KR20180128765A - Optically clear adhesive film and composition for the same and display device using the same - Google Patents

Abstract

The present invention relates to an optical transparent pressure sensitive adhesive sheet comprising a (meth) acrylate syrup which is a resin syrup prepared by partial polymerization of a (meth) acrylate monomer and a photoinitiator, wherein the sheet has a stress relaxation ratio after primary ultraviolet crosslinking Is 0.02 to 0.10, and the stress relaxation ratio after the secondary ultraviolet crosslinking is 0.3 to 0.6 at the same temperature as the temperature of the primary ultraviolet crosslinking, and a flat panel display device and a To provide a composition for making.

Description

TECHNICAL FIELD [0001] The present invention relates to an optical transparent pressure-sensitive adhesive sheet, a composition for producing the same, and a display device using the same. BACKGROUND ART [0002]

The present invention relates to an optical transparent pressure sensitive adhesive sheet, a flat panel display including the same, and a composition for manufacturing the same.

In an image display module of an electronic device such as a mobile portable device, a computer display and a touch panel, a glass or plastic film is laminated as a surface protection layer. This surface protection layer is fixed to the image display module or the touch panel by applying a frame-shaped tape or adhesive to the margin outside the image display portion or outside the active region of the touch panel. As a result, a gap is formed between the image display portion or the active region of the touch panel and the surface protection layer.

In the industry, there has been a trend in the industry to replace the gap between the image display module or the touch panel and the surface protection layer with a transparent material having a refractive index almost identical to those of the material, in order to improve transparency and improve linearity. Exemplary transparent materials include, but are not limited to, optical adhesive films (OCA films), pressure sensitive adhesives, adhesives, and silicone gels. In the case of using an adhesive, for example, when a defect occurs after laminating the surface protective layer and the image display module, it is difficult to separate and replace the surface protective layer. Silicone gels have reliability problems due to their low adhesion. On the other hand, a pressure-sensitive adhesive (for example, a pressure-sensitive adhesive sheet) is capable of re-lamination in spite of a sufficiently high adhesive force, but it is difficult to apply uniformly because it is in a liquid form by a solvent, And the like.

The surface of the adherend such as the image display module, the optical member or the surface protection layer is sometimes uneven. The surface of the surface protective layer, in particular the surface in contact with the adhesive film or the adhesive sheet, is often subjected to a step of printing for decoration or shading purposes. In some cases, the printed portion generates a step having a height of 10 占 퐉 or more on the surface of the surface protective layer. One potential problem in laminating an image display module or a touch panel to a surface protective layer using an optical adhesive film is that the optical adhesive film may not be sufficiently coherent with the edge and that a gap .

In the past, Korean Patent Laid-Open Publication No. 10-2016-0011785 discloses a transparent photocurable pressure-sensitive adhesive composition. However, due to the uneven surface of the adherend, the end filling property and the step difference overcoming are insufficient during bonding, A problem has occurred.

Korean Patent Laid-Open Publication No. 10-2016-0011785

An object of the present invention is to provide an optical transparent pressure sensitive adhesive sheet which is minimized in lifting from the surface of the adherend after curing and has excellent adhesiveness, step difference filling property and durability.

The present invention relates to an optical transparent pressure sensitive adhesive sheet comprising a (meth) acrylic copolymer, a photo initiator and an acrylate monomer, wherein the optical transparent pressure sensitive adhesive sheet has a stress relaxation ratio of 0.02 to 0.10 after primary ultraviolet crosslinking at 70 캜, Wherein the stress relaxation ratio after secondary ultraviolet crosslinking is 0.3 to 0.6 at the same temperature as the temperature of the primary ultraviolet crosslinking.

 The present invention also relates to a composition comprising a (meth) acrylate resin syrup, a photo initiator and a (meth) acrylate monomer which are resin syrups produced by partial polymerization of a (meth) acrylate monomer, ≪ / RTI >

Further, the present invention provides a flat panel display device comprising the optical transparent pressure sensitive adhesive sheet described above.

The present invention is characterized in that the film has a stress relaxation ratio of 0.02 to 0.10 after primary ultraviolet crosslinking at 70 캜 so as to provide excellent end filling property and step difference overcoming property and to provide a stress relaxation after secondary ultraviolet crosslinking at 70 캜 within a range of 0.3 to 0.6 So that lifting from the surface of the adherend is minimized, and an energy curing type inorganic adhesive film excellent in level difference filling and durability can be provided.

