include (meth) acrylic monomers such as (meth) acrylic acid esters, vinyl monomers such as vinylpyrrolidone, isobornyl (meth) acrylate, and adamantyl (meth) acrylate. Examples include (meth) acrylate having a bridged cyclic hydrocarbon group.

  The polyfunctional monomer includes a polyfunctional monomer having about 2 to 8 polymerizable groups. Examples of the bifunctional monomer include ethylene glycol di (meth) acrylate and propylene glycol di (meta). ) Acrylate, butanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, alkylene glycol di (meth) acrylate such as hexanediol di (meth) acrylate; diethylene glycol di (meth) acrylate, dipropylene glycol di (meth) ) Acrylate, polyoxytetramethylene glycol di (meth) acrylate and other (poly) oxyalkylene glycol di (meth) acrylate; tricyclodecane dimethanol di (meth) acrylate, adamantane di (meth) acrylate, etc. And di (meth) acrylate having a hydrocarbon group.

  Examples of 3 to 8 functional monomers include glycerin tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolethane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) ) Acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and the like.

  Examples of oligomers or resins include (meth) acrylates of bisphenol A-alkylene oxide adducts, epoxy (meth) acrylates (bisphenol A type epoxy (meth) acrylates, novolac type epoxy (meth) acrylates, etc.), polyester (meth) acrylates ( For example, aliphatic polyester type (meth) acrylate, aromatic polyester type (meth) acrylate, etc.), (poly) urethane (meth) acrylate (polyester type urethane (meth) acrylate, polyether type urethane (meth) acrylate, etc.), Examples thereof include silicone (meth) acrylate. These (meth) acrylate oligomers or resins may contain copolymerizable monomers such as styrene monomers, vinyl ester monomers, maleic anhydride, maleic acid, and fumaric acid. These photocurable compounds can be used alone or in combination of two or more.

  Preferred curable resin precursors are photocurable compounds that can be cured in a short time, for example, ultraviolet curable compounds (monomers, oligomers, resins that may be low molecular weight, etc.), and EB curable compounds. In particular, a practically advantageous resin precursor is an ultraviolet curable resin. Furthermore, in order to improve the scratch resistance, the photocurable resin is a bifunctional or higher (preferably about 2 to 10 functional, more preferably about 3 to 8 functional) photocurable compound, particularly a polyfunctional (meth) acrylate. For example, it is preferable to contain (meth) acrylate (for example, dipentaerythritol hexa (meth) acrylate etc.) of 3 or more functions (especially 4-8 functions). In particular, 5 to 7 functional (meth) acrylates and 2 to 4 functional (meth) acrylates [particularly 3 to 4 functional (meth) acrylates such as pentaerythritol tri (meth) acrylate] may be combined. The ratio (weight ratio) is, for example, the former / the latter = 100/0 to 1/99, preferably 90/10 to 10/90, more preferably about 80/20 to 20/80. From the viewpoint of excellent properties, for example, the former / the latter = 90/10 to 50/50 (especially 80/20 to 60/40) is particularly preferable.

(B) Cellulose nanofiber The cellulose nanofiber is not particularly limited as long as it is formed of a polysaccharide having a β-1,4-glucan structure, for example, a cellulose fiber derived from a higher plant [for example, wood fiber ( Wood pulp such as conifers, hardwoods, etc., bamboo fibers, sugarcane fibers, seed hair fibers (cotton linters, Bombax cotton, kapok etc.), gin leather fibers (eg hemp, mulberry, mitsumata etc.), leaf fibers (eg, Natural cellulose fibers (pulp fibers) such as Manila hemp and New Zealand hemp), animal-derived cellulose fibers (such as squirt cellulose), and bacteria-derived cellulose fibers. These cellulose nanofibers may be used alone or in combination of two or more.

  Among these cellulose nanofibers, plant-derived cellulose fibers such as wood fibers (wood pulp such as conifers and hardwoods) and seed hair fibers (from the point of high productivity and appropriate fiber diameter and fiber length) Cellulose fibers derived from pulp such as cotton linter pulp) are preferred, and cellulose fibers derived from hardwood pulp are particularly preferred from the viewpoint of easy preparation of short fiber length fibers.

  Although the average fiber diameter of a cellulose nanofiber will not be specifically limited if it is nanometer size, For example, it is 10-300 nm, Preferably it is 30-280 nm, More preferably, it is a 50-250 nm (especially 100-230 nm) grade. The average fiber length is, for example, about 0.1 to 10 μm, preferably about 0.5 to 9 μm, and more preferably about 1 to 8 μm.

  In addition, in this invention, the said average fiber diameter and fiber length are the values computed from the fiber diameter (n = about 20) measured based on the polarization micrograph. Cellulose nanofibers having the above fiber diameter and fiber length are aggregated into rods having the shape and size described above, improving the dispersibility of cellulose nanofibers in the initial stage of the hard coat layer coating solution, and promoting the generation of convection For this reason, a fine concavo-convex structure (particularly a concavo-convex structure having steep and fine convex portions) can be formed on the surface of the hard coat layer. In particular, cellulose microfibrils are skeletal materials that occupy 50% or more of plant cell walls (plant fibers) and are high-strength and high-elasticity nanofibers made of extended chain crystals. Conventionally, cellulose nanofibers have long fiber lengths. However, in the present invention, a fine and steep convex portion was successfully formed on the surface of the hard coat layer by adjusting the fiber length to a relatively short fiber. did. If the average fiber length is too large, it becomes difficult to form a steep concavo-convex structure, and the cellulose nanofibers aggregate before coating to cause poor appearance.

