JP5778997B2 - Optical film and manufacturing method thereof - Google Patents

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.

  On the other hand, in recent years, with the progress of electronic displays as man-machine interfaces, interactive input systems have become widespread, and in particular, devices in which a touch panel (coordinate input device) is integrated with a display are widely used. In addition, light-weight and thin displays such as liquid crystal displays can be made keyboard-less, and the features are alive, so the number of cases where touch panels are used in mobile devices is increasing. The touch panel can be classified into an optical method, an ultrasonic method, a capacitance method, a resistance film method, and the like according to a position detection method. Among these, the resistive film method has rapidly spread in recent years because of its simple structure and excellent price / performance ratio.

  A resistive film type touch panel is an electrical component formed by holding two films or plates having transparent electrodes on opposite sides and holding them at regular intervals. The operation method is that after fixing one transparent electrode, press the other transparent electrode with a pen or finger from the viewing side, bend it, and contact and conduct with the fixed transparent electrode. Is detected and a predetermined input is made. In such a touch panel operation method, when an electrode is pressed with a pen or a finger, a rainbow pattern due to interference (a so-called “Newton ring” interference color) is formed around the finger or the pointing jig such as the pen. (Or interference fringes) may appear, reducing the visibility of the screen. Specifically, when two transparent electrodes contact or bend due to contact, and the distance between the two transparent electrodes facing each other is about the wavelength of visible light (about 0.5 μm), the two transparent electrodes Interference of reflected light occurs in the space between the electrodes, and Newton rings are generated. The occurrence of such a Newton ring is an unavoidable phenomenon on the principle of a resistive film type touch panel. As a countermeasure for reducing Newton's ring in such a touch panel, a process of forming a concavo-convex structure on the surface of a support film for forming a transparent electrode is used.

  As described above, the LCD and the touch panel are provided with an optical film (or light scattering film) having a concavo-convex structure on the surface, and this optical film is usually composed of fine particles such as resin fine particles and silica fine particles, and a binder resin or It is obtained by applying a mixture with a curable resin to a substrate and forming a fine concavo-convex structure on the surface. However, the concavo-convex structure has anti-glare property and anti-Newton ring property, but disturbs the pixel by acting as a lens when disposed on the viewing side of the display device with respect to the pixel. Therefore, in order to prevent `` glitter '' that appears as flickering due to a difference in brightness that appears with the naked eye, the direction to reduce the unevenness interval, such as a method that makes the unevenness interval less than half the pixel size, etc. Has been studied.

  For example, JP 2009-265143 A is disclosed as an anti-glare film capable of displaying an excellent transmission image and having an excellent anti-glare property in a plasma display panel (PDP) which has been spreading in recent years along with LCDs. 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%. There. In this document, the content of silica fine particles is described as 0.05 to 30% (particularly 0.2 to 25%) of the film weight. In addition, as a method for forming an aggregate structure of silica fine particles, a method using a flocculant such as alkyl acetoacetate aluminum diisopropylate is described. In the examples, a hard coat layer having a blend of 1.5 to 9 parts by weight with respect to 100 parts by weight of the hard coat material and having a haze of 1.92 to 2.02% and an uneven period of 46 to 80 μm is formed. Yes.

  However, in this antiglare sheet, since the uneven period is small, if the centerline average roughness Ra is large, the whiteness is not improved and the blackness cannot be improved. Conversely, if Ra is small, the antiglare property is lowered. Further, since the ratio of the silica fine particles is large, the mechanical properties of the hard coat layer are lowered. Furthermore, in order to agglomerate a large amount of silica fine particles, an aggregating agent is necessary, which causes bleeding out.

  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 this optical film, since Sm is as small as 200 μm or less, the antiglare property is lowered when the haze is low.

  Furthermore, in recent years, high-definition display devices with fine pixel sizes have been developed for LCDs and touch panels, and the size of pixels has become smaller and smaller with the increasing accuracy of display devices. Therefore, when the interval between the irregularities is reduced with respect to the pixel size, the antiglare property does not appear if the irregularity height is small, while the tendency of whiteness becomes more pronounced if the irregularity height is large. Therefore, it has become more difficult to achieve both the antiglare property and the sharpness of the image. Further, in order to prevent glare, a method of increasing the internal haze of the optical film and making the difference in luminance uniform has been studied. However, since the haze is high, the sharpness of the image is greatly impaired. Furthermore, in touch panels and the like, since the size of the display device is small and high definition is progressing, the pixel size is very small, and it is difficult to make the uneven spacing smaller than the pixel size in order to prevent glare. there were.

JP 2009-265143 A (claims, paragraph [0028], examples) JP 2007-219485 A (Claims, Examples)

  Accordingly, an object of the present invention is to provide an optical film having excellent antiglare property or anti-Newton ring property and capable of displaying a clear image without whiteness and a method for producing the same.

