JP5888410B2 - Method for producing hard coat film - Google Patents

Description

  The present invention relates to a method for producing a hard coat film in which a hard coat layer is applied to a thin film optical film.

  Since the surface of the display device is easily damaged by direct hand touching or contact with an object, a hard coat film having a hard coat layer for preventing damage is usually attached to the surface of the display device. In particular, in a liquid crystal display device, the above-mentioned hard coat film is stuck on the surface of a polarizing film (polarizer) of a polarizing plate on the light emitting side, thereby preventing damage and reducing the thickness of the entire device.

  An example of such a hard coat film is disclosed in Patent Document 1. In the example of Patent Document 1, a hard coat film is produced by forming a hard coat layer having a thickness of 20 μm on one side of a film substrate having a thickness of 80 μm.

  By the way, with the recent demand for further thinning of the liquid crystal display device, an optical film (for example, a thin film optical film having a film thickness of 15 to 30 μm) made thinner than the film substrate used for producing the hard coat film of Patent Document 1. When a hard coat film formed by applying a hard coat layer on this surface was attached to a polarizing film to produce a liquid crystal display device, it was found that display defects appeared.

  As a result of the investigation, it was found that the display defect was caused by a scratch on the thin film optical film serving as a base of the hard coat layer of the hard coat film. That is, in a hard coat film applied to a polarizing plate of a liquid crystal display device, a hard coat layer is formed on one surface of a thin film optical film, and an adhesive for adhesion to a polarizing film is applied on the other surface. The At this time, in the thin film optical film, when the hard coat layer is scratched on the application side surface, when the hard coat layer is cured and shrunk by ultraviolet irradiation or the like, there are a scratched portion and a non-scratched portion. Curing shrinkage unevenness occurs. Conversely, if the thin film optical film is scratched on the surface on which the adhesive is applied, uneven coating of the adhesive occurs between the part where the scratch is generated and the part where the scratch is not generated, and this uneven coating causes poor adhesion. cause. In this way, the scratches on the thin film optical film cause unevenness in curing and shrinkage of the hard coat layer and unevenness in the application of the adhesive.

  Here, the scratches on the thin film optical film described above are fine scratches that exist at a level that cannot be detected by the evaluation of the film surface of the optical film, and occur in a biased manner either inside or outside the film. In addition, since it occurs periodically in the longitudinal direction during film formation, it is formed by transferring a scratch on a support (for example, a belt) in a film forming process by a solution casting method (solution film forming method). It is presumed that In particular, when a thin film optical film having a film thickness of 30 μm or less is formed by the solution casting method, the solvent easily evaporates on the belt, and the solvent ratio (residual solvent amount) when peeling from the belt is extremely low. It is considered that scratches transferred from the belt are less likely to be alleviated due to drying shrinkage of the film in the subsequent drying process.

  In order to suppress the above-mentioned display defects due to uneven curing shrinkage of the hard coat layer and uneven application of the adhesive, for example, scratches that cause the uneven curing shrinkage and uneven application of the adhesive are formed on both surfaces of the thin film optical film. You just don't have to. However, when a thin film optical film having a thin film thickness is formed by the solution casting method, the scratch transferred from the support remains on the surface of the support when the thin film optical film is cast as described above. It is impossible to prevent scratches from forming on both sides of the film.

  Therefore, in order to suppress display defects in the liquid crystal display device, even if the scratch transferred from the support remains on one side of the thin film optical film constituting the hard coat film, uneven curing and adhesion of the hard coat layer It is necessary to devise a technique that suppresses both uneven application of the agent. At this time, from the viewpoint of suppressing a decrease in the production efficiency of the hard coat film, it is also necessary to easily determine the surface on which the hard coat layer should be applied in the thin film optical film and to apply the hard coat layer to the thin film optical film. . Moreover, when a plasticizer is contained in the thin film optical film, it is necessary to suppress bleed-out (spout) of the plasticizer.

JP-A-2006-212549 (see paragraphs [0068], [0069], FIG. 1, etc.)

  In view of the above circumstances, the object of the present invention is to cure and shrink the hard coat layer while suppressing the bleed-out of the plasticizer even when the scratch on the support is transferred to the surface of the support in the thin film optical film at the time of casting. A method of manufacturing a hard coat film that can suppress both unevenness and uneven application of an adhesive, and can easily determine a surface on which a hard coat layer is to be applied in a thin film optical film and suppress a decrease in production efficiency. It is to provide.

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

  1. The film is formed by a solution casting method, contains 1 to 20% by weight of a plasticizer having a characteristic of being unevenly distributed on the support side during casting, and contains silica fine particles as a matting agent. A method for producing a hard coat film, comprising: applying a hard coat layer to a surface of the thin film optical film having a thickness of 30 μm or less on the side where the concentration of the silica fine particles is larger than the average concentration relative to the entire thin film optical film.

  2. 2. The method for producing a hard coat film according to 1 above, wherein the plasticizer is a phosphoric acid plasticizer.

  3. 3. The method for producing a hard coat film according to 1 or 2, wherein a thickness of the hard coat layer is 0.5 μm or more and 10 μm or less.

4). When the plasticizer is the first plasticizer,
The thin film optical film contains 1% by weight or more of a second plasticizer different from the first plasticizer,
4. The method for producing a hard coat film according to any one of 1 to 3, wherein the total amount of the first plasticizer and the second plasticizer in the thin film optical film is 20% by weight or less.

  5. 5. The method for producing a hard coat film as described in 4 above, wherein the second plasticizer is a phthalic acid-based or polyhydric alcohol ester-based plasticizer.

  According to said manufacturing method, a hard-coat layer is apply | coated to the surface by which the density | concentration of a silica particle is larger than an average density | concentration in the thin film optical film whose film thickness is 15 micrometers or more and 30 micrometers or less. The reason why the concentration of the silica fine particles is increased is that evaporation of the solvent occurs on the support during the production of the thin film optical film by the solution casting method. Therefore, in the thin film optical film, the surface on the side where the silica fine particle concentration is high is the surface on the opposite side to the support during casting. Since the hard coat layer is applied to this surface, the hard coat layer is not affected by the scratches on the support during film formation. Thereby, the hardening shrinkage nonuniformity of a hard-coat layer can be suppressed. Moreover, since the silica fine particles are not dissolved in the solvent, the surface of the thin film optical film on the side where the concentration of the silica fine particles is large (the surface opposite to the support during casting) can be optically discriminated. This makes it easy and does not require a long time to determine the coated surface of the hard coat layer. As a result, it can suppress that the production efficiency of a hard coat film falls.

  When a hard coat film (thin film optical film with a hard coat layer) is bonded to a member whose surface is to be protected (for example, a polarizing film in a liquid crystal display device), the adhesive used at the time of bonding is the hard coat layer in the hard coat film. It is applied to the opposite surface. This surface is a surface on the support side at the time of casting at the time of forming a thin film optical film, and if there is a scratch on the support, the scratch on the support is transferred to the surface to which the adhesive is applied. However, since the plasticizer is unevenly distributed on the surface side of the thin film optical film, the plasticizer imparts flexibility to the surface side. Thereby, since the damage | wound of an application surface becomes easy to be eased, it can suppress that the application | coating unevenness of an adhesive agent arises on an application surface, and can suppress adhesion failure.

  At this time, in the thin film optical film, even if the adhesive is applied to the surface on the side where the silica fine particle concentration is large and the hard coat layer is formed on the opposite surface (the side where the plasticizer is unevenly distributed), Uneven curing shrinkage cannot be suppressed. This is presumably because the hard shrink shrinkage unevenness of the hard coat layer is more affected by the scratch on the thin film optical film than the uneven application of the adhesive. However, in the above production method, the hard coat layer is formed on the surface on the side where the silica fine particle concentration is high (the surface on the side where the scratches on the support are not transferred). Uneven coating can be suppressed at the same time. Therefore, when the hard coat film manufactured by the above-described manufacturing method is applied to, for example, a polarizing plate of a liquid crystal display device (when the hard coat film is attached to the polarizing film of the polarizing plate), display defects are caused. Can be suppressed.

  Moreover, when the plasticizer contained in a thin film optical film is less than 1 weight%, the softness | flexibility of the application surface side of an adhesive agent will fall, and it will become difficult to suppress the application | coating unevenness of an adhesive agent. On the other hand, when the plasticizer is more than 20% by weight, bleeding out tends to occur. Therefore, when the thin film optical film contains 1 to 20% by weight of the plasticizer, it is possible to suppress the display defect due to uneven application of the adhesive while suppressing bleeding out.

It is sectional drawing which shows typically an example of the manufacturing apparatus of the cellulose-ester film as a thin film optical film of embodiment of this invention. It is sectional drawing which shows the schematic structure of the liquid crystal display device with which the hard coat film using the said cellulose-ester film is applied. It is explanatory drawing for demonstrating the A surface and B surface of the said cellulose-ester film. It is sectional drawing which shows typically the structure of the principal part of the polarizing plate of the said liquid crystal display device.

  Hereinafter, although the form for implementing this invention is demonstrated in detail, this invention is not limited to these.

<Hard coat film>
The hard coat film of this embodiment is obtained by forming a hard coat layer on one surface of a thin film optical film having a film thickness of 15 μm or more and 30 μm or less.

(Hard coat layer)
The hard coat layer according to the present embodiment preferably contains an actinic radiation curable resin from the viewpoint of excellent mechanical film strength (abrasion resistance, pencil hardness). That is, it is a layer mainly composed of a resin that is cured through a crosslinking reaction by irradiation with active rays (also called active energy rays) such as ultraviolet rays and electron beams. As the actinic radiation curable resin, a component containing a monomer having an ethylenically unsaturated double bond is preferably used, and an actinic radiation curable resin layer is formed by curing by irradiation with actinic radiation such as ultraviolet rays or electron beams. The Typical examples of the actinic radiation curable resin include an ultraviolet curable resin and an electron beam curable resin, but a resin curable by ultraviolet irradiation is particularly excellent in mechanical film strength (abrasion resistance, pencil hardness). It is preferable from the point. Examples of the ultraviolet curable resin include an ultraviolet curable acrylate resin, an ultraviolet curable urethane acrylate resin, an ultraviolet curable polyester acrylate resin, an ultraviolet curable epoxy acrylate resin, an ultraviolet curable polyol acrylate resin, and an ultraviolet curable resin. A curable epoxy resin or the like is preferably used, and an ultraviolet curable acrylate resin is particularly preferable.

  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 tri / tetraacrylate, ditrimethylolpropane tetraacrylate, ethoxylated pentaerythritol tetraacrylate, pentaerythritol tetraacrylate, glycerol triacrylate relay , Dipentaerythritol triacrylate, dipentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, tris (acryloyloxyethyl) isocyanurate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, 1,6-hexanediol di Methacrylate, neopentyl glycol dimethacrylate, trimethylolpropane trimethacrylate, trimethylolethane trimethacrylate, tetramethylolmethane trimethacrylate, tetramethylolmethane tetramethacrylate, pentaglycerol trimethacrylate, pentaerythritol dimethacrylate, pentaerythritol trimethacrylate, pen Pentaerythritol tetramethacrylate, glycerol trimethacrylate, dipentaerythritol trimethacrylate, dipentaerythritol tetramethacrylate, dipentaerythritol penta methacrylate, dipentaerythritol hexa methacrylate, etc. isocyanurate derivatives of the active energy ray-curable are preferably exemplified.

  It is preferable that the hard coat layer according to the present embodiment contains an active energy ray-curable isocyanurate derivative because the effect of suppressing slippage between films is enhanced. 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.

In the formula, L ² 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.