  The cross-sectional shape (cross-sectional shape perpendicular to the longitudinal direction of the fiber) of the cellulose nanofiber is not particularly limited, but may be an anisotropic shape (flat shape) such as bacterial cellulose. In some cases, the shape is generally isotropic. Examples of the substantially isotropic shape include a perfect circle shape and a regular polygon shape. In the case of a substantially circular shape, the ratio of the major axis to the minor axis (average aspect ratio) is, for example, 1-2, preferably 1-1. 0.5, more preferably about 1 to 1.3 (particularly 1 to 1.2).

  Such cellulose nanofibers may be prepared by pulverizing long-fiber cellulose nanofibers to make short fibers. The pulverization may be a method of pulverizing solid cellulose nanofibers, or a method of pulverizing cellulose nanofibers in a dispersion (or suspension) containing cellulose nanofibers and a solvent. .

  Among these methods, a method of pulverizing in a dispersion is preferable because it can be easily pulverized to a uniform fiber length. As the solvent, for example, water or a hydrophilic organic solvent can be preferably used. Examples of the hydrophilic organic solvent include alcohols (ethanol, isopropanol, butanol, etc.), ketones (acetone, methyl ethyl ketone, etc.), cellosolves (methyl cellosolve, ethyl cellosolve, propylene glycol monomethyl ether (1-methoxy-2-propanol). ) Etc.). These solvents can be used alone or in combination of two or more. Among these solvents, it is preferable to contain at least water from the viewpoint of convenience. The dispersion may contain other additives, may be a dispersion containing a polymer (particularly a cellulose derivative) having no ethylenically unsaturated bond, which will be described later, and may be an acidic aqueous dispersion. There may be.

  The solid content concentration in the dispersion is, for example, about 0.01 to 50% by weight, preferably about 0.1 to 30% by weight, and more preferably about 0.2 to 10% by weight. The concentration of cellulose nanofibers in the dispersion is, for example, 0.01 to 10% by weight, preferably 0.05 to 5% by weight, more preferably 0.1 to 3% by weight (particularly 0.2 to 1% by weight). Degree.

  The pulverization method is not particularly limited as long as it is a pulverizer capable of unit operation for pulverizing a solid substance into small pieces. For example, a ball mill, a bead mill, a rod mill, a self-pulverization mill, a semi-autogenous pulverization ( SAG) mill, pebbles mill, high pressure grinding roll, vertical axis impactor (VSI) mill, and the like. In this invention, when it processes for a long time with a grinder with a high grinding effect, high anti-glare property cannot be expressed. That is, in order to form a fine and sharp surface concavo-convex structure, it is necessary to shorten the fiber length. However, if the fiber length is too short, a sharp concavo-convex structure cannot be formed and antiglare properties cannot be exhibited. Therefore, it is necessary to adjust so that the cellulose nanofiber which has the said fiber length and a fiber diameter can be obtained in a grinding | pulverization process.

  As a preferable pulverization method, a pulverization method that is not an excessively dispersed pulverization method and that breaks the lengthwise connection of cellulose microfibrils is used rather than a pulverization method that tears cellulose microfibrils in the length direction. preferable. That is, what is important in the pulverization process is to select a pulverization method that can cut the fiber length short. For example, a bead mill may be used to grind at a peripheral speed of about 10 to 20 m / sec (particularly 12 to 18 m / sec) with beads having a diameter of 1 mmφ.

  The ratio of the cellulose nanofibers can be selected, for example, from a range of about 0.01 to 3 parts by weight with respect to 100 parts by weight of the curable resin precursor, but can form a fine concavo-convex structure without reducing optical properties From the point of view, for example, it is about 0.02 to 2 parts by weight, preferably about 0.03 to 1 part by weight, and more preferably about 0.05 to 0.3 parts by weight. If the proportion of cellulose nanofiber is too small, it will be difficult to form an uneven structure. When there are too many ratios of a cellulose nanofiber, the optical characteristic of an optical film will fall.

(C) Polymer having no ethylenically unsaturated bond The curable composition further comprises an ethylenically unsaturated bond involved in the curing reaction of the curable resin precursor in order to improve mechanical properties such as flexibility. The polymer which does not have may be included.

  Examples of such polymers include olefin resins, styrene resins, (meth) acrylic resins, organic acid vinyl ester resins, vinyl ether resins, halogen-containing resins, polycarbonates, polyesters, polyamides, thermoplastic polyurethanes, Examples include polysulfone resins, polyphenylene ether resins, cellulose derivatives, silicone resins, rubbers, and elastomers. These polymers can be used alone or in combination of two or more.

  Of these polymers, styrene resins, (meth) acrylic resins, alicyclic olefin resins, polyesters, cellulose derivatives, etc. are widely used. Cellulose derivatives are preferred from the viewpoint that the mechanical properties can be improved.

  Cellulose derivatives include cellulose esters, cellulose ethers, and cellulose carbamates. These cellulose derivatives can be used alone or in combination of two or more. Of these cellulose derivatives, cellulose esters are preferred.

Examples of the cellulose esters include aliphatic organic acid esters (cellulose acetate such as cellulose diacetate and cellulose triacetate; C _2-6 such as cellulose propionate, cellulose butyrate, cellulose acetate propionate, and cellulose acetate butyrate). And the like.

These cellulose esters can be used alone or in combination of two or more. Among these cellulose esters, the solubility in a solvent is high, the preparation of the coating liquid is easy, the viscosity of the coating liquid can be easily adjusted by adding a small amount, and the cellulose in the coating liquid Cellulose acetate C _3-4 acylates such as cellulose acetate propionate and cellulose acetate butyrate are preferred in order to suppress nanofiber aggregation and enhance storage stability.

  The ratio of the polymer is, for example, 0.01 to 30 parts by weight, preferably 0.05 to 20 parts by weight (for example, 0.1 to 5 parts by weight) with respect to 100 parts by weight of the curable resin precursor. More preferably, it is about 0.2 to 3 parts by weight (particularly 0.3 to 1 part by weight). The ratio of the polymer is, for example, about 100 to 2000 parts by weight, preferably about 500 to 1800 parts by weight, and more preferably about 1000 to 1500 parts by weight with respect to 100 parts by weight of the nanofibers. In the present invention, the balance between the hard coat property and the mechanical properties can be adjusted by adjusting the ratio of the polymer. When the ratio is within this range, the balance between the two is excellent.

