Optical writing head such as organic EL array exposure head, method of manufacturing the same, and image forming apparatus using the same

• US 20040021762A1
• Filed: 03/10/2003
• Published: 02/05/2004
• Est. Priority Date: 03/11/2002
• Status: Active Grant

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Seki, Hideya, Yonekubo, Masatoshi
• Granted Patent: US 7,081,912 B2
• Time in Patent Office: Days
• US Class Current: 347/136
• CPC Class Codes: B41J 2/451 Special optical means therefor, e.g. lenses, mirrors, focusing means

Abstract

The present invention relates to a small optical writing head, such as an organic EL array exposure head, having long work distance with little crosstalk, a method of manufacturing the same, and an image forming apparatus using the same. The optical writing head is an optical writing head which projects fluxes of modulated light from light-emitting parts 2 of a light-emitting element array such as an organic EL array or fluxes of modulated light transmitted through shutter parts 2 of an optical shutter element array onto an image carrier 11 to form a predetermined pattern on the image carrier 11. The optical writing head comprises ball lenses 10 which are arranged such that the alignment of the ball lenses 10 corresponds to the alignment of the light-emitting parts 2 of the light-emitting element array or the shutter parts 2 of the optical shutter element array.

Claims

1. An optical writing head for projecting fluxes of modulated light from light-emitting parts of a light-emitting element array or fluxes of modulated light transmitted through shutter parts of an optical shutter element array onto an image carrier to form a predetermined pattern on said image carrier, said optical writing head being characterized by comprising ball lenses which are arranged such that the alignment of said ball lenses corresponds to the alignment of the light-emitting parts of said light-emitting element array or the shutter parts of said optical shutter element array.

2. An optical writing head as claimed in claim 1, wherein said ball lenses are fixed to a transparent member on the surface of said light-emitting element array or said optical shutter element array by transparent adhesive.

3. An optical writing head as claimed in claim 1, wherein the diameter of said ball lenses is equal to or less than the alignment pitch of the light-emitting parts of said light-emitting element array or the alignment pitch of the shutter parts of said optical shutter element array.

4. An optical writing head as claimed in claim 2, wherein the refractive index of said ball lenses is equal to or more than the refractive index of said transparent adhesive.

5. An optical writing head as claimed in claim 2, wherein the thickness of said transparent member is equal to or less than the diameter of said ball lenses.

6. An optical writing head as claimed in claim 1, further comprising a light-shielding mask arranged among said ball lenses.

7. An optical writing head as claimed in claim 6, wherein said light-shielding mask is a light-shielding mask plate formed with holes corresponding to the array of said ball lenses, wherein at least either of the positioning and the fixing of said ball lenses is achieved by said light-shielding mask plate which is disposed on the output side of said ball lenses.

8. An optical writing head as claimed-in claim 1, wherein said light-emitting element array is an organic EL array.

11. An image forming apparatus comprising an optical writing head as claimed in claim 1 as an exposure head for writing an image on an image carrier.

12. An image forming apparatus as claimed in claim 11, wherein said image forming apparatus is a color image forming apparatus of a tandem type having at least two image forming stations each comprising a charging means, an exposure head, a developing means, and a transfer means which are arranged around an image carrier, wherein said color image forming apparatus forms a color image by passing a transfer medium through the respective stations.

9. A method of manufacturing an optical writing head for projecting fluxes of modulated light from light-emitting parts of a light-emitting element array or fluxes of modulated light transmitted through shutter parts of an optical shutter element array onto an image carrier to form a predetermined pattern on said image carrier, said optical writing head comprising ball lenses which are arranged such that the alignment of said ball lenses corresponds to the alignment of the light-emitting parts of said light-emitting element array or the shutter parts of said optical shutter element array, said method being characterized in that the alignment of said ball lenses is achieved by forming a pattern of holes for positioning said ball lenses to positions corresponding to the light-emitting parts of said light-emitting element array or the shutter parts of said optical shutter element array on a transparent member on the surface of said light-emitting element array or said optical shutter element array, and fitting said ball lenses into said holes.

10. A method of manufacturing an optical writing head as claimed in claim 9, wherein said pattern of holes is composed of a member which also functions as a light-shielding means.

13. An organic EL array exposure head comprising a long substrate, an array of organic EL elements aligned just like pixels aligned in at least of one row, and a barrier plate, formed with optical holes for preventing crosstalk of light i.e. a phenomenon that fluxes of light emitted from the light-emitting parts of adjacent organic EL elements are immixed at the condensing position of light from the light-emitting part of either organic EL element, wherein said barrier plate is arranged on the output side of said array of the organic EL elements.

14. An organic EL array exposure head as claimed in claim 13, wherein plus lenses are arranged at positions of said holes of said barrier plate, respectively.

15. An organic EL array exposure head as claimed in claim 13, wherein the coefficient of linear expansion of said substrate and the coefficient of linear expansion of said barrier plate are substantially equal to each other.

16. An organic EL array exposure head as claimed in claim 13, wherein said barrier plate is a metal plate formed with holes.

17. An organic EL array exposure head as claimed in claim 13, wherein said barrier plate is made of a resin with holes-which is formed by molding.

18. An organic EL array exposure head as claimed in claim 13, wherein said barrier plate and said substrate are integrally formed.

19. An organic EL array exposure head as claimed in claim 14, wherein the level of the output-side surface of said barrier plate is higher than the level of said plus lenses.

20. An organic EL array exposure head as claimed in claim 14, wherein the level of the output-side surface of said barrier plate is lower than the level of said plus lenses.

21. An organic EL array exposure head as claimed in claim 13, wherein the inner surface of said each hole of said barrier plate has light reflectivity.

22. An organic EL array exposure head as claimed in claim 13, wherein the inner surface of said each hole of said barrier plate has light absorptivity.

23. An organic EL array exposure head as claimed in claim 14, wherein said plus lenses are made of a resin.

24. An organic EL array exposure head as claimed in claim 23, wherein said plus lenses are formed within said holes of said barrier plate by the inkjet method.

25. An organic EL array exposure head as claimed in claim 23, wherein said plus lenses are formed within said holes of said barrier plate by a molding (replica) method

26. An organic EL array exposure head as claimed in claim 14, wherein said plus lenses are made of glass.

27. An-organic EL array exposure head as claimed in claim 14, wherein said plus lenses are ball lenses.

28. An organic EL array exposure head as claimed in claim 13, wherein said each organic EL element emits light from its anode side.

29. An organic EL array exposure head as claimed in claim 13, wherein said each organic EL element emits light from its cathode side.

30. An organic EL array exposure head as claimed in claim 13, wherein said each organic EL element is of a polymer type.

31. An organic EL array exposure head as claimed in claim 13, wherein said each organic EL element is of a low-molecular type.

32. An organic EL array exposure head as claimed in claim 13, wherein the light emission of said each organic EL element is controlled by a TFT disposed on said substrate.

33. An image forming apparatus comprising an organic EL array exposure head as claimed in claim 13 as an exposure head for writing an image on an image carrier.

34. An image forming apparatus as claimed in claim 33, wherein said image forming apparatus is a color image forming apparatus of a tandem type having at least two image forming stations each comprising a charging means, an exposure head, a developing means with toner, and a transfer means which are arranged around an image carrier, wherein said color image forming apparatus forms a color image by passing a transfer medium through the respective stations.

35. An image forming apparatus as claimed in claim 34, satisfying both the following relations: