KR102087428B1 - Photo curable adhesive and bonding composition and adhesive film - Google Patents

Abstract

A (meth) acrylic photocurable compound comprising one selected from the group consisting of (meth) acrylic monomers, (meth) acrylic oligomers, (meth) acrylic prepolymers, and combinations thereof; Chain transfer agents; It provides a photocurable pressure-sensitive adhesive composition comprising; and a photoinitiator.

Description

Photocurable adhesive composition and adhesive film {PHOTO CURABLE ADHESIVE AND BONDING COMPOSITION AND ADHESIVE FILM}

It relates to a photocurable adhesive composition and an adhesive film.

Bonding or fixing parts in the electrical or electronics industry is an important issue, and in order to bond two or more different materials or parts to each other, it is necessary to use an adhesive with good adhesion on both sides. Specifically, the display is composed of a touch screen panel (TSP) and a liquid crystal module, and the touch screen panel has a laminated structure such as a conductive film and a transparent substrate. In this case, an adhesive is used to attach each layer to the laminated structure of the touch screen panel, and an adhesive is also used to attach the touch screen panel and the liquid crystal module. Adhesives for this purpose are commonly referred to as optical clear adhesives (OCAs), and the optical clear adhesives should implement excellent adhesive performance without degrading physical properties such as touch sensitivity and visibility. In particular, adhesives used in touch screens or touch panels may have significant step absorbency depending on the location of use.

One embodiment of the present invention is a photocurable pressure-sensitive adhesive composition used for direct bonding between a touch screen panel and a liquid crystal module, and provides a pressure-sensitive adhesive composition having excellent step absorption.

Another embodiment of the present invention provides a pressure-sensitive adhesive film prepared from the photocurable pressure-sensitive adhesive composition provides excellent step absorption performance.

In one embodiment of the present invention, a (meth) acrylic monomer, a (meth) acrylic oligomer, a (meth) acrylic prepolymer and a (meth) acrylic photocurable compound including one selected from the group consisting of a combination thereof; Chain transfer agents; It provides a photocurable pressure-sensitive adhesive composition comprising; and a photoinitiator.

In another embodiment of the present invention, it provides a pressure-sensitive adhesive film comprising a cured product of the photocurable pressure-sensitive adhesive composition.

The photocurable pressure-sensitive adhesive composition and pressure-sensitive adhesive film may implement an improved stress relaxation and improved step absorbance with excellent cutting properties.

Advantages and features of the present invention, and methods for achieving the same will be apparent with reference to the following embodiments. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various forms. The present embodiments are merely provided to make the disclosure of the present invention complete, and to fully inform the scope of the invention to those skilled in the art.

In one embodiment of the present invention, a (meth) acrylic monomer, a (meth) acrylic oligomer, a (meth) acrylic prepolymer and a (meth) acrylic photocurable compound including one selected from the group consisting of a combination thereof; Chain transfer agents; And a photoinitiator; provides a photocurable pressure-sensitive adhesive composition comprising

The photocurable pressure-sensitive adhesive composition may impart improved stress relaxation and improved step absorbance to the pressure-sensitive adhesive film formed by photocuring reaction thereof.

Generally, when sticking an adhesive film to the printing step part of a touch panel, there exists a problem which a bubble is easy to produce. For example, when a colored layer is formed by printing for the purpose of decoration or light shielding on a touch panel, a printing step of about several tens of micrometers is generated, and bubbles are generated when an adhesive film is attached to the printing step.

The generation | occurrence | production of a bubble can be suppressed by reducing the stress of an adhesive film and giving a level | step difference absorptivity.

In general, in order to impart excellent step absorbency to the pressure-sensitive adhesive film, a method of controlling the glass transition temperature of the prepolymer included in the pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive film, a method of adjusting the content of an initiator or a curing agent included in the pressure-sensitive adhesive composition, or adhesion There may be a method for adjusting the gel content of the film.

However, when the stress of the pressure-sensitive adhesive film is relieved in this manner to impart step difference absorbency, the fluidity of the pressure-sensitive adhesive film becomes excessively high, resulting in poor cutting, and easy development of residual adhesive. As the physical properties of the pressure-sensitive adhesive film decreases with time, workability deteriorates.