(D) Inorganic particles The curable composition may further contain inorganic particles from the viewpoint of improving optical properties such as transparency.

  The average particle diameter of the inorganic particles is 100 nm or less, preferably 80 nm or less (for example, 10 to 80 nm), more preferably about 20 to 70 nm. If the average particle size of the inorganic particles is too small, the effect of reducing haze and reflectance is reduced. If the average particle size of the inorganic particles is too large, the surface uneven structure is affected and the optical properties are deteriorated.

  The inorganic particles preferably have a low refractive index, and the refractive index is, for example, about 1.2 to 1.5, preferably about 1.21 to 1.4, and more preferably about 1.22 to 1.35. May be. When the refractive index is too large, the sharpness of the image is deteriorated.

  Examples of the inorganic particles include simple metals, metal oxides, metal sulfates, metal silicates, metal phosphates, metal carbonates, metal hydroxides, silicon compounds, fluorine compounds, and natural minerals. The inorganic particles may be surface-treated with a coupling agent (titanium coupling agent, silane coupling agent). These inorganic particles can be used alone or in combination of two or more. Of these inorganic particles, metal oxide particles such as titanium oxide, silicon compound particles such as silicon oxide, and fluorine compound particles such as magnesium fluoride are preferable from the viewpoint of transparency and the like, and low reflection and low haze are preferable. Silica particles are particularly preferable in that

  Further, the silica particles may be silica particles having hollow portions inside (hollow silica particles). Since the hollow silica particles have a low refractive index, low reflection and low haze can be improved efficiently.

  The shape and size of the cavity in the hollow silica particles are not particularly limited, and the refractive index of the particles may be in the above range. The hollow silica particles may usually have a single hollow portion (in the case of a spherical particle, a spherical hollow portion) as a core with respect to the outer shell (shell) of the particle. May have a hollow portion (such as a spherical shape or an ellipsoidal shape). Such hollow silica particles are described in JP-A Nos. 2001-233611 and 2003-192994. The hollow silica particles described in these documents have a low refractive index, are particles in a colloidal region, and are excellent in dispersibility. In the present invention, the hollow silica particles described in these documents can be preferably used. Hollow silica particles can be produced by the production methods described in these documents.

  The inorganic particles may be unevenly distributed near the surface of the hard coat layer (particularly, around the cellulose nanofiber aggregate unevenly distributed in the convex portion). When the inorganic particles are unevenly distributed near the surface of the hard coat layer, the reflectance of the optical film can be lowered. In order to make the inorganic particles unevenly distributed near the surface of the hard coat layer, for example, the composition of the dispersion may be adjusted as appropriate.

  The inorganic particles may be in the form of a dispersion dispersed in a solvent in the curable composition. Examples of the solvent include water, alcohols (such as ethanol and isopropanol), and ketones (such as acetone and methyl ethyl ketone). The solid content concentration of the inorganic particles in the dispersion is, for example, about 0.1 to 50% by weight, preferably about 1 to 40% by weight, and more preferably about 5 to 30% by weight.

  The ratio of the inorganic particles (for example, hollow silica particles) is, for example, 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight, and more preferably 0.1 to 100 parts by weight of the curable resin precursor. It is about 5 to 3 parts by weight (particularly 1 to 2 parts by weight). If the proportion of the inorganic particles is too small, the effect of improving the optical properties is small. When there are too many ratios of an inorganic particle, a mechanical characteristic will fall and haze will increase.

(E) Other additive The curable composition may contain the hardening | curing agent according to the kind of curable resin precursor. For example, the thermosetting resin may contain a curing agent such as amines and polyvalent carboxylic acids.

  The curable composition may contain a polymerization initiator. The polymerization initiator may be a thermal polymerization initiator (thermal radical generator such as a peroxide such as benzoyl peroxide) or a photopolymerization initiator (photo radical generator). A preferred polymerization initiator is a photopolymerization initiator. Examples of the photopolymerization initiator include acetophenones or propiophenones, benzyls, benzoins, benzophenones, thioxanthones, and acylphosphine oxides. The photopolymerization initiator may contain a conventional photosensitizer and a photopolymerization accelerator (for example, tertiary amines such as dialkylaminobenzoate, phosphine photopolymerization accelerator, etc.). . The ratio of the photopolymerization initiator is 0.1 to 20 parts by weight, preferably 0.5 to 10 parts by weight, more preferably 1 to 8 parts by weight (particularly 1 to 5 parts by weight) with respect to 100 parts by weight of the curable resin precursor. Part by weight), and may be about 3 to 8 parts by weight.

  The solvent can be selected according to the type and solubility of the curable resin precursor and the polymer, and at least solids (the curable resin precursor, the polymer, the reaction initiator, and other additives) are uniformly dissolved. Any solvent can be used. Examples of such solvents include ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc.), ethers (dioxane, tetrahydrofuran, etc.), aliphatic hydrocarbons (hexane, etc.), alicyclic hydrocarbons ( Cyclohexane etc.), aromatic hydrocarbons (toluene, xylene etc.), halogenated carbons (dichloromethane, dichloroethane etc.), esters (methyl acetate, ethyl acetate, butyl acetate etc.), water, alcohols (ethanol, isopropanol, Butanol, cyclohexanol, etc.), cellosolves (methyl cellosolve, ethyl cellosolve, propylene glycol monomethyl ether (1-methoxy-2-propanol), etc.), cellosolve acetates, sulfoxides (dimethylsulfate) Kishido etc.), amides (dimethylformamide, dimethylacetamide, etc.), and others. These solvents can be used alone or in combination of two or more, and may be a mixed solvent.

