WO2020111338A1 - Optical clear adhesive tape having improved level difference absorbability and manufacturing method therefor - Google Patents

Abstract

The present invention relates to an optical clear adhesive tape. The optical clear adhesive tape is prepared from an optical clear adhesive composition comprising: a prepolymer syrup in which an acrylate-based compound and a photoinitiator are partially polymerized; a primary curing photoinitiator; and a secondary curing photoinitiator. The optical clear adhesive composition is primarily cured to be maintained in a semi-cured state. The optical clear adhesive composition in a semi-cured state is applied to a substrate having a step and then completely cured by secondary curing, whereby the resulting optical clear adhesive tape has level difference absorbability. The optical adhesive tape of the present invention has excellent level difference absorbability and durability.

Description

Optical transparent adhesive tape with improved step absorption and manufacturing method

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

Recently, optically transparent adhesive tapes are 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 laminated to a conductive glass, a reinforcing material or a deco film, etc. via an adhesive layer coated with an adhesive composition on a film such as polyethylene terephthalate.

At this time, when a printing portion is formed on a conductive glass, a reinforcing material, or a deco film, when a transparent adhesive tape is laminated on the printing portion, a step equal to the height of the printing portion occurs, and thus a light bending phenomenon occurs in the step portion. do.

Therefore, there is a need to develop a technology for an optically transparent adhesive tape with improved step absorbability that can overcome such steps.

The first object of the present invention is to provide a transparent adhesive tape having improved step absorption performance in a printing section.

A second object of the present invention is to provide an optically transparent adhesive tape that does not deteriorate durability while improving the 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 partially polymerized with an acrylate compound and a photoinitiator, a photoinitiator for primary curing, and a photoinitiator for secondary curing. , The optically transparent adhesive composition is an optically transparent adhesive tape having a step absorbency that is cured by primary curing, adhered to a substrate having a step in a semi-cured state, and then completely cured by secondary curing.

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

In one embodiment of the present invention, the primary curing photoinitiator is 1-hydroxy-cyclohexylphenyl-ketone (1-hydroxy-cyclohexylphenyl ketone), and the secondary curing photoinitiator is acryloyl benzophenone, acrylic It is preferably one selected from the group consisting of monoethyl benzophenone and acryloyloxy benzophenone.

In one embodiment of the present invention, it is preferable that the optically transparent adhesive composition includes 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 the optically transparent adhesive tape of the present invention comprises the steps of preparing a prepolymer syrup partially polymerized with an acrylate-based compound and a photoinitiator; Preparing an optically transparent adhesive composition by adding and blending 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 primary cured optically transparent adhesive composition. It characterized in that it comprises.

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 second 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 an excellent step absorbency and durability.

Hereinafter, the present invention will be described in detail with reference to examples and drawings of the present invention. These examples are only provided by way of example to illustrate the present invention in more detail, it will be apparent to those skilled 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 partially polymerized with an acrylate compound and a photoinitiator, a photoinitiator for primary curing and a photoinitiator for secondary curing, and the optically transparent adhesive composition This is an optically transparent adhesive tape having a step absorbency that is cured by primary curing, and then adhered to a substrate having a step in a semi-cured state and then completely cured by secondary curing.

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

That is, through the double photo-curing method, after the primary 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 secondary curing, the gel fraction of the adhesive layer is 60%. By controlling the above, it was prevented that the durability was lowered.

In the present invention, first, a photopolymerizable monomer and a photoinitiator are mixed and stirred, and then ultraviolet light is irradiated under a nitrogen atmosphere to prepare a syrup prepolymer. The prepolymer syrup is usually formed by polymerization of photocurable monomers. Specifically, a monomer and a photoinitiator for forming the photocurable adhesive resin are mixed, and if necessary, an additive is added, followed by irradiation with light to partially photopolymerize to make a syrup state.

After preparing an adhesive composition in which the prepolymer in the syrup state is mixed with a photoinitiator for primary curing and a photoinitiator for secondary curing, when the primary composition is irradiated with light to irradiate the adhesive composition, a semi-cured adhesive tape is obtained. Subsequently, the semi-cured adhesive tape is attached to the substrate to complete curing by irradiating light again.

