Image forming apparatus and light emitting device

• US 10,642,183 B2
• Filed: 05/16/2018
• Issued: 05/05/2020
• Est. Priority Date: 11/18/2015
• Status: Active Grant

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: Kim, Wan Chin, Lee, Wan Ho, Kim, Kyoung Man, Kim, Su Hwan, Park, Yong Shik, Han, Sang Koo
• Primary Examiner(s): Zimmermann, John
• Application Number:
  US15/981,422
• Publication Number:
  US 20190064693A1
• Time in Patent Office: 720 Days
• CPC Class Codes: B41J 2/451 Special optical means therefor, e.g. lenses, mirrors, focusing means
• CPC Class Codes: F21V 7/28 characterised by coatings
• CPC Class Codes: G02B 5/0875 the reflecting layers comprising two or more metallic layers
• CPC Class Codes: G03G 15/04054 by LED arrays
• CPC Class Codes: G03G 2215/0409 Light-emitting diodes, i.e. LED-array

Abstract

An image forming device comprises: an exposer having a plurality of light emitting devices, a light emitting device among the plurality of light emitting devices to transmit light toward a photosensitive drum; and a developer to develop an electrostatic latent image formed on a surface of the photosensitive drum by the light, wherein the light emitting device among the plurality of light emitting devices includes: a light emitting layer to generate the light; and a reflective layer to reflect at least a portion of the generated light. The reflective layer can include a plurality of sub-reflective layers, in which a thickness of a sub-reflective layer among the plurality of sub-reflective layers is different from a thickness of another sub-reflective layer among the plurality of sub-reflective layers, and/or a refractive index of a sub-reflective layer among the plurality of sub-reflective layers is different from a refractive index of another sub-reflective layer among the plurality of sub-reflective layers.

Claims

1. An image forming apparatus comprising:

an exposer having a plurality of light emitting devices, a light emitting device among the plurality of light emitting devices to transmit light toward a photosensitive drum; and

a developer to develop an electrostatic latent image formed on a surface of the photosensitive drum by the light,

wherein

the light emitting device among the plurality of light emitting devices includes;

a light emitting layer to generate the light having a central wavelength variable to;

a first wavelength,

a second wavelength different from the first wavelength, and

a third wavelength different from the first wavelength and the second wavelength; and

a reflective layer to reflect at least a portion of the generated light, and

the reflective layer includes a plurality of sub-reflective layers, wherein the plurality of sub-reflective layers includes three sub-reflective layers respectively having;

a first thickness and a first refractive index at a first ratio corresponding to the first wavelength,

a second thickness and a second refractive index at a second ratio corresponding to the second wavelength, and

a third thickness and a third refractive index at a third ratio corresponding to the third wavelength.

2. The image forming apparatus of claim 1, wherein a sub-reflective layer of the plurality of sub-reflective layers is to reflect light ray having a wave length different from wavelengths of light rays to be reflected by other sub-reflective layers of the plurality of sub-reflective layers.

3. The image forming apparatus of claim 2, wherein:

the plurality of sub-reflective layers include low refractive index layers and high refractive index layers; and

refractive indices of the low refractive index layers are lower than refractive indices of the high refractive index layers.

4. The image forming apparatus of claim 3, wherein

a thickness of a low refractive index layer among the low refractive index layers included in the plurality of sub-reflective layers is different from a thickness of another low refractive index layer among the low refractive index layers, and/or

a refractive index of a low refractive index layer among the low refractive index layers included in the plurality of sub-reflective layers is different from a refractive index of another low refractive index layer among the low refractive index layers.

5. The image forming apparatus of claim 3, wherein

a thickness of a high refractive index layer among the high refractive index layers included in the plurality of sub-reflective layers is different from a thickness of another high refractive index layer among the high refractive index layers, and/or

a refractive index of a high refractive index layer among the high refractive index layers included in the plurality of sub-reflective layers is different from a refractive index of another high refractive index layer among the high refractive index layers.

6. The image forming apparatus of claim 3, wherein

a thickness of a low refractive index layer among the low refractive index layers included in the plurality of sub-reflective layers is different from a thickness of another low refractive index layer among the low refractive index layers, and

a thickness of a high refractive index layer among the high refractive index layers included in the plurality of sub-reflective layers is different from a thickness of another high refractive index layer among the high refractive index layers.

7. The image forming apparatus of claim 3, wherein

a refractive index of a low refractive index layer among the low refractive index layers included in the plurality of sub-reflective layers is different from a refractive index of another low refractive index layer among the low refractive index layers, and

a refractive index of a high refractive index layer among the high refractive index layers included in the plurality of sub-reflective layers is different from a refractive index of another high refractive index layer among the high refractive index layers.

8. The image forming apparatus of claim 3, wherein

the low refractive index layers are formed of aluminum-gallium-arsenic (AlGaAs) semiconductors having low refractive indices,

the high refractive index layers are formed of AlGaAs semiconductors having high refractive indices.

