CN101586006A - Pressure-sensitive adhesive composition, pressure-sensitive adhesive sheet, and method for producing the same - Google Patents

Abstract

The present invention relates to a pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet and a production method thereof. The present invention relates to a pressure-sensitive adhesive composition comprising a monomer mixture or an acrylic copolymer material obtained by at least partially polymerizing a monomer mixture as a main component, the monomer mixture comprising: at least one selected from the group consisting of the following formula (I )CH ₂ ＝C(R ¹ )COOR ² represents an alkyl (meth)acrylate monomer (monomer m1), wherein R ¹ is a hydrogen atom or a methyl group, and R ² is a Alkyl atoms; at least one monomer (monomer m2) selected from N-hydroxyalkyl (meth)acrylamides represented by the following formula (II) CH ₂ ═C (R ³ ) CONHR ⁴ , wherein R ³ is a hydrogen atom or a methyl group, and R is a hydroxyalkyl group with ^2-4 carbon atoms; and at least one selected from N-vinyl cyclic amides and (meth)acrylamides that may have N-alkyl groups a monomer (monomer m3); and the monomer mixture substantially does not include a carboxyl group-containing monomer.

Description

Pressure-sensitive adhesive composition, pressure-sensitive adhesive sheet, and production method thereof

technical field

The present invention relates to pressure-sensitive adhesive (hereinafter also referred to as adhesive, and this will be used hereinafter) compositions and pressure-sensitive adhesive sheets, and in particular, the present invention relates to adhesives suitable for direct bonding on metal surfaces A pressure-sensitive adhesive sheet for applications or other various applications, and relates to a pressure-sensitive adhesive composition for the pressure-sensitive adhesive sheet. The present invention further relates to a method of producing the pressure-sensitive adhesive sheet.

Background technique

In recent years, pressure-sensitive adhesive sheets have been used in various aspects such as fixing (bonding), transportation, protection, decoration and the like of articles. Typical examples of the pressure-sensitive adhesive sheet include those provided with a pressure-sensitive adhesive layer formed by using an acrylic adhesive composition. The acrylic adhesive composition is constituted such that it can form a pressure-sensitive adhesive layer containing an acrylic copolymer as a matrix polymer. For the purpose of improving adhesive performance and the like, as acrylic copolymers, those containing an alkyl (meth)acrylate as a main component (main component) and further containing a copolymer composition including a carboxyl group-containing monomer such as acrylic acid are generally used .

However, for a pressure-sensitive adhesive sheet used for an article having a part composed of a material easily affected by an acid (for example, an article having a metal surface, such as an electronic part), when it has a carboxyl group-containing The carboxyl group in the acrylic copolymer may be the cause of adverse effects on the above materials (such as corrosion of metal surfaces) when the monomers are copolymerized. Accordingly, a pressure-sensitive adhesive composition for forming a pressure-sensitive adhesive layer provided in a pressure-sensitive adhesive sheet for use in these applications (in particular, an application for direct bonding on a metal surface), A structure that enables formation of a pressure-sensitive adhesive layer having an acrylic copolymer of a copolymerized composition not including a carboxyl group-containing monomer as a matrix polymer is preferable. As background art documents on such techniques, JP-A-2007-63536, JP-A-2005-325250, and JP-A-2007-264092 can be exemplified. As a background art document on an acrylic adhesive, JP-A-2007-264092 can be exemplified. JP-A-2003-165965 is a background art document on pressure-sensitive adhesives and adhesives.

However, a pressure-sensitive adhesive composition that does not include a carboxyl group-containing monomer tends to have insufficient adhesive properties of a pressure-sensitive adhesive sheet formed from the composition. In this regard, JP-A-2007-63536 describes copolymerization with specific maleimide compounds, and JP-A-2005-325250 describes copolymerization with monomers containing nitrogen atoms such as N-acryloylmorpholine , and JP-A-2000-303045 describes the use of a specific monomer such as phenoxyethyl acrylate as a main monomer component. However, even in pressure-sensitive adhesive sheets formed by using these techniques, there is room for improvement in adhesive performance. For example, it is useful to provide a pressure-sensitive adhesive sheet that exhibits desired cohesion without using a carboxyl group-containing monomer and is further capable of forming a pressure-sensitive adhesive sheet with increased repelling resistance (adhesiveness on a curved surface) pressure-sensitive adhesive compositions.

Contents of the invention

The present invention has been made in light of the conventional circumstances, and an object of the present invention is to provide an acrylic capable of forming a pressure-sensitive adhesive sheet having improved adhesive properties (particularly, repulsion resistance) without substantially using a carboxyl group-containing monomer Adhesive composition. Another object of the present invention is to provide a pressure-sensitive adhesive sheet using the pressure-sensitive adhesive composition. Still another object of the present invention is to provide a method for producing a pressure-sensitive adhesive sheet.

That is, the present invention relates to the following items (1)-(8).

(1) A pressure-sensitive adhesive composition comprising a monomer mixture or an acrylic copolymer material obtained by at least partially polymerizing a monomer mixture as a main component,

The monomer mixture includes:

At least one monomer selected from alkyl (meth)acrylates represented by the following formula (I) in an amount of 50 to 85% by weight based on the total amount of the monomer mixture (monomer m1):

CH ₂ =C(R ¹ )COOR ² (I)

wherein R ¹ is a hydrogen atom or a methyl group, and R ² is an alkyl group having 1-20 carbon atoms,

At least one monomer selected from N-hydroxyalkyl (meth)acrylamides represented by the following formula (II) in an amount of 0.1 to 12% by weight based on the total amount of the monomer mixture (monomer m2):

CH ₂ =C(R ³ )CONHR ⁴ (II)

wherein R ³ is a hydrogen atom or a methyl group, and R ⁴ is a hydroxyalkyl group with 2-4 carbon atoms, and

Based on the total amount of the monomer mixture, the amount is 10-40% by weight of at least one monomer selected from N-vinyl cyclic amides and (meth)acrylamides that may have N-alkyl groups (monomer m3); and

The monomer mixture is substantially free of carboxyl group-containing monomers.

(2) The composition according to (1), wherein the monomer m1, the monomer m2, and the monomer m3 are contained in a total amount of 90 wt% or more based on the total amount of the monomer mixture.

(3) The composition according to (1) or (2), wherein the monomer mixture has a temperature such that the acrylic copolymer obtained by polymerizing the monomer mixture has a glass transition temperature (Tg) of -10°C or lower. Monomer composition.

(4) The composition according to any one of (1) to (3), wherein the monomer m2 is N-(2-hydroxyethyl)(meth)acrylamide.

(5) The composition according to any one of (1)-(4), wherein the monomer m3 is at least one monomer selected from N-vinyl cyclic amides represented by the following formula (III):

wherein ^R is a divalent organic group.

(6) The composition according to any one of (1) to (5), which is used for a pressure-sensitive adhesive sheet directly bonded to a metal surface.

(7) A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed by using the composition according to any one of (1) to (6).

(8) A method of producing a pressure-sensitive adhesive sheet, the method comprising:

producing a pressure-sensitive adhesive composition comprising a monomer mixture or an acrylic copolymer material obtained by partially polymerizing the monomer mixture, and 0.01 to 2 parts by weight of a photopolymerization initiator based on 100 parts by weight of the monomer mixture,

The monomer mixture includes:

At least one monomer selected from alkyl (meth)acrylates represented by the following formula (I) in an amount of 50 to 85% by weight based on the total amount of the monomer mixture (monomer m1):

CH ₂ =C(R ¹ )COOR ² (I)

wherein R ¹ is a hydrogen atom or a methyl group, and R ² is an alkyl group having 1-20 carbon atoms,

At least one monomer selected from N-hydroxyalkyl (meth)acrylamides represented by the following formula (II) in an amount of 0.1 to 12% by weight based on the total amount of the monomer mixture (monomer m2):

CH ₂ =C(R ³ )CONHR ⁴ (II)

wherein R ³ is a hydrogen atom or a methyl group, and R ⁴ is a hydroxyalkyl group with 2-4 carbon atoms, and

Based on the total amount of the monomer mixture, the amount is 10-40% by weight of at least one monomer selected from N-vinyl cyclic amides and (meth)acrylamides that may have N-alkyl groups (monomer m3), and

The monomer mixture is substantially free of carboxyl-containing monomers;

applying the pressure sensitive adhesive composition on a support; and

The applied composition is cured by irradiating the applied composition with light, thereby forming a pressure-sensitive adhesive layer.

The "acrylic copolymer material" may be a partial polymerization product of a monomer mixture, or an acrylic copolymer obtained by polymerizing almost all of the monomer mixture (eg, about 95% or more, preferably about 99% or more conversion). The partial polymerization product of the monomer mixture may generally include a polymer obtained by polymerizing a part proportion of the monomers constituting the monomer mixture (which may include monomers having a relatively low degree of polymerization, and for example, may include monomers having a degree of polymerization generally not exceeding A polymer (which may also be called an oligomer) with a weight average molecular weight of 1×10 ⁴ ) and unpolymerized monomers. The conversion rate of the partially polymerized product (ie, the proportion of previously polymerized monomers in the monomers used) may be, for example, about 2 to 50%. In addition, the expression that the pressure-sensitive adhesive composition disclosed herein includes a monomer mixture or an acrylic copolymer material as a main component means an acrylic copolymer obtained by polymerizing a monomer mixture (which may be Or a polymer obtained by polymerizing or curing a part of its polymerized product by irradiating light, or basically an acrylic copolymer material itself) as the matrix polymer (main component of the polymer component) constituting the pressure-sensitive adhesive A pressure sensitive adhesive formed from an agent composition.

Since the pressure-sensitive adhesive composition contains a monomer mixture or an acrylic copolymer material substantially not using a carboxyl group-containing monomer (carboxyl group-containing monomer) as a main component, even when the pressure-sensitive adhesive composition will be formed by using the composition When the pressure-sensitive adhesive layer is directly bonded to a surface composed of a material easily affected by an acid, such as a metal surface, it can also prevent the metal surface or the like from being corroded by carboxyl groups. In addition, by using an acrylic copolymer having a monomer composition (ratio of each monomer used as a monomer component) including monomer m1 as a main component and predetermined amounts of monomer m2 and monomer m3 as a main component Composition, a pressure-sensitive adhesive layer (or thus a pressure-sensitive adhesive sheet including a pressure-sensitive adhesive layer, and this will be used hereinafter) having high cohesion and exhibiting further improved repulsion resistance can be formed.

As a preferred example of monomer m2, mention may be made of N-(2-hydroxyethyl)(meth)acrylamide. Among them, N-(2-hydroxyethyl)acrylamide is preferably used. Also as the monomer m3, at least one monomer selected from N-vinyl cyclic amides represented by the following formula (III) can be preferably used:

wherein ^R is a divalent organic group.

