KR102061117B1 - Clear adhesives for touch panel - Google Patents

Abstract

A transparent adhesive for touch panels is disclosed.
The transparent pressure-sensitive adhesive according to the present invention includes a (meth) acrylate oligomer, a mixed monomer, a plasticizer and a photoinitiator containing an alkylene oxide in a polyether polyol, wherein the mixed monomer is a monomer having a hydroxy group, a monomer having a carboxyl group, nitrogen It is characterized by including one or more of the monomers having a functional group containing.

Description

Transparent adhesive for touch panel {CLEAR ADHESIVES FOR TOUCH PANEL}

The present invention relates to a transparent adhesive, and more particularly, to a transparent adhesive having a high dielectric constant.

A touch screen panel (TSP), which is an optical display element, is formed on the side of a flat panel display (FPD) or a cathode ray tube (CRT) such as a liquid crystal display. In a touch screen panel having a laminated structure of a cover panel (glass or plastic) and a conductive film (film coated with ITO), capacitance due to finger contact is transmitted to the sensing unit of the touch screen panel. In this case, the pressure-sensitive adhesive used in the touch screen panel is required to have a constant dielectric constant in order to improve touch performance.

Recently, as the structure of the touch screen panel is changed to an in-cell structure including a touch function inside an LCD (Liquid Crystal Display) cell, the thickness and the weight of the touch screen panel having a conventional on-cell structure have been increased. 20% less effective.

However, in the case of a touch screen panel having an in-cell structure, the distance from the touch sensor to the cover panel becomes far, and there is a problem in that touch performance is deteriorated when plastic is used instead of glass as the cover panel.

Therefore, there is a need for an optically transparent adhesive having a high dielectric constant.

Background art related to the present invention is Republic of Korea Patent Publication No. 10-2014-0046366 (2014.04.18. Publication), the document discloses an adhesive film, a pressure-sensitive adhesive composition for this and a display member comprising the same.

An object of the present invention is to provide a transparent adhesive for a touch panel having a dielectric constant of 6 or more.

The transparent pressure-sensitive adhesive according to the present invention for achieving the above object comprises a (meth) acrylate oligomer, a mixed monomer, a plasticizer and a photoinitiator containing an alkylene oxide in a polyether polyol, wherein the mixed monomer has a hydroxy group It is characterized by including at least 1 type of a monomer, the monomer which has a carboxyl group, and the monomer which has a functional group containing nitrogen.

The (meth) acrylate oligomer may include 20 to 70 mol% of alkylene oxide.

The transparent pressure-sensitive adhesive may include 30 to 60% by weight of the (meth) acrylate oligomer, 10 to 30% by weight of mixed monomers, 10 to 50% by weight of a plasticizer and 0.1 to 1% by weight of a photoinitiator.

The polyether polyol may include one or more of polyethylene glycol, polypropylene glycol, polybutylene glycol, polypentylene glycol, polytetramethylene glycol, polyhexamethylene glycol, polyhepta methylene glycol, and polydecamethylene glycol. have.

The photoinitiator may include one or more of benzoin-based initiators, hydroxy ketone-based initiators and amino ketone-based initiators.

The transparent adhesive may further include an additive including at least one of a UV stabilizer, a reinforcing agent and an antifoaming agent.

The transparent adhesive may further comprise 0.1 to 5% by weight additive.

The transparent adhesive according to the present invention may be applied between the touch panel and the cover glass to be used for gap-filling purposes.

In addition, by adjusting the content of the oligomer, monomer and plasticizer, it is possible to provide a transparent pressure-sensitive adhesive having a dielectric constant of 6 or more.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various forms, and only the present embodiments are intended to complete the disclosure of the present invention, and the general knowledge in the art to which the present invention pertains. It is provided to fully convey the scope of the invention to those skilled in the art, and the present invention is defined only by the scope of the claims. Like reference numerals refer to like elements throughout.

Hereinafter, a transparent adhesive for a touch panel according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

The transparent adhesive of the present invention is a liquid-type transparent adhesive, which is applied to a touch screen panel having a laminated structure such as a conductive film and a transparent base film, and may be used for gap-filling purposes. In addition, by having a dielectric constant of 6 or more, it is possible to cope with a change in touch performance due to a decrease in dielectric constant when the cover glass is replaced with plastic.

The transparent adhesive of this invention contains 30-60 weight% of (meth) acrylate oligomers, 10-30 weight% of mixed monomers, 10-50 weight% of plasticizers, and 0.1-1 weight% of photoinitiators.

The (meth) acrylate oligomer is present in the form of a gel and has a form in which an alkylene oxide is added to a polyether polyol.

A polyether polyol is a compound in which a polyol, which is a polyhydric alcohol, is bonded to a polyether, which is a high molecular compound connected by an ether bond (-O-). Polyether-based polyols are excellent in cohesion and flexibility and, when included in a (meth) acrylate oligomer, provide excellent curing properties and adhesion performance.

The polyether polyol may include one or more of polyethylene glycol, polypropylene glycol, polybutylene glycol, polypentylene glycol, polytetramethylene glycol, polyhexamethylene glycol, polyhepta methylene glycol, and polydecamethylene glycol. have.

