Protective film and adhesive composition

Abstract

To provide a protective film and an adhesive composition.SOLUTION: An adhesive composition comprises an acrylic acid block copolymer, a crosslinking agent, and a catalyst. With respect to 100 pts.wt. of the acrylic acid block copolymer, the content of the crosslinking agent is 1 to 10 pts.wt., and the content of the catalyst is 0.001 to 0.05 pt.wt.. The acrylic acid block copolymer is formed by a two-stage free radical polymerization using a methacrylic acid monomer, an acrylic acid monomer, and a hydroxyl-containing monomer. The glass transition temperature of the homopolymer polymerized from the methacrylic acid monomer is higher than that of the homopolymer polymerized from the acrylic acid monomer. The acrylic acid block copolymer contains an A block and a B block.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a protective film and adhesive composition, and more particularly to a protective film and adhesive composition used for a solder mask in the exposure process of a printed circuit board. [Background technology]

[0002] The manufacturing process of a printed circuit board involves multiple steps to create a precise laminate structure on the substrate. Because of the complex structure, the manufacturing of a printed circuit board is time-consuming. To keep the surface of the board clean and free of foreign matter during the manufacturing process, a transparent protective film can be applied to the surface.

[0003] The transparent protective film has a certain adhesive strength, and in the solder mask process, it is attached to the surface of a substrate coated with a solder mask and directly exposed to light, and can be peeled off before development. Therefore, to facilitate the exposure process, the protective film needs to have good light transmittance, be easily peeled off, and not leave any adhesive residue.

[0004] In practice, the protective film is generally applied flat to the printed circuit board after the solder mask has been applied and dried by hot pressing at a temperature of 50 to 80°C. After the exposure process, the protective film is manually peeled off and the development process continues.

[0005] Common protective films use polyacrylic resin as the adhesive layer, and the peel resistance of the protective film increases as the peel speed increases. Therefore, the faster the protective film is peeled off, the greater the peel resistance of the protective film. Partially exposed and hardened solder mask may peel off along with the protective film, or problems such as denting the printed circuit board may occur.

[0006] Therefore, it is an important task for the present business operator to overcome the above-mentioned drawbacks by appropriately reducing the peel resistance of the protective film through improvement of the components, while maintaining the original bonding effect. Summary of the Invention [Problem to be solved by the invention]

[0007] The technical problem that the present invention aims to solve is to provide a protective film and adhesive composition that addresses the shortcomings of the prior art. [Means for solving the problem]

[0008] To solve the above technical problems, one of the technical solutions adopted by the present invention provides an adhesive composition. The adhesive composition includes an acrylic acid block copolymer, a crosslinker, and a catalyst. The content of the crosslinker is 1 to 10 parts by weight, and the content of the catalyst is 0.001 to 0.05 parts by weight, relative to 100 parts by weight of the acrylic acid block copolymer. The acrylic acid block copolymer is formed by two-stage free radical polymerization using a methacrylic acid monomer, an acrylic acid monomer, and a hydroxyl group-containing monomer. The glass transition temperature of the homopolymer polymerized with the methacrylic acid monomer is higher than the glass transition temperature of the homopolymer polymerized with the acrylic acid monomer. The acrylic acid block copolymer includes an A block and a B block, and the content of the methacrylic acid monomer in the A block is lower than the content of the methacrylic acid monomer in the B block, and the content of the acrylic acid monomer in the A block is higher than the content of the acrylic acid monomer in the B block.

[0009] In one embodiment, the glass transition temperature of the A block is from -40°C to -10°C.

[0010] In one embodiment, the glass transition temperature of the B block is from 10°C to 25°C.

[0011] In one embodiment, the content of the A block is 10% by weight to 20% by weight, and the content of the B block is 80% by weight to 90% by weight, where the total weight of the acrylic acid block copolymer is 100% by weight.

[0012] In one embodiment, the glass transition temperature of the homopolymer obtained by polymerizing methacrylic acid monomers is 15°C to 115°C, and the glass transition temperature of the homopolymer obtained by polymerizing acrylic acid monomers is -70°C to 10°C.

