JP2017140799A - Transparent laminated film, transparent conductive film, and touch panel having the same and method for producing transparent laminated film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transparent laminated film having excellent surface smoothness and transparency and having an index matching layer having excellent adhesiveness to a transparent electrode layer and a transparent conductive film and a touch panel having the transparent laminated film and to provide a method for producing a transparent laminated film capable of forming the index matching layer by a single wet coating process.SOLUTION: There is provided a transparent laminated film 15a having an index matching layer 16 obtained by laminating a high refractive index layer 20 and a low refractive index layer 21 in this order on one surface of a transparent substrate 22, where the arithmetic average roughness (Ra) at a microregion having a side of 1 μm square is less than 0.7 nm/μm square, the reflectance of light having a wavelength of 220 to 280 nm is 3.3 to 6.5% and the coefficient of variation of the average reflectance of light having a wavelength of 220 to 280 nm is 15% or less.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a transparent laminated film having an index matching layer on a transparent substrate, a transparent laminated film, a transparent conductive film and a touch panel provided with the transparent laminated film, and a method for producing the transparent laminated film.

  As a display device of an electronic device, a touch panel configured by bonding a transparent conductive film to the surface of a polarizing plate of a liquid crystal display panel is widely used. The transparent conductive film is a transparent laminated film composed mainly of a transparent substrate, and transparent electrodes made of a transparent conductive material such as ITO are provided in a matrix. Optical adjustment called index matching layer (hereinafter referred to as “IM layer”) is used for transparent conductive film to adjust the refractive index difference between the region with and without the transparent electrode and make the pattern of the transparent electrode difficult to see. A layer may be provided.

  In Patent Document 1, an IM layer is formed by laminating a high refractive index layer and a low refractive index layer a plurality of times by dry coating on a hard coat layer laminated on a transparent substrate, and then a transparent electrode layer A transparent conductive film in which is laminated is described. In Patent Document 1, since the IM layer is laminated by dry coating, it is difficult to produce a transparent electrode film having a uniform IM layer over a wide area. Moreover, since the coating process for forming the IM layer is performed a plurality of times, there are problems that the manufacturing cost increases and the yield decreases.

  Patent Document 2 describes a transparent conductive material in which a high refractive index layer and a low refractive index layer are formed by wet coating. Even in this method, it is necessary to coat and form the high refractive index layer and the low refractive index layer separately, so that the coating process becomes longer and drastically improves the production cost and yield. It is not possible. Furthermore, since the low refractive index layer is as thin as 20 to 120 nm, it is difficult to control the film thickness by wet coating, and as a result, there is a problem that the film thickness tends to be nonuniform.

Japanese Patent No. 4666616 JP 2003-80624 A Japanese Patent No. 5309597

  In Patent Document 3, a low refractive index particle whose surface is modified with a fluorine chain is used as one of two types of inorganic particles, and the surface of the low refractive index particles is unevenly distributed due to the difference in surface free energy between the two types of inorganic particles. Thus, a method for producing a low refractive index layer and a high refractive index layer in a single coating process is described.

  However, in the method of Patent Document 3, since the fine particles are used for the low refractive index layer, the surface smoothness of the IM layer is impaired. Further, the compatibility with other binders and solvents is lowered by the fluoro group, and a sea-island structure is formed, and surface roughness and coating whitening are likely to occur. Furthermore, since there is a fluoro group having poor compatibility with other molecules on the surface, there is also a problem that the adhesion of the transparent electrode layer is lowered.

  Therefore, the present invention provides a transparent laminated film including an index matching layer having excellent surface smoothness and transparency and excellent adhesion to the transparent electrode layer, a transparent conductive film and a touch panel including the same, and the index. It aims at providing the manufacturing method of the transparent laminated | multilayer film which can form a matching layer by one wet coating process.

  The present invention provides a transparent laminated film having an index matching layer in which a high refractive index layer and a low refractive index layer are laminated in this order on one surface of a transparent substrate, and an arithmetic average in a minute region having a side of 1 μm square. The roughness (Ra) is less than 0.7 nm / μm □, the reflectance of light of 220 to 280 nm is 3.3 to 6.5%, and the variation coefficient of the average reflectance of light of 220 to 280 nm is 15 % Or less.

ここで、Ｒ^１は、水素またはメチル基のいずれかであり、Ｒ^２は、炭素数１〜９のポリエーテルまたはアルキルである。 The present invention also relates to a method for producing a transparent laminated film having an index matching layer in which a high refractive index layer and a low refractive index layer are laminated in this order on one surface of a transparent substrate, On one surface of the base material, a high-refractive-index fine particle, an acrylic monomer, a leveling agent, a photopolymerization initiator, a coating liquid containing a solvent is applied, and an index matching layer is formed by photocuring the coating film. The acrylic monomer has at least one of a urethane bond, a hydroxyl group, an aromatic ring, an amino group, a carboxyl group, and a phosphate ester, and the leveling agent has a repeating structure represented by the following general formula (1). Acrylic polymer.

Here, R ¹ is either hydrogen or a methyl group, and R ² is a C 1-9 polyether or alkyl.

  ADVANTAGE OF THE INVENTION According to this invention, it is excellent in surface smoothness and transparency, and the transparent laminated film provided with the index matching layer excellent in adhesiveness with a transparent electrode layer, the transparent conductive film and touch panel provided with this, and the said index matching The manufacturing method of the transparent laminated film which can form a layer by one wet coating process can be provided.

