KR102154998B1 - Optically clear adhensive tape and manufacturing method thereof - Google Patents

Abstract

The present invention relates to an optically transparent adhesive tape, prepared from an optically transparent adhesive composition comprising a prepolymer syrup obtained by partially polymerizing an acrylate-based compound and a photoinitiator, a photoinitiator for primary curing, and a photoinitiator for secondary curing, and the optically transparent It is an optically transparent adhesive tape having a step absorption property that is completely cured by secondary curing after the adhesive composition is first cured to maintain a semi-cured state and adhered to a substrate having a step difference in a semi-cured state.
The optical adhesive tape of the present invention has excellent effects in step absorption and durability.

Description

Optically transparent adhesive tape with improved step absorption, and manufacturing method thereof

The present invention relates to an optically transparent adhesive tape used in an electronic device and a method for manufacturing the same, and to an optically transparent adhesive tape with improved step absorption and durability by a double curing method, and a method for manufacturing the same.

Recently, optically transparent adhesive tapes have been widely used for bonding optical members used in electronic components such as liquid crystal displays and touch panels.

The optically transparent adhesive tape has a structure in which a conductive glass, a reinforcing material, or a decor film is laminated through an adhesive layer on which an adhesive composition is applied to a film such as polyethylene terephthalate.

At this time, when a printing unit is formed on conductive glass, reinforcement material, or teco film, when a transparent adhesive tape is laminated on the printing unit, a step equal to the height of the printing unit is generated, so that the bending of light occurs in the stepped area. do.

Therefore, there is a need for technology development for an optically transparent adhesive tape with improved step absorption ability that can overcome such a step difference.

A first object of the present invention is to provide a transparent adhesive tape with improved step absorption performance of a printing unit.

A second object of the present invention is also to provide an optically transparent adhesive tape in which durability is not reduced while improving step absorption performance.

The optically transparent adhesive tape of the present invention for solving the above problems is prepared from an optically transparent adhesive composition comprising a prepolymer syrup obtained by partially polymerizing an acrylate compound and a photoinitiator, a photoinitiator for primary curing, and a photoinitiator for secondary curing. , An optically transparent adhesive tape having a step absorption property that maintains a semi-cured state by first curing the optically transparent adhesive composition, adheres to a substrate having a step difference in a semi-cured state, and then is completely cured by secondary curing.

In the optically transparent adhesive tape of the present invention, the gel fraction after the first curing is 30 to 50%, and the gel fraction after the second curing is 60% or more.

In an embodiment of the present invention, the photoinitiator for primary curing is 1-hydroxy-cyclohexylphenyl ketone, and the photoinitiator for secondary curing is acryloyl benzophenone, acrylo It is preferably one selected from the group consisting of ylethyl benzophenone and acryloyloxy benzophenone.

In an embodiment of the present invention, the optically transparent adhesive composition preferably comprises 100 parts by weight of the prepolymer syrup, 0.3 to 0.9 parts by weight of a photoinitiator for primary curing, and 0.2 to 0.9 parts by weight of a photoinitiator for secondary curing.

In addition, the method of manufacturing an optically transparent adhesive tape of the present invention includes the steps of preparing a prepolymer syrup obtained by partially polymerizing an acrylate-based compound and a photoinitiator; Preparing an optically transparent adhesive composition by adding and mixing a photoinitiator for primary curing and a photoinitiator for secondary curing to the prepolymer syrup; First curing the optically transparent adhesive composition; And secondary curing the first cured optically transparent adhesive composition. It characterized in that it comprises a.

In one embodiment of the present invention, in the first curing step, it is preferable to irradiate a light amount of 0.8 to 1.3 J/cm 2, and in the secondary curing step, it is preferable to irradiate a light amount of 3 to 5 J/cm 2. .

The optical adhesive tape of the present invention has excellent effects in step absorption and durability.

Hereinafter, the present invention will be described in detail with reference to embodiments of the present invention and drawings. These examples are only illustratively presented to explain the present invention in more detail, and it will be apparent to those of ordinary skill in the art that the scope of the present invention is not limited by these examples. .

