Laminate, method of peeling laminate, and method of manufacturing flexible device

1. A method of peeling a laminate, the method comprising:

forming a first adhesive layer on a first substrate, the first adhesive layer having adhesive force that satisfies the following Expression (1) and one or both of the following Expressions (2) and (3);

firmly attaching a second substrate onto the first adhesive layer;

forming a first functional layer on the second substrate; and

peeling off the first substrate from the second substrate,

A

<

x

2

L

2

+

4

⁢

⁢

x

2

·

(

σ

max

-

6

⁢

⁢

E

·

h

L

2

·

x

)

(

1

)

where “L” is a length of the first substrate in a direction in which the first substrate is peeled off,

“h” is a thickness of the first substrate in millimeter,

“x” is an allowable deformation amount of the first substrate,

“E” is a Young's modulus of the first substrate, and

“σ max ” is a limit bending stress of the first substrate,

B′<C−ρhg   (2)

where “B” is adhesive force between the first substrate and the second substrate at a peeling start part when the peeling is performed,

“C” is peeling force in a vertical direction (in a Z-axis direction) when the peeling is performed,

“ρ” is a density of the first substrate,

“h” is the thickness of the first substrate in millimeter, and

“g” is gravitational constant,

1

=

r

r

-

d

·

d

⁡

(

2

⁢

⁢

r

-

d

)

(

3

)

where “l” is a width of a region in which the peeling is started,

“d” is an amount of projection and warpage of the first substrate, and

“r” is a curvature radius.

2. The method according to claim 1 , wherein the first adhesive layer has the adhesive force that satisfies the Expression (1) and both of the Expressions (2) and (3).

3. The method according to claim 1 , further comprising forming a release layer on a surface, of the second substrate, that is to be firmly attached onto the first adhesive layer, before the firmly attaching of the second substrate onto the first adhesive layer.

4. The method according to claim 3 , wherein the release layer is made of an inorganic material.

5. The method according to claim 1 , further comprising forming a release layer on the first substrate before the forming of the first adhesive layer.

6. The method according to claim 1 , further comprising, upon the forming of the first functional layer on the second substrate that is firmly attached onto the first substrate with the first adhesive layer in between, making a cut on a peripheral part of the first functional layer and forming thereafter a protective film on the first functional layer.

7. The method according to claim 1 , further comprising:

firmly attaching a fourth substrate onto a third substrate with a second adhesive layer in between;

attaching the fourth substrate and the second substrate to each other to cause the fourth substrate and the second substrate to be opposed to each other; and

peeling off the third substrate followed by the peeling off of the first substrate, after the attaching of the fourth substrate and the second substrate to each other.

8. The method according to claim 7 , further comprising forming a second functional layer on the fourth substrate after the firmly attaching of the fourth substrate onto the third substrate.

9. The method according to claim 8 , wherein each of the first functional layer and the second functional layer is one of a semiconductor layer, a display layer, and a color filter.

10. The method according to claim 7 , wherein each of the first substrate and the third substrate has rigidity.

11. The method according to claim 7 , wherein each of the second substrate and the fourth substrate has flexibility.

12. The method according to claim 7 , wherein the second adhesive layer has adhesive force that satisfies the Expression (1) and one or both of the Expressions (2) and (3).

13. A method of manufacturing a flexible device, the method comprising:

forming an adhesive layer on a first substrate, the adhesive layer having adhesive force that satisfies the following Expression (1) and one or both of the following Expressions (2) and (3);

fixing a second substrate onto the adhesive layer, the second substrate having flexibility;

forming a functional layer on the second substrate; and

peeling off the first substrate from the second substrate,

A

<

x

2

L

2

+

4

⁢

⁢

x

2

·

(

σ

max

-

6

⁢

⁢

E

·

h

L

2

·

x

)

(

1

)

where “L” is a length of the first substrate in a direction in which the first substrate is peeled off,

“h” is a thickness of the first substrate in millimeter,

“x” is an allowable deformation amount of the first substrate,

“E” is a Young's modulus of the first substrate, and

“σ max ” is a limit bending stress of the first substrate,

B′<C−ρhg   (2)

where “B” is adhesive force between the first substrate and the second substrate at a peeling start part when the peeling is performed,

“C” is peeling force in a vertical direction (in a Z-axis direction) when the peeling is performed,

“ρ” is a density of the first substrate,

“h” is the thickness of the first substrate in millimeter, and

“g” is gravitational constant,

1

=

r

r

-

d

·

d

⁡

(

2

⁢

⁢

r

-

d

)

(

3

)

where “l” is a width of a region in which the peeling is started,

“d” is an amount of projection and warpage of the first substrate, and

“r” is a curvature radius.

14. A laminate, comprising:

a first substrate having rigidity;

a second substrate having flexibility; and

an adhesive layer provided between the first substrate and the second substrate, and having adhesive force that satisfies the following Expression (1),

A

<

x

2

L

2

+

4

⁢

⁢

x

2

·

(

σ

max

-

6

⁢

⁢

E

·

h

L

2

·

x

)

(

1

)

where “L” is a length of the first substrate in a direction in which the first substrate is peeled off,

“h” is a thickness of the first substrate in millimeter,

“x” is an allowable deformation amount of the first substrate,

“E” is a Young's modulus of the first substrate, and

“σ max ” is a limit bending stress of the first substrate.