Sectional drawing which shows the structural example of an image display apparatus provided with a touch panel. Sectional drawing which shows an example of the laminated constitution of the laminated film used for the transparent conductive film shown in FIG. Sectional drawing which shows another example of the laminated constitution of the laminated film used for the transparent conductive film shown in FIG. The graph which shows the reflection spectrum of the transparent laminated film which concerns on Example 1 The graph which shows the reflection spectrum of the transparent laminated film which concerns on Example 2 The graph which shows the reflection spectrum of the transparent laminated film which concerns on the comparative example 2 The graph which shows the reflection spectrum of the transparent laminated film which concerns on the comparative example 7

  FIG. 1 is a cross-sectional view illustrating a configuration example of an image display device including a touch panel.

  The image display device 1 includes an image display panel 2, a touch panel 3 bonded to the image display panel 2 via an adhesive layer 8, and a cover glass 12 bonded to the surface of the touch panel 3 via an adhesive layer 11. . The upper side in FIG. 1 corresponds to the front side (viewed side) of the image display device 1, and the lower side in FIG.

  The image display panel 2 includes a backlight 4, a polarizing plate 5, a liquid crystal panel 6, and a polarizing plate 7 in order from the back side of the image display device 1. The touch panel 3 is configured by laminating transparent conductive films 9 a and 9 b having transparent electrodes via an adhesive layer 10. The polarizing plate 7 of the image display panel 2 and the transparent conductive film 9 a of the touch panel 3 are bonded together by an air gap method through an adhesive layer 8 provided only on the peripheral edge of the polarizing plate 7. The above-mentioned adhesive layers 8, 10 and 11 are made of, for example, a transparent optical adhesive film (OCA; Optical Clear Adhesive film).

  FIG. 2 is a cross-sectional view showing an example of a layer structure of a laminated film used for the transparent conductive film shown in FIG.

  The transparent conductive films 9a and 9b shown in FIG. 2 include a transparent laminated film 15a and a transparent conductive layer 23 laminated on the transparent laminated film 15a. The transparent laminated film 15 a includes a transparent base material 22 and an index matching layer (IM layer) 16 laminated on one surface of the transparent base material 22. The IM layer 16 is configured by laminating a high refractive index layer 20 and a low refractive index layer 21 in order from one surface side of the transparent substrate 22. The transparent conductive layer 23 is made of a transparent conductive material, and is laminated on the IM layer 16 (low refractive index layer 21) of the transparent laminated film 15a. Although not shown, the transparent conductive layer 23 is patterned into a predetermined shape, and a plurality of transparent electrodes arranged in a matrix are formed.

  The transparent conductive layer 23 is formed using a transparent conductive material having a refractive index of 1.7 to 2.2, such as ITO (Indium Tin Oxide), indium oxide, zinc oxide, tin oxide, and titanium oxide. The film thickness of the transparent conductive layer 23 is preferably 10 to 30 nm. If the film thickness of the transparent conductive layer 23 is less than 10 nm, the resistance value of the transparent conductive layer 23 becomes too small to function as a transparent electrode. On the other hand, when the film thickness of the transparent conductive layer 23 exceeds 30 nm, the transmittance of the transparent conductive layer 23 decreases.

  The method for forming the transparent conductive layer 23 is not particularly limited, but can be formed by sputtering, vacuum deposition, ion plate, chemical vapor deposition (CVD), or the like. When the transparent conductive layer 23 is formed of ITO, annealing is performed at about 100 to 200 ° C. after the film formation in order to crystallize the ITO.

  Here, in the transparent laminated film 15a according to the present embodiment, the arithmetic average roughness (Ra) of the 1 μm square area on the surface of the IM layer 16 is less than 0.7 nm / μm □. Since the arithmetic average roughness (Ra) of the surface of the IM layer 16 is less than 0.7 nm / μm □, the surface smoothness of the IM layer 16 is excellent, and the adhesion of the transparent electrode layer 23 can be improved. Moreover, the reflectance of 220-280 nm light of the transparent laminated film 15a is in the range of 3.3-6.5%. By setting the reflectance of light of 220 to 280 nm within the range of 3.3 to 6.5%, coloring after the formation of the transparent electrode layer 23 can be suppressed. Furthermore, the variation coefficient of the average reflectance of light of 220 to 280 nm measured at a plurality of locations on the transparent laminated film 15a is 15% or less. The coefficient of variation is an index representing the variation in the film thickness of the IM layer 16, and the average reflectance of light at 220 to 280 nm is obtained for a plurality of locations on the transparent laminated film 15 a, and the standard of the obtained average reflectance at the plurality of locations is obtained. It is defined as a value obtained by dividing the deviation by the average value of a plurality of obtained positions. When the variation coefficient of the average reflectance of 220 to 280 nm is 15% or less, the film thickness of the IM layer 16 becomes almost uniform in the entire transparent laminated film 15a, and coloring after the formation of the transparent electrode layer 23 can be suppressed. .

  Hereinafter, the detail of each layer with which the transparent laminated film 15a is provided is demonstrated.

(Transparent substrate)
The transparent substrate 22 is a film that becomes a base of the transparent laminated film 15a, and is formed of a material that is excellent in visible light transmittance. Examples of the material for forming the transparent substrate 22 include polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate, polyamides such as nylon 6 and nylon 66, polyimide, polyarylate, polycarbonate, polyacrylate, Transparent resins such as polyethersulfone and polysulfone, and inorganic glass can be used. The transparent substrate 22 may be a composite film in which a plurality of materials are laminated. Although the thickness of a transparent base material is not specifically limited, It is preferable to set it as 10-200 micrometers.

(IM layer)
The IM layer 16 is an optical adjustment layer provided in order to reduce the difference in optical characteristics between the portion with and without the transparent electrode. By providing the IM layer 16, it is difficult to visually recognize the pattern of the transparent electrode. Can do. As described above, the IM layer 16 has a layer configuration of the high refractive index layer 20 and the low refractive index layer 21 in order from the transparent substrate 22 side.

