WO2018181722A1 - Protective film for touch panel electrode and touch panel - Google Patents

Abstract

According to one embodiment of the present invention, a protective film for a touch panel electrode is obtained by curing a photosensitive resin composition containing: a binder polymer having a weight average molecular weight of 100000 or more; a photopolymerizable compound; and a photopolymerization initiator.

Description

Protective film for touch panel electrode and touch panel

The present invention relates to a protective film for a touch panel electrode and a touch panel.

Liquid crystal displays are used for large electronic devices such as personal computers and televisions, small electronic devices such as car navigation systems, mobile phones and electronic dictionaries, and display devices such as OA (Office Automation, Office Automation) and FA (Factory Automation, Factory Automation) devices. Elements and touch panels (touch sensors) are used.

Touch panels have already been put to practical use in various methods, but in recent years, the use of capacitive touch panels has progressed. In a projected capacitive touch panel, which is a kind of capacitive touch panel, generally, a plurality of X electrodes and a plurality of orthogonal to the X electrodes are used to express two-dimensional coordinates by the X axis and the Y axis. The Y electrode forms a two-layer structure. In recent years, the use of conductive meshes such as Ag nanowires and carbon nanotubes, Ag meshes, Cu meshes and the like has been studied as these electrodes, but ITO (Indium-Tin- Oxide) is still mainstream.

By the way, since the frame area of the touch panel is an area where the touch position cannot be detected, reducing the area of the frame area is an important factor for improving the product value. In the frame area, a metal wiring is required to transmit a touch position detection signal, and the metal wiring is generally formed of copper, silver, or the like.

However, in the touch panel as described above, corrosive components such as moisture and salt may enter the sensing region from the inside when the fingertip comes into contact. If a corrosive component enters the touch panel, the metal wiring corrodes, and there is a risk of an increase in electrical resistance between the electrode and the drive circuit, disconnection, or the like.

In order to prevent corrosion of metal wiring, a capacitive projection type touch panel in which an insulating layer is formed on metal is disclosed (for example, Patent Document 1). In this touch panel, a silicon dioxide layer is formed on a metal by a plasma chemical vapor deposition method (plasma CVD method) to prevent corrosion of the metal. As another method, there is known a method in which a photosensitive layer made of a photosensitive resin composition is provided on a predetermined substrate, and this photosensitive layer is exposed and developed (for example, Patent Document 2). In this method, a film-like resist film having a desired thickness is bonded onto a base material, and thereafter, exposure and development are performed to form a resist film at a necessary location.

JP 2011-28594 A International Publication No. 2013/084886

In recent years, there has been an increasing demand for thinner and lighter displays and touch panels. Accordingly, a flexible substrate is used as the substrate. Furthermore, with the widespread use of wearable devices, demands for flexibility (also referred to as “flexibility”) for touch panels, base materials and the like are increasing year by year from the viewpoints of device design and design.

In such a touch panel having flexibility, since the ITO electrode is fragile, there is a problem in that the resistance value of the touch panel electrode increases as the touch panel is bent. So far, from the viewpoint of preventing corrosion of metal wiring, application of a protective film (insulating layer or resist film) as described above has been studied, but the increase in the resistance value of the touch panel electrode accompanying bending of the touch panel is suppressed. There were no cases examined from the viewpoint.

This invention is made in view of such a situation, and it aims at providing the touchscreen provided with the protective film which can suppress the raise of the resistance value of the touchscreen electrode accompanying the bending of a touchscreen, and the said protective film.

As a result of intensive studies by the present inventors to solve the above problems, it has been found that an increase in the resistance value of the electrode when the touch panel is bent is suppressed by forming a predetermined cured film on the electrode, The present invention has been completed.

In one aspect, the present invention is a touch panel electrode protective film obtained by curing a photosensitive resin composition containing a binder polymer having a weight average molecular weight of 100,000 or more, a photopolymerizable compound, and a photopolymerization initiator. It is.

The present inventors consider the reason why this protective film can solve the above problems as follows. When a protective film is not formed on the touch panel electrode provided on the base material, when the touch panel is bent, the touch panel electrode cannot follow the base material due to generation of cracks, and is peeled off from the adherend. As a result, poor connection between the touch panel electrodes occurs, and the resistance value increases. In contrast, when a predetermined protective film is formed on the touch panel electrode, when the touch panel is bent, the protective film presses the touch panel electrode even if the touch panel electrode becomes unable to follow the base material due to the occurrence of cracks. Connection failure between the electrodes is less likely to occur. Therefore, it is considered that an increase in the resistance value of the touch panel can be suppressed by forming a protective film on the touch panel electrode.

The protective film is preferably provided in the bent region of the touch panel.

The minimum value of the light transmittance at 400 to 700 nm of the protective film is preferably 90% or more.

The thickness of the protective film is preferably 50 μm or less.

In another aspect, the present invention is a touch panel including a base material, an electrode provided on the base material, and the protective film provided on the electrode.

According to the present invention, it is possible to provide a protective film that can suppress an increase in the resistance value of the touch panel electrode accompanying bending of the touch panel, and a touch panel including the protective film.

1A and 1B are schematic cross-sectional views showing one embodiment of a photosensitive element, respectively. FIG. 2A is a schematic top view illustrating an aspect of a capacitive touch panel. FIG. 2B is a partial cross-sectional view taken along the line II of C portion shown in FIG. FIG. 3A is a perspective view showing an example of a flexible touch panel. FIG. 3B is a cross-sectional view taken along the line II-II shown in FIG. 4A and 4B are perspective views showing another example of a touch panel having flexibility.

Hereinafter, embodiments of the present invention will be described in detail with appropriate reference to the drawings.

In this specification, the touch panel electrode is provided not only in an electrode provided in a sensing area (also referred to as “touch screen area”) of the touch panel but also in a frame area that is an area other than the sensing area (touch screen area). Also includes metal wiring. The electrode provided with the protective film may be either one of the electrode provided in the sensing region and the metal wiring provided in the frame region, or both.

In this specification, “(meth) acrylic acid” means “acrylic acid” or “methacrylic acid”. “(Meth) acrylate” means “acrylate” or “methacrylate”.

In this specification, “A or B” means that it is at least one of A and B, that is, it may be both A and B. Unless otherwise specified, the materials, components, and the like exemplified in this specification may be used alone or in combination of two or more.

In this specification, the term “process” includes not only an independent process but also a process that can be clearly distinguished from other processes if the intended action of the process is achieved. . In the present specification, numerical values indicated by using “to” include numerical values described before and after “to” as the minimum value and the maximum value, respectively.

In the present specification, the content of each component in the composition is the total amount of the plurality of substances present in the composition unless there is a specific notice when there are a plurality of substances corresponding to each component in the composition. means.

<Photosensitive resin composition>
The photosensitive resin composition includes a binder polymer (also referred to as “(A) component”), a photopolymerizable compound (also referred to as “(B) component”), and a photopolymerization initiator (also referred to as “(C) component”). ) And.