The photocurable pressure-sensitive adhesive composition includes a (meth) acrylic photocurable compound, a chain transfer agent, and a photoinitiator, and when the photocurable is formed to form an adhesive film, the (meth) acrylic photocurable compound and the chain transfer agent react to each other. The film can be given improved stress relaxation and improved step absorbency. In addition, the adhesive film may have excellent cutting properties at the same time. That is, the adhesive film, which is a cured product of the photocurable pressure sensitive adhesive composition, may have improved stress relaxation and improved step absorbency without controlling the glass transition temperature of the prepolymer as described above.

The chain transfer agent included in the photocurable pressure-sensitive adhesive composition is added to the (meth) acrylic photocurable compound formed after the polymerization reaction has already been completed, and used in a curing reaction for curing the photocurable pressure-sensitive adhesive composition to form an adhesive film. It should generally be distinguished from the use of a chain transfer agent in admixture with monomers in the polymerization into prepolymers, ie in the polymerization reaction. When a chain transfer agent is used in the polymerization reaction of the monomer, the molecular weight of the prepolymer which is a polymer obtained is controlled. In contrast, the chain transfer agent included in the photocurable pressure-sensitive adhesive composition has a chain length during photocuring reaction with respect to the (meth) acrylic photocurable compound, that is, (meth) acrylic monomer, (meth) acrylic oligomer, or (meth) acrylic prepolymer. Can be adjusted.

The said chain transfer agent acts on the hardening reaction of the (meth) acrylic-type monomer, the (meth) acrylic-type oligomer, or the (meth) acrylic-type prepolymer contained in the said (meth) acrylic-type photocurable compound, and is an adhesive film which is a hardened | cured material of the said photocurable resin composition. It can give a better cutting performance and improved stress relaxation and improved step absorption.

The (meth) acrylic photocurable compound means a compound which can be photocurable including an acrylate group which is a reaction site that undergoes photocuring reaction by light, and can be obtained as a result obtained by polymerizing a (meth) acrylic monomer. The result obtained by polymerizing such a (meth) acrylic monomer includes not only the (meth) acrylic oligomer and (meth) acrylic prepolymer obtained by the polymerization reaction, but also the unreacted (meth) acrylic monomer.

The chain transfer agent is used in the curing reaction of the photocurable pressure-sensitive adhesive composition containing the (meth) acrylic photocurable compound, the (meth) acrylic photocurable compound, that is, (meth) acrylic monomer, (meth) acrylic oligomer, or It may participate in a curing reaction by reacting with a (meth) acrylic prepolymer. Specifically, when the (meth) acrylic monomer, the (meth) acrylic oligomer, or the (meth) acrylic prepolymer are linked to each other or to form a three-dimensional network structure, the chain transfer agent shortens the length of the chain. I can regulate it. Through this, the adhesive film, which is a cured product of the pressure-sensitive adhesive composition, may have improved step absorbability and at the same time excellent cutting properties.

Specifically, the chain transfer agent is a mercaptan compound including one selected from the group consisting of lauryl mercaptan, n-dodecyl mercaptan, n-octyl mercaptan, lauryl mercaptan, alpha-methylstyrene dimer, bro Motrichloromethane (Bromotrichloromethane) may include one selected from the group consisting of a combination thereof.

In one embodiment, the photocurable pressure-sensitive adhesive composition includes alpha-methylstyrene dimer as the chain transfer agent, it is possible to more easily control the degree of cure and step absorption. For example, the alpha-methylstyrene dimer is 2,4-diphenyl-4-methyl-1-pentene, 2,4-diphenyl-4- It may include one selected from the group consisting of methyl-2-pentene (2,4-diphenyl-4-methyl-2-pentene) and combinations thereof.

Specifically, the alpha-methylstyrene dimer is combined with a (meth) acrylic monomer, (meth) acrylic oligomer, and (meth) acrylic prepolymer included in the (meth) acrylic photocurable compound to have a phenyl group having a stable structure at a chain end. As such, excellent terminal modifications can be exhibited. Accordingly, the photocurable pressure sensitive adhesive composition including the alpha-methylstyrene dimer has excellent durability under high temperature and high humidity, and provides high storage so that physical properties of the pressure-sensitive adhesive film prepared therefrom may not be degraded even after several months to several years. Can be.