  Another object of the present invention is to provide an optical film capable of suppressing glare and improving the blackness of a high-definition display device having a small pixel size despite being thin, and a method for manufacturing the same. is there.

  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 unexpectedly found that the surface of the hard coat layer formed on the transparent film has irregularities larger than the small pixel size in the high-definition display device. By forming the structure, it was found that the antiglare property or anti-Newton ring property can be improved, and a clear image can be displayed without whiteness, and the present invention has been 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 the average distance Sm600 between the tops of the convex portions on the surface of the hard coat layer. A concavo-convex structure having a thickness of ˜1500 μm and an arithmetic average roughness Ra of 0.04 to 0.2 μm is formed. The arithmetic mean slope Δa of the concavo-convex structure may be 0.05 to 5 °. The optical film of the present invention may have a haze of about 0.1 to 2%. The optical film of the present invention has a transmission image definition with an optical comb width of 0.125 mm of about 1 to 67%, a transmission image definition of 0.25 mm with an optical comb width of about 2 to 67%, and an optical comb width. The transmitted image definition of 0.5 mm is about 10 to 85%, the transmitted image definition of 1 mm optical comb width is about 50 to 95%, and the transmitted image definition of 2 mm optical comb width is 80 to 99%. It may be a degree. The hard coat layer may be formed of a cured product of a curable composition containing a curable resin precursor and cellulose nanofibers. The cellulose nanofibers may have an average fiber diameter of about 10 to 500 nm and an average fiber length of about 20 to 500 μm. 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 (for example, a cellulose derivative) that does not have an ethylenically unsaturated bond. The curable composition may further contain hollow silica particles. An optical film formed of a curable composition containing a hard silica layer containing hollow silica particles may have a surface reflectance of 4% or less. The hollow silica particles may be unevenly distributed near the surface of the hard coat layer. The hard coat layer may have a thickness of 30 μm or less. 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 this production method, drying may be performed at a temperature of 70 ° C. or lower.

  In the present invention, the surface of the hard coat layer formed on the transparent film has a concavo-convex structure larger than the small pixel size in the high-definition display device, thus improving antiglare property or anti-Newton ring property. In addition, it is possible to display a clear image in which whitening is suppressed (not white). In particular, by forming a concavo-convex structure using cellulose nanofibers, glare can be suppressed and blackness can be improved in spite of being thin with respect to a high-definition display device having a small pixel size. Moreover, when a hard-coat layer is formed with the hardened | cured material of the curable composition containing a curable resin precursor and a cellulose nanofiber, scratch resistance and mechanical characteristics can also be improved. Furthermore, since the concavo-convex structure exhibiting excellent optical properties can be formed without blending the flocculant, an optical film in which bleeding out of the flocculant and the like is suppressed can be obtained. Furthermore, an optical film having low reflection and low haze can be easily produced by applying cellulose nanofibers and hollow silica particles to the curable composition.

[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 characterized in that an uneven structure larger than the size of a small pixel of about 40 to 200 μm is formed on the surface. In particular, by adjusting this concavo-convex structure to a gentle structure with a low height, it is possible to suppress glare and improve anti-glare and anti-Newton ring properties even though it is a clear film with low haze. it can.

(Surface structure of hard coat layer)
Specifically, the uneven structure on the surface has an average interval Sm between the tops of 600 to 1500 μm, preferably about 620 to 1400 μm, more preferably about 650 to 1300 μm (particularly 700 to 1200 μm), and high antiglare properties. And in order to implement | achieve anti-Newton ring property, about 650-1100 micrometers (especially 700-1000 micrometers) may be sufficient. In the present invention, by making Sm larger than a small pixel, both antiglare property, anti-Newton ring property and visibility can be achieved. If Sm is too small, glare occurs and the image becomes white and the transparency is lowered. When Sm is too large, antiglare property and anti-Newton ring property are deteriorated.

  The arithmetic average roughness Ra of the concavo-convex structure is 0.04 to 0.2 μm, preferably 0.05 to 0.19 μm, more preferably 0.06 to 0.18 μm (particularly 0.07 to 0.15 μm). In order to realize high antiglare properties and anti-Newton ring properties, it may be about 0.05 to 0.12 μm (particularly 0.07 to 0.1 μm). In the present invention, the height of the concavo-convex structure is low and the sharpness of the image can be improved by reducing Ra in this way even though Sm is large. When Ra is too small, antiglare property will fall. If Ra is too large, the sharpness of the image decreases.

  The arithmetic average slope Δa of the concavo-convex structure is, for example, about 0.05 to 5 °, preferably about 0.06 to 4 °, more preferably about 0.07 to 3 ° (particularly 0.08 to 2 °). In order to realize high antiglare property and anti-Newton ring property, it may be about 0.1 to 1.5 ° (particularly 0.5 to 1.0 °). In the present invention, since Δa is small and the concavo-convex structure is gentle, an excellent scattering effect can be exhibited despite the large concavo-convex structure, and the antiglare property and the anti-Newton ring property can be improved. When Δa is too small, the antiglare property and the anti-Newton ring property are lowered. If Δa is too large, the sharpness of the image decreases.

