KR101474920B1 - Acrylic adhesive having light transmitting and re-peelable property and Adhesive sheet thereby - Google Patents

Abstract

According to one aspect of the present invention, there is provided an ultraviolet ray-curable resin composition comprising a mixture of 90 to 98 parts by weight of a monomer capable of ultraviolet ray polymerization and 1 to 10 parts by weight of a silica hybrid containing a silica group, 0.1 to 2 parts by weight of a photoinitiator and 0.01 to 0.5 parts by weight of a molecular weight adjuster Producing a prepolymer (acrylic syrup); And 10 to 40 parts by weight of an acrylate oligomer, 0.1 to 3 parts by weight of a photoinitiator and 0.5 to 2 parts by weight of an acrylic monomer of a polyfunctional group in the prepolymer (acrylic syrup) to produce a final pressure-sensitive adhesive composition .
Accordingly, the acrylic pressure-sensitive adhesive excellent in light transmittance, adhesive strength, and re-releasability has excellent transparency, haze characteristics, and re-peelability, and can be used in a variety of adhesive-related fields.

Description

TECHNICAL FIELD [0001] The present invention relates to an acrylic adhesive having light transmittance and re-releasability and an adhesive sheet therefor,

The present invention relates to an acrylic pressure-sensitive adhesive which is excellent in not only adhesion but also light transmittance and re-releasability. More specifically, the present invention relates to an acrylic pressure- Acrylate oligomer and a photoinitiator to an ultraviolet-polymerized prepolymer (acrylic syrup), and to a pressure-sensitive adhesive sheet by the acrylic pressure-sensitive adhesive composition.

 A pressure-sensitive adhesive is a kind of adhesive, which is a temporary adhesive rather than a permanent adhesive. It is characterized by being able to be adhered even if a slight pressure is applied at room temperature for a short time without using water, solvent, heat or the like. The pressure-sensitive adhesive is manufactured in the form of a solvent type, a hot-melt type, an aqueous dispersion type, and the like. In any case, it should have cohesive force and elasticity so that it is adhered to the adherend, and that adhesive does not remain on the adhesive surface even if it is released by hand.

 The adhesive used for optics is used to attach each material when manufacturing a touch pad or a screen, and such a pressure sensitive adhesive requires properties such as high light transparency, adhesion, and heat resistance. Acrylic compounds are widely used in the production of pressure sensitive adhesives, and monomers containing an acid are used to improve adhesion. Corrosion caused by the acidic substances used is a problem in this case. For example, in Korean Patent Laid-Open Publication No. 2005-0027971, acrylic acid is used in the production of a tacky resin, which limits the use due to concern about corrosion.

In such a situation, various research results have been reported in order to improve the properties such as the adhesion property and the durability without the corrosion caused by the acid component. The prior art related to this is as follows.

(Japanese Patent No. 57-195208) which improves durability by using a silane coupling agent in the production of a pressure-sensitive adhesive for use in optical films, and a pressure-sensitive adhesive which improves high-temperature adhesive strength by using a high molecular weight acrylic resin not containing a low molecular weight compound As a result of the study, there is a literature (Japanese Patent No. 64-66283, No. 3-12471). When a silane coupling agent is used, improvement in durability is not significant. When a high molecular weight resin is used, it is difficult to control the crosslinking density depending on the amount of the crosslinking agent used.

Further, a technique of improving the releasability of a pressure-sensitive adhesive by adding a siloxane-based compound (U.S. Patent No. 4,151,319, No. 4,693,935, Korean Patent No. 10-0385720) has been reported, but the self-adhesive force is lowered.

1. Korean Unexamined Patent Publication No. 2005-0027971 entitled " Adhesive composition, process for producing the same, and adherent article "(published on March 21, 2005) 2. Korean Unexamined Patent Publication No. 0385720 entitled " Acrylic Pressure-Sensitive Adhesive Composition for Optics Excellent in Re-peelability and Laminate Using the Same "(published on Nov. 25, 2000)

It is an object of the present invention to overcome the above-mentioned problems of the prior art by providing an acrylic pressure-sensitive adhesive excellent in adhesion property, transparency, and re-peeling property using a silica hybrid compound containing an acrylic group, To produce an adhesive sheet.

