JP6048506B2 - Optical film - Google Patents

Description

  The present invention relates to an optical film in which a cured film is formed on a thin film substrate.

  In recent years, various display devices such as a liquid crystal television, a plasma display, and an organic EL (Electro Luminescence) display have been developed in addition to a CRT (Cathode Ray Tube), and their screen sizes have been increased. In such a display device, a hand or an object may touch the screen directly, and the screen is easily damaged. Therefore, in order to prevent scratches, an optical film in which a hard coat layer (cured film) is formed on a film substrate or an optical film in which an antireflection layer is further formed on the hard coat layer is usually displayed. Pasting on the display screen of the apparatus is performed.

  In the production of such an optical film, a film substrate is used in which both ends in the width direction are provided with a portion (convex portion) that is called a knurling portion or an embossed portion and is higher in volume than the film surface. By forming a knurling part on the film base material, when the produced film base material is wound around the core, the film base is displaced in the core direction, and the base materials are blocked (attached). Can be suppressed. By forming a hard coat layer on the surface of such a film substrate, an optical film with a hard coat layer can be obtained. The obtained optical film is wound around the core again.

  Here, in manufacturing an optical film with a hard coat layer, for example, in Patent Documents 1 and 2, the hard coat layer is formed on the film base so that the knurling portion of the film base is located outside the hard coat layer. In addition, another knurling portion is additionally formed on the knurling portion of the film base material. In this case, since the additional knurling portion can be formed by using the unevenness of the previously formed knurling portion, the desired height can be easily obtained without increasing the thickness of the unevenness portion of the embossing roll. The knurling portion can be formed with high accuracy. Further, for example, in Patent Document 3, an optical film is manufactured by applying a hard coat layer up to a knurling portion of a film substrate and forming fine protrusions on the back surface of the knurling portion.

  By the way, in recent years, along with the thinning of the display device, there has been a demand for thinning of the optical film used. Here, when the wound diameter when winding the manufactured optical film around the core is constant, when winding a thin optical film, the number of windings is smaller than when winding a thick optical film. Can be increased. For this reason, as a thin optical film, it becomes possible to manufacture a long (for example, 3000 m or more) optical film having a large number of windings.

  However, in Patent Documents 1 and 2, since the knurling part is formed on a film base material softer than the hard coat layer, the knurling part is crushed by its own weight or pressing force when winding the long optical film. It becomes easy. When the knurling portion is crushed, it becomes impossible to suppress winding deviation and blocking of the optical film. Further, in Patent Document 3, the fine protrusion on the back surface of the knurling portion is considered to be a protrusion provided on the back surface of the film base material that is the base of the hard coat layer, but this protrusion is softer than the hard coat layer, so When the long optical film is wound up, the protrusions are easily crushed and it is impossible to suppress winding deviation and the like.

  Accordingly, it is desirable to configure the optical film so that winding deviation and blocking can be reliably suppressed even when a long and thin optical film is wound.

Japanese Patent Laying-Open No. 2005-219272 (refer to claim 1, paragraph [0028], FIG. 1, etc.) Japanese Patent Laying-Open No. 2009-223129 (see paragraph [0026], FIG. 1 etc.) Japanese Patent Laying-Open No. 2004-347928 (see claim 4, paragraph [0015], etc.)

  In view of the above circumstances, an object of the present invention is to provide an optical film that can reliably suppress winding slippage and blocking even when a long, thin optical film is wound.

  The above object of the present invention is achieved by the following configurations.

1. An optical film in which a cured film is formed on a film substrate having a thickness of 10 to 40 μm,
When each region from the both ends in the width direction of the film base to 50 mm is a first region and a second region,
The cured film covers a range of 20 to 100% in the width direction in the first region and a range of 20 to 100% in the width direction in the second region on the film substrate. Is formed,
An uneven knurling portion is formed on the surface of the cured film in each of the first region and the second region by knurling after the cured film is formed,
The knurling part is formed on the surface of the cured film over 3 mm or more in the width direction from each end of the cured film.

  2. 2. The optical film as described in 1 above, wherein the knurling part has a height of 1 to 25 μm.

3. 3. The optical film as described in 1 or 2 above, wherein the number of convex portions of the knurling portion is 10 to 140 per 1 cm ² .

  4). 4. The optical film as described in any one of 1 to 3 above, wherein the cured film has an elastic modulus of 4.0 GPa or more.

  According to said structure, the uneven | corrugated knurling part is formed in the surface of the cured film on a thin film base material with a thickness of 10-40 micrometers by knurling after formation of a cured film. The knurling part does not use only the unevenness formed on the film base material, and has the hardness of the cured film, so that even when the optical film is wound up, the knurling part is not easily crushed by its own weight or pressing force. Thereby, even when a thin and long optical film is wound, winding deviation in the core direction and blocking can be suppressed.

  Moreover, since the knurling part is formed over 3 mm from the end in the width direction of the film base material, the resistance to the width direction (core direction) can be surely increased. The strength of the part can also be secured reliably. As a result, winding deviation and blocking in the core direction when winding a thin optical film can be reliably suppressed.

  Further, the cured film covers a range of 20 to 100% in the width direction in the first region and the second region (regions from each end in the width direction to 50 mm) on the film substrate. Since it is formed, the formation range of the cured film in the first region and the second region is 10 mm (corresponding to 20% of 50 mm) to 50 mm (corresponding to 100% of 50 mm) in the width direction. Accordingly, it is possible to reliably ensure a knurling portion forming width of 3 mm or more on the surface of the cured film in the first region and the second region.

It is sectional drawing which shows the schematic structure of the optical film which concerns on embodiment of this invention. It is sectional drawing which shows the other structure of the said optical film. It is sectional drawing which expands and shows the cured film of the optical film of FIG. 1 and FIG. 1 is a cross-sectional view illustrating a schematic configuration of an optical film of Example 1. FIG. It is sectional drawing which shows the schematic structure of the optical film of Example 10. 10 is a cross-sectional view showing a schematic configuration of an optical film of Example 11. FIG. It is sectional drawing which shows the schematic structure of the optical film of Example 12. It is sectional drawing which shows the schematic structure of the optical film of Example 13. 6 is a cross-sectional view illustrating a schematic configuration of an optical film of Comparative Example 2. FIG.

  An embodiment of the present invention will be described below with reference to the drawings. In the present specification, when the numerical range is expressed as A to B, the numerical value range includes the values of the lower limit A and the upper limit B.

[Configuration of optical film]
FIG. 1 is a cross-sectional view along the width direction showing a schematic configuration of the optical film F of the present embodiment. The width direction refers to a direction (TD direction; Transverse Direction) perpendicular to the longitudinal direction (conveyance direction, MD direction: Machine Direction) in the film plane. The optical film F is a hard coat film in which a cured film 2 as a hard coat layer is formed on a film substrate 1. The film substrate 1 has a thickness of 10 to 40 μm, and is a thin film substrate. Here, for convenience of explanation below, each region from the both ends in the width direction of the film substrate 1 to 50 mm is defined as a first region R1 and a second region R2.

  The cured film 2 is made of an active energy ray curable resin such as an ultraviolet curable resin. The details of the resin material of the cured film 2 will be described later. The elastic modulus of the cured film 2 can be controlled by appropriately selecting or controlling the resin material of the cured film 2 and the irradiation conditions (irradiation amount, etc.) of the active energy rays.

Here, the elastic modulus indicates a proportional coefficient between strain and stress, and a material having a small strain relative to the stress has a high elastic modulus and is hard (a material having a small elastic modulus is soft). When an active energy ray-curable resin is used, the elastic modulus of the cured film 2 can be controlled by the number of functional groups in the resin material, addition of particles, and curing conditions. For example, an elastic modulus of 4.0 GPa or more can be realized by irradiating an active energy ray-curable acrylate having two or more functional groups with an active ray energy ray of 300 mJ / cm ² or more.

  The cured film 2 covers a range of 20 to 100% in the width direction in the first region R1 and a range of 20 to 100% in the width direction in the second region R2 on the film substrate 1 respectively. Is formed. FIG. 1 shows a case where the cured film 2 is formed on the film substrate 1 so as to cover a 20% range in the width direction in each of the first region R1 and the second region R2. . In this case, in the first region R1 and the second region R2, the length in the width direction of the cured film 2 is 20% of 50 mm, that is, 10 mm.

  On the other hand, FIG. 2 is a cross-sectional view along the width direction showing another configuration of the optical film F. In the optical film F of FIG. 2, the cured film 2 is formed so as to cover a 100% range in the width direction in the first region R1 and the second region R2, respectively. In this case, in the first region R1 and the second region R2, the length in the width direction of the cured film 2 is 100% of 50 mm, that is, 50 mm.

  Therefore, when the cured film 2 is formed on the film substrate 1 so as to cover the range of 20 to 100% in the width direction in the first region R1 and the second region R2, respectively, the first region The length in the width direction of the cured film 2 in R1 and the second region R2 is 10 to 50 mm.

  In FIG. 1 and FIG. 2, the cured film 2 is formed continuously from the first region R1 to the second region R2 in the film width direction, but may be formed discontinuously. . For example, the cured film 2 is formed only in the first region R1 and the second region R2, and may not be formed between the first region R1 and the second region R2. In this case, the cured film 2 is formed only for the purpose of forming a hard knurling portion 3 described later, rather than protecting the surface of the film substrate 1. Further, the cured film 2 is formed between the first region R1 and the second region R2, and the first region is positioned so as to be spaced apart from the cured film 2 in the width direction. The cured film 2 may be formed in R1 and the second region R2.

  In addition, an uneven knurling portion 3 is formed on the surface of the cured film 2 in each of the first region R1 and the second region R2. In FIG. 1 and FIG. 2, for the sake of convenience, the knurling part 3 is illustrated in a layered shape with a flat surface for the purpose of clarifying the formation region of the knurling part 3. However, as shown in FIG. The surface of the knurling part 3 is uneven. The knurling part 3 is formed by a knurling process in which an embossing roll having an uneven pattern on the surface is heated and pressed onto the cured film 2. That is, the knurling part 3 is formed by knurling after the cured film is formed. At this time, by setting the heating temperature of the embossing roll higher than the glass transition temperature Tg of the cured film 2, the knurling part 3 can be formed without causing cracks in the cured film 2. The knurling part 3 may be formed by pressing an embossing roll before the cured film 2 is cured by ultraviolet irradiation or the like (for example, in a semi-cured state), and then completely curing the cured film material.

  The knurling part 3 is formed on the surface of the cured film 2 over 3 mm or more in the width direction from each end in the width direction of the cured film 2. That is, in FIG. 1 and FIG. 2, when the formation width of the knurling part 3 on the cured film 2 is indicated by d (mm), d ≧ 3.

  Moreover, in the structure of FIG. 1, in the case of the knurling process with respect to the cured film 2, by pressing an embossing roll on the surface of the film base material 1 in addition to the cured film 2, the surface of the film base material 1 is uneven. A knurling portion 4 is formed. In addition, before forming the cured film 2, the knurling part may be formed in advance in the width direction both ends of the film base material 1, and the knurling part may be formed. Good. When the knurling part is previously formed on the film base material 1, the knurling part 4 is additionally formed (laminated) on the film base material 1 when the knurling part 3 is formed on the cured film 2. . Of course, as shown in FIG. 2, when the cured film 2 is formed up to the end of the film substrate 1, the knurling process is performed only on the cured film 2 and the knurling part 3 is formed only on the surface of the cured film 2. (The knurling part 4 is not formed).