  In the present embodiment, the IM layer 16 is formed by applying an IM layer forming coating solution containing highly refractive fine particles, an acrylic monomer, a leveling agent, a photopolymerization initiator, and a solvent to the transparent substrate 22 and photocuring it. It is formed.

The coating method of the IM layer forming coating liquid is not particularly limited, and is a flow coating method, a spray coating method, a roll coating method, a gravure roll coating method, an air doctor coating method, a blade coating method, a wire doctor coating method, a knife coating. Known wet coating methods such as a method, a reverse coating method, a transfer roll coating method, a micro gravure coating method, a kiss coating method, a cast coating method, a slot orifice coating method, a calendar coating method, and a die coating method can be employed. As a method for curing the coating film of the coating liquid, for example, ultraviolet irradiation or electron beam irradiation can be used. In the case of ultraviolet irradiation, a high pressure mercury lamp, a halogen lamp, a xenon lamp, a fusion lamp, or the like can be used. The amount of ultraviolet irradiation is usually about 100 to 800 mJ / cm ² .

  As the high refractive index fine particles, metal oxides such as zirconium oxide, titanium oxide, niobium oxide, antimony trioxide, antimony pentoxide, tin oxide, ATO, indium oxide, ITO, and zinc oxide can be used. Among these high refractive index materials, zirconium oxide is more preferable because it has a relatively high refractive index and can improve the transparency of the IM layer 16. The particle diameter of the highly refractive fine particles is 10 to 100 nm. In order to improve the bonding strength with the binder resin, it is more preferable to use a high refractive index fine particle whose surface is modified with an organic chain. The organic chain that modifies the surface of the high-refractive-index fine particles only needs to have a chemical structure having at least one of an ester bond, a urethane bond, a hydroxyl group, an aromatic ring, an amino group, a carboxyl group, and a phosphate ester. . Among these, it is preferable that the organic chain that modifies the surface of the high refractive index fine particles has an ester bond having an acryloyl group. When the organic chain on the surface of the high refractive index fine particle has an acryloyl group, the high refractive index fine particle is bonded to the acrylic monomer, and desorption from the acrylic monomer is suppressed. By having the chemical structure exemplified here, the surface free energy of the high refractive index fine particles can be made larger than that of the leveling material.

  The acrylic monomer is a resin that serves as a binder. In this embodiment, the acrylic monomer is a photocurable acrylate or methacrylate, and includes at least one of a urethane bond, a hydroxyl group, an aromatic ring, an amino group, a carboxyl group, and a phosphate ester in addition to an ester bond. Those having a chemical structure can be used. In this case, the surface free energy of the acrylic monomer can be made larger than that of the leveling material.

  Leveling agents are oil droplets in the process of forming a film and are oriented on the surface of the film, making the evaporation of the solvent from the surface of the film uniform and smoothing the surface by reducing the change in surface tension. Is an additive. As the leveling agent, an acrylic polymer represented by the following general formula (1) can be used. The surface free energy of the leveling agent represented by the following general formula (1) is smaller than the above-described high refractive index fine particles and acrylic monomers.

ここで、Ｒ^１は、水素またはメチル基のいずれかであり、Ｒ^２は、炭素数１〜９のポリエーテルまたはアルキルである。ｎは、１５〜２００の整数である。

Here, R ¹ is either hydrogen or a methyl group, and R ² is a C 1-9 polyether or alkyl. n is an integer of 15 to 200.

  The compounding quantity of the acrylic polymer shown in General formula (1) is 0.2 to 1.3%. The thickness of the low refractive index layer can be adjusted by the blending amount of the acrylic polymer represented by the general formula (1), and the thickness of the low refractive index layer increases as the blending amount of the acrylic polymer represented by the general formula (1) increases. growing. When the blending amount of the acrylic polymer is below the lower limit, the thickness of the low refractive index layer is less than 20 nm, and the reflectance of light at 220 to 280 nm exceeds the above-mentioned range of 3.3 to 6.5%. In this case, since the transparent conductive film exhibits a yellow color after the formation of the transparent electrode layer 23, it is not preferable. On the other hand, when the blending amount of the acrylic polymer exceeds the above upper limit value, the thickness of the low refractive index layer becomes too thick, and the reflectance of light at 220 to 280 nm falls below the above-mentioned range of 3.3 to 6.5%. End up. In this case, since the transparent conductive film exhibits a blue color after the formation of the transparent electrode layer 23, it is not preferable.

  The photopolymerization initiator only needs to generate radicals when irradiated with ultraviolet rays. For example, radical polymerization initiators such as acetophenone, benzophenone, thioxanthone, benzoin, and benzoin methyl ether, aromatic diazonium salts Cationic polymerization initiators such as aromatic sulfonium salts, aromatic iodonium salts, and metallocene compounds can be used alone or in combination.

  Solvents include alcohols such as methanol, ethanol, isopropanol, butanol and 2-methoxyethanol, ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone, esters such as methyl acetate, ethyl acetate and butyl acetate, and diisopropyl ether. Ethers, glycols such as ethylene glycol, propylene glycol, hexylene glycol, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, glycol ethers such as ethyl cellosolve, butyl cellosolve, ethyl carbitol, butyl carbitol, hexane, heptane, Aliphatic hydrocarbons such as octane, halogenated hydrocarbons, aromatic hydrocarbons such as benzene, toluene, xylene, N-methylpyrrole Down, dimethylformamide and the like either alone or in combination can be used.

