JP2016194019A - Interlayer filler material for touch panel, and touch panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an interlayer filler material for a touch panel, which is used to fill the interlayer in the inside of a touch panel to be used for a portable information terminal or the like, with which an adhesive residue scarcely remains on a punching blade in punching, and air bubbles are scarcely produced in the interface between the interlayer filler material for a touch panel and the polarizing plate even when exposed to high temperature and high humidity in a state in which any foreign body with height of several tens of μm is interposed therebetween, and to provide a touch panel including the interlayer filler material for a touch panel.SOLUTION: An interlayer filler material for a touch panel is used for filling an interlayer in the inside of a touch panel and contains polyvinyl acetal, a plasticizer, and a tackifier.SELECTED DRAWING: None

Description

The present invention relates to an interlayer filling material for a touch panel used for filling an interlayer inside a touch panel used for a portable information terminal or the like, and particularly has a small adhesive residue with respect to a punching blade during punching and has a height of about several tens of μm. The present invention relates to an interlayer filling material for a touch panel that is less likely to generate bubbles at the interface between the interlayer filling material for a touch panel and a polarizing plate even when exposed to high temperature and high humidity with the foreign matter sandwiched therebetween. The present invention also relates to a touch panel including the interlayer filling material for a touch panel.

Touch panels are used in various fields, and are incorporated in portable information terminals such as smartphones and tablets. In a commonly used out-cell type touch panel, a film in which a touch panel wiring made of indium tin oxide (ITO) or the like is formed is disposed under a surface protection panel made of glass or the like. A polarizing plate and a display are sequentially provided under the attached film.
In order to improve the transparency, brightness, contrast, etc. of the display screen of the portable information terminal and improve the visibility, the interlayer between the surface protection panel and the film with the touch panel wiring and the interlayer between the film with the touch panel wiring and the polarizing plate are provided. The difference in refractive index between these members and the interlayer is reduced by filling with an interlayer filling material having a refractive index smaller than that of air.

As an interlayer filling material, an acrylic pressure-sensitive adhesive or pressure-sensitive adhesive tape is frequently used from the viewpoints of transparency, adhesiveness, coating property, and the like (for example, Patent Document 1).

In recent years, attention has been focused on a new touch panel configuration replacing the out-cell type in order to reduce the thickness and performance of the portable information terminal.
For example, a touch panel called a cover glass integrated type (so-called OGS: one glass solution), a cover sheet integrated type, or the like is a glass plate that is a surface protection panel, a resin film (for example, a polyester film), etc., and touch panel wiring. is there. A touch panel called an on-cell type, an in-cell type, or the like incorporates a touch panel function in a display by forming a touch panel wiring inside the display.
In these new touch panel configurations, an acrylic pressure-sensitive adhesive or pressure-sensitive adhesive tape as described in Patent Document 1 is used to bond the polarizing plates together.

However, the acrylic pressure-sensitive adhesive or pressure-sensitive adhesive tape described in Patent Document 1 is washed with a punching blade because the acrylic pressure-sensitive adhesive adheres to the punching blade in the process of punching into the shape of the touch panel (glue residue). There was a problem that it took a long time.

In addition, the acrylic pressure-sensitive adhesive or pressure-sensitive adhesive tape described in Patent Document 1 is an interface between the acrylic pressure-sensitive adhesive and the polarizing plate when the adherend and the polarizing plate are laminated via the acrylic pressure-sensitive adhesive. If a foreign substance having a height of about several tens of μm is contained in the liquid crystal, there is a problem that bubbles are generated mainly at the foreign substance under high temperature and high humidity. There has been a demand for an interlayer filling material that does not generate bubbles even if there is a foreign matter having a height of about several tens of μm.

JP 2011-74308 A

The present invention is used to fill an interlayer inside a touch panel used for a portable information terminal or the like, and has a small adhesive residue with respect to a punching blade at the time of punching, with a foreign object having a height of about several tens of μm sandwiched between them. An object of the present invention is to provide an interlayer filling material for a touch panel that is less likely to generate bubbles at the interface between the interlayer filling material for a touch panel and a polarizing plate even when exposed to high temperature and high humidity. Another object of the present invention is to provide a touch panel including the interlayer filling material for a touch panel.

The present invention is an interlayer filling material for a touch panel used for filling an interlayer in a touch panel, and is an interlayer filling material for a touch panel containing polyvinyl acetal, a plasticizer, and a tackifier.
The present invention is described in detail below.

The present inventor uses polyvinyl acetal, a plasticizer, and a tackifier as a material to replace an acrylic adhesive that has been widely used in an interlayer filling material for a touch panel used for filling an interlayer inside a touch panel. The present invention has been found by suppressing the adhesive residue and effective in suppressing the generation of bubbles centered on foreign matter under high temperature and high humidity even when there is a foreign matter having a height of about several tens of μm. It came to.

The interlayer filling material for a touch panel of the present invention is used for filling the interlayer inside the touch panel.

The interlayer filling material for a touch panel of the present invention contains polyvinyl acetal and a plasticizer.

