JPH1148522A - Optical printer head - Google Patents

Abstract

(57) [Summary] [Problem] Since the light emitting characteristics of LED elements differ from one LED array to another, a printing operation may cause uneven light emission, which causes uneven density. A transparent substrate having a plurality of wiring conductors attached to a lower surface thereof and a plurality of light emitting element arrays having a plurality of light emitting elements and a large number of terminal electrodes on an upper surface are formed by a transparent resin.
an optical printer head which is attached via an anisotropic conductive adhesive 6 in which metal particles 6b are added to a, and wherein the terminal electrode 5 and the wiring conductor 2 are electrically connected by the metal particles 6b. The light emitting element array 3
And / or anisotropic conductive adhesive 6 located on each light emitting element 4
Alternatively, the anisotropic conductive adhesive 6 located on both sides of the light emitting element 4
Is removed with a laser beam irradiated from the transparent substrate 1 side to form an optical printer head.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical printer head such as an LED printer head used as an exposure means for an electrophotographic printer or the like.

[0002]

2. Description of the Related Art Conventionally, an optical printer head used as an exposure means of an electrophotographic printer or the like has, for example, a plurality of light emitting diode arrays (hereinafter, referred to as a plurality of light emitting diode arrays (hereinafter, referred to as "a") on a lower surface of a transparent substrate on which wiring conductors of a predetermined pattern are adhered. Each of the light emitting diode elements (hereinafter, abbreviated as LED elements) of the LED array has a structure in which a light emitting surface faces the transparent substrate.
A predetermined power based on an external printing signal,
The LED elements individually emit light selectively, and the emitted light is irradiated onto an external photosensitive member via a lens member to form a predetermined latent image on the photosensitive member surface, thereby functioning as an optical printer head.

The LED array has, on its upper surface, a large number of LED elements arranged linearly and a large number of terminal electrodes electrically connected to the respective LED elements. Are individually connected to corresponding wiring conductors on the lower surface of the transparent substrate to be attached to the lower surface of the transparent substrate.

Further, an anisotropic conductive adhesive excellent in simplicity of connection work and the like is used for electrical connection between the terminal electrode and the wiring conductor. This anisotropic conductive adhesive is obtained by adding metal particles (diameter: 5 to 10 μm) such as Ni, Ag, Au, and Pt at a predetermined ratio to a resin component such as an epoxy resin. The liquid material of the anisotropic conductive adhesive is applied to a predetermined region on the lower surface of the transparent substrate, and the resin component is thermally cured while pressing the upper surface of the LED array against the applied surface, thereby bringing the upper surface of the LED array to the transparent substrate. The terminal electrode is adhered to the lower surface, and at the same time, the terminal electrode is electrically connected to the wiring conductor via the metal particles.

[0005]

In such a conventional optical printer head, the LED array is manufactured by a conventionally known semiconductor manufacturing technique.
In this semiconductor manufacturing technology, a large number of LED arrays of 1000 to 1500 pieces are cut out from one semiconductor wafer to manufacture a large amount at a time. For this reason, the light emission characteristics of the LED elements are different for each LED array due to the number of crystal defects and epi defects existing in the semiconductor wafer, or dimensional variations of the LED elements and terminal electrodes. When an optical printer head is assembled by selecting a required number of arrays at random, light-emitting variations of about ± 15 to 25% may occur during a printing operation, which is a major cause of density unevenness.

In order to solve the above-mentioned drawbacks, it is conceivable to assemble an optical printer head by selecting only LED arrays having similar light emitting characteristics. In this case, however, the required number of LED arrays having similar light emitting characteristics is required. If the LED array is less than the LED array, the LED array will not be used, and such an odd LED array must be stored in good condition until the required number of LED arrays with similar emission characteristics are found. This has the disadvantage that the manufacturing process of the optical printer head is complicated.