[0013] In some embodiments, the methacrylic acid monomer is selected from the group consisting of methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, glycidyl methacrylate, tert-butyl methacrylate, cyclohexyl methacrylate, and isobornyl methacrylate.

[0014] In some embodiments, the acrylic acid monomer is selected from the group consisting of methyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate, and n-butyl acrylate.

[0015] In some embodiments, the hydroxyl-containing monomer is selected from the group consisting of 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate.

[0016] In one embodiment, the A block is composed of 5% to 15% by weight of methacrylic acid monomers, 75% to 90% by weight of acrylic acid monomers, and 5% to 10% by weight of hydroxyl group-containing monomers.

[0017] In one embodiment, the B block is composed of 25% to 35% by weight of methacrylic acid monomers, 45% to 70% by weight of acrylic acid monomers, and 5% to 10% by weight of hydroxyl group-containing monomers.

[0018] In one embodiment, the number average molecular weight of the acrylic acid block copolymer is from 300,000 g / mol to 500,000 g / mol.

[0019] In one embodiment, the acrylic acid block copolymer has a polymer dispersity index (PDI) of 1.5-5.

[0020] Another technical solution adopted by the present invention to solve the above technical problems is to provide a protective film. The protective film includes a substrate layer, an adhesive layer, and a release layer. The adhesive layer is disposed between the substrate layer and the release layer. The adhesive layer is formed from the adhesive composition.

[0021] In one embodiment, the adhesive layer has a thickness of 2 μm to 20 μm.

[0022] In one embodiment, at a peeling temperature of 25°C, the resistance when the protective film is peeled at a speed of 0.3 m / min is greater than the resistance when the peeling speed is 2.4 m / min. [Effects of the Invention]

[0023] One of the advantageous effects of the present invention is that the protective film and adhesive composition of the present invention have the technical features that "the adhesive composition comprises an acrylic acid block copolymer, and the acrylic acid block copolymer comprises an A block and a B block" and "the glass transition temperature of the A block is lower than the glass transition temperature of the B block," allowing the protective film to have good adhesive strength and be quickly and easily peeled off. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a schematic side view of a protective film according to the present invention. [Figure 2] 1 is a schematic view showing a first state of use of a protective film according to the present invention. [Figure 3] FIG. 3 is a schematic view showing a second state of use of the protective film according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] To better understand the features and technical contents of the present invention, please refer to the following detailed description of the present invention and the accompanying drawings, which are provided for reference and explanation only and do not limit the scope of the present invention.

[0026] The following describes the implementation of the "protective film and adhesive composition" according to certain specific embodiments, and those skilled in the art can understand the advantages and effects of the present invention based on the content disclosed herein. The present invention can be implemented or applied in other different specific embodiments, and various modifications and changes can be made to the details herein based on different perspectives and applications without departing from the concept of the present invention. It should be noted in advance that the accompanying drawings of the present invention are for simple schematic illustrations and are not drawn to scale. The technical content of the present invention will be described in more detail based on the following implementations, but the disclosed content does not limit the scope of protection of the present invention. Furthermore, the term "or" used in this specification may include any one or more combinations of the related listed items depending on the actual situation.

[0027] To solve the problems of solder mask peeling and printed circuit board dents when the protective film is peeled off, the present invention provides a protective film having an adhesive layer formed from an adhesive composition. The adhesive layer formed from the adhesive composition has good adhesive strength, can be attached to the surface of a printed circuit board, and has relatively low peel resistance when the protective film is peeled off at high speed, making it easy to remove the protective film.

[0028] As shown in FIG. 1, the protective film of the present invention includes a base layer 1, an adhesive layer 2, and a release layer 3, and the adhesive layer 2 is disposed between the base layer 1 and the release layer 3.