(Binder polymer)
Examples of the component (A) include a binder polymer having a carboxyl group from the viewpoint of enabling patterning by alkali development. The binder polymer having a carboxyl group is, for example, a copolymer having a polymerizable monomer having a carboxyl group and another polymerizable monomer as a constituent unit, preferably (a) (meth) acrylic acid, And (b) a copolymer having a structural unit derived from an alkyl (meth) acrylate.

Examples of the (meth) acrylic acid alkyl ester include (meth) acrylic acid methyl ester, (meth) acrylic acid ethyl ester, (meth) acrylic acid butyl ester, (meth) acrylic acid 2-ethylhexyl ester, (meth) acrylic And acid hydroxyl ethyl ester.

The copolymer may further have another monomer as a constituent unit that can be copolymerized with at least one of the components (a) and (b). Other monomers that can be copolymerized with at least one of the components (a) and (b) include, for example, (meth) acrylic acid glycidyl ester, (meth) acrylic acid benzyl ester, styrene, dicyclopentanyl ( And (meth) acrylate and dicyclopentenyloxyethyl (meth) acrylate.

Among these, (meth) acrylic acid, (meth) acrylic acid glycidyl ester, (meth) acrylic acid benzyl ester, styrene from the viewpoints of alkali developability, especially alkali developability for inorganic alkaline aqueous solution, patterning property, and transparency. A structure derived from at least one compound selected from the group consisting of: (meth) acrylic acid methyl ester, (meth) acrylic acid ethyl ester, (meth) acrylic acid butyl ester, and (meth) acrylic acid-2-ethylhexyl ester Binder polymers having units are preferred.

The weight average molecular weight of the binder polymer as component (A) is 100,000 or more, and preferably 120,000 or more, more preferably 140000 or more, and further preferably 160000 or more from the viewpoint of further excellent film formability and flexibility. . From the viewpoint of resolution, the weight average molecular weight of the binder polymer is preferably 300000 or less, more preferably 250,000 or less, and even more preferably 200000 or less. In the present specification, the weight average molecular weight means a value obtained under the same measurement conditions as in Examples.

The acid value of the binder polymer as component (A) may be 75 mgKOH / g or more from the viewpoint of easily forming a protective film having a desired shape, and the ease and protection of controlling the shape of the protective film From the viewpoint of achieving compatibility with the rust prevention property of the film, it is preferably 75 to 200 mgKOH / g, more preferably 75 to 150 mgKOH / g, and still more preferably 75 to 120 mgKOH / g. The acid value of the binder polymer as the component (A) means a value obtained under the same measurement conditions as in the examples of the present specification.

The hydroxyl value of the binder polymer as component (A) is preferably 50 mgKOH / g or less, more preferably 45 mgKOH / g or less, from the viewpoint of further improving the rust prevention property. The hydroxyl value of (A) component means the value obtained on the same measurement conditions as the Example of this specification.

The content of the component (A) is preferably 35 parts by mass or more with respect to 100 parts by mass of the total amount of the component (A) and the component (B) from the viewpoint of maintaining transparency and suitably forming a desired pattern. More preferably, it is 40 parts by mass or more, more preferably 50 parts by mass or more, and particularly preferably 55 parts by mass or more.

(Photopolymerizable compound)
(B) As a photopolymerizable compound which is a component, the photopolymerizable compound which has an ethylenically unsaturated group is mentioned.

Examples of the photopolymerizable compound having an ethylenically unsaturated group include a monofunctional vinyl monomer having one polymerizable ethylenically unsaturated group in the molecule and two polymerizable ethylenically unsaturated groups in the molecule. Examples thereof include a bifunctional vinyl monomer and a polyfunctional vinyl monomer having at least three polymerizable ethylenically unsaturated groups in the molecule.

As a monofunctional vinyl monomer having one polymerizable ethylenically unsaturated group in the molecule, for example, (meth) acrylic acid exemplified as a monomer suitable for the component (A) to have as a structural unit , (Meth) acrylic acid alkyl esters and monomers copolymerizable therewith.

Examples of the bifunctional vinyl monomer having two polymerizable ethylenically unsaturated groups in the molecule include polyethylene glycol di (meth) acrylate (having 2 to 14 ethoxy groups), trimethylolpropane di (meta). ) Acrylate, polypropylene glycol di (meth) acrylate (having 2 to 14 propylene groups); bisphenol A polyoxyethylene diacrylate (ie 2,2-bis (4-acryloxypolyethoxyphenyl) propane), Bisphenol A polyoxyethylene dimethacrylate (ie 2,2-bis (4-methacryloxypolyethoxyphenyl) propane), bisphenol A diglycidyl ether diacrylate, bisphenol A diglycidyl ether dimethacrylate, etc .; polyvalent carboxylic acid ( Water phthalic acid, etc.) and material having a hydroxyl group and ethylenically unsaturated group (beta-hydroxyethyl acrylate, esterified products of beta-hydroxyethyl methacrylate, and the like).

The polyfunctional vinyl monomer having at least three polymerizable ethylenically unsaturated groups in the molecule can be obtained, for example, by reacting a polyhydric alcohol having at least three hydroxyl groups with an α, β-unsaturated carboxylic acid. Compound, compound obtained by addition reaction of compound having at least three glycidyl groups and α, β-unsaturated carboxylic acid, (meth) acrylate compound having urethane bond and at least three (meth) acryloyl groups in the molecule And the like, and the like.

Examples of compounds obtained by reacting a polyhydric alcohol with an α, β-unsaturated carboxylic acid include trimethylolpropane tri (meth) acrylate, tetramethylolmethanetri (meth) acrylate, and tetramethylolmethanetetra (meth). Examples include acrylate, dipentaerythritol penta (meth) acrylate, and dipentaerythritol hexa (meth) acrylate.

Examples of the compound obtained by addition reaction of a compound having a glycidyl group and an α, β-unsaturated carboxylic acid include trimethylolpropane triglycidyl ether triacrylate.

Examples of urethane monomers include tris ((meth) acryloxytetraethylene glycol isocyanate) hexamethylene isocyanurate.

The component (B) preferably contains a polyfunctional vinyl monomer having at least three polymerizable ethylenically unsaturated groups. The component (B) is preferably a (meth) acrylate compound having a skeleton derived from pentaerythritol, or a (meth) acrylate compound having a skeleton derived from dipentaerythritol, from the viewpoint of electrode corrosion inhibition and ease of development. And a (meth) acrylate compound having a skeleton derived from trimethylolpropane, more preferably a (meth) acrylate compound having a skeleton derived from dipentaerythritol and a skeleton derived from trimethylolpropane (meta ) At least one selected from acrylate compounds.

Here, (meth) acrylate having a skeleton derived from dipentaerythritol means an esterified product of dipentaerythritol and (meth) acrylic acid. The esterified product also includes a compound modified with an alkyleneoxy group. The number of ester bonds in one molecule of the esterified product is preferably 6. The esterified product may contain a compound having 1 to 5 ester bonds in one molecule.

