JP2000135814A - Optical printer head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a part of an anisotropic conductive adhesive from flowing to a region just under a light emitting element by a constitution wherein the flowing of the anisotropic conductive adhesive is blocked by a dam section even when it tends to flow to a side of the light emitting element during the assembling of an optical printer head. SOLUTION: There is disclosed an optical printer head consisting of a transparent substrate 1 having a circuit pattern 2 at the top face thereof and a light emitting member 3 having a light emitting element 4 and a terminal electrode 5 provided to the lower face thereof and being attached to the transparent substrate 1. The circuit pattern 2 and terminal electrode 5 are electrically connected with an anisotropic conductive adhesive 6. A dam section 7 made from a material having surface free energy smaller than a surface tension of an organic component included in the anisotropic conductive adhesive 6 is provided between the light emitting element 4 of the light emitting member 3 and terminal electrode 5.

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 used as exposure means for an electrophotographic printer or the like.

[0002]

2. Description of the Related Art Conventionally, optical printer heads such as LED printer heads have been used as exposure means for electrophotographic printers and the like.

Such an optical printer head has a light emitting diode array chip 13 on an upper surface of a transparent substrate 11 on which a plurality of circuit wirings 12 are formed as shown in FIG.
(Hereinafter, abbreviated as an LED array chip).

On the lower surface of the LED array chip 13,
A number of light emitting diode elements 14 arranged in a straight line,
A large number of terminal electrodes 15 which are individually electrically connected to the element 14 are provided. By electrically connecting these terminal electrodes 15 to the circuit wiring 12 on the upper surface of the transparent substrate, the power supply power is reduced. The light is supplied to the light emitting diode element 14 via the terminal 12 and the terminal electrode 15 so that the light emitting diode element 14 selectively emits light individually.
The light emitted from the light emitting diode element 14 is applied to an external photoconductor via an optical system such as a lens (not shown) to form a predetermined latent image.

As a connecting member for electrically connecting the circuit wiring 12 and the terminal electrode 15 of the optical printer head described above, an anisotropic conductive adhesive 16 excellent in simplicity of connection work and the like is used.
It has been proposed to use The anisotropic conductive adhesive 16 is formed by adding fine metal particles such as Ni, Ag, Au, and Pt to an organic component composed of a precursor such as an epoxy resin. A predetermined area on the upper surface, specifically, an area where the circuit wiring 12 and the terminal electrode 15 face each other, and the lower surface of the LED array chip 13 is pressed against the applied surface, and the metal in the anisotropic conductive adhesive 16 The LED array chip 13 is mounted by sandwiching the fine particles between the circuit wiring 12 and the terminal electrode 15,
At the same time, the circuit wiring 12 and the terminal electrode 15 are electrically connected via the fine metal particles in the anisotropic conductive adhesive 16.

[0006]

However, in this conventional optical printer head, the anisotropic conductive adhesive 16 is used for the electrical connection between the circuit wiring 12 and the terminal electrode 15, so that the optical printer head is not used. When the anisotropic conductive adhesive 16 flows at the time of assembling or the like, a part of the adhesive may extend to a region directly below the light emitting diode element 14.
In this case, a part of the light emitted from the light emitting diode element 14 hits the metal fine particles and the like in the anisotropic conductive adhesive 16 and diffuses in all directions, and a part of the diffused light is irradiated on the photoconductor as unnecessary light. Alternatively, there has been a disadvantage that the intensity of light applied to the photoreceptor decreases and the latent image becomes unclear.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks. An optical printer head according to the present invention has a transparent substrate having circuit wiring on an upper surface, and is mounted on the transparent substrate. An optical printer head comprising: a light emitting element having a light emitting element and a terminal electrode on a lower surface, wherein the circuit wiring and the terminal electrode are electrically connected to each other via an anisotropic conductive adhesive. And, between the light emitting element of the light emitting member and the terminal electrode, a dam portion is provided with a material having a surface free energy smaller than the surface tension of the organic component contained in the anisotropic conductive adhesive. It is characterized by having.

[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 cross-sectional view of an optical printer head according to one embodiment of the present invention. FIG. 2 is a top view of a transparent substrate used in the optical printer head of FIG.
Is a circuit wiring, 3 is an LED array chip as a light emitting member, 4 is a light emitting diode element as a light emitting element, 5 is a terminal electrode, 6 is an anisotropic conductive adhesive, and 7 is a dam part.

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 circuit wirings 2 and a plurality of Of the LED array chip 3 and the like, and the light emitted from the light emitting diode element 4 of the LED array chip 3 is transmitted to the lower surface side.

The circuit wiring 2 on the lower surface of the transparent substrate is provided with each light emitting diode element 4 of the LED array chip 3 described later.
And serves as a power supply wiring for supplying electric power from an external power supply to the transparent substrate 1 made of, for example, a metal such as Cu, Ag, Au, or Al, and employing a conventionally known thick film method or thin film method. Is attached and formed in a predetermined pattern with a predetermined thickness on the upper surface of the substrate.

On the upper surface of the transparent substrate 1 on which the circuit wirings 2 are formed, a plurality of LED array chips 3 are attached in a line. The LED array chip 3
Has, on its lower surface, a large number of light-emitting diode elements 4 arranged in a straight line and a large number of terminal electrodes 5 individually connected to the element 4. By being electrically connected to the circuit wiring 2 of the substrate 1, the power from an external power supply is applied to the light emitting diode element 4 via the circuit wiring 2 and the terminal electrode 5 during the printing operation, At a predetermined intensity. The light emitted from the light emitting diode element 4 is applied to an external photoconductor via an optical system such as a transparent substrate 1 and a lens (not shown) disposed below the substrate 1,
A predetermined latent image is formed.

The LED array chip 3 is made of a conventionally known semiconductor manufacturing technology, specifically, a GaAsP-based LED.
When fabricating an array chip, first, a GaAs wafer is heated to a high temperature in a furnace, and AsH ₃ and P
An n-type semiconductor GaAsP single crystal is grown on the surface of the wafer by contacting a gas containing an appropriate amount of H ₃ and Ga, and then a windowed film of Si ₃ N ₄ is deposited on the surface of the GaAsP single crystal. A window is exposed to a gas of Zn, and Zn is diffused into a part of a GaAsP single crystal of an n-type semiconductor to form a p-type semiconductor, thereby providing a pn junction. For example, 6
It is manufactured by dicing four light emitting diode elements into one light emitting diode element group as one unit, and cutting out a plurality of LED array chips from a semiconductor wafer.

Then, such an LED array chip 3
An anisotropic conductive adhesive 6 is interposed between the terminal electrode 5 and the circuit wiring 2 on the upper surface of the transparent substrate, the electrical connection between the terminal electrode 5 and the circuit wiring 2 by the adhesive 6, and the LED The mechanical connection between the array chip 3 and the transparent substrate 1 is made.

The anisotropic conductive adhesive 6 contains Ni, Ag, Au, P in an organic component comprising a precursor such as an epoxy resin.
Metal particles such as t (particle size: 5 μm to 10 μm) are added and mixed in an amount of, for example, 10 to 30% by weight, and the organic component is applied to both the lower surface of the LED array chip 3 and the upper surface of the transparent substrate 1. In this way, the two are adhered to each other, and the metal particles are sandwiched between the circuit wiring 2 and the terminal electrode 5 to electrically connect the two.

Further, on the upper surface of the transparent substrate 1 and L
Between the light emitting diode element 4 and the terminal electrode 5 of the ED array chip 3, a dam section 7 having a mountain-shaped cross section is provided with its top abutting on the lower surface of the LED array chip 3.

The dam portion 7 has an organic component contained in the anisotropic conductive adhesive 6 having a surface tension of 43 to 47 dyne.
/ Cm (measured under a temperature condition of 20 ° C.), the surface free energy of the surface free energy smaller than the surface tension of the organic component, for example, 18.5 to 37 dyne / cm (measured under a temperature condition of 20 ° C.) It is formed of a material having As a specific material of the dam portion 7, a silicon-based resin, polytetrafluoroethylene, polypropylene, polyethylene, polystyrene, polyvinyl alcohol, or the like is used.

Since the dam portion 7 is provided on the upper surface of the transparent substrate 1 and between the light emitting diode element 4 and the terminal electrode 5 of the LED array chip 3 as described above, the dam portion 7 is anisotropic when assembling an optical printer head. Even if the conductive adhesive 6 tries to flow toward the light emitting diode element 4, the flow is blocked by the dam portion 7, and a part of the anisotropic conductive adhesive 6 reaches the region directly below the light emitting diode element 4. Can be effectively prevented.

Further, the dam portion 7 is formed of a material having a surface free energy smaller than the surface tension of the organic component contained in the anisotropic conductive adhesive 6, and the surface of the dam portion 7 is formed of the organic component. , It is possible to reliably prevent the organic component from trying to enter the light emitting diode element 4 side along the surface of the dam portion 7. Therefore, the anisotropic conductive adhesive 6 does not exist in the region directly below the light emitting diode element 4, and the light emitted from the light emitting diode element 4 is applied to the photoreceptor while maintaining its intensity substantially.

Further, in this case, since the diffusion of light by the anisotropic conductive adhesive 6 is effectively prevented, unnecessary light is not irradiated to the photoreceptor, so that a clear and good latent image is obtained. An image can be formed on the photoconductor.