  In the coating film before curing, the components in the film are separated so that the free energy on the coating film surface becomes small. In this embodiment, the surface free energy of the component (leveling material) to be segregated on the surface is relatively small, and the surface free energy of the component (high refractive index fine particles, acrylic monomer) to be present in the bulk is relatively Control phase separation by increasing it. That is, when a coating liquid containing a component having a relatively high surface free energy and a component having a relatively low surface free energy is applied on the transparent substrate, a leveling agent having a relatively small surface free energy is oriented on the surface layer. In this state, when the coating film is irradiated with ultraviolet rays or ionizing radiation to cause a photopolymerization reaction, the coating film is cured while the leveling agent having a low refractive index is unevenly distributed on the surface layer. As a result, a low refractive index layer having a relatively low refractive index is formed on the surface layer side, and a high refractive index layer in which high refractive index fine particles are unevenly distributed is formed on the transparent substrate side. Can function as.

  In addition, since both the acrylic monomer and the leveling agent contained in the IM layer forming coating solution are acrylic, the affinity is high, and the formation of a sea-island structure is suppressed during curing. As a result, the surface smoothness and transparency are excellent, and the adhesion with the transparent electrode layer 23 is also improved.

  FIG. 3 is a cross-sectional view showing another example of the layer structure of the laminated film used in the transparent conductive film shown in FIG.

  The laminated film 15b shown in FIG. 3 further includes a hard coat layer 24 in addition to the layer configuration of the laminated film 15a shown in FIG. The hard coat layer 24 is laminated on the other surface of the transparent substrate 22 (the surface opposite to the surface on which the IM layer 16 is laminated).

  The hard coat layer can be formed by a wet coating method. For example, the hard coat layer can be formed by applying a hard coat layer forming coating solution containing an acrylate monomer and a photopolymerization initiator and curing the coating film by photopolymerization. Examples of the acrylate monomer include trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, propoxylated trimethylolpropane triacrylate, tris such as tris 2-hydroxyethyl isocyanurate triacrylate, glycerin triacrylate, pentaerythritol triacrylate. Trifunctional acrylate compounds such as acrylate, dipentaerythritol triacrylate, ditrimethylolpropane triacrylate, pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, dipentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, ditrimethylolpropane pentaacrylate Dipentaellis Hexaacrylate, and ditrimethylolpropane polyfunctional acrylate compounds of trifunctional or more such hexaacrylate, polyfunctional acrylate compounds some of these acrylate was substituted with an alkyl group and ε- caprolactone.

  Examples of the photopolymerization initiator include 2,2-ethoxyacetophenone, 1-hydroxycyclohexyl phenyl ketone, dibenzoyl, benzoin, benzoin methyl ether, benzoin ethyl ether, p-chlorobenzophenone, p-methoxybenzophenone, Michler ketone, acetophenone. , 2-chlorothioxanthone and the like. You may use these individually or in combination of 2 or more types.

In addition, when performing layer formation by wet coating method, flow coating method, spray coating method, roll coating method, gravure roll coating method, air doctor coating method, blade coating method, wire doctor coating method, knife coating method, reverse coating method The coating liquid is applied by a known wet coating method such as transfer roll coating method, micro gravure coating method, kiss coating method, cast coating method, slot orifice coating method, calendar coating method, die coating method, etc. Harden. As a method for curing the coating film of the coating liquid, for example, ultraviolet irradiation, heating, or the like can be used. In the case of ultraviolet irradiation, a high pressure mercury lamp, a halogen lamp, a xenon lamp, a fusion lamp, or the like can be used. The amount of ultraviolet irradiation is usually about 100 to 800 mJ / cm ² .

  When the layer is formed by the dry coating method, a physical vapor deposition method (PVD method) or a chemical vapor deposition method (CVD method) such as a vacuum deposition method, a sputtering method, an ionization deposition method, or an ion beam method can be used.

  The transparent laminated films 15a and 15b shown in FIGS. 2 and 3 continue the IM layer 16 against one surface of the transparent substrate 22 while unwinding and transporting the transparent substrate 22 wound in a roll shape. The transparent substrate 22 after the IM layer 16 is formed can be formed by a roll-to-roll method. Thereafter, as shown in FIG. 3, when the hard coat layer 24 is provided, the hard coat layer 24 is formed on the other surface of the transparent substrate 22 while the rolled transparent substrate 22 is unwound and conveyed again. .

  Examples in which the transparent laminated film according to the present invention is specifically implemented will be described below.

Example 1
The IM layer forming coating solution 1 having the following composition was applied to one surface of a 100 μm thick polyethylene terephthalate film so that the film thickness after drying was 2.0 μm and dried. Then, the coating film was hardened by irradiating with an ultraviolet ray at an irradiation dose of 200 mJ / cm ² using an ultraviolet irradiation device to form an IM layer.

[IM layer forming coating solution 1]
・ High refractive index fine particles: Zirconia fine particles (Zircoster, Nippon Shokubai Co., Ltd.) 25 parts by weight Acrylic monomer: Pentaerythritol triacrylate hexamethylene diisocyanate Urethane prepolymer (UA-306H, Kyoeisha Chemical Co., Ltd.) 23 parts by weight Agent: 1-hydroxy-cyclohexyl-phenyl-ketone (Irgacure (registered trademark) 184, BASF) 1.5 parts by weight Leveling agent: Acrylic polymer (TEGO (registered trademark) Flow 370, Evonik) 0.5 parts by weight Solvent 1: 25 parts by weight of propylene glycol monomethyl ether (PGME) Solvent 2: 25 parts by weight of methyl isobutyl ketone (MIBK)

Next, a hard coat layer-forming coating solution having the following composition was applied to the other surface of the polyethylene terephthalate film so that the film thickness after drying was 1.0 μm and dried. Then, the coating film was hardened by performing ultraviolet irradiation with an irradiation dose of 200 mJ / cm ² using an ultraviolet irradiation device to form a hard coat layer, and the transparent laminated film according to Example 1 was obtained.