The alkylene oxide serves to reduce the haze of the pressure-sensitive adhesive by promoting compatibility with the acrylate. Moreover, adhesive force can be maintained and durability of an adhesive can be improved. Alkylene oxides include ethylene oxide, propylene oxide, styrene oxide and the like.

It is preferable that the said (meth) acrylate oligomer contains 30-80 mol% of polyether polyols, and contains 20-70 mol% of alkylene oxide.

When the alkylene oxide is included in less than 20 mol%, there is a problem that it is difficult to raise the dielectric constant of the transparent adhesive to 6 or more. On the contrary, when it exceeds 70 mol%, it is difficult to ensure compatibility with the components included in the pressure-sensitive adhesive, there is a problem that is difficult to exhibit the target adhesive strength.

The transparent pressure-sensitive adhesive of the present invention contains 30 to 60% by weight of a (meth) acrylate oligomer containing an alkylene oxide, not only having a high dielectric constant but also having an excellent adhesive performance.

It is preferable that a mixed monomer contains 1 or more types of the monomer which has a high electronegativity, ie, the monomer which has a hydroxyl group, the monomer which has a carboxyl group, and the monomer which has a functional group containing nitrogen.

The mixed monomer is a monomer having a hydrophilic functional group, and is mixed with an acrylate oligomer to form a transparent adhesive, thereby controlling the dielectric constant, and may improve the adhesion performance and cohesion to secure reliability.

The monomer having a hydroxy group is hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 5-hydroxypentyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 10- Hydroxydecyl (meth) acrylate, (4-hydroxymethylcyclohexyl) methyl (meth) acrylate, caprolactone modified 2-hydroxyethyl (meth) acrylate, 2-acryloyloxyethyl-2-hydride Oxylethylphthalic acid, N-methylol (meth) acrylimide, N-hydroxyethyl (meth) acrylate, 2-hydroxy propyl (meth) acrylate, 2-hydroxy-3-propyl (meth) acrylate And 3-chloro-2-hydroxypropyl (meth) acrylate. The monomer having a carboxyl group may be acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, fumaric acid, glycolic acid, cinnamic acid, acrylic acid dimer, methacrylic acid dimer, acrylic acid trimer, acrylic acid tetramer, methacrylic acid Tetramer, 2-acryloyloxyethyl succinic acid monoester, 2-methacryloyloxy succinic acid monoester, 2-acryloyloxyethyl phthalic acid monoester, 2-methacryloyloxyethyl phthalic acid monoester It may contain the above. The monomer having a nitrogen-containing functional group may include one or more of N-vinylpinyridone, N-vinylcaprolactam, acryloyl morpholine, acrylonitrile, acrylamide, and N, N-dimethylacrylamide. .

The transparent pressure-sensitive adhesive may be adjusted to include the adhesive strength 10 to 30% by weight. When the content of the mixed monomer is less than 10% by weight, the content is insufficient, the curing of the pressure-sensitive adhesive at the time of ultraviolet curing is not sufficiently made, the adhesive performance may be lowered. Conversely, if the content exceeds 30% by weight, the physical properties of the display may be lowered due to high curing shrinkage, which causes yellowing of the display.

The transparent pressure-sensitive adhesive including the oligomer and the mixed monomer exhibits excellent curing properties by acrylate having a double bond in UV curing.

By including the plasticizer which is a component which does not harden | cure even ultraviolet irradiation, the transparent adhesive of this invention can prevent excessive hardening shrinkage of an adhesive. The transparent adhesive of this invention does not contain a solvent and can contain a plasticizer and can adjust the viscosity of an adhesive. The transparent pressure-sensitive adhesive preferably contains 10 to 50% by weight of a plasticizer, and when the content of the plasticizer is out of this range, physical properties such as optical properties and adhesive strength of the pressure-sensitive adhesive may be lowered. The plasticizer may be, for example, a non-phthalate-free plasticizer.

A photoinitiator is a substance that is activated when a light of a certain wavelength is received to cause a radical reaction. The photoinitiator attacks a double bond of an oligomer and a monomer to initiate a curing reaction. More specifically, the oligomer and the mixed monomer are cured by an acrylate group which is a structure that can be cured during ultraviolet (UV) irradiation. Since the curable structure is activated during UV irradiation, the oligomer and the mixed monomer are characterized by high reactivity. The transparent adhesive of the present invention can be cured in a short time by UV curing including a photoinitiator.

The photoinitiator may include one or more of benzoin-based initiators, hydroxy ketone-based initiators and amino ketone-based initiators. More specifically, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylamino acetophenone, 2,2-dimethe Methoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexylphenylketone, 2- Methyl-1- [4- (methylthio) phenyl] -2-morpholinyl-1-propanone, 4- (2-hydroxyethoxy) phenyl-2- (hydroxy-2-propyl) ketone, benzo Phenone, 4,4'-diethylaminobenzophenone, dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-t-butylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone (2 -methylthioxanthone), 2-ethylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, benzyldimethyl ketal, acetophenone dimethyl ketal and oligo [2-hydroxy-2 -Methyl-1- [4- (1-methylvinyl) Carbonyl] propane and the like rice.