  The knurling part 3 can be formed with the same hardness as the cured film 2 by performing knurling on the surface of the cured film 2 to form the knurling part 3 as in the present embodiment. Thereby, even when the film base 1 winds up a thin optical film F of 10 to 40 μm, the knurling part 3 is not easily crushed by its own weight or pressing force, and winding deviation in the core direction and blocking can be suppressed. . Moreover, by suppressing blocking, it is possible to suppress the occurrence of black bands (band-like streaks appearing in the circumferential direction) due to uneven thickness in the width direction of the optical film F.

  Moreover, in 1st area | region R1 and 2nd area | region R2 whose length of the width direction is 50 mm, the cured film 2 is formed so that it may each cover the range of 20 to 100% of the width direction, and cured film The formation range of 2 is 10 to 50 mm in the width direction as described above. Thereby, it becomes possible to form the knurling part 3 in the width direction over 3 mm or more on the surface of the cured film 2 in the first region R1 and the second region R2. And by forming the knurling part 3 on the surface of the cured film 2 in this way (over 3 mm or more in the width direction), the resistance to the width direction, that is, the core direction can be surely increased. Further, by forming the knurling portion 3 in a wide range of 3 mm or more in the width direction, the strength of the knurling portion 3 can be reliably ensured. As a result, winding deviation and blocking in the core direction when winding the thin optical film F can be reliably suppressed.

  Moreover, in this embodiment, since the elastic modulus of the cured film 2 is 4.0 GPa or more and the cured film 2 is hard, a function of suppressing the above-described winding deviation and blocking by performing a knurling process on the surface of the cured film 2. It is possible to reliably realize the hard knurling portion 3 that exhibits the following.

  Moreover, since the cured film 2 has a low coefficient of static friction and is smooth and easy to stick, the configuration of this embodiment capable of suppressing winding deviation and blocking has a thickness of 70 μm or less including the cured film 2. Further, it is very effective for winding a thin optical film F having a thickness of 50 μm or less. In this way, when winding of the optical film F becomes possible while suppressing winding deviation and blocking of the optical film F, when producing a polarizing plate using the optical film F, production of the polarizing plate is performed thereafter. Can be improved.

  FIG. 3 is an enlarged cross-sectional view of the cured film 2. In the present embodiment, the height t of the knurling portion 3 is 1 to 25 μm. Here, the height t of the knurling part 3 is the knurling part 3 from the surface of the cured film 2 where the unevenness of the knurling part 3 is not formed (the surface of the cured film 2 before being knurled). Refers to the height (maximum height) of the convex portion 3a. The height t of the knurling part 3 can be controlled by adjusting the pressing force against the cured film 2 of the embossing roll used during the knurling process.

  When the height t of the knurling portion 3 is less than 1 μm, the effect of suppressing the winding deviation by the knurling 3 is reduced, and the films are likely to be blocked when the film is wound. On the other hand, when the height t of the knurling part 3 exceeds 25 μm, the convex part 3a of the knurling part 3 easily falls down in the width direction at the time of winding the film, and the roll is wound in the cross section along the width direction. Warpage (deformation) is likely to occur, and it becomes difficult to secure a good winding shape.

  Therefore, by setting the height t of the knurling portion 3 in the range of 1 to 25 μm, it is possible to improve the winding shape by suppressing deformation of the roll while suppressing winding deviation and blocking during film winding.

Moreover, in this embodiment, the number (density) of the convex parts 3a of the knurling part 3 on the surface of the cured film 2 is 10 to 140 per 1 cm ² . In addition, the number of the convex parts 3a can be adjusted by selecting an appropriate thing from several embossing rolls from which the number per unit area of the convex part used as a type | mold on the surface differs, and performing a knurling process.

When the number of the convex portions 3a of the knurling portion 3 is less than 10 / cm ² , the number of the convex portions 3a is too small, and the function of the knurling portion 3, that is, the function of suppressing the above-described winding deviation and blocking is efficiently exhibited. Can not do. On the other hand, if the number of convex portions 3a exceeds 140 pieces / cm ² , the risk of film breakage increases. That is, when knurling is performed such that the number of convex portions 3a exceeds 140 pieces / cm ² , damage to the film base material 1 increases, and the strength of the film base material 1 in the width direction decreases. The risk of breakage increases.

Therefore, by setting the number of the convex portions 3a of the knurling portion 3 to 10 to 140 pieces / cm ² , the function of the knurling portion 3 that suppresses winding deviation and blocking can be reliably exerted, and the breakage of the film can be suppressed. it can.

  In addition, when the cured film material is applied to the edge of the film base material 1 at the time of forming the cured film 2 on the film base material 1, the cured film material wraps around the back surface of the film base material 1, and also on the back surface. A cured film may be formed. In order to avoid such a situation, the cured film 2 is applied by applying a cured film material from the position at least 5 mm away from the end of the film substrate 1 to the inside in the width direction (opposite the end). It is desirable to form.

  In the above, a functional layer such as an antireflection layer is not provided on the cured film 2, but the configuration of the present embodiment described above can be applied even when a functional layer is provided. That is, by providing a functional layer on the cured film 2 and forming the knurling part 3 on the cured film 2 on the outer side in the width direction of the functional layer, it is possible to suppress the winding deviation or the like of the optical film F. . The knurling part 3 may be formed on the surface of the cured film 2 before the functional layer is formed, or may be formed after the functional layer is formed.

  In particular, when a layer containing a fluorine-based activator (antifouling layer) is provided as a functional layer to improve antifouling properties, winding dislocation or the like is likely to occur. In this case, the cured film 2 The configuration of the present embodiment in which the knurling portion 3 is provided on the top is very effective.

[Details of each layer]
Hereinafter, the details of each layer of the optical film F described above will be described.

[Hard coat layer]
The hard coat layer as the cured film described above is formed of an active energy ray curable resin. The active energy ray curable type refers to a resin that is cured through a crosslinking reaction or the like by irradiation with active rays such as ultraviolet rays or electron beams, and specifically, a resin having an ethylenically unsaturated group. The active energy ray curable resin includes both an active energy ray curable isocyanurate derivative and an active energy ray curable resin other than the isocyanurate derivative.

<Active energy ray-curable isocyanurate derivative>
The active energy ray-curable isocyanurate derivative is not particularly limited as long as it is a compound having a structure in which one or more ethylenically unsaturated groups are bonded to an isocyanuric acid skeleton. Compounds having three or more ethylenically unsaturated groups and one or more isocyanurate rings in the same molecule shown are preferred. The kind of ethylenically unsaturated group is an acryloyl group, a methacryloyl group, a styryl group, and a vinyl ether group, more preferably a methacryloyl group or an acryloyl group, and particularly preferably an acryloyl group.

L ² in the formula is a divalent linking group, preferably a substituted or unsubstituted alkyleneoxy group or polyalkyleneoxy group having 4 or less carbon atoms in which a carbon atom is bonded to the isocyanurate ring. Particularly preferred are alkyleneoxy groups, which may be the same or different. R ² represents a hydrogen atom or a methyl group, and may be the same or different. Although the specific compound shown by General formula (1) is shown below, it is not restricted to these.

  Examples of the other compounds include isocyanuric acid diacrylate compounds, and isocyanuric acid ethoxy-modified diacrylates represented by the following general formula (2) are preferable.

  In addition, other examples include ε-caprolactone-modified active energy ray-curable isocyanurate derivatives, specifically, compounds represented by the following general formula (3).

Of R ₁ to R ₃ of the above chemical formulas -, the following a, b, although functional groups attached represented by c, at least one of R ₁ to R ₃ is a functional group b.

a: -H, or _{- (CH 2) n-OH} (n = 1~10, preferably n = 2 to 6)
_{b :-( CH 2) n-O-} (COC 5 H 10) m-COCH = CH 2 (n = 1~10, preferably n = 2~6, m = 2~8)
c: — (CH ₂ ) n—O—R (R is a (meth) acryloyl group, n = 1 to 10, preferably n = 2 to 6)
Although the specific compound shown by General formula (3) is shown below, it is not restricted to these.

  As a commercial item of an isocyanuric acid triacrylate compound, Shin-Nakamura Chemical Co., Ltd. A-9300 etc. are mentioned, for example. As a commercial item of an isocyanuric acid diacrylate compound, Toagosei Co., Ltd. Aronix M-215 etc. are mentioned, for example. Examples of the mixture of the isocyanuric acid triacrylate compound and the isocyanuric acid diacrylate compound include Aronix M-315 and Aronix M-313 manufactured by Toagosei Co., Ltd.

  As the ε-caprolactone-modified active energy ray-curable isocyanurate derivative, A-9300-1CL manufactured by Shin-Nakamura Chemical Co., Ltd., which is ε-caprolactone-modified tris- (acryloxyethyl) isocyanurate, manufactured by Toagosei Co., Ltd. Examples include, but are not limited to, Aronix M-327.

<Active energy ray-curable resins other than isocyanurate derivatives>
Active energy ray curable resins other than isocyanurate derivatives include UV curable urethane acrylate resins, UV curable polyester acrylate resins, UV curable epoxy acrylate resins, UV curable polyol acrylate resins, or UV curable resins. Epoxy resins and the like are preferably used. Of these, UV curable acrylate resins are preferred.

  As the ultraviolet curable acrylate resin, a polyfunctional acrylate is preferable. The polyfunctional acrylate is preferably selected from the group consisting of pentaerythritol polyfunctional acrylate, dipentaerythritol polyfunctional acrylate, pentaerythritol polyfunctional methacrylate, and dipentaerythritol polyfunctional methacrylate. Here, the polyfunctional acrylate is a compound having two or more acryloyloxy groups or methacryloyloxy groups in the molecule.

  Examples of the polyfunctional acrylate monomer include ethylene glycol diacrylate, diethylene glycol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, trimethylolpropane triacrylate, trimethylolethane triacrylate, and tetramethylolmethane triacrylate. , Tetramethylolmethane tetraacrylate, pentaglycerol triacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, glycerol triacrylate, dipentaerythritol triacrylate, dipentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol Lithol hexaacrylate, tris (acryloyloxyethyl) isocyanurate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, trimethylolpropane trimethacrylate, trimethylolethane trimethacrylate, Tetramethylol methane trimethacrylate, tetramethylol methane tetramethacrylate, pentaglycerol trimethacrylate, pentaerythritol dimethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, glycerol trimethacrylate, dipentaerythritol trimethacrylate, dipentaerythritol tetramethacrylate Acrylate, dipentaerythritol penta methacrylate, dipentaerythritol hexa methacrylate, and the like preferably.

  A monofunctional acrylate may be used as the active energy ray-curable resin other than the isocyanurate derivative. Monofunctional acrylates include isobornyl acrylate, 2-hydroxy-3-phenoxypropyl acrylate, isostearyl acrylate, benzyl acrylate, ethyl carbitol acrylate, phenoxyethyl acrylate, lauryl acrylate, isooctyl acrylate, tetrahydrofurfuryl acrylate, behenyl Examples include acrylate, 4-hydroxybutyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and cyclohexyl acrylate. Monofunctional acrylates can be obtained from Shin Nakamura Chemical Co., Ltd., Osaka Organic Chemical Industry Co., Ltd., and the like. These compounds are used alone or in admixture of two or more. Moreover, oligomers, such as a dimer and a trimer of the said monomer, may be sufficient.

