KR101528962B1 - Adhesive composition and adhesives for protection film - Google Patents

Abstract

(Meth) acrylic copolymer formed by polymerization with at least one kind of (meth) acrylic acid ester monomer alone, and a peroxide. Also provided is a pressure-sensitive adhesive for a protective film formed from the pressure-sensitive adhesive composition.

Description

ADHESIVE COMPOSITION AND ADHESIVES FOR PROTECTION FILM < RTI ID = 0.0 >

A pressure-sensitive adhesive composition, and a pressure-sensitive adhesive for a protective film formed from the pressure-sensitive adhesive composition.

The surface of various display devices, such as a polarizing film, which is a type of flat panel display (FPD), or a protective window of a mobile phone, etc., always work on a workbench with a protective film attached for surface protection. At this time, the layer facing the adherend irrespective of the layer structure of the protective film is a pressure sensitive adhesive, and the performance of the pressure sensitive adhesive is a very important component for determining the adhesive force with the adherend or the adhesive transfer phenomenon.

In general, the pressure-sensitive adhesive composition for a protective film for forming the pressure-sensitive adhesive is formed by polymerizing an acrylic monomer and a functional group-containing monomer together or simultaneously forming a curing agent for an isocyanate compound such as NCO. In this case, Problems such as the occurrence of white spots or the peeling force with the adherend due to the aging change were raised. Japanese Patent Application Laid-Open No. 2003-329837 proposes to contain a plasticizer or an oligomer component in the acrylic polymer as the base polymer of the acrylic pressure-sensitive adhesive. However, the acrylic pressure-sensitive adhesive is required to exhibit the reworkability for the adherend, It can not be said that it satisfies workability and workability.

An embodiment of the present invention provides a pressure-sensitive adhesive composition which does not cause a phenomenon that a peeling force with an adherend rises due to occurrence of white spots or change with time under high-temperature and high-humidity conditions.

Another embodiment of the present invention provides a pressure-sensitive adhesive having a light-fastness property and good workability with respect to the adherend.

In one embodiment of the present invention, there is provided a pressure-sensitive adhesive composition comprising a (meth) acrylic copolymer formed by polymerization with at least one (meth) acrylic acid ester monomer alone and a peroxide.

The (meth) acrylic acid copolymer may not contain a structural unit derived from a monomer other than the (meth) acrylate monomer.

(Meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth) acrylate, Butyl (meth) acrylate, sec-butyl (meth) acrylate, pentyl (meth) acrylate, 2-ethylhexyl Acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, lauryl (meth) acrylate, tetradecyl (meth) acrylate and combinations thereof.

The peroxide may be at least one selected from the group consisting of di (2-ethylhexyl) peroxydicarbonate, di (4-t-butylcyclohexyl) peroxydicarbonate, di- Di-n-octanoyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, di-n-octanoyl peroxide, di (T-hexylperoxy) cyclohexanone, and combinations thereof, at least one member selected from the group consisting of (4-methylbenzoyl) peroxide, dibenzoyl peroxide, t-butyl peroxyisobutyrate, .

And may include about 0.1 part by weight to about 5.0 parts by weight peroxide with respect to 100 parts by weight of the (meth) acrylic copolymer.

The glass transition temperature of the (meth) acrylic monomer may be about -70 ° C to about 10 ° C.

The weight average molecular weight of the (meth) acrylic copolymer may be about 500,000 to about 200.

In another embodiment of the present invention, there is provided a pressure-sensitive adhesive for a protective film formed by the pressure-sensitive adhesive composition.

The gel fraction of the pressure-sensitive adhesive may be about 90% or more.

The pressure-sensitive adhesive was cut into a film having a width of 25 mm and a length of 10 cm, and the pressure-sensitive adhesive was attached to the non-alkali glass plate by reciprocating twice with a 2 kg roller and pulled off at 180 mm in the direction of 180 ° with respect to the pressure- The peel force may be about 2 g / 25 mm to about 15 g / 25 mm.

