# US 11,307,452 B2 · Backlight device and display apparatus

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- Number: US 11,307,452 B2
- Document ID: US11307452B2
- Status: Granted
- Kind: B2
- Application number: 16/814,367
- Filed: 2020-03-10
- Published: 2021-03-25
- Granted: 2022-04-19
- Earliest claimed: 2019-09-20
- Assignees: Boe Technology Group Co., Ltd.
- Applicants: Boe Technology Group Co., Ltd.
- Inventors: Tao Hong
- Web page: https://patentgrep.com/patent/US11307452B2

## CPC

- G02F 1/133602: {Direct backlight}
- G02F 1/133615: {Edge-illuminating devices, i.e. illuminating from the side}
- G02B 6/0016: {Grooves, prisms, gratings, scattering particles or rough surfaces}
- G02B 6/002: {by shaping at least a portion of the light guide, e.g. with collimating, focussing or diverging surfaces}
- G02B 6/0031: {Reflecting element, sheet or layer}
- G02B 6/005: {provided by one optical element, or plurality thereof, placed on the light output side of the light guide}
- G02B 6/0056: {for producing polarisation effects, e.g. by a surface with polarizing properties or by an additional polarizing elements}
- G02B 6/0063: {for extracting light out both the major surfaces of the light guide}
- G02F 1/133512: {Light shielding layers, e.g. black matrix (G02F1/136209 takes precedence)}
- G02F 1/13362: {providing polarized light, e.g. by converting a polarisation component into another one}
- G02F 1/13363: Birefringent elements, e.g. for optical compensation
- 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

The present disclosure provides a backlight device and a display apparatus. The backlight device includes: a light guide plate having a light exit face and a light entrance face, and a plurality of light extraction structures disposed on the light exit face. A light beam is totally reflected in the light guide plate, and can enter the light extraction structure through a surface of the light extraction structure that is in contact with the light exit surface of the light guide plate. The light extraction structure is configured to converge its output light beam when the backlight device is used in a dark display state, and diverge its output light beam when the backlight device is used in the grayscale display state.

## Claims

### Claim 1

A backlight device, comprising:
a light guide plate having a light exit face and a light entrance face; and
a plurality of light extraction structures disposed on the light exit face of the light guide plate,
wherein a light beam is totally reflected in the light guide plate, and can enter a light extraction structure of the plurality of light extraction structures through a surface of the light extraction structure that is in contact with the light exit surface of the light guide plate, and the light extraction structure is configured to converge its output light beam when the backlight device is used in a dark display state, and diverge its output light beam when the backlight device is used in a grayscale display state.

### Claim 2 (depends on 1)

The backlight device as claimed in claim 1, wherein each of the light extraction structures comprises:
a light extraction grating arranged on the light exit face so as to extract light from the light exit face of the light guide plate;
a polarization conversion element disposed on a side of the light extraction grating away from the light exit surface, and configured to convert the light extracted by the light extraction grating into a predetermined first polarization state in the dark display state and convert the light extracted by the light extraction grating into a predetermined second polarization state in the grayscale display state;
a birefringent microlens disposed on a side of the polarization conversion element away from the light exit surface, and configured to converge the linearly polarized light in the first polarization state from the polarization conversion element in the dark display state and diverge the linearly polarized light in the second polarization state from the polarization conversion element in the grayscale display state, wherein the first polarization state is different from the second polarization state; and
a filling layer covering a surface of the birefringent microlens away from the polarization conversion elements.

### Claim 3 (depends on 2)

The backlight device as claimed in claim 2, further comprising a polarizer configured so that light, after passing through the polarizer, becomes linearly polarized light and enters the light guide plate.

### Claim 4 (depends on 2)

The backlight device as claimed in claim 2, wherein the birefringent microlens is a convex lens and is formed of a birefringent material, and a refractive index of a material for forming the filling layer is between a first refractive index of the birefringent material for the linearly polarized light in the first polarization state and a second refractive index of the birefringent material for the linearly polarized light in the second polarization state.

### Claim 5 (depends on 2)

The backlight device as claimed in claim 2, wherein the polarization conversion element of each of the light extraction structures includes a first electrode, a first orientation layer, a polarization conversion liquid crystal layer, a second orientation layer, and a second electrode which are stacked in that order.

### Claim 6 (depends on 5)

The backlight device as claimed in claim 5, wherein the first electrode and the second electrode are formed of a transparent conductive material.

### Claim 7 (depends on 2)

The backlight device as claimed in claim 2, wherein an orthographic projection of the light extraction grating on the light exit face and an orthographic projection of the polarization conversion element on the light exit face coincide.

### Claim 8 (depends on 1)

The backlight device as claimed in claim 1, further comprising a light source, from which light enters the light guide plate through the light entrance face.

### Claim 9 (depends on 3)

The backlight device as claimed in claim 3, wherein the light extraction grating is configured to extract an incident light at a specific angle and extract no light at other angles.

### Claim 10 (depends on 3)

The backlight device as claimed in claim 3, wherein the light extraction grating is formed by plating a layer on the light guide plate and etching the plated layer.

### Claim 11 (depends on 1)

A display apparatus comprising a display module and the backlight device as claimed in claim 1, the display module being provided on a light output face of the backlight device.

### Claim 12 (depends on 11)

The display apparatus as claimed in claim 11, wherein the display module comprises:
a liquid crystal layer arranged on a side of the plurality of light extraction structures, so that a light outputted by the plurality of light extraction structures irradiate the liquid crystal layer; and
a black matrix arranged on a side of the liquid crystal layer away from the light extraction structures, openings being defined in the black matrix.