  The viscosity of the polyfunctional acrylate is preferably 3000 mPa · s or less, more preferably 2000 mPa · s or less, at 25 ° C. In addition, said viscosity is the value measured on 25 degreeC conditions using the B-type viscometer.

  In the case where an active energy ray-curable isocyanurate derivative and an active energy ray-curable resin other than the isocyanurate derivative are used in combination in the hard coat layer, the active energy ray-curable isocyanurate derivative (A) and the isocyanurate derivative are used. By using the content mass ratio with the active energy ray-curable resin (B) other than that in the range of (A) :( B) = 10: 90 to 50:50, the film strength (scratch resistance) is excellent. Is preferable.

  The hard coat layer preferably contains a photopolymerization initiator in order to accelerate the curing of the active energy ray-curable resin. The amount of the photopolymerization initiator is preferably a photopolymerization initiator: active energy ray-curable resin = 20: 100 to 0.01: 100 by mass ratio.

  Specific examples of the photopolymerization initiator include acetophenone, benzophenone, hydroxybenzophenone, Michler's ketone, α-amyloxime ester, thioxanthone, and derivatives thereof, but are not particularly limited thereto. .

  Moreover, in order to prevent blocking, improve scratch resistance, etc., it is preferable to add inorganic or organic fine particles to the active energy ray-curable resin. As inorganic fine particles, silicon oxide, titanium oxide, aluminum oxide, tin oxide, indium oxide, ITO, zinc oxide, zirconium oxide, magnesium oxide, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated silicic acid Mention may be made of calcium, aluminum silicate, magnesium silicate and calcium phosphate. In particular, silicon oxide, titanium oxide, aluminum oxide, zirconium oxide, magnesium oxide and the like are preferably used.

  These inorganic fine particles are preferably coated with an organic component having a reactive functional group on a part of the surface because the scratch resistance is improved while maintaining the transparency of the optical film. As an aspect in which a part of the surface is coated with an organic component having a reactive functional group, for example, a compound containing an organic component such as a silane coupling agent reacts with a hydroxyl group present on the surface of the metal oxide fine particles, A mode in which an organic component is bonded to a part of the surface, a mode in which an organic component is attached to a hydroxyl group present on the surface of a metal oxide fine particle by an interaction such as a hydrogen bond, or one or two or more in a polymer particle Examples include inorganic fine particles.

  The organic fine particles include polymethacrylic acid methyl acrylate resin powder, acrylic styrene resin powder, polymethyl methacrylate resin powder, silicon resin powder, polystyrene resin powder, polycarbonate resin powder, benzoguanamine resin powder, melamine resin. Powder, polyolefin resin powder, polyester resin powder, polyamide resin powder, polyimide resin powder, polyfluoroethylene resin powder, and the like can be used.

  Preferred organic fine particles include crosslinked polystyrene particles (for example, SX-130H, SX-200H, SX-350H manufactured by Soken Chemical), polymethyl methacrylate-based particles (for example, MX150 and MX300 manufactured by Soken Chemical), and fluorine-containing acrylic resin fine particles. Can be mentioned. Examples of the fluorine-containing acrylic resin fine particles include commercial products such as FS-701 manufactured by Nippon Paint. Examples of the acrylic particles include Nippon Paint: S-4000, and examples of the acrylic-styrene particles include Nippon Paint: S-1200, MG-251.

  The average particle diameter of these fine particle powders is not particularly limited, but is preferably 0.01 to 5 μm, and particularly preferably 0.01 to 1.0 μm. Moreover, you may contain 2 or more types of microparticles | fine-particles from which a particle size differs. The average particle diameter of the fine particles can be measured by, for example, a laser diffraction particle size distribution measuring device.

  The proportion of the ultraviolet curable resin composition and the fine particles is preferably such that the fine particles are blended so as to be 10 to 400 parts by mass, more preferably 50 to 200 parts by mass with respect to 100 parts by mass of the resin composition. .

  In addition, the hard coat layer according to the present embodiment is provided by applying a hard coat layer coating composition diluted with a solvent onto a film substrate by the following method, drying, and curing. It is preferable from the viewpoint that interlayer adhesion with a material is easily obtained. As the solvent, ketones or esters are preferable. Examples of ketones include methyl ethyl ketone, acetone, cyclohexanone, and methyl isobutyl ketone. Examples of esters include methyl acetate, ethyl acetate, butyl acetate, and propyl acetate. It is not limited. Other solvents include alcohols (ethanol, methanol, butanol, n-propyl alcohol, isopropyl alcohol, diacetone alcohol), hydrocarbons (toluene, xylene, benzene, cyclohexane), glycol ethers (propylene glycol monomethyl ether, Propylene glycol monopropyl ether, ethylene glycol monopropyl ether, etc.) can be preferably used.

  By using these solvents in the range of 20 to 200 parts by mass with respect to 100 parts by mass of the active energy ray-curable resin, the stability as a coating composition is excellent.

  The coating amount of the hard coat layer coating composition is suitably 0.1 to 40 μm in wet film thickness, preferably 0.5 to 30 μm, and average film thickness 0.1 to 30 μm in dry film thickness. , Preferably 1 to 20 μm, particularly preferably 4 to 15 μm.

  The hard coat layer was coated with a hard coat layer coating composition that forms a hard coat layer using a known coating method such as a gravure coater, dip coater, reverse coater, wire bar coater, die (extrusion) coater, or ink jet method. Thereafter, it can be formed by drying, UV curing treatment, and further heat treatment for UV curing as necessary.

As a light source used for the UV curing treatment, any light source that generates ultraviolet rays can be used without limitation. For example, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a carbon arc lamp, a metal halide lamp, a xenon lamp, or the like can be used. Irradiation conditions vary depending on individual lamps, irradiation of active rays, usually, 50~1000mJ / cm ^2, preferably 100 to 500 mJ / cm ^2.

  Moreover, when irradiating actinic radiation, it is preferable to carry out while applying tension | tensile_strength in the conveyance direction of a film, More preferably, it is performing applying tension | tensile_strength also in the width direction. The tension to be applied is preferably 30 to 300 N / m. The method for applying tension is not particularly limited, and tension may be applied in the conveying direction on the back roll, or tension may be applied in the width direction or biaxial direction by a tenter. Thereby, a film having further excellent flatness can be obtained.

  The hard coat layer may contain a conductive agent in order to impart antistatic properties. Preferred conductive agents include metal oxide particles or π-conjugated conductive polymers. An ionic liquid is also preferably used as the conductive compound. In addition, the hard coat layer has a nonionic surfactant such as a silicone surfactant, a fluorosurfactant or a polyoxyether, an anionic interface, from the viewpoint of coating properties and the uniform dispersibility of fine particles. An activator and a fluorine-siloxane graft polymer may be included. The fluorine-siloxane graft polymer refers to a copolymer polymer obtained by grafting polysiloxane containing siloxane and / or organosiloxane alone and / or organopolysiloxane to at least a fluorine-based resin. Examples of commercially available products include ZX-022H, ZX-007C, ZX-049, and ZX-047-D manufactured by Fuji Kasei Kogyo Co., Ltd. Moreover, it is preferable to add these components in 0.01-3 mass% with respect to the solid content component in a coating liquid.

  The hard coat layer may be a single layer or a plurality of layers. In order to easily control the hard coat property, haze, and arithmetic surface roughness Ra of the hard coat layer, the hard coat layer may be divided into two or more layers. Moreover, you may provide a hard-coat layer on both surfaces of a film base material.

  The thickness of the uppermost layer when two or more hard coat layers are provided is preferably in the range of 0.05 to 2 μm. Two or more layers may be formed as a simultaneous multilayer. The simultaneous multi-layering is a method of forming a hard coat layer by applying two or more hard coat layers on a base material without going through a drying step. In order to laminate the second hard coat layer on the first hard coat layer without a drying process, the layers are stacked one after another by an extrusion coater or simultaneously by a slot die having a plurality of slits. Can be done.

  The hard coat layer has a pencil hardness, which is an index of hardness, of H or higher, more preferably 4H or higher. If it is 4H or more, the surface film base of a large-sized liquid crystal display device or a liquid crystal display device for digital signage that is not only difficult to be scratched in the polarizing plate forming process of the liquid crystal display device but is often used for outdoor applications. Excellent film strength when used as a material. Pencil hardness is one of the standards of the JIS (Japanese Industrial Standards Committee) after conditioning the prepared optical film for 2 hours or more at a temperature of 23 ° C. and a relative humidity of 55%. It is a value measured according to the pencil hardness evaluation method defined in JIS K5400 using the test pencil defined in S6006.

<Haze>
The haze value of the optical film of the present embodiment is preferably 1% or less for a clear optical film. By setting the haze value to 1% or less, sufficient brightness and high contrast can be obtained when used outdoors such as a large-sized liquid crystal display device or digital signage. The haze value can be measured according to JIS K7105 and JIS K7136.

  Moreover, the optical film of this embodiment may have anti-glare properties. Anti-glare is a function that blurs the outline of the image and external light reflected by the hard coat layer of the optical film. It reduces the visibility of the reflected image and reflects when the optical film is used for a liquid crystal display or the like. It is to avoid the reflection of the image. In the optical film having antiglare properties, the total haze value is preferably 3% to 40%. The surface haze value (haze due to film surface scattering) is preferably 3 to 40%, and the internal haze value (haze due to internal scattering) is preferably 35% or less.

[Film base]
The film base is preferably a cellulose ester film such as a triacetyl cellulose film, a cellulose acetate propionate film, a cellulose diacetate film, or a cellulose acetate butyrate film because it is easy to produce. Other films include polyester films such as polyethylene terephthalate and polyethylene naphthalate, polycarbonate films, polyarylate films, polysulfone (including polyethersulfone) films, polyethylene films, polypropylene films, cellophane, polyvinylidene chloride films, polyvinyl Alcohol film, ethylene vinyl alcohol film, syndiotactic polystyrene film, norbornene resin film, polymethylpentene film, polyether ketone film, polyether ketone imide film, polyamide film, fluororesin film, nylon film, cycloolefin polymer film , Polymethyl methacrylate film, acrylic film, etc. It can be used for the film substrate. You may use together the resin which comprises an above described film.

  The refractive index of the film substrate is preferably 1.30 to 1.70, and more preferably 1.40 to 1.65. The refractive index can be measured by the method of JIS K7142 using an Atpe refractometer 2T.

<Cellulose ester film>
In the case of cellulose triacetate, the cellulose ester film preferably has an average degree of acetylation (bound acetic acid amount) of 54.0 to 62.5%, more preferably an average degree of acetylation of 58.0. 62.5% cellulose triacetate film. When the average acetylation degree is small, the dimensional change is large, and the polarization degree of the polarizing plate is lowered. When the average acetylation degree is large, the solubility in a solvent is lowered, and the productivity is lowered.

  The film substrate preferably contains cellulose triacetate A having an acetyl group substitution degree of 2.80 to 2.95 and a number average molecular weight (Mn) of 125000 or more and less than 155000. Cellulose triacetate A preferably has a weight average molecular weight (Mw) of 265,000 or more and less than 310,000 and Mw / Mn of 1.9 to 2.1.

  Moreover, from the point which pencil hardness improves, acetyl group substitution degree is 2.75-2.90, number average molecular weight (Mn) is 155000 or more and less than 180,000, Mw is 290000 or more and less than 360,000, Mw / Mn is 1. It is preferable to use cellulose triacetate B which is .8 to 2.0 in combination with cellulose triacetate A. When cellulose triacetate A and cellulose triacetate B are used in combination, it is preferable that the weight ratio is in the range of cellulose triacetate A: cellulose triacetate B = 100: 0 to 20:80.

Other than cellulose triacetate, when an acyl group having 2 to 4 carbon atoms is used as a substituent, the substitution degree of acetyl group is X, and the substitution degree of propionyl group or butyryl group is Y, the following formula (I) Cellulose esters that simultaneously satisfy (II) and (II) can be used.
Formula (I) 2.6 ≦ X + Y ≦ 3.0
Formula (II) 0 ≦ X ≦ 2.5
Among them, cellulose acetate propionate is preferable, and 1.9 ≦ X ≦ 2.5 and 0.1 ≦ Y ≦ 0.9 are particularly preferable. The degree of acyl group substitution can be measured according to ASTM D817-96, one of the standards formulated and issued by ASTM (American Society for Testing and Materials). Cellulose diacetate can also be preferably used.

The number average molecular weight (Mn) and molecular weight distribution (Mw) of the cellulose ester can be measured using high performance liquid chromatography. The measurement conditions are as follows.
Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (GL Science Co., Ltd.)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0 ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation)
A calibration curve with 13 samples from Mw = 100000 to 500 was used. The 13 samples are preferably used at approximately equal intervals.

<Ester compound>
The cellulose ester film preferably contains an ester compound from the viewpoint of excellent moisture resistance. As the ester compound, an ester compound having a structure obtained by reacting phthalic acid, adipic acid, at least one benzene monocarboxylic acid and at least one alkylene glycol having 2 to 12 carbon atoms is preferable.

  Examples of the benzene monocarboxylic acid component include benzoic acid, para-tert-butylbenzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethylbenzoic acid, ethylbenzoic acid, normal propylbenzoic acid, aminobenzoic acid, acetoxybenzoic acid. There exists an acid etc., and these can be used as a 1 type, or 2 or more types of mixture, respectively. Most preferred is benzoic acid.

  Examples of the alkylene glycol component having 2 to 12 carbon atoms include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,2-propanediol, 2-methyl 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2,2-diethyl-1, 3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3-propanediol (3,3-dimethylolheptane), 3-methyl-1,5-pentanediol 1 , 6-hexanediol, 2,2,4-trimethyl 1,3-pentanediol, 2-ethyl 1,3-hexanediol, -Methyl 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, etc. These glycols are used as one kind or a mixture of two or more kinds . 1,2-propylene glycol is particularly preferable.

  The ester compound may have an adipic acid residue and a phthalic acid residue as the final compound structure.

  The ester compound can be produced by mixing in the presence of an esterification catalyst as necessary, for example, within a temperature range of 180 to 250 ° C. for 10 to 25 hours, and performing an esterification reaction.

  Furthermore, an aromatic terminal ester compound can also be used as the ester compound. Although the exemplary compound of an aromatic terminal ester compound is shown below, it is not limited to these.

  Examples of ester compounds include sugar ester compounds. The sugar ester compound is a compound obtained by esterifying all or part of the OH group of a sugar such as the following monosaccharide, disaccharide, trisaccharide or oligosaccharide. As a more specific example, a general formula (4) The compound etc. which are represented by these can be mention | raise | lifted.

In the formula, R _{1 to} R ₈ represent a substituted or unsubstituted alkylcarbonyl group having 2 to 22 carbon atoms, or a substituted or unsubstituted arylcarbonyl group having 2 to 22 carbon atoms. R _{1 to} R ₈ may be the same or different.

  Although the compound shown by General formula (4) below is shown more specifically (as compound 4-1 to compound 4-23), it is not limited to these.

  In the ester compound, the number average molecular weight is preferably 300 to 2000, more preferably 400 to 1500. The acid value is preferably 0.08 to 0.50 mg KOH / g. The hydroxyl value is preferably 25 mgKOH / g or less, more preferably 15 mgKOH / g or less.

  The ester compound is preferably contained in the film base in an amount of 1 to 35% by mass, particularly 5 to 30% by mass. Within this range, there is no bleeding out and excellent transparency.

  The cellulose ester film may contain a thermoplastic acrylic resin and a cellulose ester resin.

  Acrylic resin also includes methacrylic resin. Although it does not restrict | limit especially as an acrylic resin, What consists of 50-99 mass% of methyl methacrylate units and 1-50 mass% of other monomer units copolymerizable with this is preferable. Other monomers that can be copolymerized include alkyl methacrylates having 2 to 18 carbon atoms, alkyl acrylates having 1 to 18 carbon atoms, acrylic acid, methacrylic acid, and the like. Unsaturated group-containing divalent carboxylic acids such as saturated acid, maleic acid, fumaric acid and itaconic acid, aromatic vinyl compounds such as styrene and α-methylstyrene, α, β-unsaturated nitriles such as acrylonitrile and methacrylonitrile, Maleic anhydride, maleimide, N-substituted maleimide, glutaric anhydride and the like can be mentioned. These can be used alone or in combination of two or more monomers.

  Among these, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, 2-ethylhexyl acrylate, and the like are preferable from the viewpoint of thermal decomposition resistance and fluidity of the copolymer. n-Butyl acrylate is particularly preferably used.

  Moreover, it is preferable that the weight average molecular weights (Mw) of an acrylic resin are 80000-500000, More preferably, it exists in the range of 110000-500000. The weight average molecular weight of the acrylic resin can be measured by gel permeation chromatography including the measurement conditions. Moreover, as a commercial item, Delpet 60N, 80N (Asahi Kasei Chemicals Co., Ltd. product), Dianal BR52, BR80, BR83, BR85, BR88 (Mitsubishi Rayon Co., Ltd. product), KT75 (Electrochemical Industry Co., Ltd. product) Etc. Two or more acrylic resins can be used in combination.

<Additives>
Acrylic particles may be contained for the purpose of improving the brittleness of the film substrate. Examples of commercially available acrylic particles include, for example, Metablen W-341 (C2) (manufactured by Mitsubishi Rayon Co., Ltd.), Chemisnow MR-2G (C3), MS-300X (C4) (manufactured by Soken Chemical Co., Ltd.). And the like.

  The acrylic fine particles are preferably contained in the range of 0.5% to 30% with respect to the total mass of the resin forming the film substrate.

(Fine particles)
The film substrate may contain fine particles other than acrylic fine particles. As fine particles other than acrylic fine particles, silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated silica from the viewpoint of slipperiness and storage stability. Inorganic fine particles such as calcium acid, aluminum silicate, magnesium silicate and calcium phosphate are preferred.

  Among these inorganic fine particles, silicon dioxide is preferable in terms of low turbidity. Silicon dioxide that has been subjected to a hydrophobization treatment is preferable in terms of achieving both slipperiness and haze. Of the four silanol groups, those in which two or more are replaced with hydrophobic substituents are preferred, and those in which three or more are substituted are more preferred. The hydrophobic substituent is preferably a methyl group. The primary particle size of silicon dioxide is preferably 20 nm or less, and more preferably 10 nm or less.

  Silicon dioxide fine particles are commercially available, for example, under the trade names Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (above Nippon Aerosil Co., Ltd.). it can. Zirconium oxide fine particles are commercially available, for example, under the trade names Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.) and can be used. Among these, Aerosil 200V and Aerosil R972V are particularly preferable because they have a large effect of reducing the friction coefficient while keeping the haze of the film substrate low, and Aerosil R812 is most preferably used. In a film base material, it is preferable that the dynamic friction coefficient of at least one surface is 0.2 to 1.0.

(Other additives)
In order to improve the fluidity and flexibility of the composition, a plasticizer can be added to the film substrate. Examples of the plasticizer include phthalic acid compounds, fatty acid compounds, trimellitic acid compounds, phosphoric acid compounds, acrylic polymers, and epoxy compounds.

  The acrylic polymer is preferably a homopolymer or copolymer of acrylic acid or methacrylic acid alkyl ester. Examples of the acrylate monomer include methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), butyl acrylate (n-, i-, s-, t-), pentyl acrylate ( n-, i-, s-), hexyl acrylate (n-, i-), heptyl acrylate (n-, i-), octyl acrylate (n-, i-), nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), acrylic acid (2-ethylhexyl), acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic Acid (3-hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), acrylic acid (2-methoxyethyl), acrylic acid 2-ethoxyethyl), etc., or the acrylic acid ester may include those obtained by changing the methacrylic acid ester. The acrylic polymer is a homopolymer or copolymer of the above-mentioned monomer, but it is preferable that the acrylic acid methyl ester monomer unit has 30% by mass or more, and the methacrylic acid methyl ester monomer unit has 40% by mass or more. preferable. In particular, a homopolymer of methyl acrylate or methyl methacrylate is preferred.

  These plasticizers can be selected or used in combination depending on the application. Moreover, it is preferable that the addition amount of a plasticizer is 0.5-30 mass parts with respect to 100 mass parts of film base materials.

  It is also preferable that the film substrate contains an ultraviolet absorber. Examples of the ultraviolet absorber used include benzotriazole, 2-hydroxybenzophenone, or salicylic acid phenyl ester. For example, 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (3 Triazoles such as 5-di-t-butyl-2-hydroxyphenyl) benzotriazole, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone And benzophenones. Here, among ultraviolet absorbers, ultraviolet absorbers having a molecular weight of 400 or more are less likely to volatilize at a high boiling point and are difficult to disperse even during high-temperature molding, so that the weather resistance is effectively improved with a relatively small amount of addition. be able to.

  Examples of the ultraviolet absorber having a molecular weight of 400 or more include 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole, 2,2-methylenebis [4- (1, 1,3,3-tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol], bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis ( Hindered amines such as 1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and 2- (3,5-di-t-butyl-4-hydroxybenzyl) -2-n-butylmalonic acid Bis (1,2,2,6,6-pentamethyl-4-piperidyl), 1- [2- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] ethyl L] -4- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] -2,2,6,6-tetramethylpiperidine and the like, hindered phenol and hindered amine A hybrid system having both structures can be mentioned, and these can be used alone or in combination of two or more. Among these, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole and 2,2-methylenebis [4- (1,1,3,3- Tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol] is particularly preferred.

  Furthermore, various antioxidants can also be added to the film substrate in order to improve the thermal decomposability and thermal colorability during molding. An antistatic agent can be added to impart antistatic performance to the film substrate.

  A flame retardant acrylic resin composition containing a phosphorus flame retardant may be used for the film substrate. Phosphorus flame retardants used here include red phosphorus, triaryl phosphate ester, diaryl phosphate ester, monoaryl phosphate ester, aryl phosphonate compound, aryl phosphine oxide compound, condensed aryl phosphate ester, halogenated alkyl phosphorus. Examples thereof include one or a mixture of two or more selected from acid esters, halogen-containing condensed phosphates, halogen-containing condensed phosphonates, halogen-containing phosphites, and the like.

  Specific examples include triphenyl phosphate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, phenylphosphonic acid, tris (β-chloroethyl) phosphate, tris (dichloropropyl). Examples thereof include phosphate and tris (tribromoneopentyl) phosphate.