The polyvinyl acetal can be prepared, for example, by acetalizing polyvinyl alcohol obtained by saponifying polyvinyl acetate with an aldehyde in the presence of a catalyst. The saponification degree of the polyvinyl alcohol is not particularly limited, but is generally in the range of 70 to 99.9 mol%, preferably 70 to 99.8 mol%, more preferably 80 to 99.8 mol%.

When the polyvinyl alcohol is acetalized with an aldehyde in the presence of a catalyst, a solution containing the polyvinyl alcohol may be used. As a solvent used for the solution containing the said polyvinyl alcohol, water etc. are mentioned, for example.

Although the said aldehyde is not specifically limited, Generally, a C1-C10 aldehyde is used suitably.
The aldehyde having 1 to 10 carbon atoms is not particularly limited, and may be a linear aldehyde or a branched aldehyde such as n-butyraldehyde, isobutyraldehyde, n- Examples include valeraldehyde, 2-ethylbutyraldehyde, n-hexylaldehyde, n-octylaldehyde, n-nonylaldehyde, n-decylaldehyde, formaldehyde, acetaldehyde, benzaldehyde and the like. Of these, n-butyraldehyde, n-hexylaldehyde, and n-valeraldehyde are preferable, and n-butyraldehyde is more preferable. These aldehydes may be used alone or in combination of two or more.
That is, the polyvinyl acetal is preferably polyvinyl butyral (when the aldehyde is n-butyraldehyde, the polyvinyl acetal is referred to as polyvinyl butyral). By using the polyvinyl butyral, the adhesive force of the interlayer filling material for touch panel to glass is appropriately developed, and light resistance, weather resistance, and the like are improved. Moreover, you may use together 2 or more types of polyvinyl acetal as needed.

The average degree of polymerization of the polyvinyl acetal is not particularly limited, but the average degree of polymerization is high because polyvinyl acetal having a large molecular weight is preferable from the viewpoint of further suppressing the generation of bubbles centering on foreign matters under high temperature and high humidity. It is preferable.
The preferable lower limit of the average degree of polymerization of the polyvinyl acetal is 300, and the preferable upper limit is 4000. When the average degree of polymerization is less than 300, the mechanical strength of the polyvinyl acetal may be reduced, and the cohesive force of the polyvinyl acetal may be reduced to reduce bubbles of mainly foreign substances under high temperature and high humidity. Occurrence may not be suppressed. When the average polymerization degree exceeds 4000, when the polyvinyl alcohol is acetalized, the solution viscosity becomes abnormally high, and acetalization may be difficult, and it becomes difficult to mold an interlayer filling material for a touch panel. Sometimes. The more preferable lower limit of the average degree of polymerization is 350, the more preferable upper limit is 3800, the still more preferable lower limit is 800, and the still more preferable upper limit is 3500.
The average degree of polymerization of polyvinyl acetal can be considered to correspond to the average degree of polymerization of polyvinyl alcohol as a raw material.

The polyvinyl acetal has less intermolecular cross-linking because it is excellent in the ability to follow steps and foreign matter caught in the adherend and can suppress the generation of bubbles centering on foreign matter under high temperature and high humidity. Is preferred. If the intermolecular crosslinking of the polyvinyl acetal is small, it is possible to obtain an interlayer filling material for a touch panel that is more excellent in step following ability even if the molecular weight, acetyl group amount, degree of acetalization, etc. of the polyvinyl acetal are the same. Furthermore, if the molecular weight of the polyvinyl acetal is large, the generation of bubbles centering on foreign matters under high temperature and high humidity can be further suppressed.
As a method for obtaining such a polyvinyl acetal with little intermolecular crosslinking, for example, so as not to crosslink the main chain of the adjacent polyvinyl alcohol, so as not to excessively add the aldehyde before or during the acetalization reaction with the aldehyde. Is preferred. When the aldehyde is added in excess of the amount required for acetalization, the degree of crosslinking increases.

The preferable lower limit of the hydroxyl group content (hydroxyl group amount) of the polyvinyl acetal is 16 mol%, and the preferable upper limit is 45 mol%. When the amount of the hydroxyl group is 16 mol% or more, the adhesive force of the interlayer filling material for touch panel to glass is improved. If the amount of the hydroxyl group is 45 mol% or less, the flexibility of the polyvinyl acetal is increased, the handleability is improved, and the compatibility between the polyvinyl acetal and the plasticizer is increased, and the interlayer filling material for a touch panel is obtained. The step following ability is improved, and generation of bubbles centering on foreign matters under high temperature and high humidity can be further suppressed. The more preferred lower limit of the hydroxyl group content is 18 mol%, the still more preferred lower limit is 20 mol%, the particularly preferred lower limit is 22 mol%, the more preferred upper limit is 40 mol%, the still more preferred upper limit is 38 mol%, and the still more preferred upper limit. Is 36 mol%, and a particularly preferred upper limit is 35 mol%.
In addition, the hydroxyl group amount of polyvinyl acetal is the value which expressed the mole fraction calculated | required by dividing the ethylene group amount which the hydroxyl group has couple | bonded with the total ethylene group amount of a principal chain in percentage (mol%). The amount of ethylene group to which the hydroxyl group is bonded can be determined, for example, by a method based on JIS K6728 “Testing method for polyvinyl butyral”.