The surface free energy of such a dam portion 7 is 1 to 10 dyn more than the surface tension of the organic component.
It is preferable to set it smaller by e / cm.

By disposing the dam portion 7 not only between the light emitting diode element 4 and the terminal electrode 5 but also along the outer periphery of the LED array chip 3, the dam portion 7 can be used when assembling an optical printer head. It is possible to effectively prevent the anisotropic conductive adhesive 6 from spreading outward, thereby reducing the reflection of light. Therefore, it is preferable to arrange the dam portion 7 along the outer periphery of the LED array chip 3.

If a black pigment such as iron oxide or carbon is added in an amount of 1 to 50% by weight to the anisotropic conductive adhesive 6, a part of the light emitted from the light emitting diode element 4 is anisotropic conductive adhesive. Even if it enters the adhesive 6, most of it can be well absorbed by the black pigment, and the diffusion and reflection of light can be more reliably prevented. Therefore, it is preferable to add 1 to 50% by weight of a black pigment in the anisotropic conductive adhesive 6. Here, the reason why the addition ratio of the black pigment to the anisotropic conductive adhesive 6 is set to 50% by weight or less is to prevent a decrease in the adhesive strength of the anisotropic conductive adhesive 6.

The dam portion 7 is formed by applying a precursor of the resin described above to a predetermined area on the upper surface of the transparent substrate by a conventionally known screen printing or dispenser and curing the same.

The LED array chip 3 is attached to the transparent substrate 1 by first printing and applying a paste-like anisotropic conductive adhesive 6 to a predetermined area on the upper surface of the transparent substrate by a conventionally known screen printing or the like. Next, the lower surface of the LED array chip 3 is pressed against the application surface so that the terminal electrode 5 is positioned on the corresponding circuit wiring 2, and the fine metal particles in the anisotropic conductive adhesive 6 are removed from the circuit wiring 2 and the terminal electrode 2. This is performed by sandwiching between the five.

In the optical printer head described above, the power from the external power supply is applied to the light emitting diode element 4 of the LED array chip 3 mounted on the upper surface of the transparent substrate 1 via the circuit wiring 2 and the terminal electrode 5, LED array chip 3
The light emitting diode elements 4 are selectively emitted and driven individually on the basis of the printing data, and the emitted light is irradiated and imaged on an external photoconductor via an optical system such as a lens to form a predetermined latent image. Forming an optical printer head.

The present invention is not limited to the above-described embodiment, and various changes and improvements can be made without departing from the gist of the present invention. For example, in the above-described embodiment, a space between the light emitting diode element 4 of the LED array chip 3 and the transparent substrate 1 is filled with a transparent resin such as an acrylic resin or an epoxy resin having a light transmittance of 90% or more. The light emitting diode element 4 may be formed of a transparent material having a transmittance of 90% or more, and a part thereof may be extended to a region immediately below the light emitting diode element 4. Is irradiated on the photoconductor, thereby forming a clear latent image on the photoconductor.

In the above embodiment, the LED array chip 3 may be covered with a sealing material to prevent corrosion.

Further, in the above embodiment, the LED printer head has been described as an example, but other optical printer heads,
For example, the present invention is applicable 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.

[0029]

According to the present invention, even when the anisotropic conductive adhesive flows to the light emitting element side when assembling an optical printer head or the like, the anisotropic conductive adhesive is blocked and damped by the dam portion, and is anisotropically. It is possible to reliably prevent a part of the conductive adhesive from reaching the region directly below the light emitting element. Therefore, it is possible to irradiate the light emitted from the light emitting element to an external photosensitive member while maintaining a high intensity, and it is possible to form a clear and good latent image.

[Brief description of the drawings]

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

FIG. 2 is a top view of a transparent substrate used in the optical printer head of FIG.

FIG. 3 is a sectional view of a conventional optical printer head.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Transparent substrate, 2 ... Circuit wiring, 3 ... LED
Array chip (light emitting member), 4 light emitting diode element (light emitting element), 5 terminal electrode, 6 anisotropic conductive adhesive, 7 dam part

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2C162 AG11 FA17 FA23 5F041 AA14 CA04 CA35 CA38 DA04 DA15 EE25 FF13

Claims (1)

[Claims] 1. A circuit board comprising: a transparent substrate having a circuit wiring on an upper surface; and a light emitting member attached on the transparent substrate and having a light emitting element and a terminal electrode on a lower surface. An optical printer head electrically connected through an electrically conductive adhesive, wherein the anisotropic conductive adhesive is provided on an upper surface of the transparent substrate and between a light emitting element of the light emitting member and a terminal electrode. An optical printer head having a dam portion made of a material having a surface free energy smaller than the surface tension of an organic component contained therein.