The transparent pressure-sensitive adhesive may comprise 0.1 to 1% by weight of the photoinitiator. When the content of the photoinitiator is less than 0.1% by weight, the content of the photoinitiator may be insufficient and the curing reaction may not be performed smoothly. On the contrary, when the content of the photoinitiator exceeds 1% by weight, a lot of molecules having a short bond length are generated, and thus durability is weak.

The transparent pressure-sensitive adhesive may further comprise 0.1 to 5% by weight of additives for controlling dielectric constant and improving reliability.

The additive may include one or more of an ultraviolet stabilizer, a reinforcing agent and an antifoaming agent. The UV stabilizer may be a benzotriazole-based UV stabilizer such as Tinuvin 234, Tinuvin 360 of Ciba.

As described above, by controlling the content of the oligomer, monomer, plasticizer and photoinitiator, the dielectric constant of the transparent adhesive can be controlled. Such a transparent adhesive may exhibit a dielectric constant of 6 or more, and may be applied between the touch panel and the cover glass to be expected to have excellent touch performance.

In addition, curing may be performed by irradiating the transparent pressure-sensitive adhesive with ultraviolet rays of about 2000 to 4000 mJ / cm ² for 20 to 80 seconds using a metal halide.

As described above, a specific embodiment of the transparent adhesive for a touch panel is as follows.

1. Preparation and Results of Transparent Adhesive

Examples 1-3 and Comparative Examples 1-3

50 mol% polypropylene glycol (PPG) acrylate oligomer containing 50 mol% ethylene oxide (EO), hydroxyethyl (meth) acrylate and acrylic acid as mixed monomer, polyethylene glycol (PEG) as plasticizer, benzoin n as photoinitiator -Butyl ether, a transparent pressure-sensitive adhesive containing an ultraviolet stabilizer as an additive in the content described in the following [Table 1] was prepared.

 TABLE 1

Dielectric constant measurement: by using a dielectric constant measuring device (Agilent, E4980A LCR meter + 16451B dielectric test fixture device), the dielectric constant of each of Examples 1 to 3 and Comparative Examples 1 to 3 were measured at room temperature conditions.

Adhesion performance measurement: A 150 μm thick step tape is attached to the slide glass, and then a liquid transparent adhesive is applied. Next, when the upper glass is covered on the transparent adhesive, the adhesive is 1 cm in diameter and 150 µm thick. It is cured by irradiation with 3000mJ / cm ² using a metal halide. Next, after sufficiently cooling at room temperature, the adhesion performance is measured by using a TA (Text Analyzer).

Referring to Table 1, in Examples 1 to 3, the content of oligomers, monomers, plasticizers, and the like satisfying the range set forth in the present invention, the dielectric constant of the pressure-sensitive adhesive can be controlled to 6 or more and confirmed that the adhesion performance is also excellent. Can be. In addition, the transparent adhesive is applied between the touch panel and the cover glass, it is expected that the touch performance is excellent.

On the contrary, in the case of Comparative Examples 1 to 3 in which the content of the oligomer and the monomer is outside the range set forth in the present invention, it can be confirmed that the dielectric constant is reduced or the adhesion performance is “normal” as compared with Examples 1 to 3.

Although the embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to the above embodiments and can be manufactured in various forms, and having ordinary skill in the art to which the present invention pertains. It will be understood by those skilled in the art that the present invention may be embodied in other specific forms without changing the technical spirit or essential features of the present invention. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive.

Claims (7)

A (meth) acrylate oligomer containing an alkylene oxide in a polyether polyol, a mixed monomer, a plasticizer and a photoinitiator,
The mixed monomer includes at least one of a monomer having a hydroxy group, a monomer having a carboxyl group, and a monomer having a functional group containing nitrogen, wherein the (meth) acrylate oligomer is contained in an amount of 30 to 60% by weight Transparent pressure sensitive adhesive.
The method of claim 1,
The (meth) acrylate oligomer is a transparent adhesive, characterized in that containing 20 to 70 mol% alkylene oxide.
The method of claim 1,
The transparent adhesive is a transparent adhesive, characterized in that 10-30% by weight of mixed monomers, 10-50% by weight of a plasticizer and 0.1-1% by weight of a photoinitiator.
The method of claim 1,
The polyether polyol includes one or more of polyethylene glycol, polypropylene glycol, polybutylene glycol, polypentylene glycol, polytetramethylene glycol, polyhexamethylene glycol, polyhepta methylene glycol, and polydecamethylene glycol Transparent adhesive.
The method of claim 1,
The photoinitiator is a transparent pressure-sensitive adhesive, characterized in that it comprises at least one of a benzoin initiator, a hydroxy ketone initiator and an amino ketone initiator.
The method of claim 1,
The transparent adhesive is a transparent adhesive, characterized in that it further comprises an additive comprising at least one of a UV stabilizer, a reinforcing agent and an antifoaming agent.
The method of claim 1,
The transparent pressure-sensitive adhesive, characterized in that it further comprises an additive 0.1 to 5% by weight.