The present invention relates to an optical transparent adhesive film and a composition for producing the same. The optical transparent adhesive film of the present invention may be an inorganic material film. In addition, the composition of the present invention may contain a (meth) acrylate copolymer, a photoinitiator and a (meth) acrylate monomer. The optical transparent pressure sensitive adhesive film of the present invention may comprise a (meth) acrylic copolymer, a photoinitiator and an acrylate monomer, and the term 'optical transparent pressure sensitive adhesive film' have. In the optical transparent pressure sensitive adhesive sheet of the present invention made of the composition, the stress relaxation ratio after the first ultraviolet crosslinking at 70 캜 is 0.02 to 0.10, and the second ultraviolet crosslinking ratio is 2 And has a stress relaxation ratio of from 0.3 to 0.6 after crosslinking by ultraviolet ray cross-linking. Thus, end filling property and step difference overcoming property are excellent, and lifting from the surface of the adherend after curing can be minimized.

The present invention relates to a composition comprising a (meth) acrylate resin syrup, a photo-initiator and a (meth) acrylate monomer which are resin syrups produced by partially polymerizing a (meth) acrylate monomer, Wherein the composition of the present invention has a stress relieving ratio of from 0.02 to 0.10 after primary ultraviolet crosslinking at 70 DEG C and a secondary ultraviolet crosslinking at a temperature equal to the temperature of the primary ultraviolet crosslinking When the post stress relieving ratio is in the range of 0.3 to 0.6, it is possible to secure the end filling property and the step difference overcome due to the cohesive force, the adhesion and the durability improvement in the pressure sensitive adhesive, and the lifting phenomenon from the surface of the adherend can be minimized.

Hereinafter, the configuration of the present invention will be described in detail.

( Meta ) Acrylate  syrup

In the present invention, (meth) acrylate means "acrylate", "methacrylate", or both. (Meth) acrylate syrup may contribute to the cohesive force, adhesion and durability of the pressure-sensitive adhesive.

The (meth) acrylate syrup of the present invention may comprise i) an acrylate containing a hydroxy group and ii) a monofunctional (meth) acrylate monomer. When i) the acrylate monomer containing a hydroxy group is included, it can contribute to the improvement of the cohesive force and the adhesion. The type of the acrylate containing the i) hydroxyl group is not limited as long as it contains a hydroxy group, but the alkyl acrylate monomer containing a hydroxy group specifically includes, for example, 2-hydroxyethyl acrylate, 2-hydroxy Propyl acrylate, 4-hydroxybutyl acrylate, 5-hydroxypentyl acrylate, 6-hydroxyhexyl acrylate, 8-hydroxyoctyl acrylate, 2-hydroxyethylene glycol acrylate and 2- Glycol acrylate and the like.

The type of the monofunctional (meth) acrylate monomer is not limited as long as it is a monofunctional monomer known in the art, and specific examples thereof include ethylhexyl (meth) acrylate, dodecyl (meth) Acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isobornyl (meth) acrylate, cyclohexyl (Meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl Acrylate, isooctyl (meth) acrylate, isooctyl (meth) acrylate, lauryl (meth) acrylate, tetradecyl (Meth) acrylate, Acrylates such as acrylic acid, methacrylic acid, 2- (meth) acryloyloxyacetic acid, 3- (meth) acryloyloxypropyl acid, 4- (meth) acryloyloxybutyric acid, 2- Acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl Ethylene glycol (meth) acrylate, 2-hydroxypropylene glycol (meth) acrylate, and the like. More preferably at least one member selected from the group consisting of ethylhexyl (meth) acrylate, dodecyl (meth) acrylate, isobonyl (meth) acrylate and cyclohexyl (meth) acrylate.

The i) acrylate containing a hydroxyl group may be included in an amount of 5 to 20% by weight based on the total weight of the copolymer including i) the acrylate containing a hydroxyl group and the ii) monofunctional (meth) acrylate monomer, and 5 If the amount is less than 10% by weight, cohesive failure may occur under high temperature and / or high humidity conditions, such that endurance reliability may deteriorate. If the amount is more than 20% by weight, the compatibility and wettability may decrease.

In the present invention, the (meth) acrylate syrup may have a weight average molecular weight of 600,000 or more and 1,000,000 or less, and more preferably 600,000 or more and 800,000 or less. When the weight average molecular weight of the (meth) acrylate syrup of the present invention satisfies the above range, the adhesion property, wettability and durability can be expected to be improved.

Photoinitiator

The optical transparent pressure sensitive adhesive sheet of the present invention comprises a photoinitiator to efficiently induce the reaction of the radical polymerizable group.

