JPS60227231A - Optical printer head - Google Patents

Abstract

PURPOSE:To increase exposure per unit area and luminance and to decrease the electric current to be conducted to a light emitting element by making the light emitted from the terminal end face of the P-N junction face of the light emitting element incident on the light incident face of a liquid crystal shutter facing the terminal end face in proximity thereto. CONSTITUTION:An LED array 28 which is a light source is brought into tight contact with a liquid crystal shutter array 15. LED chips 30 are lined up by as much as the length of the array 15 and are attached to an insulating substrate 31. An electrode 32 is provided on the outside surface in the P-layer region of each chip 30 and contacts with the bonding pad 31a of the substrate 31. An electrode 33 is provided on the outside surface of the N-region layer and is bonded by a wire 34 to the electrode 31. The light, when emitted from tne P-N junction face, advances between two sheets of the electrodes 32 and 33 and is emitted from the end face. The picture element position of the array 15 is matched with the end face so as to bring the polarizing plate into contact therewith. The exposure per unit area is thus increased and the luminance is increased with small electric power.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical printer head that can be used as an image light source for electrophotographic optical printers and the like.

[Prior art]

FIG. 3 shows a schematic configuration diagram of an optical printer to which electrophotography is applied. In the figure, the photoreceptor l rotates in the direction of the arrow.
is uniformly charged by a charger 2, and imagewise exposed by an optical printer head 3 that emits light according to an image signal to form an electrostatic latent image. The electrostatic latent image is developed with toner supplied from the developing device 5. The toner image is transferred onto a transfer paper P by a transfer charger 6 and fixed by a fixing device 7 to obtain a hard copy. On the other hand, the toner remaining on the photoreceptor 1 is scraped off by a cleaner 8, and the residual charge is removed by a charge eliminator 9 and a light source 10 in preparation for the next image formation.

FIG. 4 shows a conventionally known configuration of an optical printer head 3 used in such printers, which consists of a light source and a liquid crystal shutter array. light source 12
is an LED array in which light emitting diodes are arranged in a row (in the depth direction in the drawing). The structure of LED l 2 is such that the junction surface between the P region and the N region is aligned with the light emitting surface. Wire bonding is performed with a wire 14 between the electrode of the P region on the light emitting surface side and the power supply electrode 11. L.E.
The diffused light emitted from the D array 12 is focused only in one-dimensional direction by the cylindrical lens 13 and is incident on the liquid crystal shutter array 15. The light transmitted through the liquid crystal shutter array 15 is imaged on the surface of the photoreceptor 1 by a short-focus convergent lens array 16 arranged in a single row, and the above-mentioned image exposure is performed.

The liquid crystal shutter array 15 has pixels arranged in a line. The arrangement direction is the longitudinal direction of the cylindrical lens 13,
This is the same direction as the arrangement direction of the LED array 12 and short focus lens array 16. FIG. 5 shows a longitudinal cross-sectional view of the liquid crystal shutter array 15. As shown in FIG. Two transparent substrates 18.
19 are held facing each other at a constant distance by a sealing material 20 to form a liquid crystal cell, and the cell is filled with a liquid crystal substance. A common electrode 22 is provided on the transparent substrate 18, and a microelectrode 23 for each pixel is provided on the transparent substrate 19.・232-233... are provided, and an image signal voltage is applied between the electrode 22 and the electrodes 231, 23, 233, and the fist. Also, transparent substrate 1
A first polarizing plate 25 and a second polarizing plate 26 are disposed in close contact with the outer sides of the polarizing plates 8 and 19, respectively. Of the light incident on the liquid crystal shutter array 15, only one component of linearly polarized light is transmitted through the first polarizing plate 25. When the transmitted polarized light passes through the liquid crystal, it rotates in the parts of the pixel electrodes 231, 232, 233, etc. where no image signal voltage is applied, and does not rotate in the parts to which voltage is applied. The image signal light is transmitted through the second polarizing plate 26, and the image signal light is emitted from the liquid crystal shear array 15.

However, in such a printer head, only a very small amount of the light from the T and ED array 12, which is the light source, is effectively used. This is to prevent it from happening. However, this cause cannot be eliminated due to the essential properties of the liquid crystal shutter array.

Another reason is that the cylindrical lens 13 focuses light in one dimension, but not in the radial direction (longitudinal direction). That is, LED
The light from the array 12 remains spread out in the longitudinal direction, and there are many light components that cannot be captured by the aperture of the short focus lens array 16. Therefore, the value of the condenser lens 13 is halved. There is. For these reasons, the amount of image light tends to be insufficient, so the current applied to the LED l2 is increased to increase the amount of light. As a result, the LED
There is a problem in that the lifespan of the printer head is shortened and the printer head is more likely to break down.