The pressure-sensitive adhesive was cut into a film having a width of 25 mm and a length of 10 cm, and the pressure-sensitive adhesive was reciprocated twice with a 2 kg roller on an alkali-free glass plate and allowed to stand at 150 ° C for 2 hours in a state of being attached to the glass plate. The peeling force when peeling off by pulling at 300 mm / min in the direction of 180 ° with respect to the pressure-sensitive adhesive surface may be about 2 g / 25 mm to about 15 g / 25 mm.

The pressure-sensitive adhesive composition for a protective film can improve the adhesive force and the processability and can form a pressure-sensitive adhesive which does not cause a white point phenomenon even under high-temperature and high-humidity conditions.

In addition, the pressure-sensitive adhesive maintains a constant adhesive force and peeling force, and can be most effectively used in the field of liquid crystal panel.

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

Pressure-sensitive adhesive composition

In one embodiment of the present invention, there is provided a pressure-sensitive adhesive composition comprising a (meth) acrylic copolymer formed by polymerization with at least one (meth) acrylic acid ester monomer alone and a peroxide.

In the pressure-sensitive adhesive composition, the (meth) acrylic acid copolymer may not contain a structural unit derived from a monomer other than the (meth) acrylic acid ester monomer. Usually, in the case of forming an acrylic pressure sensitive adhesive composition, in addition to the (meth) acrylic acid ester monomer, a functional group-containing monomer is often contained together. In this case, additional crosslinking agents and curing agents are required, and in the case of forming an acrylic pressure sensitive adhesive composition The acrylic polymer or the like has to be aged at a certain temperature for a certain period of time.

However, the pressure-sensitive adhesive composition does not contain any monomers other than the (meth) acrylic acid ester monomer, that is, it does not contain the functional group-containing monomer and does not undergo the aging step in forming the pressure-sensitive adhesive composition.

Specifically, the (meth) acrylic acid ester monomer is preferably selected from the group consisting of methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) (Meth) acrylate, 2-ethylbutyl (meth) acrylate, sec-butyl (meth) acrylate, pentyl (Meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, lauryl (meth) acrylate, tetradecyl have.

Since the pressure-sensitive adhesive composition contains a peroxide, unlike the case where a compound such as a general isocyanate is contained as a curing agent, the pressure-sensitive adhesive composition can prevent the phenomenon that a peeling force with the adherend rises due to the occurrence of a white spot at high- have.

Specifically, the peroxide may be at least one selected from the group consisting of di (2-ethylhexyl) peroxydicarbonate, di (4-t-butylcyclohexyl) peroxydicarbonate, di-sec-butylperoxydicarbonate, t-butyl peroxyneodecanoate, t-hexylperoxy pivalate, t-butyl peroxypivalate, dilauryl peroxide, di-n-octanoyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexano Di (t-hexylperoxy) cyclohexane acid, and combinations thereof, selected from the group consisting of di (4-methylbenzoyl) peroxide, dibenzoyl peroxide, t-butyl peroxyisobutyrate, At least one or more.

And may include about 0.1 part by weight to about 5.0 parts by weight peroxide with respect to 100 parts by weight of the (meth) acrylic copolymer. When the peroxide is contained in an amount of less than about 0.1 parts by weight based on 100 parts by weight of the (meth) acrylic copolymer, the durability may be low due to a low degree of curing. When the amount of the peroxide is more than about 5.0 parts by weight, Is low. Also, when excess peroxide remains unreacted, yellowing may occur. Therefore, it is advantageous to maintain the content within the above-mentioned range in order to maintain the durability and to minimize the change in appearance while maintaining the adhesive force and the peeling force.

The glass transition temperature of the (meth) acrylic monomer may be about -70 ° C to about 10 ° C. When the glass transition temperature of the (meth) acrylic monomer is less than about -70 캜, wetting is good but heat resistance may be lowered. When the glass transition temperature is more than about 10 캜, the adhesive force or peeling force There is a problem. Therefore, maintaining the above glass transition temperature range is advantageous in terms of maintaining the performance as a pressure-sensitive adhesive.