[0007]

SUMMARY OF THE INVENTION The present invention has been devised in view of the above-mentioned drawbacks. An optical printer head according to the present invention comprises a transparent substrate having a large number of wiring conductors attached to a lower surface thereof, and a large number of wiring substrates provided on an upper surface thereof. A light emitting element and a plurality of light emitting element arrays having a large number of terminal electrodes are attached via an anisotropic conductive adhesive in which metal particles are added to a transparent resin, and the terminal electrodes and the wiring conductors are An optical printer head electrically connected by the metal particles, wherein an anisotropic conductive adhesive and / or an anisotropic conductive adhesive are provided on each light emitting element of the light emitting element array.
Or, the anisotropic conductive adhesive located on both sides of the light emitting element, at least partially removed by the laser light irradiated from the transparent substrate side, characterized in that the transmission of light from the light emitting element array is adjusted. Is what you do.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a longitudinal sectional view showing an embodiment of the optical printer head of the present invention. FIG. 2 is a transverse sectional view showing a main part of the optical printer head before removing an anisotropic conductive adhesive. 2 is a wiring conductor, 3 is an LED array as a light emitting element array, 4 is an LED element as a light emitting element, 5 is a terminal electrode, 6 is an anisotropic conductive adhesive, and 6a is an anisotropic conductive adhesive 6. The transparent resin 6b as an agent component is metal particles added to the anisotropic conductive adhesive 6.

The transparent substrate 1 is made of a light-transmitting electrically insulating material such as borosilicate glass, soda glass, quartz, sapphire, crystallized glass, and the like, and a plurality of wiring conductors 2 and It supports a plurality of LED arrays 3 and the like.

The plurality of wiring conductors 2 are used to supply power from an external power supply to each LED element 4 of the LED array 3 described later, and are covered with a predetermined pattern on the lower surface of the transparent substrate 1. Weared and formed. As a specific method of forming the wiring conductor 2, for example, a metal paste such as copper is printed on the lower surface of the transparent substrate 1 by a conventionally known screen printing and the like, and is baked, or a conductive material such as aluminum is printed. This is performed by sputtering a material and finely processing the material into a predetermined pattern by photolithography.

On the lower surface of the transparent substrate 1 on which the wiring conductor 2 is attached, a plurality of LED arrays 3 are attached in a line. As shown in FIG. 3, the LED array 3 has a large number of LEDs linearly arranged on its upper surface.
It has an element 4 and a number of terminal electrodes 5 individually connected to the element 4. By applying a predetermined power to each LED element 4 via this terminal electrode 5,
The elements 4 are made to selectively emit light individually.
The light emitted from the LED element 4 is applied to the external photoconductor P via the transparent substrate 1 and the lens 7 disposed above the substrate 1, whereby a predetermined latent image is formed on the photoconductor surface P. Is done.

Incidentally, the LED array 3 is manufactured in large quantities at a time by a conventionally known semiconductor manufacturing technique. Specifically, for example, when manufacturing a GaAsP-based LED array, first, a wafer made of GaAs is heated to a high temperature in a furnace and AsH ₃ (arsine), PH ₃ (phosphine), and Ga (gallium) are appropriately added. The n-type semiconductor GaAsP (gallium-
A single crystal of arsenic-phosphorus is grown, and then a windowed film of Si ₃ N ₄ (silicon nitride) is deposited on the surface of the GaAsP single crystal, and the window is exposed to a gas of Zn (zinc).
Forming a p-type semiconductor by diffusing Zn into a part of the GaAsP single crystal of the type semiconductor to form a pn junction;
Such a semiconductor wafer is manufactured by dicing a large number of LED elements, for example, an LED element group including 64 LED elements as one unit, and cutting out an LED array from one semiconductor wafer in large quantities.

The LED array 3 is in contact with the lower surface of the transparent substrate 1 via an anisotropic conductive adhesive 6, and a terminal is formed by metal particles 6b added to the anisotropic conductive adhesive 6. The electrode 5 is electrically connected to the wiring conductor 2.

