Pressure-sensitive adhesive composition for foldable display

Abstract

The present application relates to a pressure-sensitive adhesive composition for a foldable display and a use thereof. The pressure-sensitive adhesive composition of the present application has excellent bending reliability, and also excellent adhesive force and cohesive force.

Claims

1. A pressure-sensitive adhesive composition for a foldable display comprising: a first pressure-sensitive adhesive comprising a first silicone gum and a first MQ resin, and having a peel force on a glass substrate of 10 gf/in or less, as measured at a peel rate of 0.3 m/min and a peel angle of 180 degrees; a second pressure-sensitive adhesive comprising a second silicone gum and a second MQ resin and having a peel force on a glass substrate of 200 gf/in to 400 gf/in, as measured at a peel rate of 0.3 m/min and a peel angle of 180 degrees; and any one additive selected from the group consisting of a borane compound, a borate compound and a mixture thereof, and wherein MQ resin is a silicone compound having at least a three-dimensional reticular steric molecular structure comprising a monofunctional siloxane unit (M Unit) and a tetrafunctional siloxane unit (Q unit).

2. The pressure-sensitive adhesive composition for a foldable display according to claim 1, wherein a peel force of a pressure-sensitive adhesive layer formed by curing the pressure-sensitive adhesive composition on a glass substrate, as measured at a peel rate of 0.3 m/min and a peel angle of 180 degrees is 20 gf/in or more.

3. The pressure-sensitive adhesive composition for a foldable display according to claim 1, wherein the first or second silicone gum is represented by Formula 1 below: ##STR00005## wherein, R.sup.1 and R.sup.6 are each independently a silyl group or silanol group with or without an alkyl group, an alkenyl group or an aryl group, R.sup.2 to R.sup.5 are each independently an alkyl group, an alkenyl group or an aryl group, and n and m are each independently an integer in a range of 1 to 10,000.

4. The pressure-sensitive adhesive composition for a foldable display according to claim 1, wherein the first pressure-sensitive adhesive comprises the first MQ resin in a content of less than 5 wt %.

5. The pressure-sensitive adhesive composition for a foldable display according to claim 1, wherein the first silicone gum has a number average molecular weight in a range of 400,000 to 800,000.

6. The pressure-sensitive adhesive composition for a foldable display according to claim 1, wherein the first silicone gum has a vinyl group content in a range of 0.5 to 1 mol %.

7. The pressure-sensitive adhesive composition for a foldable display according to claim 1, wherein the first pressure-sensitive adhesive is contained in a range of 5 wt % to 50 wt % relative to the total solid content of the composition.

8. The pressure-sensitive adhesive composition for a foldable display according to claim 1, wherein the second pressure-sensitive adhesive comprises the second MQ resin in a content of 40 wt % or less.

9. The pressure-sensitive adhesive composition for a foldable display according to claim 1, wherein the second silicone gum is a linear polydimethylsiloxane containing hydroxy groups at both ends.

10. The pressure-sensitive adhesive composition for a foldable display according to claim 1, wherein the borane compound is represented by Formula 3 below: ##STR00006## wherein, R.sup.4 to R.sup.6 are each independently hydrogen, halogen, an alkyl group having 1 to 6 carbon atoms, or a silyl group.

11. The pressure-sensitive adhesive composition for a foldable display according to claim 1, wherein the borate compound is represented by Formula 4 below: ##STR00007## wherein, R.sup.7 to R.sup.9 are each independently hydrogen, halogen, an alkyl group having 1 to 6 carbon atoms, or a silyl group.

12. The pressure-sensitive adhesive composition for a foldable display according to claim 1, wherein the additive is contained in a range of 0.01 to 5 wt % relative to the total solid content of the pressure-sensitive adhesive composition.

13. The pressure-sensitive adhesive composition for a foldable display according to claim 1, wherein a storage elastic modulus (G) after curing is 510.sup.6 Pa or less within a temperature range of 40 C. to 90 C.

14. A foldable display comprising a pressure-sensitive adhesive layer which is a cured product of a pressure-sensitive adhesive composition for a foldable display of claim 1 attached to an adherend.

15. The foldable display according to claim 14, wherein the pressure-sensitive adhesive layer has a peel force on the adherend of 2,000 gf/in or more, as measured at a peel rate of 0.3 m/min and a peel angle of 180 degrees.

Description

MODE FOR INVENTION

(1) Hereinafter, the pressure-sensitive adhesive composition for a foldable display according to the present application and the display comprising the same will be described in detail with reference to Examples and Comparative Examples, but the following examples are only examples according to the present application, and thus do not limit the technical idea of the present application.

(2) The physical properties of the pressure-sensitive adhesive composition of the present application were evaluated by the following methods.

(3) 1. Measurement of Storage Elastic Modulus

(4) A pressure-sensitive adhesive composition prepared in Examples and Comparative Examples was coated between release films and cured, and then tailored to a size of 15 cm25 cm, and laminated several times to have a thickness of about 1 mm, after removing the release film on one side. Subsequently, the laminate was tailored into a circle having a diameter of 8 mm and compressed using glass, and then a sample was prepared by allowing the laminate to stand overnight to improve wetting at the interfaces between the layers and removing bubbles generated upon lamination. Subsequently, the sample was placed on a parallel plate, the gap was adjusted, the zero point of Normal & Torque was set, and the storage elastic modulus was measured after confirming stabilization of Normal force.