The (meth) acrylate compound having a skeleton derived from trimethylolpropane means an esterified product of trimethylolpropane and (meth) acrylic acid. The esterified product also includes a compound modified with an alkyleneoxy group. The number of ester bonds in one molecule of the esterified product is preferably 3. The esterified product may include an esterified product having 1 to 2 ester bonds in one molecule.

The ratio of the polyfunctional vinyl monomer having at least three polymerizable ethylenically unsaturated groups in the molecule is the photopolymerizability contained in the photosensitive resin composition from the viewpoint of obtaining photocurability and electrode corrosion inhibition. Preferably it is 30 mass parts or more with respect to 100 mass parts of total amounts of a compound ((B) component), More preferably, it is 50 mass parts or more, More preferably, it is 75 mass parts or more.

About content of (A) component and (B) component in the photosensitive resin composition, (A) component is 35-85 mass parts with respect to 100 mass parts of total amounts of (A) component and (B) component, and ( The component (B) is preferably 15 to 65 parts by mass, the component (A) is preferably 40 to 80 parts by mass, the component (B) is more preferably 20 to 60 parts by mass, and the component (A) is 50 to 50 parts by mass. It is more preferable that 70 parts by mass and the component (B) are 30 to 50 parts by mass, and it is particularly preferable that the component (A) is 55 to 65 parts by mass and the component (B) is 35 to 45 parts by mass.

The photosensitive resin composition has sufficient coating properties and film properties when a photosensitive element to be described later is formed by making the content of the component (A) and the component (B) within the above range, Sensitivity, photocurability, developability, and electrode corrosion inhibition can be sufficiently secured. In particular, from the viewpoint of maintaining transparency and forming a favorable pattern, the content of the component (A) is preferably 35 parts by mass with respect to 100 parts by mass of the total amount of the components (A) and (B). As mentioned above, More preferably, it is 40 mass parts or more, More preferably, it is 50 mass parts or more, Most preferably, it is 55 mass parts or more.

Examples of the photopolymerization initiator (C) include oxime ester compounds and alkylphenone compounds. The component (C) can form a pattern with sufficient resolution even when the protective film is highly transparent and the protective film is a thin film (for example, a film having a thickness of 10 μm or less). Therefore, it preferably contains at least one selected from the group consisting of oxime ester compounds and alkylphenone compounds.

Examples of the oxime ester compound include compounds represented by the following general formula (C-1).

In formula (C-1), R ¹ represents an alkyl group having 1 to 12 carbon atoms or a cycloalkyl group having 3 to 20 carbon atoms. As long as the effects of the present invention are not impaired, the compound represented by the formula (C-1) may have a substituent on the aromatic ring. R ¹ is preferably an alkyl group having 3 to 10 carbon atoms or a cycloalkyl group having 4 to 15 carbon atoms, more preferably an alkyl group having 4 to 8 carbon atoms or a cycloalkyl group having 4 to 10 carbon atoms.

Examples of the compound represented by the formula (C-1) include (1,2-octanedione, 1- [4- (phenylthio) phenyl-, 2- (O-benzoyloxime)] and the like. -Octanedione, 1- [4- (phenylthio) phenyl-, 2- (O-benzoyloxime)] is available as IRGACURE OXE 01 (trade name, manufactured by BASF Japan Ltd.).

２，２－ジメトキシ－１，２－ジフェニルエタン－１－オンは、ＩＲＧＡＣＵＲＥ　６５１（ＢＡＳＦジャパン（株）製、商品名）として入手可能である。 Examples of the alkylphenone compound include a compound represented by the following general formula (C-2) (2,2-dimethoxy-1,2-diphenylethane-1-one).

2,2-dimethoxy-1,2-diphenylethane-1-one is available as IRGACURE 651 (trade name, manufactured by BASF Japan Ltd.).

As the alkylphenone compound, in addition to the compound represented by the above formula (C-2), for example, 1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1- {4- [4- (2-hydroxy-2- Methyl-propionyl) -benzyl] phenyl} -2-methyl-propan-1-one, 1.3α-aminoalkylphenone, 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1,2- (dimethylamino) -2-[(4-methylphenyl Yl) methyl] -1- [4- (4-morpholinyl) phenyl] -1-butanone, and the like. 1-hydroxy-cyclohexyl-phenyl-ketone is IRGACURE 184 (trade name, manufactured by BASF Japan), and 2-hydroxy-2-methyl-1-phenyl-propan-1-one is IRGACURE 1173 (BASF Japan) Product name, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one is IRGACURE 2959 (trade name, manufactured by BASF Japan Ltd.) 2-Hydroxy-1- {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] phenyl} -2-methyl-propan-1-one is IRGACURE 127 (BASF Japan Ltd., (Product name) can be obtained respectively.

(C) Component may be other photopolymerization initiators other than the oxime ester compound and the alkylphenone compound. Examples of other photopolymerization initiators include aromatic ketones such as benzophenone and 4-methoxy-4′-dimethylaminobenzophenone; benzoin ether compounds such as benzoin methyl ether, benzoin ethyl ether and benzoin phenyl ether; benzoin and methyl benzoin Benzoin compounds such as ethyl benzoin; benzyl derivatives such as benzyl dimethyl ketal; acridine derivatives such as 9-phenylacridine and 1,7-bis (9,9′-acridinyl) heptane; N-phenylglycine and N-phenylglycine derivatives A coumarin compound; an oxazole compound and the like. As the component (C), a combination of a thioxanthone compound and a tertiary amine compound, such as a combination of diethylthioxanthone and dimethylaminobenzoic acid, may be used.

The content of the component (C) is preferably 0.1 parts by mass or more from the viewpoint of excellent sensitivity to light and resolution with respect to 100 parts by mass of the total amount of the components (A) and (B). From the viewpoint of excellent light transmittance at 400 to 700 nm, it is preferably 20 parts by mass or less. The content of the component (C) is preferably 0.1 to 20 parts by weight, more preferably 1 to 10 parts by weight, and still more preferably 2 parts per 100 parts by weight of the total amount of the components (A) and (B). Is 5 parts by mass.

By the way, when providing a protective film on a part of the ITO electrode of the touch panel, for example, a part where a protective layer is not formed in the sensing area, and a metal layer such as copper is formed on the ITO electrode in the frame area and the ITO electrode. In the case where a protective film is provided, unnecessary portions can be removed by performing exposure and development after providing a photosensitive layer on the entire surface (the entire surface of the touch panel). In this case, the photosensitive layer is required to have good developability so as to have sufficient adhesion to the electrode to be protected and no development residue occurs in unnecessary portions. From the viewpoint of achieving both adhesion and developability in such a case, the photosensitive resin composition of the present embodiment is preferably a phosphoric ester having an ethylenically unsaturated group (hereinafter also referred to as component (D)). Containing. In this specification, although the phosphate ester containing an ethylenically unsaturated group may overlap with the said (B) component, it shall not be contained in (B) component.