The photoinitiator is not particularly limited as long as it is a general initiator that can initiate photopolymerization by generating radicals by irradiation with ultraviolet light or the like, and a photopolymerization initiator known in the art can be used. Specific examples thereof include a benzoin-based initiator, a hydroxyketone-based initiator, an amino ketone-based initiator and / or a phosphine oxide-based initiator and more specifically 2,2-dimethoxy-2-paleacetophenone Diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide, Hydroxycyclohexyl phenyl ketone, Hydroxycyclohexyl phenyl ketone, Hydroxymethyl phenyl ketone, benzoylformic acid, 1,4-dibenzoylbenzene, benzyl, and the like.

The photoinitiator includes two or more selected from the group consisting of a polyfunctional benzoyl compound initiator, a benzophenone based initiator, a benzoin based initiator, a hydroxy ketone based initiator, an amino ketone based initiator and / or a phosphine oxide based initiator can do. The multifunctional benzoyl-based initiator reacts with benzoylmorphic acid and Coronate-HXR at a ratio of 1: 1 in an equivalent ratio of 100: 1, and a polyfunctional benzoyl compound can be formed through a urethane bonding reaction. Preferred are polyfunctional benzoyl compounds, benzophenone acrylics (VISIOMER6973, ebonics), 2,2-dimethoxy-2-phenylacetophenone, diphenyl (2,4,6 (2,4,6-trimethylbenzoyl) phosphine oxide, hydroxycyclohexyl phenyl ketone, hydroxymethyl phenyl ketone, benzoyl peroxide, Benzoylformic acid, 1,4-dibenzoylbenzene and / or benzyl, and the like.

The photoinitiator may be added in an amount of 0.2 to 4 parts by weight, more preferably 0.5 to 2 parts by weight, based on 100 parts by weight of the sum of the acrylate monomer containing the hydroxy group and the monofunctional (meth) acrylate monomer.

The amount of the photoinitiator may be 0.2 to 4 parts by weight, more preferably 0.5 to 2 parts by weight based on 100 parts by weight of (meth) acrylate syrup.

When the photoinitiator is included in the above range, the effect is insignificant even though it is added, and properties such as durability, reliability and transparency can be improved.

additive

The process for producing the optical transparent pressure sensitive adhesive sheet of the present invention can be carried out by a method commonly used in this field except for those described above. At this time, molecular weight regulators, isocyanate crosslinking agents, catalysts and the like used in this field can be used without limitation.

The method of applying the optical transparent pressure sensitive adhesive sheet of the present invention is not particularly limited, and after the optical transparent pressure sensitive adhesive sheet is applied, it is cured through light irradiation. In the present application, for example, in the case of applying the ultraviolet ray irradiation method, the ultraviolet ray irradiation can be performed by means of a high-pressure mercury lamp, an electrodeless lamp, or a xenon lamp.

In addition, a suitable aging step may be carried out before or after the light irradiation step to induce the reaction of the functional group of the crosslinking agent in the composition with the thermosetting functional group of the polymer, and the conditions in the process are not particularly limited as long as a proper crosslinking reaction can take place .

The optical transparent pressure sensitive adhesive sheet of the present invention can be obtained by, for example, laminating optical films such as a polarizing film, a retardation film, an anti-glare film, a wide viewing angle compensating film or a brightness enhancement film to each other, Can be used for adhering to the same adherend.

In particular, the optical transparent pressure sensitive adhesive sheet of the present invention can be preferably used for a flexible display device.

In addition, a method for producing an optical transparent pressure sensitive adhesive sheet can be used without limitation in a method known in the art.

There is provided a flat panel display device comprising an optical transparent adhesive inorganic material film formed from the optical transparent adhesive inorganic material composition of the present invention.

It is more preferable that the flat panel display device is a flexible display device.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the following examples are intended to illustrate the present invention, and the present invention is not limited by the following examples, but may be variously modified and changed.

Manufacturing example : ( Meta ) Acrylate  Manufacture of syrups

Manufacturing example  One

(2-EHA) monomer, 25% by weight of ethylhexylmethacrylate (EHMA) monomer, 5% by weight of isobornyl acrylate (EHMA) monomer, A monomer mixture consisting of 30% by weight of an acrylate (IBOA) monomer and 10% by weight of a 2-hydroxyethyl acrylate (2-HEA) monomer was poured into the flask. Then, nitrogen gas was purged for 1 hour to remove oxygen, Respectively. After homogeneously mixing the monomer mixture, 1.0 part by weight of DMPA (2,2-dimethoxy-2-phenylacetophenone) was added as a photoinitiator. Then, the mixture was stirred and irradiated with a UV lamp (10 mW) to prepare a (meth) acrylate syrup having a solid content of 25%.