The optically transparent adhesive tape of the present invention can be used in a semi-cured state, and can be adhered to a substrate having a step difference of 60 to 100 µm due to excellent step absorption. In addition, when light is irradiated secondary to completely adhere the substrate and the optically transparent adhesive tape, the semi-cured adhesive composition is second-cured to the second, and the adhesive tape is fully cured in the adhesive state on the substrate, and then the substrate And the adhesive tape are 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 as long as it is a polymer that is polymerized and crosslinked with a polymer upon light irradiation. Preferably, a compound containing 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), ethylhexyl methyl acrylate (EHMA), isobornyl acrylate (IBoA), isostearyl acrylate (ISTA), 4-hydroxy Butyl acrylate (4-HBA), hydroxyethyl acrylate (HEA), butyl acrylate, hexyl acrylate, n- octyl acrylate, and at least one selected from acrylate monomers including isooctyl acrylate. Can be.

In order to increase the polymerization yield, the present invention may be subjected to a process of preparing a prepolymer in a syrup state by mixing a photoinitiator with the photopolymerizable monomer, adding an additive if necessary, and partially photopolymerizing by irradiating light.

To the prepolymer syrup, a photoinitiator for primary curing and a photoinitiator for secondary curing are added and mixed to prepare an optically transparent composition of the present invention. The prepolymer syrup preferably has 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. When the weight average molecular weight is less than 1,000,000, it takes a long time for subsequent photocuring, so productivity may drop, and when it exceeds 3,000,000, it is not preferable because the mixing performance may decrease when preparing the adhesive composition.

The primary curing photoinitiator 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 One or more selected from aromatic ketones of anthraquinone and phenanthrenequinone can be used, and 1-hydroxy-cyclohexylphenyl-ketone is particularly preferred.

The secondary curing photoinitiator may include acetophenone, benzophenone, mihila ketone, benzoin, benzyl methyl ketal, benzoyl bezoade, etc., but benzophenone is preferred, and in particular, acryloyl benzo in terms of improving durability. Phenone, acryloylethyl benzophenone and acryloyloxy benzophenone are preferably one selected from the group consisting of.

In the adhesive composition, the composition of the prepolymer syrup, the photoinitiator for primary curing and the photoinitiator for secondary curing, 100 parts by weight of the prepolymer syrup, 0.3 to 0.9 parts by weight of the photoinitiator for primary curing, and the photoinitiator for secondary curing 0.2 It is preferably included in a proportion of 0.9 parts by weight. If the content of the primary curing photoinitiator is less than 0.2 parts by weight, the workability may be deteriorated, and if it exceeds 0.9 parts by weight, the step yieldability may deteriorate. When the secondary curing photoinitiator is less than 0.2 parts by weight, heat resistance and workability It may fall off, and if the photoinitiator for secondary curing exceeds 0.9 parts by weight, the adhesive performance may deteriorate, 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 the adhesive layer of the adhesive tape is prepared. As described above, the adhesive composition may be started from partial polymerization by first irradiating a mixture of a photopolymerizable monomer and a photoinitiator to prepare a syrup prepolymer.

Then, to the prepolymer syrup, the primary curing photoinitiator and the secondary curing photoinitiator are added to obtain a sufficiently stirred adhesive composition. After the adhesive composition is applied onto a transparent film such as polyethylene terephthalate, the adhesive composition is first irradiated with light to obtain a semi-cured adhesive tape.

At this time, in the first curing step, it is preferable to irradiate a light amount of 0.8 to 1.3 J/cm 2. When irradiating a light amount of less than 0.8 J/cm2, sufficient photocuring may not be achieved, and when irradiating a light amount of more than 1.3 J/cm2, curing proceeds too much and the step absorption performance may be deteriorated, which is not preferable.

After adhering the semi-cured adhesive tape on the substrate, the adhesive tape is completely cured so that the adhesive tape is adhered to the substrate, and the amount of light irradiated is preferably 3 to 5 J/cm 2. When irradiating a light amount of less than 3 J/cm 2, durability may be deteriorated, and when irradiating a light amount of more than 5 J/cm 2, adhesive performance may deteriorate, which is not preferable.

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

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 may be used without particular limitation as long as it is an application requiring absorption of a printing step.

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, 2-EHA / EHMA / IBOA / HEA each using 40 parts by weight/10 parts by weight/30 parts by weight/20 parts by weight, and photoinitiator 1-hydroxy-cyclohexylphenyl-ketone (Irgacure 184) After adding 0.05 parts by weight, the mixture was put into an old flask and partially photopolymerized by irradiating ultraviolet light 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

After adding 100 parts by weight of the prepolymer syrup of the 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, and then adding an adhesive composition It was compounded. Primary curing. Thereafter, the amount of light of 3 J/cm 2 was irradiated using an LED to completely cure the adhesive layer of the adhesive tape by secondary curing.

