JP2018005249A - Photosensitive transparent material for protective film of touch panel electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photosensitive transparent material for a protective film of a touch panel electrode that makes it possible to form a transparent protective film having a low dielectric constant on a touch panel electrode.SOLUTION: There is provided a photosensitive transparent material for a protective film of a touch panel electrode containing (A) a binder polymer containing a structural unit a1 derived from (meth)acrylic acid and a structural unit a2 derived from (meth)acrylic acid alkyl ester having an alkyl group with 4 to 18 carbon atoms, (B) a photopolymerizable compound having at least 3 ethylenic unsaturated groups and acid value of 5 mgKOH/g or less, and (C) a photoinitiator.SELECTED DRAWING: None

Description

  The present invention relates to a photosensitive transparent material for a protective film of a touch panel electrode used for a protective film of an electrode for a touch panel.

  Liquid crystal display elements and touch panels (touch sensors) are used in 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 / FA devices. These liquid crystal display elements and touch panels are provided with electrodes made of a transparent conductive electrode material. As the transparent conductive electrode material, ITO (Indium-Tin-Oxide), indium oxide and tin oxide are known, and since these materials exhibit high visible light transmittance, they are used as electrode materials for substrates for liquid crystal display elements. It has become mainstream.

  Various types of touch panels have already been put into practical use, but in recent years, the use of capacitive touch panels has progressed. In a capacitive touch panel, when a fingertip (conductor) contacts the touch input surface, the fingertip and the conductive film are capacitively coupled to form a capacitor. For this reason, the capacitive touch panel detects the coordinates by capturing the change in charge at the contact position of the fingertip.

  In particular, the projected capacitive touch panel can detect multiple fingertips, so it has a good operability to give complex instructions. Use as an input device on a display surface in a device having a small display device such as a music player is advancing.

  In general, in a projected capacitive touch panel, a plurality of X electrodes and a plurality of Y electrodes orthogonal to the X electrodes have a two-layer structure in order to express two-dimensional coordinates based on the X and Y axes. ITO (Indium-Tin-Oxide) is used as the electrode.

  By the way, since the frame area of the touch panel is an area where the touch position cannot be detected, it is an important element of the product value to reduce the area of the frame area. In order to reduce the frame area, it is necessary to narrow the widths of the bus electrodes and the lead lines. Since the conductivity of ITO is not sufficiently high, generally, a treatment for increasing the conductivity is performed by forming a metal layer such as aluminum / molybdenum or copper on the bus electrode.

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

  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. However, since this method uses a plasma CVD method, there is a problem that a high temperature treatment is required and the base material is limited. There is also a problem that the manufacturing cost becomes high.

  As a method of providing a resist film at a necessary location, a method is known 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 Documents 2 to 2). 3).

JP 2011-28594 A JP-A-7-253666 JP 2005-99647 A

  In a transparent protective film for a touch panel electrode using a photosensitive resin composition, many protective films having a thickness of 10 μm or less and having transparency, developability and rust resistance have been studied. However, in order to improve the sensitivity of the touch sensor, there has been no example in which a low dielectric constant of the electrode transparent protective film for a touch panel has been studied.

  An object of the present invention is to provide a photosensitive transparent material for a protective film of a touch panel electrode which is a transparent protective film formed on a predetermined touch panel electrode and has a low dielectric constant and can form a transparent protective film. .

  In order to solve the above-mentioned problems, the present inventors have intensively studied, and as a result, a carboxyl group molecule that causes a dielectric constant to increase by copolymerizing a long-chain alkyl with a binder polymer used in the photosensitive resin composition. Inhibition of movement and suppression of orientational polarization of carboxyl groups led to a reduction in dielectric constant. Moreover, it discovered that the photosensitive resin composition containing the said binder polymer, a specific photopolymerizable compound, and a photoinitiator had sufficient transparency, developability, and a low dielectric constant.

The present invention is [1] a photosensitive transparent material for a protective film of a touch panel electrode, having (A) a structural unit a1 derived from (meth) acrylic acid and an alkyl group having 4 to 18 carbon atoms (meth). A binder polymer containing a structural unit a2 derived from an alkyl acrylate ester, (B) a photopolymerizable compound having at least three ethylenically unsaturated groups and an acid value of 5 mgKOH / g or less, (C) photopolymerization initiation The present invention relates to a photosensitive transparent material for a protective film of a touch panel electrode containing an agent.
The binder polymer used in the present invention has a carboxyl group derived from (meth) acrylic acid, an acid value of 30 to 190 mgKOH / g, and a (meth) acrylic acid alkyl ester having an alkyl group having 4 to 18 carbon atoms. (A) a binder polymer, (B) a photopolymerizable compound having at least three ethylenically unsaturated groups, and having an acid value of 5 mgKOH / g or less, and (C) a photopolymerization initiator, A photosensitive layer made of a photosensitive resin composition containing, and curing a predetermined portion of the photosensitive layer by irradiation with actinic rays, and then removing the photosensitive layer other than the predetermined portion to cover a part or all of the electrode The photosensitive transparent material for the protective film of the touch panel electrode which consists of the hardened | cured material of the said photosensitive resin composition of 10 micrometers or less is preferable.

In this specification, the touch panel electrode includes not only electrodes in the sensing area of the touch panel but also metal wiring in the frame area. Either or both of the electrodes provided with the protective layer may be provided.