  Among these solvents, ketones such as methyl ethyl ketone, alcohols such as butanol, and cellosolves such as propylene glycol monomethyl ether are preferable, and these may be mixed. For example, the ketones and the alcohols and / or the cellosolves are the former / the latter = 90/10 to 10/90, preferably 80/20 to 30/70, more preferably 70/30 to 50 /. You may mix by the ratio (weight ratio) of about 50.

  The ratio of the solvent can be selected from the range of about 10 to 1000 parts by weight with respect to 100 parts by weight of the curable resin precursor, for example, 50 to 500 parts by weight, preferably 80 to 400 parts by weight, and more preferably 100 to 300 parts by weight. About parts by weight.

  In the curable composition, conventional additives such as organic particles, stabilizers (antioxidants, ultraviolet absorbers, etc.), surfactants, water-soluble polymers are used as long as the optical properties of the hard coat layer are not impaired. , Fillers, crosslinking agents, coupling agents, colorants, flame retardants, lubricants, waxes, preservatives, viscosity modifiers, thickeners, leveling agents, antifoaming agents, and the like.

  In particular, the curable composition can form a concavo-convex structure without using a flocculant, and is substantially a flocculant (for example, a fine particle flocculant described in JP-A-2009-265143) from the viewpoint of optical characteristics and the like. Etc.) are preferred.

  The curable composition (curable resin precursor) may be a thermosetting composition or a photocurable compound that can be cured in a short time, for example, an ultraviolet curable compound or an EB curable compound. Good. In particular, a resin precursor that is practically advantageous and easily forms an uneven structure is an ultraviolet curable resin.

  The thickness of the hard coat layer is, for example, about 0.5 to 30 μm, preferably 1 to 25 μm, more preferably about 3 to 20 μm (particularly 5 to 15 μm).

[Transparent film]
As the transparent film (or substrate film), a transparent polymer film, for example, a cellulose derivative [cellulose triacetate (TAC), cellulose acetate such as cellulose diacetate, etc.], polyester [polyethylene terephthalate (PET), polybutylene terephthalate (PBT) ), Polyarylate resins, etc.], polysulfone resins [polysulfone, polyethersulfone, etc.], polyether ketone resins [polyether ketone, polyether ether ketone, etc.], polycarbonate (bisphenol A type polycarbonate, etc.), polyolefin (polyethylene) , Polypropylene, etc.), cyclic polyolefin [TOPAS (registered trademark), ARTON (registered trademark), ZEONEX (ZEO) EX) (registered trademark)], halogen-containing resin (polyvinylidene chloride, etc.), (meth) acrylic resin, styrene resin (polystyrene, etc.), vinyl acetate or vinyl alcohol resin (polyvinyl alcohol, etc.), etc. Film. The transparent film may be uniaxially or biaxially stretched.

For optically isotropic transparent films, cellulose esters (cellulose acetate such as cellulose diacetate and cellulose triacetate, cellulose acetate propionate, cellulose acetate C _3-4 acylate such as cellulose acetate butyrate, etc.), etc. A formed sheet or film is preferred. In particular, when a cellulose derivative is used as the thermoplastic resin of the hard coat layer, the adhesion between the two can be improved by using a film composed of the cellulose derivative as the transparent film.

  The thickness of the transparent film can be selected from a range of, for example, about 15 to 200 μm, preferably 20 to 150 μm, and more preferably about 30 to 100 μm.

[Optical film]
By having the hard coat layer, the optical film of the present invention has a high antiglare property, but has a high transparency because haze is suppressed.

  The optical film of the present invention has a haze based on JIS K7136 of, for example, 0.1 to 30%, preferably 0.2 to 25%, more preferably 0.3 to 20% (particularly 0.5 to 10%). The haze can be further reduced by blending low refractive index inorganic particles, for example, 0.1 to 3%, preferably 0.2 to 2%, more preferably 0.3 to 1. It may be about 5% (particularly 0.5 to 1.3%). By containing hollow silica in the hard coat layer and unevenly distributed near the surface, haze can be efficiently reduced. If the haze is too low, it is difficult to form a concavo-convex structure. If the haze is too high, the image becomes whitish and a clear image cannot be displayed.

  In the optical film of the present invention, the total light transmittance based on JIS K7136 is, for example, about 70 to 100%, preferably 80 to 100%, more preferably 85 to 99% (particularly 90 to 95%). .

  The optical film of the present invention may have a surface reflectance of 10% or less, for example, 1 to 10%, preferably 2 to 8%, more preferably about 3 to 5%. In particular, the surface reflectance may be lowered by blending low refractive index inorganic particles in the hard coat layer, etc., and the surface reflectance is 4% or less, preferably 1 to 4%, more preferably 1 to 3. % Or less. By making the hard coat layer contain hollow silica and unevenly distributed in the vicinity of the surface, the surface reflectance can be efficiently reduced.

  In the optical film of the present invention (particularly, an optical film used as an antiglare film), a low refractive index layer may be further formed on the hard coat layer in order to reduce the surface reflectance. By laminating a low refractive index layer on the hard coat layer, in a display device such as a liquid crystal display device, when the low refractive index layer is arranged to be the outermost surface, light from the outside (external Light source etc.) can be effectively prevented from reflecting on the surface of the optical film.

  The optical film of the present invention has hard coat properties and high antiglare properties. Furthermore, the clarity of the transmitted image is excellent, and there is little character blur on the display surface. Therefore, the optical film of the present invention can be used for various display devices such as a liquid crystal display (LCD) device, a plasma display, and a display device with a touch panel. For example, it can be used as an antiglare film provided in an LCD device or an electrode substrate for a touch panel, and other optical elements (for example, various optical elements disposed in an optical path such as a polarizing plate, a retardation plate, a light guide plate). And may be combined.