  Since higher brightness is required for use in outdoor applications such as digital signage, the film base material is required to withstand use in a higher temperature environment. If the tension softening point of the film substrate is 105 ° C. to 145 ° C., it can be determined that the film has sufficient heat resistance, and is preferably controlled to 110 ° C. to 130 ° C.

  As a specific method of measuring the tension softening point, for example, using a Tensilon tester (ORIENTEC, RTC-1225A), the optical film is cut out at 120 mm (length) × 10 mm (width) and pulled with a tension of 10 N. However, the temperature can be continuously increased at a temperature increase rate of 30 ° C./min, and the temperature at 9 N can be measured three times, and the average value can be obtained.

  From the viewpoint of heat resistance, the film substrate preferably has a glass transition temperature (Tg) of 110 ° C. or higher. More preferably, it is 120 ° C. or higher. Especially preferably, it is 150 degreeC or more.

  In addition, the glass transition temperature here is the intermediate | middle calculated | required according to JISK7121 (1987), using the differential scanning calorimeter (DSC-7 type | mold by Perkin Elmer), measured with the temperature increase rate of 20 degree-C / min. Point glass transition temperature (Tmg).

  When the film substrate is used for a liquid crystal display device used particularly outdoors, the dimensional change rate (%) of the film substrate is preferably less than 0.5%, and further less than 0.3%. Is preferred.

  Moreover, in a film base material, it is preferable that the defect in a film surface diameter of 5 micrometers or more is 1 piece / 10cm square or less. More preferably, it is 0.5 piece / 10 cm square or less, more preferably 0.1 piece / 10 cm square or less. Here, the defect is a void in the film (foaming defect) generated due to the rapid evaporation of the solvent in the drying process of the solution casting, a foreign matter in the film forming stock solution, or a foreign matter mixed in the film forming. It refers to the part where the surface shape has changed, such as the foreign matter (foreign matter defect) in the film, and the transfer or scratching of a roll wound. The diameter of the defect indicates the diameter when the defect is circular, and when the defect is not circular, the range of the defect is determined by observing with a microscope according to the following method, and the maximum diameter (diameter of circumscribed circle) is determined.

  The range of the defect is the size of the shadow when the defect is observed with the transmitted light of the differential interference microscope when the defect is a bubble or a foreign object. When the defect is a change in the surface shape, such as transfer of a roll flaw or an abrasion, the size is confirmed by observing the defect with the reflected light of a differential interference microscope. In addition, when observing with reflected light, if the size of the defect is unclear, aluminum or platinum is deposited on the surface for observation.

  In order to obtain a high-quality film represented by such a defect frequency with high productivity, high-precision filtration of the polymer solution immediately before casting, increasing the cleanliness around the casting machine, It is effective to set the drying conditions after casting stepwise, and to dry efficiently while suppressing foaming.

  When the number of defects is greater than 1/10 cm square, for example, when the film is tensioned during processing in a later process, the film may break with the defects as a starting point, and productivity may decrease. Moreover, when the diameter of a defect becomes 5 micrometers or more, it can confirm visually by polarizing plate observation etc., and when used as an optical member, a bright spot may arise.

  Even when the defects cannot be visually confirmed, when the hard coat layer is formed on the film, the hard coat layer coating composition may not be applied uniformly, resulting in defects (coating defects).

  In addition, the film substrate preferably has a breaking elongation in at least one direction of 10% or more, more preferably 20% or more, in the measurement based on JIS K7127 (1999).

  The upper limit of the elongation at break is not particularly limited, but is practically about 250%. In order to increase the elongation at break, it is effective to suppress defects in the film caused by foreign matter and foaming.

  The thickness of the film substrate is preferably 10 μm or more. More preferably, it is 20 μm or more.

  Although the upper limit of the thickness of a film base material is not specifically limited, When forming into a film by a solution casting method, an upper limit is about 250 micrometers from viewpoints, such as applicability | paintability, foaming, and solvent drying. In addition, the thickness of a film base material can be suitably selected according to a use.

  Therefore, the thickness of the film substrate of the present embodiment is preferably 10 to 250 μm, and more preferably 20 to 100 μm. In addition, it is especially preferable that it is 10-40 micrometers from a viewpoint of thin film formation of an optical member.

  The film substrate preferably has a total light transmittance of 90% or more, more preferably 93% or more. Moreover, as a realistic upper limit, it is about 99%. In order to achieve excellent transparency expressed by such total light transmittance, it is necessary not to introduce additives and copolymerization components that absorb visible light, or to remove foreign substances in the polymer by high-precision filtration. It is effective to reduce the diffusion and absorption of light inside the film.

  The retardation of the film substrate is preferably such that the in-plane retardation Ro at a wavelength of 590 nm is from 0 to 50 nm and the retardation Rth in the thickness direction is from -10 to 50 nm. By configuring an optical film using a film base material having retardation in the range, interference fringes due to birefringence can be satisfactorily suppressed when the optical film is used for, for example, a constituent member for a touch panel.

The above Ro and Rth are values defined by the following formulas (I) and (II).
Formula (I) Ro = (nx−ny) × d
Formula (II) Rth = {(nx + ny) / 2−nz} × d
In the formula, nx is the refractive index in the slow axis direction in the plane of the film substrate, ny is the refractive index in the direction perpendicular to the slow axis in the plane of the film substrate, and nz is the thickness direction of the film substrate. And d represents the thickness (nm) of the film substrate. Said retardation can be calculated | required by measurement wavelength 590nm in 23 degreeC and 55% RH environment, for example using KOBRA-21ADH (Oji Scientific Instruments Co., Ltd.).

  Retardation can be adjusted by the types of ester compounds and plasticizers described above, the amount added, the film thickness of the film substrate, and the stretching conditions.

  Also, reduce the surface roughness of the film surface by reducing the surface roughness of the film contact part (cooling roll, calender roll, drum, belt, coating substrate in solution casting, transport roll, etc.) during film formation. It is also effective to reduce the diffusion and reflection of light on the film surface by reducing the refractive index of the acrylic resin.

(Film base film formation)
Next, although the example of the film forming method of a film base material is demonstrated, this invention is not limited to this.

  As a method for forming a film substrate, a production method such as an inflation method, a T-die method, a calendar method, a cutting method, a casting method, an emulsion method, a hot press method, or the like can be used. From the viewpoints of suppressing coloring, suppressing defects of foreign matter, and suppressing optical defects such as die lines, film formation by a casting method is preferable. Film formation by the casting method includes a solution casting method and a melt casting method.

(Organic solvent)
An organic solvent useful for forming a dope when a film substrate is produced by a solution casting method can be used without limitation as long as it dissolves a cellulose ester resin and other additives simultaneously.

  For example, as the chlorinated organic solvent, methylene chloride, as the non-chlorinated organic solvent, methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro- Examples include 2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, and nitroethane. Methylene chloride, methyl acetate, ethyl acetate and acetone can be preferably used.

  In addition to the organic solvent, the dope preferably contains 1 to 40% by mass of a linear or branched aliphatic alcohol having 1 to 4 carbon atoms. When the proportion of alcohol in the dope increases, the web gels, and peeling from the metal support becomes easy. When the proportion of alcohol is small, acrylic resin and cellulose ester resin in a non-chlorine organic solvent system are used. Dissolution is promoted.

  In particular, in a solvent containing methylene chloride and a linear or branched aliphatic alcohol having 1 to 4 carbon atoms, at least 15 to 45 mass in total of at least three kinds of acrylic resin, cellulose ester resin, and acrylic particles are used. It is preferable that the dope composition is dissolved in%.

  Examples of the linear or branched aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol. Of these, ethanol is preferable because the stability of the dope, the boiling point is relatively low, and the drying property is good.

(Solution casting method)
The film substrate can be produced by a solution casting method. In the solution casting method, a step of preparing a dope by dissolving a resin and an additive in a solvent, a step of casting the dope on a belt-like or drum-like metal support, and a step of drying the cast dope as a web The step of peeling the web from the metal support, the step of stretching or maintaining the width of the web, the step of further drying, and the step of winding up the finished film are performed.

  The concentration of the cellulose ester resin in the dope is preferably higher because the drying load after casting on the metal support can be reduced, but if the concentration of the cellulose ester resin is too high, the load during filtration increases. Thus, the filtration accuracy is deteriorated. As a density | concentration which makes these compatible, 10-35 mass% is preferable, More preferably, it is 15-25 mass%.

  The metal support in the casting (casting) step preferably has a mirror-finished surface, and a stainless steel belt or a drum whose surface is plated with a casting is preferably used as the metal support.

  The cast width can be 1 to 4 m. The surface temperature of the metal support in the casting step is set to −50 ° C. to a temperature at which the solvent boils and does not foam. A higher temperature is preferred because the web can be dried faster, but if it is too high, the web may foam or the flatness may deteriorate.

  It is preferable that the temperature of a metal support body is suitably determined in the range of 0-100 degreeC, and 5-30 degreeC is still more preferable. Alternatively, it is also a preferable method that the web is gelled by cooling and peeled from the metal support in a state containing a large amount of residual solvent.

  The method for controlling the temperature of the metal support is not particularly limited, and there are a method of blowing hot air or cold air, and a method of contacting hot water with the back side of the metal support. It is preferable to use warm water because heat transfer is performed efficiently, so that the time until the temperature of the metal support becomes constant is short.

  When using warm air, considering the temperature drop of the web due to the latent heat of vaporization of the solvent, while using warm air above the boiling point of the solvent, there is a case where wind at a temperature higher than the target temperature is used while preventing foaming. is there. In particular, it is preferable to efficiently dry by changing the temperature of the metal support and the temperature of the drying air during the period from casting to peeling.

In order for the cellulose ester-based film to exhibit good flatness, the residual solvent amount when peeling the web from the metal support is preferably 10 to 150% by mass. A preferable lower limit of the residual solvent amount is 20 to 40% by mass, and particularly preferably 20 to 30% by mass. The preferable upper limit of the residual solvent amount is 60 to 130% by mass, and particularly preferably 70 to 120% by mass. The residual solvent amount is defined by the following formula.
Residual solvent amount (% by mass) = {(MN) / N} × 100
Here, M is the mass of a sample taken at any time during or after production of the web or film, and N is the mass after heating M at 115 ° C. for 1 hour.

  Further, in the drying step of the cellulose ester film or the cellulose ester resin / acrylic resin film, it is preferable that the web is peeled off from the metal support and further dried to make the residual solvent amount 1% by mass or less, more preferably 0. 0.1 mass% or less, particularly preferably 0 to 0.01 mass% or less.

  In the stretching step, the web (film) can be sequentially or simultaneously stretched in the conveyance direction (MD direction; Machine Direction) and the width direction (TD direction; Transverse Direction) perpendicular thereto. The draw ratios in the biaxial directions perpendicular to each other are preferably in the range of 1.0 to 2.0 times in the MD direction and 1.07 to 2.0 times in the TD direction, respectively. It is preferable to carry out within a range of 1.0 to 1.5 times and 1.07 to 2.0 times in the TD direction. For example, a method in which peripheral speed differences are applied to a plurality of rolls and a roll peripheral speed difference is used to stretch in the MD direction, both ends of the web are fixed with clips and pins, and the distance between the clips and pins is increased in the traveling direction. And a method of stretching in the MD direction, a method of stretching in the transverse direction and stretching in the TD direction, a method of stretching in the MD / TD direction simultaneously and stretching in both the MD / TD directions, and the like.

