JP2521106B2 - Optical writing head - Google Patents

Description

The present invention relates to an optical writing head used for an LED printer or the like using an electrophotographic method.

[Conventional technology]

FIG. 3 shows a schematic explanatory view of an LED printer using an LED array head as an example of the optical writing head.

In the figure, reference numeral 1 is a photosensitive drum whose surface is made of a photoconductive material, and rotates in the direction of the arrow in the figure. This drum 1
Are uniformly charged by the charger 2, and then the LED array head 3 receives an exposure corresponding to the recorded image information, whereby an electrostatic latent image is formed. This latent image is developed by the developing device 4 to obtain a toner image, and this toner image is transferred to the transfer paper 6 under the action of the transfer device 5. Then, the transfer paper 6 onto which the toner image is transferred is sent to the fixing device 7, where the toner image is fixed on the paper 6. On the other hand, after the transfer, the photosensitive drum 1 is cleaned by the cleaning device 8 and reused.

The LED array head 3 has a large number of LEDs as described later.
(Light emitting diode) LED with chips arranged in the print digit direction
An element array and a self-focusing rod lens array that focuses the light emitted by each LED element of the element array and exposes it onto the photosensitive drum 1 are provided.

As shown in FIG. 4, the conventional LED array head 3 used in the above LED printer has a ceramic substrate 21.
LED chip 22 is die-bonded on top, wire bonding is performed corresponding to each light emitting part to energize each LED light emitting part, bonding wire connected to this LED chip 22 and ceramic board mounting this LED chip 22 twenty one
A cover crow 26 for protecting the upper conductor pattern is attached to a radiator plate 23 such as aluminum, and the mounting member 25 of the self-focusing type rod lens array 24 is supported on the radiator plate,
It constituted the LED array head.

[Problems to be solved by the invention]

For the LED array head as described above, when mounting the LED chip on the ceramic board, the positioning accuracy such as linearity is required to be about ± 10 μm, and the width of the chip is 0.7.
~ 1 mm, width of pad for die bonding is 1.2 ~ 1.5 m
Since it is quite large (about m), the positioning requires an optical method using a TV camera, etc., which not only reduces the efficiency of die bonding of the LED chip, but also requires the use of expensive mounting equipment. Atsuta

Also, wire bonding needs to be performed once for each LED light-emitting part (normally 64 LED chips are formed for each LED chip). As an example, a commonly used integration density of 300D
For LED array heads for PI (approx. 12 dots / mm) and A4-letter size, 2560 wire bonds are required, and even if a high-speed wire bonder is used, it will take about 40 minutes to 1 hour. If even one of them has a mistake in bonding, the LED array head will be defective as a whole, so careful attention is required, resulting in poor production efficiency and cost increase.

Furthermore, both the alignment accuracy of the LED chips of the LED array head and the variation in the linearity in the height direction of the light emitting part require high accuracy of ± 100 μm in the width direction (216 mm for A4 size). The sled and bend of itself are limited. Therefore, it is necessary to use a highly accurate ceramic substrate and to select all the substrates, which makes the substrate expensive.

Further, since the self-focusing type rod lens array is held on the heat dissipation plate to which the ceramic substrate is attached, there is a drawback that errors of these dimensions are accumulated and required accuracy cannot be obtained.
Currently, the positioning accuracy of the self-focusing rod lens array is ± 0.1 mm over the entire length, and it is essential to check the optical mounting position accuracy, and it is necessary to install a mechanism in the LED array head that enables highly accurate positioning. Yes,
It also brought up costs in terms of assembly man-hours, manufacturing equipment, number of parts, and the like.

The present invention has been made in view of such problems, and an object thereof is to provide a low cost optical writing head with a simple structure.

[Means for Solving the Problems] The present invention uses a substrate having a fiber bundle at least a part of which is composed of a plurality of optical fibers, and a flip chip type so that the light emitting portion side of the substrate faces the substrate surface. With the mounted light emitting means, one end of the fiber bundle faces the light emitting portion of the light emitting means, and the other end is formed into a curved surface, and the end formed in the curved surface becomes an exposed object. It is characterized in that it is in sliding contact with the surface of the photosensitive belt.