The present invention also relates to [2] a photosensitive transparent material for a protective film of a touch panel electrode according to the above [1], which has a visible light transmittance of 90% or more when a film having a thickness of 10 μm is formed.
Moreover, this invention is [3] The photosensitive transparent for the protective film of the touchscreen electrode of [2] whose relative dielectric constant when forming a cured film is 3.1-3.8. Regarding materials.
[4] The present invention also includes [4] the binder polymer polymerized in such a manner that a polymerization molar ratio of the structural units a1 and a2 of the binder polymer is in the range of a1 / a2 = 15/85 to 40/60. It is related with the photosensitive transparent material for protective films of the touchscreen electrode in any one of [3].
The present invention also provides: [5] The (B) photopolymerizable compound is derived from a (meth) acrylate compound having a skeleton derived from pentaerythritol, a (meth) acrylate compound having a skeleton derived from dipentaerythritol, or derived from trimethylolpropane. It relates to the photosensitive transparent material for protective films of the touchscreen electrode in any one of said [1]-[4] containing the at least 1 sort (s) of compound selected from the group which consists of a (meth) acrylate compound which has these skeletons.

Moreover, this invention is [6] For the protective film of the touchscreen electrode in any one of said [1]-[5] in which the said (C) photoinitiator contains an oxime ester compound or a phosphine oxide compound. The present invention relates to a photosensitive transparent material.
From the viewpoint of sufficiently ensuring the visibility of the touch panel as described above, the photosensitive layer preferably has a visible light transmittance of 90% or more. In this case, it is suitable for forming a protective film that covers the electrodes in the sensing region.

  By the way, it is desirable that the transparency of the protective film is higher in consideration of the visibility and appearance of the touch panel. However, on the other hand, the present inventors have found that when patterning a thin photosensitive layer having high transparency, the resolution tends to decrease. The present inventors consider that the reason is that when the thickness of the photosensitive layer is reduced, it is easily affected by light scattering from the base material and halation occurs.

  On the other hand, in the present invention, the photopolymerization initiator contains an oxime ester compound or a phosphine oxide compound, thereby enabling pattern formation with sufficient resolution.

  The reason why the above effect can be obtained is that the oxime moiety contained in the oxime ester compound or the phosphine oxide moiety contained in the phosphine oxide compound has a relatively high photolysis efficiency but does not decompose with slight light leakage. The present inventors infer that the influence of leakage light is suppressed because of having a large threshold.

  In the method for forming a protective film for an electrode for a touch panel according to the present invention, a support film and the photosensitive resin composition provided on the support film (including at least the above (A), (B), and (C)) A photosensitive element provided with a photosensitive layer made of the above is prepared, and the photosensitive layer of the photosensitive element is transferred onto a substrate to provide the photosensitive layer. In this case, by using the photosensitive element, a roll-to-roll process can be easily realized, and the solvent drying process can be shortened, which can greatly contribute to shortening of the manufacturing process and cost reduction.

  According to the present invention, a protective film having sufficient transparency, developability, and low dielectric constant formed on a predetermined touch panel electrode, and the protective film photosensitivity of the touch panel electrode capable of forming such a protective film. A transparent material can be provided.

  Moreover, according to the photosensitive transparent material for the protective film of the touch panel electrode of the present invention, it is possible to reduce electrical noise between the electrodes by having a low dielectric constant, and to improve the sensitivity as a touch sensor. it can.

  Hereinafter, embodiments for carrying out the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

  The photosensitive transparent material for a protective film of a touch panel electrode of the present invention is a photosensitive element in which a photosensitive resin composition used as a protective film for a touch panel electrode is provided on a support film.

  As a support film, the film of about 5-100 micrometers in thickness which consists of a polyethylene terephthalate, a polycarbonate, polyethylene, a polypropylene, polyether sulfone etc. is mentioned, for example.

  The thickness of the support film is preferably 5 to 100 μm, and more preferably 10 to 70 μm, from the viewpoints of ensuring coverage and suppressing a decrease in resolution when exposed through the support film.

  The photosensitive resin composition according to the present invention is a binder polymer obtained by copolymerizing (meth) acrylic acid having a carboxyl group, an acid value of 100 to 190 mgKOH / g, and an alkyl group having 4 to 18 carbon atoms. (Hereinafter also referred to as component (A)), a photopolymerizable compound (hereinafter also referred to as component (B)) having at least three ethylenically unsaturated groups and an acid value of 5 mgKOH / g or less, A polymerization initiator (hereinafter also referred to as component (C)).

  In the present embodiment, by using a combination of the component (A) having an acid value within the above range and the component (B) that satisfies the above conditions, while ensuring developability and adhesion to the substrate, A protective film having a sufficient antirust property can be formed with a thickness of 10 μm or less.

  In this embodiment, the component (A) is a co-polymer containing a structural unit derived from (a1) (meth) acrylic acid and (a2) a (meth) acrylic acid alkyl ester having an alkyl group having 4 to 18 carbon atoms. Polymers are preferred. Here, (meth) acrylic acid means acrylic acid and methacrylic acid, and similarly (meth) acrylic acid alkyl ester means acrylic acid alkyl ester and methacrylic acid alkyl ester.

  In the present embodiment, from the viewpoint of developability and low dielectric constant, the structural unit derived from the above (a1) (meth) acrylic acid and (a2) a (meth) acrylic acid alkyl ester having a C 4-18 alkyl group. It is preferable to include a binder polymer that is polymerized in a range of a1 / a2 = 15/85 to 40/60 in terms of the molar ratio of copolymerization with respect to a total amount of 100 mol%, and a1 / a2 = 25/75 More preferably, it is -40/60.

  Examples of the (meth) acrylic acid alkyl ester include (meth) acrylic acid butyl ester, (meth) acrylic acid lauryl ester, and (meth) acrylic acid stearyl ester.

  The molecular weight of the binder polymer as component (A) is not particularly limited, but from the viewpoint of coating properties, coating film strength, and developability, it is usually a weight average molecular weight (a value measured in terms of standard polystyrene using GPC). ) Is preferably 10,000 to 200,000, more preferably 30,000 to 150,000, and even more preferably 50,000 to 100,000.

  The acid value of the binder polymer as the component (A) can be developed with various known developing solutions in the step of selectively removing the photosensitive resin composition layer in the development step, From the viewpoint of improving resistance to corrosive components such as moisture and salt when functioning as a protective film, a range of 30 to 190 mgKOH / g is preferable.