[Coating liquid for forming hard coat layer]
Silica filler: Organosilica sol MEK-AC-4130Y (Nissan Chemical Co., Ltd.) 2.5 parts by weight Acrylic monomer: Pentaerythritol triacrylate (A-TMM-3L, Shin-Nakamura Chemical Co., Ltd.) 44.5 parts by weight Photopolymerization initiator: 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (TPO, manufactured by BASF) 3 parts by weight, solvent 1: 25 parts by weight of acetone, solvent 2: propylene glycol monomethyl ether (PGME) 25 parts by weight Part

(Example 2)
A transparent laminated film according to Example 2 was produced in the same manner as in Example 1 except that the IM layer forming coating solution 2 having the following composition was used.

[IM layer forming coating solution 2]
High refractive index fine particles: Zirconia fine particles (Zircoster, Nippon Shokubai Co., Ltd.) 25 parts by weight Acrylic monomer: Pentaerythritol triacrylate isophorone diisocyanate Urethane prepolymer (UA-306I, Kyoeisha Chemical Co., Ltd.) 22.5 parts by weight Photopolymerization Initiator: 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (TPO, BASF) 1.5 parts by weight Leveling agent: Acrylic polymer (Polyflow No. 77, Kyoeisha Chemical Co., Ltd.)
1.0 part by weight / solvent 1: 25 parts by weight of propylene glycol monomethyl ether (PGME) / solvent 2: 25 parts by weight of methyl isobutyl ketone (MIBK)

(Example 3)
A transparent laminated film according to Example 3 was produced in the same manner as in Example 1 except that the IM layer forming coating solution 3 having the following composition was used.

[IM layer forming coating solution 3]
High refractive index fine particles: Zirconia fine particles (Zircoster, Nippon Shokubai Co., Ltd.) 25 parts by weight Acrylic monomer: Pentaerythritol triacrylate (Biscoat # 300, Osaka Organic Chemical Industries, Ltd.) 23 parts by weight Photoinitiator: 1- Hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184, BASF) 1.5 parts by weight Leveling agent: Acrylic polymer (BYK-350, BYK) 0.5 parts by weight Solvent 1: Propylene glycol monomethyl ether (PGME) 25 Part by weight / solvent 2: 25 parts by weight of methyl isobutyl ketone (MIBK)

Example 4
A transparent laminated film according to Example 4 was produced in the same manner as in Example 1 except that the IM layer forming coating solution 4 having the following composition was used.

[IM layer forming coating solution 4]
・ High refractive index fine particles: Zirconia fine particles (Zircoster, Nippon Shokubai Co., Ltd.) 25 parts by weightAcrylic monomer: KAYAMAAR PM-2 (Nippon Kayaku Co., Ltd.) 22.5 parts by weightPhotopolymerization initiator: 2, 4, 6 -Trimethylbenzoyl-diphenyl-phosphine oxide (TPO, BASF) 1.5 parts by weight Leveling agent: Acrylic polymer (BYK-354, BYK) 1.0 parts by weight Solvent 1: Propylene glycol monomethyl ether (PGME) 25 parts by weight / solvent 2: 25 parts by weight of methyl isobutyl ketone (MIBK)

(Example 5)
A transparent laminated film according to Example 5 was produced in the same manner as in Example 1 except that IM layer forming coating solution 5 having the following composition was used.

[IM layer forming coating solution 5]
・ High refractive index fine particles: 25 parts by weight of zirconia fine particles (Zircoster, Nippon Shokubai Co., Ltd.) Acrylic monomer: Carboxylic acid-containing urethane acrylate oligomer (DAUA-167, Kyoeisha Chemical Co., Ltd.) 22.5 parts by weight 1-hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184, BASF) 1.5 parts by weight leveling agent: acrylic polymer (TEGO Flow 370, Evonik)
1.0 part by weight / solvent 1: 25 parts by weight of propylene glycol monomethyl ether (PGME) / solvent 2: 25 parts by weight of methyl isobutyl ketone (MIBK)

(Example 6)
A transparent laminated film according to Example 6 was produced in the same manner as in Example 1 except that the IM layer forming coating solution 6 having the following composition was used.

[IM layer forming coating solution 6]
・ High refractive index fine particles: 25 parts by weight of zirconia fine particles (Zircoster, Nippon Shokubai Co., Ltd.) ・ Acrylic monomer: Pentaerythritol triacrylate (Biscoat # 300, Osaka Organic Chemical Co., Ltd.) 22.5 parts by weight ・ Photopolymerization initiator: 1.5 parts by weight of 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (TPO, BASF) Leveling agent: Acrylic polymer (TEGO Flow 370, Evonik)
1.0 part by weight / solvent 1: 25 parts by weight of propylene glycol monomethyl ether (PGME) / solvent 2: 25 parts by weight of methyl isobutyl ketone (MIBK)

(Example 7)
A transparent laminated film according to Example 7 was produced in the same manner as in Example 1 except that the IM layer forming coating solution 7 having the following composition was used.

[IM layer forming coating solution 7]
・ High refractive index fine particles: Zirconia fine particles (Zircoster, Nippon Shokubai Co., Ltd.) 25 parts by weight ・ Acrylic monomer: KAYAMA PM-2 (Nippon Kayaku Co., Ltd.) 23 parts by weight ・ Photopolymerization initiator: 1-hydroxy-cyclohexyl-phenyl -Ketone (Irgacure 184, BASF) 1.5 parts by weight Leveling agent: Acrylic polymer (Polyflow No. 77, Kyoeisha Chemical Co., Ltd.)
0.5 parts by weight / solvent 1: 25 parts by weight of propylene glycol monomethyl ether (PGME) / solvent 2: 25 parts by weight of methyl isobutyl ketone (MIBK)

(Comparative Example 1)
A transparent laminated film according to Comparative Example 1 was produced in the same manner as in Example 1 except that the IM layer forming coating solution 8 having the following composition was used.