Another object of the present invention is to re-peel off the adhesive sheet from a product which is poor in bonding or is recovered in the market by using a pressure-sensitive adhesive so that each component can be reused.

In order to attain the above object, one aspect of the present invention is to provide a photographic material, which comprises 0.1 to 2 parts by weight of a photoinitiator, 0.01 to 0.5 parts by weight of a molecular weight modifier, and 0.1 to 2 parts by weight of a photoinitiator, in a mixture of 90 to 98 parts by weight of a monomer mixture capable of ultraviolet polymerization and 1 to 10 parts by weight of a silica- (Acryl syrup) by using ultraviolet ray-polymerized parts by weight; And 10 to 40 parts by weight of an acrylate oligomer, 0.5 to 2 parts by weight of an acrylic monomer of a polyfunctional group, and 0.1 to 3 parts by weight of a photoinitiator, to the prepolymer (acrylic syrup) to produce a final pressure-sensitive adhesive composition .

At this time, as the composition of the monomer mixture, an aromatic compound or a heterocyclic compound containing a vinyl group may be used in combination with a reactive or non-reactive acrylate monomer serving as a basic property of the pressure-sensitive adhesive to improve adhesion and cohesive strength And the content of such a compound is 10 to 30 parts by weight based on 100 parts by weight of the total monomer mixture.

On the other hand, the silica hybrid compound containing an acrylic group has a structure of the general formula (1), and has an optical transparency and re-peelability.

(화학식 1)

(Formula 1)

In the general formula (1), S represents a nano-sized silica network structure prepared by a sol-gel method, R represents an organic compound structure containing a urethane group and a urea group, and n is an integer of 1 or more.

In another aspect of the present invention, a pressure-sensitive adhesive composition comprising the compounding composition of claim 1 is applied to the surface of various substrates including plastic such as polyethylene terephthalate (PET) to a predetermined thickness and ultraviolet cured to produce a pressure-sensitive adhesive sheet.

INDUSTRIAL APPLICABILITY As described above, the present invention provides an acrylic pressure-sensitive adhesive excellent in light transmittance, adhesive strength, and re-releasability, and thus has excellent transparency, haze characteristics, and re-

According to an aspect of the present invention, as a first step, an initiator and a molecular weight modifier are added to a mixture of an ultraviolet-polymerizable monomer containing a vinyl group-containing aromatic compound or a heterocyclic compound and a silica hybrid containing an acrylic group (Acrylic syrup) is produced by ultraviolet polymerization, and as a second step, an acrylic monomer of a polyfunctional group, an acrylate oligomer and a photoinitiator are further compounded. According to this method, since the nanosilica hybrid is bonded in the molecular chain, the heat resistance and the transparency are improved, and the adhesive composed of these components has excellent optical characteristics and re-peelability.

According to the detailed construction of the present invention, the ultraviolet-curable pressure-sensitive adhesive composition comprises 0.1 to 2 parts by weight of a photoinitiator, 0.01 to 0.5 parts by weight of a molecular weight modifier, and 0.1 to 2 parts by weight of a photoinitiator in a mixture of 90 to 98 parts by weight of a monomer capable of ultraviolet ray polymerization and 1 to 10 parts by weight of a silica- And 10 to 40 parts by weight of an acrylate oligomer, 0.5 to 2 parts by weight of an acryl monomer of a polyfunctional group and 0.1 to 3 parts by weight of a photoinitiator are added to the compound .

Each component of the acrylic pressure-sensitive adhesive composition will be described in more detail as follows.

In the first step of the present invention, the monomers used in the production of the ultraviolet curing type pressure-sensitive adhesive use 70 to 90 parts by weight of a reactive or non-reactive acrylate monomer serving as a basic property of the pressure- (Meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl acrylate, hexyl (meth) acrylate, 2-ethylhexyl (Meth) acrylate, hydroxy (meth) acrylate and the like, hydroxyl group-containing monomers such as hydroxy (meth) acrylate and glycidyl (meth) And monomers containing a nitrogen component such as a monomer, acrylamide or acrylonitrile.