  Moreover, it can develop using the aqueous alkali solution containing water, an alkali metal salt, and surfactant by making the acid value of a binder polymer into 30-190 mgKOH / g. When the acid value is less than 30 mgKOH / g, development tends to be difficult, and when it exceeds 190 mgKOH / g, the dielectric constant tends to increase.

  The photopolymerizable compound as component (B) has at least three ethylenically unsaturated groups, and the photopolymerizable compound having an acid value of 5 mgKOH / g or less includes, for example, trimethylolpropane tri (meth) acrylate. Α, β-unsaturated saturated carboxylic acids to polyhydric alcohols such as tetramethylol methane tri (meth) acrylate, tetramethylol methane tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate A compound obtained by reacting an acid; a compound obtained by adding an α, β-unsaturated carboxylic acid to a glycidyl group-containing compound such as trimethylolpropane triglycidyl ether triacrylate.

  In the photosensitive resin composition of the present embodiment, from the viewpoint of dielectric constant and ease of development, a (meth) acrylate compound having a skeleton derived from pentaerythritol, a (meth) acrylate compound having a skeleton derived from dipentaerythritol, It preferably contains at least one selected from the group consisting of (meth) acrylate compounds having a skeleton derived from methylolpropane, and has a (meth) acrylate compound having a skeleton derived from dipentaerythritol and a skeleton derived from trimethylolpropane. More preferably, it contains at least one selected from (meth) acrylate compounds.

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

  The (meth) acrylate compound having a skeleton derived from trimethylolpropane means an esterified product of trimethylolpropane and (meth) acrylic acid, and the esterified product is modified with an alkyleneoxy group. Also included are compounds. In the above esterified product, the number of ester bonds in one molecule is preferably 3, but a compound having 1 to 2 ester bonds may be mixed.

  Said compound can be used individually by 1 type or in combination of 2 or more types.

  The content of the component (A) and the component (B) in the photosensitive resin composition of the present embodiment is such that the component (A) is 40 to 80 with respect to 100 parts by mass of the total amount of the components (A) and (B). It is preferable that a mass part and (B) component are 20-60 mass parts, It is more preferable that (A) component is 50-70 mass parts, (B) component is 30-50 mass parts, (A) More preferably, the component is 55 to 65 parts by mass, and the component (B) is 35 to 45 parts by mass.

  By setting the content of the component (A) within the above range, sufficient sensitivity can be obtained while sufficiently ensuring the coatability or film properties of the photosensitive element, and the photocurability, developability, and low dielectric constant. A sufficient rate can be ensured.

  Examples of the photopolymerization initiator (C) include benzophenone, N, N′-tetramethyl-4,4′-diaminobenzophenone (Michler ketone), N, N′-tetraethyl-4,4′-diaminobenzophenone. 4-methoxy-4′-dimethylaminobenzophenone, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1,2-methyl-1- [4- (methylthio) phenyl] -2 -Aromatic ketones such as morpholino-propanone-1, 2-ethylanthraquinone, phenanthrenequinone, 2-tert-butylanthraquinone, octamethylanthraquinone, 1,2-benzanthraquinone, 2,3-benzanthraquinone, 2-phenylanthraquinone, 2,3-diphenylanthraquinone, 1-chloroa Quinones such as nthraquinone, 2-methylanthraquinone, 1,4-naphthoquinone, 9,10-phenantharaquinone, 2-methyl 1,4-naphthoquinone, 2,3-dimethylanthraquinone; benzoin methyl ether, benzoin ethyl ether, benzoin Benzoin ether compounds such as phenyl ether, benzoin compounds such as benzoin, methylbenzoin, and ethylbenzoin; 1,2-octanedione, 1- [4- (phenylthio)-, 2- (O-benzoyloxime)], ethanone, 1 -[9-ethyl-6- (2-methylbenzoyl) -9H-carbazol-3-yl]-, oxime ester compounds such as 1- (0-acetyloxime); benzyl derivatives such as benzyldimethyl ketal; 2- ( o-chlorophenyl) -4,5-diphenyl Imidazole dimer, 2- (o-chlorophenyl) -4,5-di (methoxyphenyl) imidazole dimer, 2- (o-fluorophenyl) -4,5-diphenylimidazole dimer, 2- (o -Methoxyphenyl) -4,5-diphenylimidazole dimer, 2,4,5-triarylimidazole dimer such as 2- (p-methoxyphenyl) -4,5-diphenylimidazole dimer; 9- Examples include acridine derivatives such as phenylacridine and 1,7-bis (9,9′-acridinyl) heptane; N-phenylglycine, N-phenylglycine derivatives, coumarin compounds, and oxazole compounds. Further, the substituents of the aryl groups of two 2,4,5-triarylimidazoles may be the same to give the target compound, or differently give an asymmetric compound. Moreover, you may combine a thioxanthone type compound and a tertiary amine compound like the combination of diethyl thioxanthone and dimethylaminobenzoic acid.

  Among these, an oxime ester compound or a phosphine oxide compound is preferable from the transparency of the protective film to be formed and the pattern forming ability when the film thickness is 10 μm or less. Examples of the oxime ester compound include compounds represented by the following general formula (C-1) and general formula (C-2). From the viewpoint of fast curability and transparency, the following general formula (C-1) The compound represented by these is preferable.

In the general formula (C-1), R ¹ is an alkyl group having 1 to 12 carbon atoms, an organic group containing a cycloalkyl group having 3 to 20 carbon atoms, an alkanoyl group having 2 to 12 carbon atoms, or a double bond. An alkenoyl group having 4 to 6 carbon atoms, a benzoyl group, an alkoxycarbonyl group having 2 to 6 carbon atoms or a phenoxycarbonyl group which is not conjugated with a carbonyl group is shown. In addition, unless the effect of this invention is inhibited, you may have a substituent on the aromatic ring in the said general formula (C-1).