[IM layer forming coating solution 8]
-High refractive index fine particles: Zirconia fine particles (Zircoster, Nippon Shokubai Co., Ltd.) 25 parts by weight-Acrylic monomer: Pentaerythritol triacrylate hexamethylene diisocyanate Urethane prepolymer (UA-306H, Kyoeisha Chemical Co., Ltd.)
23.45 parts by weight-photopolymerization initiator: 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (TPO, BASF) 1.5 parts by weight-leveling agent: acrylic polymer (TEGO Flow 370, Evonik)
0.05 part by weight / solvent 1: 25 parts by weight of propylene glycol monomethyl ether (PGME) / solvent 2: 25 parts by weight of methyl isobutyl ketone (MIBK)

(Comparative Example 2)
A transparent laminated film according to Comparative Example 2 was produced in the same manner as in Example 1 except that the IM layer forming coating solution 9 having the following composition was used.

[IM layer forming coating solution 9]
・ High refractive index fine particles: Zirconia fine particles (Zircoster, Nippon Shokubai Co., Ltd.) 25 parts by weightAcrylic monomer: Pentaerythritol triacrylate isophorone diisocyanate urethane prepolymer (UA-306I, Kyoeisha Chemical Co., Ltd.) 22 parts by weight : 1-hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184, BASF) 1.5 parts by weight Leveling agent: Acrylic polymer (Polyflow No. 77, Kyoeisha Chemical Co., Ltd.)
1.5 parts by weight / solvent 1: 25 parts by weight of propylene glycol monomethyl ether (PGME) / solvent 2: 25 parts by weight of methyl isobutyl ketone (MIBK)

(Comparative Example 3)
A transparent laminated film according to Comparative Example 3 was produced in the same manner as in Example 1 except that the IM layer forming coating solution 10 having the following composition was used.

[IM layer forming coating solution 10]
・ High refractive index fine particles: Zirconia fine particles (Zircoster, Nippon Shokubai Co., Ltd.) 25 parts by weightAcrylic monomer: 1,6-hexanediol diacrylate (Kyoeisha Chemical Co., Ltd.)
23 parts by weight-photopolymerization initiator: 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (TPO, BASF) 1.5 parts by weight-leveling agent: acrylic polymer (TEGO Flow 370, Evonik)
0.5 parts by weight / solvent 1: 25 parts by weight of propylene glycol monomethyl ether (PGME) / solvent 2: 25 parts by weight of methyl isobutyl ketone (MIBK)

(Comparative Example 4)
A transparent laminated film according to Comparative Example 4 was produced in the same manner as in Example 1 except that the IM layer forming coating solution 11 having the following composition was used.

[IM layer forming coating solution 11]
High refractive index fine particles: Zirconia fine particles (Zircoster, Nippon Shokubai Co., Ltd.) 25 parts by weight Acrylic monomer: Pentaerythritol triacrylate (Biscoat # 300, Osaka Organic Chemical Industries, Ltd.) 23 parts by weight Photoinitiator: 1- Hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184, BASF) 1.5 parts by weight Leveling agent: Fluorosurfactant (RS-75, DIC Corporation) 0.5 parts by weight Solvent 1: Propylene glycol monomethyl ether ( 25 parts by weight of PGME / solvent 2: 25 parts by weight of methyl isobutyl ketone (MIBK)

(Comparative Example 5)
A transparent laminated film according to Comparative Example 5 was produced in the same manner as in Example 1 except that the IM layer forming coating solution 12 having the following composition was used.

[Hollow silica having a fluoro group]
In Comparative Example 5, hollow silica having a fluoro group was used as the leveling material. This hollow silica having a fluoro group was prepared according to the “adjustment of low refractive index component (a)” method described in Japanese Patent No. 5309597. Specifically, 2.75 g of methacryloxypropyltrimethoxysilane and 0.34 g of 10% by weight aqueous formic acid solution were mixed with 20 g of throughria TR-113 (made by Catalyst Chemical Industry Co., Ltd .: solid content 20% by weight) which is hollow silica. , And stirred at 70 ° C. for 1 hour. Subsequently, 2.76 g of 2-perfluorooctylethyl acrylate and 0.115 g of 2,2-azobisisobutyronitrile were added, followed by heating and stirring at 90 ° C. for 1 hour. The obtained liquid was diluted with isopropyl alcohol to obtain a leveling material containing hollow silica having a fluoro group.
[IM layer forming coating solution 12]
-High refractive index fine particles: Zirconia fine particles (Zircoster, Nippon Shokubai Co., Ltd.) 25 parts by weight-Acrylic monomer: Pentaerythritol triacrylate (Biscoat # 300, Osaka Organic Chemical Co., Ltd.) 23.45 parts by weight-Photopolymerization initiator: 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (TPO, BASF) 1.5 parts by weight Leveling agent: 1.4 parts by weight of hollow silica having a fluoro group Solvent 1: propylene glycol monomethyl ether (PGME) 24.3 parts by weight / solvent 2: methyl isobutyl ketone (MIBK) 24.3 parts by weight

(Comparative Example 6)
The transparent laminated film according to Comparative Example 6 is obtained by forming a high refractive index layer and a low refractive index by another coating process. Specifically, the coating liquid 1 for forming a high refractive index layer having the following composition was applied on one surface of a polyethylene terephthalate film having a thickness of 100 μm so that the film thickness after drying was 2.0 μm and dried. Then, the coating film was hardened by irradiating with an ultraviolet ray at an irradiation dose of 200 mJ / cm ² using an ultraviolet irradiation device to form a high refractive index layer.