In addition, the alpha-methylstyrene dimer may not remain an anionic material or the like in a product prepared from the photocurable pressure-sensitive adhesive composition comprising the same. Accordingly, it is possible to prevent anions remaining in the product from reacting with heat and light to deteriorate the product.

In addition, the photocurable pressure-sensitive adhesive composition comprising the alpha-methylstyrene dimer that does not leave an anionic material that may affect the electrical signal may be more suitable for use of the pressure-sensitive adhesive film used in electronic products.

The amount of the chain transfer agent included in the photocurable pressure sensitive adhesive composition may be about 0.01 to about 0.05 parts by weight based on 100 parts by weight of the (meth) acrylic photocurable compound.

The photocurable pressure-sensitive adhesive composition comprises the chain transfer agent in the content of the above range, the curing reaction of the (meth) acrylic monomer, (meth) acrylic oligomer, (meth) acrylic prepolymer contained in the (meth) acrylic photocurable compound By properly adjusting and adjusting to have an appropriate chain length, it is possible to give the adhesive film an appropriate adhesive performance, and to realize improved stress relaxation and improved step absorbance with excellent cutting property.

When the (meth) acrylic photocurable compound is used as a result obtained by polymerizing the (meth) acrylic monomer as described above, the unreacted monomer, oligomer and prepolymer to be obtained by polymerization at a conversion rate of about 10 to about 60% It may be a mixture. That is, the (meth) acrylic photocurable compound is a (meth) acrylic monomer, a (meth) acrylic oligomer, or a (meth) acrylic prepolymer, using a mixture of the resultant obtained by polymerizing a (meth) acrylic monomer at a conversion ratio in the above range. And combinations thereof may include one selected from the group consisting of.

The photocurable pressure-sensitive adhesive composition comprises one selected from the group consisting of (meth) acrylic monomers, (meth) acrylic oligomers, (meth) acrylic prepolymers, and combinations thereof obtained by polymerizing a (meth) acrylic monomer at a conversion rate in the above range. By including the (meth) acrylic-based photocurable compound, it is possible to maintain an appropriate adhesive force, steam is not generated in the punching process, excellent workability, and excellent step absorption.

The (meth) acrylic monomers include one selected from the group consisting of alkyl (meth) acrylates having C ₁ -C ₂₂ alkyl groups, alicyclic (meth) acrylates having C ₃ -C ₁₅ cycloalkyl groups, and combinations thereof can do.

Specifically, the alkyl (meth) acrylate having a C ₁ -C ₂₂ alkyl group may be an alkyl (meth) acrylate having a linear or branched C ₁ -C ₂₂ alkyl group. For example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, pentyl (meth) acrylate, n-octyl (meth) acrylic Late, lauryl (meth) acrylate, tetradecyl (meth) acrylate, isopropyl (meth) acrylate, t-butyl (meth) acrylate, sec-butyl (meth) acrylate, 2-ethylhexyl (meth) ) Acrylate, 2-ethylbutyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, and combinations thereof.

In addition, the alicyclic (meth) acrylate having the C ₃ -C ₁₅ cycloalkyl group is isobonyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate (tetrahydrofurfuryl (meth) acrylate), cyclohexyl (meth) It may include one selected from the group consisting of cyclohexyl (metha) crylate and combinations thereof.

The (meth) acrylic oligomer and the (meth) acrylic prepolymer are polymerized from the (meth) acrylic monomer component, and are included in the pressure-sensitive adhesive film that reacts with the chain transfer agent to form a cured product.

The weight average molecular weight of the (meth) acrylic oligomer may be about 500,000 or less. Specifically, it may be about 50,000 to about 300,000. The weight average molecular weight (Mw) of the (meth) acrylic prepolymer included in the photocurable pressure sensitive adhesive composition may be about 1 million to about 3.5 million. The photocurable pressure sensitive adhesive composition includes a (meth) acrylic prepolymer having a weight average molecular weight in the above range, thereby imparting appropriate adhesive force to the adhesive film and providing sufficient adhesive holding force even in an environment of high temperature and high humidity.