In the general formula (C-1), R ¹ is preferably an organic group containing an alkyl group having 1 to 12 carbon atoms or a cycloalkyl group having 3 to 20 carbon atoms, and an alkyl group having 3 to 10 carbon atoms. Or an organic group containing a cycloalkyl group having 4 to 15 carbon atoms, particularly an organic group containing an alkyl group having 4 to 8 carbon atoms or a cycloalkyl group having 4 to 10 carbon atoms. preferable.

In the general formula (C-2), R ² is a halogen atom, an alkyl group having 1 to 12 carbon atoms, a cyclopentyl group, a cyclohexyl group, a phenyl group, a benzyl group, a benzoyl group, an alkanoyl group having 2 to 12 carbon atoms, An alkoxycarbonyl group having 2 to 12 carbon atoms or a phenoxycarbonyl group; R ³ represents an organic group containing an alkyl group having 1 to 12 carbon atoms and a cycloalkyl group having 3 to 20 carbon atoms; and R ⁴ is independently selected. In addition, a halogen atom, an alkyl group having 1 to 12 carbon atoms, a cyclopentyl group, a cyclohexyl group, a phenyl group, a benzyl group, a benzoyl group, an alkanoyl group having 2 to 12 carbon atoms, an alkoxycarbonyl group having 2 to 12 carbon atoms, or phenoxy Represents a carbonyl group, R ⁵ represents an alkyl group having 2 to 20 carbon atoms or an arylene group, and p1 represents an integer of 0 to 3. The When p1 is 2 or more, a plurality of R ⁴ may be the same or different. Note that carbazole may have a substituent as long as the effects of the present invention are not impaired.

In the general formula (C-2), R ² is preferably an alkyl group having 1 to 12 carbon atoms, more preferably an alkyl group having 1 to 8 carbon atoms, and an alkyl group having 1 to 4 carbon atoms. It is particularly preferred that

In the above general formula (C-2), R ³ is preferably an organic group containing an alkyl group having 1 to 8 carbon atoms and a cycloalkyl group having 4 to 15 carbon atoms, an alkyl group having 1 to 4 carbon atoms, A cycloalkyl group having 4 to 10 carbon atoms is more preferable.

  Examples of the compound represented by the general formula (C-1) and the compound represented by the general formula (C-2) include 1,2-octanedione, 1- [4- (phenylthio)-, 2- (O -Benzoyloxime)], ethanone, 1- [9-ethyl-6- (2-methylbenzoyl) -9H-carbazol-3-yl]-, 1- (O-acetyloxime) and the like. 1,2-octanedione, 1- [4- (phenylthio)-, 2- (O-benzoyloxime)] is IRGACURE-OXE01 (trade name, manufactured by BASF Corp.) as etanone, 1- [9-ethyl- 6- (2-Methylbenzoyl) -9H-carbazol-3-yl]-, 1- (O-acetyloxime) is commercially available as IRGACURE-OXE02 (trade name, manufactured by BASF). These are used alone or in combination of two or more.

  Of the above general formula (C-1), 1,2-octanedione, 1- [4- (phenylthio)-, 2- (O-benzoyloxime)] is particularly preferable.

  As said phosphine oxide compound, the compound represented by the following general formula (C-3) and general formula (C-4) is mentioned. From the viewpoint of fast curability and transparency, a compound represented by the following general formula (C-3) is preferred.

In said general formula (C-3), R < ⁶ >, R < ⁷ > and R < ⁸ > show a C1-C20 alkyl group or aryl group each independently. In general formula (C-4), R <^9> , R < ¹⁰ > and R < ¹¹ > show a C1-C20 alkyl group or an aryl group each independently.

When R ⁶ , R ⁷ or R ⁸ in the general formula (C-3) is an alkyl group having 1 to 20 carbon atoms, the alkyl group may be linear, branched, or cyclic. Moreover, it is more preferable that the alkyl group has 5 to 10 carbon atoms. When R ⁹ , R ¹⁰ or R ¹¹ in the general formula (C-4) is an alkyl group having 1 to 20 carbon atoms, the alkyl group may be any of linear, branched, and cyclic Moreover, it is more preferable that carbon number of this alkyl group is 5-10.

When R ⁶ , R ⁷ or R ⁸ in the general formula (C-3) is an aryl group, the aryl group may have a substituent. Examples of the substituent include an alkyl group having 1 to 6 carbon atoms and an alkoxy group having 1 to 4 carbon atoms. When R ⁹ , R ¹⁰ or R ¹¹ in the general formula (C-4) is an aryl group, the aryl group may have a substituent. Examples of the substituent include an alkyl group having 1 to 6 carbon atoms and an alkoxy group having 1 to 4 carbon atoms.

Among these, as for the said general formula (C-3), it is preferable that R < ⁶ >, R < ⁷ > and R < ⁸ > are aryl groups, and the compound represented by general formula (C-4) is R < ⁹ >, R <^10>. And R ¹¹ is preferably an aryl group.

  The compound represented by the general formula (C-3) includes 2,4,6-trimethylbenzoyl-diphenyl-phosphine because of the transparency of the protective film to be formed and the pattern forming ability when the film thickness is 10 μm or less. Oxides are preferred. 2,4,6-Trimethylbenzoyl-diphenyl-phosphine oxide is commercially available, for example, as DAROCUR-TPO (trade name, manufactured by BASF Japan).

  The content of the photopolymerization initiator that is the component (C) is preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the total amount of the components (A) and (B), and is 1 to 2 parts by mass. I prefer to be a part.

  By making the content of the component (C) within the above range, the photosensitivity is sufficient, and the absorption on the surface of the composition is increased at the time of exposure, and the internal photocuring becomes insufficient. Problems such as a reduction in visible light transmittance can be suppressed.