As preferred examples of N-vinyl cyclic amides, mention may be made of N-vinyl-2-pyrrolidone (ie compounds wherein R ⁵ in formula (III) is propylene).

In a preferred embodiment of the pressure-sensitive adhesive composition disclosed herein, based on the total amount of the monomer mixture, the total amount of the monomers m1, m2 and m3 is about 90 wt% or more. The pressure-sensitive adhesive composition containing the monomer mixture or the acrylic copolymer material of this composition as a main component can form a pressure-sensitive adhesive layer having more excellent quality stability.

The monomer mixture preferably has a monomer composition such that the acrylic copolymer obtained by polymerizing the monomer mixture (i.e., the matrix polymer in a pressure-sensitive adhesive formed from the pressure-sensitive adhesive composition) has A glass transition temperature (Tg) of about -10°C or less (typically about -10 to -70°C). The adhesive composition can form, for example, a pressure-sensitive adhesive layer exhibiting good adhesive properties (tackiness, etc.) at normal temperature (generally about 5-35°C, such as 20-25°C).

In another preferred embodiment of the pressure-sensitive adhesive composition disclosed herein, the composition comprises a photopolymerization initiator, and is formed from a pressure-sensitive adhesive composition curable by irradiation with light (such as ultraviolet rays) ( photocurable pressure sensitive adhesive composition). For example, it may be a pressure-sensitive adhesive composition formed by using about 0.01-2 parts by weight of a photopolymerization initiator based on 100 parts by weight of a monomer mixture. A pressure-sensitive adhesive layer formed by irradiating light onto the photocurable pressure-sensitive adhesive composition (which may be referred to as a photopolymerizable pressure-sensitive adhesive composition, etc.) can exhibit more Good adhesive properties (eg cohesion, repulsion resistance, etc.).

According to the present invention, there is provided a pressure-sensitive adhesive sheet including a pressure-sensitive adhesive layer comprising, as a matrix polymer, an acrylic copolymer obtained by polymerizing any one of the monomer mixtures disclosed herein. The pressure-sensitive adhesive layer may be a pressure-sensitive adhesive layer formed by using any one of the pressure-sensitive adhesive compositions disclosed herein. That is, according to the present invention, there is provided a pressure-sensitive adhesive sheet including a pressure-sensitive adhesive layer formed by using any one of the pressure-sensitive adhesive compositions disclosed herein. Since the pressure-sensitive adhesive sheet contains a polymer derived from a monomer mixture or an acrylic copolymer material as a matrix polymer, even when it is directly bonded to a surface composed of a material easily affected by an acid such as a metal surface When there is no metal surface corrosion, etc. Therefore, it is suitable as a pressure-sensitive adhesive sheet for direct bonding on a metal surface (a pressure-sensitive adhesive sheet to be bonded to a metal surface). In addition, the pressure-sensitive adhesive sheet can exhibit good adhesiveness on objects to be bonded other than metal surfaces, as well as excellent cohesive force and repulsion resistance. Furthermore, any one of the pressure-sensitive adhesive compositions disclosed herein is suitable as a pressure-sensitive adhesive composition for forming a pressure-sensitive adhesive layer of a pressure-sensitive adhesive sheet to be bonded to a metal surface.

According to the present invention, there is also provided a method of producing a pressure-sensitive adhesive sheet (which may be a pressure-sensitive adhesive sheet to be bonded to a metal surface) on a metal surface. The method includes the step of preparing a pressure-sensitive adhesive composition comprising a monomer mixture satisfying all of the following conditions (a)-(d), or an acrylic copolymer material obtained by partially polymerizing the monomer mixture. In a preferred embodiment, the photopolymerization initiator is used in this step in an amount of about 0.01-2 parts by weight based on 100 parts by weight of the monomer mixture.

(a) The monomer mixture contains at least one monomer (monomer m1) selected from alkyl (meth)acrylates represented by the following formula (I). Based on the total amount of monomer mixture, the content of monomer m1 can be 50-85wt%:

CH ₂ =C(R ¹ )COOR ² (I)

Wherein R ¹ is a hydrogen atom or a methyl group, and R ² is an alkyl group having 1-20 carbon atoms.

(b) The monomer mixture contains at least one monomer selected from N-hydroxyalkyl (meth)acrylamides represented by the following formula (II) (monomer m2). Based on the total amount of monomer mixture, the content of monomer m2 can be 0.1-12wt%:

CH ₂ =C(R ³ )CONHR ⁴ (II)

Wherein ^R3 is a hydrogen atom or a methyl group, and ^R4 is a hydroxyalkyl group with 2-4 carbon atoms.

(c) The monomer mixture contains at least one monomer selected from N-vinyl cyclic amides and (meth)acrylamides which may have N-alkyl groups (monomer m3). Based on the total monomer mixture, the content of monomer m3 may be 10-40 wt%.

(d) The monomer mixture contains substantially no carboxyl group-containing monomers.

The method for producing a pressure-sensitive adhesive sheet further includes a step of applying a pressure-sensitive adhesive composition on a support, and curing the composition by irradiating light onto the applied composition, thereby forming Step of pressure sensitive adhesive layer.

By this method, a pressure-sensitive adhesive sheet that can be preferably used even on a surface easily affected by an acid such as a metal surface and further has good adhesive properties (cohesion, repulsion resistance, etc.) can be efficiently produced. In addition, a method for producing a pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer is formed by using the photocurable adhesive composition as described above is preferable because a thick adhesive layer can be easily formed.

Description of drawings

FIG. 1 is a schematic cross-sectional view showing a structural example of a pressure-sensitive adhesive sheet according to the present invention.

Fig. 2 is another schematic cross-sectional view showing a structural example of the pressure-sensitive adhesive sheet according to the present invention.

Fig. 3 is still another schematic cross-sectional view showing a structural example of the pressure-sensitive adhesive sheet according to the present invention.

Fig. 4 is another schematic cross-sectional view showing a structural example of the pressure-sensitive adhesive sheet according to the present invention.

Fig. 5 is still another schematic cross-sectional view showing a structural example of the pressure-sensitive adhesive sheet according to the present invention.

Fig. 6 is still another schematic cross-sectional view showing a structural example of the pressure-sensitive adhesive sheet according to the present invention.

DESCRIPTION OF REFERENCE NUMBERS AND REFERENCE SIGNS

1: Substrate

2: Pressure sensitive adhesive layer

3: Isolation liner

11, 12, 13, 14, 15, and 16: Pressure-sensitive adhesive sheets

Detailed ways

Suitable embodiments of the invention will be described hereinafter. In addition, elements necessary for carrying out the present invention other than those specifically mentioned in this specification can be appreciated by those skilled in the art based on the design of the background technology in the relevant field. The present invention can be implemented based on ordinary technical knowledge in the relevant field and the contents disclosed in this specification.

The pressure-sensitive adhesive composition disclosed herein has a predetermined monomer mixture or an acrylic copolymer material obtained by partial polymerization of the monomer mixture as a main component. The monomer mixture includes at least monomer m1, monomer m2, and monomer m3 as essential components.

Monomer m1 is a component that is the main monomer (main component) constituting the monomer mixture, and includes an alkyl (meth)acrylate represented by the following formula (I), that is, (methyl) of an alkyl alcohol Acrylate. Here, "(meth)acrylic acid" means including acrylic acid and methacrylic acid. In addition, the expression that monomer m1 is the main monomer means that based on the total amount of the monomer mixture, the amount of monomer m1 (in the case of including two or more alkyl (meth)acrylates represented by formula (I) In the case of its total amount) is 50wt% or more.

The monomer m1 may be one or more selected from alkyl (meth)acrylates represented by the following formula (I).

CH ₂ =C(R ¹ )COOR ² (I)

Here, R ¹ in formula (I) is a hydrogen atom or a methyl group. In addition, R ² in formula (I) is an alkyl group having 1 to 20 carbon atoms. The alkyl group can be linear or branched. Specific examples of the alkyl (meth)acrylate represented by the formula (I) include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, iso (meth)acrylate Butyl, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, (meth) Heptyl acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate , Decyl (meth)acrylate, Isodecyl (meth)acrylate, Undecyl (meth)acrylate, Dodecyl (meth)acrylate, Tridecyl (meth)acrylate, (meth)acrylate base) myristyl acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, (meth)acrylate base) nonadecyl acrylate and eicosyl (meth)acrylate. Among them, an alkyl (meth)acrylate in which R is an alkyl group having ² to 14 carbon atoms (this carbon atom range may be referred to as "C _2-14 " hereinafter) is preferred, and more preferred is an alkyl (meth)acrylate in which R ² is an alkyl (meth)acrylate of a C _2-10 alkyl group (such as n-butyl, 2-ethylhexyl, etc.).

In a preferred embodiment, wherein R ² in formula (1) is a C _2-10 (more preferably C _4-8 ) alkyl group, the alkyl (meth)acrylate accounts for more than about 70 wt% of the total amount of monomer m1 (More preferably about 90% by weight or more). Substantially all of the monomer m1 may be C _2-10 alkyl (more preferably C _4-8 alkyl) (meth)acrylate. The monomer mixture may be, for example, a composition including butyl acrylate (BA) alone as the monomer m1, a composition including 2-ethylhexyl acrylate (2EHA) alone as the monomer m1, or a composition including these two kinds of BA and 2EHA as the monomer m1. Composition of monomer m1.

The amount of monomer m1 may be about 50-85 wt% (preferably 60-80 wt%) based on the total amount of the monomer mixture. When the amount of the monomer m1 is less than the above range, the pressure-sensitive adhesive layer formed from the composition tends to have insufficient adhesive properties (adhesiveness, tackiness, etc.). On the other hand, when the amount of the monomer m1 is higher than the above-mentioned range, since the amounts of the monomer m2 and the monomer m3 contained in the monomer mixture decrease, the cohesive force (such as durability against peeling under a certain stress, which is a static load characteristic) and the compatibility between repulsion resistance may deteriorate. Additionally, the composition of the monomer mixture (monomer composition) generally corresponds to that of the acrylic copolymer obtained by polymerization of the monomer mixture (i.e., in a pressure-sensitive adhesive formed from the pressure-sensitive adhesive composition disclosed herein). matrix polymer) copolymerization ratio.

The monomer mixture further includes monomer m2 in addition to monomer m1 as a main monomer. The monomer m2 may be one or more selected from N-hydroxyalkyl (meth)acrylamides represented by the following formula (II).