Examples 2 to 6

In Example 1, except for changing the composition of the pressure-sensitive adhesive composition as shown in Table 1, an adhesive tape was prepared in the same manner as in Example 1.

Comparative Example 1

100 parts by weight of the prepolymer syrup of the above 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, followed by mixing the pressure-sensitive adhesive composition. Thereafter, the pressure-sensitive adhesive composition was coated on a polyethylreterphthalate film to a thickness of 150 μm. The coated adhesive composition was cured by irradiating a light amount of 3J/cm 2 using a black light bulb.

Comparative Examples 2 to 3

In Example 1, except for changing the composition of the pressure-sensitive adhesive composition as shown in Table 1, an adhesive tape was prepared in the same manner as in Example 1.

	Primary photoinitiator (parts by weight)	Secondary photoinitiator (parts 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 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.

The measurement of the gel fraction accurately measures the mass of the adhesive layer, is 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, and the mass of the residue was accurately measured to calculate the gel fraction of the adhesive layer 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 Examples and Comparative Examples, samples were collected after primary curing and after secondary curing, respectively, and modulus was measured, and the results are shown in Table 2.

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

Experimental Example 3 Evaluation of Printed Level Absorption

When preparing the adhesive tapes according to Examples and Comparative Examples, after the primary curing, the printing step was attached to a glass substrate having a thickness of 100 μm, and the step absorbency was evaluated. The evaluation of the level absorbency was evaluated by the presence or absence of air bubbles or air bubbles in the adhesive film. When the level of water absorption or air bubbles is little, the level of water absorption is excellent. When a lot of 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 Examples and Comparative Examples, samples were cut by cutting to 10 cm in width. The sample was adhered to a non-tinned surface of an alkali-free glass cleaned with acetone with a pressing roll, left under an atmosphere of 80°C and 85%RH for 250 hours, and then taken out under an atmosphere of 23°C and 50%RH, and after 1 hour, the state of the adhesive tape It was observed to determine the durability.

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

(Triangle|delta): Peeling and foaming generate|occur|produced in a part of adhesive tape.

X: Peeling and foaming were generated in the entire adhesive tape.

	Gel fraction (%)		Modulus (Pa)		Step absorbency	durability
	1st hardening	2nd hardening	1st hardening	2nd 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

As described above, the adhesive tapes of the embodiments incorporating the double curing method have much better step absorbency and durability than 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 drop in step absorbency compared to the adhesive tape of the Examples. In addition, since Examples 3 to 6 are more durable than Examples 1 and 2, the adhesive composition constituting the adhesive tape of the present invention has a photoinitiator content of 0.5 to 0.7 parts by weight based on 100 parts by weight of the prepolymer syrup. It can be seen that it is the most preferable range.

Claims (6)

1. It is prepared from an optically transparent adhesive composition comprising a prepolymer syrup partially polymerized with an acrylate compound and a photoinitiator, a photoinitiator for primary curing, and a photoinitiator for secondary curing,

   A semi-cured state is maintained by the primary curing of the optically transparent adhesive composition,

   An optically transparent adhesive tape having a step absorbency that is fully cured by being second-cured after being adhered to a substrate having a step in a semi-cured state.
2. According to claim 1,

   The optically transparent adhesive tape characterized in that the gel fraction after primary curing is 30-50%, and the gel fraction after secondary curing is 60% or more.
3. According to claim 1,

   Optical transparent adhesive tape, characterized in that it adheres to the substrate having a printing step of 60 ~ 100㎛.
4. According to claim 1,

   The optically transparent adhesive composition, the optically transparent adhesive tape having a step absorbency, characterized in that it comprises 100 parts by weight of the prepolymer syrup, 0.3 to 0.9 parts by weight of the photoinitiator for primary curing and 0.2 to 0.9 parts by weight of the photoinitiator for secondary curing .
5. As a method of manufacturing the optically transparent adhesive tape of claim 1,

   Preparing a prepolymer syrup partially polymerized with an acrylate-based compound and a photoinitiator;

   Preparing an optically transparent adhesive composition by adding and blending 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 primary cured optically transparent adhesive composition; Method of manufacturing an optically transparent adhesive tape comprising a.
6. 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, and the method for manufacturing the optically transparent adhesive tape is characterized in that .