The preferable lower limit of the degree of acetylation (acetyl group amount) of the polyvinyl acetal is 0.1 mol%, and the preferable upper limit is 30 mol%. If the amount of the acetyl group is 0.1 mol% or more, the compatibility between the polyvinyl acetal and the plasticizer is increased, the step following property of the interlayer filling material for touch panel is improved, and foreign matter under high temperature and high humidity. The generation of bubbles centering on can be further suppressed. When the amount of the acetyl group is 30 mol% or less, the moisture resistance of the polyvinyl acetal is improved. Moreover, when the said acetyl group amount exceeds 30 mol%, the reaction efficiency at the time of manufacturing the said polyvinyl acetal may fall. The more preferable lower limit of the amount of the acetyl group is 0.2 mol%, the still more preferable lower limit is 0.3 mol%, the more preferable upper limit is 24 mol%, the still more preferable upper limit is 20 mol%, and the still more preferable upper limit is 19. 5 mol%, and a particularly preferred upper limit is 15 mol%.
The amount of acetyl groups in polyvinyl acetal is the value obtained by subtracting the amount of ethylene groups to which acetal groups are bonded and the amount of ethylene groups to which hydroxyl groups are bonded from the total amount of ethylene groups in the main chain. This is a value expressed as a percentage (mol%) of the mole fraction obtained by dividing by the total amount of ethylene groups. The amount of ethylene group to which the acetal group is bonded can be measured, for example, according to JIS K6728 “Testing method for polyvinyl butyral”.

Examples of a method for adjusting the amount of acetyl groups of the polyvinyl acetal within the above range include a method for adjusting the degree of saponification of the polyvinyl alcohol. That is, the amount of acetyl groups in the polyvinyl acetal depends on the degree of saponification of the polyvinyl alcohol. If polyvinyl alcohol having a low saponification degree is used, the amount of acetyl groups in the polyvinyl acetal increases and the degree of saponification is high. The amount of acetyl groups in the polyvinyl acetal is reduced.

The preferable lower limit of the degree of acetalization of the polyvinyl acetal is 50 mol%, and the preferable upper limit is 85 mol%. If the said acetalization degree is 50 mol% or more, the compatibility of the said polyvinyl acetal and the said plasticizer will become high. If the said acetalization degree is 85 mol% or less, reaction time required in order to manufacture the said polyvinyl acetal can be shortened. The more preferable lower limit of the degree of acetalization is 54 mol%, the still more preferable lower limit is 58 mol%, and the particularly preferable lower limit is 60 mol%. A more preferable upper limit of the degree of acetalization is 82 mol%, a further preferable upper limit is 79 mol%, and a particularly preferable upper limit is 77 mol%.
The degree of acetalization of polyvinyl acetal is a value obtained by dividing the amount of ethylene groups to which the acetal group is bonded by the total amount of ethylene groups in the main chain, as a percentage (mol%). . The degree of acetalization is determined by measuring the amount of acetyl groups and the amount of vinyl alcohol (hydroxyl content) by a method based on JIS K6728 “Testing methods for polyvinyl butyral”, and calculating the molar fraction from the obtained measurement results. Subsequently, it can be calculated by subtracting the amount of acetyl groups and the amount of vinyl alcohol from 100 mol%.

Examples of a method for adjusting the degree of acetalization of the polyvinyl acetal include a method for adjusting the amount of the aldehyde added. If the addition amount of the aldehyde is decreased, the degree of acetalization of the polyvinyl acetal is lowered, and if the addition amount of the aldehyde is increased, the degree of acetalization of the polyvinyl acetal is increased.

The said plasticizer is not specifically limited, A conventionally well-known plasticizer can be used, may be used independently and may use 2 or more types together. Examples of the plasticizer include organic acid ester plasticizers such as monobasic organic acid esters and polybasic organic acid esters, and phosphoric acid plasticizers such as organic phosphoric acid plasticizers and organic phosphorous acid plasticizers. . Of these, organic acid ester plasticizers are preferred.
The plasticizer is preferably a liquid plasticizer.

The monobasic organic acid ester is not particularly limited. For example, butyric acid, isobutyric acid, caproic acid, 2-ethylbutyric acid, heptylic acid, n-octylic acid, 2-ethylhexylic acid, pelargonic acid (n-nonylic acid), Examples thereof include glycol esters obtained by reacting monobasic organic acids such as decyl acid with glycols such as triethylene glycol, tetraethylene glycol and tripropylene glycol.
The polybasic organic acid ester is not particularly limited. For example, by reacting a polybasic organic acid such as adipic acid, sebacic acid, or azelaic acid with an alcohol having a linear or branched structure having 4 to 8 carbon atoms. The obtained ester compound etc. are mentioned.

