JP3634962B2 - Optical printer head - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical printer head used as a light source for an electrophotographic printer or the like.
[0002]
[Prior art]
In a conventional optical printer head, for example, a plurality of light emitting diode array chips (hereinafter referred to as LED array chips) are mounted and mounted in a line on one main surface of a circuit board having a plurality of power supply wirings. Have a structure. For example, as shown in FIG. 7, the LED array chip has a plurality of light emitting diode elements 12 arranged in a straight line on the upper surface thereof, and a plurality of terminal electrodes 13 provided corresponding to the elements 12 individually. The light emitting diode element 12 is electrically connected to the power supply wiring by bonding these terminal electrodes 13 to the power supply wiring of the circuit board with a bonding wire or the like. In addition, a ground electrode is provided on the lower surface of the LED array chip 11, and the light emitting diode element 12 is caused to emit and drive by applying external power between the ground electrode and the terminal electrode 13 described above. It has become.
[0003]
Then, a plurality of lenses corresponding to each chip 11 are arranged on the light emitting diode elements 12 of the LED array chip 11 as shown in FIG. 7, and light emitted from the light emitting diode elements 12 of the LED array chip 11 is emitted. Irradiates an external photoconductor through the lens and forms a predetermined latent image on the photoconductor to function as an optical printer head.
[0004]
[Problems to be solved by the invention]
However, according to this conventional optical printer head, the same number of terminal electrodes 13 as the light emitting diode elements 12 are provided on the upper surface of the LED array chip 11. For this reason, a wide space for forming these terminal electrodes 13 is required on the upper surface of each LED array chip 11, making it difficult to reduce the size of the LED array chip 11.
[0005]
In general, the LED array chip 11 is cut out from a single semiconductor wafer by using a conventionally well-known semiconductor manufacturing technique, and a plurality of the LED array chips 11 are manufactured at a time. However, when it is difficult to downsize the LED array chip 11 as described above, the number of LED array chips 11 obtained from one semiconductor wafer cannot be increased, and the manufacturing cost of the LED array chip 11 is expensive. It also has the disadvantage of becoming.
[0006]
Further, the terminal electrode 13 of the LED array chip 11 described above has a one-to-one correspondence with each light emitting diode element 12 on the upper surface of the chip 11 by a conventionally well-known thin film forming technique, specifically, a sputtering method, a photolithography technique or the like. Since the terminal electrodes 13 are formed with a high density, the terminal electrodes 13 are often short-circuited with the adjacent terminal electrodes 13, which causes a reduction in the yield rate of the LED array chips.
[0007]
[Means for Solving the Problems]
The present invention has been devised in view of the above disadvantages. An optical printer head according to the present invention has a plurality of light emitting diode elements on the lower surface of a transparent substrate to which a plurality of power supply wirings are attached, and the element. A light emitting diode element array, in which an electrode is formed of an anisotropic conductive adhesive comprising conductive fine particles in a transparent resin, is attached so that the electrode is in contact with the power supply wiring. It is characterized by being made to do.
[0008]
The optical printer head of the present invention is characterized in that a light-shielding film provided with a window at a position corresponding to each of the light emitting diode elements is attached to the upper surface and / or the lower surface of the transparent substrate. .
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
(First form)
1 is a cross-sectional view of an optical printer head according to a first embodiment of the present invention, FIG. 2 is an enlarged view of a main part of FIG. 1, and FIG. 3 is an enlarged plan view of the optical printer head of FIG. Is a transparent substrate, 2 is a power supply wiring, 4 is a light emitting diode element, and 5 is an anisotropic conductive adhesive.
[0010]
The transparent substrate 1 is made of a light-transmitting electrically insulating material such as borosilicate glass, soda glass, quartz, sapphire, or crystallized glass, and the transparent substrate 1 has a plurality of power supply wirings 2 on its lower surface 1A. And function as a support base material for supporting the LED array chip 3.