CH ₂ =C(R ³ )CONHR ⁴ (II)

Here, R ³ in formula (II) is a hydrogen atom or a methyl group. In addition, R ⁴ in formula (II) is a hydroxyalkyl group having 2-4 carbon atoms. The alkyl group in the hydroxyalkyl group can be linear or branched. Specific examples of N-hydroxyalkyl (meth)acrylamide represented by formula (II) include N-(2-hydroxyethyl)acrylamide, N-(2-hydroxyethyl)methacrylamide, N- (2-hydroxypropyl)acrylamide, N-(2-hydroxypropyl)methacrylamide, N-(1-hydroxypropyl)acrylamide, N-(1-hydroxypropyl)methacrylamide, N-(3-hydroxypropyl)acrylamide, N-(3-hydroxypropyl)methacrylamide, N-(2-hydroxybutyl)acrylamide, N-(2-hydroxybutyl)methacrylamide Amide, N-(3-hydroxybutyl)acrylamide, N-(3-hydroxybutyl)methacrylamide, N-(4-hydroxybutyl)acrylamide and N-(4-hydroxybutyl)methacrylamide Acrylamide. From the viewpoint that a pressure-sensitive adhesive layer having a good balance between hydrophilicity and hydrophobicity and a good balance between pressure-sensitive adhesive properties can be formed, preferred examples of the monomer m2 in the present invention include N -(2-hydroxyethyl)acrylamide and N-(2-hydroxyethyl)methacrylamide. In particular, N-(2-hydroxyethyl)acrylamide (HEAA) is preferably used. For example, more than 50wt% (more preferably more than 70wt%, usually substantially all) of the monomer m2 is preferably HEAA.

Monomer m2 may function as a component that helps improve aggregation of the pressure-sensitive adhesive due to interactions between monomer m2 molecules. The amount of monomer m2 may be about 0.1-12 wt % (typically about 1-10 wt %) based on the total amount of the monomer mixture. When the amount of the monomer m2 is less than the above range, the pressure-sensitive adhesive layer formed from the composition has insufficient adhesive properties (adhesiveness at high temperature, durability against peeling under a certain stress, etc.) trend. On the other hand, when the amount of the monomer m2 is higher than the above-mentioned range, there is a tendency that tackiness or cohesiveness decreases at lower temperatures.

In a preferred embodiment of the pressure-sensitive adhesive composition disclosed herein, based on the total amount of the monomer mixture, the amount of monomer m2 is about 2 wt % or more (usually 2-12 wt %), and more preferably about 3 wt % Above (usually about 3-12 wt%, eg about 3-10 wt%). With the adhesive composition, the effect of being able to form a pressure-sensitive adhesive sheet having better cohesive force and repulsion resistance can be obtained.

The weight ratio (m1/m2) of monomer m1 to monomer m2 in the monomer mixture may be, for example, about 99/1-80/20. Generally, the weight ratio is preferably about 98/2-85/15 (more preferably about 97/3-90/10). With the adhesive composition, the effect of being able to form a pressure-sensitive adhesive sheet having better cohesive force and repulsion resistance can be obtained. The total amount of the monomer m1 and the monomer m2 may be, for example, about 60-90 wt%, based on the total amount of the monomer mixture. The total amount thereof is preferably about 70 wt% or more (for example, 70-90 wt%) based on the total amount of the monomer mixture.

In addition to monomers m1 and m2, the monomer mixture further comprises monomer m3. The monomer m3 may be at least one monomer selected from the group consisting of N-vinyl cyclic amides and (meth)acrylamides which may have N-alkyl groups. Specific examples of N-vinyl cyclic amides include N-vinyl-2-pyrrolidone, N-vinyl-2-piperidone, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-1,3-oxadine-2-one and N-vinyl-3,5-morpholinedione. Specific examples of (meth)acrylamides that may have N-alkyl groups include (meth)acrylamides such as N-alkyl(meth)acrylamides; N-ethyl(meth)acrylamides, N-n-butyl and N,N-dialkyl(meth)acrylamide such as N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide , N,N-dipropyl (meth)acrylamide, N,N-diisopropyl (meth)acrylamide, N,N-di(n-butyl)(meth)acrylamide, N,N - Di(tert-butyl)(meth)acrylamide. Preference is given to using (meth)acrylamides (e.g. N,N-dialkylacrylamides such as N, N-diethylacrylamide, N,N-dimethylacrylamide).

As the monomer m3 in the technique disclosed herein, N-vinyl cyclic amides represented by the following formula (III):

wherein ^R is a divalent organic group. R ⁵ in the above formula is preferably a saturated or unsaturated hydrocarbon group, more preferably a saturated hydrocarbon group (for example, an alkylene group having 3-5 carbon atoms). By the monomer mixture having this composition, a pressure-sensitive adhesive composition for forming a pressure-sensitive adhesive layer having a good balance between adhesive properties can be obtained. In the present invention, N-vinyl-2-pyrrolidone is exemplified as a particularly preferred N-vinyl cyclic amide.

The amount of monomer m3 may be, for example, about 10-40 wt%, based on the total amount of the monomer mixture. When the amount of the monomer m3 is higher than the above-mentioned range, the characteristics (adhesion as a pressure-sensitive adhesive, etc.) in a low-temperature environment of the pressure-sensitive adhesive layer formed using the composition may deteriorate. On the other hand, when the amount of the monomer m3 is less than the above-mentioned range, cohesive force (such as peel strength) or repulsion resistance tends to decrease. More suitable results can be achieved by setting the amount of monomer m3 at about 15-35% by weight based on the total monomer mixture.

The total amount of the monomers m1, m2, and m3 may be, for example, about 70 wt% or more based on the total amount of the monomer mixture. The total amount thereof is preferably about 90 wt% or more (more preferably about 95 wt% or more) based on the total amount of the monomer mixture. In preferred embodiments of the pressure sensitive adhesive compositions disclosed herein, the monomer mixture consists essentially only of monomers m1, m2 and m3 (i.e. based on the total amount of monomer mixture, monomers m1, m2 and m3 The total amount is basically 100wt%). With this adhesive composition, the effect that a pressure-sensitive adhesive sheet having good cohesive force and repulsion resistance can be formed can be obtained with a simple composition.

For the techniques disclosed herein, the monomer mixture is substantially free of carboxyl-containing monomers. Here, the "carboxyl group-containing monomer" refers to a vinyl monomer (ethylenically unsaturated monomer) (which may be in the form of an anhydride) having at least one carboxyl group in one molecule thereof. Specific examples of the carboxyl group-containing monomer include ethylenically unsaturated monocarboxylic acids such as (meth)acrylic acid and crotonic acid; ethylenically unsaturated dicarboxylic acids such as maleic acid, itaconic acid and citraconic acid; and ethylenically unsaturated Saturated dicarboxylic anhydrides such as anhydrous maleic acid and anhydrous itaconic acid. In addition, the expression that the monomer mixture "substantially does not include" a carboxyl group-containing monomer means that the monomer mixture does not contain any carboxyl group-containing monomer, or the amount is 0.1 wt% or less based on the total amount of the monomer mixture.

It is preferable that the monomer mixture substantially excludes carboxyl group-containing monomers, and that the monomer mixture substantially exclude acid group-containing (sulfonic acid groups, phosphoric acid groups, etc.) monomers other than carboxyl groups. That is, it is preferred that the monomer does not include acidic group-containing monomers other than carboxyl-containing monomers (this means that monomers do not include carboxyl-containing monomers and additional acidic group-containing monomers) , or based on the total amount of the monomer mixture, the total amount thereof is 0.1 wt% or less. The adhesive composition can form a pressure sensitive adhesive layer that is highly resistant to corrosion of metal surfaces (ie, highly inhibits corrosion on metal surfaces) when it is bonded to a metal surface.

In addition to the monomers m1 to m3, the monomer mixture may contain other monomers (ie, monomers other than the monomers m1 to m3, which may be referred to as "monomer m4" hereinafter) as optional components. point. By using the monomer m4, for example, various properties of the pressure-sensitive adhesive, the structure of the acrylic copolymer, and the like can be more suitably controlled. As the monomer m4, one selected from various monomers that are copolymerizable with the alkyl (meth)acrylate used herein and do not have a carboxyl group (usually a carboxyl group and an acidic group other than a carboxyl group) can be used. or more. For example, various monomers having one or more ethylenically unsaturated groups such as (meth)acryloyl, vinyl and the like can also be used.

Examples of monomer m4 include epoxy group-containing monomers such as glycidyl (meth)acrylate and allyl glycidyl ether; alkoxy group-containing monomers such as methoxyethyl (meth)acrylate, ( Methoxypropyl methacrylate, methoxyethylene glycol (meth)acrylate and methoxypolypropylene glycol (meth)acrylate; cyano-containing monomers such as acrylonitrile and methacrylonitrile; styrenes Monomers such as styrene and α-methylstyrene; α-olefins such as ethylene, propylene, isoprene, butadiene, and isobutylene; monomers containing isocyanate groups such as 2-methacryloyloxyethyl Isocyanates; vinyl ester monomers such as vinyl acetate and vinyl propionate; vinyl ether monomers such as vinyl ether; heterocyclic group-containing (meth)acrylates such as tetrahydrofurfuryl (meth)acrylate ; Halogen-containing monomers such as fluorine (meth)acrylate; Alkoxysilyl-containing monomers such as 3-methacryloxypropyltrimethoxysilane and vinyltrimethoxysilane; Monomers of siloxane bonds such as silicone (meth)acrylate; wherein ^R in the formula (I) is an alkyl (meth)acrylate having an alkyl group with more than 21 carbon atoms; alicyclic (meth)acrylates of aromatic hydrocarbon groups such as cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, bornyl (meth)acrylate and isobornyl (meth)acrylate; and aromatic hydrocarbon-containing (meth)acrylates such as phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate and phenoxydiethylene glycol (meth)acrylate.

Other examples of the monomer m4 include nitrogen atom-containing monomers other than the monomer m2 and the monomer m3. Examples thereof include N-acryloyl-containing cyclic (meth)acrylamides such as N-(meth)acryloylmorpholine and N-acryloylpyrrolidone; amino group-containing monomers such as aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate and N,N-dimethylaminopropyl (meth)acrylate; monomers containing maleimide backbones such as N-cyclohexylmaleic acid imide and N-phenylmaleimide; and itaconimide monomers such as N-methyl itaconimide, N-ethyl itaconimide, N-butyl itaconimide imide, N-2-ethylhexyl itaconimide, N-lauryl itaconimide and N-cyclohexyl itaconimide.