The organic acid ester plasticizer is preferably a diester plasticizer represented by the following formula. By using the diester plasticizer, the moldability of the interlayer filling material for touch panels is improved.
R ¹ —CO — (— R ³ —O—) _p —CO—R ²
In the formula, R ¹ and R ² each represent an organic group having 5 to 10 carbon atoms (preferably 6 to 10 carbon atoms), R ³ represents an ethylene group, an isopropylene group or an n-propylene group, and p is 3 Represents an integer of -10.
Specific examples of the organic acid ester plasticizer include triethylene glycol-di-2-ethylbutyrate, triethylene glycol-di-2-ethylhexanoate, triethylene glycol dicaprylate, and triethylene glycol diethylene. -N-octanoate, triethylene glycol-di-n-heptanoate, tetraethylene glycol-di-n-heptanoate, tetraethylene glycol-di-2-ethylhexanoate, dibutyl sebacate, dioctyl azelate, dibutyl carbitol adipate , Ethylene glycol di-2-ethyl butyrate, 1,3-propylene glycol di-2-ethyl butyrate, 1,4-butylene glycol di-2-ethyl butyrate, diethylene glycol-di-2-ethyl butyrate, diethyl Glycol-di-2-ethylhexanoate, dipropylene glycol di-2-ethylbutyrate, triethylene glycol di-2-ethylpentanoate, tetraethylene glycol-di-2-ethylbutyrate, diethylene glycol dicapri Ate, dihexyl adipate, dioctyl adipate, hexyl cyclohexyl adipate, diisononyl adipate, heptylnonyl adipate, oil-modified sebacic acid alkyd, a mixture of phosphate ester and adipate ester, alkyl alcohol having 4 to 9 carbon atoms and 4 to 9 carbon atoms And mixed adipic acid esters prepared from cyclic alcohols.

The organophosphate plasticizer is not particularly limited, and examples thereof include tributoxyethyl phosphate, isodecylphenyl phosphate, triisopropyl phosphate, and the like.

Among the plasticizers, dihexyl adipate (DHA), triethylene glycol-di-2-ethylhexanoate (3GO), tetraethylene glycol-di-2-ethylhexanoate (4GO), triethylene glycol-di 2-ethylbutyrate (3GH), tetraethylene glycol-di-2-ethylbutyrate (4GH), tetraethylene glycol-di-n-heptanoate (4G7) and triethylene glycol-di-n-heptanoate (3G7) At least one selected from the group consisting of triethylene glycol-di-2-ethylbutyrate, triethylene glycol-di-n-heptanoate (3G7), triethylene glycol-di-2-ethylhexanoate (3GO) is more preferred. Glycol - di-2-ethylhexanoate is more preferred.

Although the content of the plasticizer with respect to the polyvinyl acetal is not particularly limited, a preferable lower limit with respect to 100 parts by weight of the polyvinyl acetal is 5 parts by weight, and a preferable upper limit is 75 parts by weight. If the content is within the above range, it is effective to suppress the adhesive residue and suppress the generation of bubbles centered on the foreign matter under high temperature and high humidity even if there is a foreign matter having a height of about several tens of μm. .
If the content is less than 5 parts by weight, the moldability of the interlayer filling material for a touch panel may be lowered. When the content exceeds 75 parts by weight, the transparency of the interlayer filling material for a touch panel may decrease, or the plasticizer may bleed out. The more preferred lower limit of the plasticizer is 10 parts by weight, the still more preferred lower limit is 15 parts by weight, the particularly preferred lower limit is 20 parts by weight, the more preferred upper limit is 65 parts by weight, the still more preferred upper limit is 55 parts by weight, and the particularly preferred upper limit is 45 parts by weight.

As a method for increasing the compatibility between the polyvinyl acetal and the plasticizer, for example, a method for increasing the degree of acetalization of the polyvinyl acetal and a method for increasing the amount of acetyl groups are preferable. Also preferred is a method of removing the blocking property of the hydroxyl group of the polyvinyl acetal. As a method of suppressing the blocking of the hydroxyl group, a method of lowering the aging temperature is preferable.

In the interlayer filling material for a touch panel of the present invention, the combined content of the polyvinyl acetal and the plasticizer is preferably 50% by weight or more. When the content is less than 50% by weight, adhesive residue may increase with respect to the punching blade during punching, or bubbles may be generated mainly with foreign matters under high temperature and high humidity. The more preferable lower limit of the content is 60% by weight, the still more preferable lower limit is 70% by weight, the still more preferable lower limit is 80% by weight, and the particularly preferable lower limit is 90% by weight.
The upper limit of the combined content of the polyvinyl acetal and the plasticizer is not particularly limited, but if the content of the tackifier is too low, bubbles centered on foreign matters are likely to be generated under high temperature and high humidity. The preferred upper limit is 70% by weight, and the more preferred upper limit is 60% by weight.