The glass transition temperature (Tg) of the (meth) acrylic prepolymer included in the photocurable pressure sensitive adhesive composition may be about −50 ° C. to about −10 ° C. Specifically, it may be about −40 ° C. or more, and more specifically about −30 ° C. or more.

As described above, the glass transition temperature of the prepolymer included in the pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive film may be adjusted to impart step difference absorbency to the pressure-sensitive adhesive film. Specifically, the lower the glass transition temperature of the prepolymer included in the pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive film, the pressure-sensitive adhesive film may have a high step absorbency.

However, if the glass transition temperature of the prepolymer is too low, the step absorption of the cured film thereof may be improved, but there is a problem such as poor cutting property.

The photocurable pressure-sensitive adhesive composition may include the (meth) acrylic prepolymer having a glass transition temperature in the above range, and may provide improved stress relaxation and improved step absorbency to the cured adhesive film thereof. In addition, the adhesive film may have excellent cutting properties.

The (meth) acrylic photocurable compound may be a mixture of unreacted monomers, oligomers and prepolymers obtained by further polymerizing a crosslinkable monomer in addition to the (meth) acrylic monomer.

The crosslinkable monomer may include one selected from the group consisting of a monomer having a hydroxy group, a monomer having a carboxyl group, a monomer having a nitrogen-containing functional group, and a combination thereof. These are monomers having a hydrophilic functional group, and are used as constituent monomers of the (meth) acrylic prepolymer, thereby improving adhesion performance and cohesion.

The monomer having a hydroxy group is hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 5-hydroxypentyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 10- Hydroxydecyl (meth) acrylate, (4-hydroxymethylcyclohexyl) methyl (meth) acrylate, caprolactone modified 2-hydroxyethyl (metal) acrylate, 2-acryloyloxyethyl-2-hydride Oxylethylphthalic acid, N-methylol (meth) acrylimide, N-hydroxyethyl (meth) acrylate, 2-hydroxy propyl (meth) acrylate, 2-hydroxy-3-propyl (meth) acrylate , 3-chloro-2-hydroxypropyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 2,2-dimethyl-2-hydroxyethyl (meth) acrylate, and these It may include one selected from the group consisting of a combination of.

The monomer having a carboxyl group is acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, fumaric acid, glycolic acid, cinnamic acid, acrylic acid dimer, methacrylic acid dimer, acrylic acid trimer, acrylic acid tetramer, methacrylic acid Tetramer, 2-acryloyloxyethyl succinic acid monoester, 2-methacryloyloxy succinic acid monoester, 2-acryloyloxyethyl phthalic acid monoester, 2-methacryloyloxyethyl phthalic acid monoester, 2- It may include one selected from the group consisting of acryloyloxyethyl hexahydrophthalic acid monoester, 2-methacryloyloxyethylhexahydrophthalic acid monoester, and combinations thereof.

The monomer having a nitrogen-containing functional group is N-vinylpinyridone, N-vinylcaprolactam, acryloyl morpholine, acrylonitrile, acrylamide, N, N-dimethylacrylamide, dimethylaminoethyl (meth) acrylate And combinations thereof may include one selected from the group consisting of.

The photocurable pressure-sensitive adhesive composition includes a photoinitiator together with a (meth) acrylic photocurable compound and a chain transfer agent. The photoinitiator is a substance that initiates a curing reaction by causing an active reaction when irradiating a certain amount of light.

Specifically, the photoinitiator alpha-hydroxy ketone initiator, phenylglyoxylate initiator, benzyldimethyl- ketal initiator, alpha-amino ketone initiator, monoacylphosphine initiator, bisacylphosphine initiator, phosphine oxide initiator It may include one selected from the group consisting of metallocene initiators, iodonium salt initiators and combinations thereof.

In addition, the photocurable pressure-sensitive adhesive composition may include the photoinitiator in an amount of about 0.01 to about 5.0 parts by weight based on 100 parts by weight of the (meth) acrylic photocurable compound. By including the photoinitiator in the content of the above range, it is possible to secure an appropriate level of degree of curing, and as a result it can implement an excellent step absorption.

The photocurable pressure sensitive adhesive composition may further include one or more additives selected from the group consisting of a curing agent, a crosslinking agent, an ultraviolet stabilizer, an antioxidant, a reinforcing agent, a filler, an antifoaming agent, a surfactant, a plasticizer, and a combination thereof.