9. The image forming apparatus of claim 8, wherein

a thickness of an AlGaAs semiconductor among the AlGaAs semiconductors having the low refractive indices is different from a thickness of another AlGaAs semiconductor among the AlGaAs semiconductors having the low refractive indices, and/or

an Al-mixing percentage of an AlGaAs semiconductor among the AlGaAs semiconductors having the low refractive indices is different from an Al-mixing percentage of another AlGaAs semiconductor among the AlGaAs semiconductors having the low refractive indices.

10. The image forming apparatus of claim 8, wherein

a thickness of an AlGaAs semiconductor among the AlGaAs semiconductors having the high refractive indices is different from a thickness of another AlGaAs semiconductor among the AlGaAs semiconductors having the high refractive indices, and/or

an Al-mixing percentage of an AlGaAs semiconductor among the AlGaAs semiconductors having the high refractive indices is different from an Al-mixing percentage of another AlGaAs semiconductor among the AlGaAs semiconductors having the high refractive indices.

11. The image forming apparatus of claim 8, wherein

a thickness of an AlGaAs semiconductor among the AlGaAs semiconductors having the low refractive indices is different from a thickness of another AlGaAs semiconductor among the AlGaAs semiconductors having the low refractive indices, and

a thickness of an AlGaAs semiconductor among the AlGaAs semiconductors having the high refractive indices is different from a thickness of another AlGaAs semiconductor among the AlGaAs semiconductors having the high refractive indices.

12. The image forming apparatus of claim 8, wherein

an Al-mixing percentage of an AlGaAs semiconductor among the AlGaAs semiconductors having the low refractive indices is different from an Al-mixing percentage of another AlGaAs semiconductor among the AlGaAs semiconductors having the low refractive indices, and

an Al-mixing percentage of an AlGaAs semiconductor among the AlGaAs semiconductors having the high refractive indices is different from an Al-mixing percentage of another AlGaAs semiconductor among the AlGaAs semiconductors having the high refractive indices.

13. The image forming apparatus of claim 1, wherein the reflective layer includes a first reflective layer including a plurality of first sub-reflective layers and a second reflective layer including a plurality of second sub-reflective layers.

14. The image forming apparatus of claim 13, wherein:

each of the plurality of first sub-reflective layers includes a first low refractive index layer and a first high refractive index layer; and

each of the plurality of second sub-reflective layers includes a second low refractive index layer and a second high refractive index layer.

15. The image forming apparatus of claim 14, wherein:

thicknesses and/or refractive indices of the first low refractive index layer and the second low refractive index layer are different from each other; and

thicknesses and/or refractive indices of the first high refractive index layer and the second high refractive index layer are different from each other.

16. The image forming apparatus of claim 1, wherein

a thickness of at least one sub-reflective layer among the plurality of sub-reflective layers is different from a thickness of another sub-reflective layer among the plurality of sub-reflective layers, and/or

a refractive index of at least one sub-reflective layer among the plurality of sub-reflective layers is different from a refractive index of another sub-reflective layer among the plurality of sub-reflective layers.

17. An exposer for an image forming apparatus, comprising:

a plurality of light emitting devices, a light emitting device among the plurality of light emitting devices to transmit light toward a photosensitive drum of an image forming apparatus,

wherein the light emitting device among the plurality of light emitting devices includes;

a light emitting layer to generate the light having a central wavelength variable to;

a first wavelength,

a second wavelength different from the first wavelength, and

a third wavelength different from the first wavelength and the second wavelength; and

a reflective layer to reflect at least a portion of the generated light, and

the reflective layer includes a plurality of sub-reflective layers, wherein the plurality of sub-reflective layers includes three sub-reflective layers respectively having;

a first thickness and a first refractive index at a first ratio corresponding to the first wavelength,

a second thickness and a second refractive index at a second ratio corresponding to the second wavelength, and

a third thickness and a third refractive index at a third ratio corresponding to the third wavelength.

18. The exposer of claim 17, wherein a sub-reflective layer of the plurality of sub-reflective layers is to reflect light ray having a wave length different from wavelengths of light rays to be reflected by other sub-reflective layers of the plurality of sub-reflective layers.

19. The exposer of claim 17, wherein:

the plurality of sub-reflective layers include low refractive index layers and high refractive index layers;

refractive indices of the low refractive index layers are lower than refractive indices of the high refractive index layers; and

a thickness of a low refractive index layer among the low refractive index layers included in the plurality of sub-reflective layers is different from a thickness of another low refractive index layer among the low refractive index layers.

20. The exposer of claim 19, wherein

a thickness of at least one sub-reflective layer among the plurality of sub-reflective layers is different from a thickness of another sub-reflective layer among the plurality of sub-reflective layers, and/or

a thickness of a high refractive index layer among the high refractive index layers included in the plurality of sub-reflective layers is different from a thickness of another high refractive index layer among the high refractive index layers.