The phosphoric acid ester having an ethylenically unsaturated group as component (D) is preferably from the viewpoint of achieving both high adhesion and developability to the ITO electrode while ensuring sufficient protection against rust of the protective film. These are compounds represented by the following general formula (D-1). The compound represented by the formula (D-1) is available as a commercial product such as PM-21 (manufactured by Nippon Kayaku Co., Ltd.).

(Other additives)
The photosensitive resin composition according to the present embodiment is optionally provided with an adhesion imparting agent such as a silane coupling agent, a leveling agent, a plasticizer, a filler, an antifoaming agent, a flame retardant, a stabilizer, and an oxidation agent. An inhibitor, a fragrance, a thermal crosslinking agent, a polymerization inhibitor and the like may be contained in an amount of 0.01 to 20 parts by mass with respect to 100 parts by mass of the total amount of component (A) and component (B). Moreover, the photosensitive resin composition may further contain a water-soluble compound to the extent that it does not significantly impair the function of the protective film.

The photosensitive resin composition according to this embodiment can be used for forming a photosensitive layer. For example, a coating solution is prepared by uniformly dissolving or dispersing the photosensitive resin composition in a solvent, and a coating film is formed by coating the coating solution on, for example, a support substrate, and the solvent is removed by drying. Thus, a photosensitive layer can be formed.

Examples of the solvent include ketones, aromatic hydrocarbons, alcohols, ethers, esters, alkyl halides and the like from the viewpoints of solubility of each component, ease of film formation, and the like. Examples of the ketone include acetone, methyl ethyl ketone, and methyl isobutyl ketone. Examples of the aromatic hydrocarbon include toluene. Examples of the alcohol include monohydric alcohols and dihydric alcohols (glycols). Examples of the monohydric alcohol include methanol, ethanol, propanol, butanol and the like. Examples of the glycol include methylene glycol, ethylene glycol, propylene glycol and the like. Examples of the ether include alkylene glycol alkyl ether and alkylene glycol alkyl ether acetate. Examples of the alkylene glycol alkyl ether include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol dimethyl ether, diethylene glycol ethyl methyl ether, diethylene glycol diethyl ether, and propylene glycol monomethyl ether. Examples of the alkylene glycol alkyl ether acetate include ethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, and the like. Examples of the halogenated ester include chloroform and methylene chloride.

Application methods include known methods such as micro gravure coating, spin coating, dip coating, curtain flow coating, roll coating, spray coating, and slit coating.

The photosensitive resin composition according to the present embodiment is used for forming a protective film for a touch panel electrode, and is excellent in adhesion to the base material of the touch panel. When the touch panel has flexibility, the photosensitive resin composition is suitable for forming a protective film provided in a bent region of the touch panel. According to this photosensitive resin composition, generation | occurrence | production of the crack in an electrode and a protective film at the time of bending a touch panel can be suppressed.

The photosensitive resin composition of the present embodiment is suitably used regardless of the type of device on which the touch sensor is mounted as long as it is intended to protect the electrodes of the touch sensor. Examples of the device include a liquid crystal display device, an organic electroluminescence display device, a smartphone, and a tablet PC.

<Photosensitive element>
The photosensitive resin composition according to the present embodiment is preferably used after being formed into a film shape like a photosensitive element described later. By laminating a photosensitive film on a substrate having a touch panel electrode, a roll-to-roll process can be easily realized, a solvent drying process can be shortened, and the production process can be greatly shortened and cost can be greatly reduced. .

FIG. 1A is a schematic cross-sectional view showing an embodiment of a photosensitive element. As shown in FIG. 1A, the photosensitive element 1 </ b> A includes a support film 2 and a photosensitive layer 3 made of the photosensitive resin composition provided on the support film 2.

1 A of photosensitive elements prepare the coating liquid containing the photosensitive resin composition which concerns on this embodiment, for example, apply | coat the said coating liquid on the support film 2, and form the coating film further, It is obtained by forming the photosensitive layer 3 by drying (volatilizing the solvent). The coating liquid can be obtained by uniformly dissolving or dispersing each component constituting the photosensitive resin composition according to the present embodiment described above in a solvent.

The solvent is not particularly limited, and a known solvent can be used. As the solvent, those exemplified as the solvent for the photosensitive resin composition can be similarly used.

Application methods include, for example, doctor blade coating method, Meyer bar coating method, roll coating method, screen coating method, spinner coating method, inkjet coating method, spray coating method, dip coating method, gravure coating method, curtain coating method, die coating Examples thereof include a coating method.

The drying conditions are not particularly limited, but the drying temperature is preferably 60 to 130 ° C., and the drying time is preferably 0.5 to 30 minutes.

(Support film)
As the support film 2, a polymer film can be used. Examples of the polymer film include films made of polyethylene terephthalate, polycarbonate, polyethylene, polypropylene, cycloolefin polymer, polyethersulfone, and the like.

The thickness of the support film 2 is preferably 5 to 100 μm, more preferably 10 to 70 μm, and still more preferably, from the viewpoints of ensuring coverage and suppressing a reduction in resolution when irradiated with actinic rays through the support film 2. Is from 15 to 40 μm, particularly preferably from 20 to 35 μm.

(Photosensitive layer)
The thickness of the photosensitive layer 3 is sufficient to protect the electrode, and is dried (after the solvent is volatilized) so that the level difference on the surface of the touch sensor caused by the partial electrode protective film formation is minimized. The thickness is preferably 20 μm or less, more preferably 1 μm to 9 μm, still more preferably 1 μm to 8 μm, particularly preferably 2 μm to 8 μm, and most preferably 3 μm to 8 μm.

The minimum value of the light transmittance at 400 to 700 nm of the photosensitive layer 3 is preferably 90% or more, more preferably 92% or more, and further preferably 95% or more. If the minimum value of light transmittance in the wavelength range of 400 to 700 nm, which is a general visible light wavelength range, is 90% or more, the transparent electrode in the sensing area of the touch sensor is protected, and the frame of the touch sensor When the protective layer is visible from the edge of the sensing area when protecting the metal layer in the area (for example, a layer in which a copper layer is formed on the ITO electrode), the image display quality, color, brightness, etc. in the sensing area are reduced. Can be sufficiently suppressed.

In this specification, the minimum value of the light transmittance at 400 to 700 nm of the photosensitive layer is obtained by measuring the light transmittance at a measurement wavelength region of 400 to 700 nm using an ultraviolet-visible spectrophotometer. It means the minimum value of light transmittance in the region. The light transmittance is measured on the cured photosensitive layer formed by irradiating the photosensitive layer having a thickness of 10 μm or less formed on the support film with ultraviolet rays, followed by photocuring and then removing the support film.

From the viewpoint of further improving the visibility of the touch panel, b ^* in the CIELAB color system of the photosensitive layer 3 is preferably −0.2 to 1.0, more preferably 0.0 to 0.7, and still more preferably. 0.1 to 0.5. Similarly to the case where the minimum value of the light transmittance at 400 to 700 nm is 90% or more, from the viewpoint of preventing the image display quality in the sensing area and the deterioration of the hue, b ^* in the CIELAB color system is Preferably, it is -0.2 to 1.0.

In the present specification, b ^* in the CIELAB color system refers to, for example, Konica Minolta for a cured photosensitive layer that is photocured by irradiating a photosensitive layer having a thickness of 10 μm or less formed on a support film with ultraviolet rays. It means a value obtained by measurement using a spectrocolorimeter “CM-5” manufactured by Co., Ltd. under the conditions of a D65 light source and a viewing angle of 2 °.

The photosensitive element of the present embodiment may include other appropriately selected layers in addition to the photosensitive layer as long as a desired effect is obtained. There is no restriction | limiting in particular as another layer, According to the objective, it can select suitably, For example, an optical adjustment layer, a cushion layer, an oxygen shielding layer, a peeling layer, an adhesive layer etc. are mentioned. The photosensitive element may be provided with one of these layers alone, or may be provided with two or more. The photosensitive element may include two or more layers of the same kind.

(Protective film)
In another embodiment, as shown in FIG. 1B, the photosensitive element 1B is provided on the surface of the photosensitive layer 3 opposite to the support film 2 in addition to the support film 2 and the photosensitive layer 3. A protective film (cover film) 4 may be further provided. That is, the photosensitive element 1 </ b> B according to the embodiment includes the support film 2, the photosensitive layer 3, and the protective film 4 in this order.

Examples of the protective film 4 include polyethylene, polypropylene, polyethylene terephthalate, polycarbonate, polyethylene-vinyl acetate copolymer, and a film made of a laminated film of polyethylene-vinyl acetate copolymer and polyethylene.

The thickness of the protective film 4 is preferably 5 to 100 μm. The thickness of the protective film 4 is preferably 70 μm or less, more preferably 60 μm or less, still more preferably 50 μm or less, and particularly preferably 40 μm or less from the viewpoint of storing the photosensitive element 1B in a roll shape.

Photosensitive elements 1A and 1B can be stored in roll form or used.

The photosensitive elements 1 </ b> A and 1 </ b> B are suitable for forming a protective film for a touch panel electrode by including the photosensitive layer 3 formed of the photosensitive resin composition, and are excellent in adhesion with the base material of the touch panel. Can be formed.

<Touch panel>
FIG. 2 is a schematic diagram illustrating an example of a capacitive touch panel. FIG. 2A is a schematic top view of the touch panel, and FIG. 2B is a partial cross-sectional view taken along line II of C portion shown in FIG.

2 (a) and 2 (b), the touch panel 5 includes a base material (transparent base material) 6 and a touch panel electrode provided on the base material 6. A touch screen area 7 for detecting touch position coordinates is formed on one side of the touch panel 5. As the touch panel electrode, a first transparent electrode 8, a second transparent electrode 9, a metal wiring (lead wiring) 10, a connection electrode 11, and a connection terminal 12 are provided.

The base material 6 provided with the touch panel electrode shown by FIG. 2 (a), (b) is obtained by the following procedures, for example. After forming a metal film by sputtering in the order of ITO and Cu on a substrate 6 such as a PET film, an etching photosensitive film is pasted on the metal film to form a desired resist pattern, and unnecessary Cu is chlorinated. After removing with an etching solution such as an iron aqueous solution, the resist pattern is peeled off.

Examples of the substrate 6 include substrates such as glass plates, plastic plates, and ceramic plates that are generally used for touch sensors. Examples of the touch panel electrode include electrodes formed of ITO, Cu, Al, Mo, or the like.

The first transparent electrode 8 and the second transparent electrode 9 are provided in the touch screen area 7 in order to detect a capacitance change. The first transparent electrode 8 and the second transparent electrode 9 detect the X coordinate and the Y coordinate of the touch position, respectively.

The metal wiring 10 transmits a detection signal of the touch position by the first transparent electrode 8 and the second transparent electrode 9 to an external circuit. The metal wiring 10 and the first transparent electrode 8 and the second transparent electrode 9 are connected to each other by a connection electrode 11 provided on the first transparent electrode 8 and the second transparent electrode 9. One end of the metal wiring 10 is connected to the first transparent electrode 8 and the second transparent electrode 9. The other end of the metal wiring 10 is provided with a connection terminal 12 for connection to an external circuit.

As shown in FIG. 2A, the first transparent electrode 8, the second transparent electrode 9, the metal wiring 10, the connection electrode 11, and a part of the connection terminal 12 are protected so as to cover them. A membrane 13 is arranged. The protective film 13 may be in direct contact with the touch panel electrode such as the metal wiring 10 and the base material 6 or may be provided on the touch panel electrode such as the metal wiring 10 and the base material 6 through another layer. . The protective film 13 is suitably formed using the photosensitive resin composition or photosensitive element of this embodiment.

<Method for forming protective film>
[Layer formation process]
The protective film 13 is formed as follows, for example. First, the photosensitive layer which consists of the said photosensitive resin composition is provided on the base material 6 with which electrodes (touch panel electrode), such as the metal wiring 10, were provided (layer formation process). When a photosensitive element is used in the layer forming step, the photosensitive layer is transferred, for example, by pressing the photosensitive layer on the surface of the substrate 6 on which the metal wiring 10 or the like is provided while heating the photosensitive element. , Provided by stacking. In addition, when using the photosensitive element 1B provided with the protective film 4 as a photosensitive element, the protective film 4 is removed before pressure bonding. The photosensitive element may be transferred to the substrate after only the connecting portion with the other substrate is removed in a rectangular shape.

Crimping means includes a crimping roll. The pressure roll may be provided with a heating means so that it can be heat-pressure bonded.

The heating temperature for thermocompression bonding is such that the components of the photosensitive layer are not easily cured or thermally decomposed while ensuring sufficient adhesion between the photosensitive layer and the substrate 6 and adhesion between the photosensitive layer and the touch panel electrode. The temperature is preferably 10 to 160 ° C, more preferably 20 to 150 ° C, still more preferably 23 to 150 ° C.

The pressure during thermocompression bonding is a linear pressure from the viewpoint of suppressing deformation of the substrate 6 while ensuring sufficient adhesion between the photosensitive layer and the substrate 6, preferably 50 to 1 × 10 ⁵ N / m. More preferably, it is 2.5 × 10 ² to 5 × 10 ⁴ N / m, and further preferably 5 × 10 ² to 4 × 10 ⁴ N / m.

If the photosensitive element is heated as described above, it is not necessary to pre-heat the substrate 6, but preferably the substrate 6 is preliminarily from the viewpoint of further improving the adhesion between the photosensitive layer and the substrate 6. Heat treatment. The preheating temperature at this time is preferably 30 to 150 ° C.

If necessary, by applying an equal pressure with compressed air while being heated by an autoclave during or after thermocompression bonding, air bubbles in the photosensitive element can be removed and at the same time the crimping strength can be increased.

In another embodiment, instead of using the photosensitive element, a coating liquid containing the photosensitive resin composition and the solvent according to the present embodiment is prepared and applied to the surface of the substrate 6 on which the touch panel electrode is provided. And dried to form a photosensitive layer.

[Exposure process]
Following the layer formation step, the entire surface of the photosensitive layer is irradiated with actinic rays to form a protective film made of a cured product of the photosensitive layer (exposure step).

When actinic light is irradiated, if the support film on the photosensitive layer is transparent, it can be irradiated as it is, and if it is opaque, it is removed and then irradiated with actinic light. From the viewpoint of protecting the photosensitive layer, a transparent polymer film is preferably used as the support film, and actinic rays are irradiated through the polymer film while it remains. In this case, the support film is removed after irradiation with actinic rays.

As a light source of actinic light used for irradiation of actinic light, a known actinic light source can be used and is not particularly limited as long as it emits ultraviolet rays effectively. Examples of the light source include a metal halide lamp, a carbon arc lamp, an ultrahigh pressure mercury lamp, a high pressure mercury lamp, and a xenon lamp.

The irradiation amount of actinic rays at this time is usually 1 × 10 ² to 1 × 10 ⁴ J / m ² , and heating can be accompanied at the time of irradiation. When the irradiation amount of this actinic ray is 1 × 10 ² J / m ² or more, the photocuring effect tends to be sufficient, and when it is 1 × 10 ⁴ J / m ² or less, the photosensitive layer is discolored. It tends to be possible to suppress this.

The thickness of the protective film 13 is preferably 50 μm or less or 20 μm or less so that the step on the surface of the touch sensor that exhibits a sufficient effect for protecting the electrode and that is caused by partial formation of the protective film of the electrode is minimized. More preferably, they are 1 micrometer or more and 9 micrometers or less, More preferably, they are 1 micrometer or more and 8 micrometers or less, Especially preferably, they are 2 micrometers or more and 8 micrometers or less, Most preferably, they are 3 micrometers or more and 8 micrometers or less. Even if this protective film 13 is a thin film as described above, an increase in the resistance value of the touch panel electrode accompanying bending of the touch panel can be suppressed.

The minimum value of the light transmittance at 400 to 700 nm of the protective film 13 is preferably 90% or more, more preferably 92% or more, and still more preferably 95% or more from the viewpoint of excellent visibility. If the light transmittance of the protective film is 90% or more in the wavelength range of 400 to 700 nm, which is a general visible light wavelength range, the transparent electrode in the sensing area of the touch sensor is protected, and the touch sensor When the metal film in the frame area (for example, the copper layer formed on the ITO electrode) is protected and the protective film is visible from the edge of the sensing area, the image display quality, color, and brightness in the sensing area are reduced. Can be sufficiently suppressed.

From the viewpoint of excellent visibility, b ^* in the CIELAB color system of the protective film 13 is preferably −0.2 to 1.0, more preferably 0.0 to 0.7, and still more preferably 0.1 to 0.5.

In other embodiments, the substrate 6 may further include an optical adjustment layer (also referred to as “index matching layer”), an insulating layer, and the like.

In the touch panel described above, the metal wiring 10 and the first transparent electrode 8 and the second transparent electrode 9 are connected to each other by the connection electrode 11, but in another aspect, the metal wiring and the first transparent electrode 8 The transparent electrode and the second transparent electrode may be directly connected to each other.

In other embodiments, the place where the protective film 13 is provided may be changed as appropriate. In the above touch panel, the protective film 13 is provided so as to cover all of the first transparent electrode 8, the second transparent electrode 9, the metal wiring 10, the connection electrode 11, and a part of the connection terminal 12. A part of each of the first transparent electrode, the second transparent electrode, and the connection terminal, and the metal wiring and the connection electrode may be provided. In this case, the protective film 13 is provided as follows, for example. First, in the exposure step, the photosensitive layer is cured by irradiating a predetermined portion of the photosensitive layer with actinic rays through a photomask. The photosensitive layer that has been irradiated with actinic rays is developed with a developing solution, and a portion that is not irradiated with actinic rays (that is, other than a predetermined portion of the photosensitive layer) is removed, whereby a protective film 13 that covers a portion of the electrode. Is formed (development process). The protective film 13 is made of a cured product of the photosensitive resin composition according to the present embodiment and has a predetermined pattern. In addition, the pattern in this specification includes not only the shape of the fine wiring that forms the circuit, but also a shape in which only the connection portion with the other substrate is removed in a rectangle, a shape in which only the sensing region of the substrate is removed, and the like. It is.

[Development process]
After irradiation with actinic rays, if a support film is laminated on the photosensitive layer, it may be removed, and if necessary, a portion not irradiated with actinic rays may be removed with a developer (developing step). ).

The developing step can be performed by a known method such as spraying, showering, rocking dipping, brushing, scrubbing, or the like, using a known developer such as an alkaline aqueous solution, an aqueous developer, or an organic solvent. In particular, the development step is preferably performed by spray development using an alkaline aqueous solution from the viewpoint of environment and safety.

The development temperature and time may be adjusted according to the developability of the photosensitive resin composition according to the present embodiment.

Further, the base of the alkaline aqueous solution remaining in the photosensitive layer after development and photocuring is subjected to an acid treatment by a known method such as spraying, rocking immersion, brushing or scrubbing using an organic acid, an inorganic acid or an aqueous acid solution thereof. (Neutralization treatment). Furthermore, the water washing process can also be performed after an acid treatment (neutralization treatment).

[Post-process]
The cured product of the photosensitive layer may be further cured after curing by irradiation with actinic light, after development, and if necessary, by irradiation with actinic light (for example, 5 × 10 ³ to 2 × 10 ⁴ J / m ² ). Good (post process). The photosensitive resin composition according to the present embodiment exhibits excellent adhesion to a metal even without a heating step after development, but if necessary, instead of irradiation with actinic rays after development, or A heat treatment (80 to 160 ° C.) may be applied in combination with the irradiation with actinic rays.

The touch panel 5 may have flexibility. FIG. 3A is a perspective view showing an example of a flexible touch panel. FIG. 3B is a cross-sectional view taken along the line II-II shown in FIG. As illustrated in FIGS. 3A and 3B, the touch panel 5 </ b> A includes a touch panel substrate 14 and a protective film 13 provided on the touch panel substrate 14. In FIG. 3 and subsequent figures, the base material 6 and the touch panel electrode in FIG. 2 are collectively referred to as a touch panel substrate 14 for simplification. That is, the touch panel 5A includes a base material 6, a touch panel electrode provided on the base material 6, and a protective film 13 provided so as to cover at least a part of the touch panel electrode.

The touch panel 5A having flexibility is bent in a direction perpendicular to the XY plane (−Z direction, opposite to the protective film 13 of the touch panel substrate 14) near both ends in the X direction, and extends in the Y direction. It has a bending region R1. The protective film 13 is provided on at least a part of the bent region R1.