[0029] In one exemplary embodiment, the thickness of the base layer 1 is 10 μm to 50 μm, the thickness of the adhesive layer 2 is 2 μm to 20 μm, and the thickness of the release layer 3 is 10 μm to 50 μm, but the present invention is not limited to these. Experiments have shown that when the thickness of the adhesive layer 2 is 2 μm to 20 μm, a balance is achieved between the adhesion effect and peel resistance of the protective film, making it convenient to use.

[0030] In another exemplary embodiment, the main materials of the base layer 1 and the release layer 3 are both polyethylene terephthalate (PET), and the difference between the material of the base layer 1 and the material of the release layer 3 is that a release agent is applied to the surface of the release layer 3, so that it can be easily separated from the base layer 1.

[0031] As shown in Figures 2 and 3, when using the protective film, the release layer 3 is peeled off first (Figure 2). Next, the adhesive layer 2 is brought into contact with a printed circuit board P (Figure 3) coated with a solder mask S (also called solder resist), and the protective film is hot-pressed at a temperature of 60°C using a roller. In this way, by providing the protective film, it is possible to prevent foreign matter from adhering to the surface of the printed circuit board P, thereby achieving a protective effect.

[0032] Because the protective film is light-transmitting, it can be covered with a photomask and then directly exposed to light to pattern the solder mask S. After the process is complete, the protective film can be directly peeled off to allow other processes, such as a development process, to continue on the printed circuit board P. However, the above description is merely an explanation of the method of using the protective film according to the present invention, and the present invention is not limited thereto.

[0033] The present invention provides an adhesive composition for forming an adhesive layer in a protective film, which provides good adhesion to the protective film and has relatively low peel resistance when peeled at a high speed (2.4 m / min), the specific peel resistance value being as described below.

[0034] The adhesive composition according to the present invention comprises an acrylic acid block copolymer, a crosslinking agent, a solvent, and a catalyst, and may optionally contain a plasticizer. During the process of forming an adhesive layer using the adhesive composition, the solvent may dissipate. Therefore, the adhesive layer material may comprise the acrylic acid block copolymer, an initiator, and a catalyst, or may further comprise the plasticizer.

[0035] In the adhesive composition, the acrylic acid block copolymer is the main solid content, and the content of the crosslinking agent is 1 to 10 parts by weight, the content of the catalyst is 0.001 to 0.05 parts by weight, the content of the solvent is 50 to 90 parts by weight, and the content of the plasticizer is 0.1 to 5 parts by weight, relative to 100 parts by weight of the acrylic acid block copolymer.

[0036] The acrylic acid block copolymer is obtained by copolymerizing a methacrylic acid monomer, an acrylic acid monomer, and a hydroxyl group-containing monomer, with the hydroxyl group-containing monomer being bonded between the methacrylic acid monomer and the acrylic acid monomer.

[0037] In one exemplary embodiment, the number average molecular weight of the acrylic acid block copolymer is 300,000 g / mol to 500,000 g / mol, for example, 325,000 g / mol, 350,000 g / mol, 375,000 g / mol, 400,000 g / mol, 425,000 g / mol, 450,000 g / mol, or 475,000 g / mol. The polymer dispersity index (PDI) of the acrylic acid block copolymer is 1.5 to 5, for example, 2, 2.5, 3, 3.5, 4, or 4.5. Controlling the molecular weight and polymer dispersity index of the acrylic acid block copolymer within the above ranges imparts low resistance to high-speed peeling to the adhesive layer obtained by curing the adhesive layer composition.

[0038] It is worth noting that the acrylic acid block copolymer of the present invention is copolymerized by free radical two-stage polymerization, and by controlling the ratio of acrylic acid monomers, the acrylic acid block copolymer has an A block and a B block.

[0039] The difference between the A block and the B block is that they have different glass transition temperatures, and the glass transition temperature of the A block is lower than the glass transition temperature of the B block. Specifically, the glass transition temperature of the A block is −40° C. to −10° C., and the glass transition temperature of the B block is 10° C. to 25° C.