[Method for producing optical film]
The method for producing the optical film of the present invention is not particularly limited as long as the concavo-convex structure can be formed on the surface of the hard coat layer, and a conventional method can be used. When the hard coat layer is formed of a cured product of the curable composition, the optical film of the present invention is coated with a coating solution containing the curable composition on the transparent film, dried, and then activated energy rays. Can be obtained by curing with irradiation.

  The coating liquid is usually a mixed liquid (especially a liquid such as a uniform solution) containing the curable resin precursor, cellulose nanofibers, a solvent, and, if necessary, a polymer or inorganic particles having no ethylenically unsaturated bond. Composition). In a preferred embodiment, the mixed solution contains a photocurable compound, cellulose nanofibers, a cellulose derivative, hollow silica, a photopolymerization initiator, and a solvent capable of dissolving the photocurable compound and the cellulose derivative. A composition is used.

  The concentration of the solute (curable resin precursor, nanofiber, polymer, inorganic particles, reaction initiator, other additives) in the mixed solution can be selected within a range that does not impair the castability and coating properties. It is about 1 to 80% by weight, preferably 5 to 60% by weight, more preferably 15 to 50% by weight (particularly 20 to 45% by weight).

  As a coating method, for example, spray, roll coater, air knife coater, blade coater, rod coater, reverse coater, bar coater, comma coater, dip squeeze coater, die coater, gravure coater, micro gravure coater, silk Examples include screen coater method, dip method, spray method, spinner method and the like. Of these methods, the bar coater method and the gravure coater method are widely used.

  After the mixture is cast or applied, the solvent is evaporated. A drying temperature is 70 degrees C or less (for example, 20-65 degreeC), Preferably it is 30-65 degreeC, More preferably, it is a 40-60 degreeC (especially 45-60 degreeC) grade. If the drying temperature is too high, the drying time is shortened and the occurrence of convection is suppressed, so that it is difficult to develop the uneven structure.

  In the present invention, the reason why cellulose nanofibers having a specific fiber length and fiber diameter form a fine and steep concavo-convex structure can be estimated as follows.

  That is, in the process of heating the coating liquid and evaporating the solvent, various convections are generated in the coating liquid before being dried and solidified. These convections include Marangoni convection mainly caused by surface tension difference and Benard convection caused by temperature gradient. There is a high possibility that Marangoni convection is dominant in the coating liquid in the present invention. Once Marangoni convection is generated, the temperature and concentration become inhomogeneous due to the flow, so that quasi-stationary convection is generated depending on conditions. . Furthermore, the cellulose nanofibers flow together with the curable resin precursor before cross-linking in the convection process that occurs during drying to form a lump, and aggregates of cellulose nanofibers are formed in the resin precursor. The resin component rises with the curing of the curable composition as a core, and the coating liquid does not contain particles (such as multiple particles with different particle sizes) or flocculants, but the surface is fine. A steep convex part is formed. Therefore, a dense concavo-convex structure is formed on the surface of the coating film, and cellulose nanofibers are concentrated and deposited on these convex portions. In the present invention, it can be presumed that the mechanism by which Marangoni convection is generated in the coating solution is that the surface tension is reduced by adding cellulose nanofibers. That is, in the coating liquid (dispersion liquid) in the present invention, the entropy of the coating liquid is increased by the effect of cellulose nanofibers, and convection is induced. This inducing effect of convection increases as the fiber length of the cellulose nanofiber in the coating solution is shorter.

  These estimates are supported by the following experimental results conducted by the present inventors. That is, as a result of comparing the surface tension temperature dependence of cellulose nanofibers and water, the surface tension accompanying the rise decreases linearly as the temperature rises in an aqueous system in which unground (raw material cellulose nanofibers) is added and dispersed. However, while it showed the same behavior as normal water, cellulose nanofibers pulverized into short fibers were added and dispersed, and in the aqueous system, the dependence of surface tension on temperature rise was higher than that of water. For example, the surface tension at 50 ° C. in water (pure water) is 68 mN / m, whereas the liquid in which 1% by weight of unground cellulose nanofiber aggregates are dispersed has a surface tension at 50 ° C. of water. In the same manner as in Example 1, the pulverized cellulose nanofiber aggregate (average major axis 7 μm, average minor axis 3 μm) significantly reduced the surface tension at 50 ° C. to 60 mN / m.

  The hard coat layer on which such a concavo-convex structure is formed is finally cured by actinic rays (such as ultraviolet rays or electron beams) or heat to form a cured resin. Curing of the precursor may be combined with heating, light irradiation, etc., depending on the type of curable resin precursor. Among these, light irradiation is preferable because a specific uneven structure can be easily formed. The light irradiation can be selected according to the type of the photocuring component or the like, and usually ultraviolet rays, electron beams, etc. can be used.

As the light source, for example, in the case of ultraviolet rays, a Deep UV lamp, a low-pressure mercury lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a halogen lamp, a laser light source (light source such as a helium-cadmium laser or an excimer laser) may be used. it can. Irradiation light amount (irradiation energy) varies depending on the thickness of the coating film, for example, 10 to 10000 mJ / cm ^2, preferably 30~5000mJ / cm ^2, more preferably about 50~1000mJ / cm ^2.

  In the case of an electron beam, a method of irradiating an electron beam with a light source (exposure source) such as an electron beam irradiation apparatus can be used. The irradiation amount (dose) varies depending on the thickness of the coating film, but is, for example, about 1 to 200 kGy (gray), preferably 5 to 150 kGy, and more preferably 10 to 100 kGy (particularly 20 to 80 kGy). The acceleration voltage is, for example, about 10 to 1000 kV, preferably about 50 to 500 kV, and more preferably about 100 to 300 kV.