The interlayer filling material for a touch panel of the present invention contains a tack fire.
The tackifier is not particularly limited as long as the transparency of the interlayer filling material for the touch panel is not impaired, but preferably includes a resin generally called an oligomer having a weight average molecular weight of several hundred to several thousand.
As the tackifier, for example, a styrene polymer or copolymer obtained by polymerizing or copolymerizing a styrene monomer such as styrene or α-methylstyrene and an aliphatic monomer such as terpene as necessary. Copolymer; Coumarone-indene resin; phenolic resin such as t-butylphenol resin, phenol formaldehyde resin, xylene-phenol resin; xylene resin; terpene phenol resin, terpene resin (α-pinene, β-pinene, dipentene) ), Terpene resins such as aromatic modified terpene resins and hydrogenated terpene resins; aromatic (C9) petroleum resins, aliphatic (C5) petroleum resins, copolymerized (C5 / C9) petroleum resins , Petroleum hydrocarbon trees such as alicyclic petroleum resins (alicyclic saturated hydrocarbon resins), hydrogenated petroleum resins, etc. Rosin, rosin pentaerythritol ester, rosin glycerol ester, hydrogenated rosin, disproportionated rosin, polymerized rosin, rosin-based resin such as hydrogenated rosin pentaerythritol ester; other preparations However, it is not limited to them. The above tackifiers may be used alone or in combination of two or more. Among these, terpene phenol resins, aromatic modified terpene resins, alicyclic saturated hydrocarbon resins, rosin resins, styrene polymers or copolymers are preferable.

The interlayer filling material for a touch panel of the present invention includes an adherend and a polarizing plate through an interlayer filling material for a touch panel, particularly when the tackifier contains a resin generally called an oligomer having a weight average molecular weight of several hundred to several thousands. When the layers are heated to about 70 to 80 ° C., high followability can be exhibited even with a foreign object having a height of about several tens of μm. Fine voids that become the core of bubbles generated under high temperature and high humidity are less likely to occur.
Furthermore, the interlayer filling material for a touch panel of the present invention contains a polyvinyl acetal having a high cohesive force, so that the growth of bubbles under high temperature and high humidity can be suppressed, and a foreign matter having a height of about several tens of μm. Even if there is, the generation of bubbles under high temperature and high humidity can be suppressed.

In the interlayer filling material for a touch panel of the present invention, the content of the tackifier is preferably 0.1% by weight or more and 50% by weight or less. When the content is less than 0.1% by weight, air bubbles centered on foreign matters may be easily generated under high temperature and high humidity. When the content exceeds 50% by weight, the combined content of the polyvinyl acetal and the plasticizer is too low, and the adhesive residue increases with respect to the punching blade during the punching process. It may become easy to generate air bubbles centering around. A more preferable lower limit of the content is 0.5% by weight, and a more preferable lower limit is 5% by weight. A more preferable upper limit of the content is 30% by weight, and a more preferable upper limit is 20% by weight.

The interlayer filling material for a touch panel of the present invention, if necessary, within a range that does not impair transparency, an adhesive strength modifier, a tackifier resin, a plasticizer, an emulsifier, a softener, fine particles, a filler, a pigment, a dye, You may contain well-known additives, such as a silane coupling agent, antioxidant, surfactant, and wax.

The shape of the interlayer filling material for a touch panel of the present invention is not particularly limited, and examples thereof include a sheet shape, a film shape, and a liquid (dispersed liquid, emulsion), and the like is preferable. Even if the interlayer filling material for touch panel of the present invention is a thin filling material, when the adherend and the polarizing plate are laminated via the interlayer filling material for touch panel, the sandwiched height is about several tens of μm. High followability can be expressed even with respect to foreign matter.
In the case of a sheet form, the thickness of the interlayer filling material for a touch panel of the present invention is not particularly limited and is set depending on the application, but a preferable lower limit is 5 μm and a preferable upper limit is 800 μm. If the thickness is less than 5 μm, the step following property of the interlayer filling material for the touch panel may be lowered, and generation of bubbles centering on foreign matters at high temperature and high humidity may not be suppressed. The more preferred lower limit of the thickness is 10 μm, the more preferred upper limit is 400 μm, the still more preferred lower limit is 25 μm, the still more preferred upper limit is 300 μm, the still more preferred lower limit is 50 μm, the still more preferred upper limit is 200 μm, and the particularly preferred lower limit. Is 75 μm, and a particularly preferred upper limit is 100 μm.

The method for producing an interlayer filling material for a touch panel of the present invention is not particularly limited. In the case of a sheet, for example, a composition containing polyvinyl acetal, a plasticizer, a tackifier, and an additive blended as necessary is extruded. Examples thereof include a method of forming a film into a sheet by a usual film forming method such as a method, a method of construction, a casting method, a calendar method, or a press method.