  These width maintenance or width direction stretching in the film forming step is preferably performed by a tenter, and may be a pin tenter or a clip tenter. The film transport tension in the film forming process in the tenter and the like is preferably 120 N / m to 200 N / m, more preferably 140 N / m to 200 N / m, and most preferably 140 N / m to 160 N / m, depending on the temperature. preferable.

  The temperature at which the film is stretched is (Tg-30) to (Tg + 100) ° C, more preferably (Tg-20) to (Tg + 80) ° C, more preferably, when the glass transition temperature of the film substrate is Tg ° C. (Tg-5) to (Tg + 20) ° C.

  The glass transition temperature of the film substrate can be controlled by the material type constituting the film and the ratio of the constituting materials. The glass transition temperature during drying of the film substrate is preferably 110 ° C. or higher, more preferably 120 ° C. or higher. Moreover, it is preferable that the glass transition temperature of a film base material is 190 degrees C or less, and it is more preferable that it is 170 degrees C or less. At this time, the glass transition temperature of the film substrate can be determined by the method described in JIS K7121.

  It is preferable to set the temperature at which the film is stretched to 150 ° C. or more and the stretching ratio to 1.15 times or more because the surface is appropriately roughened. It is preferable to appropriately roughen the film surface because not only the slipperiness is improved but also the surface processability, particularly the adhesion of the hard coat layer is improved. The arithmetic average roughness Ra of the surface of the film substrate is preferably 2.0 nm to 4.0 nm, more preferably 2.5 nm to 3.5 nm.

  In the film drying process, a roll drying method (a method in which webs are alternately passed through a plurality of rolls arranged above and below) and a method in which the web is dried while being conveyed by a tenter are generally employed.

(Melt casting method)
The film substrate can also be formed by a melt casting method. The melt casting method refers to heating and melting a composition containing an additive such as a resin and a plasticizer to a temperature exhibiting fluidity, and then casting a melt containing a fluid cellulose ester. The melt casting method includes a method in which a film-forming material is heated to develop its fluidity and then extruded to form a film on a drum or an endless belt.

  More specifically, the heat melting molding method can be classified into a melt extrusion molding method, a press molding method, an inflation method, an injection molding method, a blow molding method, a stretch molding method, and the like. Among these molding methods, the melt extrusion molding method is preferable from the viewpoint of mechanical strength and surface accuracy. It is preferable that a plurality of raw materials used for melt extrusion are usually kneaded in advance and pelletized.

  Pelletization can be performed using a known method. For example, dry cellulose ester, plasticizer, and other additives are supplied to an extruder with a feeder, kneaded using a single or twin screw extruder, extruded into a strand from a die, water-cooled or air-cooled, and cut. Can be pelletized.

  The additive may be mixed before being supplied to the extruder, or may be supplied to the extruder by an individual feeder.

  A small amount of additives such as particles and antioxidants are preferably mixed in advance in order to mix uniformly.

  It is preferable that the extruder can be pelletized so that the shearing force is suppressed and the resin is not deteriorated (molecular weight reduction, coloring, gel formation, etc.) and processed at a temperature as low as possible. For example, in the case of a twin screw extruder, it is preferable to rotate in the same direction using a deep groove type screw. From the uniformity of kneading, the meshing type is preferable.

  A film is formed using the pellets obtained as described above. Of course, the raw material powder can be directly fed to the extruder by a feeder without being pelletized to form a film as it is.

  The melting temperature when extruding the pellets using a single-screw or twin-screw type extruder is about 200 to 300 ° C., filtered through a leaf disk type filter or the like to remove foreign matters, and then formed into a film from a T die. The film is cast, the film is nipped between the cooling roll and the elastic touch roll, and solidified on the cooling roll.

  When introducing the material from the supply hopper to the extruder, it is preferable to prevent oxidative decomposition or the like under vacuum, reduced pressure, or inert gas atmosphere. Moreover, it is preferable to carry out the extrusion flow rate of the pellets stably by introducing a gear pump or the like.

  Further, a stainless fiber sintered filter is preferably used as a filter used for removing foreign substances. A stainless steel fiber sintered filter is made by compressing a stainless steel fiber body after creating a complex intertwined state, and sintering and integrating the contact points. The density is changed according to the thickness of the fiber and the amount of compression, and filtration is performed. The accuracy can be adjusted.

  Additives such as plasticizers and particles may be mixed with the resin in advance, or may be kneaded in the middle of the extruder. In order to add uniformly, it is preferable to use a mixing apparatus such as a static mixer.

  The film temperature on the touch roll side when the film is nipped between the cooling roll and the elastic touch roll is preferably Tg or more and Tg + 110 ° C. or less of the film. The elastic touch roll used for such a purpose can use the well-known roll which has an elastic body on the surface. The elastic touch roll is also called a pinching rotator, and the touch roll disclosed in Japanese Patent No. 3194904, Japanese Patent No. 3422798, Japanese Patent Laid-Open No. 2002-36332, Japanese Patent Laid-Open No. 2002-36333, and the like can be preferably used. A commercially available elastic touch roll can also be used.

  When peeling the film from the cooling roll, it is preferable to control the tension to prevent deformation of the film.

  Moreover, it is preferable that the film obtained as described above is stretched by a stretching operation after passing through the step of contacting the cooling roll. As a method of stretching, a known roll stretching machine or tenter can be preferably used. The stretching temperature is usually preferably performed in the temperature range of Tg to Tg + 60 ° C. of the resin constituting the film.

  Before winding the formed film, slit the edge to the product width and cut it off, and apply knurling (embossing) on both ends to prevent sticking and scratching during winding. Also good. The knurling process can be performed by heating and pressing an embossing roll having an uneven pattern on the surface thereof. In addition, since the film is deform | transforming and cannot use as a product normally, the holding part of the clip of the both ends of a film is cut out and reused.

[Functional layer]
The optical film of the present embodiment can be provided with functional layers such as an antistatic layer, a backcoat layer, an antireflection layer, a slippery layer, an adhesive layer, and a barrier layer.

(Back coat layer)
In the optical film of the present embodiment, a back coat layer may be provided on the surface of the film base opposite to the side on which the hard coat layer is provided to prevent curling and sticking.

  Examples of inorganic compound particles added to the backcoat layer include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, tin oxide, indium oxide, Mention may be made of zinc oxide, ITO, hydrated calcium silicate, aluminum silicate, magnesium silicate and calcium phosphate.

  The amount of particles contained in the backcoat layer is preferably 0.1 to 50% by mass with respect to the binder. As the binder, a cellulose ester resin such as diacetylcellulose is preferable.

  Further, the increase in haze when the backcoat layer is provided is preferably 1.5% or less, more preferably 0.5% or less, and particularly preferably 0.1% or less.

(Antireflection layer)
The optical film of this embodiment can be used as an antireflection film having an external light antireflection function by coating an antireflection layer on the hard coat layer.

  The antireflection layer is preferably laminated in consideration of the refractive index, the film thickness, the number of layers, the layer order, and the like so that the reflectance is reduced by optical interference. The antireflection layer is a combination of a low refractive index layer having a lower refractive index than that of the film substrate that is the support, or a combination of a high refractive index layer and a low refractive index layer that have a higher refractive index than that of the film substrate that is the support. It is preferable to be configured. Particularly preferably, it is an antireflection layer composed of three or more refractive index layers, and three layers having different refractive indexes from the support side are divided into medium refractive index layers (high refractive index layers having a higher refractive index than the support). Are preferably laminated in the order of a layer having a lower refractive index) / a high refractive index layer / a low refractive index layer. Alternatively, an antireflection layer having a layer structure of four or more layers in which two or more high refractive index layers and two or more low refractive index layers are alternately laminated is also preferably used.

  As the layer structure of the antireflection film, the following structure is conceivable, but is not limited thereto.

Film substrate / hard coat layer / low refractive index layer Film substrate / hard coat layer / medium refractive index layer / low refractive index layer Film substrate / hard coat layer / medium refractive index layer / high refractive index layer / low refractive index Layer Film substrate / hard coat layer / high refractive index layer (conductive layer) / low refractive index layer Film substrate / hard coat layer / antiglare layer / low refractive index layer

<Low refractive index layer>
The low refractive index layer preferably contains silica-based fine particles, and the refractive index is preferably in the range of 1.30 to 1.45 at 23 ° C. and a measurement wavelength of 550 nm.

  The film thickness of the low refractive index layer is preferably 5 nm to 0.5 μm, more preferably 10 nm to 0.3 μm, and most preferably 30 nm to 0.2 μm.

  The composition for forming a low refractive index layer preferably contains at least one kind of particles having an outer shell layer and porous or hollow inside as silica-based fine particles. In particular, the particles having the outer shell layer and having a porous or hollow interior are preferably hollow silica-based fine particles.

  The composition for forming a low refractive index layer may contain an organosilicon compound represented by the following general formula (OSi-1) or a hydrolyzate thereof, or a polycondensate thereof.

General formula (OSi-1): Si (OR) ₄
In the formula, R represents an alkyl group having 1 to 4 carbon atoms. Specifically, tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane and the like are preferably used as the organosilicon compound represented by the general formula.

  The composition for forming a low refractive index layer is thermosetting and / or photocuring mainly comprising a fluorine-containing compound containing a fluorine atom in a range of 35 to 80% by mass and containing a crosslinkable or polymerizable functional group. You may contain the compound which has property. Specifically, it is a fluorine-containing polymer or a fluorine-containing sol-gel compound. As the fluorine-containing polymer, for example, a hydrofluorinated monomer in addition to a hydrolyzate or dehydration condensate of a perfluoroalkyl group-containing silane compound [for example, (heptadecafluoro-1,1,2,2-tetrahydrodecyl) triethoxysilane] Examples thereof include fluorine-containing copolymers having units and cross-linking reactive units as constituent units. In addition, you may add a solvent, a silane coupling agent, a hardening | curing agent, surfactant, etc. to the composition for low refractive index layer formation as needed.

<High refractive index layer>
The refractive index of the high refractive index layer is preferably in the range of 1.4 to 2.2 at 23 ° C. and a measurement wavelength of 550 nm. The thickness of the high refractive index layer is preferably 5 nm to 1 μm, more preferably 10 nm to 0.2 μm, and most preferably 30 nm to 0.1 μm. The means for adjusting the refractive index can be achieved by adding metal oxide fine particles or the like to the high refractive index layer. The refractive index of the metal oxide fine particles to be used is preferably 1.80 to 2.60, and more preferably 1.85 to 2.50.

  The kind of metal oxide fine particles is not particularly limited, and Ti, Zr, Sn, Sb, Cu, Fe, Mn, Pb, Cd, As, Cr, Hg, Zn, Al, Mg, Si, P and S A metal oxide having at least one element selected from can be used. These metal oxide fine particles may be doped with a trace amount of atoms such as Al, In, Sn, Sb, Nb, halogen elements, Ta, or a mixture thereof. Among them, at least one metal oxide fine particle selected from zirconium oxide, antimony oxide, tin oxide, zinc oxide, indium tin oxide (ITO), antimony-doped tin oxide (ATO), and zinc antimonate is used as a main component. It is particularly preferred. In particular, it is preferable to contain zinc antimonate particles.