In addition, as the monomer m4, for example, polyfunctional monomers such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, di( Tetraethylene glycol methacrylate, Polyethylene glycol di(meth)acrylate, Polypropylene glycol di(meth)acrylate, Neopentyl glycol di(meth)acrylate, Hexyl di(meth)acrylate Diol ester, pentaerythritol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, epoxy acrylate, Polyester acrylate, urethane acrylate, divinylbenzene, butyl di(meth)acrylate and hexyl di(meth)acrylate.

Other examples of monomer m4 include hydroxyl-containing monomers such as hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, (meth) 3-Hydroxypropyl acrylate, 2-Hydroxybutyl (meth)acrylate, 4-Hydroxybutyl (meth)acrylate, 6-Hydroxyhexyl (meth)acrylate, 8-Hydroxyoctyl (meth)acrylate , (meth)acrylate 10-hydroxydecyl ester, (meth)acrylate 12-hydroxyl dodecyl ester and [4-(hydroxymethyl)cyclohexyl] methacrylate; wherein R in the formula (II) ⁴ is N-hydroxyalkyl (meth)acrylamides having a hydroxyalkyl group of 1 or more carbon atoms; and alkenyl alcohols such as vinyl alcohol and allyl alcohol.

In addition, in the case of using a hydroxyl group-containing monomer as the monomer m4, it is preferable to use a lower ratio of the hydroxyl group-containing monomer than the monomer m2 from the viewpoint that the effect obtained from the use of the monomer m2 can be exhibited more suitably. body m4. In other words, based on the total amount of hydroxyl-containing monomers contained in the monomer mixture, it is preferred that the monomer m2 accounts for more than 50 wt% of the proportion (usually 60 wt% or more of the proportion, more preferably 75 wt% or more, such as 90 wt% or more ). Alternatively, the hydroxyl group-containing monomer contained in the monomer mixture may be substantially only monomer m2.

The amount of the monomer m4 (the total amount when two or more are contained) is suitably about 30% by weight or less based on the total amount of the monomer mixture. When the amount of the monomer m4 is too high, the pressure-sensitive adhesive sheet formed by using the composition may deteriorate the balance between pressure-sensitive adhesive properties. The amount of the monomer m4 is preferably about 10 wt% or less, more preferably about 5 wt% or less (eg, about 2 wt% or less) based on the total amount of the monomer mixture. Alternatively, the monomer mixture may contain substantially no monomer m4 (ie, a monomer mixture containing substantially only monomers m1 to m3).

The monomer mixtures used in the techniques disclosed herein preferably each contain monomers in a proportion such that the acrylic copolymer formed by polymerizing about the entire monomer mixture has a Tg of about -10° C. or less (typically about -10° C. 10°C to -70°C), and more preferably contain monomers respectively in a proportion at which the Tg of the acrylic copolymer obtained by polymerization of the monomer mixture is about -20°C or lower (usually about -20°C to - 70°C). The composition of the monomer mixture may be adjusted so that Tg is within the above range. Here, the Tg of the acrylic copolymer refers to a value determined by the Fox equation based on the Tg of the homopolymer of the monomers constituting the monomer mixture and the weight fraction of the monomers (copolymerization composition). The Tg value of the homopolymer can be obtained from various known materials ("Handbook of Adhesion Technologies" of NIKKAN KOGYO SHIMBUN, LTD., "Polymer Handbook" in Wiley-Interscience, etc.).

A suitable embodiment of the pressure-sensitive adhesive composition disclosed herein is a composition comprising a monomer mixture or a partially polymerized product thereof (in other words, an acrylic copolymer material including unpolymerized monomers) as a main component. For example, it may be a pressure sensitive adhesive composition comprising polymerizable functional groups left unpolymerized in a significant amount (eg, about 50-100 mole percent of the monomer mixture). Such a pressure-sensitive adhesive composition is generally constituted such that by applying the pressure-sensitive adhesive composition on a substrate, release liner, etc. (which may be referred to as a "substrate") described later And by reacting (polymerizing) the polymerizable functional group in the applied composition to cure the composition, a pressure-sensitive adhesive layer (including an acrylic copolymer obtained by polymerization of a monomer mixture as a matrix polymer) can be formed. Curing of the pressure sensitive adhesive composition is preferably carried out while avoiding contact with oxygen, for example under an inert atmosphere such as nitrogen.

The polymerization method (method for curing the composition) in the case of forming a pressure-sensitive adhesive layer with a pressure-sensitive adhesive composition is not particularly limited, but a polymerization method selected from various conventionally known methods can be suitably used any method. For example, any method selected from the following may be used: a polymerization method performed by irradiating active energy rays such as light and radioactive rays (which may hereinafter be referred to as high-energy rays) to the composition; Polymerization method (thermal polymerization method such as solution polymerization method, emulsion polymerization method and block polymerization method) and the like. As an example of a preferable curing method, a method of irradiating active energy rays (for example, light such as ultraviolet rays) can be mentioned. The pressure-sensitive adhesive composition disclosed herein can be cured by irradiating the active energy rays, preferably in the form of a constituted composition. The active energy ray-curable (usually photocurable) adhesive composition is advantageous because it can easily form a thick adhesive layer. In addition, the pressure-sensitive adhesive composition is suitably provided as a liquid composition substantially free of organic solvents (non-solvent type). This is preferable from the viewpoint of environmental friendliness and the like.

The photocurable adhesive composition is usually prepared by using a photopolymerization initiator. For example, it may be in the form of: a pressure-sensitive adhesive composition obtained by mixing a monomer mixture and a photopolymerization initiator, and if necessary, blending with other components; A mixture of agents to form a partial polymerization product of the monomer mixture, and if necessary, a pressure-sensitive adhesive composition obtained by blending the partial polymerization product with other components; by further adding a photopolymerization initiator (post-addition) A pressure-sensitive adhesive composition obtained in a partially polymerized product; a partially polymerized product by forming a monomer mixture in a method other than photopolymerization, and adding a photopolymerization initiator and, if necessary, other components to the partially polymerized product The pressure-sensitive adhesive composition obtained in and the like.

The photopolymerization initiator is not particularly limited, but may be suitably selected from various conventionally known materials in the field of photocurable adhesive compositions. Examples of photopolymerization initiators include ketal photopolymerization initiators, acetophenone photopolymerization initiators, benzoin ether photopolymerization initiators, acylphosphine oxide photopolymerization initiators, α-ketol alcohol photopolymerization Initiators, aromatic sulfonyl chloride-based photopolymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzyl-based photopolymerization initiators, benzophenone-based photopolymerization initiators, and thiazolin-based photopolymerization initiators xanthone-based photopolymerization initiators, etc. These photopolymerization initiators may be used alone or in combination thereof.

Specific examples of the ketal-based photopolymerization initiator include 2,2-dimethoxy-1,2-diphenylethan-1-one [eg, trade name "Irgacure 651" (manufactured by Ciba Japan)]. Specific examples of the acetophenone-based photopolymerization initiator include 1-hydroxycyclohexyl phenyl ketone [for example, trade name "Irgacure 184" (manufactured by Ciba Japan)], 2,2-diethoxyacetophenone, 2 , 2-dimethoxy-2-phenylacetophenone, 4-phenoxydichloroacetophenone and 4-(tert-butyl)dichloroacetophenone. Specific examples of the benzoin ether-based photopolymerization initiator include benzoin methyl ether, benzoin diethyl ether, benzoin propyl ether, benzoin isopropyl ether, and benzoin isobutyl ether. As the acylphosphine oxide-based photopolymerization initiator, trade name "Lucirin TPO" (manufactured by BASF) and the like can be used. Specific examples of the α-keto alcohol-based photopolymerization initiator include 2-methyl-2-hydroxypropiophenone and 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropan-1-one. Specific examples of the aromatic sulfonyl chloride-based photopolymerization initiator include 2-naphthalenesulfonyl chloride. Specific examples of the photoactive oxime-based photopolymerization initiator include 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)oxime. Specific examples of the benzoin-based photopolymerization initiator include benzoin. Specific examples of benzyl-based photopolymerization initiators include benzil. Specific examples of benzophenone-based photopolymerization initiators include benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone and α-hydroxycyclohexyl phenyl ketone. Specific examples of the thioxanthone-based photopolymerization initiator include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2 , 4-diisopropylthioxanthone and dodecylthioxanthone.

The amount of photopolymerization initiator to be used is not particularly limited. For example, the initiator may be used in an amount of about 0.001-5 parts by weight (preferably about 0.01-2 parts by weight, more preferably about 0.01-1 part by weight) based on 100 parts by weight of the total monomer mixture. In addition, the expression of the amount of the photopolymerization initiator to be used herein refers to the total amount of the photopolymerization initiator used in the process for preparing the pressure-sensitive adhesive composition. Therefore, for a pressure-sensitive adhesive composition obtained by post-adding a photopolymerization initiator to a partial polymerization product obtained by irradiating a mixture of a monomer mixture and a photopolymerization initiator with light, it means The total amount of partially aggregated fractions and post-joined fractions.

The polymerization method for forming the partially polymerized product of the monomer mixture is not particularly limited, but may suitably be the same as the polymerization method (curing method) in the case of forming the pressure-sensitive adhesive layer using the pressure-sensitive adhesive composition. Mode Use any method selected from various conventionally known polymerization methods. For example, a mixture (preferably a mixture substantially free of a liquid medium such as an organic solvent, water, etc. (non-solvent type )) photopolymerization method. Formation of a partial polymerized product is preferably performed while avoiding contact with oxygen (for example, under an inert atmosphere such as nitrogen or the like). In addition, a polymerization method in the case of forming a partial polymerization product from a monomer mixture, and a polymerization method in the case of forming a pressure-sensitive adhesive layer from a pressure-sensitive adhesive composition having a partial polymerization product as a main component ( That is, the polymerization method in the case of using the composition to prepare a pressure-sensitive adhesive sheet) may be the same as or different from each other.

In the case where the pressure-sensitive adhesive composition disclosed herein is a composition having a partially polymerized product as a main component (usually a photocurable adhesive composition), the partially polymerized product (preferably wherein the A composition in the state of a slurry (syrup) in which a polymer formed by the polymerization of a mixture and unpolymerized monomers coexist, and the part of the polymerization product having this state and properties may be referred to as a monomer mixture in a "monomer slurry") The conversion rate may be, for example, about 2-40 wt%. Generally, the conversion is preferably about 5-20%. When the conversion rate is too high, the processability of the pressure-sensitive adhesive composition is easily deteriorated. For example, there is a tendency that it is difficult to obtain a composition in the form of substantially no liquid medium (non-solvent type) exhibiting good paintability at normal temperature. On the other hand, when the conversion rate is too low, the properties of the pressure-sensitive adhesive obtained by curing (usually photocuring) the pressure-sensitive adhesive composition tend to be unstable, and in addition, the viscosity of the composition may be too low and cannot be applied.