The pre-anisotropic conductive adhesive 6 includes a transparent resin 6a such as an epoxy resin or an acrylic resin as an adhesive component.
Of metal particles 6b (diameter 5 to 10 μm) of Ni, Ag, Au, Pt or the like as a conductive member at a ratio of 10 to 90% by weight, and the metal particles 6 in the anisotropic conductive adhesive 6 are used.
b is sandwiched between the terminal electrode 5 and the wiring conductor 2 to act as a conductive member for conducting the two, and the transparent resin 6a acts as an adhesive for adhering the transparent substrate 1 and the LED array 3 to the LED array. 3 and the transparent substrate 1 are electrically and mechanically connected.

The light transmittance of the anisotropic conductive adhesive 6 is set in the range of 60 to 90%, and the liquid of the anisotropic conductive adhesive 6 is coated with the wiring conductor 2. A predetermined area on the lower surface of the transparent substrate, that is, an area where the LED array 3 is to be attached, is applied using a conventionally known printing technique or a dispenser, and then, the plurality of LEs obtained as described above are applied.
The D arrays 3 are arranged in a line on the application surface of the anisotropic conductive adhesive 6, and heat is applied to the anisotropic conductive adhesive 6 in a state where each LED array 3 is pressed against the transparent substrate 1. LE by curing the transparent resin 6a in the conductive adhesive 6 by heat.
The D array 3 is attached to the lower surface of the transparent substrate 1.

The anisotropic conductive adhesive 6
Is that portions of the LED array 3 located on the LED elements 4 or on both sides of the LED elements 4 are removed by the laser light emitted from the transparent substrate 1 side. The light emission output is adjusted. Such adjustment of the light emission output is performed by L
When the anisotropic conductive adhesive 6 is present on the LED elements 4 of the ED array 3, a part of the light emitted from the LED elements 4 hits the opaque metal particles 6 b in the anisotropic conductive adhesive 6, and And the anisotropic conductive adhesive 6 on both sides of the LED element 4.
When the LED exists, the light emitted from the LED element 4 is an LED.
It utilizes the property that the light is hardly leaked to both sides of the element 4 and the intensity of the light irradiated on the photoconductor P is maintained at a high level. FIG. 4A shows the small LED array 3.
As shown in the figure, the anisotropic conductive adhesive 6 on the LED elements 4 of the LED array 3 was irradiated with laser light from the transparent substrate 1 side to remove this portion, and the light emission luminance was higher than a predetermined reference value. As for the LED array 3, as shown in FIG. 4B, the anisotropic conductive adhesive 6 located on both sides of the LED element 4 is irradiated with laser light from the transparent substrate 1 side to remove this portion. The laser beam used for removing the anisotropic conductive adhesive 6 has a wavelength of 355 nm,
32nm, 1064nm, output energy is 1.2 ~
6.0 mJ / pulse, a pulse width of 3 to 10 ns, and a beam diameter φ of 1 to 2 μm are used.

As described above, by partially removing the anisotropic conductive adhesive 6 on each LED array 3 according to the light emission luminance of the LED array, the light output of each LED array 3 can be made substantially uniform. This makes it possible to obtain a good print without density unevenness. When the anisotropic conductive adhesive 6 is to be removed, the anisotropic conductive adhesive 6 on the LED element 4 is removed if the light emission luminance of the LED array 3 is smaller than a predetermined reference value. As a result, more light is guided to the photoconductor P side. For this reason, it is possible to effectively prevent a decrease in the overall intensity of the light radiated on the photoconductor P, whereby the printing quality can be maintained at a high level.

A plurality of lenses 7 corresponding one-to-one with the LED array 3 are provided above the transparent substrate 1 on which the LED array 3 is attached, and a ground wiring 8 and an individual wiring 9 are provided below. The circuit boards 10 provided on the upper surface are respectively arranged, and the circuit board 10 and the above-mentioned transparent substrate 1
It has a structure in which the array 3 is sandwiched.