  The visible light transmittance of the cured film of the photosensitive resin composition of the present embodiment is preferably 90% or more, more preferably 92% or more, and even more preferably 95% or more.

  Here, the visible light transmittance of the photosensitive resin composition is determined as follows. First, the photosensitive resin composition is applied onto a support film so that the thickness after drying is 10 μm, and dried to form a photosensitive resin composition layer. Next, it laminates on a glass substrate using a laminator so that the photosensitive resin composition layer contacts. Thus, a measurement sample in which the photosensitive resin composition layer and the support film are laminated on the glass substrate is obtained. Next, after irradiating the obtained sample for measurement with ultraviolet rays, the photosensitive resin composition layer is photocured and the support film is peeled off, and then transmitted through a measurement wavelength region of 300 to 800 nm using an ultraviolet-visible spectrophotometer. Measure the rate.

  If the transmittance in the wavelength range of 400 to 700 nm, which is a light beam in a general visible light wavelength range, is 90% or more, for example, the transparent electrode of the display part of the touch panel (touch sensor) is protected, or the touch panel (touch When the protective layer is visible from the edge of the display part when the metal layer (for example, a layer in which a copper layer is formed on the ITO electrode) is protected, the display quality, hue, A decrease in luminance can be sufficiently suppressed.

  The photosensitive resin composition of the present embodiment is preferably used after being formed on a photosensitive film. By laminating the photosensitive film on the substrate having the touch panel electrode, the roll-to-roll process can be easily realized, and the solvent drying process can be shortened. it can.

  The photosensitive film (photosensitive element) can be formed by using the photosensitive resin composition of the present embodiment as a coating solution, and applying and drying the coating composition on a support film. The coating liquid can be obtained by uniformly dissolving or dispersing each component constituting the photosensitive resin composition of the present embodiment described above in a solvent.

  The solvent is not particularly limited and known ones can be used. For example, acetone, methyl ethyl ketone, methyl isobutyl ketone, toluene, methanol, ethanol, propanol, butanol, methylene glycol, ethylene glycol, propylene glycol, ethylene glycol monomethyl ether, Examples include ethylene glycol monoethyl ether, propylene glycol monomethyl ether, chloroform, and methylene chloride. These solvents may be used alone or as a mixed solvent composed of two or more solvents.

  Application methods include, for example, doctor blade coating method, wire 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.

  Although there is no restriction | limiting in particular in drying conditions, It is preferable that drying temperature shall be 60-130 degreeC, and it is preferable that drying time shall be 0.5-30 minutes.

  The thickness of the photosensitive layer is 10 μm or less after drying so that the step on the surface of the touch panel (touch sensor) caused by the formation of a partial electrode protective film is minimized as much as possible to exert a sufficient effect on electrode protection. Is preferred.

  Next, a method for forming a protective film for an electrode for a touch panel according to the present invention will be described.

  The method for forming a protective film for a touch panel electrode according to the present embodiment includes a first step of providing a photosensitive layer made of the photosensitive resin composition according to the present embodiment on a substrate having a touch panel electrode, and a photosensitive layer. A protective film made of a cured product of a photosensitive resin composition that removes a photosensitive layer other than the predetermined portion after exposure and covers a part or all of the electrode after the second step of curing the predetermined portion by irradiation with actinic light A third step of forming.

  There is no restriction | limiting in particular in the base material used by this embodiment, Substrates, such as a glass plate, a plastic plate, a ceramic board, generally used for touchscreens (touch sensor) are mentioned. On this substrate, a touch panel electrode to be a target for forming a protective film is provided. Examples of the electrode include electrodes such as ITO, Cu, Al, and Mo, and TFT.

  The base material which has the electrode for touchscreens can be obtained in the following procedures, for example. After forming a metal film by sputtering in the order of ITO and Cu on a substrate 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 iron chloride. After removing with an etching solution such as an aqueous solution, the resist pattern is peeled off.

  In the first step of the present embodiment, the photosensitive layer of the present embodiment is laminated by pressing the photosensitive layer on the surface of the substrate on which the touch panel electrode is provided while heating the photosensitive layer.

  Examples of the pressing means include a pressing roll. The pressure roll may be provided with a heating means so that it can be heat-pressure bonded.

  The heating temperature in the case of thermocompression bonding is preferably 10 to 180 ° C. so that the components of the photosensitive layer are hardly thermally cured or thermally decomposed while ensuring sufficient adhesion between the photosensitive layer and the substrate. It is more preferable to set it to -160 degreeC, and it is still more preferable to set it as 30-150 degreeC.

In addition, the pressure during thermocompression bonding is set to 50 to 1 × 10 ⁵ N / m in terms of linear pressure from the viewpoint of suppressing deformation of the base material while ensuring sufficient adhesion between the photosensitive layer and the base material. Is preferably 2.5 × 10 ^{2 to} 5 × 10 ⁴ N / m, more preferably 5 × 10 ² to 4 × 10 ⁴ N / m.

  If the photosensitive layer is heated as described above, it is not necessary to pre-heat the substrate, but it is preferable to pre-heat the substrate from the viewpoint of further improving the adhesion between the photosensitive layer and the substrate. The preheating temperature at this time is preferably 30 to 180 ° C.

  In this embodiment, instead of using a photosensitive element, the photosensitive resin composition of the present embodiment is applied as a coating liquid to the surface of the substrate touch panel electrode, and dried to form a photosensitive layer. can do.

  In the second step of this embodiment, the photosensitive layer is exposed to actinic rays in a pattern via a photomask.

  At the time of exposure, when the support film on the photosensitive layer is transparent, it can be exposed as it is, and when it is opaque, it is removed and then exposed. From the viewpoint of protecting the photosensitive layer, it is preferable to use a transparent polymer film as the support film, and expose the polymer film while leaving the polymer film remaining.