  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 is only required to be formed of a transparent and hard material, but from the point that a hard coat layer excellent in optical properties and mechanical properties can be easily produced, You may be 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 thermosetting compounds or resins [low molecular weight compounds having an epoxy group, a polymerizable group, an isocyanate group, an alkoxysilyl group, a silanol group, etc. (for example, epoxy resins, unsaturated polyester resins) , Urethane resins, silicone resins, etc.)], photocurable compounds curable with actinic rays (such as ultraviolet rays) (photocurable monomers, ultraviolet curable compounds such as oligomers), etc. May be an EB (electron beam) curable compound. 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 oligomer or resin, may contain a copolymerizable monomer. These photocurable compounds can be used alone or in combination of two or more.

  Furthermore, the curable resin precursor may contain a curable compound containing a fluorine atom from the viewpoint of improving the strength of the hard coat layer. Precursors containing fluorine atoms (fluorine-containing curable compounds) include fluorides of the monomers and oligomers such as fluorinated alkyl (meth) acrylates [for example, perfluorooctylethyl (meth) acrylate and trifluoro Ethyl (meth) acrylate, etc.], fluorinated (poly) oxyalkylene glycol di (meth) acrylate [eg, fluoroethylene glycol di (meth) acrylate, fluoropropylene glycol di (meth) acrylate, etc.], fluorine-containing epoxy resin, fluorine Examples thereof include urethane-based resins.

  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 about 90/10 to 10/90, more preferably about 80/20 to 20/80, and suppresses haze. For example, it may be about 50/50 to 10/90 (particularly 40/60 to 10/90).

  The number average molecular weight of the curable resin precursor is, for example, 5000 or less, preferably 2000 or less, and more preferably about 1000 or less.

  The curable resin precursor may contain a curing agent depending on the type. For example, the thermosetting resin may contain a curing agent such as amines and polyvalent carboxylic acids, and the photocurable resin may contain a photopolymerization initiator. Examples of the photopolymerization initiator include conventional components such as acetophenones or propiophenones, benzyls, benzoins, benzophenones, thioxanthones, acylphosphine oxides, and the like. The content of the curing agent such as a photocuring agent is 0.1 to 20 parts by weight, preferably 0.5 to 10 parts by weight, more preferably 1 to 8 parts by weight (100 parts by weight based on 100 parts by weight of the curable resin precursor. In particular, it is about 1 to 5 parts by weight, and may be about 3 to 8 parts by weight.

  Furthermore, the curable resin precursor may contain a curing accelerator. For example, the photocurable resin may contain a photocuring accelerator, for example, a tertiary amine (such as a dialkylaminobenzoic acid ester), a phosphine photopolymerization accelerator, and the like.

(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, etc.) such as Manila hemp and New Zealand hemp]], animal-derived cellulose fibers (eg squirt cellulose), bacteria-derived cellulose fibers, chemically synthesized cellulose fibers [cellulose acetate (cellulose acetate) , Cellulose propionate, cellulose butyrate, Organic acid esters such as roulose acetate propionate and cellulose acetate butyrate; inorganic acid esters such as cellulose nitrate, cellulose sulfate and cellulose phosphate; mixed acid esters such as cellulose nitrate acetate; hydroxyalkyl cellulose (eg, hydroxyethyl cellulose (HEC)) , Hydroxypropyl cellulose, etc.); carboxyalkyl cellulose (carboxymethyl cellulose (CMC), carboxyethyl cellulose, etc.); alkyl cellulose (methyl cellulose, ethyl cellulose, etc.); regenerated cellulose (rayon, cellophane, etc.), etc.] . 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.

  Although the average fiber diameter of cellulose nanofiber will not be specifically limited if it is nanometer size, For example, it is 10-500 nm, Preferably it is 20-300 nm, More preferably, it is about 30-200 nm (especially 50-100 nm) grade. If the average fiber diameter is too small, it will be difficult to form an uneven structure. If the average fiber diameter is too large, it becomes difficult to form a large uneven structure with a gentle slope. In the present invention, a large concavo-convex structure can be formed by manufacturing under specific conditions using a nanometer-sized fiber without using a particle having a large particle size, and thus the concavo-convex structure can be formed even for a thin hard coat layer. Can be formed. Furthermore, when a particle having a large particle size is used, it is difficult to form a concavo-convex structure with a gentle slope, but by using cellulose nanofiber, a concavo-convex structure with a gentle slope can be easily formed.