The optically transparent adhesive tape of the present invention is prepared from an optically transparent adhesive composition comprising a prepolymer syrup obtained by partially polymerizing an acrylate compound and a photoinitiator, a photoinitiator for primary curing, and a photoinitiator for secondary curing, and the optically transparent adhesive composition A semi-cured state is maintained by this primary curing, and after being adhered to a substrate having a step difference in a semi-cured state, it is an optically transparent adhesive tape having step absorption properties that is completely cured by secondary curing.

The optically transparent adhesive tape has excellent durability when the adhesive layer has a high gel fraction and modulus, but a high gel fraction and modulus are factors that weaken the step absorption performance. Therefore, it is important to control the adhesive layer to have an appropriate level of gel fraction and modulus in order to improve the step absorption performance. In the present invention, in order to realize an appropriate gel fraction and modulus, in preparing the adhesive layer, it is characterized in that it introduces double photocuring.

That is, through the dual photocuring method, after the first curing, the gel fraction of the adhesive layer is controlled to a level of 30-50% to improve the step absorption performance, and after the second curing, the gel fraction of the adhesive layer is reduced by 60%. By controlling above, the durability was prevented from deteriorating.

In the present invention, first, a photopolymerizable monomer and a photoinitiator are mixed and stirred, and then a prepolymer in a syrup state is prepared by irradiating ultraviolet rays under a nitrogen atmosphere. The prepolymer syrup is generally formed by polymerization of photocurable monomers. Specifically, a monomer for forming the photocurable adhesive resin and a photoinitiator are mixed, if necessary, additives are added, and then photopolymerized partially by irradiation with light to form a syrup state.

After preparing an adhesive composition in which the syrup prepolymer is mixed with a photoinitiator for primary curing and a photoinitiator for secondary curing, the adhesive composition is irradiated with light to first cure it to obtain a semi-cured adhesive tape, Thereafter, the adhesive tape in a semi-cured state is attached to the substrate and then completely cured by irradiating light again.

The optically transparent adhesive tape of the present invention may be used in a semi-cured state, and has excellent step absorption properties, and thus may be adhered to a substrate having a step difference of 60 to 100 μm. And when the light is irradiated secondarily to completely bond the substrate and the optically transparent adhesive tape, the adhesive composition in the semi-cured state is secondarily photocured, and the adhesive tape is completely cured while being adhered to the substrate. The adhesive tape is adhesive.

Hereinafter, the optically transparent adhesive composition according to the present invention will be described in more detail.

The adhesive composition of the present invention is not particularly limited and used as long as it is a polymer that is polymerized and crosslinked with a polymer upon irradiation with light. Preferably, a material including a compound having at least one unsaturated double bond and a photopolymerization initiator may be used.

Preferred examples of the compound having one or more unsaturated double bonds are acrylic compounds.

The acrylate-based compound is 2-ethylhexyl acrylate (2-EHA), ethylhexylmethyl acrylate (EHMA), isobornyl acrylate (IBoA), isostearyl acrylate (ISTA), 4-hydroxy Including at least one selected from acrylate monomers including butyl acrylate (4-HBA), hydroxyethyl acrylate (HEA), butyl acrylate, hexyl acrylate, n-octyl acrylate and isooctyl acrylate I can.

In the present invention, in order to increase the polymerization yield, a photoinitiator is mixed with the photopolymerizable monomer, and if necessary, additives are added, followed by irradiation with light to partially photopolymerize the prepolymer in a syrup state.

The optically transparent composition of the present invention is gradually prepared by adding and mixing a photoinitiator for primary curing and a photoinitiator for secondary curing to the prepolymer syrup. The prepolymer syrup may have a weight average molecular weight of 1,000,000 to 3,000,000, more preferably 1,300,000 to 2,500,000, and most preferably 1,500,000 to 2,000,000. If the weight average molecular weight is less than 1,000,000, it takes a long time during subsequent photocuring and thus productivity may decrease, and if it exceeds 3,000,000, the blending performance may decrease when preparing the adhesive composition, which is not preferable.

