White film and backlight using same

• US 8,557,370 B2
• Filed: 10/13/2011
• Issued: 10/15/2013
• Est. Priority Date: 11/12/2004
• Status: Active Grant

• Current Assignee: Toray Industries Incorporated
• Original Assignee: Toray Industries Incorporated
• Inventors: Kanaya, Tomoko, Matsuyama, Tadami, Sakaguchi, Yoshihiko, Watanabe, Osamu
• Primary Examiner(s): Chen, Vivian
• Application Number:
  US13/272,355
• Publication Number:
  US 20120033154A1
• Time in Patent Office: 733 Days
• Field of Search: None
• US Class Current: 428/195.1
• CPC Class Codes: C09K 2323/00 Functional layers of liquid crystal optical display excluding electroactive liquid crystal layer characterised by chemical composition
• CPC Class Codes: C09K 2323/035 Ester polymer, e.g. polycarbonate, polyacrylate or polyester
• CPC Class Codes: C09K 2323/06 Substrate layer characterised by chemical composition
• CPC Class Codes: G02B 6/0055 Reflecting element, sheet or layer
• CPC Class Codes: G02F 1/133605 including specially adapted reflectors
• CPC Class Codes: Y10T 428/24802 Discontinuous or differential coating, impregnation or bond [e.g., artwork, printing, retouched photograph, etc.]
• CPC Class Codes: Y10T 428/249953 Composite having voids in a component [e.g., porous, cellular, etc.]
• CPC Class Codes: Y10T 428/249976 Voids specified as closed
• CPC Class Codes: Y10T 428/249978 Voids specified as micro
• CPC Class Codes: Y10T 428/249987 With nonvoid component of specified composition
• CPC Class Codes: Y10T 428/249991 Synthetic resin or natural rubbers
• CPC Class Codes: Y10T 428/249992 Linear or thermoplastic
• CPC Class Codes: Y10T 428/31786 Of polyester [e.g., alkyd, etc.]

Abstract

A white film including polymer film wherein both the thermal shrinkage rate in the longitudinal direction and that in the transverse direction of the film are not less than −0.2% and not more than 0.5% at 90° C., and a backlight for liquid crystal displays using such a white film. Since the white film hardly suffers from undulation or rise in its end portions, it is most suitable as a reflection film for backlights of liquid crystal displays. Since a backlight for liquid crystal displays using this white film can be used for a long time, it is applicable to liquid crystal displays of various electrical/electronic devices.

Claims

1. A white film comprising polymer film having a thickness of 188 to 250 μ

m, containing air bubbles and having a thermal shrinkage rate in longitudinal directions of the film that are not less than 0.08% and not more than 0.15% at 90°

C., in transverse directions of the film that are not less than −

0.05% and not more than 0.01% at 90°

C., wherein the white film has reflectance properties.

2. The white film as described in claim 1, wherein the polymer film is biaxially oriented polyethylene terephthalate film.

3. The white film as described in claim 2, wherein at least one face of the polymer film is provided with an ultraviolet-absorbing layer that contains an ultraviolet-absorbing substance.

4. The white film as described in claim 3, wherein another face of the white film, which is not the face provided with the ultraviolet-absorbing polymer film layer, is provided with a printed layer that contains ink.

5. A backlight device for liquid crystal display comprising white film as described in claim 2.

6. The white film as described in claim 1, wherein at least one face of the polymer film is provided with an ultraviolet-absorbing layer that contains an ultraviolet-absorbing substance.

7. The white film as described in claim 6, wherein another face of the white film, which is not the face provided with the ultraviolet-absorbing polymer film layer, is provided with a printed layer that contains ink.

8. The white film as described in claim 7, wherein the printed layer is provided in parts of polymer film.

9. A backlight device for liquid crystal display comprising white film as described in claim 7.

10. A backlight device for liquid crystal display comprising white film as described in claim 6.

11. A backlight device for liquid crystal display comprising white film as described in claim 1.

12. The backlight device for liquid crystal display as described in claim 11, wherein the backlight device is a direct backlight device.

13. The backlight device for liquid crystal display as described in claim 12, wherein the size of the liquid crystal display is not less than 76.2 cm (30 inches).

14. A white film comprising polymer film having a thickness of 188 to 250 μ

m, containing air bubbles and having a thermal shrinkage rate in longitudinal directions of the film that are not less than 0.08% and not more than 0.15% at 90°

C., in transverse directions of the film that are not less than −

0.05% and not more than 0.01% at 90°

C., wherein mean reflectance of the white film in a wavelength range of 400 nm to 700 nm is not less than 85%.