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

One of R _{1 to} R _{3 in} the above chemical structural formula is attached with functional groups represented by a, b, and c below, and at least one of R _{1 to} R ₃ is a functional group of 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.

  As these commercial products, Adekaoptomer N series, Sun Rad H-601, RC-750, RC-700, RC-600, RC-500, RC-611, RC-612 (manufactured by Sanyo Chemical Industries, Ltd.) , Aronix M-6100, M-8030, M-8060, Aronix M-215, Aronix M-315, Aronix M-313, Aronix M-327 (manufactured by Toagosei Co., Ltd.), NK-ester A-TMM-3L , NK-ester AD-TMP, NK-ester ATM-35E, NK ester A-DOG, NK ester A-IBD-2E, A-9300, A-9300-1CL (Shin Nakamura Chemical Co., Ltd.), PE- 3A (Kyoeisha Chemical) etc. are mentioned. You may mix the said active ray curable resin individually or in mixture of 2 or more types. The viscosity at 25 ° C. of the actinic radiation curable resin is preferably 20 mPa · s or more and 2000 mPa · s or less. By using such a low-viscosity resin, a protrusion shape described later can be easily obtained. Specifically, within the viscosity range of the resin, sufficient fluidity of the resin composition (composition comprising an active ray curable resin and an additive other than a solvent) can be easily obtained in the drying step, and a protrusion shape can be obtained. It is easy to be done.

  The viscosity of the actinic radiation curable resin can be measured using a B-type viscometer under the condition of 25 ° C. while stirring and mixing the resin with a disper. A monofunctional acrylate may also be used.

  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. Such monofunctional acrylates can be obtained from Nippon Kasei Kogyo Co., Ltd., Shin-Nakamura Chemical Co., Ltd., Osaka Organic Chemical Co., Ltd., etc.

  When using a monofunctional acrylate, it is preferable to contain polyfunctional acrylate: monofunctional acrylate = 80: 20 to 98: 2 in terms of the mass ratio of polyfunctional acrylate and monofunctional acrylate.

(Photopolymerization initiator)
The hard coat layer preferably contains a photopolymerization initiator to accelerate the curing of the actinic radiation curable resin. The amount of the photopolymerization initiator is preferably contained in a mass ratio of photopolymerization initiator: active ray curable resin = 20: 100 to 0.01: 100. Specific examples of the photopolymerization initiator include alkylphenone series, acetophenone, benzophenone, hydroxybenzophenone, Michler ketone, α-amyloxime ester, thioxanthone and the like, and derivatives thereof. In particular, it is not limited to these.

  A commercial item may be used for such a photoinitiator, for example, Irgacure 184, Irgacure 907, Irgacure 651, etc. by BASF Japan Ltd. are mentioned as a preferable illustration.

(Conductive agent)
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.

(Additive)
In the hard coat layer, a silicone surfactant, a fluorine surfactant, a difference in contact angle with water before and after alkali treatment (θ _Δ ) can be easily controlled within a predetermined range (for example, 5 to 55 °), An anionic surfactant and additives such as a fluorine-siloxane graft compound, a fluorine compound, and an acrylic copolymer may be contained. Moreover, you may contain the compound whose HLB value is 3-18. By adjusting the type and amount of these additives, water repellency can be controlled, and θ _Δ can be easily controlled within the above range. If _θΔ is within the above range, the hard coat layer exhibits hydrophilicity, and when wound into a roll, the slipping property between the hard coat films is suppressed, and an effect of preventing winding deviation is obtained.

Here, the difference (θ _Δ ) between the water contact angle before and after the alkali treatment is alkali-treated under the conditions shown below at least from the water contact angle (θ) of the hard coat layer before the alkali treatment of the hard coat film. This is a value obtained by subtracting the water contact angle (θa) of the hard coat layer after this to obtain the difference (θ _Δ ) in water contact angle before and after the alkali treatment. The alkali treatment condition is a condition in which the hard coat film is immersed in a 2.5 mol / L potassium hydroxide solution at a temperature of 50 ° C. for 120 seconds. As for the contact angle with water, the sample was allowed to stand for 24 hours in an atmosphere having a temperature of 23 ° C. and a relative humidity of 55%, and then contact angle meter (Kyowa Interface Science Co., Ltd.) in an atmosphere having a temperature of 23 ° C. and a relative humidity of 55%. Product, trade name DropMaster DM100), the contact angle of pure water 7 minutes after dropping 1 μl of pure water was measured 7 times, and the average value of 5 measured values excluding the maximum and minimum values of the measured values It was.

  Said HLB value is Hydrophile-Lipophile-Balance, hydrophilicity-lipophilicity-balance, and is a value indicating the hydrophilicity or lipophilicity of a compound. The smaller the HLB value, the higher the lipophilicity, and the higher the value, the higher the hydrophilicity. The HLB value can be obtained by the following calculation formula.

HLB = 7 + 11.7Log (Mw / Mo)
In the formula, Mw represents the molecular weight of the hydrophilic group, Mo represents the molecular weight of the lipophilic group, and Mw + Mo = M (molecular weight of the compound). Alternatively, according to the Griffin method, HLB value = 20 × total formula weight of hydrophilic part / molecular weight (J. Soc. Cosmetic Chem., 5 (1954), 294) and the like. Specific examples of the compound having an HLB value of 3 to 18 are listed below, but the present invention is not limited thereto. Figures in parentheses indicate HLB values.

  Made by Kao Corporation: Emulgen 102KG (6.3), Emulgen 103 (8.1), Emulgen 104P (9.6), Emulgen 105 (9.7), Emulgen 106 (10.5), Emulgen 108 (12. 1), Emulgen 109P (13.6), Emulgen 120 (15.3), Emulgen 123P (16.9), Emulgen 147 (16.3), Emulgen 210P (10.7), Emulgen 220 (14.2) , Emulgen 306P (9.4), Emulgen 320P (13.9), Emulgen 404 (8.8), Emulgen 408 (10.0), Emulgen 409PV (12.0), Emulgen 420 (13.6), Emulgen 430 (16.2), Emulgen 705 (10.5), Emulgen 707 (12.1), Emulgen 7 9 (13.3), Emulgen 1108 (13.5), Emulgen 1118S-70 (16.4), Emulgen 1135S-70 (17.9), Emulgen 2020G-HA (13.0), Emulgen 2025G (15. 7), Emulgen LS-106 (12.5), Emulgen LS-110 (13.4), Emulgen LS-114 (14.0), manufactured by Nissin Chemical Industry Co., Ltd .: Surfynol 104E (4), Surfynol 104H (4), Surfinol 104A (4), Surfinol 104BC (4), Surfinol 104DPM (4), Surfinol 104PA (4), Surfinol 104PG-50 (4), Surfinol 104S (4), Surfi Knoll 420 (4), Surfynol 440 (8), Surfynol 46 (13), Surfinol 485 (17), Surfinol SE (6), manufactured by Shin-Etsu Chemical Co., Ltd .: X-22-4272 (7), X-22-6266 (8), KF-351 (12), KF-352 (7), KF-353 (10), KF-354L (16), KF-355A (12), KF-615A (10), KF-945 (4), KF-618 (11), KF -6011 (12), KF-6015 (4), KF-6004 (5).

  Examples of the silicone surfactant include polyether-modified silicone, and the KF series manufactured by Shin-Etsu Chemical Co., Ltd. can be used. Examples of the acrylic copolymer include commercially available compounds such as BYK-350 and BYK-352 manufactured by BYK Japan. Examples of the fluorosurfactant include Megafac RS series manufactured by DIC Corporation, Megafac F-444 Megafac F-556, and the like. The fluorine-siloxane graft compound refers to a compound of a copolymer obtained by grafting polysiloxane and / or organopolysiloxane containing siloxane and / or organosiloxane alone on at least a fluorine-based resin. Such a fluorine-siloxane graft compound can be prepared by a method as described in Examples described later. Or as a commercial item, Fuji Chemical Industries Ltd. ZX-022H, ZX-007C, ZX-049, ZX-047-D etc. can be mentioned. Moreover, as a fluorine-type compound, Daikin Industries Ltd. OPTOOL DSX, OPTOOL DAC, etc. can be mentioned. These components are preferably added in the range of 0.005 parts by mass or more and 5 parts by mass or less with respect to the solid component in the hard coat composition.

(UV absorber)
A hard-coat layer may further contain the ultraviolet absorber demonstrated by the cellulose-ester film mentioned later. When the hard coat film is composed of two or more layers, it is preferable that the hard coat layer in contact with the cellulose ester film contains the ultraviolet absorber as the film configuration when containing the ultraviolet absorber.

  The content of the ultraviolet absorber is preferably a mass ratio, and the ultraviolet absorber: hard coat layer constituting resin = 0.01: 100 to 10: 100. When two or more layers are provided, the thickness of the hard coat layer in contact with the cellulose ester film 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-layer is to form 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.

(solvent)
The hard coat layer is a hard coat layer composition obtained by diluting the above-described components forming the hard coat layer with a solvent that swells or partially dissolves the cellulose ester film, and is applied onto the cellulose film by the following method, dried, It is preferable to provide it by curing.

  As the solvent, ketone (methyl ethyl ketone, acetone, etc.) and / or acetate ester (methyl acetate, ethyl acetate, butyl acetate, etc.), alcohol (ethanol, methanol), propylene glycol monomethyl ether, cyclohexanone, methyl isobutyl ketone, etc. are preferable. The coating amount of the hard coat layer is suitably in the range of 0.1 to 40 μm, preferably in the range of 0.5 to 30 μm, as the wet film thickness. The dry film thickness is in the range of 0.01 to 20 μm, preferably in the range of 0.5 to 10 μm. More preferably, it is the range of 0.5-5 micrometers.

  As a method for applying the hard coat layer, known methods such as a gravure coater, a dip coater, a reverse coater, a wire bar coater, a die coater, and an ink jet method can be used.

(Hard coat layer forming method)
After applying the hard coat layer composition, it may be dried and cured (irradiated with active rays (also referred to as UV curing treatment)), and if necessary, may be heat treated after UV curing. The heat treatment temperature after UV curing is preferably 80 ° C. or higher, more preferably 100 ° C. or higher, and particularly preferably 120 ° C. or higher. By performing the heat treatment after UV curing at such a high temperature, a hard coat layer having excellent film strength can be obtained.

  Drying is preferably performed at a high temperature of 90 ° C. or higher in the rate of decrease drying section. More preferably, the temperature in the decreasing rate drying section is 90 ° C. or higher and 125 ° C. or lower. By increasing the temperature of the rate-decreasing drying section, convection occurs in the coating resin during the formation of the hard coat layer, and as a result, irregular surface roughness tends to occur on the hard coat layer surface, and the arithmetic described later It is easy to control the average roughness Ra.

  In general, it is known that the drying process changes from a constant state to a gradually decreasing state when drying starts. The decreasing section is called the decreasing rate drying section. In the constant rate drying section, the amount of heat flowing in is all consumed for solvent evaporation on the coating film surface, and when the solvent on the coating film surface decreases, the evaporation surface moves from the surface to the inside and enters the decreasing rate drying section. Thereafter, the temperature of the coating film surface rises and approaches the hot air temperature, so that the temperature of the actinic radiation curable resin composition rises, the resin viscosity decreases, and the fluidity increases.

  As a light source for 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.

The irradiation conditions vary depending on individual lamps, irradiation of actinic rays is generally within the range of 50~1000mJ / cm ^2, preferably in the range of 50 to 300 mJ / cm ^2. In the UV curing treatment, oxygen removal (for example, replacement with an inert gas such as nitrogen purge) can be performed to prevent reaction inhibition by oxygen. The cured state of the surface can be controlled by adjusting the removal amount of the oxygen concentration. This makes it possible to control the presence state of the additive on the hard coat layer surface, and as a result, it is easy to control _θΔ within the above range. When irradiating actinic radiation, it is preferably performed while applying tension in the film transport direction, and more preferably while applying tension 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 roller, 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.