The weight average molecular weight of the (meth) acrylic copolymer may be about 500,000 to about 200. When the weight average molecular weight of the (meth) acrylic copolymer is less than about 500,000, the durability of the (meth) acrylic copolymer is lowered and the residue may remain during high temperature standing. When the weight average molecular weight exceeds about 2,000,000, the durability is good but the wetting is low . Therefore, maintaining the above-mentioned range of molecular weight is effective in that wettability and durability are maintained.

Adhesive for protective film

Another embodiment of the present invention provides a pressure-sensitive adhesive for a protective film formed from a pressure-sensitive adhesive composition comprising a (meth) acrylic copolymer and a peroxide formed by polymerization of at least one (meth) acrylic acid ester monomer only.

The pressure-sensitive adhesive composition can form the pressure-sensitive adhesive for the protective film by drying the solvent at a predetermined temperature and then heating and curing the pressure-sensitive adhesive composition once again at a limited high temperature at which the peroxide becomes a completely free radical.

Specifically, in order to form a pressure-sensitive adhesive for a protective film with the pressure-sensitive adhesive composition, that is, to secure a cured product of the pressure-sensitive adhesive composition, the solvent contained in the pressure-sensitive adhesive composition may be dried at a temperature of about 70 ° C to about 90 ° C . At this time, once the solvent-dried pressure-sensitive adhesive composition is heated again at about 140 ° C to about 180 ° C, the peroxide is formed into a free radical, and a step of causing hardening due to the radical formation of the polymer chain can be made. The pressure-sensitive adhesive formed through the above process can maintain a constant gel fraction.

When the heating temperature after drying is less than about 140 ° C, there is a possibility that the peroxide is less or the percentage of the peroxide reacts with the polymer chain is low and the gel fraction is lowered. When the heating temperature is higher than about 180 ° C, There is a risk of yellowing, and since a release film must be used with a high durability grade, appearance after coating may be poor. Therefore, the pressure-sensitive adhesive for a protective film formed by maintaining the heating temperature can secure a constant gel fraction, thereby maintaining a certain level of peeling force.

Specifically, the gel fraction of the pressure-sensitive adhesive formed by the pressure-sensitive adhesive composition may be about 90% or more, specifically about 95% or more. If the gel fraction of the pressure-sensitive adhesive is less than 90%, the pressure-sensitive adhesive can not secure a certain level of adhesion and peeling force, and is affected by the external environment such as high temperature and high humidity.

The gel fraction is the gel fraction measured after immersing the pressure-sensitive adhesive composed of the pressure-sensitive adhesive composition in a polar solvent for 48 hours and heating at 110 ° C for about 2 hours, as shown in Equation 1 below.

[Equation 1]

X (gel fraction) = [1- (Xi-Xs) / Xi] x 100 (%)

Where Xi is the weight of the adhesive, Xs is the weight of the adhesive remaining on the wire net after being dissolved in the solvent, filtered on a 300 mesh wire mesh and dried at 110 ° C for 2 hours, and X is the gel fraction.

Depending on the polarity, the time for the pressure-sensitive adhesive to melt and separate may vary, but if the pressure is about 24 hours to about 48 hours, the pressure sensitive adhesive is sufficiently separated to leave only the pressure-sensitive adhesive, so that the polar solvent used in the present invention is not limited as long as it has a slight polarity. Specific examples thereof include chloroform, ethyl acetate, acetone, methanol, ethanol, isopropanol, butanol, and dimethylformamide.

Specifically, the pressure-sensitive adhesive for a protective film was laminated on a non-treated PET film as a backing film, cut into a film having a width of 25 mm and a length of 10 cm, and the pressure-sensitive adhesive was reciprocated twice with a 2 kg roller on an alkali- The peeling force when peeling off by pulling at 300 mm / min in the direction of 180 ° with respect to the adhered adhesive surface may be about 2 g / 25 mm to about 15 g / 25 mm. Since the pressure-sensitive adhesive for film formation functions to protect the surface of the adhered material during transport or storage by maintaining the peeling force in the above range and removes it easily without residue due to low peeling force at the time of desorption, Is high.

