Photodiffusion sheet and backlight unit using this

• US 6,852,396 B1
• Filed: 09/10/1999
• Issued: 02/08/2005
• Est. Priority Date: 09/17/1998
• Status: Expired due to Term

• Current Assignee: KEIWA, Inc.
• Original Assignee: KEIWA, Inc.
• Inventors: Mineo, Yutaka
• Primary Examiner(s): Dye, Rena
• Assistant Examiner(s): FERGUSON, LAWRENCE D
• Application Number:
  US09/786,565
• Time in Patent Office: 1,978 Days
• Field of Search: 362/558, 362/330, 362/333, 362/355, 359/599, 428/195, 428/212
• US Class Current: 428/212
• CPC Class Codes: G02B 5/0226 having particles on the surface
• CPC Class Codes: G02B 5/0242 by means of dispersed particles
• CPC Class Codes: G02B 5/0278 used in transmission
• CPC Class Codes: G02B 6/0051 Diffusing sheet or layer
• CPC Class Codes: G02B 6/0065 Manufacturing aspects; Material aspects
• CPC Class Codes: Y10T 428/24942 including components having same physical characteristic in differing degree

Abstract

It is an object of the present invention to provide a light diffusing sheet that has a less tendency to be deflected due to heat generated by a lamp and a back light unit using this. The light diffusing sheet of the present invention comprises a base sheet and a light diffusing layer provided on a surface of the base sheet. The light diffusing layer is formed by dispersing resinous beads and a fine inorganic filler into a binder. It is preferable that the fine inorganic filler has an averaged particle diameter of not smaller than 5 nanometers and smaller than 1 micrometer. It is preferable that the amount of the fine inorganic filler to be mixed is 10 parts to 500 parts by weight for 100 parts by weight of a polymer component in the binder. As the fine inorganic filler, colloidal silica is used.

Claims

1. A light diffusing sheet comprising:

a transparent base sheet; and

a light diffusing layer provided on a front surface side of the base sheet, wherein

the light diffusing layer is formed by dispersing resinous beads and a fine inorganic filler into a binder, and

the fine inorganic filler is colloidal silica having an average particle diameter that is in a range of 5 nanometers to 50 nanometers.

2. The light diffusing sheet of claim 1, wherein the resinous beads of the light diffusing layer have an averaged particle diameter of 1 micrometer to 50 micrometers.

3. The light diffusing sheet of claim 1, wherein an amount of the fine inorganic filler mixed into the light diffusing layer is 10 parts to 500 parts by weight for 100 parts by weight of a polymer component in the binder.

4. A light diffusing sheet comprising:

a transparent base sheet;

a light diffusing layer provided on a front surface side of the base sheet; and

a sticking-proof layer provided on a rear surface side of the base sheet, wherein the sticking-proof layer is formed by dispersing resinous beads and a fine inorganic filler into a binder, and

the fine inorganic filler is colloidal silica having an average particle diameter that is in a range of 5 nanometers to 50 nanometers.

5. The light diffusing sheet of claim 4, wherein the resinous beads of the sticking-proof layer has an averaged particle diameter of 1 micrometer to 50 micrometers.

6. The light diffusing sheet of claim 4, wherein an amount of the fine inorganic filler mixed-into the sticking-proof layer is 10 parts to 500 parts by weight for 100 parts by weight of a polymer component in the binder.

7. A backlight unit comprising:

a lamp;

a light guiding plate disposed laterally of the lamp for guiding light rays emitted from the lamp to a front surface side and a light diffusing sheet disposed on a front surface side of the light guiding plate, wherein,

said light diffusing sheet comprises;

a transparent base sheet; and

a light diffusing layer provided on a front surface side of the base sheet, wherein

the light diffusing layer is formed by dispersing resinous beads and a fine inorganic filler into a binder, and

the fine inorganic filler is colloidal silica having an average particle diameter that is in a range of 5 nanometers to 50 nanometers.