Light-scattering substrate, method for manufacturing light-scattering substrate, polarizing plate and image display device

• US 20100277674A1
• Filed: 04/29/2010
• Published: 11/04/2010
• Est. Priority Date: 04/30/2009
• Status: Active Grant

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Inventors: Ohashi, Yusuke, Yoneyama, Hiroyuki, Watanabe, Jun, Abiru, Daisaku
• Granted Patent: US 8,643,808 B2
• Time in Patent Office: Days
• US Class Current: 349/96
• CPC Class Codes: B29C 39/148 characterised by the shape of the surface
• CPC Class Codes: B29C 39/20 Making multilayered or multicoloured articles B29C39/142 takes precedence
• CPC Class Codes: B29K 2105/16 Fillers
• CPC Class Codes: B29K 2995/0018 having particular optical properties, e.g. fluorescent or phosphorescent
• CPC Class Codes: G02B 5/02 Diffusing elements; Afocal elements
• CPC Class Codes: G02B 5/3033 in the form of a thin sheet or foil, e.g. Polaroid

Abstract

A light-scattering substrate having an irregular shape on one surface thereof is provided, the light-scattering substrate including: a thermoplastic resin; and at least one kind of transparent particles having a mean primary particle size of 3 μm or more and not more than 12 μm, wherein the light-scattering substrate contains a first region having a thickness of ½ or more times and not more than 4 times the mean primary particle size of the transparent particles from the surface having an irregular shape; and a second region having a thickness of 3/2 or more times the mean primary particle size of the transparent particles from a surface on back side of the surface having an irregular shape, and the first region and the second region have a region not substantially containing the transparent particle.

Claims

1. A light-scattering substrate having an irregular shape on one surface thereof, the light-scattering substrate comprising:

a thermoplastic resin; and

at least one kind of transparent particles having a mean primary particle size of 3 μ

m or more and not more than 12 μ

m,

wherein the light-scattering substrate contains a first region having a thickness of ½

or more times and not more than 4 times the mean primary particle size of the transparent particles from the surface having an irregular shape; and

a second region having a thickness of 3/2 or more times the mean primary particle size of the transparent particles from a surface on back side of the surface having an irregular shape, and

the first region and the second region have a region not substantially containing the transparent particles.

2. The light-scattering substrate according to claim 1,

wherein the surface of the light-scattering substrate having an irregular shape has an arithmetic mean roughness Ra, a mean spacing of irregularities Sm and a mean tilt angle of irregularities θ

a in conformity with JIS B0601, which are satisfied with following expressions (1) to (3);

0.03 μ

m≦

Ra≦

0.3 μ

m 

 

(1)

10 μ

m≦

Sm≦

300 μ

m 

 

(2)

3. The light-scattering substrate according to claim 1,

wherein a tilt angle of irregularities of the surface of the light-scattering substrate having an irregular shape has following distribution:

(a) an integrated value of the frequency of 0°

or more and less than 0.5°

is less than 25%;

(b) an integrated value of the frequency of 0.5°

or more and less than 10°

is 65% or more and less than 100%; and

(c) an integrated value of the frequency of 10°

or more is 0% or more and less than 20%.

4. The light-scattering substrate according to claim 1,

wherein the transparent particles are substantially spherical resin particles.

5. The light-scattering substrate according to claim 1,

wherein an absolute value of a difference between a refractive index of the transparent particles and a refractive index of the light-scattering substrate in the case of excluding the transparent particles from the light-scattering substrate is less than 0.09.

6. The light-scattering substrate according to claim 1, which has light scattering properties such that a value of an image clarity measured through an optical comb having a width of 2 mm by using an image clarity measuring apparatus in conformity with JIS K7105 is from 5% to 60%.

7. The light-scattering substrate according to claim 1,

wherein a transmitted scattered-light profile measured by a goniophotometer with an acceptance angle of 2°

is satisfied with following expression (d);

0.03≦

I(4°

)/I0≦

0.07 

 

(d)

wherein I(4°

) represents an transmitted light intensity at a position tilted by 4°

from a normal line of the light-scattering substrate; and

I0 represents a light intensity when a light source is measured from the front.

8. The light-scattering substrate according to claim 1,

wherein a haze value caused by inside is 0.1% or more and less than 30%;

and a haze value caused by surface is 3% or more and less than 30%.

