JPH0740595A - Optical printing head - Google Patents

Abstract

PURPOSE:To provide a serial optical printing head which can carry out the high speed printing and is of superior image formation performance. CONSTITUTION:LED array mounting faces 6, 8 and 10 which are approximate to a concentric circle of a sensitive drum 2 are formed on a housing 4, and one LED array 14 is mounted on every one mounting face. A single lens 20 is provided on every array 14 and so disposed as to form three strings on the concentric circle of the drum 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical print head using an LED array or an EL array, and more particularly to a head for serial exposure in the main scanning direction.

[0002]

2. Description of the Related Art It is known that an LED array or an EL array is used for exposing a photosensitive member, and serial exposure is performed while moving the array along a guide in the main scanning direction. The serial printer is characterized by its small size and low cost, and the head is also required to be small and low cost. However, in the case of an optical printer which is somewhat expensive, even a serial printer requires high-speed printing performance for the head.

From such a viewpoint, the inventor tried to improve the printing speed by arranging a large number of light emitter arrays (for example, LED arrays) along the sub-scanning direction and increasing the number of dots exposed at the same time. In this case, what is important is to arrange the light emitter array and the lens according to the curvature of the photoconductor so that the light emitter array and the lens are arranged at appropriate positions with respect to the photoconductor having the curvature. . There is also a problem with the type of lens, and since the self-focusing lens array that is normally used in imaging devices is a bundle of rod-shaped lenses,
It cannot be bent according to the surface shape of the photoconductor and cannot be used.

[0004]

An object of the present invention is to improve the printing speed by arranging a plurality of light emitter arrays in the sub-scanning direction, and 2) a light emitter array and a lens used for imaging. It is to put it in place from the surface of the photoconductor. In addition to 1) and 2), the object of the invention of claim 2 is to 3) further bring out the characteristics of a small-sized serial head.
In addition to 1) to 3), 4) to prevent density unevenness due to spontaneous attenuation of the exposure potential while the head is moving in the main scanning direction.

[0005]

According to the present invention, in an optical print head for exposing a photosensitive member having a curvature in the sub-scanning direction, a plurality of light-emitting members are provided on a line at a constant distance from the photosensitive member in the sub-scanning direction. An array is arranged, and a monocular lens is arranged for each light emitter array on a line that internally divides each light emitter array and the surface of the photoconductor at a constant ratio (claim 1). Preferably, the optical print head is disposed inside the photoconductor and exposed from the back side (claim 2). More preferably, the developing device is arranged so as to face the exposed portion of the photoconductor by the optical print head, and the exposure and the development are performed at substantially the same position (claim 3).

[0006]

According to the present invention, a plurality of light emitter arrays are arranged on a line at a constant distance from the surface of the photoconductor. The light emitter array may be arranged outside or inside the photoreceptor. Next, in order to internally divide the distance between the photoconductor surface and the light emitter array at a predetermined ratio, in other words, for each light emitter array, on a line where the distance between the photoconductor surface and the photoconductor surface is more constant than that of the light emitter array, Place a monocular lens on. As the photoconductor, a film-shaped organic photoconductor film or the like is used in addition to a transparent glass cylindrical substrate provided with a photoconductor film such as a-Si. These photoconductors have a curvature, and for example, in the case of a cylindrical photoconductor, the light emitter array and the monocular lens are arranged on a concentric circle with the photoconductor. As a general rule, the lines for arranging the light emitter array and the monocular lens are curved lines, and it is difficult to obtain imaging performance with a single lens for a plurality of light emitter arrays on the curved line. To use.

The luminous body array and the monocular lens are preferably housed inside the photoconductor to reduce the size of the apparatus. When serially exposing while moving the head along the main scanning direction,
The exposure timing is shifted by the scanning time at both ends of one line in the main scanning direction, and the natural attenuation of the exposure potential and the charging potential cannot be ignored. Therefore, preferably, the print head is disposed inside the photoconductor and the developing device is disposed outside, and the print head and the developing device are opposed to each other through the exposure portion, and the exposure and the development are performed substantially at the same time. The characteristic of such development is that the charging / exposure / development is performed substantially at the same time so that the exposure can be performed in a wide range within the range of the toner pool between the charger and the photoconductor, and the scanning with the serial head is slow. Therefore, the problem that the exposure timing changes along the main scanning direction can be solved.