In addition, the conversion rate of the partial polymerization product was determined in the following method. That is, about 0.5 g of a sample was taken out from the partial polymerization product and weighed (weight: W _p1 ). The sample was then heated to 130° C. for 2 hours to volatilize unpolymerized monomers, and the sample remaining after heating was weighed (weight: W _p2 ). Further, conversion can be determined by applying each obtained value to the following equation:

Conversion rate [%]=(W _p2 /W _p1 )×100

The pressure-sensitive adhesive composition disclosed herein may be, for example, one in which an acrylic copolymer obtained by polymerizing substantially all of the monomer mixture is dissolved or dispersed in a suitable liquid medium (which may be an organic solvent, water, or Compositions in the form of mixtures (solvent type, aqueous solution type, emulsion type, etc.). These forms of pressure-sensitive adhesive compositions are generally constituted such that by applying the pressure-sensitive adhesive composition on a suitable substrate or the like and removing the solvent from the applied product (ie drying the composition) , a pressure-sensitive adhesive layer having an acrylic copolymer as a matrix polymer can be formed. At this time, appropriate crosslinking treatment and the like may be performed, if necessary.

For the pressure-sensitive adhesive composition comprising as a main component an acrylic copolymer (which may be an acrylic copolymer material substantially free of unpolymerized monomer) obtained by polymerizing almost all of the monomer mixture, for The method of polymerizing the monomer mixture is not particularly limited, but various conventionally known polymerization methods may be suitably used in the same manner as in the case of partially polymerizing the monomer mixture. For example, if the acrylic copolymer is formed by, for example, a solution polymerization method, the embodiment of the solution polymerization is not particularly limited, and can be obtained by appropriately using, for example, various known monomer supply methods, polymerization conditions (polymerization temperature, polymerization time, polymerization pressure, etc.), materials to be used (polymerization initiator, surfactant, etc.), are carried out by the same embodiment as conventionally known ordinary solution polymerization. As the monomer feeding method, any method such as an intermittent feeding method for simultaneously feeding the entire amount of the monomer mixture into the reaction vessel, a continuous feeding (dropping) method, or a stepwise feeding (dropping) method, etc. can be used. . In a preferred embodiment, an embodiment is exemplified in which a solution obtained by dissolving the entire amount of a monomer mixture and an initiator in a solvent is prepared in a reaction vessel, and then the monomer mixture is polymerized batchwise (batch polymerization). This batch polymerization is preferred because it facilitates polymerization operation and process control. In another preferred embodiment, it is exemplified in which the initiator is prepared in a reaction vessel (usually a solution obtained by dissolving the initiator in a solvent), and then the monomer mixture is polymerized while the solution dissolved in the solvent is dripped Addition to the reaction vessel (dropwise polymerization or continuous polymerization) embodiment. Usually a portion (some kind and/or partial proportion) of the monomer mixture is put into the reaction vessel together with the solvent, and then the remaining mixture can be added dropwise to the reaction vessel.

Examples of thermal polymerization initiators include azo-based compounds (azo-based initiators) such as 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, dimethyl -2,2'-Azobis(2-methylpropionate), 4,4'-Azobis-4-cyanovaleric acid, Azobisisovaleronitrile, 2,2'-Azobis (2-Amidinopropane) dihydrochloride, 2,2'-Azobis[2-(5-methyl-2-imidazolin-2-yl)propane] dihydrochloride, 2,2'- Azobis(2-methylpropionamidine) disulfate, 2,2'-azobis(N,N'-dimethyleneisobutyramide) dihydrochloride and 2,2'-azobis [N-(2-Carboxyethyl)-2-methylpropionamidine]hydrate; persulfates such as potassium persulfate and ammonium persulfate; peroxides (peroxide-based initiators) such as diphenylmethane peroxide acyl, tert-butyl permaleate, tert-butyl hydroperoxide and hydrogen peroxide; substituted ethane initiators such as phenyl substituted ethane; redox system initiators such as persulfate and sodium bisulfite combination, and a combination of peroxide and sodium ascorbate. In the case of polymerizing the monomer mixture by a thermal polymerization method, a polymerization temperature of, for example, about 20-100°C (usually 40-80°C) can be suitably used.

In a preferred embodiment of the pressure sensitive adhesive composition disclosed herein, the composition comprises a crosslinking agent. By using the crosslinking agent, the pressure-sensitive adhesive layer formed from the composition can have suitable cohesion and adhesive force, and also the repulsion resistance of the pressure-sensitive adhesive layer can be improved. Any crosslinking agent may be suitably selected from various conventionally known materials in the field of pressure-sensitive adhesives. For example, isocyanate-based compounds (isocyanate-based cross-linking agents), epoxy-based cross-linking agents, aziridine-based cross-linking agents, melamine-based cross-linking agents, metal chelate-based cross-linking agents, and metal salt-based cross-linking agents can be used. agent, peroxide crosslinking agent, oxazoline crosslinking agent, urea crosslinking agent, amino crosslinking agent, carbodiimide crosslinking agent, coupling agent crosslinking agent (such as silane coupling joint agent), etc. These crosslinking agents may be used alone or in combination thereof. It may be preferred to blend the crosslinking agent into a form such as a solvent-type adhesive composition in which the acrylic copolymer formed by polymerizing almost all of the monomer mixture is dissolved or dispersed in a suitable liquid medium. composition. Among them, isocyanate-based crosslinking agents are preferably used. In a preferred embodiment, only one or more (usually one) isocyanate crosslinkers are used as crosslinkers. Alternatively, a cross-linking agent other than the isocyanate-based cross-linking agent may be used in combination with the isocyanate-based cross-linking agent within a range that does not significantly affect the effect of the present invention.

Examples of isocyanate compounds include aliphatic polyisocyanates such as 1,6-hexamethylene diisocyanate, 1,4-tetramethylene diisocyanate, 2-methyl-1,5-pentane diisocyanate, 3-methano -1,5-pentane diisocyanate, lysine diisocyanate, etc.; alicyclic polyisocyanates such as isophorone diisocyanate, cyclohexyl diisocyanate, hydrogenated toluene diisocyanate, hydrogenated xylene diisocyanate, hydrogenated diphenyl Methyl methane diisocyanate, hydrogenated tetramethyl xylene diisocyanate, etc.; aromatic polyisocyanate such as 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2, 4'-Diphenylmethane diisocyanate, 4,4'-diphenyl ether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, 2,2'-diphenylpropane-4,4 '-diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, naphthalene-1,4-diisocyanate, naphthalene-1,5-diisocyanate, 3,3'-dimethoxydiphenyl-4,4'-diisocyanate, etc.; araliphatic polyisocyanate such as Xylene-1,4-diisocyanate, xylene-1,3-diisocyanate, etc.

In addition, as the isocyanate crosslinking agent, dimers or trimers, reaction products or polymerization products of the above-exemplified isocyanate compounds (such as dimers or trimers of diphenylmethane diisocyanate, trimers, The reaction product of methylolpropane and toluene diisocyanate, the reaction product of trimethylolpropane and hexamethylene diisocyanate, polymethylene polyphenylisocyanate, polyether polyisocyanate, polyester polyisocyanate) and the like. For example, a reaction product of trimethylolpropane and toluene diisocyanate can be preferably used.

Based on 100 parts by weight of the monomer mixture (which generally corresponds to 100 parts by weight of the acrylic copolymer when the polymerization conversion rate of the monomer mixture in the pressure-sensitive adhesive composition is about 100%), the The amount of the isocyanate-based crosslinking agent may be, for example, about 0.01-20 parts by weight (preferably about 0.01-15 parts by weight). When the amount of the crosslinking agent to be used is too low, it is difficult to exhibit a sufficient effect (effect of improving pressure-sensitive adhesive properties), and when the amount thereof is too high, the balance between adhesive properties is easily disturbed. Usually, about 0.01-1 part by weight (preferably about 0.02-1 part by weight, eg about 0.05-0.5 part by weight) of the isocyanate-based crosslinking agent is suitably used based on 100 parts by weight of the monomer mixture.

In the case where the pressure-sensitive adhesive composition disclosed herein is a composition comprising a monomer mixture or a partial polymerization product thereof as a main component (usually a photocurable adhesive composition), it may be preferable to use a multifunctional (Meth)acrylate (ie, a monomer containing two or more (meth)acryloyl groups in one molecule thereof) acts as a crosslinking agent. For example, one or more selected from the polyfunctional (meth)acrylates exemplified in the description of the monomer m4 may be used. Suitable examples thereof include 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate and 1,2-di(meth)acrylate. - Glycol esters. From the viewpoints of polymerization reactivity (crosslinking reactivity), etc., it is preferable to use polyfunctional acrylate. For a pressure-sensitive adhesive composition having a partially polymerized product of a monomer mixture as a main component, it is preferable to partially polymerize the monomer mixture and then blend (ie, post-add) the multifunctional monomer therewith. In a preferred embodiment, only one or more (usually one) polyfunctional (meth)acrylates are used as crosslinkers. Alternatively, a crosslinking agent other than polyfunctional (meth)acrylate (such as an isocyanate-based crosslinking agent) may be used in combination within a range that does not significantly affect the effect of the present invention.

Based on 100 parts by weight of the monomer mixture, the amount of multifunctional (meth)acrylate used as a crosslinking agent for blending is, for example, about 0.001-5 parts by weight, and usually suitably about 0.005-1 part by weight (for example, about 0.005-0.1 parts by weight). When the amount of the multifunctional (meth)acrylate to be used is too low, a sufficient crosslinking effect is not exhibited, and there is a tendency for cohesion or repulsion resistance to decrease. On the other hand, when the amount of the multifunctional (meth)acrylate to be used is too high, the increase in elasticity of the pressure-sensitive adhesive formed after curing is too high, and adhesion or tackiness may be easily reduce.

In the pressure-sensitive adhesive layer provided on the pressure-sensitive adhesive sheet disclosed herein, the pressure-sensitive adhesive layer preferably includes a pressure-sensitive adhesive having a gel fraction of, for example, about 25 to 75%. In order to form a pressure-sensitive adhesive having such a gel fraction (a cross-linked pressure-sensitive adhesive in a composition including a cross-linking agent), some conditions such as a monomer composition (for example, to be used monomer m2), the degree of polymerization of the monomer mixture in the pressure-sensitive adhesive composition, the molecular weight of the acrylic copolymer, the conditions for forming the pressure-sensitive adhesive layer (drying conditions, light irradiation conditions, etc.), the The type and amount of crosslinking agent, etc. When the gel fraction of the pressure-sensitive adhesive is too low, there is a tendency for insufficient cohesion or repulsion resistance. On the other hand, when the gel fraction thereof is too high, pressure-sensitive adhesive force or stickiness may be easily lowered. Better adhesive performance can be achieved with pressure sensitive adhesives having a gel fraction in the range of about 25-75%, such as about 30-60%.