(5) (1) Measuring instruments and measuring conditions

(6) Measuring instrument: ARES-RDA equipped with a forced convection oven, TA Instruments Inc. (G2 series Rheometer)

(7) (2) Measurement conditions

(8) Geometry: 8 mm parallel plate

(9) Interval: about 1 mm

(10) Test type: dynamic strain frequency sweep

(11) Strain=0.1 [%]

(12) Initial temperature: 40 C., final temperature: 90 C.

(13) Frequency: 6.2 rad/s

(14) 2. Peel Force Measurement

(15) The pressure-sensitive adhesive layer prepared according to Examples and Comparative Examples was attached to a glass substrate or a surface-treated PI base film as an adherend and then aged under a condition of 50 C. and 5 atm for 1 hour or at room temperature for 3 days. After aging, the peel force was measured at a peel rate of 0.3 m/min and a peel angle of 180 degrees at room temperature using a tensile tester (Texture Analyzer).

Example 1

(16) Preparation of Pressure-Sensitive Adhesive Composition (A1)

(17) A first pressure-sensitive adhesive comprising a first polysiloxane gum with a vinyl group content of 0.5 mol % and a number average molecular weight of about 600,000, and about 0.001 wt % of a MQ resin with a structure of Formula 2 (R is an alkyl group having 1 to 2 carbon atoms), and having a peel force on a glass substrate of about 2 gf/in, and a second pressure-sensitive adhesive comprising a second polysiloxane silicone gum containing hyroxy groups at both ends and having a number average molecular weight of 700,000, and about 38 wt % of the MQ resin, and having a peel force on a glass substrate of about 337 gf/in were mixed with triethyl borate and a solvent, but a pressure-sensitive adhesive composition (A1) prepared by adjusting the content of the first pressure-sensitive adhesive to about 10 wt % of the total solid content of the composition and adjusting the content of triethyl borate to 1 wt % relative to the total content of the composition.

(18) Formation of Pressure-Sensitive Adhesive Layer (B1)

(19) The pressure-sensitive adhesive composition (A1) was coated on the primer-treated PET base material and cured to form a pressure-sensitive adhesive layer (B1), where the pressure-sensitive adhesive layer (B1) was subjected to surface modification.

Example 2

(20) A pressure-sensitive adhesive composition (A2) was prepared in the same manner as in Example 1, except that the content of triethyl borate was changed to 2 wt % relative to the total solid content of the composition, and a pressure-sensitive adhesive layer (B2) was formed using the same and subjected to surface modification.

Example 3

(21) A pressure-sensitive adhesive composition (A3) was prepared in the same manner as in Example 1, except that the content of the first pressure-sensitive adhesive was adjusted to about 30 wt % of the total solid content of the composition and the content of triethyl borate was adjusted to 1 wt % relative to the total solid content of the composition, and a pressure-sensitive adhesive layer (B3) was formed using the same and subjected to surface modification.

Comparative Example 1

(22) A pressure-sensitive adhesive composition (A4) was prepared in the same manner as in Example 1, except that triethyl borate was not included, and a pressure-sensitive adhesive layer (B4) was formed using the same and subjected to surface modification.

Comparative Example 2

(23) A pressure-sensitive adhesive composition (A5) was prepared in the same manner as in Example 3, except that triethyl borate was not included, and a pressure-sensitive adhesive layer (B5) was formed using the same and subjected to surface modification.

Experimental Example 1Measurement of Peel Force on Glass Substrate or PI Base Film

(24) The peel forces of the pressure-sensitive adhesive layers according to Examples 1 to 3 and Comparative Examples 1 and 2 on a glass substrate or a PI base film were measured, and the results were shown in Table 1 below.

(25) TABLE-US-00001 TABLE 1 Comparative Example Example 1 2 3 1 2 Peel_force on glass substrate 32 32 28 10 8 (gf/in) Peel force on PI base film 2,737 2,666 2,400 44 22 (gf/in)

(26) As described in Table 1 above, it could be confirmed that when the pressure-sensitive adhesive layers were formed using the pressure-sensitive adhesive compositions according to Examples 1 to 3 of the present application, they had excellent adhesive forces on the glass substrate or the PI base film, but in the case of the pressure-sensitive adhesive layers according to Comparative Examples 1 and 2, they were not suitable as a pressure-sensitive adhesive composition for a foldable display due to low pressure-sensitive adhesive forces.

Experimental Example 2Measurement of Storage Elastic Modulus

(27) In order to examine the storage elastic modulus change rate depending on temperatures after curing of the compositions according to Examples 1 to 3, the storage elastic modulus at 40 C. and 90 V was measured according to the above-described measuring method using an ARES-RDA, an equipment of TA instruments, equipped with a forced convection oven and the results were shown in Table 2.

(28) TABLE-US-00002 TABLE 2 Example 1 Example 2 Example 3 Storage elastic modulus at 1.8 10.sup.5 Pa 1.8 10.sup.5 Pa 1.8 10.sup.5 Pa 40 C. (Pa) Storage elastic modulus at 1.1 10.sup.5 Pa 1.1 10.sup.5 Pa 1.7 10.sup.5 Pa 90 C. (Pa)