  As the active light source used for exposure, a known active light source can be used, for example, a carbon arc lamp, an ultrahigh pressure mercury lamp, a high pressure mercury lamp, a xenon lamp, etc. Not limited.

  In the third step of this embodiment, the exposed photosensitive layer is developed with a developing solution to remove the unexposed portion, and from the cured product of the photosensitive resin composition of this embodiment that covers a part or all of the electrode. A protective film is formed. The formed protective film may have a predetermined pattern.

  In addition, after exposure, when the support film is laminated | stacked on the photosensitive layer, after removing it, the image development which removes the unexposed part by a developing solution is performed.

  As a developing method, development is performed by a known method such as spraying, showering, dipping, rocking dipping, brushing, scraping or the like using a known developing solution such as an aqueous alkaline solution, an aqueous developer, an organic solvent, etc. Among them, it is preferable to use an alkaline aqueous solution from the viewpoint of environment and safety.

  Examples of the base of the alkaline aqueous solution include alkali hydroxide (lithium, sodium or potassium hydroxide, etc.), alkali carbonate (lithium, sodium or potassium carbonate or bicarbonate, etc.), alkali metal phosphate (potassium phosphate, etc.) , Sodium phosphate, etc.), alkali metal pyrophosphates (sodium pyrophosphate, potassium pyrophosphate, etc.), tetramethylammonium hydroxide, triethanolamine, etc. Among them, tetramethylammonium hydroxide, etc. are preferred. It is done.

  An aqueous solution of sodium carbonate is also preferably used. For example, a dilute solution of sodium carbonate (0.5 to 5% by mass aqueous solution) at 20 to 50 ° C. is preferably used.

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

  Further, a surfactant, an antifoaming agent, a small amount of an organic solvent for accelerating development, and the like can be mixed in the alkaline aqueous solution.

  Further, the base of the alkaline aqueous solution remaining in the photosensitive layer after development and photocuring is converted into an acid by a known method such as spraying, rocking immersion, brushing or scraping using an organic acid, an inorganic acid or an aqueous acid solution thereof. It can be treated (neutralized).

  Furthermore, the water washing process can also be performed after an acid treatment (neutralization treatment).

  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)]
A flask equipped with a stirrer, reflux condenser, inert gas inlet and thermometer was charged with (1) shown in Table 1, heated to 65 ° C. in a nitrogen gas atmosphere, and the reaction temperature was 65 ° C. ± While keeping at 2 ° C., (2) shown in Table 1 was uniformly added dropwise over 3 hours. After dropping (2), stirring was continued at 79 ° C. ± 2 ° C. for 1 hour to obtain a binder polymer solution (A1) having a weight average molecular weight of about 65900 and an acid value of 163.8 mg KOH / g.

[Preparation of binder polymer solution (A2)]
In the same manner as in the above (A1), a binder polymer solution (A2) having a weight average molecular weight of about 79500 and an acid value of 151.4 mgKOH / g was obtained.

[Preparation of binder polymer solution (A3)]
In the same manner as in the above (A1), a binder polymer solution (A3) having a weight average molecular weight of about 70200 and an acid value of 140.8 mgKOH / g was obtained.

[Preparation of binder polymer solution (A4)]
In the same manner as in the above (A1), a binder polymer solution (A4) having a weight average molecular weight of about 78000 and an acid value of 133.7 mgKOH / g was obtained.

[Preparation of binder polymer solution (A5)]
In the same manner as in the above (A1), a binder polymer solution (A5) having a weight average molecular weight of about 65000 and an acid value of 109.0 mgKOH / g was obtained.

[Preparation of binder polymer solution (A6)]
In the same manner as in the above (A1), a binder polymer solution (A6) having a weight average molecular weight of about 72000 and an acid value of 186.6 mgKOH / g was obtained.

[Preparation of binder polymer solution (A7)]
In the same manner as in the above (A1), a binder polymer solution (A7) having a weight average molecular weight of about 60400 and an acid value of 174.5 mgKOH / g was obtained.

なお、重量平均分子量（Ｍｗ）は、ゲルパーミエーションクロマトグラフィー法（ＧＰＣ）によって測定し、標準ポリスチレンの検量線を用いて換算することにより導出した。ＧＰＣの条件を以下に示す。
［ＧＰＣ条件］
ポンプ：ＤＰ−８０２０（東ソー株式会社）
カラム：Ｇｅｌｐａｃｋ ＧＬ−Ｗ５２０−Ｓ、Ｇｅｌｐａｃｋ ＧＬ−Ｗ５３０−Ｓ（日立化成株式会社）
溶離液：テトラヒドロフラン
測定温度：２５℃
流量：１．００ｍＬ／分
検出器：ＲＩ−８０２０（東ソー株式会社）

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 conditions]
Pump: DP-8020 (Tosoh Corporation)
Column: Gelpack GL-W520-S, Gelpack GL-W530-S (Hitachi Chemical Co., Ltd.)
Eluent: Tetrahydrofuran Measurement temperature: 25 ° C
Flow rate: 1.00 mL / min Detector: RI-8020 (Tosoh Corporation)

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

[Production of photosensitive element]
A polyethylene terephthalate film having a thickness of 16 μm is used as a support film, and the photosensitive resin composition solution is uniformly applied on the support film using an applicator, and dried with a dust-free dryer at 100 ° C. for 4 minutes to remove the solvent. It removed and the photosensitive layer (photosensitive resin composition layer) which consists of photosensitive resin compositions was formed. The resulting photosensitive layer had a thickness of 10 μm.