(Surface shape)
The arithmetic average roughness Ra of the hard coat layer is preferably in the range of 2 to 100 nm, particularly preferably in the range of 5 to 80 nm, because the slippage between the films is suppressed and the effect of preventing winding deviation is enhanced. . The arithmetic average roughness Ra can be measured according to JIS (Japanese Industrial Standards; B0601: 2001).

  The height of the protrusion shape for obtaining the arithmetic average roughness Ra is preferably in the range of 2 nm to 4 μm. The width of the protrusion shape is in the range of 50 nm to 300 μm, and preferably in the range of 50 nm to 100 μm.

  The 10-point average roughness Rz of the hard coat layer is 10 times or less of the centerline average roughness Ra, and the average mountain valley distance Sm is preferably 5 to 150 μm, more preferably 20 to 100 μm, and the height of the protrusion from the deepest part of the unevenness. Preferably, the standard deviation of the mean valley distance Sm with respect to the center line is 20 μm or less, and the surface with the inclination angle of 0 to 5 degrees is preferably 10% or more. The arithmetic average roughness Ra, Sm, Rz described above is a value measured with an optical interference surface roughness meter (manufactured by ZYGO, NewView) in accordance with JIS B0601: 2001.

(Haze)
The haze of the hard coat film is preferably in the range of 0.2 to 10% from the visibility when used in an image display device. Haze can be measured according to JIS-K7105 and JIS K7136.

(hardness)
The hard coat film of this embodiment has a pencil hardness, which is an index of hardness, of HB or more, more preferably H or more. If it is more than HB, it is hard to be damaged in the polarizing plate forming step. The pencil hardness is determined by adjusting the humidity of the produced optical film at a temperature of 23 ° C. and a relative humidity of 55% for 2 hours or more, and then using a test pencil specified by JIS S 6006 under a load of 500 g. Or it is the value which measured the functional layer according to the pencil hardness evaluation method which JISK5400 prescribes | regulates.

<Cellulose ester film>
Next, the cellulose ester film as the thin film optical film of this embodiment and the cellulose ester film bonded to the back surface side of the polarizing plate will be described.

  Examples of the cellulose ester film (hereinafter also referred to as cellulose acetate film) include a triacetyl cellulose film, a cellulose acetate propionate film, a cellulose diacetate film, and a cellulose acetate butyrate film. The cellulose ester film may be used in combination with polyester resins such as polyethylene terephthalate and polyethylene naphthalate, polycarbonate resins, polyethylene resins, polypropylene resins, norbornene resins, fluororesins, and cycloolefin polymers. Examples of commercially available cellulose ester films include Konica Minoltak KC8UX, KC4UX, KC8UY, KC4UY, KC6UA, KC4UA, KC4UE, and KC4UZ (manufactured by Konica Minolta Opto, Inc.). The refractive index of the cellulose ester film is preferably 1.45 to 1.55. The refractive index can be measured according to JIS K7142-2008.

(Cellulose ester resin)
The cellulose ester resin (hereinafter also referred to as cellulose ester) is preferably a lower fatty acid ester of cellulose. The lower fatty acid in the lower fatty acid ester of cellulose means a fatty acid having 6 or less carbon atoms. For example, cellulose acetate, cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, etc. Further, mixed fatty acid esters such as cellulose acetate butyrate can be used.

  Among the above descriptions, the lower fatty acid esters of cellulose that are particularly preferably used are cellulose diacetate, cellulose triacetate, and cellulose acetate propionate. These cellulose esters can be used alone or in combination.

  Cellulose diacetate preferably has an average degree of acetylation (bound acetic acid amount) of 51.0% to 56.0%. Examples of commercially available products include L20, L30, L40, and L50 manufactured by Daicel Corporation, and Ca398-3, Ca398-6, Ca398-10, Ca398-30, and Ca394-60S manufactured by Eastman Chemical Japan Co., Ltd. .

  The cellulose triacetate preferably has an average degree of acetylation (bound acetic acid amount) of 54.0 to 62.5%, and more preferably cellulose triacetate having an average degree of acetylation of 58.0 to 62.5%. is there.

  Cellulose triacetate has a number average molecular weight (Mn) of 125,000 or more and less than 155000, 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, acetyl group substitution degree Triacetate having a number average molecular weight (Mn) of 155,000 or more and less than 180,000, a weight average molecular weight (Mw) of 290000 or more and less than 360,000, and Mw / Mn of 1.8 to 2.0. It is preferable to contain B.

  Cellulose acetate propionate has an acyl group having 2 to 4 carbon atoms as a substituent. When the substitution degree of acetyl group is X and the substitution degree of propionyl group or butyryl group is Y, the following formula (I ) And (II) are preferably satisfied at the same time.

Formula (I) 2.6 ≦ X + Y ≦ 3.0
Formula (II) 0 ≦ X ≦ 2.5
Among them, it is preferable that 1.9 ≦ X ≦ 2.5 and 0.1 ≦ Y ≦ 0.9.

  The degree of substitution of the acyl group can be measured according to ASTM-D817-96, which is one of the standards formulated and issued by ASTM (American Society for Testing and Materials).

  The number average molecular weight (Mn) and the weight average molecular weight (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 Corp.) Mw = 100000 to 500 samples were used. The 13 samples are preferably used at approximately equal intervals.

(Thermoplastic acrylic resin)
A cellulose ester film and a thermoplastic acrylic resin may be used in combination. When using together, it is preferable that the containing mass ratio of a thermoplastic acrylic resin and a cellulose-ester resin is thermoplastic acrylic resin: cellulose-ester resin = 95: 5-50: 50.

  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 may be mentioned, and these may be used alone or in combination of two or more.

  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 a weight average molecular weight (Mw) is 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. Commercially available acrylic resins include, for example, Delpet 60N, 80N (Asahi Kasei Chemicals Corporation), Dialnal BR52, BR80, BR83, BR85, BR88 (Mitsubishi Rayon Co., Ltd.), KT75 (Electrochemical Industry Co., Ltd.) )) And the like. Two or more acrylic resins can be used in combination.

(Fine particles)
In order to improve the handleability, the cellulose ester film of the present embodiment has, for example, acrylic particles, silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin, talc, calcined calcium silicate, and hydrated calcium silicate. It is preferable to contain a matting agent such as inorganic fine particles such as aluminum silicate, magnesium silicate and calcium phosphate and a crosslinked polymer. The acrylic particles are not particularly limited, but are preferably multi-layered acrylic granular composites. Among these, silicon dioxide is preferable in that the haze of the cellulose ester film can be reduced. The primary average particle diameter of the fine particles is preferably 20 nm or less, more preferably in the range of 5 to 16 nm, and particularly preferably in the range of 5 to 12 nm.

  It is preferable that the cellulose acetate film of this embodiment contains the ester compound or sugar ester represented by the following general formula (X) from the dimensional stability by an environmental change. First, the ester compound represented by the general formula (X) will be described.

Formula (X) B- (GA) n-GB
(Wherein B is a hydroxy group or carboxylic acid residue, G is an alkylene glycol residue having 2 to 12 carbon atoms, an aryl glycol residue having 6 to 12 carbon atoms, or an oxyalkylene glycol residue having 4 to 12 carbon atoms) , A represents an alkylene dicarboxylic acid residue having 4 to 12 carbon atoms or an aryl dicarboxylic acid residue having 6 to 12 carbon atoms, and n represents an integer of 1 or more.)

  In the general formula (X), as the alkylene glycol component having 2 to 12 carbon atoms, 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 There are 1,3-hexanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, and the like. Used as a mixture of two or more. In particular, an alkylene glycol having 2 to 12 carbon atoms is particularly preferable because of excellent compatibility with cellulose acetate. Examples of the aryl glycol component having 6 to 12 carbon atoms include hydroquinone, resorcin, bisphenol A, bisphenol F, bisphenol and the like, and these glycols can be used as one kind or a mixture of two or more kinds.

  Examples of the oxyalkylene glycol component having 4 to 12 carbon atoms include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, and the like. These glycols are one kind or two or more kinds. Can be used as a mixture. Examples of the alkylene dicarboxylic acid component having 4 to 12 carbon atoms include succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, and the like. Used as a mixture of two or more. Examples of the arylene dicarboxylic acid component having 6 to 12 carbon atoms include phthalic acid, terephthalic acid, isophthalic acid, 1,5-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, and the like. Although the specific example (compound X-1-compound X-17) of a compound represented by general formula (X) below is shown, it is not limited to this.

  Next, the sugar ester compound will be described. The sugar ester compound is an ester other than cellulose ester, and is a compound obtained by esterifying all or a part of OH groups of sugars such as the following monosaccharide, disaccharide, trisaccharide or oligosaccharide. Examples of the sugar include glucose, galactose, mannose, fructose, xylose, arabinose, lactose, sucrose, nystose, 1F-fructosyl nystose, stachyose, maltitol, lactitol, lactulose, cellobiose, maltose, cellotriose, maltotriose, raffinose And kestose. In addition, gentiobiose, gentiotriose, gentiotetraose, xylotriose, galactosyl sucrose, and the like are also included. Among these compounds, compounds having a furanose structure and / or a pyranose structure are particularly preferable. Among these, sucrose, kestose, nystose, 1F-fructosyl nystose, stachyose and the like are preferable, and sucrose is more preferable. As oligosaccharides, maltooligosaccharides, isomaltooligosaccharides, fructooligosaccharides, galactooligosaccharides, and xylo-oligosaccharides can also be preferably used.

  The monocarboxylic acid used for esterifying the sugar is not particularly limited, and known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid and the like can be used. The carboxylic acid to be used may be one kind or a mixture of two or more kinds. Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, lauric acid , Saturated fatty acids such as tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, heptacosanoic acid, montanic acid, melicic acid, and laccelic acid, Examples include unsaturated fatty acids such as undecylenic acid, oleic acid, sorbic acid, linoleic acid, linolenic acid, arachidonic acid and octenoic acid. Examples of preferred alicyclic monocarboxylic acids include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, or derivatives thereof. Examples of preferred aromatic monocarboxylic acids include benzoic acid, aromatic monocarboxylic acids having an alkyl group or alkoxy group introduced into the benzene ring of benzoic acid, cinnamic acid, benzylic acid, biphenylcarboxylic acid, naphthalenecarboxylic acid, tetralin An aromatic monocarboxylic acid having two or more benzene rings such as carboxylic acid, or a derivative thereof can be mentioned, and more specifically, xylic acid, hemelic acid, mesitylene acid, planicylic acid, γ-isojurylic acid, Julylic acid, mesitic acid, α-isoduric acid, cumic acid, α-toluic acid, hydroatropic acid, atropic acid, hydrocinnamic acid, salicylic acid, o-, m, p-anisic acid, creosote acid, o-, m, p-homosalicylic acid, o-pyrocatechuic acid, β-resorcylic acid, vanillic acid, isovanillic acid, veratrum acid o- veratric acid, gallic acid, asarone acid, mandelic acid, homoanisic acid, homovanillic acid, homoveratric acid, o- homoveratric acid, Futaron acid, can be mentioned p- coumaric acid, especially benzoic acid. Among the ester compounds esterified, an acetyl compound into which an acetyl group has been introduced by esterification is preferable. Although the specific example of the sugar ester compound which can be used for this embodiment below is shown, it is not limited to these.

  The sugar ester compound is preferably a compound represented by the general formula (Y). Below, the compound shown by general formula (Y) is demonstrated.