Furthermore, the standard deviation of the fiber diameter distribution is, for example, 80 nm or less (for example, 1 to 80 nm), preferably 3 to 50 nm, more preferably 5 to 40 nm (particularly 10 to 30 nm) from the viewpoint that a uniform uneven structure can be formed. It may be a degree . Further, the maximum fiber diameter may be less than 500 nm, for example, 30 to 300 nm, preferably 40 to 200 nm, and more preferably about 50 to 100 nm.

  In the present invention, the average fiber diameter, the standard deviation of the fiber diameter distribution, and the maximum fiber diameter are values calculated from a fiber diameter (about n = 20) measured based on an electron micrograph.

  The average fiber length of the cellulose nanofibers may be about 10 μm or more, for example, can be selected from a range of about 10 to 1000 μm. From the point that a predetermined uneven structure can be formed on the surface of the hard coat layer and the optical characteristics can be improved. For example, it is 20-900 micrometers, Preferably it is 30-800 micrometers (for example, 35-700 micrometers), More preferably, it is about 40-600 micrometers (especially 50-500 micrometers). If the average fiber length is too small, it will be difficult to form an uneven structure. If the average fiber length is too large, the concavo-convex structure becomes too large, it is difficult to form a gentle concavo-convex structure, and the sharpness of the image is deteriorated.

  Furthermore, the ratio of the average fiber length to the average fiber diameter (average fiber length / average fiber diameter) (average aspect ratio) is about 40 or more, for example, 50 to 50000, preferably 80 to 25000, more preferably 150 to 10000. (Especially 500 to 6000). In the present invention, by using nanofibers having a relatively long fiber length and aspect ratio in spite of having a nano-sized average diameter, appropriately entangled nanofibers are produced by convection in the production process. After separation into a dense region and a sparse region, an appropriate uneven structure can be formed because a convex portion is formed in the dense region.

  The cross-sectional shape of the cellulose nanofiber (cross-sectional shape perpendicular to the longitudinal direction of the fiber) may be an anisotropic shape (flat shape) such as bacterial cellulose. Isotropic shape. 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).

  Cellulose nanofibers may be prepared in the form of a dispersion (or suspension) by dispersing in water in a curable composition. 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, more preferably about 0.3 to 10% by weight (particularly 0.5 to 5% by weight). is there.

The ratio of the cellulose nanofiber can be selected from a range of, for example, about 0.01 to 3 parts by weight with respect to 100 parts by weight of the curable resin precursor, but an appropriate uneven structure can be formed without deteriorating optical properties. From the point, for example, 0.02 to 2 parts by weight, preferably 0.03 to 1 part by weight, and more preferably 0.04 to 0.5 parts by weight (particularly 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. If the ratio of cellulose nanofibers is too large, the optical properties will deteriorate.

(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.

Examples of cellulose esters include aliphatic organic acid esters (cellulose acetate such as cellulose diacetate and cellulose triacetate; cellulose C ₂₋ such as cellulose propionate, cellulose butyrate, cellulose acetate propionate, and cellulose acetate butyrate). ₆ acylates), aromatic organic acid esters (C _7-12 aromatic carboxylic acid esters such as cellulose phthalate and cellulose benzoate), inorganic acid esters (eg cellulose phosphate, cellulose sulfate and the like), and the like. The cellulose esters may be mixed acid esters such as acetic acid and cellulose nitrate esters.

Examples of cellulose ethers include cyanoethyl cellulose; hydroxy C _2-4 alkyl cellulose such as hydroxyethyl cellulose and hydroxypropyl cellulose; C _1-6 alkyl cellulose such as methyl cellulose and ethyl cellulose; carboxymethyl cellulose or a salt thereof, benzyl cellulose, and acetylalkyl. A cellulose etc. can be illustrated. Examples of cellulose carbamates include cellulose phenyl carbamate.

These cellulose derivatives can be used alone or in combination of two or more. Among these cellulose derivatives, cellulose esters, particularly cellulose C _2-6 acylates such as cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, and cellulose acetate butyrate are preferable. Among them, 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 nanofibers can be aggregated in the coating liquid. Cellulose C _2-4 acylates such as cellulose diacetate, cellulose acetate propionate, cellulose acetate butyrate (especially cellulose acetate C _3-4 acylates such as cellulose acetate propionate) to suppress and enhance storage stability Is preferred.

  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). 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 shape of the inorganic particles is not particularly limited, and examples thereof include a spherical shape, an elliptical shape, a polygonal shape (polygonal pyramid shape, a rectangular parallelepiped shape, a rectangular parallelepiped shape, etc.), a plate shape, a rod shape, and an indefinite shape. Of these shapes, an isotropic shape such as a substantially spherical shape is preferable from the viewpoint of optical characteristics.

The average particle diameter of the inorganic particles is 100nm or less, preferably 80nm or less (e.g., 10 to 8 0 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. 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 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). 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).

  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.

Of these solvents, ketones such as methyl ethyl ketone, alcohols such as butanol, cellosolves such as propylene glycol monomethyl ether are preferred, may be mixed together. For example, the ketones and the alcohols and / or the cellosolves are the former / the latter = 90/10 to 10/90, preferably 70/30 to 30/70, more preferably 60/40 to 40 /. You may mix in the ratio (weight ratio) of about 60.

  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). In the present invention, a thin hard coat layer having a thickness of 30 μm or less can be formed in spite of having a large uneven structure having an Sm value of 600 μm or more.

[Transparent film]
Examples of the transparent film (or substrate film) include resin sheets in addition to glass and ceramics. As resin which comprises a transparent film, resin similar to the said hard-coat layer can be used. Preferred transparent films include transparent polymer films such as cellulose derivatives [cellulose triacetate (TAC), cellulose acetate such as cellulose diacetate], polyester resins [polyethylene terephthalate (PET), polybutylene terephthalate (PBT), poly Arylate resins, etc.], polysulfone resins [polysulfone, polyethersulfone, etc.], polyether ketone resins [polyether ketone, polyether ether ketone, etc.], polycarbonate resins (bisphenol A type polycarbonate, etc.), polyolefin resins ( Polyethylene, polypropylene, etc.), cyclic polyolefin resin [TOPAS (registered trademark), ARTON (registered trademark), Zeonet ZEONEX (registered trademark, etc.), halogen-containing resins (polyvinylidene chloride, etc.), (meth) acrylic resins, styrene resins (polystyrene, etc.), vinyl acetate or vinyl alcohol resins (polyvinyl alcohol, etc.), etc. Examples include formed films. The transparent film may be uniaxially or biaxially stretched.

  These films can be appropriately selected according to the application, and when an optical film is used for the upper electrode substrate of the touch panel (the electrode substrate on the side in contact with a pressing member such as a finger or a pen), flexibility is required. A plastic sheet or film (unstretched or stretched plastic sheet or film) can be used.

Examples of the optically isotropic transparent film include glass, unstretched or stretched plastic sheet or film, for example, polyester (PET, PBT, etc.), cellulose derivatives, particularly cellulose esters (cellulose diacetate, A sheet or film formed of cellulose acetate such as cellulose triacetate, cellulose acetate propionate, cellulose acetate C _3-4 acylate such as cellulose acetate butyrate, or the like is preferable. 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 5 to 2000 μm, preferably 15 to 1000 μm, and more preferably about 20 to 500 μm.

[Optical film]
By having the hard coat layer, the optical film of the present invention has high antiglare property and anti-Newton ring property, but haze is suppressed and high transparency.

  The optical film of the present invention has a haze based on JIS K7136 of, for example, 0.1 to 2%, preferably 0.15 to 1.5%, more preferably 0.2 to 1% (particularly 0.3 to 0.8%). 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 transmitted image definition of the optical film of the present invention is 0.1-67% when an optical comb with a width of 0.125 mm is used, that is, the transmitted image with an optical comb width of 0.125 mm is, for example, 1 to 67%, preferably 1. It is about 5 to 55%, more preferably about 2 to 50% (especially 5 to 40%).

  The transmitted image definition with an optical comb width of 0.25 mm is, for example, about 2 to 67%, preferably about 3 to 60%, and more preferably about 4 to 55% (particularly 8 to 50%).

  The transmitted image definition with an optical comb width of 0.5 mm is, for example, about 10 to 85%, preferably about 15 to 80%, and more preferably about 20 to 75% (particularly about 25 to 70%).

  The transmitted image clarity with an optical comb width of 1 mm is, for example, about 50 to 95%, preferably 55 to 93%, and more preferably about 60 to 92% (particularly 70 to 90%).

  The transmitted image clarity with an optical comb width of 2 mm is, for example, about 80 to 99%, preferably 85 to 98%, and more preferably about 90 to 98% (particularly 94 to 98%).

  When the transmitted image definition is in the above-mentioned range, scattering of the straight transmitted light is small. Therefore, even when the optical film is disposed in a high-definition display device, scattering from each pixel is reduced, resulting in glare. Can be prevented.

  The transmitted image definition is a scale for quantifying blur and distortion of light transmitted through a film. The transmitted image definition is measured through an optical comb that moves the transmitted light from the film, and a value is calculated based on the amount of light in the bright and dark portions of the optical comb. That is, when the film blurs the transmitted light, the image of the slit formed on the optical comb becomes thick, so that the amount of light at the transmissive portion is 100% or less, while the light leaks at the non-transmissive portion, so 0% That's it. The value C of the transmitted image definition is defined by the following equation from the maximum transmitted light value M of the transparent portion and the minimum transmitted light value m of the opaque portion of the optical comb.

C (%) = [(M−m) / (M + m)] × 100
That is, the closer the value of C is to 100%, the smaller the blur of the image due to the transparent conductive film [Reference: Suga, Mitamura, Painting Technology, July 1985 issue].

