JPH0777809B2 - Light emitting diode array - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting diode printer using the light emitting diode array as an optical recording head for image formation, and more particularly to a high definition light emitting diode array.

[Conventional technology]

A light emitting diode printer generally has the configuration shown in FIG. The photosensitive drum 5 rotates in the direction of arrow Y. At this time, the surface of the photosensitive drum is uniformly charged by the charger 6.
The conventional light emitting diode array head is 7 and is composed of a light emitting diode array portion having a head substrate structure in which a driver of 8 is mounted and an imaging lens array portion of 9. The light emitting diodes have thousands of light emitting elements for one row in the main scanning direction and are arranged in one row in parallel with the rotation axis of the photosensitive drum to form a so-called light emitting diode array. Each light emitting diode is connected to a driver so that it can blink independently in response to an image signal. This blinking is imaged on the photosensitive drum by the imaging lens array, and the electric charge in the illuminated image portion disappears. Main scanning for each line is sequentially performed in synchronization with the rotation of the photosensitive drum to form a charge image for one screen. Then, the charge image is formed into a toner image by the developing machine 10. The toner development includes normal development in which toner is attached to the portion where the charged electric charge remains and reversal development in which the toner is attached to the portion where the charged electric charge disappears, which are appropriately used. The toner image formed by the development is transferred to the sheet 12 by the next transfer device 11 and fixed by the fixing device 13. Also, a small amount of untransferred toner is a cleaner.
It is removed from the photosensitive drum at 14, and the surface charge of the photosensitive drum is uniformly removed by the eraser 15.

The light emitting diode array has a conventional dot array structure as shown in FIG. This figure is a surface view of the array. A light emitting diode array is usually manufactured as a chip 3 having a light emitting dot 1 formed by p and n layers, a dot separation I and a dot electrode 2 on a wafer of 2 to 5 inches by making full use of epitaxial and diffusion techniques. . The chips are laid out in a row of the required recording width and assembled into a light emitting diode array head. For example, in the case of the cathode common chip, the dot separation is shown in the center cross section of the array in FIG.
It becomes like (b). FIG. 3A shows a method in which an n layer is formed on the entire surface of a wafer B, and then a p layer which becomes a light emitting dot is formed by selective diffusion separately from an adjacent dot.
(B) is separation by etching that penetrates the p layer.
In any case, the non-light emitting part I of about 20 μm between dots
Have. Dot electrodes for energizing each light emitting dot are alternately drawn out in a direction perpendicular to the array so as to facilitate connection with a driver by wire bonding. Then, the light emitting dot is electrically connected at a part 4 on the pulling side.

Incidentally, regarding this kind of technology, for example, JP-A-58-2030
No. 71 publication.

[Problems to be solved by the invention]

In the above conventional light emitting diode array, one side of the light emitting dot is inevitably reduced by about 20 μm due to dot separation.
When forming a high-definition recording array of 20 dots / mm or more in which the dot pitch is 50 μm or less, the proportion of the non-light emitting portion to the dot pitch becomes large. Therefore, when forming an image with a plurality of dots, in the developing process using fine toner, so-called fog occurs in which the black stripes are generated corresponding to the non-light-emitting portion of the dot separation in the regular development, and the black solid is generated in the reverse development. White streaks enter the inside, causing a decrease in recording density. As described above, the conventional array has a problem that image quality is deteriorated.

Further, since a large amount of current is supplied to the extraction side connected to the dot electrode in the light emitting dot, the light output shows a distribution which is offset with respect to the sub-scanning direction perpendicular to the array. In such a light output distribution, the light output is lowered, so that the drive current per dot is increased in order to obtain the required amount of light emission. That is, the problem that the driving power becomes large occurs in the conventional array.

An object of the present invention is to eliminate a deterioration in image quality caused by a non-light emitting portion between dots of a conventional light emitting diode array and an increase in drive current due to a connection form with a dot electrode, and to realize a high image quality and low power consumption with a simple structure. An object is to provide a light emitting diode array.

