# US 9,753,320 B2 · Light diffusion sheet, and backlight unit for liquid crystal display device

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- Number: US 9,753,320 B2
- Document ID: US9753320B2
- Status: Granted
- Kind: B2
- Application number: 14/503,571
- Filed: 2014-10-01
- Published: 2015-04-09
- Granted: 2017-09-05
- Earliest claimed: 2013-10-03
- Assignees: Keiwa Inc.
- Applicants: Keiwa Inc.
- Inventors: Akira Arakawa
- Web page: https://patentgrep.com/patent/US9753320B2

## CPC

- G02F 1/133504: {Diffusing, scattering, diffracting elements (associated to illuminating devices G02F1/133606)}
- G02B 5/0226: {having particles on the surface}
- G02F 1/133614: {using photoluminescence, e.g. phosphors illuminated by UV or blue light}
- G02F 1/133615: {Edge-illuminating devices, i.e. illuminating from the side}
- 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
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

A light diffusion sheet capable of inhibiting emission of blue light, and a backlight unit for a liquid crystal display device. The light diffusion sheet includes: a transparent substrate layer; and a light diffusion layer overlaid on the front face side of the substrate layer. The light diffusion layer is a light diffusion sheet for a backlight unit of a liquid crystal display device containing a light-diffusing agent and a binder covering the light-diffusing agent, and includes a component that attenuates blue light. The blue light attenuation component is preferably a yellow fluorescent material that generates yellow light through excitation by blue light, or a light absorbing agent that absorbs blue light. The light diffusion layer preferably includes the blue light attenuation component. Preferably, the light-diffusing agent is resin beads, and the blue light attenuation component is included in the resin beads.

## Claims

### Claim 1

A light diffusion sheet comprising:
a transparent substrate layer; and
a light diffusion layer overlaid on a front face side of the substrate layer,
the light diffusion layer being a light diffusion sheet for a backlight unit of a liquid crystal display device comprising a light-diffusing agent and a binder covering the light-diffusing agent, and
the light diffusion layer comprising a component that attenuates only blue light,
wherein
the component that attenuates the blue light is a yellow fluorescent material that generates only yellow light through excitation by the blue light,
the binder comprises a light absorbing agent that attenuates visible light other than the blue light, and
the light absorbing agent is configured to absorb yellow light emitted resulting from the component that attenuates blue light.

### Claim 2 (depends on 1)

The light diffusion sheet according to claim 1, wherein the light-diffusing agent is resin beads, and the component that attenuates blue light is included in the resin beads.

### Claim 3 (depends on 1)

The light diffusion sheet according to claim 1, wherein the component that attenuates blue light is included in the binder.

### Claim 4 (depends on 1)

The light diffusion sheet according to claim 1, wherein the substrate layer comprises the component that attenuates blue light.

### Claim 5 (depends on 1)

The light diffusion sheet according to claim 1, wherein a sticking preventive layer comprising beads dispersed in a binder is provided on a back face side of the substrate layer, and the component that attenuates blue light is included in the binder of the sticking preventive layer.

### Claim 6 (depends on 1)

The light diffusion sheet according to claim 1, which is a light diffusion sheet for use at the top.

### Claim 7 (depends on 1)

A backlight unit for a liquid crystal display device that allows rays of light radiated from a lamp to be dispersed and leads the rays to a front face side, the backlight unit for a liquid crystal display device comprising the light diffusion sheet according to claim 1.

### Claim 8 (depends on 1)

The light diffusion sheet according to claim 1, wherein the light diffusion layer is 1 micrometer to 30 micrometers in thickness.

### Claim 9 (depends on 8)

The light diffusion sheet according to claim 8, wherein the light diffusing agent comprises beads having a mean particle size from 1 micrometer to 50 micrometers.

### Claim 10 (depends on 1)

The light diffusion layer according to claim 1, wherein a component that attenuates the blue light is inside the binder.

### Claim 11 (depends on 7)

The backlight unit according to claim 7; wherein the light diffusion layer is 1 micrometer to 30 micrometers in thickness.

### Claim 12 (depends on 11)

The backlight unit according to claim 11, wherein the light diffusing agent comprises beads having a mean particle size from 1 micrometer to 50 micrometers.

### Claim 13 (depends on 7)

The backlight unit according to claim 7, wherein a component that attenuates the blue light is inside the binder.