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, due to Ru is contained inorganic particles having a low refractive index in the hard coat layer may reduce the surface reflectance, surface reflectance is 4% or less, preferably 1-4%, more preferably 2 to It may be 3.5% 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.

  Further, when the optical film of the present invention is used as an anti-Newton ring film, a transparent conductive layer, for example, a metal oxide such as indium oxide-tin oxide composite oxide (ITO) is further formed on the hard coat layer. You may laminate the transparent conductive layer comprised by these, and the transparent conductive layer comprised by the conductive polymer.

  The optical film of the present invention has hard coat properties and high antiglare properties or anti-Newton ring 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 optical film of the present invention is not particularly limited as long as the uneven 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. In this invention, it is preferable to disperse | distribute cellulose nanofiber uniformly in a coating liquid with a conventional method, for example, you may process a coating liquid with an ultrasonic wave.

  The concentration of the solute (curable resin precursor, cellulose 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. 1 to 80% by weight, preferably 5 to 60% by weight, and more preferably 15 to 50% by weight (especially 20 to 45% by weight).

  In addition, when the said liquid mixture is apply | coated to a transparent film, a transparent film may melt | dissolve or swell depending on the kind of solvent. For example, when a coating solution (uniform solution) containing a resin component is applied to a triacetyl cellulose film, the coated surface of the triacetyl cellulose film may be eluted, eroded, or swollen depending on the type of solvent. In such a case, an optically isotropic solvent-resistant coating layer may be formed by previously applying a solvent-resistant coating agent on the application surface of a transparent film (such as a triacetyl cellulose film). Such coating layers include, for example, AS resins, polyester resins, thermoplastic resins such as polyvinyl alcohol resins (polyvinyl alcohol, ethylene-vinyl alcohol copolymer, etc.), epoxy resins, silicone resins, and UV curable types. It can be formed using a curable resin such as a resin. Moreover, when apply | coating a liquid mixture or a coating liquid to a transparent support body, according to the kind of transparent film, you may select the solvent which does not melt | dissolve, erode, or swell a transparent film.

  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. If necessary, the coating solution may be applied a plurality of times.

  After the mixture is cast or applied, the solvent is evaporated. The evaporation of the solvent can be usually selected from the range of about 30 to 200 ° C., for example, depending on the boiling point of the solvent. In the present invention, the drying temperature is used to form a specific uneven structure on the surface of the hard coat layer. Is important and can be selected depending on the type of the curable resin precursor. For example, it is 70 ° C. or lower (for example, 20 to 65 ° C.), preferably 30 to 65 ° C., more preferably 40 to 60 ° C. (especially 45 to 60 ° C.). Degree). 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 cellulose nanofibers dispersed in the coating liquid are appropriately aggregated together with the curing of the curable composition, although the coating liquid does not contain a flocculant, and the resin component becomes a nucleus. It can be presumed that it is raised and forms an uneven structure on the surface.

  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. The amount of irradiation light (irradiation energy) varies depending on the thickness of the coating film, but may be, for example, about 50 to 10,000 mJ / cm ² , preferably 70 to 7000 mJ / cm ² , and more preferably about 100 to 5000 mJ / cm ² .

  In the case of an electron beam, a method of irradiating an electron beam with an 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 exposure 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").

[Transparent image (map) definition]
Based on JIS K7105, the film sharpness of the optical film and the direction of the comb teeth of the optical comb were measured using a mapping measuring instrument (trade name “ICM-1T” manufactured by Suga Test Instruments Co., Ltd.). The film was placed so that and were parallel to each other and measured. Among the optical combs of the mapping measuring instrument, the mapping clarity was measured in an optical comb having a width of 0.125 to 2 mm.

[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.

[Anti-Newton ring property]
Install the optical film on the glass substrate so that the hard coat layer of the optical film is in contact with the glass substrate, and visually observe the occurrence of Newton rings when pressed with a finger from the transparent film side. It was evaluated with.

○: Newton ring was not generated. Δ: Newton ring was slightly observed. ×: Newton ring was generated.

[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), the arithmetic average roughness Ra, between the tops of the projections, under the conditions of a scanning range of 3 mm and a scanning frequency of 2 The average interval Sm and the arithmetic average slope Δa were measured.

[Preparation of coating solution]
(Hard coat layer coating solution: NC-1)
50 parts by weight of dipentaerythritol hexaacrylate (manufactured by Daicel Cytec Co., Ltd., DPHA), 50 parts by weight of pentaerythritol triacrylate (manufactured by Daicel Cytec Co., Ltd., PETIA), cellulose acetate propionate (manufactured by Eastman Corporation, 0.5 part by weight of CAP) is dissolved in a mixed solvent of 100 parts by weight of methyl ethyl ketone (MEK), 50 parts by weight of 1-methoxy-2-propanol (MMPG) and 50 parts by weight of 1-butanol (BuOH) (boiling point 113 ° C.). did. To this solution, 2 parts by weight of a photopolymerization initiator (trade name “Irgacure 184” manufactured by Ciba Japan Co., Ltd.) was added and dissolved. Furthermore, 5 parts by weight of cellulose nanofibers (manufactured by Daicel Chemical Industries, Ltd., average fiber diameter of 70 nm, average fiber length of about 800 μm, 1% by weight aqueous dispersion) were added to this solution, and the mixture was stirred for 1 hour, and hard coated Layer coating solution: NC-1 was prepared.