The photoinitiator for primary curing is 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1,2,2-dimethoxy-1,2-diphenylethan-1-one , 1-hydroxy-cyclohexylphenyl-ketone, 2-methyl-1-(4-(methylthio)phenyl)-2-morpholinopropanone-1,2,4-diethylthioxanthone, 2-ethyl At least one selected from aromatic ketones of anthraquinone and phenanthrenequinone may be used, and in particular, 1-hydroxy-cyclohexylphenyl-ketone is preferable.

The photoinitiator for secondary curing may include acetophenone, benzophenone, Michler's ketone, benzoin, benzyl methyl ketal, benzoyl bezoade, and the like, but benzophenone is preferable, and in particular, in terms of durability improvement, acryloyl benzo One selected from the group consisting of phenone, acryloylethyl benzophenone and acryloyloxy benzophenone is preferred.

In the adhesive composition, the composition of the prepolymer syrup, the photoinitiator for the primary curing, and the photoinitiator for the secondary curing are 100 parts by weight of the prepolymer syrup, 0.3 to 0.9 parts by weight of the photoinitiator for the primary curing, and the photoinitiator for the secondary curing 0.2 It is preferably included in a ratio of 0.9 parts by weight. If the content of the photoinitiator for primary curing is less than 0.2 parts by weight, processability may be deteriorated, and if the content of the photoinitiator for secondary curing is less than 0.2 parts by weight, the step recovery may be deteriorated.If the photoinitiator for secondary curing is less than 0.2 parts by weight, the heat resistance and workability It may fall, and if the photoinitiator for secondary curing exceeds 0.9 parts by weight, adhesion performance may be deteriorated, which is not preferable.

Hereinafter, a method of manufacturing the optically transparent adhesive tape of the present invention will be described in detail.

First, an adhesive composition constituting an adhesive layer of an adhesive tape is prepared. As described above, the adhesive composition may be initiated by firstly irradiating a mixture of a photopolymerizable monomer and a photoinitiator for partial polymerization to prepare a syrup prepolymer.

Thereafter, the photoinitiator for primary curing and the photoinitiator for secondary curing are added to the prepolymer syrup to obtain a sufficiently stirred adhesive composition. After the adhesive composition is applied on a transparent film such as polyethylene terephthalate, the adhesive composition is primarily irradiated with light to obtain an adhesive tape in a semi-cured state.

At this time, in the step of primary curing, it is preferable to irradiate an amount of light of 0.8 to 1.3 J/cm 2. When irradiating a light amount of less than 0.8 J/cm 2, sufficient photocuring may not be possible, and when an amount of light exceeding 1.3 J/cm 2 is irradiated, curing may proceed too much and the step absorption performance may be degraded, which is not preferable.

After the adhesive tape in a semi-cured state is adhered to the substrate, the adhesive tape is completely cured so that the adhesive tape adheres to the substrate, and the amount of light irradiated at this time is preferably 3 to 5 J/cm 2. When irradiating an amount of light less than 3 J/㎠, durability may be deteriorated, and if an amount of light exceeding 5 J/cm2 is irradiated, adhesion performance may be degraded, which is not preferable.

In the optical adhesive tape of the present invention manufactured by the above method, after the first curing, the gel fraction of the adhesive layer is 30-50%. It is more preferable to control the gel fraction of the pressure-sensitive adhesive layer after the primary curing to 35 to 45% from the viewpoint of step absorption.

The adhesive tape according to the present invention may be used for an optical member such as a touch panel or a display panel, but is not limited thereto, and any application requiring printing step absorption is not particularly limited and may be used.

Hereinafter, the present invention will be described in more detail by examples and comparative examples. However, the present invention is not limited by the following examples.