For example, the photocurable pressure-sensitive adhesive composition may further include a curing agent, and in this case, the curing agent may be included in an amount of about 0.1 to about 1.0 parts by weight based on 100 parts by weight of the (meth) acrylic photocurable compound.

As described above, by adjusting the content of the curing agent included in the pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive film, it is possible to impart step difference absorbency to the pressure-sensitive adhesive film. Specifically, as the content of the curing agent is lowered, the adhesive film may have higher step absorbency. However, there is a problem such as poor cutting property.

The photocurable pressure-sensitive adhesive composition may include a hardening agent in the above range, and may provide improved stress relaxation and improved step absorbency to an adhesive film thereof. In addition, the adhesive film may have excellent cutting properties.

In another embodiment of the present invention, there is provided an adhesive film comprising a cured product of the photocurable pressure-sensitive adhesive composition.

The pressure-sensitive adhesive film is formed by photocuring the photocurable pressure-sensitive adhesive composition, wherein the photocurable pressure-sensitive adhesive composition includes a (meth) acrylic photocurable compound, a chain transfer agent, and a photoinitiator, as described above. The photocurable compound and the chain transfer agent react to impart improved stress relaxation and improved step absorbency to the adhesive film. In addition, the adhesive film may have excellent cutting properties at the same time.

Specifically, the adhesive film may have a loss factor (tanδ) of about 0.5% to about 0.8 when the strain is about 10% at a temperature of about 40 ° C. and a frequency of about 1 rad / sec (= 0.1591549 Hz). The loss coefficient tan δ is a value obtained by dividing the loss modulus G`` by the storage modulus G` (G`` / G`), and the loss modulus and storage modulus are ARES (Advanced Rheometric). It can be measured using an Expansion System. Specifically, the loss coefficient may be measured by measuring the storage modulus and the loss modulus when the strain is about 10% at a frequency of about 1 rad / sec (= 0.1591549 Hz) at a temperature of about 40 ° C.

[Equation 1]

Loss factor (tanδ) = loss modulus (G``) / storage modulus (G`)

The adhesive film may have a loss factor (tan δ) in the above range, and may have an improved stress relaxation and an improved step absorbency with appropriate adhesive force and peel force.

In addition, the pressure-sensitive adhesive film may be about 10% elongation at a temperature of about 25 ° C may be about 80% to about 95% of the stress relaxation rate when maintained for about 180 seconds. That is, the stress relaxation ratio measured by Equation 2 may be about 80% to about 95%.

[Equation 2]

% Stress relaxation = {(initial stress-stress after relaxation) / initial stress} × 100

Since the stress relaxation rate of the pressure-sensitive adhesive film satisfies the above range, when the pressure-sensitive adhesive film is attached to the printing step, the generation of bubbles may be suppressed due to the improved level absorbency.

The following presents specific embodiments of the present invention. However, the embodiments described below are merely for illustrating or explaining the present invention in detail, and thus the present invention is not limited thereto.

Example  One

A mixed monomer component was prepared comprising 60 weight percent 2-ethylhexyl acrylate (EHA), 15 weight percent isobonyl methacrylate (IBOMA) and 20 weight percent hydroxyethyl acrylate (HEA). The mixed monomer component was thermally polymerized to have a conversion ratio of 20% to obtain a (meth) acrylic prepolymer (glass transition temperature (-42) ° C.) having a weight average molecular weight (Mw) of 1 million. As a (meth) acrylic photocurable compound, a product obtained by thermally polymerizing the mixed monomer component was prepared, and the (meth) acrylic photocurable compound together with the (meth) acrylic prepolymer includes an unreacted monomer and an oligomer form together. Obtained in the form of syrup.

0.01 weight part of alpha-methylstyrene dimers were contained with respect to 100 weight part of said (meth) acrylic-type photocurable compounds, and 0.3 weight part of benzyldimethyl- ketal initiators were mixed as a photoinitiator, and the photocurable adhesive composition was prepared.

Example  2

A photocurable pressure-sensitive adhesive composition was prepared in the same manner as in Example 1, except that 0.03 part by weight of alpha-methylstyrene dimer was included based on 100 parts by weight of the (meth) acrylic photocurable compound.