At this time, according to the present invention, an aromatic compound or a heterocyclic compound containing a vinyl group is used in combination for improving adhesion and cohesion, and examples thereof include divinylbenzene, norbornene, cyclopentyl acrylate, cyclohexyl acrylate, vinyl Pyrrolidone and the like. The content of the compound is preferably 10 to 30 parts by weight based on 100 parts by weight of the total monomer. When the content is less than 10 parts by weight, the adhesive strength is lowered. When the content is more than 30 parts by weight, A problem occurs.

The silica hybrid compound containing an acrylic group of the present invention is represented by the following Formula 1 and is prepared by the following method.

First, an alkoxysilane containing an amino group capable of reacting with isocyanate and a diisocyanate are reacted at a reaction temperature of room temperature to 80 ° C to prepare a silane compound having a terminal isocyanate group. Then, an acrylic compound containing a hydroxy group was added thereto and stirred at a temperature of 40 to 60 ° C. for 1 to 5 hours until all of the isocyanates were reacted to produce an alkoxysilane compound containing an acrylic group. Then, a silane compound containing at least three alkoxy groups such as a methoxy group and an ethoxy group is added and water is added. Then, an aqueous solution of HCl is added as a catalyst, and the mixture is stirred at room temperature for one day to hydrolyze and condense, To prepare a silica hybrid compound (Formula 1).

(화학식 1)

(Formula 1)

In the above formula (1), S represents a nano-sized silica network structure prepared by a sol-gel method, R represents an organic compound structure containing a urethane group and a urea group, and n is an integer of 1 or more.

It is preferable to use this compound in an amount of 1 to 10 parts by weight based on the total monomer mixture. If the amount is less than 1 part by weight, heat resistance is not exhibited properly. If the amount exceeds 10 parts by weight, control of the reaction rate during prepolymer polymerization is difficult. Gel may be generated.

As the molecular weight modifier used in the present invention, a compound containing a thiol (-SH) group is used, and ethyl mercaptan, butyl mercaptan, hexyl mercaptan, dodecyl mercaptan, phenyl mercaptan, benzyl mercaptan, If the amount is less than 0.01 part by weight, the molecular weight is difficult to control. If the amount is more than 0.5 part by weight, the molecular weight becomes too low and the final properties are deteriorated.

As the acrylate oligomer used in the second step of the present invention, various types of acrylate oligomers such as urethane acrylate oligomer, polyester acrylate oligomer and epoxy acrylate oligomer can be used. The amount of the acrylate oligomer to be used is preferably 10 to 40 parts by weight based on the total amount of the prepolymer of the first stage. When the amount of the acrylate oligomer is less than 10 parts by weight, the viscosity is low and it is difficult to control the coating thickness. When the amount is more than 40 parts by weight, Is lowered.

The amount of the photoinitiator used in the present invention is preferably 0.1 to 3 parts by weight based on the total amount of the prepolymer of the first step. When the content of the photoinitiator is less than 0.1 parts by weight, the polymerization rate is slow and the conversion rate is low. The reaction speed is fast, but there are many oligomers having a low molecular weight, and the physical properties of the pressure-sensitive adhesive deteriorate. Examples of the photoinitiator include benzophenone, benzion, benzion methyl ether, benzion-n-butyl ether, benzion-isobutyl ether, 1-hydroxycyclohexyl phenyl ketone, 2,2-diethoxyacetophenone, Phenol, methylphenylglyoxylate, and ethylphenylpyloxylate, which may be used alone or in combination of two or more.

In another aspect of the present invention, the pressure-sensitive adhesive composition having the above-described compounding composition may be applied to the surface of various substrates including plastic such as polyethylene terephthalate (PET) to a predetermined thickness and ultraviolet cured to produce a pressure-sensitive adhesive sheet. As a result, the adhesive sheet can be re-peeled from a product which is poor in bonding or is recovered in the market, so that each component can be reused.