Preparation Example-Preparation of prepolymer syrup

As a photopolymerizable monomer, 40 parts by weight / 10 parts by weight / 30 parts by weight / 20 parts by weight of each of 2-EHA / EHMA / IBOA / HEA are used, and the photoinitiator 1-hydroxy-cyclohexylphenyl-ketone (Irgacure 184) After adding 0.05 parts by weight, it was put into an old flask and subjected to partial photopolymerization by irradiating UV rays for 15 minutes under a nitrogen atmosphere. At this time, the acrylic polymer syrup is a prepolymer with a polymerization rate of 10% and a weight average molecular weight (Mw) of 2 million.

Example 1

To 100 parts by weight of the prepolymer syrup of Preparation Example, 0.3 parts by weight of the primary photoinitiator 1-hydroxy-cyclohexylphenyl-ketone (Irgacure 184) and 0.2 parts by weight of the secondary photoinitiator acryloyl benzophenone were added, and then the pressure-sensitive adhesive composition was added. Blended. It was first cured. Then, the adhesive layer of the adhesive tape was completely cured by irradiating the light amount of 3 J/cm 2 using an LED and performing secondary curing.

Examples 2 to 6

In Example 1, an adhesive tape was prepared in the same manner as in Example 1, except that the composition of the adhesive composition was changed as shown in Table 1.

Comparative Example 1

To 100 parts by weight of the prepolymer syrup of Preparation Example, 0.3 parts by weight of the primary photoinitiator 1-hydroxy-cyclohexylphenyl-ketone (Irgacure 184) and 0.6 parts by weight of HDDA (Hexanediol diacrylate) were added, and then the adhesive composition was mixed. Thereafter, the pressure-sensitive adhesive composition was coated to a thickness of 150 μm on the polyethyleterephthalate film. The coated adhesive composition was cured by irradiation with a light amount of 3J/cm2 using a black light bulb.

Comparative Examples 2 to 3

In Example 1, an adhesive tape was prepared in the same manner as in Example 1, except that the composition of the adhesive composition was changed as shown in Table 1.

Primary photoinitiator (parts by weight) Secondary photoinitiator
(Part by weight) ABP AEBP AOBP Example 1 0.3 0.2 - - Example 2 0.5 0.2 - - Example 3 0.5 0.5 - - Example 4 0.5 0.7 - - Example 5 0.5 - 0.5 - Example 6 0.5 - - 0.5 Comparative Example 1 0.3 - - - Comparative Example 2 0.5 1.0 - - Comparative Example 3 1.0 0.5 - -

Experimental Example 1-Measurement of gel fraction

For the adhesive tapes of the Examples and Comparative Examples, samples were collected after the first curing and after the second curing, and the gel fraction of each sample was measured.

In the measurement of the gel fraction, the mass of the adhesive layer is accurately measured, immersed in toluene for 24 hours, and then filtered through a 200 mesh wire mesh. Thereafter, the filtrate was dried at 100° C. for 1 hour, the mass of the residue was accurately measured, and the gel fraction of the adhesive layer was calculated from the following equation.

Gel fraction (%) = insoluble partial mass (g) / adhesive layer mass (g) × 100

Experimental Example 2 Measurement of Modulus

For the adhesive tapes of the Examples and Comparative Examples, samples were taken after the first curing and after the second curing, and the modulus was measured, and the results are shown in Table 2.

Modulus was measured at 30° C. using a modulus meter ARES G2.

Experimental Example 3-Evaluation of printing step absorbency

In the manufacture of the adhesive tapes according to the Examples and Comparative Examples, after the first curing, it was attached to a glass substrate having a printing step of 100 μm, and the step absorbency was evaluated. The evaluation of the level difference absorption was evaluated by whether the adhesive film was lifted or bubbled. When the lifted or bubbled little occurred, the leveled absorption was considered to be excellent. "○"; When a lot of bubbles or bubbles are generated, it is indicated as "Х" and the results are shown in Table 2 below.

Experimental Example 4-Durability evaluation

For each of the adhesive tapes of the Examples and Comparative Examples, a sample was prepared by cutting into 10 cm in width and length. The sample was adhered to the non-tin surface of alkali-free glass washed with acetone with a pressing roll, left in an atmosphere of 80°C and 85%RH for 250 hours, then taken out under an atmosphere of 23°C and 50%RH, and the state of the adhesive tape after 1 hour By observing the durability was judged.