In addition, since the width of the pixel row of the liquid crystal shutter array 15 is very small, the light from the LED 12 is transmitted to the cylindrical lens 1.
3, it is difficult to arrange each part so that the light can be focused exactly on the center white. Therefore, there is a problem in that the light from the LED array 12 hits the liquid crystal shutter array 15 at an angle, resulting in non-uniformity in the amount of light for each pixel. In addition, in this way, the light from the LED array 12 is transferred to the cylindrical lens 13.
If the image is to be projected using the printer head, there is an inconvenience that the printer head becomes large due to the installation space and optical path required.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to solve these problems and provide an optical printer head that is less likely to fail, can perform uniform image exposure, and is compact.

[Structure of the invention]

The present invention achieves this object by controlling the light emitted from the light emitting element and passing through the liquid crystal shutter by applying an image signal voltage to the liquid crystal shutter, and controlling the light emitted from the light emitting element in an optical printer head to obtain image light. The light emitted from the terminal surface of the PN junction surface of
The optical precipitator head is characterized in that the light is caused to enter a light incident surface of the liquid crystal shutter that closely faces the termination surface.

〔Example〕

FIG. 1 shows an embodiment of an optical printer head to which the present invention is applied. As shown in the figure, the LED which is the light source
Array 28 is in close contact with liquid crystal shutter array 15.

As shown in a perspective view in FIG. 2, the structure of the LED array 28 is such that LED chips 30 are arranged along the length of a liquid crystal shutter array 35 and attached to an insulating substrate 31. LED
An electrode 32 is provided on the outer surface of the P region layer of the chip 30 and contacts the bonding pad electrode 31a of the substrate 31, and an electrode 33 is provided on the outer surface of the N region layer and contacts the bonding pad electrode 31a. It is wire bonded with wire 34. The PN junction surface is in the vertical direction as shown, and the light exit surface is the end surface of the PN junction surface. ! When light emission occurs at the PN junction surface, it is confined between the two electrodes 32 and 33, and some light components travel directly while some light components travel through the gap while being totally reflected, and are emitted from the end face. The width of the end face (output n]) is the sum of the thicknesses of the P region layer and the N region layer, and is expressed by the formula 11
It becomes 001L. The first polarizing plate 37 is brought into contact with the end face by aligning the pixel positions of the liquid crystal shutter array 15, and the LED array 28 and the liquid crystal shutter array 15 are arranged close to each other.

[Effect]

In the conventional optical printer head, since there is a current supply means such as wire bonding on the light emitting surface side of the light source LED l 2, it was not possible to bring the liquid crystal shutter array 15 close to each other, but in the optical printer head of the present invention, the light source LED
28 and the liquid crystal shutter array 15 are integrated, making it extremely compact. LCD shutter area, I15
Since it becomes easier to align the pixel row with the light emitting position of LE028, the light emitted from the liquid crystal shutter array 15 becomes uniform over the entire length of the pixel row. In addition, although conventional light collection using cylindrical lenses is eliminated, light collection is originally only in one dimension and is inefficient, and as the distance from the light source becomes shorter and the amount of light increases, the overall amount of output light increases. . In addition, the luminance per unit area can be increased by making the light emitting width of the LED 28 narrow and constant, and by increasing the area of the PN junction surface.

Therefore, even if the current applied to the LED 28 is small, the amount of image exposure will be sufficient, and failures will be reduced.

[Other Examples]

An insulating reflective plate may be provided on the side of the LED chip 3o opposite to the liquid crystal shutter array 15 (upper side in the figure). If this is done, the light entering the liquid crystal shutter array 15 from the LED chip 30 will be reduced. The amount becomes even larger.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an optical printer head to which the present invention is applied;
Fig. 2 is a perspective view of the main parts, Fig. 3 is a schematic diagram of a printer equipped with an optical printer head, Fig. 4 is a sectional view of a conventional optical printer head, and Fig. 5 is a sectional view of a liquid crystal shunter array. . 3 is an optical printer head, 12 and 28 are light emitting diode arrays, 15 is a liquid crystal shutter array, 16 is a short focus lens array, 30 is a light emitting diode chip, and 31 is a wiring board. Patent applicant Canon Co., Ltd.

Claims (1)

[Claims] 1. In an optical printer head that controls the light emitted from a light emitting element and passes through a liquid crystal shutter by applying an image signal voltage to the liquid crystal shutter to obtain image light, the terminal surface of the PN junction surface of the light emitting element is used. An optical printer head characterized in that light emitted from the liquid crystal shutter is incident on a light incident surface of the liquid crystal shutter that closely faces the terminal end surface.