The use of the interlayer filling material for a touch panel of the present invention is not particularly limited. For example, a flat or flexible image display device using an image display panel such as a portable information terminal (for example, a smartphone or a tablet), LCD, EL, or PDP ( For example, in electronic paper, PDA, TV, game machine, etc., it is used to fill the interlayer inside the touch panel.
When the interlayer filling material for touch panel of the present invention is sandwiched between layers and heated to around 70 to 85 ° C., the interlayer can be filled easily. Further, for example, after preheating and pressing at 70 ° C. for 30 minutes at 1 atm with a vacuum laminator, autoclave (ACV) treatment in which pressurization is performed simultaneously with heating is performed for 30 minutes at a temperature of 70 ° C., thereby being sandwiched. Higher followability can be expressed even for foreign matters having a height of about several tens of μm. Further, using a vacuum laminator, the interlayer may be filled by thermocompression bonding at, for example, 70 ° C. for 30 minutes at 5 atm. Moreover, after pressing and pressing with an indenter in vacuum, the layers may be filled by performing thermocompression bonding at 70 ° C. for 30 minutes at 1 atm, for example.

The configuration of the touch panel is not particularly limited, and examples thereof include an out-cell type, a cover glass integrated type (so-called OGS: one glass solution), a cover sheet integrated type, an on-cell type, and an in-cell type. The method of the touch panel is not particularly limited, and is usually used for, for example, a portable information terminal, a flat type or a flexible image display device such as a resistance film type, a capacitance type, an optical type, an ultrasonic type, and an acoustic wave matching type. Can be used.

In the out-cell type touch panel, a film having a touch panel wiring made of indium tin oxide (ITO) or the like is disposed under the surface protection panel, and a polarizing plate and a display are disposed under the film with the touch panel wiring. Are provided in order. The said surface protection panel is not specifically limited, For example, what is normally used for portable information terminals, a flat type, or a flexible image display apparatus, such as a glass plate and a resin board (for example, a polycarbonate board, an acrylic board), is used. Can do.
In the out-cell type touch panel, the interlayer filling material for a touch panel of the present invention is used, for example, for laminating the film with a touch panel wiring and the polarizing plate (filling the interlayer).
FIG. 1 is a cross-sectional view schematically showing an example of a method of using the interlayer filling material for a touch panel of the present invention. FIG. 1 shows an out-cell type touch panel in which a film 2 with a touch panel wiring and a polarizing plate 4 are sequentially provided under a surface protective panel 3 (having a decorative printing unit 5). In FIG. 1, the interlayer between the film 2 with touch panel wiring and the polarizing plate 4 is filled with an interlayer filling material 1 for a touch panel. The film 2 with a touch panel wiring may be a multilayer film. In addition, as shown in FIG. 1, the interlayer of the surface protection panel 3 and the film 2 with a touch panel wiring may be filled with the interlayer filling material 1 for a touch panel.

The above-mentioned cover glass integrated type (so-called OGS: one glass solution) or cover sheet integrated type touch panel is obtained by applying touch panel wiring to a glass plate, a resin film (for example, a polyester film) which is a surface protection panel, A polarizing plate and a display are sequentially provided under such a glass plate with touch panel wiring, a resin film with touch panel wiring, and the like.
On the touch panel wiring such as the glass plate with touch panel wiring and the resin film with touch panel wiring, a hard coat layer made of, for example, urethane acrylate may be further formed.
In the above-described cover glass-integrated type or cover sheet-integrated type touch panel, the interlayer filling material for a touch panel of the present invention includes, for example, a laminate of the above-mentioned glass plate with a touch panel wiring, a resin film with a touch panel wiring, etc. Used to fill).

The on-cell type or in-cell type touch panel has a touch panel function built into the display by forming a touch panel wiring inside the display. A display with a polarizing plate and a touch panel function built under the surface protection panel is provided. It is provided in order. The said surface protection panel is not specifically limited, For example, what is normally used for portable information terminals, a flat type, or a flexible image display apparatus, such as a glass plate and a resin board (for example, a polycarbonate board, an acrylic board), is used. Can do.
In the on-cell type or in-cell type touch panel, the interlayer filling material for a touch panel of the present invention is used, for example, for laminating (filling the interlayer) the surface protection panel and the polarizing plate.

At least one type of adherend selected from the group consisting of a glass plate, a resin plate, a resin film, a glass plate with a touch panel wiring, and a resin film with a touch panel wiring, and the polarizing plate, the interlayer filling material for a touch panel of the present invention. A touch panel laminated via the touch panel is also one aspect of the present invention.

According to the present invention, it is used to fill an interlayer inside a touch panel used for a portable information terminal or the like, and there is little adhesive residue with respect to the punching blade during punching, and foreign matter having a height of about several tens of μm is sandwiched. Even when exposed to high temperature and high humidity in a state, it is possible to provide an interlayer filling material for a touch panel in which bubbles are not easily generated at the interface between the interlayer filling material for a touch panel and a polarizing plate. Moreover, according to this invention, the touch panel containing the said interlayer filler material for touch panels can be provided.