[0008]

EXAMPLE A first example is shown in FIGS. In FIG. 1, 2 is a cylindrical photosensitive drum, 3 is an optical print head, 4 is its housing, and 6, 8 and 10 are array mounting surfaces, which are arranged concentrically with the photosensitive drum 2. It is a surface in which concentric circles having a diameter larger than 2 are arranged so as to be approximated by three chords. Reference numeral 12 is a substrate, and 14 is an LED array, which may be an EL array or the like.
Although three 4 are used, a plurality may be used. For the LED array 14, a large number of light emitting elements arranged in one or a plurality of rows along the sub-scanning direction of the photosensitive drum 2 is used, and 16 is a lens mounting wall, which extends toward the center of the photosensitive drum 2. There is. That is, when the lens mounting wall 16 is extended, it intersects at the center of the drum 2. Reference numeral 18 is a lens plate, which is fixed to the mounting wall 16, and 20 is a monocular lens fixed to the plate 18. The mounting wall 16 is provided so as to separate the LED arrays 14 one by one, and a monocular lens 20 is provided for each array 14.
The monocular lens 20 is a curved lens or a rod lens. 22 is a carriage and 24 is a guide hole.

As shown in FIG. 2, the print head 3 is moved in the main scanning direction of the photosensitive drum 2 through the guide 26 through the guide hole 24, and serially in the main scanning direction and three in the sub scanning direction. The light emission of the LED arrays 14, 14 and 14 exposes in parallel. When the LED array 14 is provided with 64 dots × 1 row of light emitters, 192 dots are simultaneously exposed in the sub-scanning direction and one dot is exposed in the main scanning direction. Reference numeral 28 is a drive IC for the LED array 14.

FIG. 3 shows a usage state of the print head 3. 30 is a developing device, 32 is a developing roller, 34 is a cleaner, 36 is a charger, and 38 is a transfer charger.

The characteristics of the optical print head 3 will be described. The optical print head 3 is moved in the main scanning direction of the drum 2 using the guide 26, and serial exposure is performed. The exposure speed is 1 dot at a time in the main scanning direction and 6 in the sub scanning direction.
High-speed exposure is possible because a plurality of LED arrays 14 are used in 4 × 3 192 dot parallel. Array mounting surface 6,
Since 8 and 10 are provided so as to approximate the concentric circles of the photosensitive drum 2, the LED arrays 14, 14 and 14 are arranged at the same distance from the surface of the photosensitive drum 2. Monocular lens 2
By forming an enlarged image on the photosensitive drum 2 at 0,
The LED array 14 is downsized and the cost is reduced. Also L
When the ED array 14 is miniaturized, even if the surface of the array 14 is flat, the deviation from the circular arc is small, and the distance to the photosensitive drum 2 can be made constant.

It is difficult to image the light of the LED arrays 14, 14, 14 arranged on three strings on the concentric circles of the drum 2 with one lens, and the imaging performance is deteriorated due to the variation in the distance from the lens. Occurs. Therefore, a monocular lens 20 is arranged for each LED array 14, and an image is formed by using a different lens for each array 14 and combined on the drum 2. The monocular lens 20 is mounted on the lens plate 18, and the three lenses 2
0, 20, 20 are arranged on the concentric circles of the drum 2 and are positioned so as to form three equal chords. Lens 20, 2
0 and 20 internally divide the space between the LED arrays 14, 14 and 14 and the photosensitive film on the surface of the drum 2 at a constant ratio. As a result, an optical print head 3 capable of high-speed printing and having high exposure accuracy can be obtained.

[0013]

[Embodiment 2] FIGS. 4 and 5 show an embodiment of a light back exposure system. In FIG. 4, reference numeral 40 denotes an optical print head, which is housed inside the photosensitive drum 2, 42 is a developing device, 44 is a developing roller, 46 is a sleeve, 48 is an electrode roller of 8 poles, 50 is a transfer roller, 52 is a sheet of paper. The print head 40 and the developing device 42 are arranged so as to face each other via the drum 2, a bias is applied to the transparent electrode of the drum 2 on the sleeve 46, and contact is made with conductive toner in the toner reservoir 54. The photoconductor film of the drum 2 is charged to near the bias potential. When exposed by the optical print head 40, the potential of the photoconductor film decreases to near the potential of the transparent electrode,
The charged toner adheres to the exposed portion and is transferred to the paper 52 by the voltage applied to the transfer roller 50.