Hereinafter, the present invention will be described in detail with reference to Production Examples and Examples, but the present invention is not limited to these Production Examples and Examples.

(Example 1)

A double jacket reactor equipped with a UV lamp, cooling water and a stirrer was charged with 68 parts by weight of butyl acrylate, 10 parts by weight of 2-hydroxyethyl methacrylate, 20 parts by weight of divinylbenzene, , 2 parts by weight of a hybrid, 0.4 part by weight of an initiator (Drocur TPO, siba chemical) and 0.1 part by weight of butyl mercaptan, and the mixture was subjected to ultraviolet ray polymerization under a nitrogen atmosphere for 30 minutes to prepare an acrylic prepolymer. Then, 10 parts by weight of a urethane acrylate oligomer (product name: CN996, sartomer), 1 part by weight of 1,6-hexane diacrylate and 0.5 part by weight of an initiator (Irgacure 184, siba chemical) were added and mixed well for 20 minutes to prepare an ultraviolet- To prepare a pressure-sensitive adhesive. Next, the PET film was coated to a thickness of 100 탆, and the coating film was cured at a light amount of 700 mJ / cm 2 using an ultraviolet curing apparatus to produce a pressure-sensitive adhesive sheet.

<Preparation of silica hybrid compound containing acryl group>

88 g of 3-aminopropyltrimethoxysilane and 100 g of methylenediphenyl diisocyanate (MDI) were reacted at room temperature for 2 hours in a reactor equipped with a stirrer, a condenser and a thermometer to prepare an isocyanate-terminated silane compound. Then, 56 g of 2-hydroxyethyl methacrylate, which is an acrylic compound containing a hydroxy group, and 50 g of methyl ethyl ketone were mixed, 0.1 g of dibutyl tin dilaurate was added as a reaction catalyst, and 5 g of 5 And stirred for a time to prepare a silane alkoxide compound containing an acryl group. 200 g of tetramethoxysilane, 50 g of 3-methacryloxypropyltrimethoxysilane and 7 g of a 0.1N hydrochloric acid aqueous solution were added to the above compound and stirred at room temperature for 24 hours to obtain a silica hybrid compound containing an acrylic group.

(Example 2)

An acryl pressure-sensitive adhesive was prepared in the same manner as in Example 1, except that 62 parts by weight of butyl acrylate and 8 parts by weight of a silica hybrid containing an acrylic group were used in Example 1, and the properties were evaluated.

(Comparative Example 1)

An acrylic pressure-sensitive adhesive was prepared and evaluated for its physical properties in the same manner as in Example 1, except that the silica hybrid containing an acrylic group was not used in Example 1.

(Comparative Example 2)

The procedure of Example 1 was repeated except that 2 parts by weight of nano-sized silica (MEK-EC-2102, Nissan chemical) dispersed in methyl ethyl ketone was used instead of the silica hybrid containing an acrylic group in Example 1, A pressure sensitive adhesive was prepared and its physical properties were evaluated.

(Comparative Example 3)

An acryl pressure-sensitive adhesive was prepared in the same manner as in Example 1, except that 69.5 parts by weight of butyl acrylate and 0.5 parts by weight of a silica hybrid containing an acrylic group were used, and the properties were evaluated.

(Comparative Example 4)

An acryl pressure-sensitive adhesive was prepared in the same manner as in Example 1, except that 55 parts by weight of butyl acrylate and 15 parts by weight of a silica hybrid containing an acrylic group were used in Example 1, and the properties were evaluated.

<Test Method>

The properties of the pressure-sensitive adhesive sheets prepared in the above Examples and Comparative Examples were evaluated by the following methods.

① Optical characteristics

The haze and total light transmittance of the adhesive itself were evaluated using a spectrophotometer and a haze meter.

② Adhesion

The adhesive sheet thus prepared was attached to a slide glass, and then the adhesive strength was measured at a peeling speed of 100 mm / min using a universal tensile tester (UTM, TA-XT). The adhesive strength was measured in accordance with KSM 3725 (Test Method for Peel Strength of Adhesive).