Example  3

A photocurable pressure-sensitive adhesive composition was manufactured in the same manner as in Example 1, except that 0.05 part by weight of alpha-methylstyrene dimer was included based on 100 parts by weight of the (meth) acrylic photocurable compound.

Example  4

A photocurable pressure-sensitive adhesive composition was prepared in the same manner as in Example 1, except that 0.07 part by weight of alpha-methylstyrene dimer was included based on 100 parts by weight of the (meth) acrylic photocurable compound.

Example  5

A photocurable pressure-sensitive adhesive composition was manufactured in the same manner as in Example 1, except that 0.03 part by weight of n-dodecyl mercaptan (n-DDM, n-dodecyl mercaptan) was included based on 100 parts by weight of the (meth) acrylic photocurable compound. It was.

Example  6

A photocurable pressure-sensitive adhesive composition was manufactured in the same manner as in Example 1, except that 0.03 part by weight of bromotrichloromethane was included with respect to 100 parts by weight of the (meth) acrylic photocurable compound.

Comparative example  One

A photocurable pressure-sensitive adhesive composition was prepared in the same manner as in Example 1, except that no chain transfer agent was included for the (meth) acrylic photocurable compound.

Photocurable Adhesive Composition (Meth) acrylic photocurable compound Chain transfer agent Photoinitiator
(Part by weight) Kinds Content (parts by weight) Example 1 100 parts by weight Alpha-methylstyrene dimer 0.01 0.3 Example 2 100 parts by weight Alpha-methylstyrene dimer 0.03 0.3 Example 3 100 parts by weight Alpha-methylstyrene dimer 0.05 0.3 Example 4 100 parts by weight Alpha-methylstyrene dimer 0.07 0.3 Example 5 100 parts by weight n-dodecyl mercaptan 0.03 0.3 Example 6 100 parts by weight Bromotrichloromethane 0.03 0.3 Comparative Example 1 100 parts by weight 0.3

<Evaluation>

The photocurable adhesive composition of Examples 1-6 and Comparative Example 1 was irradiated with a light amount of 2 J / cm 2 to form a photocured product. Thus, an adhesive film containing the photocured product was prepared.

1. Loss Factor (tanδ)

About the adhesive films manufactured from Examples 1-6 and Comparative Example 1, the loss coefficient (tanδ) of the following Formula 1 was measured using ARES-G2 equipment from TA instrument.

Specifically, using the ARES-G2 parallel plate (parallel plate), at a temperature of 40 ℃, it was set to a vertical force of 204gf (= 2N), and then in a strain condition of 10%, 1rad / The storage modulus (G ') and loss modulus (G ") at sec (= 0.1591549 Hz) were measured and substituted into Equation 1 to determine the loss factor (tanδ). The results are shown in Table 2 below. .

[Equation 1]

Loss factor (tanδ) = loss modulus (G ") / storage modulus (G ')

2. Stress relaxation rate (%)

About the adhesive films manufactured from Examples 1 to 6 and Comparative Example 1, using the ARES-G2 equipment of TA instrument, the stress relaxation rate (%) of the following formula (2) was measured.

Specifically, the pressure-sensitive adhesive film was allowed to elongate 10% at a temperature of 25 ℃. The stress (initial stress) at this time was measured. Moreover, the stress (stress after relaxation) when the said state was hold | maintained for 180 second was measured. The stress relaxation rate was measured by substituting the obtained initial stress and the stress value after relaxation into Equation 2 below. The results are shown in Table 2 below.

[Equation 2]

% Stress relaxation = {(initial stress-stress after relaxation) / initial stress} × 100

3. Step  Absorbency

A pressure-sensitive adhesive film prepared in Examples 1 to 6 and Comparative Example 1 was placed in a cover window in which a step of 15 μm was printed at 4 corners of the corner, and the release polyethyleneterephthalate (PET) was removed, and 0.55T of glass was attached on top. Thereafter, after pressing the autoclave at 40 ° C. and 4 bar for 20 minutes, the shape of the bubbles was visually observed on the printing step, and evaluated according to the following evaluation criteria. The results are shown in Table 2 below.

<Evaluation Criteria>

-Good: No bubbles are observed in 3 of 4 corners.