（式中、Ｒ_１〜Ｒ_８は、水素原子、置換若しくは無置換の炭素数２〜２２のアルキルカルボニル基、あるいは、置換又は無置換の炭素数２〜２２のアリールカルボニル基を表し、Ｒ_１〜Ｒ_８は、同じであっても、異なっていてもよい。）

(Wherein R _{1 to} R ₈ represent a hydrogen atom, 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 with general formula (Y) below is shown more concretely (compound Y-1-compound Y-23), it is not limited to these. In the following table, when the average degree of substitution is less than 8.0, any one of R _{1 to} R ₈ represents a hydrogen atom.

  The substitution degree distribution can be adjusted to the target substitution degree by adjusting the esterification reaction time or mixing compounds having different substitution degrees.

  The ester compound or sugar ester compound represented by the general formula (X) is preferably contained in the cellulose acetate film in an amount of 1 to 30% by mass, more preferably 5 to 25% by mass, and more preferably 5 to 20% by mass. It is particularly preferable to contain it.

(Other additives)
[Plasticizer]
The cellulose acetate film of this embodiment may contain a plasticizer as necessary. The plasticizer is not particularly limited, but is a polyvalent carboxylic ester plasticizer, glycolate plasticizer, phthalate ester plasticizer, phosphate ester plasticizer, and polyhydric alcohol ester plasticizer, acrylic. A plasticizer etc. are mentioned. In these, an acrylic plasticizer is preferable from the point which can control a cellulose-ester film to the retardation value mentioned later.

  The polyhydric alcohol ester plasticizer is a plasticizer comprising an ester of a divalent or higher aliphatic polyhydric alcohol and a monocarboxylic acid, and preferably has an aromatic ring or a cycloalkyl ring in the molecule. Preferably it is a 2-20 valent aliphatic polyhydric alcohol ester. Specific examples of the polyhydric alcohol ester plasticizer are shown below, but are not limited thereto.

  The glycolate plasticizer is not particularly limited, but alkylphthalylalkyl glycolates can be preferably used. Examples of alkyl phthalyl alkyl glycolates include methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, octyl phthalyl octyl glycolate, methyl phthalyl ethyl Glycolate, ethyl phthalyl methyl glycolate, ethyl phthalyl propyl glycolate, methyl phthalyl butyl glycolate, ethyl phthalyl butyl glycolate, butyl phthalyl methyl glycolate, butyl phthalyl ethyl glycolate, propyl phthalyl butyl glycol Butyl phthalyl propyl glycolate, methyl phthalyl octyl glycolate, ethyl phthalyl octyl glycolate, octyl phthalyl methyl glycolate, octyl phthalate Ethyl glycolate, and the like.

  Examples of the phthalate ester plasticizer include diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, dioctyl phthalate, dicyclohexyl phthalate, and dicyclohexyl terephthalate.

  Phosphate ester plasticizers include triphenyl phosphate (TPP), tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, butylphenyl diphenyl phosphate (BDP), etc. Can be mentioned.

  The polyvalent carboxylic acid ester plasticizer is a compound composed of an ester of a divalent or higher valent, preferably a divalent to -20 valent polyvalent carboxylic acid and an alcohol. Specific examples include triethyl citrate, tributyl citrate, acetyl triethyl citrate (ATEC), acetyl tributyl citrate (ATBC), benzoyl tributyl citrate, acetyl triphenyl citrate, acetyl tribenzyl citrate, dibutyl tartrate, tartaric acid Examples include, but are not limited to, diacetyldibutyl, tributyl trimellitic acid, tetrabutyl pyromellitic acid, and the like.

  The acrylic plasticizer is preferably an acrylic polymer, and the acrylic polymer is preferably a homopolymer or copolymer of acrylic acid or alkyl methacrylate. 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 monomers, but the acrylic acid methyl ester monomer unit preferably 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.

(UV absorber)
The cellulose acetate film of this embodiment may contain an ultraviolet absorber. Since the ultraviolet absorber absorbs ultraviolet rays of 400 nm or less, durability can be improved. In particular, the ultraviolet absorber preferably has a transmittance of 10% or less at a wavelength of 370 nm, more preferably 5% or less, and still more preferably 2% or less. Specific examples of the ultraviolet absorber are not particularly limited. For example, oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, triazine compounds, nickel complex salts, inorganic powders. Examples include the body.

  More specifically, for example, 5-chloro-2- (3,5-di-sec-butyl-2-hydroxylphenyl) -2H-benzotriazole, (2-2H-benzotriazol-2-yl) -6 -(Linear and side chain dodecyl) -4-methylphenol, 2-hydroxy-4-benzyloxybenzophenone, 2,4-benzyloxybenzophenone, etc. can be used. Commercially available products may be used. For example, TINUVIN such as TINUVIN 109, TINUVIN 171, TINUVIN 234, TINUVIN 326, TINUVIN 327, and TINUVIN 328 manufactured by BASF Japan Ltd. can be preferably used.

  Preferred ultraviolet absorbers are benzotriazole ultraviolet absorbers, benzophenone ultraviolet absorbers, and triazine ultraviolet absorbers, and particularly preferred are benzotriazole ultraviolet absorbers and benzophenone ultraviolet absorbers.

  In addition, a discotic compound such as a compound having a 1,3,5 triazine ring is also preferably used as the ultraviolet absorber. As the UV absorber, a polymer UV absorber can be preferably used, and a polymer type UV absorber is particularly preferably used.

  As a benzotriazole ultraviolet absorber, TINUVIN 109 (octyl-3- [3-tert-butyl-4-hydroxy-5- (5-chloro-2H-benzotriazole-2-) manufactured by BASF Japan Ltd., which is a commercial product, is available. Yl) phenyl] propionate and 2-ethylhexyl-3- [3-tert-butyl-4-hydroxy-5- (5-chloro-2H-benzotriazol-2-yl) phenyl] propionate), TINUVIN 928 (2 -(2H-benzotriazol-2-yl) -6- (1-methyl-1-phenylethyl) -4- (1,1,3,3-tetramethylbutyl) phenol) and the like can be used. As the triazine-based ultraviolet absorber, TINUVIN 400 (2- (4,6-bis (2,4-dimethylphenyl) -1,3,5-triazin-2-yl) -manufactured by BASF Japan Ltd., which is a commercial product, is available. Reaction product of 5-hydroxyphenyl and oxirane), TINUVIN 460 (2,4-bis [2-hydroxy-4-butoxyphenyl] -6- (2,4-dibutoxyphenyl) -1,3-5 Triazine), TINUVIN 405 (2- (2,4-dihydroxyphenyl) -4,6-bis- (2,4-dimethylphenyl) -1,3,5-triazine and (2-ethylhexyl) -glycidic acid ester Reaction products) and the like.

  The ultraviolet absorber is added by dissolving the ultraviolet absorber in an alcohol, such as methanol, ethanol, butanol or the like, an organic solvent such as methylene chloride, methyl acetate, acetone, dioxolane, or a mixed solvent thereof, and then becomes a film substrate. It may be added to the resin solution (dope) or directly during the dope composition. For an inorganic powder that does not dissolve in an organic solvent, a dissolver or a sand mill is used in the organic solvent and cellulose acetate to disperse and then added to the dope.

  0.5-10 mass% is preferable with respect to a cellulose acetate film, and, as for the usage-amount of a ultraviolet absorber, 0.6-4 mass% is still more preferable.

(Antioxidant)
The cellulose acetate film of the present embodiment may further contain an antioxidant (deterioration inhibitor). The antioxidant has a role of delaying or preventing the cellulose acetate film from being decomposed by a residual solvent amount of halogen in the cellulose acetate film, phosphoric acid of a phosphoric acid plasticizer, or the like. As the antioxidant, hindered phenol compounds are preferably used. For example, 2,6-di-tert-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl). -4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3 5-di-t-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino) -1,3 5-triazine, 2,2-thio-diethylenebis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], octadecyl-3- 3,5-di-tert-butyl-4-hydroxyphenyl) propionate, N, N'-hexamethylenebis (3,5-di-tert-butyl-4-hydroxy-hydrocinnamamide), 1,3 5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-t-butyl-4-hydroxybenzyl) -isocyanurate Etc. The addition amount of these compounds is preferably 1 ppm to 10000 ppm, more preferably 10 to 1000 ppm in terms of mass ratio with respect to the cellulose acetate film.

(Disadvantage)
The cellulose ester film preferably has a defect of 5 μm or more in diameter of 1 piece / 10 cm 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, defects are caused by voids in the film (foaming defects) generated due to rapid evaporation of the solvent in the drying process of solution casting, foreign substances in the film forming stock solution, and foreign substances mixed in the film forming process. This refers to foreign matter (foreign matter defect) in the film to be transferred, roller scratch transfer and scratches. 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 surface shape, such as transfer of a roller scratch or an abrasion, the size of the defect can be confirmed by observing the defect with reflected light of a differential interference microscope.

  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. When the defect diameter is 5 μm or more, the defect can be visually confirmed by polarizing plate observation or the like, and a bright spot may be generated when the film is used as an optical member. Even when the defects cannot be visually confirmed, when the hard coat layer is formed, the coating film may not be formed uniformly, and the coating may be lost.

  In the measurement based on JIS-K7127-1999, the base film preferably has a breaking elongation of at least one direction of 10% or more, more preferably 20% or more. 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.

(optical properties)
The cellulose ester film 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%. The haze value is preferably 2% or less, more preferably 1.5% or less. The total light transmittance and haze value can be measured according to JIS K7361 and JIS K7136.

  The in-plane retardation value Ro of the cellulose ester film is preferably in the range of 0 to 5 nm and the retardation value Rth in the thickness direction is in the range of −10 to 10 nm. Further, Rth is more preferably in the range of −5 to 5 nm.

  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
(Where nx is the refractive index in the slow axis direction in the cellulose ester film plane, ny is the refractive index in the direction perpendicular to the slow axis in the substrate film plane, and nz is the refractive index in the thickness direction of the cellulose ester film. The rate and d each represent the thickness (nm) of the cellulose ester film.)

  The retardation can be obtained at a measurement wavelength of 590 nm in an environment of 23 ° C. and 55% RH (relative humidity) using, for example, KOBRA-21ADH (manufactured by Oji Scientific Instruments). By using the cellulose ester film controlled to the above retardation value, it is preferable from the viewpoint of excellent visibility when used in an image display device such as a touch panel or a liquid crystal display device. Retardation can be adjusted by the kind and addition amount of a plasticizer mentioned above, the film thickness of a cellulose ester film, stretching conditions, and the like.

(Film formation of cellulose ester film)
(Organic solvent)
The cellulose ester film of the present embodiment is formed by a solution casting method (solution casting method). An organic solvent useful for forming a resin solution (dope composition) when a cellulose ester film is formed by a solution casting method is not limited as long as it dissolves a cellulose ester resin and other additives at the same time. Can be used. 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- 2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, nitroethane, methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, tert-butanol, etc. Can, methylene chloride, methyl acetate, ethyl acetate, may be used preferably acetone. The solvent is preferably a dope composition in which a total of 15 to 45 mass% of a cellulose ester resin and other additives are dissolved.

(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-shaped or drum-shaped 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 peeled web, the step of drying the web, and the step of winding up the finished cellulose ester film are performed. More specific description will be given below.

  FIG. 1 is a cross-sectional view schematically showing an example of an apparatus for producing a cellulose ester film as a thin film optical film of the present embodiment. In FIG. 1, first, a resin such as cellulose ester is dissolved in a mixed solvent of a good solvent and a poor solvent in a dissolving pot 1, and an additive such as a plasticizer or an ultraviolet absorber is added thereto to prepare a dope. .