[0040] Additionally, the glass transition temperatures of the A and B blocks can be calculated according to the FOX equation. In the FOX equation, Tg is the glass transition temperature of the block polymer, and W1, W2, W3, ... and W n is the weight percent of each monomer, and Tg1, Tg2, Tg3, ... and Tgn are the glass transition temperatures of the homopolymer after polymerizing each monomer.

number

[0041] The A block and B block each play an important role in the bonding effect and peel resistance of the adhesive layer. The A block, which has a relatively low glass transition temperature, provides the adhesive layer with good bonding effect, while the B block, which has a relatively high glass transition temperature, provides the adhesive layer with relatively low peel resistance. In this way, the drawback of commercially available protective films, such as difficulty in peeling at high speeds, can be overcome.

[0042] In a preferred embodiment, the A block content is 10 to 20% by weight, and the B block content is 80 to 90% by weight, where the total weight of the acrylic acid block copolymer is 100% by weight. Specifically, the A block content may be 12, 14, 16, or 18% by weight, and the B block content may be 82, 84, 86, or 88% by weight. Within this content ratio range, an adhesive layer formed from the adhesive composition exhibits the property of being relatively easy to peel.

[0043] The A block and the B block are composed of the same or different types of monomers, and by adjusting the content of the monomers, different properties can be imparted to the A block and the B block.

[0044] In a preferred embodiment, the A block and the B block are composed of the same monomers. That is, both the A block and the B block are composed of the methacrylic acid monomer, the acrylic acid monomer, and the hydroxyl group-containing monomer. The A block and the B block differ in the amount of the methacrylic acid monomer and the acrylic acid monomer.

[0045] By adjusting the content ratio of methacrylic acid monomer to acrylic acid monomer, the A block and the B block have different glass transition temperatures, where the content of methacrylic acid monomer in the A block is less than the content of methacrylic acid monomer in the B block, and the content of acrylic acid monomer in the A block is more than the content of acrylic acid monomer in the B block.

[0046] Specifically, the A block contains 5 to 15% by weight of methacrylic acid monomers, 75 to 90% by weight of acrylic acid monomers, and 5 to 10% by weight of hydroxyl group-containing monomers, while the B block contains 25 to 35% by weight of methacrylic acid monomers, 45 to 70% by weight of acrylic acid monomers, and 5 to 10% by weight of hydroxyl group-containing monomers.

[0047] In addition to the structural differences between methacrylic acid monomers and acrylic acid monomers, homopolymers obtained by polymerizing methacrylic acid monomers and acrylic acid monomers also have different glass transition temperatures, with the glass transition temperature of the homopolymer obtained by polymerizing methacrylic acid monomers being higher than the glass transition temperature of the homopolymer obtained by polymerizing acrylic acid monomers. Specifically, the glass transition temperature of the homopolymer obtained by polymerizing methacrylic acid monomers is 15°C to 115°C, and the glass transition temperature of the homopolymer obtained by polymerizing acrylic acid monomers is -70°C to 10°C.

[0048] The methacrylic acid monomer can be represented by the general formula CH2=C(CH3)COOR2, where R2 is an alkyl group having 1 to 10 carbon atoms. Specifically, the methacrylic acid monomer may be methyl methacrylate (homopolymer Tg is 105°C), ethyl methacrylate (homopolymer Tg is 66°C), n-butyl methacrylate (homopolymer Tg is 20°C), isobutyl methacrylate (homopolymer Tg is 47°C), glycidyl methacrylate (homopolymer Tg is 40°C), tert-butyl methacrylate (homopolymer Tg is 107°C), cyclohexyl methacrylate (homopolymer Tg is 105°C), isobornyl methacrylate (homopolymer Tg is 110°C), or a combination thereof, but the present invention is not limited thereto.

[0049] The acrylic acid monomer can be represented by the general formula CH2=CHCOOR3, where R3 is an alkyl group having 1 to 18 carbon atoms. The acrylic acid monomer can be, but is not limited to, methyl acrylate (homopolymer Tg is 10°C), ethyl acrylate (homopolymer Tg is -21°C), 2-ethylhexyl acrylate (homopolymer Tg is -55°C), n-butyl acrylate (homopolymer Tg is -54°C), or combinations thereof.