Manufacturing example  2 to 4

(Meth) acrylate syrup was prepared in the same manner as in Preparation Example 1, but with the composition shown in Table 1 below.

Test Example  One. ( Meta ) Acrylate  Evaluation of weight average molecular weight and molecular weight distribution of syrup

The weight average molecular weight and molecular weight distribution of the (meth) acrylate syrup were measured using GPC under the following conditions. For the preparation of the calibration curve, the measurement results were converted using standard polystyrene of the Agilent system.

 <Conditions for measuring weight average molecular weight>

Meter: Agilent GPC (Agilent 1200 series, USA)

Column: Two PL Mixed B connections

Column temperature: 40 ° C

Eluent: tetrahydrofuran

Flow rate: 1.0 mL / min

Concentration: ~ 1 mg / mL (100 [mu] L injection)

[Table 1]

Example  1 to 4 and Comparative Example  1 to 4

The pressure-sensitive adhesive composition was prepared by mixing the (meth) acrylate syrup and the photoinitiator content of the above Preparation Example in the composition shown in Table 2 below.

The pressure-sensitive adhesive composition prepared above was coated on a releasing film coated with a silicone release agent to a thickness of 150 mu m, and a release film was bonded thereon to produce a pressure-sensitive adhesive sheet.

[Table 2]

Test Example 2 . Adhesion evaluation

A release film on one side of the pressure-sensitive adhesive sheet prepared in the Example or Comparative Example was peeled off, and a 38-μm PET film and a pressure-sensitive adhesive surface were corona-treated and bonded, and then cut to a width of 25 mm and a length of 100 mm. Then, the release film adhered to the PET / pressure-sensitive adhesive layer structure is peeled off, and the pressure-sensitive adhesive sheet is attached to the alkali glass using a roller of 2 kg in accordance with JIS Z 0237. The alkali glass with the adhesive sheet was pressed for about 20 minutes under an autoclave (50 캜, 5 atmospheric pressure), and the sample stored for 1 hour under constant temperature and humidity conditions (23 캜, 50% relative humidity) Analyzer, manufactured by Stable Microsystems, UK), the peeling force is measured while peeling the adhesive sheet from the alkali glass at a peeling speed of 300 mm / min and a peeling angle of 180 degrees.

In addition, the adhesive force of PET is measured by the same method, except that a glass adhered to PET is attached to an alkali glass using a double-sided tape as an adherend. The results are shown in Table 3 below.

Test Example  3. Evaluation of Stress Relaxation Ratio (S / R Ratio)

The pressure-sensitive adhesive sheet produced in Examples or Comparative Examples

Measuring instrument: Rheometer MCR-302, PP25 (25mmΦ)

Measurement conditions: Strain 25%, Axial force 1N

Thickness 500 탆 (5 sheets of 100 탆 overlap)

Temp: 70 캜 (stabilization 10 min)

After the stabilization, the elastic modulus at 70 ° C and the elastic modulus after 300 seconds are checked

S / R Ratio = 70 seconds elastic modulus at 300 seconds / 70 seconds elastic modulus at 1 sec

25mmΦ (PP25), 25% strain, Frequency 1Hz, Axial force 1N,

Temperature 70 占 폚 (70 占 폚 after room temperature bonding, stabilization 5 minutes), measurement thickness 500 占 퐉

G 'at a time of Ratio = 300 seconds, G' at a time of 0.1 second,

The S / R ratio after primary UV cross-linking was A and the S / R ratio after secondary UV cross-linking was B. The results are shown in Table 3 below.

Test Example  4. Step Burial castle

The one side release PET of the pressure-sensitive adhesive film produced by the method described above was peeled off and bonded to a polyethylene terephthalate film (PET100) having a thickness of 100 占 퐉 to produce an adhesive film to which PET100 base material was bonded on one side. The specimens were cut to a length of 50 mm and a width of 40 mm. Next, a 50 占 퐉 -thick polyethylene terephthalate film (PET50) was cut to form a frame of 40 mm in length, 30 mm in width, and 5 mm in width. The mold releasing PET having a thickness of 50 占 퐉 with a cut 50 占 퐉 thickness made of the cut PET50 was bonded on the peeled PET100 so as to be sandwiched with another PET100 (composition of PET100 / pressure-sensitive adhesive / PET50 / PET100). This was subjected to an autoclave treatment for 20 minutes at a pressure of 0.5 MPa in an atmosphere of 50 캜, and then irradiated with 3 J of a metal halide lamp to prepare a sample. Thereafter, the sample was allowed to stand in an atmosphere at a temperature of 80 캜 for 24 hours, and the inside of the frame having a thickness of 50 탆 was observed with a visual observation, and the filling property with respect to the step of thickness of 50 탆 was evaluated as follows. The evaluation results are shown in Table 3 below.