The pressure-sensitive adhesive for a protective film was laminated on a untreated PET film as a backing film, cut into a film having a width of 25 mm and a length of 10 cm, and the pressure-sensitive adhesive was attached to the non-alkali glass plate by reciprocating twice with a 2 kg roller, The adhesive sheet is allowed to stand at 150 DEG C for 2 hours in a state of being attached to a glass plate and then peeled off at a rate of 300 mm / have. The film-shaped pressure-sensitive adhesive maintains a peeling force similar to the peeling force before storage at a high temperature even after storage at a high temperature, and the peeling force is not increased due to the external environment such as high temperature storage.

Therefore, even after storage at a high temperature, the pressure-sensitive adhesive maintains the peeling force in the above-mentioned range, thereby being utilized in the fields of polarizing plate protective films, touch screen panel shipping and permanent adhesion protective films, prism sheet protective films, Is high.

Hereinafter, specific embodiments of the present invention will be described. However, the embodiments described below are only intended to illustrate or explain the present invention, and thus the present invention should not be limited thereto.

< Example  And Comparative Example >

Example  One

1.5 parts by weight of peroxide dibenzoyl peroxide as a curing agent to 100 parts by weight of the acrylic copolymer was added to an acrylic copolymer (molecular weight: 1.2 million) polymerized with ethylhexyl acrylate (EHA) alone to obtain an acrylic pressure-sensitive adhesive composition .

Example  2

A pressure-sensitive adhesive composition was prepared in the same manner as in Example 1, except that 0.8 part by weight of peroxide dibenzoyl peroxide was used in the acrylic copolymer (molecular weight: 800,000) formed by polymerizing only butyl acrylate (BA).

Comparative Example  One

98 parts by weight of ethylhexyl acrylate (EHA) and 2.0 parts by weight of hydroxyethyl acrylate (HEA) were formed, and toluene diisocyanate was added to 100 parts by weight of the acrylic copolymer Was added to the pressure-sensitive adhesive composition for an acrylic protective film to prepare a pressure-sensitive adhesive composition for an acrylic protective film.

Acrylic copolymer Acrylic copolymer Molecular weight Hardener Example 1 EHA 1.2 million BPO 1.0 Example 2 BA 80 million BPO 0.8 Comparative Example 1 EHA / 2.0HEA 80 million TDI 5.0

< Experimental Example > - Physical properties of pressure-sensitive adhesive composition

The pressure-sensitive adhesive compositions of Examples 1 and 2 were maintained in a 90 ° C oven for 3 minutes to dry the solvent, and then heated in a 150 ° C Matis oven for 2 minutes to complete the curing of the peroxide. Thereafter, the pressure-sensitive adhesive, which was dried and cured in an oven, was laminated on a 50um untreated PET film to produce a film-type pressure-sensitive adhesive.

On the other hand, the pressure-sensitive adhesive composition of Comparative Example 2 was maintained in a 110 ° C oven for 5 minutes in the same manner as in Examples 1 and 2 to completely dry the solvent, and then laminated on a 50um untreated PET film to produce a film- . The above Examples 1 and 2 were not aged after curing, and Comparative Example 1 was aged at 50 캜 for 3 days after curing.

1) Gel fraction: The weight of the pressure-sensitive adhesive was measured, immersed in ethyl acetate solvent for 48 hours, taken out again, and heated in an oven at 110 ° C for 2 hours. Thereafter, the difference between the weight of the first adhesive and the weight of the latter adhesive was calculated and the final gel fraction was measured. The specific gel fraction was measured according to the above-mentioned formula (1).

2) Peeling force: The film-shaped pressure-sensitive adhesive was cut to a width of 25 mm and a length of 10 cm, and then attached to a non-alkali glass plate by reciprocating twice with a 2 kg roller and held at a rate of 300 mm / The peeling force at the time of peeling off was measured (initial peeling force). Further, the film-form adhesive was stored on the glass plate at 150 DEG C for 2 hours, and the peel force was measured in the same manner as the initial peel force (peeling force after storage at high temperature).

3) White spot phenomenon: The film-like adhesive adhered to the glass at 85 DEG C and 85% RH was stored for 1 day to observe whether white spots were observed.