  Of these light sources, a general-purpose light source is usually an ultraviolet irradiation device. Note that light irradiation may be performed in an inert gas atmosphere if necessary. In particular, when photocuring is utilized, not only can the precursor be immediately fixed by curing the precursor, but also the precipitation of low molecular components such as oligomers from the inside of the transparent film due to heat can be suppressed. Furthermore, the hard coat layer can be given scratch resistance, and when used in a touch panel, even if the operation is repeated, damage to the surface structure can be suppressed, and durability can be improved.

  Even when a low refractive index layer is further formed on the hard coat layer, it is usually cured with actinic rays or heat after applying or casting the coating liquid in the same manner as the hard coat layer. Can be formed.

  In the present invention, the hard coat layer may be subjected to a surface treatment in order to improve the adhesion of other layers (for example, a low refractive index layer or a transparent conductive layer) to the hard coat layer. Examples of the surface treatment include conventional surface treatments such as corona discharge treatment, flame treatment, plasma treatment, ozone and ultraviolet irradiation treatment.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. The transparent conductive films obtained in Examples and Comparative Examples were evaluated by the following items.

[Abrasion resistance of hard coat layer]
As an index of scratch resistance, # 0000 steel wool was rubbed 10 times back and forth with a load of 9.5 N / cm ² and evaluated according to the following criteria based on the number of scratches.

：: 0 ○ ○: 1-3 △: 4-6 ×: 7 or more.

[Pencil hardness]
Based on JIS K5400, pencil hardness was measured with a load of 4.9N.

[Haze and total light transmittance (TPP)]
It measured based on JISK7136 using the haze meter (The Nippon Denshoku Co., Ltd. make, brand name "NDH-5000W").

[Anti-glare]
A black film is pasted on the transparent film side of the optical film, and a fluorescent lamp (10000 cd / m ² ) exposed from a fluorescent tube is projected on the film surface from a point 2 m away, and the degree of blurring of the reflected image is visually observed. The evaluation was based on the following criteria.

○: The outline of the fluorescent lamp is not known or is slightly understood. Δ: The fluorescent lamp is partially blurred but the outline is clearly visible. ×: The fluorescent lamp is hardly blurred and the outline is very clear.

[Evaluation of glare]
The determination of glare on the display surface was made by placing the obtained optical film on a 42 inch full HD liquid crystal television (pixel number 1080 × 1920) and visually evaluating it as a white display according to the following criteria. In addition, the surface layer side polarizing plate of the LCD monitor used was a clear type polarizing plate.

A: Glare is not felt. O: Glare is slightly felt. X: Glare is felt.

[Evaluation of transmission image]
The transmitted image was determined by attaching the obtained optical film on a 42-inch full HD liquid crystal television (number of pixels 1080 × 1920) using a double-sided tape (manufactured by Nitto Denko Corporation, CS9621). These images were displayed, and the transmission images were visually evaluated according to the following criteria. In addition, the surface layer side polarizing plate of the LCD monitor used was a clear type polarizing plate.

A: The transmitted image looks completely clear. O: The transmitted image looks clear, but is slightly inferior to a normal clear liquid crystal television. Δ: The transmitted image looks a little white. X: The transmitted image appears blurred and unclear.

[Aggregation state]
A black film was bonded to the transparent film side of the optical film, and the degree of aggregation of cellulose nanofibers on the film surface was observed with a polarizing microscope and visually, and evaluated according to the following criteria.

○: Aggregation can be confirmed with a polarizing microscope, but aggregation cannot be confirmed visually, and irregularities appear smooth. Δ: Aggregation can be confirmed with a polarizing microscope, and agglomeration can be confirmed slightly visually, and irregularities are not slightly smooth. : Aggregation can be confirmed with both a polarizing microscope and visual observation.

[Reflectance]
A black film was bonded to the transparent film side of the optical film, and the integrated reflectance (visibility conversion) was measured using an integrating sphere reflection intensity measuring device (U-3300, manufactured by Hitachi High-Technologies Corporation).

[Arithmetic average roughness Ra, average distance Sm between tops of convex portions, arithmetic average slope Δa]
According to JIS B0601, using a contact-type surface roughness meter (manufactured by Tokyo Seimitsu Co., Ltd., surfcom 570A), under the conditions of a scanning range of 3 mm and a scanning frequency of 10 times, the arithmetic average roughness Ra, between the tops of the convex portions The average interval Sm and the arithmetic average slope Δa were measured.

[Size of cellulose nanofiber aggregate]
Based on a polarizing microscope ("System Biological Microscope BX50" manufactured by Olympus Co., Ltd.), the major axis of the rod-like aggregates at the convex portions of the hard coat layer was measured, and the average value (n = 20) was obtained.

[Preparation of cellulose nanofiber dispersion]
(Dispersion A)
Cellulose nanofiber aqueous dispersion (manufactured by Daicel Corporation, average fiber diameter 200 nm, average fiber length of about 100 μm, 1 wt% aqueous dispersion) 25 parts by weight, cellulose acetate propionate (manufactured by Eastman, CAP) 0. 5 parts by weight is dissolved in a mixed solvent of 40 parts by weight of methyl ethyl ketone (MEK), 10 parts by weight of 1-methoxy-2-propanol (MMPG), 20 parts by weight of 1-butanol (BuOH) and 10 parts by weight of isopropyl alcohol (IPA). did. Such a cellulose nanofiber suspension was prepared and pulverized at a peripheral speed of 8 m / s using a bead mill (NM-G5M manufactured by Asada Tekko Co., Ltd.) containing zirconia beads having a diameter of 1 mmΦ. The pulverized cellulose nanofibers were aggregated in a rod shape having an average major axis of 10 μm and an average minor axis of 1 to 3 μm. The photograph observed with the polarization microscope by the crossed Nicol of the obtained cellulose nanofiber dispersion liquid A is shown in FIG.