(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 average fiber length of the cellulose nanofibers was changed to about 400 μm.

(Hard coat layer coating solution: NC-3)
A hard coat layer coating solution: NC-3 was prepared in the same manner as NC-1, except that the average fiber length of the cellulose nanofibers was changed to about 200 μm.

(Hard coat layer coating solution: NC-4)
A hard coat layer coating solution: NC-4 was prepared in the same manner as NC-1, except that the average fiber length of the cellulose nanofibers was changed to about 100 μm.

(Hard coat layer coating solution: NC-5)
Except changing the addition amount of a cellulose nanofiber to 3 weight part, it carried out similarly to NC-1, and prepared hard-coat layer coating liquid: NC-5.

(Hard coat layer coating solution: NC-6)
A hard coat layer coating solution: NC-6 was prepared in the same manner as NC-2 except that the amount of cellulose nanofiber added was changed to 3 parts by weight.

(Hard coat layer coating solution: NC-7)
A hard coat layer coating solution: NC-7 was prepared in the same manner as NC-3, except that the amount of cellulose nanofiber added was changed to 3 parts by weight.

(Hard coat layer coating solution: NC-8)
Except changing the addition amount of a cellulose nanofiber to 3 weight part, it carried out similarly to NC-4, and prepared the hard-coat layer coating liquid: NC-8.

(Hard coat layer coating solution: NC-9)
Hard coat layer coating solution in the same manner as NC-8, except that the addition amount of dipentaerythritol hexaacrylate (DPHA) is changed to 20 parts by weight and the addition amount of pentaerythritol triacrylate (PETIA) is changed to 50 parts by weight: NC-9 was prepared.

(Hard coat layer coating solution: NC-10)
A hard coat layer coating solution: NC- 10 was prepared in the same manner as NC-1 except that the average fiber length of the cellulose nanofiber was changed to about 60 μm and the addition amount was changed to 10 parts by weight.

(Hard coat layer coating solution: NC-11)
Except changing the addition amount of a cellulose nanofiber to 15 weight part, it carried out similarly to NC-10, and prepared the hard-coat layer coating liquid: NC-11.

(Hard coat layer coating solution: NCL-1)
Further, hard coat layer coating solution: NCL-1 in the same manner as NC-1, 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)
Further, a hard coat layer coating solution: NCL-2 was prepared in the same manner as NC-5 except that 7 parts by weight of hollow silica (A2SL-02SH) was added.

(Hard coat layer coating solution: NCL-3)
Further, a hard coat layer coating solution: NCL-3 was prepared in the same manner as NC-6 except that 7 parts by weight of hollow silica (A2SL-02SH) 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-7 except that 7 parts by weight of hollow silica (A2SL-02SH) was added.

(Hard coat layer coating solution: NCL-5)
Further, a hard coat layer coating solution: NCL-5 was prepared in the same manner as NC-8 except that 7 parts by weight of hollow silica (A2SL-02SH) was added.

(Hard coat layer coating solution: NCL-6)
Further, a hard coat layer coating solution: NCL-6 was prepared in the same manner as NC-9 except that 7 parts by weight of hollow silica (A2SL-02SH) was added.

(Hard coat layer coating solution: NCL-7)
Further, a hard coat layer coating solution: NCL-7 was prepared in the same manner as NC-10 except that 7 parts by weight of hollow silica (A2SL-02SH) was added.

(Hard coat layer coating solution: NCL-8)
Further, a hard coat layer coating solution: NCL-8 was prepared in the same manner as NC-11 except that 7 parts by weight of hollow silica (A2SL-02SH) was added.

(Hard coat layer coating solution: HC-1)
Instead of cellulose nanofibers, a hard coat layer coating solution: HC-1 was added in the same manner as NC-1 except that 0.1 part by weight of a fluorine leveling agent was added together with the initiator without ultrasonic treatment. Prepared.

(Hard coat layer coating solution: HC-2)
Further, except for adding 5 parts by weight of silica particles (“Chihosta KE-P150” manufactured by Nippon Shokubai Co., Ltd., average particle size 1.5 μm), a hard coat layer coating solution: HC-2 Was prepared.

(Hard coat layer coating solution: HC-3)
Further, a hard coat layer coating solution: HC-3 was prepared in the same manner as HC-1, except that 1 part by weight of styrene beads (average particle size: 3.5 μm) was added.