The "gel fraction of the pressure-sensitive adhesive" used herein refers to a value measured in the following method. The gel fraction can be understood as the weight ratio of ethyl acetate-insoluble components in the pressure-sensitive adhesive.

Methods used to measure gel fraction:

The pressure-sensitive adhesive sample (weight: W _b1 ) is wrapped into a bag with a porous polytetrafluoroethylene film (weight: W _b2 ) with an average pore size of 0.2 μm, and its opening is wrapped with a kite string (weight: W _b3 ) tie on. The bag was immersed in 50 mL of ethyl acetate and left standing at room temperature (typically 23° C.) for 7 days. The bag was then removed, and the ethyl acetate remaining on the outer surface of the bag was wiped off. The bag was dried at 130° C. for 2 hours, and the weight (W _b4 ) of the bag was measured. Determine the gel fraction of a pressure sensitive adhesive by applying each value to the following equation:

Gel fraction [%]=[(W _b4 -W _b2 -W _b3 )/W _b1 ]×100

In addition, it is desirable to use a trade name "NITOFLON (registered trademark) NTF1122" (average pore diameter: 0.2 µm, porosity: 75% and thickness: 85 µm) available from Nitto Denko Corporation or its equivalent as porous polytetrafluoroethylene ( PTFE) film.

The pressure-sensitive adhesive composition disclosed herein may contain various additives commonly used in the field of pressure-sensitive adhesive compositions as optional components. Examples of this optional component include tackifiers (rosin-based resins, petroleum-based resins, terpene-based resins, phenolic resins, ketone-based resins, etc.), plasticizers, softeners, fillers, colorants (pigments, dyes, etc.), antioxidants, labeling reagents, stabilizers and preservatives. These additives can be used by usual methods using conventionally known substances, and do not particularly characterize the present invention. Therefore, a detailed description thereof is omitted here.

In addition, the pressure-sensitive adhesive composition disclosed herein may be suitably blended with polymers other than copolymers formed by polymerization of monomer mixtures for the purpose of adjusting viscosity (generally thickening). The use of a polymer for adjusting viscosity is particularly effective for a pressure-sensitive adhesive composition (usually a photocurable adhesive composition) having a monomer mixture or a partial polymerization product thereof as a main component. Examples of polymers for adjusting viscosity include styrene-butadiene rubber (SBR), isoprene rubber (IR), styrene-butadiene-styrene block copolymer (SBS), ethylene-vinyl acetate copolymer, Acrylic rubber, polyurethane, polyester, etc. In addition, it can be used by making an alkyl (meth)acrylate and a functional monomer (for example, one or more selected from acrylic monomers with functional groups such as acrylamide, acrylonitrile, acryloyl morpholine, acrylic acid, etc.) The acrylic polymer obtained by copolymerization was used as a polymer for adjusting viscosity. It is preferable to use a polymer for adjusting viscosity substantially free of carboxyl groups (more preferably acidic groups other than carboxyl groups).

These polymers for adjusting viscosity may be used alone or in combination, but they are preferably present in an amount of about 40 wt% or less (usually about 5-40 wt%) based on the entire pressure-sensitive adhesive formed from the pressure-sensitive adhesive composition. ) range is used. That is, it is preferable that the proportion of the polymer for adjusting the viscosity is about 40 wt% or less (more preferably about 20 wt% or less) of the pressure-sensitive adhesive-forming components contained in the composition.

The pressure-sensitive adhesive composition disclosed herein is preferably constituted such that about 50% by weight or more (more preferably about 70% by weight or more, such as 90% by weight or more) of an acrylic copolymer obtained by polymerization of a monomer mixture is contained in the composition. In the pressure sensitive adhesive formed by the material. The adhesive composition can form a pressure sensitive adhesive with better adhesive properties.

The pressure-sensitive adhesive sheet according to the present invention includes a pressure-sensitive adhesive layer formed with any one of the pressure-sensitive adhesive compositions disclosed herein. It may be a pressure-sensitive adhesive sheet bonded to a substrate in which the pressure-sensitive adhesive layer is arranged to be fixed to one or both surfaces of a sheet-shaped substrate (support) A pressure-sensitive adhesive sheet in which the pressure-sensitive adhesive layer is separated from a substrate), or a pressure-sensitive adhesive sheet without a substrate in which the pressure-sensitive adhesive layer is provided on a support having release capability such as a release liner (release liner) paper, a resin sheet whose surface is subjected to isolation treatment, etc.). Regarding the concept of the pressure-sensitive adhesive sheet mentioned herein, those called pressure-sensitive adhesive tapes, pressure-sensitive adhesive labels, pressure-sensitive adhesive films and the like are included. In addition, the pressure-sensitive adhesive layer is not limited to those formed continuously, but it may be, for example, an adhesive layer formed in a regular pattern such as dots, stripes, etc. or an irregular pattern.

The pressure-sensitive adhesive sheet disclosed herein may be, for example, a pressure-sensitive adhesive sheet having a cross-sectional structure schematically shown in FIGS. 1-6 . Among them, FIGS. 1 and 2 are examples of the structure of a double-sided pressure-sensitive adhesive type pressure-sensitive adhesive sheet bonded to a substrate. A pressure-sensitive adhesive sheet 11 as shown in FIG. 1 includes pressure-sensitive adhesive layers 2 on both sides of a base material 1, and the pressure-sensitive adhesive layers 2 are each constructed such that they are provided with pressure-sensitive adhesive properties. At least one side of the agent layer is protected by a release liner 3 with a release surface. The pressure-sensitive adhesive sheet 12 shown in FIG. The two sides of the two sides have the protection of the isolation liner 3 of the isolation surface. Such a pressure-sensitive adhesive sheet 12 may be constructed such that if the pressure-sensitive adhesive sheet 12 is rolled up, the pressure-sensitive adhesive layer on the other side contacts the back side of the release liner 3, and the pressure-sensitive adhesive layer on the other side contacts the back side of the release liner 3, and the pressure-sensitive adhesive layer on the other side The sensitive adhesive layer is also protected by a release liner 3 .

3 and 4 are examples of the structure of a pressure-sensitive adhesive sheet without a substrate. The pressure-sensitive adhesive sheet 13 shown in FIG. 3 is constructed in such a way that both sides of the pressure-sensitive adhesive layer 2 without the substrate are covered with a release liner having at least one side of the pressure-sensitive adhesive layer with a release surface. 3 protection. The pressure-sensitive adhesive sheet 14 as shown in FIG. The other side of the pressure-sensitive adhesive layer 2 is in contact with the release liner 3 and the other side is also protected by the release liner 3 .

5 and 6 are examples of the structure of a pressure-sensitive adhesive sheet of a single-sided pressure-sensitive adhesive type bonded to a substrate. The pressure-sensitive adhesive sheet 15 as shown in FIG. At least one side of the pressure-sensitive adhesive layer is protected by a release liner 3 with a release surface. A pressure-sensitive adhesive sheet 16 as shown in FIG. 6 is constructed such that a substrate 1 is provided with a pressure-sensitive adhesive layer 2 on one side. It may be constructed such that the other side of the substrate 1 has a release surface, and if the pressure-sensitive adhesive sheet 16 is wound, the pressure-sensitive adhesive layer 2 is in contact with the other side, and the surface of the pressure-sensitive adhesive layer (Adhesive side) is protected on the other side of the substrate 1 .

The base material constituting the pressure-sensitive adhesive sheet can be appropriately selected and used depending on the application of the pressure-sensitive adhesive sheet, for example, from plastic films such as polypropylene films, ethylene-propylene copolymer films, polyester films, and polyvinyl chloride films. ; foam substrates such as polyurethane foam and polyethylene foam; paper such as kraft paper, crepe paper and Japanese paper; cloth such as cotton and staple fiber; nonwovens such as polyester nonwoven and vinylon nonwoven; metal Foils such as aluminum foil, copper foil and the like. As the plastic film, non-stretched films and stretched (uniaxially stretched or biaxially stretched) films can be used. In addition, the side of the base material on which the pressure-sensitive adhesive layer is provided may be surface-treated with primer application, corona discharge treatment, or the like. The thickness of the substrate can be appropriately selected depending on the purpose, but in general, it is usually about 10 μm to 500 μm (usually 10 μm to 200 μm).

The pressure-sensitive adhesive layer can be preferably placed, for example, by placing any one of the pressure-sensitive adhesive compositions disclosed herein, that is, a pressure-sensitive adhesive composition having a monomer mixture or a partial polymerization product thereof as a main component. (Usually applied on) a support (substrate or release liner), and formed by curing (polymerizing) by irradiating the composition with active energy rays (such as ultraviolet rays). More suitable results can be achieved by this method of forming a pressure-sensitive adhesive layer, for example, from the viewpoint of heat resistance of the pressure-sensitive adhesive layer. In this forming method, an acrylic copolymer obtained by polymerizing a monomer mixture (a matrix polymer in a pressure-sensitive adhesive layer) is synthesized, and the pressure-sensitive adhesive layer is formed at the same time. This method can be preferably applied to an active energy ray-curable adhesive composition prepared by subjecting a monomer mixture (a mixture of unpolymerized monomers) or by subjecting a monomer mixture to a suitable polymerization method such as photopolymerization Method) A partially polymerized product obtained by partially polymerizing with a photopolymerization initiator is blended with a crosslinking agent (polyfunctional (meth)acrylate, etc.) as needed. The active energy ray-curable adhesive composition may be a composition (non-solvent) substantially free of a liquid medium (organic solvent, water, etc.). For the active energy ray-curable adhesive composition in a form including a liquid medium, it is preferable to dry the composition provided on the support and then irradiate it with active energy rays.

In addition, the pressure sensitive adhesive layer can also be formed by placing (typically applying) any of the pressure sensitive adhesive compositions disclosed herein on a support (substrate or release liner) and drying the composition. form. This method for forming a pressure-sensitive adhesive layer can be preferably used for a pressure-sensitive adhesive composition in a form in which almost all of the monomer mixture will be polymerized by a suitable polymerization method (usually a thermal polymerization method) The obtained acrylic copolymer and, if necessary, a crosslinking agent, additives, etc. are dissolved or dispersed in a liquid medium in advance. Where the pressure-sensitive adhesive composition includes a crosslinking agent, appropriate crosslinking may be performed, if desired, in addition to the drying described above.

The pressure-sensitive adhesive composition can be applied using a commonly used applicator such as a gravure roll coater, reverse roll coater, light touch roll coater, dip roll coater, rod coater, knife coater, spray coater, etc. conduct. The pressure-sensitive adhesive composition may preferably be dried under heating from the viewpoint of promoting the crosslinking reaction, improving production efficiency, and the like. The temperature used for drying varies depending on the type of support on which the composition is applied, but a drying temperature of, for example, about 40-150°C can be used.

In addition, in the case of a pressure-sensitive adhesive sheet bonded on a substrate, the pressure-sensitive adhesive composition can be directly placed on the substrate to form a pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer formed on a release liner can be formed. The pressure-sensitive adhesive layer on the substrate is transferred to the substrate.

The thickness of the pressure-sensitive adhesive layer is not particularly limited, but is generally, for example, about 10 μm or more (preferably about 20 μm or more, more preferably about 30 μm or more), whereby good adhesive performance (eg, adhesive strength) can be achieved. In addition, it is generally preferred that the thickness is about 400 μm or less (usually about 200 μm or less, for example about 100 μm or less).

Example

Several embodiments of the present invention are described below, but the present invention is not considered to be limited to these embodiments. Also in the following description, "part" and "%" are based on weight unless otherwise specifically stated.

Example 1

The preparation includes 70 parts of 2-ethylhexyl acrylate (2EHA, Tg of homopolymer: -70°C), 30 parts of N-vinyl-2-pyrrolidone (NVP, Tg of homopolymer: 54°C) and 4 parts 0.05 parts of 2,2-dimethoxy-1,2-diphenylethane- 1-Kone (trade name "Irgacure 651" (manufactured by Ciba Japan)) and 0.05 part of 1-hydroxycyclohexyl phenyl ketone (trade name "Irgacure 184" (manufactured by Ciba Japan)) were used as photopolymerization initiators. Dissolved oxygen was sufficiently removed from the mixture by stirring under a nitrogen atmosphere, and ultraviolet rays were irradiated onto the mixture, thereby obtaining a compound obtained by partial polymerization of a monomer mixture (conversion rate (monomer conversion rate): about 11%). Acrylic copolymer. To this monomer slurry, 0.01 part of 1,6-hexanediol diacrylate (HDDA) was added as an internal crosslinking agent based on 100 parts of the monomer mixture. A photocurable pressure-sensitive adhesive composition according to Example 1 was thus prepared.

Two sheets of release liners (thickness: 38 μm) that had been released with a silicone-based release agent were prepared on the surface of a polyethylene terephthalate (PET) film. The pressure-sensitive adhesive composition described above was applied to the release side (the surface that had been treated with the release agent) of the first release liner. At the same time, the application amount was adjusted so that the finally obtained adhesive layer had a thickness of 50 μm. The applied adhesive composition is then adhered to the release side of a second release liner. The composition was further cured to form a pressure-sensitive adhesive layer by irradiating ultraviolet rays under conditions of a light intensity of about 4 mW/cm ² and a light amount of about 720 mJ/cm ² . Thus, a pressure-sensitive adhesive sheet (release liner-bonded adhesive sheet) was produced, which was constructed such that both sides of the pressure-sensitive adhesive layer were protected by the release liner.

The gel fraction of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to the present example was measured in the following manner according to the method for measuring the gel fraction. That is, a porous PTFE film (trade name "NITOFLON (registered trademark) NTF1122", manufactured by Nitto Denko Corporation) having a size of 100 mm x 100 mm and a kite string having a length of about 100 mm (fineness: 1.5 mm) were prepared, and the weight thereof was measured . Peel off the two release liners from the release liner-bonded pressure-sensitive adhesive sheet with a cut size of ^20cm2 , and wrap the pressure-sensitive adhesive sample into a bag with PTFE film, and wrap its opening with a kite On the line. The weight of the bag was measured, and the weight of the PTFE film (W _b2 ) and the weight of the kite string (W _b3 ) were subtracted from the weight of the bag to determine the weight of the pressure sensitive adhesive sample (W _b1 ). The bag was then immersed in 50 mL of ethyl acetate and left standing at room temperature (typically 23° C.) for 7 days. The bag was then removed from the ethyl acetate, and any ethyl acetate remaining on the outer surface of the bag was wiped off. The bag was dried in a dryer at 130° C. for 2 hours, and then the weight (W _b4 ) of the bag was measured. The gel fraction of the pressure sensitive adhesive determined by applying each value to the equation as previously described was 49.9%.

Example 2-5

Except using the monomer mixture of the composition shown in Table 1 (in the table, "AA" represents acrylic acid; Tg of the homopolymer: 106°C) and the amount of HDDA to be added is 0.02 parts and 0.02 parts in Example 3, respectively. Except for 0.04 parts in Example 5, a pressure-sensitive adhesive composition was prepared in the same manner as in Example 1, and a pressure-sensitive adhesive sheet was prepared based on 100 parts of the monomer mixture. The gel fractions of the pressure-sensitive adhesives measured in the same manner as in Example 1 were 48% in Example 2, 68.1% in Example 3, 81.9% in Example 4, and 81.9% in Example 4, respectively. In Example 5, it was 60%.

For the pressure-sensitive adhesive sheets prepared in Examples 1 to 5 provided with the pressure-sensitive adhesive layer formed from the ultraviolet curable adhesive composition, the following evaluation tests were performed.

Corrosive:

One side of the release liner was peeled off from the pressure-sensitive adhesive sheet according to each example to expose one side of the pressure-sensitive adhesive layer, and a transparent PET film (which was not subjected to release treatment) having a thickness of 25 μm was bonded and supported body on it. In addition, the release liner on the other side was peeled off to expose the other side of the pressure-sensitive adhesive layer, and it was pasted and combined with a copper foil having a thickness of 80 μm, and then kept under an atmosphere of 60° C.×95% RH 250 hours. Then, the copper foil surface of the portion stuck to the pressure-sensitive adhesive sheet was visually observed on the side of the PET film, and the presence or absence of copper foil surface corrosion was confirmed using the color change of the copper foil surface as an index. As a result, the case where no color change on the surface of the copper foil was confirmed was expressed as "absence" of corrosivity, and the case where the color change of the surface of the copper foil was confirmed was expressed as "presence" of corrosivity.

Adhesion:

One side of the release liner was peeled off from the pressure-sensitive adhesive sheet according to each example to expose one side of the pressure-sensitive adhesive layer, and a PET film (which was not subjected to release treatment) having a thickness of 50 μm was bonded and supported on on it. The supported pressure-sensitive adhesive sheet was cut to a width of 25 mm to prepare test pieces. As an object to be bonded, a clean acrylic plate obtained by reciprocating rubbing and washing 10 times with clean waste dipped in isopropyl alcohol was used. The release liner on the other side was peeled off from the test piece and pressed onto the object to be bonded with a 5 kg roller once. After storing it at 40°C for 2 days, it was taken out under the measurement environment of 23°C×50%RH, kept standing for 30 minutes, and tested at a tensile speed of 300mm/min and a peeling angle of 180° using a tensile tester. Peel strength (N/25mm) was measured under conditions.

Anti-repulsion:

The pressure-sensitive adhesive sheet according to each example was cut into a size of 10 mm wide and 90 mm long, and the release liner was peeled from one side. Then, an aluminum plate having the same size (thickness: 0.5 mm) was bonded and combined therewith to prepare a test piece. The test piece is longitudinally along the The 50mm line is bent (that is, the curvature of R50), and the aluminum plate should not face inward. Then, the release liner was peeled off from the other side of the test piece, and pressed using a laminator on the surface of the polypropylene plate cleaned in the same manner as above so that no floating occurred. It was left to stand in an environment of 23° C. for 4 hours or 7 hours, and then the flying height (mm) of the edge of the test piece in the longitudinal direction on the surface of the polypropylene plate was measured. Measurements are made at both ends of the test piece, and the total fly height value at both ends is taken as the repulsion resistance value.

Retentivity:

As an index of cohesive force, the holding force (static load characteristic) of the pressure-sensitive adhesive sheet according to each example was evaluated in the following manner. That is, the release liner on one side was peeled from the pressure-sensitive adhesive sheet to expose one side of the pressure-sensitive adhesive layer, and a PET film (which was not subjected to release treatment) having a thickness of 50 μm was bonded and supported thereon . The supported adhesive sheet was cut into a size of 10 mm wide and 50 mm long to prepare test pieces. As an object to be bonded, a clean Bakelite board cleaned by reciprocating rubbing 10 times with clean waste soaked in toluene was used. The release liner on the other side was peeled off from the test piece and pressed against the object to be bonded by reciprocating rolling with a 2 kg roller over a contact area of 10 mm wide and 20 mm long. After keeping it at 40°C for 30 minutes, the bakelite board was removed in an environment of 40°C, and after a load of 500 g was applied to the free end of the test piece (the protruding portion of the bakelite board), it was allowed to cool in an environment of 40°C. Let stand for 2 hours. The case where the test piece fell from the bonded object after imparting the load and before the subsequent 2 hours was indicated as "poor" retention, while the case where the test piece remained on the bonded object even after the lapse of 2 hours was indicated as Expressed as "good" retention.

The results of the evaluation tests are shown in Table 1. In this table, the composition of the monomer mixture used to prepare the pressure-sensitive adhesive composition according to each example (the kind and amount ratio of the monomers to be used) together with Tg determined from the composition based on the Fox equation Shows.

Table 1

As shown in Table 1, compared with the pressure-sensitive adhesive sheet (Example 3) in the present invention having a copolymer composition including monomer m1 (2EHA) and monomer m3 (NVP) and excluding monomer m2, According to the pressure-sensitive adhesive sheets (Examples 1 and 2) having a copolymerized composition including the monomer m2 (here, HEAA) in addition to the monomers m1 and m3, repulsion resistance was significantly improved while other characteristics remained comparable. Therefore, with the pressure-sensitive adhesive sheets of Examples 1 and 2, compared with the pressure-sensitive adhesive sheet of Example 5 obtained by using a carboxyl group-containing monomer (here, AA) of a general adhesive composition, it is possible to Achieve equivalent or higher levels of repellency resistance and peel strength. In addition, the pressure-sensitive adhesive sheet according to Example 4 having an excessively high amount of monomer m3 was insufficient in balance between adhesive properties. In addition, the pressure-sensitive adhesive sheets according to Examples 1-4 were not corrosive on metal surfaces, and also had sufficient holding power. On the other hand, it was confirmed that the pressure-sensitive adhesive sheet of Example 5 obtained by using AA exhibited better adhesive properties than the pressure-sensitive adhesive sheet according to Example 3, but corroded the metal surface.