It is sectional drawing which shows typically an example of the usage method of the interlayer filling material for touchscreens of this invention.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

(Examples 1 to 28)
(1) Production of polyvinyl butyral resin (1) A reactor equipped with a stirrer is charged with 2700 mL of ion-exchanged water, 300 g of polyvinyl alcohol having an average polymerization degree of 1800 and a saponification degree of 99.3 mol%, and heated and dissolved while stirring. To obtain a solution. Next, 35% by weight hydrochloric acid as a catalyst was added to this solution so that the hydrochloric acid concentration was 0.2% by weight, the temperature was adjusted to 15 ° C., and n-butyraldehyde (n-BA) was stirred. 21 g was added. Thereafter, when 145 g of n-butyraldehyde (n-BA) was added, white particulate polyvinyl butyral resin was precipitated. 15 minutes after the precipitation, 35 wt% hydrochloric acid was added so that the hydrochloric acid concentration was 1.8 wt%, heated to 50 ° C., and aged at 50 ° C. for 2 hours. Then, after cooling and neutralizing the solution, the polyvinyl butyral resin was washed with water and dried to obtain a polyvinyl butyral resin (1). The amount of hydroxyl groups was 31.0 mol%, the amount of acetyl groups was 0.7 mol%, and the degree of butyralization (degree of Bu formation) was 68.3 mol%.

(2) Production of polyvinyl butyral resins (2) to (7) Based on the formulation and conditions shown in Table 1, polyvinyl butyral resins (2) to (7) were produced in the same manner as the polyvinyl butyral resin (1).

(3) Manufacture of sheet-like interlayer filling material Using the obtained polyvinyl butyral resins (1) to (7), the following film formation was carried out by blending the sheet-like interlayer filling material shown in Table 2.
Triethylene glycol-di-2-ethylhexa as a plasticizer with respect to 100 parts by weight of the obtained polyvinyl butyral resin (having the degree of butyralization (Bu degree), the amount of hydroxyl group and the amount of acetyl group shown in Table 1) Noate (3GO) and tackifier were added at the blending amounts shown in Table 2 and kneaded thoroughly to obtain a kneaded product. The obtained kneaded material was press-molded by a press molding machine to form a sheet, and a sheet-like interlayer filling material having a film thickness shown in Table 2 was obtained.

<Evaluation 1>
The following evaluation was performed about the sheet-like interlayer filling material obtained in the Example. The results are shown in Table 2.

(1) 5 mg of resinous spherical particles (Micropearl manufactured by Sekisui Chemical Co., Ltd.) having a foamed average particle diameter of 40 μm under high temperature and high humidity are collected with a spatula, and a white plate glass (Matsunami Glass with a thickness of 1.0 to 1.2 mm) Dropping from a height of 30 cm onto S9112) was repeated three times. After pasting the sheet-like interlayer filling material on the white plate glass, a separately prepared white plate glass (S9112 manufactured by Matsunami Glass Co., Ltd.) having a thickness of 1.0 to 1.2 mm was stuck on the sheet-like interlayer filling material. . Next, this structure was preliminarily heat-pressed with a vacuum laminator at 70 ° C. and 1 atm for 30 minutes, and then heated in an autoclave at 75 ° C. and 0.5 MPa for 30 minutes. A laminated body in which spherical white particles having an average particle diameter of 40 μm were encapsulated and 2 sheets of white sheet glass were filled with a sheet-like interlayer filling material was obtained.
Furthermore, the laminated body was put into an environment of 85 ° C. and 85%, and the laminated body after 5 hours was observed using a microscope. Out of 100 randomly selected spherical particles, the number of the spherical particles in which bubbles are generated centering on the spherical particles is 0, and 1-10 are “◯”, 11-20 The thing of the piece was set as "△", and the thing of 21 or more was set as "x".

(2) Adhesive residue When the sheet-like interlayer filling material was punched 50 times with a 50 mm × 50 mm Thomson blade, the presence or absence of adhesion (glue residue) of the sheet-like interlayer filling material to the Thomson blade was visually confirmed. The case where no adhesive residue was generated on the Thomson blade was indicated as “◯”, and the case where adhesive residue was generated was indicated as “x”.

(Comparative Example 1)
(1) Preparation of acrylic copolymer (resin (8))
In a reaction vessel equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen gas inlet, 65.0 parts by weight of n-butyl acrylate, 26.0 parts by weight of methyl methacrylate, 4.0 parts by weight of ethyl acrylate, hydroxyethyl acrylate 1 0.04 parts by weight, 4.0 parts by weight of acrylic acid and 0.2 parts by weight of 2,2′-azobisisobutylnitrile as a polymerization initiator were dissolved in 100 parts by weight of ethyl acetate. Acrylic copolymer was obtained by time polymerization.
A diluted sample obtained by diluting the obtained acrylic copolymer 50 times with tetrahydrofuran (THF) was filtered through a filter (material: polytetrafluoroethylene, pore diameter: 0.2 μm) to prepare a measurement sample. This measurement sample is supplied to a gel permeation chromatograph (manufactured by Waters, 2690 Separations Model), GPC measurement is performed under the conditions of a sample flow rate of 1 ml / min and a column temperature of 40 ° C., and the polystyrene equivalent molecular weight of the acrylic copolymer is measured. Was measured to determine the weight average molecular weight (Mw).
The weight average molecular weight of the obtained acrylic copolymer was 650,000.
GPC LF-804 (manufactured by Showa Denko) was used as the column, and a differential refractometer was used as the detector.