[0011]
The power supply wiring 2 deposited on the lower surface of the transparent substrate 1 is a laminate in which a second wiring 2b made of copper or the like is partially deposited on the surface of a first wiring 2a made of ITO (indium tin oxide) or the like. The power supply wiring 2 is for supplying power from an external power source to each light emitting diode element 4 of the LED array chip 3 via an anisotropic conductive adhesive 5 described later, not shown. It is connected to an external electric circuit (such as a printer main body) via a connector or the like.
[0012]
Here, the first wiring 2a is formed from a light-transmitting conductive material such as ITO when the optical printer head is assembled when the LED array chip 3 is attached to the lower surface 1A of the transparent substrate 1. In order to effectively prevent the light of the light emitting diode element 4 arranged facing the wiring 2a from being reflected or absorbed by the first wiring 2a and to transmit more light to the upper surface side of the transparent substrate 1. In addition, one end of the first wiring 2a is tapered for the same purpose. On the other hand, the second wiring 2b is for electrically reinforcing the first wiring 2a having a relatively large specific resistance to effectively prevent the voltage drop in the power supply wiring 2. For example, the first wiring 2a When formed to a thickness of 500 mm to 1500 mm, the second wiring 2b is set to a thickness of 5 μm to 20 μm.
[0013]
When forming the power supply wiring 2 having such a two-layer structure, first, a light-transmitting conductive material such as ITO is used to form a thin film such as a sputtering method or a photolithography technology, or a screen printing method or a spray method. The first wiring 2a is deposited on the lower surface 1A of the transparent substrate 1 by finely processing the first wiring 2a into a predetermined pattern by a well-known photolithography technique. Then, a conductive paste such as a silver paste or a copper paste is printed and applied on the surface of the first wiring 2a previously formed by screen printing or the like known in the art. A wiring 2b is formed.
[0014]
And the LED array chip 3 in which the anisotropic conductive adhesive 5 formed the electrode is attached to the lower surface 1A of the transparent substrate 1 to which the power supply wiring 2 is attached.
[0015]
That is, the LED array chip 3 abuts the anisotropic conductive adhesive 5 applied on the light emitting diode element 4 to the first wiring 2 a of the power supply wiring 2, and the conductive fine particles in the anisotropic conductive adhesive 5. The light emitting diode element 4 is electrically connected to the power supply wiring 2 by using 5b as an electrode of the LED array chip 3.
[0016]
As shown in FIG. 3, the LED array chip 3 has a plurality of light emitting diode elements 4 arranged in a straight line on the upper surface thereof, and an anisotropic conductive adhesive is attached to a part of the upper surface of the light emitting diode element 4. The agent 5 has a structure in which a ground electrode (not shown) is formed on the lower surface. For example, when the light-emitting diode element 4 of the LED array chip 3 has a structure in which an n-type semiconductor layer 3b, a p-type semiconductor layer 3c, and an insulating film 3d with a window are sequentially formed on a GaAs substrate 3a. The isotropic conductive adhesive 5 is directly bonded to the p-type semiconductor layer 3c located in the window of the insulating film 3d, and a predetermined gap is provided between the anisotropic conductive adhesive 5 and the ground electrode on the lower surface of the GaAs substrate. By applying electric power, light is emitted at the junction surface 4a (pn junction surface) between the n-type semiconductor layer 3b and the p-type semiconductor layer 3c.
[0017]
In the case of an A4 size, 600 dpi optical printer head, the light emitting diode elements 4 are linearly arranged in 5120 (24 per 1 mm), for example, an LED array having 128 light emitting diode elements 4 as a unit. By arranging 40 chips 3 in a straight line, 5120 light emitting diode elements 4 are arranged and mounted on the lower surface 1 </ b> A of the transparent substrate 1.