[High refractive index layer forming coating solution 1]
-High refractive index fine particles: Zirconia fine particles (Zircoster, Nippon Shokubai Co., Ltd.) 25 parts by weight-Acrylic monomer: Pentaerythritol triacrylate hexamethylene diisocyanate Urethane prepolymer (UA-306H, Kyoeisha Chemical Co., Ltd.)
23.5 parts by weight Photopolymerization initiator: 1-hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184, BASF) 1.5 parts by weight Solvent 1: 25 parts by weight of propylene glycol monomethyl ether (PGME) Solvent 2: Methyl isobutyl ketone (MIBK) 25 parts by weight

Next, a coating solution for forming a low refractive index layer having the following composition was applied on the formed high refractive index layer so that the film thickness after drying was 22 nm and dried. Then, the coating film was hardened by irradiating with an ultraviolet ray at an irradiation dose of 200 mJ / cm ² using an ultraviolet ray irradiating device to form a low refractive index layer.

[Coating liquid for forming low refractive index layer]
Acrylic monomer: Propoxylation (6) Trimethylolpropane triacrylate (CD501, Sartomer) 0.9 parts by weight Photopolymerization initiator: 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (TPO, BASF) 0.1 parts by weight, solvent 1: ethanol 69.3 parts by weight, solvent 2: diacetone alcohol 29.7 parts by weight

  Next, a hard coat layer was formed on the other surface of the polyethylene terephthalate film by the same method as in Example 1, and a transparent laminated film according to Comparative Example 6 was obtained.

(Comparative Example 7)
The transparent laminated film according to Comparative Example 7 is obtained by omitting the low refractive index layer on the high refractive index layer. Specifically, the coating liquid 2 for forming a high refractive index layer having the following composition was applied on one surface of a polyethylene terephthalate film having a thickness of 100 μm so as to have a film thickness after drying of 2.0 μm and dried. Then, the coating film was hardened by performing ultraviolet irradiation with an irradiation dose of 200 mJ / cm ² using an ultraviolet irradiation device, and a transparent laminated film according to Comparative Example 7 was obtained.

[High refractive index layer forming coating solution 2]
-High refractive index fine particles: Zirconia fine particles (Zircoster, Nippon Shokubai Co., Ltd.) 25 parts by weight-Acrylic monomer: Pentaerythritol triacrylate hexamethylene diisocyanate Urethane prepolymer (UA-306H, Kyoeisha Chemical Co., Ltd.)
23.5 parts by weight Photopolymerization initiator: 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (TPO, BASF) 1.5 parts by weight Solvent 1: propylene glycol monomethyl ether (PGME) 25 parts by weight・ Solvent 2: 25 parts by weight of methyl isobutyl ketone (MIBK)

  About transparent laminated film which concerns on Examples 1-7 and Comparative Examples 1-7, the reflectance of 220-280 nm, the variation coefficient of the average reflectance of 220-280 nm light, the presence or absence of coloring after transparent electrode layer formation, IM layer The arithmetic average roughness (Ra) of the surface, the presence or absence of whitening, the adhesion with the transparent electrode layer, the haze, and the film thickness of the low refractive index layer were evaluated. The evaluation method is shown below.

[Reflectance between 220 and 280 nm]
Using a spectrophotometer (U-4100, Hitachi, Ltd.), the light reflectance is measured while changing the wavelength by 1 nm in the wavelength range of 220 to 280 nm, and the reflectance range (minimum value to maximum value range). )

[Coefficient of variation of average reflectance of light of 220 to 280 nm]
Samples were obtained at intervals of 5 cm in the width direction at each of the winding start portion (inside winding) and winding end portion (outside winding) of the transparent laminated film (width 1550 cm) prepared by roll-to-roll. Next, for each sample, the light reflectance was measured while changing the wavelength by 1 nm in the wavelength range of 220 to 280 nm, and the average reflectance was calculated. And the average value and standard deviation of the average reflectance of a plurality of samples were calculated, and the value obtained by dividing the standard deviation by the average value was calculated as the coefficient of variation.

[Presence or absence of coloring after forming transparent electrode layer]
On the IM layer of the transparent laminated film according to Examples 1 to 7 and Comparative Examples 1 to 7, ITO was formed into a film with a thickness of 22 nm by a sputtering method, and after the film formation, an annealing treatment was performed at 150 ° C. Laminated. After lamination of the transparent electrode layer, the presence or absence of coloring was visually confirmed.

[Arithmetic mean roughness (Ra) of IM layer surface]
The uneven shape of the low refractive index layer was observed using an atomic force microscope (AFM), and the arithmetic average roughness (Ra) in a 1 μm square area was calculated.

[Presence of whitening]
It was visually confirmed whether the transparent laminated film had white haze.

[Adhesion with transparent electrode layer]
On the IM layer of the transparent laminated film according to Examples 1 to 7 and Comparative Examples 1 to 7, ITO was formed into a film with a thickness of 22 nm by a sputtering method, and after the film formation, an annealing treatment was performed at 150 ° C. Laminated. After lamination of the transparent electrode layer, a cross-cut test was performed in accordance with JIS K5600-5-6, and the ratio of the area of the transparent electrode layer remaining without peeling was determined.

[Haze]
Haze was measured according to JIS K 7105 using a haze meter (NDH2000, Nippon Denshoku Industries Co., Ltd.).