  Next, the dope adjusted in the melting pot 1 is fed to the casting die 3 through a pressurized metering gear pump 2 by a conduit, and flows on the metal support 6 made of a rotationally driven stainless steel endless belt that is infinitely transported. The dope is cast from the casting die 3 at the extending position, and the web 9 (casting film) formed thereby is brought into contact with the metal support 6. The endless belt as the metal support 6 is held by a pair of front and rear drums 5 and 5 and a plurality of intermediate rolls (not shown). A drive device (not shown) for applying tension to the endless belt is provided on one or both of the endless belt drums 5 and 5 so that the endless belt is tensioned and tensioned. Used in.

  Instead of the endless belt, a stainless steel rotary drive drum having a hard chrome plating surface is used as the metal support 6, and a dope is cast from the casting die 3 onto the rotary drive drum. A web may be formed.

  The dope is cast by the casting die 3 using a doctor blade method in which the film thickness of the cast web is adjusted by a blade, a method by a reverse roll coater in which the film thickness is adjusted by a reverse rotating roll, There is a method using a pressure die. Among them, a method using a pressure die is preferable because the slit shape of the base portion can be adjusted and the film thickness can be easily made uniform. The pressure die includes a coat hanger die and a T die, and any of them can be preferably used.

  In the solution casting method, the solid content concentration of a dope such as cellulose ester cast from the casting die 3 onto the metal support 6 is preferably 15 to 30% by weight. If the solid content concentration of the dope is less than 15% by weight, sufficient drying cannot be performed on the metal support 6, and a part of the web remains on the metal support 6 at the time of peeling, leading to contamination (for example, belt contamination). . Further, when the solid content concentration of the dope exceeds 30%, the dope viscosity becomes high, the filter clogging is accelerated in the dope adjusting process, or the pressure becomes high when the dope is cast on the metal support 6, It may not be possible to extrude.

  The dope cast on the surface of the metal support 6 in this way also increases the strength of the gel film (film strength) by promoting drying until stripping.

  In order to dry and solidify the web 9 until the film strength is peelable from the metal support 6 by the peeling roll 8, it is preferable that the residual solvent amount in the web 9 is dried to 150% by weight or less on the metal support 6. 80 to 120% by weight is more preferable. Moreover, as for the web temperature when peeling the web 9 from the metal support body 6, 0-30 degreeC is preferable. Further, immediately after the web 9 is peeled off from the metal support 6, the temperature rapidly decreases once due to the solvent evaporation from the contact surface side with the metal support 6, and volatile components such as water vapor and solvent vapor in the atmosphere are condensed. Since it is easy to do, the web temperature at the time of peeling has more preferable 5-30 degreeC.

Here, the residual solvent amount can be expressed by the following equation.
Residual solvent amount (% by weight) = {(M−N) / N} × 100
In the formula, M is the weight of the web at an arbitrary point in time, and N is the weight when a weight M is dried at 110 ° C. for 3 hours.

  The web 9 formed by the dope cast on the metal support 6 is heated on the metal support 6, and the solvent is evaporated until the web 9 can be peeled from the metal support 6 by the peeling roll 8. For evaporating the solvent, there are a method of blowing air from the web 9 side, a method of transferring heat from the back surface of the metal support 6 by liquid, a method of transferring heat from the front and back by radiant heat, and the like. Can be used.

  The peeling tension at the time of peeling the web 9 from the metal support 6 with the peeling roll 8 is preferably larger than the peeling force obtained by measuring the peeling force as in JIS Z 0237. This is done at a higher level for stabilization, since when the release tension is made equal to the peel force obtained by the JIS measurement method at the time of high-speed film formation, the peel position may be taken downstream. However, even if the film is formed with the same peeling tension in the process, it is confirmed that the variation in the crossed Nicols transmittance (CNT) of the film is greatly reduced when the peeling force by the JIS measuring method is lowered.

  As the peeling tension value in the process, peeling is usually performed at 50 to 250 N / m.

  After the web 9 is dried and solidified to a peelable film strength on the metal support 6, the web 9 is peeled off by the peeling roll 8, and then the web 9 is stretched in the tenter 10 in the stretching process.

  In the stretching step, a tenter system in which both side edges of the web 9 are fixed with clips or the like and stretched is preferable as the liquid crystal display device film in order to improve the flatness and dimensional stability of the film.

  The residual solvent amount of the web 9 immediately before entering the tenter 10 in the stretching process is preferably 1 to 10% by weight. Moreover, the stretch ratio of the web in the tenter 10 in the stretching process is 1 to 100%, preferably 3 to 80%, and more preferably 3 to 60%.

  Moreover, the temperature of the warm air blown from the warm air blowing slit port in the tenter 10 is 100 to 200 ° C, preferably 110 to 190 ° C, and more preferably 115 to 185 ° C.

  A drying device 11 is provided after the tenter 10 in the stretching process. In the drying device 11, the web 9 is meandered by a plurality of conveying rolls arranged in a staggered manner as viewed from the side, and the web 9 is dried in the meantime. The film transport tension in the drying apparatus 11 is affected by the physical properties of the dope, the amount of residual solvent in the peeling and film transport process, the drying temperature, etc., but the film transport tension during drying is 10 to 300 N / m width. Yes, 20 to 270 N / m width is more preferable.

  The means for drying the web (film) 9 is not particularly limited, and is generally performed by hot air, infrared rays, a heating roll, microwaves, or the like. It is preferable to dry with hot air from the viewpoint of simplicity. For example, it is dried by the drying air 12 blown from the hot air inlet of the drying device 11 and dried by exhausting the exhaust air from the outlet of the drying device 11. The temperature of the drying air 12 is preferably 40 to 160 ° C, and more preferably 50 to 160 ° C in order to improve the flatness and dimensional stability.

  These steps from casting to post-drying may be performed in an air atmosphere or in an inert gas atmosphere such as nitrogen gas. In this case, it goes without saying that the dry atmosphere is carried out in consideration of the explosion limit concentration of the solvent.

  The optical film F conveyed after finishing the drying process in the drying device 11 is wound up by the winding device 13 to obtain the original roll (original fabric) of the optical film. A film with good dimensional stability can be obtained by setting the residual solvent amount of the dried film to 0.5 wt% or less, preferably 0.1 wt% or less.

  The winding method of the film may be a generally used winder, and there are methods for controlling the tension such as a constant torque method, a constant tension method, a taper tension method, a program tension control method with a constant internal stress, etc. Use it properly. The film may be bonded to the winding core (winding core) by either a double-sided adhesive tape or a single-sided adhesive tape.

  The film thickness after drying of the optical film F such as cellulose ester is preferably 15 μm or more and 30 μm or less from the viewpoint of thinning the liquid crystal display device. Here, the film thickness after drying refers to the film thickness when the amount of residual solvent in the optical film F is 0.5% by weight or less.

  When the film thickness of the optical film F after winding is too thin, the intensity | strength required as a protective film for polarizing plates may not be acquired, for example. On the other hand, when the film thickness of the optical film F is too thick, the advantage of thinning is lost with respect to conventional resin films such as cellulose ester. For adjusting the film thickness, the dope concentration, the pumping amount, the slit gap of the die of the casting die 3, the extrusion pressure of the casting die 3, the speed of the metal support 6 and the like are adjusted so as to obtain a desired thickness. It is good to control. Further, as a means for making the film thickness uniform, it is preferable to use a film thickness detection means to feed back and adjust the programmed feedback information to each of the above devices.

(Physical properties of cellulose ester film)
As described above, the film thickness of the cellulose ester film in the present embodiment is desirably 15 μm or more and 30 μm or less. The cellulose ester film preferably has a width of 1 to 4 m. If it exceeds 4 m, conveyance becomes difficult.

  Moreover, 500-10000m is preferable and, as for the length of a cellulose-ester film, More preferably, it is 1000-8000m. By setting it as the range of the said length, it is excellent in the processability in application | coating, such as a hard-coat layer, and the handleability of a cellulose-ester film itself.

  Moreover, arithmetic mean roughness Ra of a cellulose-ester film becomes like this. Preferably it is 2-10 nm, More preferably, it is 2-5 nm. The arithmetic average roughness Ra can be measured according to JIS B0601: 1994.

  The water contact angle before the alkali treatment of the cellulose ester film is generally in the range of 40 ° to 80 °, preferably 50 ° to 70 °. The contact angle with water after the alkali treatment is generally 10 ° to 60 °, preferably 20 ° to 60 °, although it depends on the alkali treatment conditions. The water contact angle is a value measured according to the method described in the method for measuring the water contact angle of the hard coat layer.

  It is estimated that the water contact angle of the hard coat layer is lowered by the alkali treatment and approaches the water contact angle of the cellulose ester film, whereby the hydrophilic layers are laminated to each other, and an anti-winding effect is obtained. . As an alkali treatment method, the cellulose ester film is immersed in an alkali solution, washed with water and dried. Further, after the alkali treatment, neutralization in an acidic water step may be performed, followed by washing with water and drying.

  Examples of the alkaline solution include a potassium hydroxide solution and a sodium hydroxide solution, and the concentration of hydroxide ions is preferably in the range of 0.1 to 5 mol / L, and preferably 0.5 mol / L to 3 mol / L. More preferably, it is in the range. Furthermore, the temperature of the alkaline solution is preferably in the range of 25 to 90 ° C, more preferably in the range of 40 to 70 ° C. The alkali treatment time is in the range of 5 seconds to 5 minutes, preferably in the range of 30 seconds to 3 minutes.

<Other layers>
The hard coat film of this embodiment can be provided with other layers such as an antireflection layer and a conductive layer.

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

  The antireflection layer is preferably formed 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 composed of a low refractive index layer having a lower refractive index than that of the protective film as the support, or a combination of a high refractive index layer and a low refractive index layer having a higher refractive index than that of the protective film as the support. It is preferable. 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, the following structure is conceivable, but is not limited thereto.

Cellulose ester film / hard coat layer / low refractive index layer Cellulose ester film / hard coat layer / high refractive index layer / low refractive index layer Cellulose ester film / hard coat layer / medium refractive index layer / high refractive index layer / low refractive index Layer hard coat layer / cellulose ester film / hard coat layer / low refractive index layer hard coat layer / cellulose ester film / hard coat layer / high refractive index layer / low refractive index layer hard coat layer / cellulose ester film / hard coat layer / Medium refractive index layer / High refractive index layer / Low refractive index layer Low refractive index layer / Hard coat layer / Cellulose ester film / Hard coat 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 when measured at 23 ° C. and a wavelength of 550 nm.

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

  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 porous or hollow inside 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.

  In addition, a silane coupling agent, a curing agent, a surfactant, and the like may be added to the composition for forming a low refractive index layer, if necessary. 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, a fluorine-containing polymer or a fluorine-containing sol-gel compound is used. 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.

(High refractive index layer)
About the refractive index of a high refractive index layer, it is preferable to adjust to the range of 1.4-2.2 by 23 degreeC and wavelength 550nm measurement. 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.

  Adjustment of the refractive index of the high refractive index layer can be realized by adding metal oxide fine particles and the like. The metal oxide fine particles used preferably have a refractive index of 1.80 to 2.60, 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.

(Conductive layer)
The hard coat film may be configured by forming a conductive layer on the hard coat layer. As the conductive layer provided, a generally well-known conductive material can be used. For example, metal oxides such as indium oxide, tin oxide, indium tin oxide, gold, silver, and palladium can be used. These can be formed as a thin film on the hard coat film by vacuum deposition, sputtering, ion plating, solution coating, or the like. Moreover, it is also possible to form a conductive layer using the organic conductive material which is the above-described π-conjugated conductive polymer.