FIG. 5 shows the structure of the optical print head 40. In the figure, 56 is a new housing, and 58 and 6
Reference numerals 0 and 62 are new array mounting surfaces, and a concentric circle having a diameter smaller than that of the drum 2 is approximated by three chords, and 64 is a new lens mounting wall, which is arranged in the radial direction of the drum 2. In other respects, the configuration is similar to that of the print head 3 of FIG. 1, and the three LED arrays 14, 14, 14 are arranged on the concentric circle of the drum 2 as three strings having a small diameter, and the three monocular lenses 20 are arranged. , 20, 20 are arranged on the concentric circles of the drum 2 as three strings of intermediate diameter. LED array 14, 14, 1
4 and the photosensitive film on the surface of the photosensitive drum 2 are constant, and the distance between the lenses 20, 20, 20 and the photosensitive film and the LED array 14 is also constant. Further, in order to reduce the size of the LED array 14 and prevent the deterioration of the image forming performance due to the difference in the shape of the arc and the chord, a magnified image is formed on the drum 2.

One dot in the main scanning direction, for example, 30 μ
Second exposure, if there are 2560 dots in the main scanning direction,
One scan requires 76.8 msec, and during this period, the exposure potential and the charging potential may change due to spontaneous decay. However, as shown in FIG. 4, when the developing device 42 is opposed to the print head 40, the exposure and the development are performed at the same time. If the photosensitive film is exposed by being contacted with the toner and then exposed, the toner adheres only by the amount of the charge injected or released by the exposure and does not adhere further, and the toner once adhered returns to the toner pool 54. Absent. Therefore, it is possible to prevent the uneven density due to the difference in the exposure timing along the main scanning direction. Further, if the print head 40 is housed in the drum 2, the feature of the small-sized serial printer can be further utilized.

[0016]

According to the first aspect of the present invention, 1) a plurality of light emitter arrays are arranged in the sub-scanning direction to improve the printing speed, and 2) these light emitter arrays and the lens used for image formation are provided. Place at a specified distance from the surface of the photoconductor. Therefore, an optical print head having a high printing speed and high exposure accuracy can be obtained. According to the second aspect of the invention, in addition to 1) and 2), 3) the print head is housed inside the photoconductor to further bring out the feature of small size. According to the invention of claim 3, in addition to 1) to 3), 4) a developing device is arranged so as to face the exposed portion, and the exposure and the development are performed substantially at the same time to eliminate the influence of the natural decay of the exposure potential, thereby eliminating the uneven density. Prevent.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of an optical print head according to an embodiment.

FIG. 2 is a side view of the optical print head of the embodiment with the monocular lens removed.

FIG. 3 is a diagram showing a usage state of the optical print head of the embodiment.

FIG. 4 is a sectional view showing a usage state of an optical print head according to a second embodiment.

FIG. 5 is a cross-sectional view of an essential part of an optical print head according to a second embodiment.

[Explanation of symbols]

 2 Photosensitive drum 3 Optical print head 4,56 Housing 6,8,10 Array mounting surface 12 Substrate 14 LED array 16,64 Lens mounting wall 18 Lens plate 20 Monocular lens 22 Carriage 24 Guide hole 26 Guide 28 Drive IC 40 Optical printing Head 42 Developing device 44 Developing roller 46 Sleeve 48 Electrode roller 50 Transfer roller 52 Paper 54 Toner reservoir 58, 60, 62 Array mounting surface

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H01L 33/00 N 7376-4M

Claims (3)

[Claims] 1. An optical print head for exposing a photosensitive member having a curvature in a sub-scanning direction, wherein a plurality of light-emitting array units are arranged on a line at a constant distance from the photosensitive member in the sub-scanning direction. An optical print head characterized in that a monocular lens is arranged for each of the light emitter arrays on a line that internally divides each light emitter array and the surface of the photoconductor at a constant ratio. 2. The optical print head according to claim 1, wherein the optical print head is arranged inside the photoconductor so that the back surface of the photoconductor is exposed. 3. A developing device is arranged so as to face an exposed portion of the photoconductor by an optical print head.
The optical printhead of claim 2.