# US 8,542,443 B2 · Light reflector and planar light source device

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- Number: US 8,542,443 B2
- Document ID: US8542443B2
- Status: Granted
- Kind: B2
- Application number: 11/722,026
- Filed: 2005-12-16
- Published: 2008-06-05
- Granted: 2013-09-24
- Earliest claimed: 2004-12-17
- Assignees: Yupo Corporation
- Applicants: Takahiko Ueda; Hiroshi Koyama
- Inventors: Takahiko Ueda; Hiroshi Koyama
- Web page: https://patentgrep.com/patent/US8542443B2

## CPC

- G02B 6/0055: {Reflecting element, sheet or layer}
- F21V 7/24: characterised by the material
- F21V 7/28: characterised by coatings
- G02B 5/0221: {the surface having an irregular structure (G02B5/0226 takes precedence)}
- G02B 5/0242: {by means of dispersed particles}
- G02B 5/0268: {characterized by the fabrication or manufacturing method}
- G02B 5/0278: {used in transmission}
- G02B 5/0284: {used in reflection}
- G02B 6/0065: {Manufacturing aspects; Material aspects}
- G02F 1/133605: {including specially adapted reflectors}
- F21Y 2103/00: Elongate light sources, e.g. fluorescent tubes
- G02F 1/133611: {including means for improving the brightness uniformity}
- G02F 2201/34: reflector
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- F21V: FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
- G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- F21Y: INDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO THE FORM OR THE KIND OF THE LIGHT SOURCES OR OF THE COLOUR OF THE LIGHT EMITTED

## Abstract

A light reflector of which the bidirectional reflectance R1 is from 90 to 120% when the light entrance angle is 15° and the light acceptance angle is 0°, and the bidirectional reflectance R2 is from 85 to 110% when the light entrance angle is 75° and the light acceptance angle is 0°. The light reflector has high reflectivity, and attains brightness improvement even in underlight-type backlights.

## Claims

### Claim 1

A light reflector, comprising:
a substrate layer comprising a polyolefinic resin and a filler and stretched in at least one direction; and
a light-diffusive layer including a filler in a concentration of from 45 to 70% by weight,
wherein the substrate layer has a bidirectional reflectance R1 which is from 90 to 120% with respect to a bidirectional reflectance of a ceramic standard white plate, when a light entrance angle is 15° and a light acceptance angle is 0°, the substrate layer has a bidirectional reflectance R2 which is from 85 to 110% with respect to a bidirectional reflectance of a ceramic standard white plate, when the light entrance angle is 75° and the light acceptance angle is 0°, the light entrance angle and the light acceptance angle are angles with respect to a normal line direction of a surface to which light is applied, and the filler in the light-diffusive layer comprises at least one material selected from the group consisting of an inorganic filler having a mean particle size of from 0.2 to 0.7 μm and an organic filler having a mean dispersed particle size of from 0.2 to 0.7 μm.

### Claim 2 (depends on 1)

The light reflector according to claim 1, wherein the substrate layer has a relative brightness of from 112 to 150% with respect to a brightness of synthetic paper used as a standard.

### Claim 3 (depends on 1)

The light reflector according to claim 1, wherein the substrate layer has a light-reflecting face which has a light-collecting function.

### Claim 4 (depends on 1)

The light reflector according to claim 1, wherein the substrate layer is stretched to an areal draw ratio of from 1.3 to 80 times.

### Claim 5 (depends on 1)

The light reflector according to claim 1, wherein the light-diffusive layer is included in a laminate film formed on at least one face of the substrate layer.

### Claim 6 (depends on 5)

The light reflector according to claim 5, wherein the filler in the light-diffusive layer includes the inorganic filler and the organic filler.

### Claim 7 (depends on 5)

The light reflector according to claim 5, wherein the laminate film has a protective layer on a face of the substrate layer opposite to the face having the light-diffusive layer.

### Claim 8 (depends on 5)

The light reflector according to claim 5, wherein the light-diffusive layer has a thickness which is from 0.5 to 20 μm.

### Claim 9 (depends on 5)

The light reflector according to claim 5, wherein the laminate film has a porosity of from 15 to 60%.

### Claim 10 (depends on 1)

The light reflector according to claim 1, wherein the filler in the substrate layer is in a concentration of from 5 to 75% by weight and is at least one material selected from the group consisting of an inorganic filler having a mean particle size of from 0.05 to 0.9 μm and an organic filler having a mean dispersed particle size of from 0.05 to 0.9 μm.

### Claim 11 (depends on 1)

The light reflector according to claim 1, wherein the filler in the substrate layer is a surface-treated inorganic filler.

### Claim 12 (depends on 1)

The light reflector according to claim 1, wherein the substrate layer has a porosity of from 15 to 60%.

### Claim 13 (depends on 1)

A planar light source device comprising the light reflector of claim 1.