9. A method for manufacturing a light-scattering substrate having an irregular shape on one surface thereof, wherein the light-scattering substrate comprises:

a thermoplastic resin; and

at least one kind of transparent particles having a mean primary particle size of 3 μ

m or more and not more than 12 μ

m,

wherein the light-scattering substrate contains a first region having a thickness of ½

or more times and not more than 4 times the mean primary particle size of the transparent particles from the surface having an irregular shape; and

a second region having a thickness of 3/2 or more times the mean primary particle size of the transparent particles from a surface on back side of the surface having an irregular shape, and

the first region and the second region have a region not substantially containing the transparent particles,

the method comprising;

casting a transparent particle-containing dope containing a thermoplastic resin and at least one kind of transparent particles having a mean primary particle size of 3 μ

m or more and not more than 12 μ

m; and

a dope for surface shape adjustment containing a thermoplastic resin and not substantially containing a particle having a mean primary particle size of 1 μ

m or more, in which a concentration of the thermoplastic resin is lower than that of the transparent particle-containing dope,

in this order simultaneously or sequentially on a support, thereby forming a film.

10. The method for manufacturing a light-scattering substrate according to claim 9, which further comprises casting a dope not substantially containing a particle having a mean primary particle size of 1 μ

m or more and composed of a thermoplastic resin,

wherein the dope not substantially containing a particle having a mean primary particle size of 1 μ

m or more and composed of a thermoplastic resin;

the transparent particle-containing dope; and

the dope for surface shape adjustment are casted in this order simultaneously or sequentially on a support, thereby forming a film.

11. The method for manufacturing a light-scattering substrate according to claim 9,

wherein a flow rate is adjusted such that when a mean primary particle size of the transparent particles is defined as D, a film thickness of the dope for surface shape adjustment after drying is from (1/2)D to 4D.

12. The method for manufacturing a light-scattering substrate according to claim 9,

wherein a viscosity of the dope for surface shape adjustment at room temperature is 1 Pa·

s or more and not more than 200 Pa·

s.

13. The method for manufacturing a light-scattering substrate according to claim 9, which comprises:

casting a dope not substantially containing a particle having a mean primary particle size of 1 μ

m or more and having a concentration of a thermoplastic resin lower than that of an adjacent dope simultaneously or sequentially between a plurality of dopes and the support, thereby forming a film.

14. A polarizing plate, comprising:

a polarizing film; and

a protective film on or above at least one side of the polarizing film, wherein the protective film is a light-scattering substrate having an irregular shape on one surface thereof, wherein the light-scattering substrate comprises;

a thermoplastic resin; and

at least one kind of transparent particles having a mean primary particle size of 3 μ

m or more and not more than 12 μ

m.

wherein the light-scattering substrate contains a first region having a thickness of ½

or more times and not more than 4 times the mean primary particle size of the transparent particles from the surface having an irregular shape; and

a second region having a thickness of 3/2 or more times the mean primary particle size of the transparent particles from a surface on back side of the surface having an irregular shape, and

the first region and the second region have a region not substantially containing the transparent particles.

15. An image display device, comprising:

a light-scattering substrate having an irregular shape on one surface thereof, wherein the light-scattering substrate comprises;

a thermoplastic resin; and

at least one kind of transparent particles having a mean primary particle size of 3 μ

m or more and not more than 12 μ

m,

wherein the light-scattering substrate contains a first region having a thickness of ½

or more times and not more than 4 times the mean primary particle size of the transparent particles from the surface having an irregular shape; and

a second region having a thickness of 3/2 or more times the mean primary particle size of the transparent particles from a surface on back side of the surface having an irregular shape, and

the first region and the second region have a region not substantially containing the transparent particles.

16. An image display device, comprising:

a light source;

a lower polarizing plate;

a liquid crystal cell; and

an upper polarizing plate in this order,

wherein the lower polarizing plate is a polarizing plate comprising;

a polarizing film; and

a protective film on or above at least one side of the polarizing film,

wherein the protective film is the a light-scattering substrate having an irregular shape on one surface thereof, wherein the light-scattering substrate comprises;

a thermoplastic resin; and

at least one kind of transparent particles having a mean primary particle size of 3 μ

m or more and not more than 12 μ

m,

wherein the light-scattering substrate contains a first region having a thickness of ½

or more times and not more than 4 times the mean primary particle size of the transparent particles from the surface having an irregular shape; and

a second region having a thickness of 3/2 or more times the mean primary particle size of the transparent particles from a surface on back side of the surface having an irregular shape, and

the first region and the second region have a region not substantially containing the transparent particles.