  The average particle diameter of primary particles of these metal oxide fine particles is 10 nm to 200 nm, and particularly preferably 10 nm to 150 nm. The average particle diameter of the metal oxide fine particles can be measured from an electron micrograph obtained by a scanning electron microscope (SEM) or the like, but is measured by a particle size distribution meter using a dynamic light scattering method or a static light scattering method. May be. If the particle size is too small, aggregation tends to occur and the dispersibility deteriorates. If the particle size is too large, the haze is remarkably increased, which is not preferable. The shape of the metal oxide fine particles is preferably a rice grain shape, a spherical shape, a cubic shape, a spindle shape, a needle shape, or an indefinite shape.

  The metal oxide fine particles may be surface-treated with an organic compound. By modifying the surface of the metal oxide fine particles with an organic compound, the dispersion stability in an organic solvent is improved, the dispersion particle size can be easily controlled, and aggregation and sedimentation over time can be suppressed. . For this reason, the surface modification amount with a preferable organic compound is 0.1 mass%-5 mass% with respect to metal oxide fine particles, More preferably, it is 0.5 mass%-3 mass%. Examples of the organic compound used for the surface treatment include polyols, alkanolamines, stearic acid, silane coupling agents, and titanate coupling agents. Of these, silane coupling agents are preferred. Two or more kinds of surface treatments may be combined.

  The high refractive index layer may contain a π-conjugated conductive polymer. The π-conjugated conductive polymer can be used as long as it is an organic polymer having a main chain composed of a π-conjugated system. Examples thereof include polythiophenes, polypyrroles, polyanilines, polyphenylenes, polyacetylenes, polyphenylene vinylenes, polyacenes, polythiophene vinylenes, and copolymers thereof. From the viewpoint of ease of polymerization and stability, polythiophenes, polyanilines, and polyacetylenes are preferable.

  The π-conjugated conductive polymer exhibits sufficient conductivity and solubility in a binder resin even if it is not substituted, but in order to further improve conductivity and solubility, an alkyl group, a carboxy group, a sulfo group, an alkoxy group A functional group such as a hydroxy group or a cyano group may be introduced. The ratio of the polymer to the binder is preferably 10 to 400 parts by mass of the binder with respect to 100 parts by mass of the polymer, and particularly preferably 100 to 200 parts by mass of the binder with respect to 100 parts by mass of the polymer. is there.

The high refractive index layer may contain an ionic compound. Examples of the ionic compound include imidazolium, pyridium, alicyclic amine, aliphatic amine, and aliphatic phosphonium cations, inorganic ions such as BF ₄ ⁻ and PF ₆ ⁻ , CF ₃ SO _{2, and the like. ^{-, (CF 3 SO 2)}} 2 N -, CF 3 CO 2 - compound comprising a fluorine-based anions such like.

〔Polarizer〕
Next, a polarizing plate using the optical film of this embodiment will be described. The polarizing plate can be produced by a general method. The back side of the optical film of this embodiment is subjected to alkali saponification treatment, and the treated optical film is attached to at least one surface of a polarizing film prepared by immersing and stretching in an iodine solution using a completely saponified aqueous polyvinyl alcohol solution. It is preferable to match. In addition, the optical film of this embodiment may be bonded to the other surface of the polarizing film, and the above-described film substrate may be bonded.

  In addition, at a wavelength of 590 nm, an optical compensation film (retardation film) having an in-plane retardation Ro of 20 to 70 nm and a retardation Rt in the film thickness direction of 70 to 400 nm is used. The polarizing plate can be enlarged. Such a polarizing plate can be produced by, for example, a method described in JP-A-2002-71957. Further, it is preferable to use an optical compensation film having an optical anisotropic layer formed by aligning a liquid crystal compound such as a discotic liquid crystal. For example, the optically anisotropic layer can be formed by the method described in JP-A-2003-98348.

  Moreover, as a commercially available polarizing plate film base material preferably used, KC8UX2MW, KC4UX, KC5UX, KC4UY, KC8UY, KC12UR, KC4UEW, KC8UCR-3, KC8UCR-4, KC8UCR-5, KC4FR-2, KC4FR-2, KC8FR-2 , KC4UE (manufactured by Konica Minolta Opto Co., Ltd.) and the like.

  A polarizing film, which is a main component of a polarizing plate, is an element that allows only light having a polarization plane in a certain direction to pass through. A typical polarizing film currently known is a polyvinyl alcohol polarizing film, which includes a polyvinyl alcohol film dyed with iodine and a dichroic dye dyed. The deflection film is not limited to these.

  As the polarizing film, a polyvinyl alcohol aqueous solution is formed and dyed by uniaxially stretching or dyed, or uniaxially stretched after dyeing, and then preferably subjected to a durability treatment with a boron compound. The polarizing film preferably has a film thickness of 5 to 30 μm, preferably 8 to 15 μm.

  On the surface of the polarizing film, one side of the optical film of the present embodiment is bonded to form a polarizing plate. Preferably, they are bonded together with an aqueous adhesive mainly composed of completely saponified polyvinyl alcohol or the like.

(Adhesive layer)
The pressure-sensitive adhesive layer used on one side of the film base material to be bonded to the substrate of the liquid crystal cell is preferably optically transparent and exhibits moderate viscoelasticity and pressure-sensitive adhesive properties.

  Specifically, as the adhesive layer, for example, an acrylic copolymer, epoxy resin, polyurethane, silicone polymer, polyether, butyral resin, polyamide resin, polyvinyl alcohol resin, synthetic rubber, or other adhesive or adhesive A polymer such as an agent can be used. Using these materials, a pressure-sensitive adhesive layer can be formed by forming a film by a drying method, a chemical curing method, a thermal curing method, a thermal melting method, a photocuring method, or the like and curing the film. Among these, acrylic copolymers are most easily controlled for adhesive properties and are excellent in transparency, weather resistance, durability, and the like, and can be preferably used.

<Liquid crystal display device>
By incorporating a polarizing plate produced using the optical film of the present embodiment into a display device, various image display devices with excellent visibility can be produced.

  The optical film of this embodiment is incorporated in a polarizing plate, and is a reflective type, transmissive type, transflective type liquid crystal display device or TN type, STN type, OCB type, HAN type, VA type (PVA type, MVA type), IPS. It is preferably used for liquid crystal display devices of various driving systems such as a type and an OCB type.

  Moreover, the optical film of this embodiment can also be used for the member for touch panels of a liquid crystal display device with a touch panel. In this case, visibility and durability against pen input (scratches due to sliding, etc.) can be improved.

<Example>
Hereinafter, specific examples of the present invention will be described as examples, but the present invention is not limited to these examples.

Example 1
FIG. 4 is a cross-sectional view along the width direction showing a schematic configuration of the optical film F of Example 1. In addition, since the optical film F is a layer structure symmetrical with respect to a cross section perpendicular to the width direction passing through the center in the width direction, the first region R1 and the second region of the optical film F are shown in FIG. Of the region R2, only the first region R1 is shown, and the second region R2 is not shown (the same applies to the sectional views appearing below).

In Example 1, a triacetyl cellulose film (TAC) was used as the film substrate 1, and a pentaerythritol diacrylate resin was used as the cured film material. Then, in the width direction of the film substrate 1, a cured film material is applied from the first region R1 to the second region R2, and cured by irradiation with ultraviolet rays to form a cured film 2 having an elastic modulus of 4.5 GPa. did. In addition, the irradiation conditions of the ultraviolet rays at this time were an illuminance of 100 mW / cm ² and an irradiation amount of 300 mJ / cm ² . Thereafter, the optical film F is knurled using an embossing roll to form the knurling portion 3 on the cured film 2 and the knurling portion 4 is formed on the film substrate 1 to produce the optical film F. did.

  Here, A is the position of the end of the film substrate 1 in the width direction. A position 50 mm from the position A on the inner side in the width direction (opposite the end A) is defined as D. In this case, the first region R1 and the second region R2 are regions between A and D (50 mm width). Moreover, in each of 1st area | region R1 and 2nd area | region R2, the cured film 2 shall be formed from the position B1 to the position B2 in the width direction on the film base material 1, and the whole knurling part (knurling) The part 3 + the knurling part 4) is formed from the position C1 to the position C2 in the width direction. In addition, position B1 * C1 shall be located in the edge part A side rather than position B2 * C2. Unless otherwise specified, it is assumed that the position C1 coincides with the position A, and the position B2 coincides with the position D.

  In Example 1, in the first region R1 and the second region R2, the formation range of the cured film 2 is 45 mm between B1 and B2 (90% between A and D), and the entire knurling portion (the knurling portion) The formation range of 3+ knurling part 4) was 15 mm between C1 and C2. That is, in the first region R1 and the second region R2, the formation range of the knurling part 4 on the film substrate 1 is 5 mm between A (C1) -B1, and the knurling part 3 on the cured film 2 The formation range was 10 mm between B1 and C2.

Further, the height t of the knurling part 3 was 10 μm, and the number of the convex parts 3a of the knurling part 3 was 70 / cm ² . The height t of the knurling part 3 is measured by a contact-type film thickness meter TOF-6R (Yamabun Electric Co., Ltd.), and the number of convex parts 3a is measured by a microscope VHX-2000 (Keyence Co., Ltd.). Went by. Moreover, the thickness of the used film base material 1 was 30 micrometers.

(Example 2)
In Example 2, in the first region R1 and the second region R2, the formation range (between C1 and C2) of the entire knurling portion from the film end (between the knurling portion 3 and the knurling portion 4) is 8 mm, and the cured film 2 An optical film F was produced in the same manner as in Example 1 except that the formation range of the knurling part 3 (between B1 and C2) was 3 mm.

Example 3
In Example 3, an optical film F was produced in the same manner as in Example 1 except that the height t of the knurling part 3 was 1 μm.

Example 4
In Example 4, an optical film F was produced in the same manner as in Example 1 except that the height t of the knurling part 3 was 25 μm.

(Example 5)
In Example 5, an optical film F was produced in the same manner as in Example 1 except that the number of convex portions 3a of the knurling portion 3 was 10 / cm ² .

(Example 6)
In Example 6, an optical film F was produced in the same manner as in Example 1 except that the number of convex portions 3a of the knurling portion 3 was 140 pieces / cm ² .

(Example 7)
In Example 7, an optical film F was produced in the same manner as in Example 1 except that the film base 1 used had a thickness of 10 μm.

(Example 8)
In Example 8, an optical film F was produced in the same manner as in Example 1 except that the film substrate 1 used had a thickness of 40 μm.

Example 9
In Example 9, the irradiation conditions of ultraviolet rays were set to an illuminance of 80 mW / cm ² , an irradiation amount of 100 mJ / cm ² , and the cured film material was irradiated with ultraviolet rays, whereby the elastic modulus of the cured film 2 was set to 4.0 GPa. In the same manner as in Example 1, an optical film F was produced.

(Example 10)
FIG. 5 is a cross-sectional view along the width direction showing a schematic configuration of the optical film F of Example 10. In Example 10, in the first region R1 and the second region R2, the formation range of the cured film 2 (between B1 and B2) is 10 mm (20% between A and D), and the entire knurling part (knurling part 3+) The formation range (between C1 and C2) of the knurling part 4) was 50 mm. That is, on the cured film 2 in the first region R1 and the second region R2, the formation range of the knurling part 3 (between B1 and C2) was set to 10 mm. Otherwise, the optical film F was produced in the same manner as in Example 1.

(Example 11)
6 is a cross-sectional view along the width direction showing a schematic configuration of the optical film F of Example 11. FIG. In Example 11, in the first region R1 and the second region R2, the formation range (between B1 and B2) of the cured film 2 is 50 mm (100% between A and D), and the knurling on the cured film 2 is performed. The formation range of the part 3 (between B1 and C2) was 15 mm. That is, in Example 11, since the position B1 of the end portion of the cured film 2 coincides with the position A (C1) of the end portions of the first region R1 and the second region R2, the cured film is obtained by knurling. The knurling part 3 is formed only on 2 (the knurling part 4 is not formed on the film base 1). Otherwise, the optical film F was produced in the same manner as in Example 1.

(Example 12)
FIG. 7 is a cross-sectional view along the width direction showing a schematic configuration of the optical film F of Example 12. In Example 12, the cured film 2 is formed only in the first region R1 and the second region R2, and the position B2 of the end portion of the cured film 2 is set to the end in the width direction from the position D (position A side). ).

  More specifically, in the first region R1 and the second region R2, the formation range of the cured film 2 (between B1 and B2) is a range from the end position A to 20 mm in the width direction (between A and D). 40%), and the formation range of the knurling part 3 (between B1 and C2) was 15 mm. That is, in Example 12, the position B1 of the end portion of the cured film 2 coincides with the position A (C1) of the end portions of the first region R1 and the second region R2, and thus the cured film is obtained by knurling. The knurling part 3 is formed only on 2 (the knurling part 4 is not formed on the film base 1). Otherwise, the optical film F was produced in the same manner as in Example 1.

(Example 13)
FIG. 8 is a cross-sectional view along the width direction showing a schematic configuration of the optical film F of Example 13. In Example 13, similarly to Example 12, the cured film 2 is formed only in the first region R1 and the second region R2, and the position B2 at the end of the cured film 2 is wider than the position D. It is shifted toward the direction end (position A side).

  More specifically, in the first region R1 and the second region R2, the formation range of the cured film 2 is changed from the position A of the end portion to the inner side in the width direction from the position B1 of 10 mm to the inner side in the width direction from the position A. The range of 30 mm (60% between A and D) up to the position B2 of 40 mm was set, and the formation range (between C1 and C2) of the knurling part (knurling part 3 + knurling part 4) was 20 mm. In this case, on the cured film 2 in the first region R1 and the second region R2, the formation range of the knurling part 3 (between B1 and C2) is 10 mm. Otherwise, the optical film F was produced in the same manner as in Example 1.

(Example 14)
In Example 14, in 1st area | region R1 and 2nd area | region R2, the formation range (between C1-C2) of the knurling part (knurling part 3 + knurling part 4) from a film edge part shall be 10 mm, and cured film 2 An optical film F was produced in the same manner as in Example 1 except that the formation range of the knurling part 3 (between B1 and C2) was 5 mm.

(Example 15)
In Example 15, an optical film F was produced in the same manner as in Example 1 except that the height t of the knurling part 3 was 0.5 μm.

(Example 16)
In Example 16, an optical film F was produced in the same manner as in Example 1 except that the height t of the knurling part 3 was 30 μm.

(Example 17)
In Example 17, an optical film F was produced in the same manner as in Example 1 except that the number of convex portions 3a of the knurling portion 3 was 5 / cm ² .

(Example 18)
In Example 18, an optical film F was produced in the same manner as in Example 1 except that the number of convex portions 3a of the knurling portion 3 was 150 pieces / cm ² .

(Example 19)
In Example 19, except that the ultraviolet irradiation conditions were an illuminance of 50 mW / cm ² and an irradiation amount of 50 mJ / cm ² , and the cured film material was irradiated with ultraviolet rays, whereby the elastic modulus of the cured film 2 was 3.5 GPa. In the same manner as in Example 1, an optical film F was produced.

(Comparative Example 1)
In Comparative Example 1, in the first region R1 and the second region R2, the formation range (between C1 and C2) of the knurling part (knurling part 3 + knurling part 4) from the film end is 7 mm, An optical film F was produced in the same manner as in Example 1 except that the formation range of the knurling part 3 (between B1 and C2) was 2 mm.

(Comparative Example 2)
FIG. 9 is a cross-sectional view along the width direction showing a schematic configuration of the optical film F of Comparative Example 2. In Comparative Example 2, in the first region R1 and the second region R2, the formation range of the cured film 2 (between B1 and B2) is 5 mm (10% between A and D), and the knurling part (knurling part 3 + knurling) The formation range of part 4) (between C1 and C2) was 45 mm. That is, in Comparative Example 2, the knurling part 4 was formed only on the film substrate 1 in the first region R1 and the second region R2, and the knurling part 3 was not formed on the cured film 2. Otherwise, the optical film F was produced in the same manner as in Example 1.

<Evaluation>
The optical films F produced in Examples 1 to 19 and Comparative Examples 1 and 2 described above are wound up, and evaluations about winding deviation in the core direction, gauge band (attached, blocking), winding shape, and film breakage are performed. The results are shown in Table 1. Examples 11 and 12 are merely reference examples of the present invention and do not belong to the present invention.

Here, the evaluation standard of winding deviation is as follows.
(Double-circle): Winding deviation does not generate | occur | produce at all and is favorable.
○: A slight amount of winding deviation occurred, but there was no problem.
(Triangle | delta): Although winding deviation has generate | occur | produced further, it is a level which is satisfactory practically.
X: Winding deviation has occurred to some extent and is defective.

The evaluation criteria for the gauge band are as follows.
A: Gauge band is not generated at all and is good.
○: Gauge band is generated a little, but it is a level with no problem.
(Triangle | delta): Although the gauge band has further generate | occur | produced, it is a level which is satisfactory practically.
X: The gauge band has a problem to some extent and is defective.

The evaluation criteria for the rolled form are as follows.
A: The roll is not deformed and the winding shape is good.
○: The roll is slightly warped, but at a level with no problem.
(Triangle | delta): Although the curvature further generate | occur | produced in the roll, it is a level which is satisfactory practically.
X: The problem of the warp of the roll has occurred to some extent and is defective.

The evaluation criteria for film breakage are as follows.
A: The film is not broken at all and is good.
○: Although the film is slightly broken, it is a level with no problem.
(Triangle | delta): Although the fracture | rupture of the film has generate | occur | produced further, it is a level which is satisfactory practically.
X: The film breaks to some extent and is defective.

  From the result of Table 1, in Examples 1-19, the knurling part 3 on the cured film 2 is formed 3 mm or more in the width direction, and about the winding deviation and the gauge band, it is good (、), or no problem level (○) or a level (△) where there is no problem in actual use. On the other hand, in Comparative Examples 1 and 2, the knurling portion 3 on the cured film 2 is less than 3 mm in the width direction, and both winding deviation and a gauge band are generated, resulting in a defect (x). Therefore, it can be said that by forming the knurling part 3 on the cured film 2 in the width direction over 3 mm or more, winding deviation and a gauge band can be suppressed.

  Further, in Example 15, even when the knurling part 3 is formed on the cured film 2 over 3 mm in the width direction, the winding deviation and the gauge band are further generated as compared with Example 1. This is presumably because the knurling part 3 cannot sufficiently suppress the winding deviation and the gauge band because the height of the knurling part 3 is as small as 0.5 μm.

  In Example 16, the wound roll was deformed, and the wound form was inferior to Example 1. This is presumably because the height of the knurling part 3 is as large as 30 μm, so that the convex part 3a easily falls down in the width direction at the time of winding, resulting in further warping of the wound roll.

  On the other hand, in Examples 1-14, the height of the knurling part 3 is in the range of 1 to 25 μm, and any of the winding deviation, gauge band, and winding shape is good (◎), or a level with no problem ( ○). Therefore, it can be said that the height of the knurling part 3 is desirably 1 to 25 μm in order to suppress the roll deviation and blocking and suppress the deformation of the roll to improve the winding shape.

Further, in Example 17, even when the knurling part 3 is formed on the cured film 2 over 3 mm in the width direction, the winding deviation and the gauge band are further generated as compared with Example 1. This is because the number of the convex portions 3a of the knurling portion 3 is 5 / cm ² and the number of the convex portions 3a is too small, so that the function of suppressing winding deviation and blocking by the knurling portion 3 can be efficiently exhibited. It is thought that it is not possible.

Further, in Example 18, the film was further broken during winding as compared with Example 1. This causes a great damage to the film substrate 1 when the knurling process is performed so that the number of the convex portions 3a of the knurling portion 3 is 150 pieces / cm ² , thereby causing the film in the width direction of the film. This is thought to be due to a decrease in strength.

On the other hand, in Examples 1 to 14, the number of convex portions 3a of the knurling portion 3 is 10 to 140 pieces / cm ² , and any of winding deviation, gauge band, and film breakage is good (（), There is no problem level (○). Therefore, it can be said that the number of convex portions 3a of the knurling portion 3 is desirably 10 to 140 pieces / cm ² in order to suppress winding slip, blocking, and film breakage.

  In Example 19, even when the knurling part 3 is formed on the cured film 2 over 3 mm in the width direction, winding deviation and a gauge band are further generated as compared with Example 1. This is because the cured film 2 has a low elastic modulus of 3.5 GPa, so that the desired hardness cannot be imparted to the knurling portion 3 formed on the surface of the cured film 2, and further winding deviation and gauge bands are generated. It is thought that it was because.

  On the other hand, in Examples 1-14, the elasticity modulus of the cured film 2 is 4.0 GPa or more, and neither winding deviation nor a gauge band is observed. This is presumably because the knurling part 3 is formed on the surface of the cured film 2 so that the knurling part 3 surely exhibits a function of suppressing the occurrence of winding deviation and gauge bands. Therefore, it can be said that the elastic modulus of the cured film 2 is preferably 4.0 GPa or more in order to reliably exhibit the function of the knurling portion 3 that suppresses winding deviation and the like.

  The present invention can be used for various functional films such as a polarizing plate protective film, a retardation film, and a viewing angle widening film used in a liquid crystal display device, for example.

DESCRIPTION OF SYMBOLS 1 Film base material 2 Cured film 3 Knurling part F Optical film R1 1st area | region R2 2nd area | region

Claims (4)

An optical film in which a cured film is formed on a film substrate having a thickness of 10 to 40 μm,
When each region from the both ends in the width direction of the film base to 50 mm is a first region and a second region,
The cured film covers a range of 20 to 100% in the width direction in the first region and a range of 20 to 100% in the width direction in the second region on the film substrate. Is formed,
An uneven knurling portion is formed on the surface of the cured film in each of the first region and the second region by knurling after the cured film is formed,
The knurling part is formed only in the range of the first region and the second region on the surface of the cured film, and is formed from each end of the cured film over 3 mm in the width direction. Has been
The cured film covers a range of 20 to 90% in the width direction in the first region and a range of 20 to 90% in the width direction in the second region on the film substrate. Is formed,
The knurling portion includes a surface of the cured film between each of the first region and the second region, and an end portion of the film base and an end portion of the cured film in the width direction. An optical film formed on both surfaces of the film substrate .   The optical film according to claim 1, wherein a height of the knurling portion is 1 to 25 μm. 3. The optical film according to claim 1, wherein the number of convex portions of the knurling portion is 10 to 140 per 1 cm ² .   The optical film according to claim 1, wherein the cured film has an elastic modulus of 4.0 GPa or more.

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