[0018]
A plurality of such LED array chips 3 are manufactured at a time by a conventionally known semiconductor manufacturing technique. Specifically, for example, when manufacturing a GaAsP-based LED array chip 3, first, a semiconductor wafer made of GaAs is heated to a high temperature in a furnace and a gas containing appropriate amounts of AsH ₃ , PH _3, and Ga is brought into contact therewith. A single crystal of GaAsP (gallium-arsenic-phosphorus) of n-type semiconductor 3b is grown on the surface of the wafer, and then an insulating film 3d with a window of Si ₃ N ₄ (silicon nitride) is deposited on the surface of the GaAsP single crystal, Thereafter, a Zn (zinc) gas is exposed to the window portion, and Zn is diffused into a part of the GaAsP single crystal to form a p-type semiconductor layer 3c, thereby providing a pn junction. A plurality of such semiconductor wafers are formed. A plurality of light emitting diode elements, for example, 128 light emitting diode elements are manufactured at a time by dicing each light emitting diode element group as a unit. .
[0019]
On the other hand, the anisotropic conductive adhesive 5 has a transparent resin 5a such as an epoxy resin or an acrylic resin as an adhesive component, and conductive fine particles 5b (diameter 5 to 10 μm) such as ITO, Ag, Au, or Pt as a conductive component. ) In a predetermined ratio (conducting fine particle content: 10 to 90% by weight).
[0020]
The anisotropic conductive adhesive 5 positions the conductive fine particles 5b contained in the anisotropic conductive adhesive 5 between the light emitting diode element 4 and the power supply wiring 2, more specifically, in the window of the insulating film 3d of the light emitting diode element 4. The LED array chip 3 is bonded and fixed to the lower surface of the transparent substrate 1 with a transparent resin 5a by sandwiching it between the p-type semiconductor layer 3c and the power supply wiring 2 and electrically connecting them.
[0021]
When the LED array chip 3 is attached to the lower surface 1A of the transparent substrate 1, the LED array chip 3 is first liquefied in a predetermined region of the transparent substrate 1, specifically, in a region where the leading end of the power supply wiring 2 is led out. An anisotropic conductive adhesive 5 is applied in a strip shape, and the LED array chip 3 is placed thereon so that each light emitting diode element 4 is opposed to the power supply wiring 2 with the anisotropic conductive adhesive 5 sandwiched therebetween. After that, the transparent resin 5a of the anisotropic conductive adhesive 5 is heated and cured to electrically connect the power supply wiring 2 and the light emitting diode element 4 with the conductive fine particles 5b in the anisotropic conductive adhesive 5. It may be performed by connecting them automatically. In this case, even when the total number of the light emitting diode elements 4 of each LED array chip 3 is extremely large, all of them are firmly attached to the power supply wiring 2 of the transparent substrate 1 at once via the anisotropic conductive adhesive 5. Since it is electrically connected, each light emitting diode element 4 of the LED array chip 3 and the power supply wiring 2 of the transparent substrate 1 can be electrically connected in a very short time, thereby assembling the optical printer head. Improves.
[0022]
A lens (not shown) is arranged on the upper surface 1B side (above) of the transparent substrate 1 described above at a certain distance from the transparent substrate 1, and the light emitting diode element of the LED array chip 3 is arranged. The light emitted by 4 is applied to an external photoreceptor via the lens.
[0023]
Thus, the above-described optical printer head applies predetermined power to each light-emitting diode element 4 of the LED array chip 3 to selectively light-emit and drive each light-emitting diode element 4 based on the print signal. The emitted light is irradiated to an external photoconductor through a lens or the like to form a predetermined latent image on the photoconductor, thereby functioning as an optical printer head.
[0024]
According to the optical printer head of the first embodiment as described above, the electrode made of the anisotropic conductive adhesive 5 constituted by containing conductive fine particles in transparent resin on the light emitting diode element 4 of the LED array chip 3 is provided. Since this electrode is formed and directly connected to the power supply wiring 2 of the transparent substrate 1, a plurality of terminal electrodes for connecting the light emitting diode element 4 to the power supply wiring 2 on the lower surface of the chip 3. Therefore, it is possible to reduce the size of the LED array chip 3 and to improve the yield rate of the LED array chip 3.