[Thickness of low refractive index layer]
Reflection spectroscopy was measured using a spectrophotometer (U-4100, Hitachi, Ltd.), and the film thickness of the low refractive index layer was calculated by simulation using thin film calculation software “Essential Macleod”.

  In Table 1, the composition of the coating liquid used for preparation of the transparent laminated film which concerns on Examples 1-7 and Comparative Examples 1-7 and the evaluation result of the evaluation item mentioned above are shown.

  As shown in Table 1, all of the transparent laminated films according to Examples 1 to 7 were excellent in surface smoothness, transparency, and adhesion with the transparent electrode layer. Moreover, coloring was not seen even if it formed the transparent electrode layer on the IM layer of the transparent laminated film which concerns on Examples 1-7. Furthermore, from the evaluation results of the transparent laminated films according to Examples 1 to 7, according to the method for producing a transparent laminated film according to the present invention, the high refractive index layer and the low refractive index layer are formed by a single coating liquid coating process. It was confirmed that variation in film thickness was suppressed throughout the transparent laminated film.

  On the other hand, the transparent laminated films according to Comparative Examples 1 to 3 have a light reflectance of 220 to 280 nm that is out of the range of 3.3 to 6.5%. It was not suitable for the use of a transparent conductive film.

  In Comparative Examples 4 and 5, since a compound having a fluoro group was used as a leveling agent to be added to the IM layer forming coating solution, the compatibility with the acrylic polymer or the solvent was lowered by the fluoro group, and a sea-island structure was formed. As a result, the smoothness of the surface of the IM layer was lowered, and whitening of the IM layer occurred. Moreover, adhesiveness with a transparent electrode layer was also bad because surface smoothness fell.

  In Comparative Example 6, the high refractive index layer and the low refractive index layer are formed by different coating processes. However, since the film thickness of the low refractive index layer is as thin as about 22 nm, Thickness control was difficult, the film thickness varied, and the variation coefficient of the average reflectance of light of 220 to 280 nm was relatively large. Moreover, in the manufacturing method of the transparent laminated film which concerns on the comparative example 6, in order to form IM layer by two coating processes, manufacturing cost and manufacturing efficiency also worsened.

  Further, in Comparative Example 7, since the low refractive index layer is not provided, the reflectance of light at 220 to 280 nm is out of the range of 3.3 to 6.5%, and yellow is formed after the transparent electrode layer is formed. The film was not suitable for use as a protective film.

  4, 5, 6 and 7 are graphs showing the reflection spectra of the transparent laminated films according to Example 1, Example 2, Comparative Example 2 and Comparative Example 7. FIG. 4 to 7, (a) is a graph plotting the reflectance measured while changing the wavelength by 1 nm in the wavelength range of 200 to 800 nm, and (b) is 200 to 300 nm shown in (a). It is an enlarged view of the range.

  In the reflection spectrum of the transparent laminated film according to Examples 1 and 2 shown in FIGS. 4 and 5, the reflectance of light at 220 to 280 nm is within the range of 3.3 to 6.5%. On the other hand, in the reflection spectrum of the transparent laminated film according to Comparative Example 2 shown in FIG. 6, the reflectance of light at 220 to 280 nm is 3.0 to 3.5%, which is lower than the preferred reflectance. In the reflection spectrum of the transparent laminated film according to Comparative Example 7 shown in FIG. 7, the reflectance of light at 220 to 280 nm is 7.2 to 9.0%, which is higher than the preferred reflectance.

  The present invention can be used for a transparent conductive film used for a touch panel.

DESCRIPTION OF SYMBOLS 1 Image display apparatus 2 Image display panel 3 Touch panel 4 Backlight 5 Polarizing plate 6 Liquid crystal panel 7 Polarizing plate 8 Adhesive layer 9a, 9b Transparent conductive film 10 Adhesive layer 11 Adhesive layer 12 Cover glass 15a, 15b Transparent laminated film 16 Index matching Layer (IM layer)
20 High Refractive Index Layer 21 Low Refractive Index Layer 22 Transparent Base Material 23 Transparent Electrode Layer 24 Hard Coat Layer

Claims (6)

In a transparent laminated film having an index matching layer in which a high refractive index layer and a low refractive index layer are laminated in this order on one surface of a transparent substrate,
Arithmetic mean roughness (Ra) in a minute region of 1 μm square is less than 0.7 nm / μm □,
The reflectance of 220-280 nm light is 3.3-6.5%,
A transparent laminated film having a coefficient of variation of an average reflectance of light of 220 to 280 nm of 15% or less. On the surface opposite to the surface on which the index matching layer of the transparent substrate is laminated, a hard coat layer is further provided,
The transparent laminated film according to claim 1, wherein the haze is less than 0.5%. The transparent laminated film according to claim 1 or 2,
A transparent conductive film comprising: a transparent electrode layer laminated on the low refractive index layer of the transparent laminated film.   A touch panel comprising the transparent conductive film according to claim 3. A method for producing a transparent laminated film having an index matching layer in which a high refractive index layer and a low refractive index layer are laminated in this order on one surface of a transparent substrate,
The index matching layer is formed by coating a coating liquid containing high refractive index fine particles, an acrylic monomer, a leveling agent, a photopolymerization initiator, and a solvent on the one surface of the transparent substrate, and photocuring the coating film. Form the
The acrylic monomer has at least one of a urethane bond, a hydroxyl group, an aromatic ring, an amino group, a carboxyl group, and a phosphate ester,
The method for producing a transparent laminated film, wherein the leveling agent is an acrylic polymer having a repeating structure represented by the following general formula (1).

Here, R ¹ is either hydrogen or a methyl group, and R ² is a C 1-9 polyether or alkyl.   The method for producing a transparent laminated film according to claim 5, wherein the high refractive index fine particles are zirconia oxide fine particles.

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