[Measurement of transmittance of photosensitive element]
Next, the obtained photosensitive element was used with a laminator (HLM-1500, manufactured by Hitachi Chemical Technoplant Co., Ltd.) so that the photosensitive layer was in contact with a glass substrate having a thickness of 0.5 mm and a length of 4 cm and a width of 4 cm. Then, lamination was performed under the conditions of a roll temperature of 110 ° C., a substrate feed rate of 0.5 m / min, and a pressure bonding pressure (cylinder pressure) of 0.3 MPa, to prepare a laminate in which a photosensitive layer and a support film were laminated on a glass substrate.

Next, a large-sized manual exposure machine (manufactured by Dainippon Screen Mfg. Co., Ltd., MAP 1200L) is used for the photosensitive layer of the obtained laminate, and the exposure amount is 100 mJ / cm ² from the upper side of the photosensitive layer (i-line (wavelength 365 nm )), After irradiating ultraviolet rays, the support film was removed to obtain a transmittance measurement sample having a photosensitive layer (photocured cured film) thickness of 10 μm.

  Next, the visible light transmittance of the obtained sample was measured in a measurement wavelength range of 300 to 800 nm using an ultraviolet-visible spectrophotometer (V-570 type) manufactured by JASCO Corporation. As a measurement result, the total light transmittance was 97% or more, and the 400 nm transmittance was 95%, which was the same transparency as Comparative Example 1.

[Resolution measurement of photosensitive elements]
The obtained photosensitive element is rolled using a laminator (HLM-1500, manufactured by Hitachi Chemical Technoplant Co., Ltd.) so that the photosensitive layer is in contact with a glass substrate having a thickness of 0.5 mm and a length of 4 cm and a width of 4 cm. Lamination was carried out under conditions of a temperature of 110 ° C., a substrate feed rate of 0.5 m / min, and a pressure bonding pressure (cylinder pressure) of 0.3 MPa, to prepare a laminate in which a photosensitive layer and a support film were laminated on a glass substrate.

After producing the laminate obtained above, a photomask having a square opening diameter of 5 to 100 μm, in which actinic light transmitting portions and actinic light shielding portions are alternately patterned, is placed on a support film. , Using a large manual exposure machine (MAP 1200L, manufactured by Dainippon Screen Mfg. Co., Ltd.) with an exposure amount of 20 mJ / cm ² (measured value at i-line (wavelength 365 nm)) from above the photomask surface vertically Irradiated.

  Next, the support film laminated on the photosensitive layer is removed, and dip development is performed at 25 ° C. for 14 seconds using a 2.38 mass% tetramethylammonium hydroxide (TMAH) solution, so that the photosensitive layer is selectively formed. Removed to form a pattern. The substrate surface state of the portion of the obtained patterned substrate from which the photosensitive layer was selectively removed was observed and evaluated with a microscope. When the surface state of the sample for evaluation was observed, a 15 × 15 μm square opening pattern was formed without residue, and this was defined as the resolution.

[Measurement of relative permittivity of photosensitive element]
A laminator (HLM-1500, manufactured by Hitachi Chemical Technoplant Co., Ltd.) is used so that the photosensitive layer is in contact with a p-type silicon wafer substrate having a thickness of 0.5 mm and a length of 4 cm × width of 4 cm. A laminate in which a photosensitive layer and a support film are laminated on a p-type silicon wafer substrate by laminating under conditions of a roll temperature of 110 ° C., a substrate feed rate of 0.5 m / min, and a pressure (cylinder pressure) of 0.3 MPa. Was made.

Next, a large-sized manual exposure machine (manufactured by Dainippon Screen Mfg. Co., Ltd., MAP 1200L) is used for the photosensitive layer of the obtained laminate, and the exposure amount is 100 mJ / cm ² from the upper side of the photosensitive layer (i-line (wavelength 365 nm )), After irradiation with ultraviolet rays, the support film was removed to obtain a sample for measuring the relative dielectric constant of a photosensitive layer (photocured cured film) having a thickness of 10 μm. The measurement result at a frequency of 1.0 KHz was a relative dielectric constant of 3.6.

(Examples 2-7, Comparative Example 1)
A photosensitive element was prepared in the same manner as in Example 1 using the photosensitive resin composition solution shown in Table 3 (the unit of the numerical values in the table is part by mass), and the total light, 400 nm transmittance measurement, resolution Measurements and relative permittivity measurements were performed, and the measurement results are summarized in Table 4.

（Ａ１）：メタクリル酸／メタクリル酸メチル／メタクリル酸ブチル＝３０／５５／１５（モル比）、酸価１６３．８（ｍｇＫＯＨ／ｇ）
（Ａ２）：メタクリル酸／メタクリル酸メチル／メタクリル酸ブチル＝３０／３５／３５（モル比）、酸価１５１．４（ｍｇＫＯＨ／ｇ）
（Ａ３）：メタクリル酸／メタクリル酸メチル／メタクリル酸ブチル＝３０／１５／５５（モル比）、酸価１４０．８（ｍｇＫＯＨ／ｇ）
（Ａ４）：メタクリル酸／メタクリル酸ブチル＝３０／７０（モル比）、酸価１３３．７（ｍｇＫＯＨ／ｇ）
（Ａ５）：メタクリル酸／メタクリル酸ブチル＝２５／７５（モル比）、酸価１０９．０（ｍｇＫＯＨ／ｇ）
（Ａ６）：メタクリル酸／メタクリル酸ブチル＝４０／６０（モル比）、酸価１８６．６（ｍｇＫＯＨ／ｇ）
（Ａ７）：メタクリル酸／メタクリル酸メチル＝３０／７０（モル比）、酸価１７４．５（ｍｇＫＯＨ／ｇ）
ＴＭＰ−Ａ：ペンタエリスリトールテトラアクリレート（共栄社化学株式会社製、酸価５ｍｇＫＯＨ／ｇ以下）
Ｉｒｇ−ＯＸＥ０１：１，２−オクタンジオン，１−［４−（フェニルチオ）−，２−（Ｏ−ベンゾイルオキシム）］（ＢＡＳＦ社）
ＡＯ−８０：３，９−ビス［１，１−ジメチル−２−［ベータ−（３−ｔ−ブチル−４−ヒドロキシ−５−メチルフィエニル）プロピオニルオキシ］エチル］２，４，８，１０−テトラオキサスピロ［５，５］−ウンデカン（株式会社ＡＤＥＫＡ）
ＫＢＭ−５０３：３−メタクリロキシプロピルトリエトキシシラン（信越化学工業株式会社）
ＰＧＭＥＡ：プロピレングリコール−１−メチルエーテルアセテート