(2) Preparation of pressure-sensitive adhesive sheet 100 parts by weight of the acrylic copolymer was diluted with ethyl acetate to obtain a pressure-sensitive adhesive solution having a resin solid content of 45%. To 100 parts by weight of the acrylic copolymer in the pressure-sensitive adhesive solution, 1.0 part by weight of an isocyanate-based cross-linking agent (Nippon Polyurethane Coronate L-45, solid content 45%) was added and stirred for 15 minutes. The 50 μm release PET film was coated on the release treated surface so that the thickness after drying was 200 μm, and dried at 80 ° C. for 15 minutes. Furthermore, a newly prepared release PET film was superposed on the obtained pressure-sensitive adhesive layer so that the release treatment surface was in contact with the pressure-sensitive adhesive layer to obtain a laminate. Thereafter, the laminate was cured at 23 ° C. for 5 days to obtain an adhesive sheet (thickness: 200 μm) having a release PET film attached to both sides.

(Comparative Examples 2 to 4)
In the same manner as in Comparative Example 1, an acrylic copolymer was produced with the formulation shown in Table 3. The composition and weight average molecular weight are shown in Table 3. Moreover, the adhesive sheet was produced similarly to the comparative example 1, respectively.

(Comparative Example 5)
100 parts by weight of the acrylic copolymer and 10 parts by weight of tackifier (1) were diluted with ethyl acetate to obtain a pressure-sensitive adhesive solution having a resin solid content of 45%. To 100 parts by weight of the acrylic copolymer in the pressure-sensitive adhesive solution, 1.5 parts by weight of an isocyanate-based cross-linking agent (Coronate L-45 manufactured by Nippon Polyurethane Co., Ltd., 45% solid content) was added and stirred for 15 minutes. The 50 μm release PET film was coated on the release treated surface so that the thickness after drying was 200 μm, and dried at 80 ° C. for 15 minutes. Furthermore, a newly prepared release PET film was superposed on the obtained pressure-sensitive adhesive layer so that the release treatment surface was in contact with the pressure-sensitive adhesive layer to obtain a laminate. Thereafter, the laminate was cured at 23 ° C. for 5 days to obtain an adhesive sheet (thickness: 200 μm) having a release PET film attached to both sides.

(Comparative Examples 6-11)
In the same manner as in Comparative Example 5, an acrylic copolymer was produced with the formulation shown in Table 3. The composition and weight average molecular weight are shown in Table 3. Moreover, the adhesive sheet was produced similarly to the comparative example 1, respectively.

<Evaluation 2>
About the adhesive sheet obtained by the comparative example, evaluation similar to said <evaluation 1> was performed. The results are shown in Table 4.

According to the present invention, it is used to fill an interlayer inside a touch panel used for a portable information terminal or the like, and there is little adhesive residue with respect to the punching blade during punching, and foreign matter having a height of about several tens of μm is sandwiched. Even when exposed to high temperature and high humidity in a state, it is possible to provide an interlayer filling material for a touch panel in which bubbles are not easily generated at the interface between the interlayer filling material for a touch panel and a polarizing plate. Moreover, according to this invention, the touch panel containing the said interlayer filler material for touch panels can be provided.

DESCRIPTION OF SYMBOLS 1 Interlayer filling material for touch panels 2 Film with touch panel wiring 3 Surface protection panel 4 Polarizing plate 5 Decorative printing part

Claims (7)

An interlayer filling material for a touch panel, which is used for filling an interlayer in a touch panel, comprising polyvinyl acetal, a plasticizer, and a tack fire. The interlayer filling material for a touch panel according to claim 1, wherein the total content of the polyvinyl acetal and the plasticizer is 50% by weight or more. 3. The interlayer filling material for a touch panel according to 1 or 2, wherein the content of the tackifier is 0.1% by weight or more and 50% by weight or less. The tackifier is a terpene phenol resin, an aromatic modified terpene resin, an alicyclic saturated hydrocarbon resin, a rosin resin, or a styrene polymer or copolymer. Interlayer filling material for touch panels. 5. The interlayer filling material for a touch panel according to claim 1, wherein the polyvinyl acetal is polyvinyl butyral. The interlayer filling material for a touch panel according to claim 1, 2, 3, 4, or 5, wherein the polyvinyl acetal has an average degree of polymerization of 800 to 3,500. Claims 1, 2, 3, 4 wherein at least one adherend selected from the group consisting of a glass plate, a resin plate, a resin film, a glass plate with a touch panel wiring, and a resin film with a touch panel wiring, and a polarizing plate. A touch panel, which is laminated through the interlayer filling material for a touch panel according to 5 or 6.

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