[0050] Supplementally, the glass transition temperature of the homopolymer obtained by polymerizing the above-mentioned monomers was measured by a dynamic mechanical analyzer (DMA).

[0051] After the monomer having a double bond is excited to form a free radical, the hydroxyl group-containing monomer provides a crosslinking point, which can be bonded to the methacrylic acid monomer or the acrylic acid monomer. The hydroxyl group-containing monomer may be 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, or a combination thereof, but the present invention is not limited thereto.

[0052] The crosslinking agent in the adhesive composition has multiple functional groups to facilitate the crosslinking reaction. Specifically, the crosslinking agent may be an isocyanate compound having at least three isocyanate groups (-NCO). Examples of such crosslinking agents include hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), and xylene diisocyanate (XDI).

[0053] The catalyst in the adhesive composition may be a metal chelate compound of iron, titanium, or aluminum, such as iron(III) acetylacetonate, tris(2,4-hexanedione)titanium, tris(2,4-hexanedione)aluminum, or a combination thereof.

[0054] The solvent in the adhesive composition may be toluene (boiling point: 110.6°C), propylene glycol methyl ether acetate (boiling point: 149°C), ethyl acetate (boiling point: 77.1°C), or other high boiling solvents, for example, the boiling point of the solvent may be 70°C to 160°C.

[0055] To prove that the adhesive composition of the present invention can form an adhesive layer of a protective film, polymer products of Preparation Examples 1 to 4 were synthesized according to the methods described below. Next, adhesive compositions were prepared using the polymer products of Preparation Examples 1 to 4, thereby producing protective films according to Examples 1 and 2 and Comparative Examples 1 and 2.

[0056] [Preparation Examples 1 to 4] Based on the weight parts shown in Table 1, the monomers for constructing the B block (methacrylic acid monomer, acrylic acid monomer, and hydroxyl group-containing monomer), solvent (ethyl acetate), and initiator (azobisisobutyronitrile) were added to a glass reactor, and the mixture was stirred at 300 rpm under nitrogen gas purging, heated to 65-70°C, and the first-stage reaction was carried out at a constant temperature for 8 hours (conversion rate of 95%) to obtain an intermediate. The intermediate had a solids content of 40 wt% and a viscosity of 1500-2000 cps.

[0057] Next, based on the weight parts shown in Table 2, the monomers for constructing the A block (methacrylic acid monomer, acrylic acid monomer, and hydroxyl group-containing monomer), solvent (ethyl acetate), and initiator (azobisisobutyronitrile) were added. Again under nitrogen gas purging, the mixture was stirred at 300 rpm while maintaining a temperature of 65°C to 70°C. The second-stage reaction was carried out for 8 hours to obtain a polymer product. The solids content of the polymer product was 35 wt% and its viscosity was 2000 cps to 2500 cps. After removing the solvent from the polymer product, an acrylic acid copolymer (acrylic acid block copolymer in Preparation Examples 2 and 3) was obtained.

[0058] The acrylic acid copolymers in Preparation Examples 1 to 4 differ in the weight ratio of the A block to the B block. Specifically, the acrylic acid copolymer in Preparation Example 1 is formed only from the monomer for constituting the A block. The acrylic acid copolymer in Preparation Example 4 is formed only from the monomer for constituting the B block. The polymer products in Preparation Examples 2 and 3 contain an acrylic acid block copolymer having an A block and a B block, but the weight ratio of the two is different. The weight ratios are as shown in Table 3.

[0059] The block ratios, molecular weights and glass transition temperatures of the blocks of the polymer products in Preparation Examples 1 to 4 are as shown in Table 3, where the glass transition temperatures of the blocks were measured using a dynamic mechanical analyzer.

[0060] [Table 1]

[0061] [Table 2]

[0062] [Table 3]

[0063] [Examples 1 and 2] In Examples 1 and 2, adhesive compositions were formed by weighing appropriate amounts of a crosslinker (hexamethylene diisocyanate, e.g., Bayer® N3300), a catalyst, and a solvent (ethyl acetate), and adding the acrylic acid block copolymers of Preparation Examples 2 and 3, respectively. Relative to 100 parts by weight of the acrylic acid block copolymer, the content of the crosslinker was 10 parts by weight, the content of the catalyst was 0.4 parts by weight, and the content of the solvent was 90 parts by weight.