(Dispersion B)
Cellulose nanofibers were pulverized in the same manner as in the preparation of Dispersion A, except that the peripheral speed of the bead mill was pulverized at 15 m / s. The pulverized cellulose nanofibers were aggregated in a rod shape having an average major axis of 6 μm and an average minor axis of 1 to 3 μm. The photograph observed with the polarization microscope by the crossed Nicol of the obtained cellulose nanofiber dispersion liquid B is shown in FIG.

(Dispersion C)
Cellulose nanofibers were pulverized in the same manner as in the preparation of Dispersion B except that the amount of cellulose nanofibers was 10 parts by weight. The pulverized cellulose nanofibers after pulverization were aggregated in a rod shape having an average major axis of 6 μm and an average minor axis of 1 to 3 μm. The photograph observed with the polarization microscope by the crossed Nicol of the obtained cellulose nanofiber dispersion C is shown in FIG.

(Dispersion D)
Cellulose nanofiber IPA dispersion (manufactured by Daicel Corporation, average fiber diameter 200 nm, average fiber length of about 100 μm, 2.5 wt% IPA dispersion) 10 parts by weight, CAP 0.2 part by weight, MEK 50 parts by weight and MMPG30 It melt | dissolved in the mixed solvent of the weight part. Such a cellulose nanofiber suspension was prepared and pulverized using a bead mill (NM-G5M) at a zirconia bead of 1 mmΦ and a peripheral speed of 15 m / s. The pulverized cellulose nanofibers were aggregated in a rod shape having an average major axis of 8 μm and an average minor axis of 1 to 3 μm.

(Dispersion E)
As the IPA dispersion of cellulose nanofiber, 20 parts by weight of IPA dispersion of cellulose nanofiber (manufactured by Daicel Corporation, average fiber diameter 200 nm, average fiber length of about 50 μm, 2.5 wt% IPA dispersion) was used. Pulverized cellulose nanofibers in the same manner as in the preparation of Dispersion D. The pulverized cellulose nanofibers were aggregated in a rod shape having an average major axis of 8 μm and an average minor axis of 1 to 3 μm.

(Dispersion F)
Cellulose nanofibers were pulverized in the same manner as in the preparation of Dispersion E, except that the amount of cellulose nanofiber IPA dispersion was 40 parts by weight. The pulverized cellulose nanofibers were aggregated in a rod shape having an average major axis of 8 μm and an average minor axis of 1 to 3 μm.

(Dispersion G)
Cellulose nanofibers were pulverized in the same manner as in the preparation of Dispersion A except that a dissolver disk (circumferential speed 18 m / second) was used instead of the bead mill. The pulverized cellulose nanofibers were aggregated in a rod shape having an average major axis of 30 μm and an average minor axis of 1 to 3 μm.

(Dispersion H)
Instead of the bead mill, the cellulose nanofibers were crushed in the same manner as in the preparation of the dispersion A, except that ultrasonic treatment (42 kHz, 600 / second) was performed. The pulverized cellulose nanofibers were aggregated in a rod shape having an average major axis of 20 μm and an average minor axis of 1 to 3 μm. The photograph observed with the polarizing microscope by the cross Nicol of the obtained cellulose nanofiber dispersion liquid H is shown in FIG.

[Preparation of coating solution]
(Hard coat layer coating solution: NC-1)
A solvent was added to dispersion A21.1 parts by weight so that the composition of MEK 100 parts by weight, MMPG 50 parts by weight and BuOH 20 parts by weight was prepared, and then dipentaerythritol hexaacrylate (Daicel Cytec) was added to the mixture. Co., Ltd., DPHA) 40 parts by weight, pentaerythritol triacrylate (Daicel Cytec Co., Ltd., PETIA) 60 parts by weight, and CAP 0.7 parts by weight were dissolved. In the obtained solution, 2 parts by weight of photopolymerization initiator A (Ciba Japan Co., Ltd., trade name “Irgacure 184”) and photopolymerization initiator B (Ciba Japan Co., Ltd., trade name “Irgacure 907”) were prepared. ") 1 part by weight was added and dissolved. The resulting solution was stirred for 1 hour to prepare a hard coat layer coating solution: NC-1.

(Hard coat layer coating solution: NC-2)
A hard coat layer coating solution: NC-2 was prepared in the same manner as NC-1, except that the dispersion A was changed to the dispersion B.

(Hard coat layer coating solution: NC-3)
The hard coat layer coating solution: NC-3 was changed in the same manner as NC-2 except that the weight ratio of DPHA and PETIA was changed to DPHA / PETIA = 70/30 and dispersion B was changed to dispersion C. Prepared.

(Hard coat layer coating solution: NC-4)
A hard coat layer coating solution: NC-4 was prepared in the same manner as NC-3 except that the dispersion C was changed to the dispersion D.

(Hard coat layer coating solution: NC-5)
A hard coat layer coating solution: NC-5 was prepared in the same manner as NC-3 except that the dispersion C was changed to the dispersion E.

(Hard coat layer coating solution: NC-6)
A hard coat layer coating solution: NC-6 was prepared in the same manner as NC-3 except that the dispersion C was changed to the dispersion F.

(Hard coat layer coating solution: NCL-1)
Further, hard coat layer coating solution: NCL-1 in the same manner as NC-2 except that 7 parts by weight of hollow silica (“A2SL-02SH” manufactured by JGC Catalysts & Chemicals Co., Ltd., 20 wt% alcohol dispersion) is added. Was prepared.

(Hard coat layer coating solution: NCL-2)
Furthermore, except for adding 7 parts by weight of hollow silica (“A2SL-03SH” manufactured by JGC Catalysts & Chemicals Co., Ltd., 20% by weight alcohol dispersion), a hard coat layer coating solution: NCL-2 in the same manner as NC-4 Was prepared.

(Hard coat layer coating solution: NCL-3)
Further, a hard coat layer coating solution: NCL-3 was prepared in the same manner as NC-5 except that 7 parts by weight of hollow silica (A2SL-03SH) was added.