[Means for solving problems]

The above purpose is to arrange the light emitting dots of the light emitting diode array in two rows in a staggered pattern, and from the light emitting dot periphery where each light emitting dot is perpendicular to the array direction, form a narrow protruding shape toward the center of the light emitting dot. This is achieved by providing a light emitting diode array structure in which dot electrodes having a shape extending in the array arrangement direction are provided.

[Action]

If the zigzag light emitting dots are used, the dot pitch will be twice as large as the one line arrangement, so there will be a sufficient dot separation band, and the light emitting dot size can be assured to match the recording dot density. Therefore, the optical image on the photosensitive drum can be made clear.

Further, the dot electrode is driven so as to have a shape extending from the side of the dot serving as the energization path to the center of the dot. As a result, the distribution of the light output in the dot is improved and the luminous efficiency is increased, so that the driving current is small.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a light emitting diode array chip according to an embodiment of the present invention. In the figure, 1-1 is an odd-numbered light emitting dot, and 1-2 is an even-numbered light emitting dot. Reference numeral 2 denotes a dot electrode, which is formed by vapor deposition of aluminum or the like and does not transmit light. Reference numeral 3 represents a light emitting diode array chip. The light emitting dots are separately formed by a known selective diffusion or etching technique, and have a rectangular shape having sides of x _H in the array direction and y _V in the direction perpendicular thereto. Then, the dot electrode has a shape 2-C extending in the array direction at the center of the dot, using the side y _{V of the} light emitting dot as an energizing path. The portion 4 of 2-C is electrically connected to the light emitting dot.

The side length x _H of the light emitting dot is equal to the size determined from the recording dot density. The other side length y _V of the light emitting dot is effective in consideration of the fact that the light image irradiated on the rotating photosensitive drum spreads in the rotating direction, that is, the dot y direction, compared to the size of the light source. Choose a value such that the light image above is almost square. The interval between the odd-numbered dot line and the even-numbered dot line is an integral multiple of the recording dot pitch. By having a data buffer memory corresponding to this interval, the irradiation timing of the odd-numbered dots and the even-numbered dots to the photoconductor is adjusted so that the dot optical image on the photoconductor drum has a regular size. You can arrange them in a straight line. As a result, the white streaks in the black image and the fog in the white image, which occur in the conventional array, are eliminated, and the image quality is improved.

Since electricity is applied to the light emitting dots at the center of the dots, the current distribution characteristic in the dots is improved, the light emission distribution becomes more uniform, and the light output per dot can be increased. This brings about an effect of reducing power consumption.

There is an opaque electrode at the center of the dot, but since it extends in the direction perpendicular to the direction of rotation of the photosensitive drum and its width is not large, the shadow generated in the image formation on the surface of the photosensitive drum is The dot light image on the photosensitive drum is not interrupted because it is canceled by the irradiation from the light emitting surface accompanying the rotation. Therefore, there is no inconvenience in terms of image quality.

〔The invention's effect〕

As described above in detail, according to the present invention, in the high-definition light emitting diode array, the light emitting dot can be formed in the net dot size, and at the same time, the current can be made more uniform in the dot structure. As a result, it is possible to obtain an effect that a high-quality recorded image without a decrease in density or fog is realized together with a reduction in power consumption.

[Brief description of drawings]

FIG. 1 is a front view of a light emitting diode array according to an embodiment of the present invention, FIG. 2 is an explanatory view of a light emitting diode printer, and FIG.
FIG. 4 is a front view of a conventional light emitting diode array, and FIG. 4 is a sectional view of the light emitting diode array for explaining dot separation. 1-1, 1-2 ... Emitting dots, 2,2-C ... Dot electrodes,
3 ... Light emitting diode array chip, 4 ... Connection part.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location H04N 1/036 A

Claims (1)

[Claims] 1. In a light emitting diode array in which a plurality of minute light emitting diodes corresponding to recording dots are arranged and the light emitting diodes are independently blinked according to image data, the light emitting dots are arranged in two rows in a staggered pattern. , Each light emitting dot has a dot electrode in the shape of a protrusion that has a narrow width from the periphery of the light emitting dot forming a right angle with the array direction of the array, and extends in the array direction of the array toward the center of the light emitting dot. Light emitting diode array.