The lens 7 is an LED whose optical axis corresponds to the LED.
It is arranged so as to be located substantially at the center of the array 3, and LE
The light emitted from each LED element 4 of the D array 3 is enlarged at a predetermined magnification, and the light is irradiated and imaged on the photoconductor surface P. The lens 7 is manufactured by injection molding a transparent resin such as an acrylic resin or a polycarbonate resin, or by press-molding a translucent inorganic material such as glass, and is formed of a liquid crystal polymer or the like. It is fixed at a position separated from the transparent substrate 1 by a predetermined distance by a plate, a housing, or the like.

The substrate of the circuit board 10 is formed of a liquid crystal polymer having a coefficient of thermal expansion of -1 × 10 ^{−6 to} 5 × 10 ⁻⁶ / ° C., polyimide resin, polyester, or the like. Are connected to a ground electrode (not shown) on the lower surface of the LED array, and the individual wiring 9 is electrically and mechanically connected to the wiring conductor 2 on the lower surface of the transparent substrate via solder or the like.

Thus, the above-described optical printer head of this embodiment applies power from an external power supply to the LED elements 4 of the LED array 3 attached to the lower surface of the transparent substrate 1 via the wiring conductors 2 and the terminal electrodes 5. The LED element 4 of each LED array 3 is selectively illuminated and driven based on a printing signal, and the illuminated light is radiated and imaged on an external photoconductor P via a lens 7 so as to form an image on the photoconductor surface P. By forming a predetermined latent image, it functions as an optical printer head.

It should be noted that the present invention is not limited to the above-described embodiment, and various changes and improvements can be made without departing from the scope of the present invention. The head is applied to an LED printer head as an example. However, the present invention can be applied to other optical printer heads such as an EL head, a plasma dot head, a liquid crystal shutter head, a fluorescent head, and a PLZT. It is.

[0023]

According to the optical printer head of the present invention, the anisotropic conductive adhesive located on the light emitting element of the light emitting element array or the anisotropic conductive adhesive located on both sides of the light emitting element is supplied with a constant power. Since the light emission output of each light emitting element array is adjusted according to the light emission luminance of the light emitting element array when the voltage is applied, the light emission output of each light emitting element array can be made substantially uniform. It is possible to obtain a good print without density unevenness.

In the optical printer head according to the present invention, when the light emission luminance of the light emitting element array is smaller than a predetermined reference value, the anisotropic conductive adhesive on the light emitting element is irradiated with laser light and removed. As a result, more light is guided to the photoconductor side, so that it is possible to effectively prevent a decrease in the overall intensity of light irradiated on the photoconductor, Thus, printing quality can be maintained at a high level.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of an optical printer head of the present invention.

FIG. 2 is a cross-sectional view showing a main part of the optical printer head before removing an anisotropic conductive adhesive.

FIG. 3 is a plan view showing an upper surface of an LED array as a light emitting element array.

FIGS. 4A and 4B are enlarged views of a main part for describing a method of removing an anisotropic conductive adhesive 6;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 transparent substrate 2 wiring conductor 3 LED array 4 LED element 5 terminal electrode 6 anisotropic conductive adhesive 6 a transparent resin 6 b metal particles

Claims (1)

[Claims] 1. A transparent substrate having a plurality of wiring conductors attached to a lower surface thereof, and a plurality of light emitting device arrays having a plurality of light emitting devices and a plurality of terminal electrodes on an upper surface thereof, wherein metal particles are added to a transparent resin. An optical printer head, wherein the light emitting elements are attached via an anisotropic conductive adhesive and the terminal electrodes and the wiring conductors are electrically connected by the metal particles. The anisotropic conductive adhesive located on the upper side and / or the anisotropic conductive adhesive located on both sides of the light emitting element is at least partially removed by the laser light irradiated from the transparent substrate side, and the light emitting element array An optical printer head that controls light transmission.