  In particular, a conductive material that is excellent in transparency and conductivity, and that has a main component of any of indium oxide, tin oxide, and indium tin oxide, which can be obtained at a relatively low cost, can be suitably used. Although the thickness of the conductive layer varies depending on the material to be applied, it cannot be said unconditionally. However, the surface resistivity is 1000Ω or less, preferably 500Ω or less, and considering the economy, A range of 10 nm or more, preferably 20 nm or more and 80 nm or less, preferably 70 nm or less is suitable. In such a thin film, visible light interference fringes due to uneven thickness of the conductive layer are unlikely to occur.

<Polarizing plate>
Next, a polarizing plate using the hard coat film of this embodiment will be described. The polarizing plate can be produced by a general method.

  For example, a completely saponified polyvinyl alcohol aqueous solution is used on at least one surface of a polarizing film prepared by subjecting the hard coat film of the present embodiment to an alkali saponification treatment and immersing and stretching the treated hard coat film in an iodine solution. It is preferable to bond them together.

  For the other surface of the polarizing film, the hard coat film may be used, or the cellulose ester film described above may be used. The film thickness of the cellulose ester film used for the other surface is preferably in the range of 5 to 34 μm from the viewpoint of adjusting smoothness and curl balance and further enhancing the effect of preventing winding deviation.

  A polarizing film (polarizer), which is a main component of a polarizing plate, is an element that allows only light in a polarization plane in a certain direction to pass through. A typical polarizing film known at present is a polyvinyl alcohol polarizing film, This includes, but is not limited to, a polyvinyl alcohol film dyed with iodine and a dichroic dye dyed.

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

  On the surface of the polarizing film, one side of the hard coat 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 to be bonded to the substrate of the liquid crystal cell is preferably optically transparent and exhibits moderate viscoelasticity and adhesive properties.

  Specific examples of the adhesive layer include adhesives or adhesives such as acrylic copolymers, epoxy resins, polyurethanes, silicone polymers, polyethers, butyral resins, polyamide resins, polyvinyl alcohol resins, and synthetic rubbers. A film such as a drying method, a chemical curing method, a thermal curing method, a thermal melting method, a photocuring method, or the like can be formed and cured using a polymer such as the above. Among them, the acrylic copolymer can be preferably used because it is most easy to control the physical properties of the adhesive and is excellent in transparency, weather resistance, durability and the like.

<Winding>
The thickness of the air layer held between the layers when the hard coat film, cellulose ester film or polarizing plate of the present embodiment is wound into a roll is preferably 0.5 μm to 10 μm, more preferably 1 to 5 μm. The air layer thickness (t ′) is a value obtained from an equation of t ′ = [{π (D ² −d ² ) / 4L} −t]. In the above formula, D represents the winding diameter, d represents the winding core diameter, L represents the winding length, t represents the film thickness, and all units are μm.

  In addition, the method of winding up the hard coat film, etc., is to provide a roll that the film touches in front of the take-up shaft and wind up the film, or when taking up the film on the take-up shaft. A method of winding the film while the roll to be touched is gradually separated at a constant distance (gap winding), a film winding unit for winding the film around the core by rotating the core, and the film on the core It is possible to use an oscillating winding method in which winding is performed while periodically shifting within a certain range in the width direction. The air layer thickness can be controlled by adjusting winding conditions (for example, adjusting tension during winding).

<Image display device>
The hard coat film of this embodiment is preferable in that the performance excellent in visibility (clearness) is exhibited by using it in an image display device. As an image display device, a reflection type, a transmission type, a transflective type liquid crystal display device, a liquid crystal display device of various drive systems such as a TN type, STN type, OCB type, VA type, IPS type, ECB type, etc., a touch panel display device And organic EL display devices and plasma displays. Among these image display devices, when the hard coat film of the present embodiment is used for a liquid crystal display device or a touch panel display device, it is preferable in terms of excellent visibility.

  FIG. 2 is a cross-sectional view showing a schematic configuration of a liquid crystal display device 20 which is an example of an image display device to which the hard coat film of the present embodiment is applied. The liquid crystal display device 20 is configured such that a polarizing plate 22 is bonded to one surface of a liquid crystal cell 21 having a liquid crystal layer sandwiched between two substrates, and a polarizing plate 23 is bonded to the other surface. Here, the side where the polarizing plate 22 is provided with respect to the liquid crystal cell 21 is defined as a light emitting side (viewing side).

  Cellulose ester films 41 and 42 are respectively attached to both surfaces of the polarizing film 31 (polarizer) of the polarizing plate 22, and the cellulose ester film 43 is formed on both surfaces of the polarizing film 32 (polarizer) of the polarizing plate 23.・ 44 are pasted. Further, a hard coat layer 51 is formed on the surface of the cellulose ester film 41 located on the opposite side of the liquid crystal cell 21 among the cellulose ester films 41 and 42 of one polarizing plate 22. The cellulose ester film 41 and the hard coat layer 51 constitute the hard coat film 60 of the present embodiment. About the polarizing films 31 and 32, the cellulose-ester films 41-44, and the hard-coat layer 51, the above-mentioned thing can be used. Note that another layer such as the above-described antireflection layer may be formed on the surface of the hard coat layer 51 of the hard coat film 60.

<Method for producing hard coat film>
In the present embodiment, from the viewpoint of suppressing the curing shrinkage unevenness of the hard coat layer 51 in the hard coat film 60 and the application unevenness when the adhesive for adhering to the polarizing film 31 is applied to the cellulose ester film 41, the following: The hard coat film 60 is manufactured by this method.

  In the present embodiment, a cellulose ester film 41 as a thin film optical film having a film thickness of 15 μm or more and 30 μm or less is formed by a solution casting method, and a plasticizer A (first plasticizer) is formed on the cellulose ester film 41. And silica fine particles as a matting agent.

  The plasticizer A has a property of being unevenly distributed on the metal support 6 side during casting in the process of forming the cellulose ester film 41 by the solution casting method. For example, the above-described phosphoric acid plasticizer (for example, TPP or BDP). The plasticizer A is unevenly distributed on the metal support 6 side because the side opposite to the metal support 6 of the film (web) is in contact with air on the metal support 6 at the time of casting. It is also considered that the solvent tends to evaporate on the side opposite to the metal support 6 side, and this causes the plasticizer A dissolved in the solvent to approach the metal support 6 side. In the present embodiment, 1 to 20% by weight of plasticizer A is contained with respect to the entire film. Hereinafter, the surface that was on the metal support 6 side of the peeled film will be expressed as B surface, and the surface that is opposite to the metal support 6 will be expressed as A surface. Moreover, when distinguishing the A surface and B surface of the cellulose-ester film 41 on a drawing, as shown in FIG. 3, it is set as the surface 41a (A surface) and the surface 41b (B surface), respectively.

  Unlike the plasticizer A, the silica fine particles are not dissolved in the solvent. Therefore, the silica fine particles do not approach the B surface side as the solvent evaporates on the metal support 6, and the A The concentration of silica fine particles on the surface side becomes larger than the average concentration (for example, 0.1 to 1%) of silica fine particles in the entire film. That is, in the formed cellulose ester film 41, the concentration of the silica fine particles on the A side is larger than the average concentration of the entire film.

  In the present embodiment, in the formed cellulose ester film 41, the hard coat layer 51 is applied to the A side, that is, the side where the concentration of silica fine particles is higher than the average concentration. The reason is as follows.

  The B-side of the formed cellulose ester film 41 is the side in contact with the metal support 6 during film formation. If there is a scratch on the surface of the metal support 6, the scratch is transferred to the B-side. Is done. Then, when the hard coat layer 51 is applied to the B surface, unevenness occurs in the curing shrinkage of the hard coat layer 51 between the portion where the scratch is generated on the B surface and the portion where the scratch is not generated. On the other hand, the A surface side of the cellulose ester film 41 is a surface that does not come into contact with the metal support 6 during film formation, and is not affected by scratches on the surface of the metal support 6. In this embodiment, since the hard coat layer 51 is applied to the A surface side of the cellulose ester film 41, unevenness is caused in the curing shrinkage of the applied hard coat layer 51 due to scratches on the surface of the metal support 6. It can be suppressed from occurring.

  At this time, in distinguishing between the A side and the B side of the cellulose ester film 41, component analysis of the micro range of the cross section of the film is frequently conducted to examine the material composition of the cross section, thereby determining the A side and B side of the film. Since the determination takes a long time, the production efficiency of the hard coat film 60 is lowered. Further, as described later, because of the effect of the plasticizer A, minute scratches on the B surface are alleviated, so it is difficult to determine whether the surface is the B surface or not visually.

  In this respect, since the silica fine particles are not dissolved in the solvent, the A surface of the cellulose ester film 41 on the side where the concentration of the silica fine particles is high can be easily discriminated optically. Therefore, as in the present embodiment, in the cellulose ester film 41, the hard coat layer 51 is reliably formed on the surface A by applying the hard coat layer 51 to the surface side where the concentration of the silica fine particles is larger than the average concentration. (It is possible to prevent the hard coat layer 51 from being mistakenly formed on the opposite surface). Thereby, the fall of the production efficiency of the hard coat film 60 can be suppressed. As for the dispersion state of the silica fine particles in the film, for example, a slight slice of the upper layer is collected from the optical film before coating, and the tomographic image of the optical film is taken with a transmission electron microscope at a magnification of 5000 times, This can be easily confirmed by obtaining the projected area of the particles from the photograph.

  FIG. 4 is a cross-sectional view schematically showing the configuration of the main part of the polarizing plate 22 described above. As shown in the figure, in order to produce the polarizing plate 22, when the hard coat film 60 is bonded with the polarizing film 31 and an adhesive 71 (for example, a water-based adhesive mainly composed of completely saponified polyvinyl alcohol), The adhesive 71 is applied to the surface of the hard coat film 60 opposite to the hard coat layer 51 (the surface 41b of the cellulose ester film 41). The surface 41b is a surface that comes into contact with the metal support 6 when casting the cellulose ester film 41. If the metal support 6 is damaged, the surface is transferred to the surface 41b. .

  However, since the plasticizer A is unevenly distributed on the B surface side (surface 41b side) of the cellulose ester film 41, the plasticizer A imparts flexibility to the surface 41b side. Thereby, since the damage | wound of the surface 41b becomes easy to be eased, it can suppress that the application | coating nonuniformity of the adhesive agent 71 arises in the surface 41b, and can suppress the adhesion defect of the hard-coat film 60 and the polarizing film 31.

  Since the plasticizer A is unevenly distributed on the B surface side, scratches on the surface 41b are alleviated. Therefore, even if the hard coat layer 51 is formed on the B surface side in the cellulose ester film 41 at first glance, the hard coat layer 51 Although it seems that the curing shrinkage unevenness 51 is suppressed, it has been found that the curing shrinkage unevenness cannot be suppressed. This seems to be because the curing shrinkage unevenness of the hard coat layer 51 is more greatly affected by the scratches on the cellulose ester film 41 than the uneven application of the adhesive 71.

  In the present embodiment, as described above, the hard coat layer 51 is formed on the A surface side of the cellulose ester film 41 and the adhesive 71 is applied to the B surface side. The shrinkage unevenness and the application unevenness of the adhesive 71 can be suppressed at the same time. Therefore, when the hard coat film 60 manufactured by the above manufacturing method is applied to the polarizing plate 22 of the liquid crystal display device 20 (when the hard coat film 60 is attached to the polarizing film 31 of the polarizing plate 22), display is performed. It is possible to suppress the occurrence of defects.

  Moreover, when the plasticizer A contained in the cellulose ester film 41 is less than 1% by weight, the flexibility of the application surface side (B surface side) of the adhesive 71 is lowered, and uneven application of the adhesive 71 is suppressed. It becomes difficult. On the other hand, when the plasticizer A is more than 20% by weight, the plasticizer bleed out easily occurs. Therefore, when the cellulose ester film 41 contains 1 to 20% by weight of the plasticizer A, it is possible to suppress the display defect due to uneven application of the adhesive 71 while suppressing bleeding out.

  In particular, by using a phosphoric acid plasticizer (for example, TPP, BDP) as the plasticizer A described above, the plasticizer A can be reliably placed on the metal support 6 side during casting in the process of forming the cellulose ester film 41. It can be unevenly distributed, and flexibility can be reliably imparted to the surface 41b on the metal support 6 side to which the adhesive 71 is applied.

  By the way, it is desirable that the thickness of the hard coat layer 51 applied to the A surface side of the cellulose ester film 41 is 0.5 μm or more and 10 μm or less. When the hard coat layer 51 is thinner than 0.5 μm, it is difficult to impart the necessary hardness to the hard coat layer 51. On the other hand, when the hard coat layer 51 is thicker than 10 μm, the hard coat layer 51 is easily cracked when the hard coat film 60 is wound around the winding core. Therefore, when the thickness of the hard coat layer 51 is not less than 0.5 μm and not more than 10 μm, the generation of cracks during winding can be suppressed while imparting the necessary hardness to the hard coat layer 51. Further, if the thickness of the hard coat layer is 0.7 μm or more and 9 μm or less, it is more preferable in that generation of cracks can be surely suppressed while providing the hard coat layer 51 with sufficient hardness.

  The cellulose ester film 41 may contain 1% by weight or more of a plasticizer B (second plasticizer) different from the plasticizer A described above. In this case, the total amount of the plasticizer A and the plasticizer B in the cellulose ester film 41 is desirably 20% by weight or less.

  When the cellulose ester film 41 contains 1% by weight or more of the plasticizer B, the whole cellulose ester film 41 can be given flexibility and the whole film can be given flexibility. Moreover, when the total amount of the plasticizer A and the plasticizer B in the cellulose ester film 41 is 20% by weight or less, bleeding out of at least one of the plasticizer A and the plasticizer B can be suppressed.

  At this time, the plasticizer B is desirably the phthalate ester-based or polyhydric alcohol ester-based plasticizer described above. With such a plasticizer, it is possible to reliably obtain the above-described effect that gives flexibility to the entire film.

<Example>
Hereinafter, examples of the present embodiment will be described, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless there is particular notice, it shall represent "mass part" or "mass%".

<Example 1>
(Production of cellulose ester film)
-Adjustment of silicon dioxide dispersion Aerosil R812 (Nippon Aerosil Co., Ltd.) 10 parts by mass (average diameter of primary particles 7 nm)
90 parts by mass of ethanol or more was stirred and mixed with a dissolver for 30 minutes, and then dispersed with Manton Gorin. 88 parts by mass of methylene chloride was added to the silicon dioxide dispersion while stirring, and the mixture was stirred and mixed for 30 minutes with a dissolver to prepare a silicon dioxide dispersion dilution. It filtered with the fine particle dispersion | distribution dilution liquid filter (Advantech Toyo Co., Ltd .: Polypropylene wind cartridge filter TCW-PPS-1N).

<Preparation of dope composition>
(Cellulose ester resin)
90 parts by mass of cellulose triacetate A (cellulose triacetate synthesized from linter cotton, acetyl group substitution degree 2.88, Mn = 14000) (additive)
X-1 5 parts by mass X-12 4 parts by mass (UV absorber)
TINUVIN 928 (manufactured by BASF Japan Ltd.) 3 parts by mass (fine particles)
Silicon dioxide dispersion dilution 4 parts by mass (solvent)
Methylene chloride 432 parts by mass Ethanol 38 parts by mass The above was put into a sealed container, heated and stirred, and dissolved completely. Azumi filter paper No. Azumi filter paper No. 24 was used to prepare a dope (dope composition 1).

Next, using the belt casting apparatus (manufacturing apparatus in FIG. 1), the above dope was uniformly cast on a stainless steel band support as the metal support 6. And with the stainless steel band support body, the solvent was evaporated until the amount of residual solvents became 100%, and the web was peeled from the stainless steel band support body. The cellulose ester film web was evaporated at 35 ° C., slit to 1.15 m width, and dried at a drying temperature of 140 ° C. while being stretched 1.15 times in the TD direction (film width direction) with a tenter. I let you. Then, after being dried for 15 minutes while being transported in a drying apparatus 11 at 120 ° C. by a large number of rollers, slitting to a width of 1.3 m, knurling processing of a width of 10 mm and a height of 5 μm on both ends of the film, Winding up to obtain a cellulose ester film. The film thickness of the cellulose ester film was 25 μm, and the winding length was 5000 m. The content of the phosphoric acid plasticizer (plasticizer A) in the cellulose ester film was 9% by weight, and the content of the phthalate ester plasticizer (plasticizer B) was 2% by weight. . The phthalate ester plasticizers are the compounds X-1 and X-12.

  In addition, the draw ratio of MD direction computed from the rotational speed of a stainless steel band support body and the driving speed of a tenter was 1.01 times.

[Preparation of hard coat film]
On the surface A of the cellulose ester film produced above, the following hard coat layer composition filtered through a polypropylene filter having a pore size of 0.4 μm was applied using an extrusion coater, and the constant rate drying section temperature was 50 ° C., After drying at a reduced-rate drying section temperature of 50 ° C., while purging with nitrogen so that the atmosphere has an oxygen concentration of 1.0% by volume or less, the illuminance of the irradiated part is 100 mW / cm ² using an ultraviolet lamp, and the irradiation amount is The coating layer was cured at 0.2 J / cm ² to form a hard coat layer with a dry film thickness of 7 μm, and wound up to an air layer thickness of 4 μm to produce a roll-shaped hard coat film.

  In this case, the A and B sides of the cellulose ester film were determined by taking a slice of the cellulose ester film, taking a tomographic photograph of the cellulose ester film with a transmission electron microscope at a magnification of 5000 times, and then obtaining particles from the tomographic photograph. By observing the projected area, the surface having a larger amount of particles was simply determined as the A plane.

<< Hardcoat layer composition >>
<Preparation of fluorine-siloxane graft polymer>
The commercial name of the raw material used for the preparation of the fluorine-siloxane graft polymer is shown.

Radical polymerizable fluororesin (A): Cefal coat CF-803 (hydroxyl value 60, number average molecular weight 15,000; manufactured by Central Glass Co., Ltd.)
One-end radical polymerizable polysiloxane (B): Silaplane FM-0721 (number average molecular weight 5,000; manufactured by Chisso Corporation)
Radical polymerization initiator: Perbutyl O (t-butylperoxy-2-ethylhexanoate; manufactured by NOF Corporation)
Curing agent: Sumidur N3200 (biuret type prepolymer of hexamethylene diisocyanate; manufactured by Sumika Bayer Urethane Co., Ltd.)

(Synthesis of radical polymerizable fluororesin)
In a glass reactor equipped with a mechanical stirrer, thermometer, condenser and dry nitrogen gas inlet, cefal coat CF-803 (1554 parts by mass), xylene (233 parts by mass), and 2-isocyanatoethyl methacrylate (6 3 parts by mass) and heated to 80 ° C. in a dry nitrogen atmosphere. After reacting at 80 ° C. for 2 hours and confirming that the absorption of isocyanate disappeared by the infrared absorption spectrum of the sampled material, the reaction mixture was taken out to obtain 50% by mass of a radically polymerizable fluororesin via a urethane bond. .

(Preparation of fluorine-siloxane graft compound)
In a glass reactor equipped with a mechanical stirrer, thermometer, condenser and dry nitrogen gas inlet, the above synthesized radical polymerizable fluororesin (26.1 parts by mass), xylene (19.5 parts by mass), acetic acid n-butyl (16.3 parts by mass), methyl methacrylate (2.4 parts by mass), n-butyl methacrylate (1.8 parts by mass), lauryl methacrylate (1.8 parts by mass), 2-hydroxyethyl methacrylate (1 .8 parts by mass), FM-0721 (5.2 parts by mass), and perbutyl O (0.1 parts by mass) were heated to 90 ° C. in a nitrogen atmosphere, and held at 90 ° C. for 2 hours. Perbutyl O (0.1 part) was added, and the solution was further maintained at 90 ° C. for 5 hours to obtain a 35 mass% fluorine-siloxane graft compound solution having a weight average molecular weight of 171,000. The weight average molecular weight was determined by GPC (gel permeation chromatography). Moreover, the mass% of the fluorine-siloxane graft compound was calculated | required by HPLC (liquid chromatography).

(Actinic radiation curable resin)
Pentaerythritol tri / tetraacrylate (NK ester A-TMM-3L, manufactured by Shin-Nakamura Chemical Co., Ltd.)
70 parts by mass Trimethylolpropane triacrylate (A-TMPT, manufactured by Shin-Nakamura Chemical Co., Ltd.) 30 parts by mass (photopolymerization initiator)
Irgacure 184 (manufactured by BASF Japan) 6 parts by mass (additive)
Fluorine-siloxane graft compound (35% by mass) 2 parts by mass (solvent)
Propylene glycol monomethyl ether 20 parts by weight Methyl acetate 30 parts by weight Methyl ethyl ketone 70 parts by weight

[Preparation of polarizing plate]
Using the hard coat film and cellulose ester film prepared above, a polarizing plate was prepared as follows.

(A) Production of Polarizing Film What was impregnated with 10 parts by mass of glycerin and 170 parts by mass of water in 100 parts by mass of polyvinyl alcohol (hereinafter abbreviated as PVA) having a saponification degree of 99.95 mol% and a polymerization degree of 2400 After melt-kneading and defoaming, the film was melt-extruded from a T die onto a metal roller to form a film. Then, it dried and heat-processed and obtained the PVA film.

  The obtained PVA film had an average thickness of 25 μm, a moisture content of 4.4%, and a film width of 3 m. Next, the obtained PVA film was continuously processed in the order of preliminary swelling, dyeing, uniaxial stretching by a wet method, fixing treatment, drying, and heat treatment to prepare a polarizing film. That is, the PVA film was preliminarily swollen in water at a temperature of 30 ° C. for 30 seconds, and immersed in an aqueous solution having an iodine concentration of 0.4 g / liter and a potassium iodide concentration of 40 g / liter at a temperature of 35 ° C. for 3 minutes. Subsequently, the film was uniaxially stretched 6 times in a 50% aqueous solution with a boric acid concentration of 4% under the condition that the tension applied to the film was 700 N / m, and the potassium iodide concentration was 40 g / liter and the boric acid concentration was 40 g / liter. Then, it was immersed in an aqueous solution having a zinc chloride concentration of 10 g / liter and a temperature of 30 ° C. for 5 minutes for fixing. Thereafter, the PVA film was taken out, dried with hot air at a temperature of 40 ° C., and further heat-treated at a temperature of 100 ° C. for 5 minutes. The obtained polarizing film had an average thickness of 13 μm, a polarizing performance of a transmittance of 43.0%, a polarization degree of 99.5%, and a dichroic ratio of 40.1.

(B) Production of polarizing plate A polarizing plate was produced by laminating a polarizing film, a cellulose ester film and a hard coat film according to the following steps 1 to 4.

  Process 1: The above-mentioned polarizing film was immersed in the storage tank of the polyvinyl alcohol adhesive agent solution of 2 mass% of solid content for 1-2 seconds.

  Process 2: The cellulose ester film and the hard coat film were subjected to alkali treatment under the following conditions. Next, in Step 1, the polarizing film was immersed in the polyvinyl alcohol adhesive solution. The excess adhesive adhered to the immersed polarizing film is lightly removed, the polarizing film is sandwiched between the cellulose ester film film and the hard coat film, and is wound up so that the air layer thickness is 5 μm. A polarizing plate was produced.