Examples 6 and 7

Except using a monomer mixture of the composition shown in Table 2 (in this table, "BA" means butyl acrylate; Tg of homopolymer: -54°C) and for Example 6 or 7, based on 100 parts of monomer A pressure-sensitive adhesive composition was prepared in the same manner as in Example 1 except that the amount of HDDA to be added to the body mixture was 0.03 part, and a pressure-sensitive adhesive sheet was prepared using the composition. The gel fractions of the pressure-sensitive adhesives were 28.7% in Example 6 and 53% in Example 7, respectively.

Examples 8 and 9

Except using the monomer mixture of the composition shown in Table 2 (in this table, "DEAA" represents N,N-diethylacrylamide; Tg of homopolymer: 81°C) and based on 100 parts of the monomer mixture, Except that the amounts of HDDA added were 0.05 parts in Example 8 and 0.06 parts in Example 9, a pressure-sensitive adhesive composition was prepared in the same manner as in Example 1, and using this composition, Pressure sensitive adhesive sheet. The gel fractions of the pressure-sensitive adhesives were 30.2% in Example 8 and 19.7% in Example 9, respectively.

The above-mentioned evaluation tests were performed on the pressure-sensitive adhesive sheets prepared in Examples 6-9 provided with an adhesive layer formed of an ultraviolet-curable type adhesive composition. The results are shown in Table 2.

Table 2

From the comparison between Examples 6 and 7, it can be seen that the pressure-sensitive adhesive sheet composed of a copolymer including monomer m1 (BA) and monomer m3 (NVP) and excluding monomer m2 in the present invention (Example 7) Compared to the pressure-sensitive adhesive sheet (Example 6) composed of the copolymerization composed by substituting monomer m2 (here HEAA) for a part of NVP, repulsion resistance was significantly improved while other characteristics remained comparable. From the comparison between Examples 8 and 9, it can be seen that the pressure-sensitive adhesive sheet composed of the copolymer including monomer m1 (2EHA) and monomer m3 (DEAA) and excluding monomer m2 in the present invention (Example 9) Compared with the pressure-sensitive adhesive sheet (Example 8) composed of the copolymerization composed by substituting a part of DEAA with HEAA, the repulsion resistance and holding force were significantly improved, while the peel strength remained comparable. In addition, all the pressure-sensitive adhesive sheets of Examples 6-9 were not corrosive on metal surfaces.

Example 10

Put 0.2 parts of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator, 70 parts of 2EHA, 26 parts of NVP and 4 A portion of HEAA was used as the monomer mixture, and ethyl acetate was used as the solvent, followed by stirring at room temperature under a nitrogen atmosphere for 1 hour. Thereafter, the contents of the reaction vessel (solution containing the entire amount of the monomer mixture) were heated to 60° C., and polymerized in a nitrogen stream for 5.5 hours. By this batch-feed type solution polymerization, an acrylic polymer solution is obtained.

To the obtained acrylic polymer solution were added trimethylolpropane as an isocyanate crosslinking agent and A reaction product of toluene diisocyanate (use the trade name "CORONATE L", produced by NIPPON POLYURETHANEINDUSTRY CO., LTD.). A pressure-sensitive adhesive composition according to Example 10 was thus prepared.

Two sheets of release liners (thickness: 38 μm) that had been released with a silicone-based release agent were prepared on the surface of a polyethylene terephthalate (PET) film. The above-mentioned adhesive composition is applied on the release surface of the first release liner (the surface treated with the release agent) with an applicator, dried at 130° C. for 3 minutes, and formed on the release liner with a thickness of 50 μm. thickness of the pressure sensitive adhesive layer. The pressure sensitive adhesive layer is then combined with the release side of a second release liner. Thus, a pressure-sensitive adhesive sheet (release liner-bonded pressure-sensitive adhesive sheet) was constructed such that a double-sided pressure-sensitive adhesive layer protected by a release liner was produced. The gel fraction of the pressure-sensitive adhesive measured in the same manner as in Example 1 was 49.2%.

Example 11

Except using monomer mixtures of the composition shown in Table 3 (in this table, "HEA" stands for hydroxyethyl acrylate) and based on 100 parts of acrylic polymer, the amount of isocyanate crosslinking agent to be added is 0.1 part Also, a pressure-sensitive adhesive composition was prepared in the same manner as in Example 10, and a pressure-sensitive adhesive sheet was prepared using the composition. The gel fraction of the pressure sensitive adhesive was 59.4%.

Example 12

In addition to using a monomer mixture of the composition shown in Table 3 (in this table, "CHMI" stands for N-cyclohexylmaleimide) and based on 100 parts of acrylic polymer, the amount of isocyanate crosslinking agent to be added Except that the amount was 0.5 parts, a pressure-sensitive adhesive composition was prepared in the same manner as in Example 10, and a pressure-sensitive adhesive sheet was prepared using the composition. The gel fraction of the pressure sensitive adhesive was 53.4%.

The evaluation test as described above was performed on the pressure-sensitive adhesive sheets prepared in Examples 9-12 provided with the adhesive layer formed of the solvent-based adhesive composition. The results are shown in Table 3.

table 3

As shown in Table 3, according to the pressure-sensitive adhesive sheet having a copolymer composition in which HEAA (Example 10) was replaced by an equivalent amount of HEAA (Example 10) in the monomer mixture, the repulsion resistance (total floating height) was further improved. values are reduced) while other properties remain at least comparable. In addition, the effect of improving the adhesive performance was similarly seen by the pressure-sensitive adhesive sheet having a copolymer composition in which HEAA (Example 10) was replaced in the monomer mixture in an equivalent amount of CHMI (Example 12). In addition, all the pressure-sensitive adhesive sheets according to Examples 10-12 were not corrosive on metal surfaces, and exhibited sufficient holding power.

As indicated above, specific embodiments of the present invention have been described in detail, and these are for the purpose of illustration only, and do not limit the scope of the claims. The technology described in the scope of the claims includes various modifications and changes of the specific embodiments described above.

Although the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope thereof.

This application is based on Japanese patent applications (Patent Application No. 2008-135518 filed on May 23, 2008 and Patent Application No. 2008-198269 filed on July 31, 2008), the entire contents of which are incorporated herein as refer to.

As described above, the pressure-sensitive adhesive sheet provided with the pressure-sensitive adhesive layer formed by using the pressure-sensitive adhesive composition of the present invention exhibits good adhesive properties (repellency resistance, static load characteristics) at normal temperature. etc.), which, in addition to electronic components, can preferably be used, for example, for the fixing of articles with metal surfaces, as an adhesive material with inhibited corrosion properties on metal surfaces. The pressure-sensitive adhesive sheet can preferably be used in other applications in embodiments for direct application on metal surfaces, for example for applications such as transportation, protection, decoration, etc. of articles having metal surfaces, producing the properties of advantage. The pressure-sensitive adhesive composition of the present invention is suitable as a pressure-sensitive adhesive for a pressure-sensitive adhesive sheet to be bonded to a metal surface (usually used to form a pressure-sensitive adhesive layer of a pressure-sensitive adhesive sheet) agent composition. In addition, the pressure-sensitive adhesive sheet provided by the present invention can be suitably used in other application embodiments, not limited to the embodiment directly bonded on a metal surface, because it exhibits good adhesive performance at normal temperature as described above .

Claims (8)

1. A pressure-sensitive adhesive composition comprising a monomer mixture or an acrylic copolymer material obtained by at least partially polymerizing the monomer mixture as a main component, The monomer mixture comprises: Based on the total amount of the monomer mixture, the amount is 50-85% by weight of at least one monomer selected from alkyl (meth)acrylates represented by the following formula (I) (monomer m 1): CH ₂ =C(R ¹ )COOR ² (I) wherein R ¹ is a hydrogen atom or a methyl group, and R ² is an alkyl group having 1-20 carbon atoms, At least one monomer selected from N-hydroxyalkyl (meth)acrylamides represented by the following formula (II) in an amount of 0.1 to 12% by weight based on the total amount of the monomer mixture (monomer m2): CH ₂ =C(R ³ )CONHR ⁴ (II) wherein R ³ is a hydrogen atom or a methyl group, and R ⁴ is a hydroxyalkyl group with 2-4 carbon atoms, and Based on the total amount of the monomer mixture, the amount is 10-40% by weight of at least one monomer selected from N-vinyl cyclic amides and (meth)acrylamides that may have N-alkyl groups (monomer m3); and The monomer mixture is substantially free of carboxyl group-containing monomers. 2. The composition according to claim 1, wherein based on the total amount of the monomer mixture, monomer m1, monomer m2 and monomer m3 are included in a total amount of more than 90 wt%. 3. The composition according to claim 1, wherein the monomer mixture has a monomer such that an acrylic copolymer obtained by polymerizing the monomer mixture has a glass transition temperature (Tg) of -10°C or lower composition. 4. The composition of claim 1, wherein the monomer m2 is N-(2-hydroxyethyl)(meth)acrylamide. 5. The composition according to claim 1, wherein the monomer m3 is at least one monomer selected from N-vinyl cyclic amides represented by the following formula (III): wherein ^R is a divalent organic group. 6. The composition according to claim 1, which is used for a pressure-sensitive adhesive sheet directly bonded on a metal surface. 7. A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed by using the composition according to claim 1. 8. A method of producing a pressure-sensitive adhesive sheet, the method comprising: preparing a pressure-sensitive adhesive composition comprising a monomer mixture or an acrylic copolymer material obtained by partially polymerizing the monomer mixture, and 0.01 to 2 parts by weight of a photopolymerization initiator based on 100 parts by weight of the monomer mixture, The monomer mixture comprises: At least one monomer selected from alkyl (meth)acrylates represented by the following formula (I) in an amount of 50 to 85% by weight based on the total amount of the monomer mixture (monomer m1): CH ₂ =C(R ¹ )COOR ² (I) wherein R ¹ is a hydrogen atom or a methyl group, and R ² is an alkyl group having 1-20 carbon atoms, At least one monomer selected from N-hydroxyalkyl (meth)acrylamides represented by the following formula (II) in an amount of 0.1 to 12% by weight based on the total amount of the monomer mixture (monomer m2): CH ₂ =C(R ³ )CONHR ⁴ (II) wherein R ³ is a hydrogen atom or a methyl group, and R ⁴ is a hydroxyalkyl group with 2-4 carbon atoms, and Based on the total amount of the monomer mixture, the amount is 10-40% by weight of at least one monomer selected from N-vinyl cyclic amides and (meth)acrylamides that may have N-alkyl groups (monomer m3), and The monomer mixture is substantially free of carboxyl-containing monomers; applying the pressure sensitive adhesive composition on a support; and The applied composition is cured by irradiating the applied composition with light, thereby forming a pressure-sensitive adhesive layer.

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