(Hard coat layer coating solution: HC-4)
Further, a hard coat layer coating solution: HC-4 was prepared in the same manner as HC-1, except that 20 parts by weight of acrylic beads (average particle size: 7 μm) was added.

Example 1
A triacetyl cellulose film (manufactured by Fuji Film Co., Ltd., TAC, thickness 80 μm) was used as a transparent film, and a hard coat layer coating solution NC-1 was applied onto this film using a bar coater # 26. Then, it was dried at 50 ° C. for 1 minute. The coated film is passed through an ultraviolet irradiation device (USHIO INC., High pressure mercury lamp, ultraviolet irradiation amount: 800 mJ / cm ² ) to perform ultraviolet curing treatment, and a hard coat layer having a hard coat property and a surface uneven structure. Formed. The thickness of the hard coat layer in the obtained optical film was about 8 μm.

Examples 2 to 19 and Comparative Examples 1 to 2
An optical film was produced in the same manner as in Example 1 except that the hard coat layer coating solution NC-2 to 11 , NCL1 to 8 , and HC-1 to 2 were used instead of the hard coat layer coating solution NC-1. did. The thickness of the hard coat layer was about 7 μm in Example 3 (NC-3) and Example 6 (NC-6), about 9 μm in Example 1 2 (NCL-1), and Comparative Example 1 (HC-1). ) Was about 6 μm and Comparative Example 2 (HC-2) was about 7 μm, except for about 7 μm.

Comparative Example 3
An optical film was produced in the same manner as in Example 1 except that the drying temperature after coating was changed to 80 ° C. The thickness of the hard coat layer in the obtained optical film was about 8 μm.

Comparative Examples 4-5
Instead of the hard coat layer coating liquid NC-1, the hard coat layer coating liquid HC-3 or HC-4 was used, and the drying temperature after coating was changed to 70 ° C., as in Example 1. An optical film was prepared. The thickness of the hard coat layer in the obtained optical film was about 6 μm in Comparative Example 4 (HC-3) and about 12 μm in Comparative Example 5 (HC-4).

  About the optical film obtained by the Example and the comparative example, the result of having measured the optical characteristic is shown in Table 1, the result of having measured the surface structure, and the evaluation result of various characteristics are shown in Table 2.

  As is clear from the results in Tables 1 and 2, the optical films of the examples are excellent in optical properties and mechanical properties. On the other hand, the optical film of the comparative example has low optical properties.

  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.

  The touch panel is a display device (liquid crystal display device, plasma display device, organic or inorganic EL display device) in a display unit of an electric / electronic or precision device such as a personal computer, a television, a mobile phone, a game machine, a mobile device, a clock, a calculator, etc. Etc.) may be used in combination with the touch panel (especially resistive film type touch panel).

  Among these, the optical film of the present invention is particularly useful as an antiglare film for LCDs and an anti-Newton ring film for touch panels.

Claims (13)

An optical film comprising a transparent film and a hard coat layer formed on the transparent film,
On the surface of the hard coat layer, a concavo-convex structure having an average interval between tops of convex portions Sm 700 to 1200 μm and an arithmetic average roughness Ra 0.04 to 0.2 μm is formed ,
Haze is 0.1 to 2%,
The transmission image definition with an optical comb width of 0.125 mm is 1.5 to 55%, the transmission image definition with an optical comb width of 0.25 mm is 3 to 60%, and the transmission image definition with an optical comb width of 0.5 mm. degree is 15 to 80%, a transmission image clarity of the optical comb width 1mm is 55-93%, and the optical film transmission image clarity of the optical comb width 2mm is Ru 85-98% der.   The optical film according to claim 1, wherein the arithmetic average inclination Δa of the concavo-convex structure is 0.05 to 5 °. Hard coat layer, an optical film according to claim 1 or 2, wherein is formed with a cured product of a curable composition comprising a curable resin precursor and cellulose nanofibers. The optical film of claim 3 Symbol mounting cellulose nanofibers having an average fiber length of the average fiber diameter and 20~500μm of 10 to 500 nm. The optical film according to claim 3 or 4 , wherein a ratio of the cellulose nanofiber is 0.01 to 3 parts by weight with respect to 100 parts by weight of the curable resin precursor. The optical film according to any one of claims 3 to 5 , wherein the curable composition further comprises a polymer having no ethylenically unsaturated bond. The optical film according to claim 6 , wherein the polymer having no ethylenically unsaturated bond is a cellulose derivative. The optical film according to any one of claims 3 to 7 , wherein the curable composition further contains hollow silica particles. The optical film according to claim 8 , wherein the surface reflectance is 4% or less. The optical film according to any one of claims 1 to 9 the thickness of the hard coat layer is 30μm or less. The optical film according to any one of claims 1 to 10 , wherein the hard coat layer does not substantially contain a 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. The manufacturing method of Claim 12 which dries at the temperature of 70 degrees C or less.