[0025]
Further, as described above, when the individual LED array chips 3 are downsized, the number of LED array chips 3 obtained from one semiconductor wafer can be increased. In combination with this effect, the manufacturing cost of the LED array chip 3 can be greatly reduced, and the optical printer head as a product can be made inexpensive.
[0026]
Further, in the case of the optical printer head of the first embodiment, since one end portion of the power supply wiring 2 arranged to face the light emitting diode element 4 is formed of a translucent material such as ITO, it goes to the lower surface 1A side of the transparent substrate 1. Light from the light-emitting diode element 4 is less likely to be reflected or absorbed by the power supply wiring 2 toward the lower surface 1A of the transparent substrate 1, so that much of the light emitted from the light-emitting diode element 4 is latent in the photosensitive member. It is possible to contribute to image formation.
[0027]
Furthermore, if the conductive fine particles 5b in the anisotropic conductive adhesive 5 are formed of a light-transmitting material such as ITO (light transmittance of 50% or more) in the optical printer head of the first embodiment, the light-emitting diode element 4 is less likely to diffuse or be absorbed in four directions when hitting the conductive fine particles 5b in the anisotropic conductive adhesive 5. As a result, in combination with the above-described effects, more light is emitted. This makes it possible to contribute to the formation of a latent image on the photoconductor, thereby enabling formation of a very clear and good latent image. As such conductive fine particles 5b, in addition to the above-mentioned ITO, ITO, ZnO, CdO—SnO ₂ , ZnO—SnO ₂ , on the surface of inorganic particles having a particle diameter of 2 to 10 μm made of glass or transparent resin, A transparent conductive film made of CdIn ₂ O ₄ , MgIn ₂ O _3-x or the like is used by thinly depositing it to a thickness of about 500 to 5000 mm.
[0028]
(Second form)
Next, a second embodiment of the present invention will be described.
4 is a cross-sectional view of an optical printer head according to a second embodiment of the present invention, FIG. 5 is an enlarged view of a main part of FIG. 4, and FIG. 6 is an enlarged plan view of the optical printer head of FIG. Is a transparent substrate, 2 is a power supply wiring, 4 is a light emitting diode element, 5 is an anisotropic conductive adhesive, 6 is a light shielding film, and 6a is a window provided in the light shielding film. The same constituent elements as those of the first embodiment described above are indicated by common reference numerals, and the explanation of the same constituent elements and the description of the operational effects by these constituent elements are the same as those of the first embodiment. Since it is the same, it abbreviate | omits here.
[0029]
This optical printer head of the second form is different from that of the first form in that instead of providing an insulating film with a window of Si ₃ N _{4 on} the upper surface of the LED array chip 3, the upper surface 1B of the transparent substrate 1 The light-shielding film 6 provided with the window portion 6a is attached at a position corresponding to each of the light-emitting diode elements 4.
[0030]
Since no insulating film with a window is provided on the upper surface of the LED array chip 3, almost the entire upper surface is a light emitting region, and the light emitted from the LED array chip 3 is transmitted through the window 6 a of the light shielding film 6. Only the light passing through the lens is irradiated to the external photoconductor via a lens (not shown).
[0031]
The light shielding film 6 is deposited and formed on the upper surface 1B of the transparent substrate 1 with a thickness of 1 to 100 μm by using a light shielding resin material to which iron oxide, carbon or the like is added, and is led upward by the window 6a. Even if the light emitting region of the light emitting diode element is not defined to have a certain size by the Si ₃ N ₄ window insulating film, the light emitting dots formed on the photoconductor The size of can be made almost constant. Therefore, the step of forming an insulating film with a window of Si ₃ N ₄ at the time of manufacturing the LED array 3 becomes unnecessary, and it is possible to improve the productivity of the optical printer head and reduce the manufacturing cost.
[0032]
The present invention is not limited to the first and second embodiments described above, and various modifications can be made without departing from the gist of the present invention.