-Good: No bubbles are observed in 2 of 4 corners.

-Poor: No bubble is observed in 1 of 4 corners.

Stress relaxation rate (%) Loss factor (tanδ) Step absorbency Example 1 82 0.49 Good Example 2 89 0.58 good Example 3 92 0.71 good Example 4 95 0.80 good Example 5 84 0.52 Good Example 6 82 0.50 Good Comparative Example 1 74 0.40 Bad

It can be seen that the adhesive film prepared from the example has a high stress relaxation ratio of about 80% to about 95% and a loss factor of about 0.5 to about 0.8, and exhibits improved step absorption.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of the invention.

Claims (15)

A (meth) acrylic photocurable compound comprising one selected from the group consisting of (meth) acrylic monomers, (meth) acrylic oligomers, (meth) acrylic prepolymers, and combinations thereof; Chain transfer agents that are alpha-methylstyrene dimers; And a photoinitiator; Photocurable pressure-sensitive adhesive composition comprising.
delete The method of claim 1,
The alpha-methylstyrene dimer is 2,4-diphenyl-4-methyl-1-pentene, 2,4-diphenyl-4-methyl-2- Pentene (2,4-diphenyl-4-methyl-2-pentene) and combinations thereof
Photocurable adhesive composition.

The method of claim 1,
The content of the chain transfer agent is 0.01 to 0.05 parts by weight based on 100 parts by weight of the (meth) acrylic photocurable compound.
Photocurable adhesive composition.

The method of claim 1,
The (meth) acrylic photocurable compound is formed with a conversion rate of 10% to 60%
Photocurable adhesive composition.
The method of claim 1,
The (meth) acrylic monomers include one selected from the group consisting of alkyl (meth) acrylates having C ₁ -C ₂₂ alkyl groups, alicyclic (meth) acrylates having C ₃ -C ₁₅ cycloalkyl groups, and combinations thereof doing
Photocurable adhesive composition.

The method of claim 6,
The alkyl (meth) acrylate having the C ₁ -C ₂₂ alkyl group is methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, pentyl ( Meth) acrylate, n-octyl (meth) acrylate, lauryl (meth) acrylate, tetradecyl (meth) acrylate, isopropyl (meth) acrylate, t-butyl (meth) acrylate, sec-butyl (Meth) acrylate, 2-ethylhexyl (meth) acrylate, 2-ethylbutyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, and combinations thereof Containing one
Photocurable adhesive composition.

The method of claim 6,
The cycloaliphatic (meth) acrylate having a C ₃ -C ₁₅ cycloalkyl group is a group consisting of isobornyl (meth) acrylate, tetrahydroperfuryl (meth) acrylate, cyclohexyl (meth) acrylate, and combinations thereof Containing one selected from
Photocurable adhesive composition.

The method of claim 1,
The weight average molecular weight (Mw) of the (meth) acrylic prepolymer is 1 million to 3.5 million
Photocurable adhesive composition.

The method of claim 1,
Tg of the (meth) acrylic-based prepolymer is -50 ℃ to -10 ℃
Photocurable adhesive composition.

The method of claim 1,
The photoinitiator is alpha-hydroxy ketone initiator, phenylglyoxylate initiator, benzyldimethyl- ketal initiator, alpha-amino ketone initiator, monoacylphosphine initiator, bisacylphosphine initiator, phosphine oxide initiator, metallo It includes one selected from the group consisting of a senyu initiator, an iodonium salt initiator and a combination thereof
Photocurable adhesive composition.

The method of claim 1,
The content of the photoinitiator is 0.01 to 5.0 parts by weight based on 100 parts by weight of the (meth) acrylic photocurable compound.
Photocurable adhesive composition.

The adhesive film containing the hardened | cured material of the photocurable adhesive composition of any one of Claims 1-11.

The method of claim 13,
The adhesive film has a loss coefficient (tanδ) of 0.5 to 0.8 at a strain of 10% at a temperature of 40 ° C. and a frequency of 1 rad / sec.
Adhesive film.

The method of claim 13,
The pressure-sensitive adhesive film has a stress relaxation rate of 80% to 95% when stretched 10% at a temperature of 25 ℃ maintained for 180 seconds
Adhesive film.