(A1): Methacrylic acid / Methyl methacrylate / Butyl methacrylate = 30/55/15 (Molar ratio), Acid value 163.8 (mgKOH / g)
(A2): methacrylic acid / methyl methacrylate / butyl methacrylate = 30/35/35 (molar ratio), acid value 151.4 (mgKOH / g)
(A3): Methacrylic acid / Methyl methacrylate / Butyl methacrylate = 30/15/55 (Molar ratio), Acid value 140.8 (mgKOH / g)
(A4): Methacrylic acid / butyl methacrylate = 30/70 (molar ratio), acid value 133.7 (mgKOH / g)
(A5): Methacrylic acid / butyl methacrylate = 25/75 (molar ratio), acid value 109.0 (mgKOH / g)
(A6): Methacrylic acid / butyl methacrylate = 40/60 (molar ratio), acid value 186.6 (mgKOH / g)
(A7): Methacrylic acid / Methyl methacrylate = 30/70 (molar ratio), acid value 174.5 (mgKOH / g)
TMP-A: Pentaerythritol tetraacrylate (manufactured by Kyoeisha Chemical Co., Ltd., acid value of 5 mgKOH / g or less)
Irg-OXE01: 1,2-octanedione, 1- [4- (phenylthio)-, 2- (O-benzoyloxime)] (BASF)
AO-80: 3,9-bis [1,1-dimethyl-2- [beta- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy] ethyl] 2,4,8,10 -Tetraoxaspiro [5,5] -undecane (ADEKA Corporation)
KBM-503: 3-methacryloxypropyltriethoxysilane (Shin-Etsu Chemical Co., Ltd.)
PGMEA: Propylene glycol-1-methyl ether acetate

As shown in Table 4, in Examples 4 and 5, a low dielectric constant was realized as compared with a relative dielectric constant of 3.2 and a relative dielectric constant of 3.7 in Comparative Example 1. From a rate perspective, there is an advantage. Also, the transparency of Examples 4 and 5 was comparable to that of Comparative Example 1 and the same value was obtained. Further, in Examples 4 and 5, the resolution was 20 μm, and the developability was equivalent to the resolution of Comparative Example 1.
Comparative Example 1 using (A7) in which an alkyl group having 1 to 1 carbons was copolymerized with a (meth) acrylic acid alkyl ester having an alkyl group having 4 to 18 carbons used in the present invention has a light transmittance. Is excellent, but has a high relative dielectric constant. The present invention provides a copolymer containing (meth) acrylic acid and a (meth) acrylic acid alkyl ester having an alkyl group having 4 to 18 carbon atoms as a binder polymer, and a light having at least three ethylenically unsaturated groups. Providing a photosensitive transparent material for a protective film of a touch panel electrode having a light transmittance equivalent by using a polymerizable compound and having a relative dielectric constant reduced by 2.7 to 13.5% in the above-described embodiment. I can do it.
The polymerization molar ratio of the structural unit a1 and ((meth) acrylic acid) a2 ((meth) acrylic acid alkyl ester having an alkyl group having 4 to 18 carbon atoms) is in the range of a1 / a2 = 15/85 to 40/60. In certain Examples 3 to 6, the relative dielectric constant is further reduced.

Claims (4)

A photosensitive transparent material for a protective film of a touch panel electrode,
Without including β-hydroxyalkylamide represented by the following general formula (1),
(A) a structural unit a1 derived from (meth) acrylic acid and a structural unit a2 derived from a (meth) acrylic acid alkyl ester having an alkyl group having 4 to 18 carbon atoms, and the structural unit a1 a binder polymer polymerized in a range where the polymerization molar ratio of a2 is a1 / a2 = 15/85 to 40/60,
(B) a photopolymerizable compound having at least three ethylenically unsaturated groups and having an acid value of 5 mgKOH / g or less, and
(C) including a photopolymerization initiator,
The weight average molecular weight of the (A) binder polymer is 30,000 or more,
The photosensitive transparent material for a protective film of a touch panel electrode, wherein the (B) photopolymerizable compound contains a (meth) acrylate compound having a skeleton derived from pentaerythritol.

[In Formula (1), X is an n-valent group consisting of carbon, hydrogen, oxygen, nitrogen, sulfur or halogen, n is an integer of 2 to 6, and R ¹ and R ² are each independently A hydrogen atom, an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, a group represented by the following general formula (2), or a group represented by the following general formula (3): And at least one of one or more R ¹ and R ² bonded to one or more nitrogen atoms is a group represented by the following general formula (2). ]

[In Formula (2) and Formula (3), R ^{3 to} R ⁶ each independently represent a hydrogen atom, a hydrocarbon group, or a hydrocarbon group substituted with a hydroxyl group, and R ⁷ represents a hydroxyl group. Represents a residue of a compound having a functional group capable of reacting with. ]   The photosensitive transparent material for a protective film for a touch panel electrode according to claim 1, wherein the visible light transmittance is 90% or more when a film having a thickness of 10 μm is formed.   The photosensitive transparent material for a protective film for a touch panel electrode according to claim 1, wherein the dielectric constant when the cured film is formed is 3.1 to 3.8.   The photosensitive transparent material for a protective film of a touch panel electrode according to any one of claims 1 to 3, wherein the (C) photopolymerization initiator contains an oxime ester compound or a phosphine oxide compound.