[Action]

Since the LED chip is mounted on the board surface in the flip chip format, wire bonding is unnecessary. Furthermore, since a plurality of optical fiber bundles are directly embedded in the substrate, the number of parts can be reduced and the mechanism can be simplified.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to FIG. 1 and FIG.

In FIG. 1, reference numeral 11 denotes a transparent substrate such as glass, on the surface of which a desired fine conductor pattern is formed by a thin film process.
12 are formed. The LED chip 13 is connected to the conductive pattern 12 by a solder bump 12b so that its light emitting portion 13a faces the substrate 11. Further, the back electrode 13b of the LED chip 13 is electrically connected to the ground pattern 12a of the substrate 11 by the lead wire 14. Further, the light emitting portion 13 of the LED chip 13
a through a transparent synthetic resin 15 to a diameter of 10 to 25, which will be described later.
One end 16a of a fiber bundle 16 having a structure in which a large number of μm optical fibers 17 are gathered is close to each other. The fiber bundle 16 is held in a state of being embedded in the substrate 11. As shown in FIG. 2, the above-mentioned optical fiber 17 includes a core 17a made of glass having a high refractive index and a cladding 17b made of glass having a low refractive index formed on the outer periphery of the core 17a.
And an absorber 17c made of carbon or the like formed on the outer periphery of the cladding 17b, thereby forming a three-layer structure.

For an LED array head constructed in this way,
As shown in FIG. 1, the light emitted from the light emitting portion 13a of the LED chip 13 enters from one end portion 16a of the fiber bundle 16 through the transparent synthetic resin 15 and is transmitted in the fiber bundle 16 with high efficiency. The surface of the object to be exposed 18 such as the photosensitive belt which is in contact with the other end 16b formed on the curved surface is irradiated.

〔The invention's effect〕

In the present invention, the following effects are provided by configuring the optical writing head as described above.

By mounting the light emitting means in a flip-chip form on the substrate using a transparent substrate, a wire bonding step has been conventionally required, but this step is unnecessary and the number of steps can be reduced.

In particular, when a glass substrate is used as the substrate, it is easy to form a fine pattern by a thin film process because of its high surface smoothness, and since a highly accurate substrate without warpage can be easily obtained, the positioning accuracy of the light emitting means can be improved. Is easy to obtain.

Since the optical fiber does not have a focus unlike the self-focusing type rod lens array, the distance between the light emitting portion of the light emitting means and the object to be exposed can be reduced, and the device can be downsized.

Most of the light emitted from the light emitting portion of the light emitting means enters the fiber bundle and is efficiently irradiated to the object to be exposed. Therefore, it is possible to reduce the light emitting energy supplied to the light emitting means, so that the life of the light emitting means is reduced. Becomes longer.

Since the end of the fiber bundle is formed into a curved surface,
There is no risk of damaging the exposed object by making a smooth contact with it.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a structural sectional view of an optical writing head showing an embodiment of the present invention, FIG. 2 is a sectional view of the same optical fiber, and FIG. 3 is a configuration of an ordinary LED printer. FIG. 4 is a schematic configuration diagram for explaining, and FIG. 4 is a structural sectional view of a conventional LED array head. 11 …… Transparent substrate 13 …… LED chip 13a …… Light emitting part 16 …… Fiber bundle 17 …… Optical fiber

Claims (1)

(57) [Claims] 1. A substrate having a fiber bundle at least a part of which comprises a plurality of optical fibers, and a light emitting means mounted on the substrate in a flip chip form so that a light emitting portion side thereof faces a substrate surface, One end of the fiber bundle faces the light emitting part of the light emitting means, the other end is formed into a curved surface, and the end formed in the curved surface is in sliding contact with the surface of the photosensitive belt that is the exposed object. An optical writing head characterized in that