[0064] The adhesive composition was applied to a PET base layer (12 μm thick, model number BH216 manufactured by Nanya Plastics), and then covered with a PET release layer. After drying, an adhesive layer was formed using the adhesive composition to bond the PET base layer and the PET release layer together, thereby producing a protective film.

[0065] To measure the peel resistance of the protective film, the PET release layer was peeled off, and then the adhesive layer was contacted with a printed circuit board coated with solder mask and hot pressed using a roller at a temperature of 60°C, as shown in Figure 3. Next, the peel resistance of the protective film was measured at a peel angle of 180° using a universal testing machine at a temperature of 25°C (peeling temperature), and the results are shown in Table 4.

[0066] [Comparative Examples 1 and 2] The manufacturing methods of the protective films in Comparative Examples 1 and 2 were similar to those in Examples 1 and 2, with the difference being that the acrylic acid block copolymer of the present invention was not used, and the adhesive layers in Comparative Examples 1 and 2 were formed using the acrylic acid copolymer-formed adhesive layers of Preparation Examples 1 and 4, respectively. Similarly, the peel resistance of the protective films was measured at a peel angle of 180° using a universal tensile machine at a temperature of 25°C (peeling temperature), and the results are shown in Table 4.

[0067] [Table 4]

[0068] As can be seen from Tables 1 to 4, the peel resistance of the adhesive layer formed with the adhesive composition of the present invention at a slow peel speed (0.3 m / min) is greater than the peel resistance at a fast peel speed (2.4 m / min). Therefore, after use, the protective film can be quickly peeled off without damaging the solder mask on the printed circuit board or bending the printed circuit board.

[0069] As can be seen from the results of Examples 1 and 2, the protective film according to the present invention has a peel resistance at a high peel speed (2.4 m / min) of less than 80 g / inch, may be less than 60 g / inch, and more preferably is less than 55 g / inch.

[0070] Further experimental observations revealed that the glass transition temperature of the B block was equal to or lower than the peeling temperature, and therefore, when peeling the protective film, the adhesive layer experienced stick-slip instability. As a result, as shown in the results of Examples 1 and 2, the peel resistance of the protective film decreased as the peeling speed increased.

[0071] From the results of Comparative Example 1, it can be seen that when the glass transition temperature of the acrylic acid copolymer is low, the adhesive layer has a relatively good adhesive effect, but the peel resistance of the protective film increases as the peel speed increases, which is unfavorable for quickly peeling the protective film. From the results of Table 4, it was found that the peel resistance also increases as the peel speed increases. Therefore, in order to maintain the integrity of the printed circuit board, the protective film needs to be peeled at a relatively slow peel speed, which makes it difficult to use.

[0072] According to Comparative Example 2, when the glass transition temperature of the acrylic acid copolymer is relatively high, the adhesive layer has a weak adhesive effect, which is advantageous for quickly peeling the protective film but disadvantageous for bonding to a printed circuit board. Prior to the exposure process, the protective film is cleaned with a silicone roller to prevent dust from affecting the exposure effect. Typically, the adhesive strength when cleaning with a silicone roller is approximately 30 g / inch. If the protective film has low peel resistance, the protective film may be adhered to the silicone roller during dust removal. In Comparative Example 2, the protective film may occasionally become distorted at the edges during the process of cleaning with the roller, which may result in poor usability.

[0073] [Advantageous Effects of the Embodiments] One of the advantageous effects of the present invention is that the protective film and adhesive composition of the present invention have the technical features that "the adhesive composition comprises an acrylic acid block copolymer, and the acrylic acid block copolymer comprises an A block and a B block" and "the glass transition temperature of the A block is lower than the glass transition temperature of the B block," which enable the protective film to have good adhesive strength and be quickly and easily peeled off.