[0033]
For example, in the first embodiment described above, one end portion of the power supply wiring 2 is tapered, but the one end portion of the power supply wiring 2 may be formed with a width equal to that of other portions. In this case, the power supply wiring 2 must be formed of a light-transmitting conductive material such as ITO so that light emitted from the light emitting diode element 4 can be transmitted through the power supply wiring 2 satisfactorily.
[0034]
Furthermore, in the first embodiment described above, a part of the power supply wiring 2 connected to the light emitting diode element 4 is formed of a light-transmitting conductive material, but one end of the power supply wiring 2 is made of a light-shielding metal such as Al or Cu. You may form with a material. Also in this case, one end portion of the power supply wiring 2 is tapered so that more light emitted from the light emitting diode element can be transmitted to the upper surface side of the transparent substrate 1, and the width of this portion is the width of the light emitting diode element 4. It is preferable to make it sufficiently thin.
[0035]
In the optical printer head of the second embodiment, the light shielding film 6 is formed only on the upper surface 1B of the transparent substrate 1, but instead of this, the light shielding film 6 is formed only on the lower surface 1A of the transparent substrate 1, or The light shielding film 6 may be formed on both surfaces of the transparent substrate 1, that is, both the upper surface 1B and the lower surface 1A.
[0036]
Further, in the second embodiment, when the light from the LED array chip 3 is imaged on the photoconductor using one lens, the size of the window 6a of the light shielding film 6 is gradually increased from the center toward the outside. If this is done, the beam blur caused by the aberration of the lens can be effectively corrected, and the print quality can be improved.
[0037]
【The invention's effect】
According to the optical printer head of the present invention, an electrode made of an anisotropic conductive adhesive comprising conductive fine particles in a transparent resin is formed on the surface (upper) of the light emitting diode element, and this electrode is formed on the lower surface of the transparent substrate. It is necessary to separately provide a plurality of terminal electrodes for connecting the element to the power supply wiring on the upper surface of the LED array chip on which the light emitting diode element is formed. Therefore, it is possible to reduce the size of the LED array chip and improve the yield rate.
[0038]
Also, according to the optical printer head of the present invention, as described above, since the LED array chip or the like can be reduced in size, the number of LED array chips or the like obtained from one semiconductor wafer can be increased. Therefore, the manufacturing cost of the LED array chip or the like can be greatly reduced, and the optical printer head as a product can be made inexpensive.
[0039]
Furthermore, according to the optical printer head of the present invention, a light-shielding film having a window portion provided at a position corresponding to each of the light-emitting diode elements is attached to the upper surface and / or the lower surface of the transparent substrate. A light emitting dot of a predetermined size can be obtained without forming an insulating film with a window on the surface of the element, and this can also be used for improving the productivity of the optical printer head and reducing the manufacturing cost. .
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an optical printer head according to a first embodiment of the present invention.
FIG. 2 is an enlarged view of a main part of FIG.
FIG. 3 is an enlarged plan view of the optical printer head of FIG. 1 viewed from above.
FIG. 4 is a cross-sectional view of an optical printer head according to a second embodiment of the present invention.
FIG. 5 is an enlarged view of a main part of FIG.
6 is an enlarged plan view of the optical printer head of FIG. 4 as viewed from above.
FIG. 7 is a plan view of an LED array chip used in a conventional optical printer head.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Transparent substrate 2 ... Feeding wiring 3 ... LED array chip (light emitting diode array chip)
4... Light emitting diode element 5... Anisotropic conductive adhesive 6...

Claims (2)

Anisotropic conductive bonding comprising a plurality of light emitting diode elements on the lower surface of a transparent substrate to which a plurality of power supply wirings are attached, and electrodes comprising conductive fine particles in transparent resin on the elements. An optical printer head in which a light emitting diode element array formed of an agent is attached so that the electrode is in contact with the power supply wiring. 2. The optical printer head according to claim 1, wherein a light-shielding film provided with a window at a position corresponding to each of the light emitting diode elements is attached to the upper surface and / or the lower surface of the transparent substrate.

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