○: There is no mixing of air bubbles

△: There is some air bubbles

X: There is a lot of air bubbles

Test Example  5. Durability (heat resistance, Wet heat )

The release film on one side of the pressure-sensitive adhesive sheet prepared in Example or Comparative Example was peeled off, the 40 mu m COP film and the pressure-sensitive adhesive surface were corona-treated and adhered to each other, and the pressure-sensitive adhesive sheet was cut into a size of 90 mm x 170 mm, A glass substrate (110 mm x 190 mm x 0.7 mm) was attached to prepare a specimen. At this time, the applied pressure was 5 kg / cm &lt; 2 &gt;, and the clean room operation was performed so that bubbles or foreign matter would not occur. The heat resistance characteristics were observed for 500 hours at a temperature of 100 ° C. and then observed for occurrence of bubbles or peeling. The resistance to moisture and heat was measured at 85 ° C. and 85% RH for 500 hours, Respectively.

<Evaluation Criteria>

Ⓞ: No bubbles or peeling.

○: Bubbles or peeling <5

?: 5 pieces? Bubbles or peeling <10 pieces

X: 10 pieces &lt; bubble &

The physical properties of the composition are shown in Table 3 below.

[Table 3]

The stress relaxation ratio of the present invention after primary ultraviolet crosslinking at 70 캜 is 0.02 to 0.10, and the stress relaxation ratio after secondary ultraviolet crosslinking is 0.3 to 0.6 at the same temperature as the temperature of the primary ultraviolet crosslinking The optical transparent pressure-sensitive adhesive sheets of Examples 1 to 5 exhibited very excellent durability and excellent durability means that they had excellent adhesion, and it was confirmed that the adherence was improved and the effect of end landing and step difference overcome was also excellent .

The optical transparent pressure-sensitive adhesive sheets of Examples 1 to 5 showed excellent durability, improved adhesion, and excellent step difference filling property.

On the other hand, the stress relaxation ratio of the present invention after primary ultraviolet cross-linking at 70 캜 is 0.02 to 0.10, and the stress relaxation ratio after secondary ultraviolet cross-linking at the same temperature as the temperature of the primary ultraviolet cross- In Comparative Examples 1 to 4, the durability was poor, and in Comparative Examples 1 and 2, the step coverage was also poor.

Claims (10)

(Meth) acrylate syrup, which is a resin syrup prepared by partially polymerizing a (meth) acrylate monomer, and a photoinitiator,
Wherein the film has a stress relaxation ratio of 0.02 to 0.10 after primary ultraviolet crosslinking at 70 DEG C and a stress relaxation ratio after secondary ultraviolet crosslinking at a temperature equal to the temperature of the primary ultraviolet crosslinking is 0.3 to 0.6 Sensitive adhesive sheet.
The method according to claim 1,
Wherein the photoinitiator is at least two selected from the group consisting of a benzophenone-based initiator, a benzoin-based initiator, a hydroxyketone-based initiator, an amino ketone-based initiator, and a phosphine oxide-based initiator.
The method according to claim 1,
The (meth) acrylate syrup, which is a resin syrup prepared by partially polymerizing a (meth) acrylate monomer, comprises an acrylate monomer containing a hydroxy group; Mono-functional (meth) acrylate monomers; And a photoinitiator.
The method of claim 3,
Wherein the hydroxyl group-containing acrylate monomer is contained in an amount of 5 to 20% by weight based on the total weight of the resin syrup prepared by partially polymerizing the (meth) acrylate monomer.
The method according to claim 1,
Wherein the (meth) acrylate monomer is mono-functional.
The method according to claim 1,
Wherein the photoinitiator is contained in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of (meth) acrylate syrup which is a resin syrup prepared by partially polymerizing the (meth) acrylate monomer.
The method of claim 3,
Wherein the photoinitiator is contained in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the total of the acrylate monomer containing the hydroxy group and the monofunctional (meth) acrylate monomer.
(Meth) acrylate resin syrup, a photo-initiator and a (meth) acrylate monomer, which is a resin syrup prepared by partially polymerizing a (meth) acrylate monomer, &Lt; / RTI &gt;
A flat panel display comprising the optical transparent pressure sensitive adhesive sheet of claim 1.
The method of claim 9,
Wherein the flat panel display device is a flexible display device.