[0074] The above disclosure is merely a preferred embodiment of the present invention, and the scope of the claims of the present invention is not limited thereto. Therefore, any equivalent technical modifications made using the specification and drawings of the present invention are included in the scope of the claims of the present invention. [Explanation of symbols]

[0075] 1...Base material layer 2...Adhesive layer 3…Release layer P...Printed circuit board S...Solder mask

Claims

1. an acrylic acid block copolymer formed by two-stage free radical polymerization of methacrylic acid monomers, acrylic acid monomers, and hydroxyl-containing monomers; a cross-linking agent; a catalyst; the glass transition temperature of the homopolymer obtained by polymerizing the methacrylic acid monomer is higher than the glass transition temperature of the homopolymer obtained by polymerizing the acrylic acid monomer; The acrylic acid block copolymer comprises an A block and a B block, and the glass transition temperature of the A block is lower than the glass transition temperature of the B block; the content of the methacrylic acid monomer in the A block is less than the content of the methacrylic acid monomer in the B block, and the content of the acrylic acid monomer in the A block is greater than the content of the acrylic acid monomer in the B block; an adhesive composition, characterized in that the content of the crosslinking agent is 1 part by weight to 10 parts by weight and the content of the catalyst is 0.001 part by weight to 0.05 part by weight, relative to 100 parts by weight of the acrylic acid block copolymer.

2. 2. The adhesive composition according to claim 1, wherein the A block has a glass transition temperature of −40° C. to −10° C.

3. The adhesive composition according to claim 1, wherein the B block has a glass transition temperature of 10°C to 25°C.

4. 2. The adhesive composition according to claim 1, wherein the content of the A block is 10% by weight to 20% by weight and the content of the B block is 80% by weight to 90% by weight, where the total weight of the acrylic acid block copolymer is 100% by weight.

5. The adhesive composition according to claim 1, wherein the homopolymer obtained by polymerizing the methacrylic acid monomer has a glass transition temperature of 15°C to 115°C, and the homopolymer obtained by polymerizing the acrylic acid monomer has a glass transition temperature of -70°C to 10°C.

6. 2. The adhesive composition of claim 1, wherein the methacrylic acid monomer is selected from the group consisting of methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, glycidyl methacrylate, tert-butyl methacrylate, cyclohexyl methacrylate, and isobornyl methacrylate.

7. 2. The adhesive composition of claim 1, wherein the acrylic acid monomer is selected from the group consisting of methyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate, and n-butyl acrylate.

8. 2. The adhesive composition according to claim 1, wherein the hydroxyl group-containing monomer is selected from the group consisting of 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate.

9. 2. The adhesive composition according to claim 1, wherein the A block consists of 5% by weight to 15% by weight of the methacrylic acid monomer, 75% by weight to 90% by weight of the acrylic acid monomer, and 5% by weight to 10% by weight of the hydroxyl group-containing monomer.

10. 2. The adhesive composition according to claim 1, wherein the B block consists of 25% by weight to 35% by weight of the methacrylic acid monomer, 45% by weight to 70% by weight of the acrylic acid monomer, and 5% by weight to 10% by weight of the hydroxyl group-containing monomer.

11. 2. The adhesive composition according to claim 1, wherein the number average molecular weight of the acrylic acid block copolymer is 300,000 g / mol to 500,000 g / mol.

12. The adhesive composition of claim 1, wherein the acrylic acid block copolymer has a polymer dispersity index (PDI) of 1.5 to 5.

13. a substrate layer; An adhesive layer formed from the adhesive composition according to any one of claims 1 to 12; A protective film comprising a release layer, A protective film, characterized in that the adhesive layer is disposed between the base layer and the release layer.

14. The protective film according to claim 13, wherein the adhesive layer has a thickness of 2 μm to 20 μm.

15. The protective film according to claim 13, wherein the resistance of the protective film when peeled at a peeling speed of 0.3 m / min is greater than the resistance when peeled at a peeling speed of 2.4 m / min at a peeling temperature of 25°C.

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