In this specification, the bent region means a region folded with a predetermined curvature radius or a region that can be folded with a predetermined curvature radius. The predetermined radius of curvature is, for example, 40 mm or less, 10 mm or less, or 5 mm or less.

In another embodiment, the touch panel may be folded in the folding region. In other embodiments, the touch panel may have a bent region near the center.

4 (a) and 4 (b) are perspective views showing another example of a flexible touch panel. As shown in FIG. 4A, in one embodiment, the touch panel 5B has an XY plane direction (−Y direction, the main surface of the touch panel 5B) so that the protective film 13 is inside near the center in the Y direction. (Horizontal direction) is folded 180 degrees (also referred to as inward bending) and has a bent region R2 extending in the X direction. The protective film 13 is provided on at least a part of the bending region R2.

As shown in FIG. 4B, in one embodiment, the touch panel 5C has an XY plane direction (−Y direction, touch panel 5B) so that the protective film 13 is outside near the center in the Y direction. It is folded 180 ° (horizontal direction with respect to the main surface) (also referred to as outer bending) and has a bent region R3 extending in the X direction. The protective film 13 is provided in at least a part of the bending region R3.

Since the protective film 13 is formed of the photosensitive resin composition and has excellent adhesion to the touch panel substrate 14 (base material 6), the touch panel 5A, 5B, 5C having flexibility as described above is used. Preferably used. Moreover, the protective film 13 can suppress generation | occurrence | production of the crack in the touch-panel electrode of the folded touch panels 5A, 5B, and 5C, and the protective film 13. FIG. In addition, by using the protective film 13, it is possible to suppress an increase in resistance value in the touch panel electrode.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

[Preparation of binder polymer solution (A1)]
(1) shown in Table 1 was charged into a flask equipped with a stirrer, a reflux condenser, an inert gas inlet, and a thermometer. The temperature was raised to 80 ° C. in a nitrogen gas atmosphere, and while keeping the reaction temperature at 80 ° C. ± 2 ° C., (2) shown in Table 1 was uniformly added dropwise over 4 hours. After the dropwise addition of (2), stirring was continued at 80 ° C. ± 2 ° C. for 6 hours to obtain a binder polymer solution (solid content: 45 mass%) (A1). The weight average molecular weight of the binder polymer was 65000, the acid value was 91 mgKOH / g, the hydroxyl value was 2 mgKOH / g, and the glass transition temperature (Tg) was 70 ° C.

[Preparation of binder polymer solution (A2)]
A binder polymer solution (A2) was prepared in the same manner as the binder polymer solution (A1) except that the charged amount of (2) shown in Table 1 was changed. The weight average molecular weight of the binder polymer was 180,000, the acid value was 91 mgKOH / g, the hydroxyl value was 2 mgKOH / g, and the glass transition temperature (Tg) was 75 ° C.

[Preparation of binder polymer solution (A3)]
A binder polymer solution (A3) was prepared in the same manner as the binder polymer solution (A1) except that the charged amount of (2) shown in Table 1 was changed. The weight average molecular weight of the binder polymer (A3) was 290000, the acid value was 91 mgKOH / g, the hydroxyl value was 2 mgKOH / g, and the glass transition temperature (Tg) was 77 ° C.

The weight average molecular weight (Mw) was measured by gel permeation chromatography (GPC), and was derived by conversion using a standard polystyrene calibration curve. The GPC conditions are shown below.
GPC condition Pump: Hitachi L-6000 type (product name, manufactured by Hitachi, Ltd.)
Column: Gelpack GL-R420, Gelpack GL-R430, Gelpack GL-R440 (above, manufactured by Hitachi Chemical Co., Ltd., product name)
Eluent: Tetrahydrofuran Measurement temperature: 40 ° C
Flow rate: 2.05 mL / min Detector: Hitachi L-3300 type RI (manufactured by Hitachi, Ltd., product name)

[Measurement method of acid value]
The acid value was measured by a neutralization titration method based on JIS K0070 as shown below. First, the binder polymer solution was heated at 130 ° C. for 1 hour to remove volatile matter, thereby obtaining a solid content. Then, after accurately weighing 1 g of the solid binder polymer, 30 g of acetone was added to the binder polymer, and this was uniformly dissolved to obtain a resin solution. Next, an appropriate amount of an indicator, phenolphthalein, was added to the resin solution, and neutralization titration was performed using a 0.1 mol / L potassium hydroxide aqueous solution. And the acid value was computed by following Formula.
Acid value = 0.1 × V × f ₁ × 56.1 / (Wp × I / 100)
In the formula, V is a titration amount (mL) of 0.1 mol / L potassium hydroxide aqueous solution used for titration, f ₁ is a factor (concentration conversion factor) of 0.1 mol / L potassium hydroxide aqueous solution, and Wp is a measured resin. The mass (g) and I of the solution indicate the proportion (mass%) of the non-volatile content in the measured resin solution.

[Measurement method of hydroxyl value]
The hydroxyl value was measured by a neutralization titration method based on JIS K0070 as shown below. First, the binder polymer solution was heated at 130 ° C. for 1 hour to remove volatile matter, thereby obtaining a solid content. Then, after accurately weighing 1 g of the above-mentioned solid binder polymer, the binder polymer was put into an Erlenmeyer flask, 10 mL of 10 mass% acetic anhydride pyridine solution was added to uniformly dissolve the binder polymer, and heated at 100 ° C. for 1 hour. . After heating, 10 mL of water and 10 mL of pyridine were added and heated at 100 ° C. for 10 minutes. Then, 0.5 mol / L potassium hydroxide was used using an automatic titrator (product name: COM-1700, manufactured by Hiranuma Sangyo Co., Ltd.). Neutralization titration was performed using an ethanol solution. And the hydroxyl value was computed by following Formula.
Hydroxyl value = (AB) × f ₂ × 28.05 / S + D
In the formula, A is the amount (mL) of 0.5 mol / L potassium hydroxide ethanol solution used for the blank test, B is the amount (mL) of 0.5 mol / L potassium hydroxide ethanol solution used for titration, f ₂ Is a factor (concentration conversion factor) of 0.5 mol / L potassium hydroxide ethanol solution, S is the mass (g) of the binder polymer, and D is the acid value.
In the blank test, the above process was performed without adding a binder polymer.

Example 1
[Preparation of coating solution containing photosensitive resin composition]
The materials shown in Table 2 were mixed for 15 minutes using a stirrer to prepare a coating solution containing a photosensitive resin composition for forming a protective film.

[Production of photosensitive element]
A polyethylene terephthalate film having a thickness of 50 μm was used as the support film. Using a comma coater, the coating solution containing the photosensitive resin composition prepared above was uniformly applied on the support film. The solvent was removed by drying with a hot air convection dryer at 100 ° C. for 3 minutes to form a photosensitive layer (photosensitive resin composition layer) made of the photosensitive resin composition. The resulting photosensitive layer had a thickness of 5 μm.

Next, a 25 μm thick polyethylene film was laminated as a protective film on the obtained photosensitive layer to produce a photosensitive element for forming a protective film.

[Preparation of bending resistance test sample]
An ITO electrode pattern of L / S = 200/30 μm was produced on a PET film with ITO (manufactured by Nitto Denko Corporation, product name: V100-G2YC5B) with a laser patterning device. Dispense a conductive paste (product name: DY-150H-30, manufactured by Toyobo Co., Ltd.) onto the electrode pad, dry with a hot air convection dryer at 140 ° C for 30 minutes to dry the solvent, and anneal ITO. The ITO-TEG for bending resistance test was prepared.

The photosensitive element obtained above was subjected to a roll temperature of 110 ° C., a substrate feed rate of 0.6 m / min, and a pressure of pressure (cylinder pressure) of 0.4 MPa so that ITO of ITO-TEG and the photosensitive layer were in contact with each other. A laminate was prepared by laminating on ITO-TEG and laminating a photosensitive layer and a polyethylene terephthalate film on ITO-TEG.

Using the conveyor UV device (manufactured by Oak Manufacturing Co., Ltd., device name: QRM-2317F-00), an exposure amount of 500 mJ / m ² (i (Measured value at a line (wavelength 365 nm)) was irradiated with ultraviolet rays. Next, the support film laminated on the photosensitive layer was peeled and removed to obtain a sample for bending resistance test in which a cured product of the photosensitive layer having a thickness of 5 μm was formed.

[Flexibility test]
Next, a bending resistance test was performed.
<Outside bending (ITO stretching direction)>
Set the test specimen for flexibility test to the planar load U-shaped stretch tester (Yuasa System Equipment Co., Ltd., device name: DLDMMLH-FS) so that the curvature radii are 0.5mm, 1mm and 1.5mm respectively. , And was bent once in the direction in which the ITO stretches at 11 rpm.
<Inward bending (ITO compression direction)>
Set the sample for flexibility test on the planar load U-shaped stretch tester (Yuasa System Equipment Co., Ltd., device name: DLDMMLH-FS) so that the radius of curvature is 1 mm, and in the direction that ITO compresses at 60 rpm It was bent 200,000 times.

The bending resistance was evaluated according to the following criteria. The results are shown in Table 2.
<Number of cracks>
The bent sample was observed with an optical microscope (manufactured by Olympus Corporation, apparatus name: BX51), and the number of cracks was measured.
<Rate change rate>
Before and after the bending resistance test, the resistance value was measured by pressing a tester against the conductive paste, and the resistance value change rate was calculated from the following formula.
Resistance value change rate (%) = {(resistance value before bending resistance test−resistance value after bending resistance test) / resistance value before bending resistance test} × 100
In addition, the case where the resistance value exceeded the detection upper limit of the tester and measurement was impossible was defined as “OL”.

[Measurement of light transmittance, hue and optical properties of photosensitive layer]
Laminator (manufactured by Hitachi Chemical Co., Ltd., trade name: HLM-3000 type) so that the photosensitive layer is in close contact with a 0.7 mm thick glass substrate while peeling the polyethylene film which is the protective film of the obtained photosensitive element. ), The photosensitive layer and the support film are laminated on the glass substrate, with a roll temperature of 110 ° C., a substrate feed rate of 0.6 m / min, and a pressure bonding pressure (cylinder pressure) of 0.4 MPa. A laminate was prepared.

Next, using a parallel light exposure machine (EXM1201, manufactured by Oak Manufacturing Co., Ltd.), the photosensitive layer of the obtained laminate was exposed at an exposure amount of 1000 mJ / m ² (i-line (wavelength 365 nm)). Measured value), and irradiated with ultraviolet rays. Thereafter, the support film was removed to obtain a sample for light transmittance measurement having a cured film of a photosensitive layer having a thickness of 5 μm.

Next, for the obtained sample, the light transmittance was measured in a measurement wavelength range of 400 to 700 nm using a UV-visible spectrophotometer (U-3310) manufactured by Hitachi High-Technologies Corporation, and the minimum value was calculated. . Further, for the obtained sample, L *, a *, and b * in the CIELAB color system were measured with a light source D65 using a spectrocolorimeter CM-5 manufactured by Konica Minolta. Moreover, about the obtained sample, the total light transmittance and haze were measured using the haze meter and the haze meter (Nippon Denshoku Industries Co., Ltd. make, apparatus name: NDH7000). The results are shown in Table 2.

(Examples 2 to 4 and Comparative Example 1)
A protective film was formed using a photosensitive element in the same manner as in Example 1 except that the composition of the photosensitive resin composition was changed as shown in Table 2, and the above tests and measurements were performed. The results are shown in Table 2.

In addition, the symbol of the component in Table 2 shows the following meaning.
(B) Component TMPTA: Trimethylolpropane triacrylate (manufactured by Nippon Kayaku Co., Ltd.)
T-1420 (T): Ditrimethylolpropane tetraacrylate (manufactured by Nippon Kayaku Co., Ltd.)
(C) Component BDK (IRGACURE 651): 2,2-dimethoxy-1,2-diphenylethane-1-one (manufactured by BASF Japan Ltd.)
(D) Component PM-21: Phosphate ester containing photopolymerizable unsaturated bond (Nippon Kayaku Co., Ltd.)
(Other ingredients)
DEAA: Diethylacrylamide (manufactured by KJ Chemicals)
ADDITIVE 8032: Organically modified silicone oil (Toray Dow Corning Co., Ltd.)
Antage W-500: 2,2′-methylene-bis (4-ethyl-6-tert-butylphenol) (manufactured by Kawaguchi Chemical Co., Ltd.)

DESCRIPTION OF SYMBOLS 1A, 1B ... Photosensitive element, 2 ... Support film, 3 ... Photosensitive layer, 4 ... Protective film, 5, 5A, 5B, 5C ... Touch panel, 6 ... Base material, 7 ... Touch screen area, 8 ... 1st transparent Electrode, 9 ... second transparent electrode, 10 ... metal wiring, 11 ... connection electrode, 12 ... connection terminal, 13 ... protective film, 14 ... touch panel substrate, R1, R2, R3 ... bending region.

Claims (5)

A protective film for a touch panel electrode obtained by curing a photosensitive resin composition containing a binder polymer having a weight average molecular weight of 100,000 or more, a photopolymerizable compound, and a photopolymerization initiator. The touchscreen electrode protective film according to claim 1, which is provided in a bent region of the touchscreen. The protective film for a touch panel electrode according to claim 1 or 2, wherein the minimum value of light transmittance at 400 to 700 nm is 90% or more. The protective film for a touch panel electrode according to any one of claims 1 to 3, wherein the thickness is 50 µm or less. A substrate;
An electrode provided on the substrate;
The protective film according to any one of claims 1 to 4 provided on the electrode;
Touch panel equipped with.

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