Gel fraction (%) Initial peel force
(g / 25 mm) Peel force after storage at high temperature (g / 25mm) one hundred points Example 1 98 7 9 X Example 2 96 10 13 X Comparative Example 1 95 12 30 Occur

The results of the measurement and observation are shown in Table 2 above. The pressure-sensitive adhesive compositions of Examples 1 and 2 including a (meth) acrylic copolymer formed by polymerization with only a (meth) acrylic acid ester monomer contained peroxide as a curing agent to form a pressure-sensitive adhesive, As a result, it was found that a certain level of adhesion was secured. In addition, there was almost no difference between the initial peeling force of the pressure-sensitive adhesive and the peeling force after storage at high temperature. As a result, the peeling force did not rise due to curing using peroxide as a curing agent. And no spots were observed.

In contrast, in Comparative Example 1, the gel fraction was measured at 95% with a pressure-sensitive adhesive composition containing a monomer having a functional group in addition to the (meth) acrylic acid ester monomer, so that it was possible to secure some degree of adhesion and peeling force. When the isocyanate compound was used as a curing agent, white spots also occurred in an environment of high and high temperature due to the isocyanate compound and the like which were not involved in the reaction.

As a result, in the case of using an acrylic copolymer composed solely of a (meth) acrylic acid ester-based monomer and forming a pressure-sensitive adhesive with a pressure-sensitive adhesive composition containing peroxide as a curing agent, the aging step can be omitted and the peeling- The occurrence of the phenomenon was suppressed.

Claims (11)

(Meth) acrylic copolymer and peroxide formed by polymerization with at least one kind of (meth) acrylic acid ester monomer alone, wherein the (meth) acrylic copolymer has a weight average molecular weight of 500,000 to 1,200,000, a gel fraction of 90 %.
The method according to claim 1,
Wherein the (meth) acrylic acid copolymer does not contain a structural unit derived from a monomer other than the (meth) acrylic acid ester monomer.
The method according to claim 1,
(Meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth) acrylate, Butyl (meth) acrylate, sec-butyl (meth) acrylate, pentyl (meth) acrylate, 2-ethylhexyl (Meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, lauryl (meth) acrylate, tetradecyl
Sensitive adhesive composition.
The method according to claim 1,
The peroxide may be at least one selected from the group consisting of di (2-ethylhexyl) peroxydicarbonate, di (4-t-butylcyclohexyl) peroxydicarbonate, di- Di-n-octanoyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, di-n-octanoyl peroxide, di (T-hexylperoxy) cyclohexanone, and combinations thereof, at least one member selected from the group consisting of t-butylperoxy isobutyrate, t-butylperoxy isobutyrate,
Sensitive adhesive composition.
The method according to claim 1,
Based on 100 parts by weight of the (meth) acrylic copolymer, 0.1 part by weight to 5.0 parts by weight of peroxide
Sensitive adhesive composition.
The method according to claim 1,
The (meth) acrylic monomer has a glass transition temperature of -70 ° C to 10 ° C
Sensitive adhesive composition.
delete A pressure-sensitive adhesive for a protective film formed by the pressure-sensitive adhesive composition of claim 1.
9. The method of claim 8,
Wherein the pressure-sensitive adhesive has a gel fraction of 90% or more.
9. The method of claim 8,
The pressure-sensitive adhesive was cut into a film having a width of 25 mm and a length of 10 cm, and the pressure-sensitive adhesive was attached to the non-alkali glass plate by reciprocating twice with a 2 kg roller and pulled off at 180 mm in the direction of 180 ° with respect to the pressure- Peel strength of 2 g / 25 mm to 15 g / 25 mm
Adhesive for protective film.
9. The method of claim 8,
The pressure-sensitive adhesive was cut into a film having a width of 25 mm and a length of 10 cm, and the pressure-sensitive adhesive was reciprocated twice with a 2 kg roller on an alkali-free glass plate and allowed to stand at 150 ° C for 2 hours in a state of being attached to the glass plate. The peeling force when peeling off by pulling at 300 mm / min in the direction of 180 ° to the pressure-sensitive adhesive surface is 2 g / 25 mm to 15 g / 25 mm
Adhesive for protective film.