○: There is no peeling and foaming of the adhesive tape.

?: Peeling and foaming have occurred in part of the adhesive tape.

X: Peeling and foaming have occurred over the entire adhesive tape.

Gel fraction (%) Modulus (Pa) Step absorption durability 1st hardening Secondary hardening 1st hardening Secondary hardening Example 1 35 63.5 63280 70540 O △ Example 2 35.9 69.4 53810 55080 O △ Example 3 40.2 82.6 69810 88610 O O Example 4 40.2 82.6 69810 88610 O O Example 5 40 81.3 74000 80000 O O Example 6 32 78 75000 81000 O O Comparative Example 1 95 95210 X X Comparative Example 2 53.4 83.7 85210 109300 △ X Comparative Example 3 56.5 84.5 83200 102370 △ X

The adhesive tapes of the examples in which the dual curing method was introduced as described above has much superior step absorption and durability compared to Comparative Example 1, which is not.

Comparative Examples 2 and 3, in which the composition of the secondary photoinitiator was 1.0 part by weight, showed a tendency to be inferior in step absorption properties compared to the adhesive tapes of Examples. In addition, Examples 3 to 6 are more durable compared to Examples 1,2, the adhesive composition constituting the adhesive tape of the present invention, the content of the photoinitiator, 0.5 to 0.7 parts by weight based on 100 parts by weight of prepolymer syrup It can be seen that this is the most preferable range.

Claims (6)

It is prepared from an optically transparent adhesive composition comprising a prepolymer syrup obtained by partially polymerizing an acrylate-based compound and a photoinitiator, a photoinitiator for primary curing, and a photoinitiator for secondary curing,
The optically transparent adhesive composition is first cured to maintain a semi-cured state,
After being adhered to a substrate having a step in a semi-cured state, it is completely cured by secondary curing,
The photoinitiator for primary curing is 1-hydroxy-cyclohexylphenyl-ketone,
The photoinitiator for secondary curing is one selected from the group consisting of acryloyl benzophenone, acryloyl ethyl benzophenone, and acryloyloxy benzophenone,
The gel fraction after the first curing is 32 to 40.2%,
Optically transparent adhesive tape having a step absorption property having a gel fraction of 63.5 to 82.6% after secondary curing.
delete The method of claim 1,
Optically transparent adhesive tape, characterized in that adhered to a substrate having a printing step of 60 ~ 100㎛.
The method of claim 1,
The optically transparent adhesive composition, an optically transparent adhesive tape having step absorption, characterized in that it comprises 100 parts by weight of the prepolymer syrup, 0.3 to 0.9 parts by weight of a photoinitiator for primary curing, and 0.2 to 0.9 parts by weight of a photoinitiator for secondary curing .
As a method of manufacturing the optically transparent adhesive tape of claim 1,
Preparing a prepolymer syrup obtained by partially polymerizing an acrylate compound and a photoinitiator;
Preparing an optically transparent adhesive composition by adding and mixing a photoinitiator for primary curing and a photoinitiator for secondary curing to the prepolymer syrup;
First curing the optically transparent adhesive composition; And
Secondary curing the first cured optically transparent adhesive composition; Including,
The photoinitiator for primary curing is 1-hydroxy-cyclohexylphenyl-ketone,
The photoinitiator for secondary curing is one selected from the group consisting of acryloyl benzophenone, acryloyl ethyl benzophenone, and acryloyloxy benzophenone,
The gel fraction after the first curing is 32 to 40.2%,
A method for producing an optically transparent adhesive tape having a gel fraction of 63.5 to 82.6% after secondary curing.
The method of claim 5,
In the first curing step, a light amount of 0.8 to 1.3 J/cm 2 is irradiated, and in the second curing step, a light amount of 3 to 5 J/cm 2 is irradiated. .