③ Repeatability

The adhesive sheet was adhered to a slide glass, allowed to stand at 80 DEG C for 30 minutes, and peeled off. The extent to which the adhesive migrated to the slide glass was visually determined.

The results of the above experiment are shown in the following table.

Formulation table (Examples 1 to 2, Comparative Examples 1 to 4) Example
One Example
2 Comparative Example
One Comparative Example
2 Comparative Example
3 Comparative Example
4 Acrylic prepolymer
(Acrylic syrup)





Butyl acrylate 68 62 80 68 69.5 55 2-hydroxyethyl
Methacrylate 10 10 10 10 10 10 Divinylbenzene 20 20 20 20 20 20 Silica hybrids containing acrylic groups 2 8 - - 0.5 15 Nano-sized silica
(MEK-EC-2102) - - - 2 - - Initiator
(Drocur TPO) 0.4 0.4 0.4 0.4 0.4 0.4 Butyl mercaptan 0.1 0.1 0.1 0.1 0.1 0.1 Adhesion to acrylic prepolymers

Urethane acrylate oligomer (CN996) 10 10 10 10 10 10 1,6-hexane diacrylate One One One One One One Initiator
(Irgacure 184) 0.5 0.5 0.5 0.5 0.5 0.5

Pressure-sensitive adhesive sheet properties (Examples 1 to 2, Comparative Examples 1 to 4) Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Transmittance (%) 99.5 99.7 88.7 88.6 99.0 Haze (%) 0.3 0.3 0.7 0.9 0.6 Adhesion (N / cm) 6.0 5.7 5.3 4.1 5.2 Adhesive transfer No transition No transition Small amount of transition Small amount of transition Small amount of transition Repeatability ^* ◎ ◎ X △ △ - ○

*: Excellent: Excellent: Good: Fair: Fair: X: Poor

Table 2 summarizes the results of the experiments. In Examples 1 and 2, both the transmittance, the haze, the adhesive force, the adhesive transfer, and the re-peelability are satisfactory. Comparative Example 1 exhibited poor releasability with a slight amount of transition, Comparative Example 2 exhibited poor performance in terms of haze and adhesion, Comparative Example 3 was somewhat better than Comparative Examples 1 and 2, but did not meet required performance.

Meanwhile. In Comparative Example 4, gelation was partially generated during polymerization of the acrylic prepolymer, and evaluation of the properties was impossible.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention as defined by the appended claims. It is therefore intended that such variations and modifications fall within the scope of the appended claims.

Claims (4)

(Acrylic syrup) ultraviolet-polymerized using 0.1 to 2 parts by weight of a photoinitiator and 0.01 to 0.5 part by weight of a molecular weight modifier in a mixture of 90 to 98 parts by weight of a monomer mixture capable of ultraviolet polymerization and 1 to 10 parts by weight of a silica hybrid containing an acrylic group ; And
10 to 40 parts by weight of an acrylate oligomer, 0.5 to 2 parts by weight of an acrylic monomer of a polyfunctional group, and 0.1 to 3 parts by weight of a photoinitiator are added to the prepolymer (acrylic syrup) to produce a final pressure-sensitive adhesive composition Acrylic adhesive having light transmittance and re-releasability. The method according to claim 1,
As the composition of the monomer mixture, an aromatic compound or a heterocyclic compound containing a vinyl group is used in combination with a reactive or non-reactive acrylate monomer serving as a basic property of the pressure-sensitive adhesive to improve cohesion and cohesive force , And the content of these compounds is 10 to 30 parts by weight based on 100 parts by weight of the total monomer mixture. The method according to claim 1,
Wherein the silica hybrid compound containing an acryl group has a structure of formula (1).

(Formula 1)
In the general formula (1), S represents a nano-sized silica network structure prepared by a sol-gel method, R represents an organic compound structure containing a urethane group and a urea group, and n is an integer of 1 or more. A pressure-sensitive adhesive sheet obtained by applying a pressure-sensitive adhesive composition having the composition of claim 1 to a surface of various substrates including plastic such as polyethylene terephthalate (PET) to a predetermined thickness and ultraviolet curing.