(Alkali treatment)
Saponification step 2.5 mol / L-KOH 50 ° C. 120 seconds Water washing step Water 30 ° C. 60 seconds Neutralization step 10 parts by mass HCl 30 ° C. 45 seconds Water washing step Water 30 ° C. 60 seconds After saponification treatment, water washing, neutralization, water washing in this order Followed by drying at 100 ° C.

Step 3: The laminate was bonded at a speed of about 2 m / min at a pressure of ^{20 to} 30 N / cm ² with two rotating rollers. At this time, care was taken to prevent bubbles from entering.

  Step 4: The sample produced in Step 3 was dried in a dryer at a temperature of 100 ° C. for 5 minutes to produce a roll-shaped polarizing plate.

<Production of liquid crystal display device>
(Durability test evaluation)
The produced roll-shaped polarizing plate was wrapped in an aluminum moisture-proof sheet and stored for 25 days in a thermostatic bath at 50 ° C. and 80% relative humidity assuming long-term transportation. After storage for 25 days, an adhesive layer was provided as follows and then incorporated into a liquid crystal display device to produce a liquid crystal display device.

(Adhesive layer)
A commercially available acrylic pressure-sensitive adhesive is applied to the cellulose ester film of the polarizing plate so that the thickness after drying is 25 μm, and is dried in an oven at 110 ° C. for 5 minutes to form an adhesive layer. A protective film was attached.

(Liquid crystal display device)
Of two pairs of polarizing plates installed with a liquid crystal layer sandwiched between 21.5 inch liquid crystal display devices (IPS226V-PN, LG Electronics Japan Co., Ltd.), the polarizing plate on one side on the viewer side is peeled off, The pressure-sensitive adhesive layer and the liquid crystal cell glass were bonded so that the prepared polarizing plate had the hard coat layer on the viewing side. A liquid crystal display device was manufactured by arranging the transmission axis of the polarizing plate on the observer side and the transmission axis of the polarizing plate on the backlight side to be orthogonal to each other.

<Example 2>
The same as Example 1 except that the content of the plasticizer A in the cellulose ester film of the hard coat film was 1% by weight.

<Example 3>
The same as Example 1 except that the content of the plasticizer A in the cellulose ester film of the hard coat film was 20% by weight.

<Example 4>
The same as Example 1, except that the film thickness of the cellulose ester film of the hard coat film was 15 μm.

<Example 5>
The same as Example 1 except that the film thickness of the cellulose ester film of the hard coat film was changed to 30 μm.

<Example 6>
The same as Example 1 except that the content of the plasticizer B in the cellulose ester film of the hard coat film was 1% by weight.

<Example 7>
The same as Example 1 except that the content of the plasticizer B in the cellulose ester film of the hard coat film was changed to 3% by weight.

<Comparative Example 1>
The same as Example 1 except that the hard coat layer of the hard coat film was applied to the B-side of the cellulose ester film.

<Comparative Example 2>
The same as Example 1 except that the plasticizer A was not included in the cellulose ester film of the hard coat film.

<Comparative Example 3>
The same as Example 1 except that the content of the plasticizer A in the cellulose ester film of the hard coat film was 21% by weight.

<Comparative example 4>
The same as Example 1 except that the film thickness of the cellulose ester film of the hard coat film was 14 μm.

<Evaluation>
The display defects of the liquid crystal display device produced above, the strength of the hard coat film, and the bleed out of the plasticizer were evaluated. The results are shown in Table 1.

Here, the display defects of the liquid crystal display device were visually confirmed and evaluated based on the following criteria.
A: No display defect is detected.
○: Display defects are hardly detected.
Δ: Display defects are detected very rarely, but there is no problem in actual use.
X: Display defects are frequently detected and cannot be used.

Moreover, about the intensity | strength of the hard coat film, it evaluated based on the following references | standards using the tensile tester.
A: Stronger against pulling than the target.
○: Strength to sufficiently achieve the target against pulling.
(Triangle | delta): It is the strength which achieves a target with respect to a tension | pulling.
X: It is weaker than pulling than the target and cannot endure use.

Moreover, about the bleed-out of a plasticizer, after exposing the same thing as the formed cellulose-ester film to the durable conditions of high temperature / humidity, it evaluated visually based on the following references | standards.
A: No occurrence at all.
○: Almost no occurrence.
Δ: Occasionally rare, but no problem in actual use.
X: Occurs frequently and cannot be used.

  From Table 1, in the comparative example 1, since the hard-coat layer was apply | coated to the B surface side of a cellulose-ester film, the display defect has generate | occur | produced frequently. In Comparative Example 2, the hard coat layer is applied to the A side of the cellulose ester film, but since the plasticizer A is not contained, display defects frequently occur. In Comparative Example 3, since the content of the plasticizer A exceeds 20% by weight, the plasticizer A bleeds out frequently. In Comparative Example 4, since the film thickness of the cellulose ester film is as thin as 14 μm, the film strength is not ensured.

  On the other hand, in Examples 1-7, content of the plasticizer A in a cellulose-ester film is 1-20 weight%, the film thickness of a cellulose-ester film is 15-30 micrometers, and a hard-coat layer is a cellulose ester. Since it is applied to the A side of the film, it can be seen that good results are obtained in all evaluation items of display defects, film strength, and bleed out in the liquid crystal display device.

  Next, in the hard coat film of Example 1, the thickness of the hard coat layer applied on the cellulose ester film was changed. More specifically, in Examples 1-1 to 1-5, hard coat films were prepared with the thickness of the hard coat layer being 7 μm, 0.3 μm, 11 μm, 0.7 μm, and 9 μm, respectively. About other conditions, it is the same as that of Example 1 mentioned above. In the hard coat film thus produced, the hardness of the hard coat layer and the occurrence of cracks were evaluated. The results are shown in Table 2.

Here, the hardness of the hard coat layer was evaluated by a pencil hardness test. Specifically, using a test pencil specified by JIS-S6006, in accordance with the pencil hardness evaluation method specified by JIS-K5400, a hard coat layer surface of a hard coat film is formed with a pencil of each hardness using a 500 g weight. The hardness was measured by repeatedly scratching and scratching up to one. And the hardness of the hard-coat layer was evaluated based on the following references | standards. The pencil hardness H was set as the target hardness.
○: The target hardness can be sufficiently achieved.
Δ: Target hardness can be achieved.

Moreover, about the crack of a hard-coat layer, the sample of the hard-coat film was wound around the round bar of diameter 5mm and diameter 10mm, respectively, and the generation | occurrence | production condition of the crack was observed. When the hard coat film was wound around a round bar having a diameter of 10 mm, no crack was generated in the hard coat layer in any of Examples 1-1 to 1-5. On the other hand, when the hard coat film was wound around a round bar having a diameter of 5 mm, cracks occurred in the hard coat layer in some hard coat films. The occurrence of cracks at this time is shown in Table 2 based on the following criteria.
○: When the hard coat film is wound around a round bar having a diameter of 5 mm, a winding mark is formed (no crack is generated in the hard coat layer).
Δ: Cracks occur in the hard coat layer when the hard coat film is wound around a round bar having a diameter of 5 mm.

  From Table 2, when the thickness of the hard coat layer is 0.3 μm (see Example 1-2), the target hardness can be achieved, and when the thickness of the hard coat layer is 0.7 μm or more (Example 1). 1 and 1-3 to 1-5), it is clear that the target hardness can be sufficiently achieved. If the thickness of the hard coat layer is 0.5 μm (between 0.3 μm and 0.7 μm) or more, it can be said that there is a high possibility that the target hardness can be sufficiently achieved.

  On the other hand, when the thickness of the hard coat layer is 11 μm (see Example 1-3), when the hard coat film is wound around a round bar having a diameter of 5 mm, cracks are generated in the hard coat layer. In order to suppress the occurrence, it can be said that the thickness of the hard coat layer needs to be smaller than 11 μm. Moreover, if the thickness of the hard coat layer is 9 μm or less, the occurrence of cracks in the hard coat layer can be reliably suppressed, and the thickness of the hard coat layer should be 10 μm (between 9 μm and 11 μm) or less. Thus, it can be said that there is a high possibility that the occurrence of cracks in the hard coat layer can be suppressed.

  From the above, in order to sufficiently achieve the target hardness of the hard coat layer and suppress the occurrence of cracks in the hard coat layer under severe winding conditions (winding around a round bar having a diameter of 5 mm), the thickness of the hard coat layer The height needs to be larger than 0.3 μm and smaller than 11 μm, desirably 0.5 μm or more and 10 μm or less, and more desirably 0.7 μm or more and 9 μm or less.

  Next, the content of the plasticizer B added to the cellulose ester film of the hard coat film of Example 1 and the total amount of the plasticizer (plasticizer A + plasticizer B) were changed, and the flexibility of the cellulose ester film, and The plasticizer bleed out was evaluated. The results are shown in Table 3.

Here, the flexibility of the film was evaluated based on the following criteria by the touch of the film.
○: There is sufficient breaking strength.
(Triangle | delta): There exists a breaking strength which achieves a target.

Moreover, about the bleeding out of a plasticizer, after exposing a cellulose-ester film to the durable conditions of high temperature / humidity, it evaluated visually based on the following references | standards.
A: No occurrence at all.
○: Almost no occurrence.
Δ: Occasionally rare, but no problem in actual use.
X: Occurs frequently and cannot be used.

  From Table 3, when the content of the plasticizer B is not contained (see Example 1-9), the target breaking strength can be achieved as the flexibility of the film, but in order to sufficiently achieve the breaking strength, It can be said that the content of the plasticizer B is required to be 1% by weight or more. In addition, when the total amount of the plasticizer is 21% by weight (see Example 1-13), since the bleedout of the plasticizer occurs very rarely, in order to reliably suppress the occurrence of bleedout, the plasticizer It can be said that the total amount of is required to be 20% by weight or less.

  In addition, although the example which applied the hard coat film to the polarizing plate of a liquid crystal display device was demonstrated above, the hard coat film manufactured with the manufacturing method of this embodiment is a film which protects the surface of a touch panel in addition to this. It can also be used as a glass scattering prevention film on the surface of an image display device.

  INDUSTRIAL APPLICABILITY The present invention can be used for manufacturing, for example, a hard coat film attached to a polarizing film of a polarizing plate of a liquid crystal display device or a hard coat film attached to a substrate surface of a touch panel or an image display device.

6 Metal support (support)
41 Cellulose ester film (thin film optical film)
41a surface 51 hard coat layer 60 hard coat film

Claims (4)

Silica fine particles as a matting agent containing 1 to 20% by weight of a phosphoric acid type plasticizer as a plasticizer which is formed by a solution casting method and has a characteristic of being unevenly distributed on the support side during casting in the film forming process A thin film cellulose ester film having a film thickness of 15 μm or more and 30 μm or less, wherein a hard coat layer is applied to the surface on the side where the concentration of the silica fine particles is larger than the average concentration with respect to the entire thin film cellulose ester film. A method for producing a hard coat film. The method for producing a hard coat film according to claim 1, wherein a thickness of the hard coat layer is not less than 0.5 μm and not more than 10 μm. When the plasticizer is the first plasticizer,
The thin film cellulose ester film contains 1% by weight or more of a second plasticizer different from the first plasticizer,
The method for producing a hard coat film according to claim 1 or 2, wherein the total amount of the first plasticizer and the second plasticizer in the thin film cellulose ester film is 20% by weight or less. The method for producing a hard coat film according to claim 3, wherein the second plasticizer is a phthalic acid-based or polyhydric alcohol ester-based plasticizer.

Images