JPH0255159A - Optical printer head - Google Patents

Abstract

PURPOSE:To obtain an image of high printing quality, and to attain an optical printer head having a simple structure including no optical system such as a focusing element, etc. by fixedly connecting the light emitting face of a LED array to a metal plate having many through pores, fixedly connecting a wiring pattern formed on an insulating plate to the array, and using the metal plate as the common electrode of the array. CONSTITUTION:A LED array 1 secured to a metal plate 3 is diced from its rear face side to electrically isolate light emitting elements. In this case, dicing grooves 8 arrives at least at a P-type layer 7. The LED array 1 and the plate 3 isolated at each element are placed fixedly on a circuit board 11. An insulating layer 12 having a satisfactory thermal transfer rate is formed on a heat sink plate 4 made of metal on the board 11, and a wiring pattern 5 and resist 9 are formed on the layer 12. The N-type electrode of the LED array 1 is secured to the pattern 5 with conductive adhesive 15. The plate 2 is secured onto the resist 9 of the board 11 bent in a protrusion state with adhesive to hermetically seal the LED array 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical printer head using an electrophotographic method using an LED array as a light emitting source, and specifically relates to a mounting structure of an optical printer head.

[Prior Art] An optical printer head using a known IJKD array disclosed in Japanese Unexamined Patent Publication No. 60-48384, etc.
As shown in the figure, an LED is mounted by wire bonding on a ceramic substrate 21 fixed to a heat sink 22.
An imaging optical system was sandwiched between the array 1 and the photoreceptor, and the LED array was configured to emit light in response to an image signal input to the optical printer head to form an image on the photoreceptor.

[Problems to be Solved by the Invention] However, in the conventional optical printer head, since the imaging element 20 is required, the optical path length to the photoconductor becomes long. The distance between the bodies must be adjusted, which is very difficult and delicate, making optical printer heads larger and more complex.
And prices could not be avoided. In particular, if a Selfoc Lens Array (SLA) [registered trademark], which has a deep depth of focus, is used as the imaging element, the amount of light will be insufficient, making it impossible to apply it to medium-high speed printing devices, and conversely, the numerical aperture will be large. When SLA is used, the depth of focus is shallow (which causes smearing and blurring of the print, which inevitably lowers the print quality, and if the interval between the imaging elements is not properly adjusted, the print quality will deteriorate further. It became a thing.

In order to solve the above problems, a proposal was made as disclosed in Japanese Patent Application Laid-Open No. 62-251970. However, in this case, it is difficult to practically reduce the thickness of the input electrode of the LED array and the thickness of the light-transmitting resin, and the possibility of realization is extremely low.

Therefore, the present invention aims to solve these problems.
The purpose is to provide an optical printer head with a simple structure that provides high print quality images and does not have an optical system such as an imaging element.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides an optical printer head that uses an LED array as a light emitting source and prints by exposing a photosensitive member to a metal plate having a large number of through holes. The light emitting surface of the KLKD array is fixedly connected, the wiring pattern formed on the insulating plate and the LED array are fixedly connected, and the metal plate is used as a common electrode of the LED array.

[Function] According to the configuration of the present invention, light emitted from the LED array is emitted from a large number of small through holes provided in a metal plate, and optically passes over the surface of the photosensitive drum disposed in close proximity to the metal plate. Expose without going through a system.

[Example] Therefore, details of the present invention will be explained below based on an example.

FIG. 1 is a perspective view showing a sectional view of a main part of an optical printer head according to a first embodiment of the present invention, and FIG. 2 is a sectional view taken along line A-A'. Reference numeral 1 in the figure is an LED array, which is fixed to a metal plate 2. The metal plate 2 has a large number of through holes 3.
The nine through holes 6 are arranged in one row or in two staggered rows at intervals corresponding to the desired printing dot density. In the present invention, examples of printing dot densities of 240DPI (Dots Per Mach) and 300DPI will be described as shown in FIG. However, the present invention is not limited to this,
It goes without saying that optical printer heads with different printing dot densities can be constructed using a similar method.

(Example 1) As shown in FIG. 6(α), the small through holes 3 are arranged linearly at intervals of 106 μm.The dimension a is 106106p and 150 μm.

C is 170prn, cl is 60pm, e is 85/jF7
It is L. The LED array 1 is fixed with a conductive adhesive to the back side of the metal plate 2 where the small through hole 5 is provided. The metal plate 3 is placed on the surface of the I, ED array 10.
A light emitting window 10 is provided corresponding to the small through hole 3 disposed in the . Prototype experiments were conducted using three different values for the diameters of the light emitting window 10 and the small through hole 3, and the results shown in the table below were obtained.

Note that ◎○Δ× in the table below is an evaluation that changes stepwise from good to poor. From the results below, in this example, the diameter of the small through hole 3 is 50 μm, and the diameter of the light emitting window 10 is 70 μm.
Good printing was obtained as m. However, combinations such as those marked with ○ in the table may be used.

The L]18D array 1 fixed to the metal plate 3 is diced from the back side to electrically separate each light emitting element, but at this time, the dicing grooves 8 must reach at least nine layers 7. Here, the dicing groove 8 is formed to reach the conductive adhesive layer 14. This makes it possible to prevent leakage of light between adjacent devices. In some cases, the dicing groove 8 may reach a part of the metal plate 2. The LED array 1 and metal plate 2 separated into light emitting elements in this way are placed and fixed on the circuit board 11.