(Hard coat layer coating solution: NCL-4)
Further, a hard coat layer coating solution: NCL-4 was prepared in the same manner as NC-6 except that 7 parts by weight of hollow silica (A2SL-03SH) was added.

(Hard coat layer coating solution: HC-1)
A hard coat layer coating solution: HC-1 was prepared in the same manner as NC-1, except that the dispersion A was changed to the dispersion G.

(Hard coat layer coating solution: HC-2)
A hard coat layer coating solution: HC-2 was prepared in the same manner as NC-1, except that the dispersion A was changed to the dispersion H.

(Hard coat layer coating solution: HCL-1)
A hard coat layer coating solution: HCL-1 was prepared in the same manner as NCL-2 except that the dispersion B was 5 parts by weight.

Examples 1 to 10 and Comparative Examples 1 and 3
As a transparent film, a triacetyl cellulose film (manufactured by Fuji Film Co., Ltd., TAC, thickness 80 μm) is used, and on this film, a hard coat layer coating solution NC-1 to 6, NCL1 to 4, HC-1 or HCL-1 was coated using a bar coater # 20 and then dried at 60 ° C. for 1 minute. The coated film is passed through an ultraviolet irradiation device (USHIO INC., High pressure mercury lamp, ultraviolet irradiation amount: 200 mJ / cm ² ), subjected to ultraviolet curing treatment, and has a hard coat layer and a surface uneven structure. Formed. The thickness of the hard coat layer in the obtained optical film was about 6 μm.

Comparative Example 2
An optical film was produced in the same manner as in Example 1 except that the hard coat layer coating solution HC-2 was coated using a bar coater # 26. The thickness of the hard coat layer in the obtained optical film was about 7 μm.

  As a result of measuring the optical characteristics, the surface structure and the size of the cellulose nanofiber aggregates for the optical films obtained in Examples and Comparative Examples, Table 1 shows the evaluation results of various characteristics.

  As is clear from the results in Table 1, the optical films of the examples are excellent in various properties, whereas in the optical films of Comparative Examples 1 and 2, aggregation of cellulose nanofibers was visually observed, The optical films of Comparative Examples 2 and 3 have low antiglare properties.

  About the surface of the hard-coat layer obtained in Example 7, the polarizing microscope photograph by an open Nicol is shown in FIG. 4, and the polarizing microscope photograph by a cross Nicol is shown in FIG.

  Moreover, about the surface of the hard-coat layer obtained by the comparative example 2, the polarizing microscope photograph by an open Nicol is shown in FIG. 6, and the polarizing microscope photograph by a cross Nicol is shown in FIG.

  Furthermore, with respect to the surface of the hard coat layer obtained in Comparative Example 3, a polarizing microscope photograph by open Nicol is shown in FIG. 8, and a polarizing microscope photograph by crossed Nicols is shown in FIG.

  From the result of FIGS. 4-9, in the hard-coat layer of an Example, a fine uneven structure is formed in the surface, and a cellulose nanofiber aggregate can also be confirmed. On the other hand, in the hard coat layer of Comparative Example 2, a concavo-convex structure larger than that of Example 7 was formed on the surface. Moreover, in the hard-coat layer of the comparative example 3, although a cellulose nanofiber aggregate can be confirmed, it can confirm that the uneven structure is not formed in the surface.

  The optical film of the present invention can be used in various display devices such as liquid crystal display (LCD) devices, cathode ray tube display devices, organic or inorganic electroluminescence (EL) displays, field emission displays (FED), surface electric field displays (SED), It can be used as an optical film used in display devices such as a rear projection television display, a plasma display, and a display device with a touch panel.

  Among these, the optical film of the present invention is useful for various displays including PC monitors and televisions, and can exhibit anti-glare properties without being affected by the surrounding environment. It is particularly useful as an antiglare film for displays such as computers (PCs) and display devices with touch panels.

Claims (13)

  An optical film comprising a transparent film and a hard coat layer formed on the transparent film and having a concavo-convex structure on the surface, wherein the hard coat layer comprises a curable resin precursor and cellulose nanofibers. An optical film which is formed of a cured product of the adhesive composition and the convex portions on the surface of the hard coat layer contain cellulose nanofiber aggregates.   The optical film according to claim 1, wherein the cellulose nanofibers constituting the cellulose nanofiber aggregate are oriented in random directions, and the aggregate forms a bright spot portion by observation with a polarizing microscope using crossed Nicols.   The optical film according to claim 1 or 2, wherein the cellulose nanofiber aggregate is rod-shaped and the average major axis of the cellulose nanofiber aggregate is 15 µm or less.   The optical film according to any one of claims 1 to 3, wherein the cellulose nanofibers are unevenly distributed in the convex portion.   5. An uneven structure having an average interval Sm of 80 μm or more and less than 600 μm, an arithmetic average roughness Ra of 0.05 to 1.5 μm, and an arithmetic average inclination Δa of 0.05 to 5 ° is formed on the surface of the hard coat layer. The optical film in any one of.   The optical film according to claim 1, wherein the cellulose nanofiber has an average fiber diameter of 10 to 500 nm.   The ratio of cellulose nanofiber is 0.01-3 weight part with respect to 100 weight part of curable resin precursor, The optical film in any one of Claims 1-6.   The optical film according to claim 1, wherein the curable composition further comprises a polymer having no ethylenically unsaturated bond.   The optical film according to claim 8, wherein the polymer having no ethylenically unsaturated bond is a cellulose derivative.   The optical film according to claim 1, wherein the curable composition further comprises hollow silica particles.   The optical film according to claim 10, wherein the hollow silica particles are unevenly distributed around the cellulose nanofiber aggregate.   The optical film according to claim 1, wherein the hard coat layer contains substantially no flocculant.   The manufacturing method of the optical film of Claim 1 which apply | coats the coating liquid for forming a hard-coat layer on a transparent film, and hardens | irradiates with an active energy ray after drying.