In the circuit board 11, an insulating layer 12 having a good heat transfer coefficient is formed on a heat sink 4 made of metal, and a wiring pattern 5 and a resist 9 are formed on the insulating layer 12. The odd-numbered wiring patterns 5 and the even-numbered wiring patterns 5 are arranged in different directions, and are exposed to the outside as signal input electrodes 13 at the ends of the circuit board 11. In this embodiment, aluminum is used as the metal constituting the heat dissipation plate 4, which is an inexpensive material, has good workability, and can be made lightweight, but other metals such as aluminum alloys may also be used. Further, the insulating layer 12 is formed by applying a ceramic solution and then sintering it. Alternatively, a glass woven cloth impregnated with an epoxy resin may be attached, although the heat dissipation property will be slightly lowered. The n-shaped electrodes of the LED array 1 are fixed to the wiring pattern 5 with a conductive adhesive 15, and since this process is performed for all the LED arrays in the optical printer head at once, mounting using conventional wire bonding is not possible. It can be completed in a shorter time compared to Further, the metal plate 2 is curved into a convex shape and fixed on the resist 9 of the circuit board 11 with adhesive.
The structure is such that the array 1 is hermetically sealed. This protects it from contamination by toner powder and the like generated during the electrophotographic process.

Furthermore, the heat generated by the LED array when emitting light is generated by the light emitting part 9
This occurs in the layer 7, and according to the structure of the present invention, the nine layers 7 are closely fixed to the metal plate 2, which also serves as a heat dissipation member, at the shortest distance, so that the heat generated by the LED array can be efficiently dissipated, which is a unique feature not seen in the past. It has the effect of After the above configuration is completed, a drive signal from an external LED array drive circuit is wired and inputted to the signal input electrode 16, and the metal plate 2 is wired as a common electrode, thereby causing the LED array to emit light.

By arranging the optical printer head configured as described above in contact with or close to the photoreceptor, it is possible to configure an optical writing device that does not require an optical system.

(Example 2) FIG. 4 is a perspective view showing a cross section of the main part of the optical printer head according to this example, and the through holes 3 are spaced at intervals of 600 μm as shown in FIG. 5(b). 170μ in two rows
They are arranged in a staggered manner at intervals of m. On the back side of the metal plate 2 where the small through holes 3 are arranged, the LED arrays 1 are fixed with a conductive adhesive so as to form two rows as in the first embodiment. The difference from Embodiment 1 is L.
The dicing grooves 8 are formed to reach nine layers 7 before the ED array 1 is fixed to the metal plate 2.

Regarding the diameters of the light emitting window 10 and the small through hole 6 at this time, a trial production experiment was conducted in the same manner as in the first example, and the results shown in the table below were obtained.

In addition, ◎○Δ× in the above table is an evaluation that changes stepwise from good to poor. From the above results, in this example, the diameter of the through hole B is 50 μm, and the diameter of the light emitting window 10 is 70 μm.
Good printing was achieved in μm. However, combinations such as those marked with ○ in the table may also be used. L fixed to metal plate O
The ED array jIE is placed and fixed on the circuit board 11 all at once. The wiring patterns 5 on the circuit board 11 are arranged at the same intervals as the light emitting windows 10 of the LKD array 1.
The end portion of the electrode is opened to the outside as a signal input electrode 13.

(Embodiment 3) FIG. 5 is a perspective view showing a cross section of a main part of an optical printer head according to this embodiment. In the second embodiment, the LED ID array and the LED array drive element 16 are mounted in the space formed between the substantially convex metal plate 2 and the circuit board 110. Bumps are formed on the electrodes of the I and KD array drive elements 16, and are fixed to the wiring pattern with a conductive adhesive like the LED ID array. Conversely, a pedestal may be provided on the wiring pattern side for mounting. Since the LED array drive element 16 is mounted on the same substrate in this way, it is possible to drastically reduce the number of signal input electrodes 130 compared to the second embodiment, and the wiring to the signal input electrodes 15 can be significantly reduced. Work can be done easily.

[Effects of the Invention] According to the optical printer head of the present invention, it is possible to easily provide rad to an optical printer capable of high-quality printing without requiring an optical system. Furthermore, since the heat generating part of the LID array is fixed to the heat dissipating member at the shortest distance, efficient heat dissipation is possible, and since a special heat dissipation device is not required, the optical printer head can be miniaturized, which is a unique effect.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a cross section of a main part of an optical printer head according to the present invention, and FIG. 2 is a cross-sectional view taken along line AA'. FIGS. 6(α) and 6(b) are diagrams showing examples of arrangement of small through holes in the present invention. FIG. 4 is a perspective view showing a cross section of a main part of an optical printer head according to a second embodiment of the present invention. FIG. 5 is a perspective view showing a cross section of a main part of an optical printer head according to a fifth embodiment of the present invention. FIG. 6 is a perspective view showing a cross section of a main part of a conventional optical printer head. 1......LED ID array...Metal plate 3......Through small hole 4...Heat sink plate 10... ......Light emitting window 11......Circuit board 16......LED array drive element or more

Claims (1)

[Claims] In an optical printer head that uses a light emitting diode array (hereinafter referred to as an LED array) as a light source and prints by exposing a photoreceptor to light, the light emitting surface of the LED array is fixed to a metal plate having a large number of through holes. An optical printer head characterized in that the LED array is fixedly connected to a wiring pattern formed on an insulating plate, and the metal plate is used as a common electrode of the LED array.