JPS60247663A - electrophotographic equipment - Google Patents

Abstract

PURPOSE:To prevent waste of a toner, lowering of contrast and image dropout on the border of the copied image by lighting a light source array composed of light emitting diodes and self-converging type lenses short in focal length and small in diameter in accordance with the width of the image to be formed on a photosensitive body to expose the lateral region of said body on which the image is not formed. CONSTITUTION:A light emitting diode (LED) array 20 arranged in the lateral direction of the photosensitive body 1 is lighted in accordance with the nonimage region width, and self-converging type lenses array 21 short in focal length and small in diameter are arranged likewise in the lateral direction are allowed to expose the nonimage region width in a sharp cutting manner. Only the fraction of the LED array 20 corresponding to the nonimage region width S is allowed to emit light to expose the photosensitive body 1 through the lenses 21, thus preventing the toner from attaching to the nonimage area.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention is an electrophotographic device such as a copying machine, in which excess developer adheres to an area other than the area where an image is formed (non-image area) on a photoreceptor. It is related to exposure that prevents

[Conventional technology]

In a copying machine which is an electrophotographic apparatus shown in FIG. 1, a photoreceptor 1 forms an image of a document 0 while rotating in the direction of the arrow, and transfers the image onto copy paper P to obtain a copy. In the figure, 3 is a slit, 4, 5, 6118, 9, and 10 are mirrors, and 7 is an imaging lens, which constitutes a scanning optical system. 12 is a primary charger, 13
14 is a developing device, 14 is a transfer charger, and 15 is a cleaner. Since each of these devices is well known, a detailed explanation thereof will be omitted. Since the non-image area of the photoreceptor l is not exposed to the image light from the scanning optical system, it is developed in the same way as the black part of the image, which is transferred and creates an unsightly black border around the edge of the copy paper. I end up.

Furthermore, developer (toner) is wasted.

In order to eliminate such adverse effects, conventional methods have been to expose non-image areas. This exposure is performed using different light sources for both the non-image area in the rotational direction of the photoreceptor l and the non-image area in the width direction (depth direction in the drawing) of the photoreceptor. Exposure to the former area is called blank exposure, and after the image exposure is completed, the photoreceptor can be uniformly exposed over the entire white area using a rod-shaped lamp 17 such as a fluorescent lamp, so the latter is relatively less problematic. Exposure to light is called sharp-cut exposure, and there are various technical problems because the amount of exposure must be changed depending on the size of the copy.

Conventionally, a large number of incandescent light sources whose exposure areas are regulated by light-shielding plates or light-emitting diodes with lens-shaped tips are used to illuminate the non-image area and expose the area. There is.

[Problem that the invention seeks to solve]

However, this method has the disadvantage that light also wraps around to the image area side, resulting in poor sharp cutting performance.

As a result, the image contrast at the periphery of the copy paper decreases, or in extreme cases, the image becomes white. If you try to improve sharp cutting by narrowing the aperture of the light shielding plate, there is a drawback that the amount of exposure will be insufficient and the black frame will not be completely erased.

Furthermore, recent copying machines have advanced variable magnification functions, and continuous variable magnification is becoming mainstream. At this time, it is necessary to continuously change the sharp cut exposure in response to the continuously changing image area width.

[Structure of the invention]

The configuration of the present invention that solves the above problems is such that, in an electrophotographic apparatus as shown in FIG. The light is turned on in accordance with the width direction, and the non-image area is subjected to sharp cut exposure using the short-focus self-converging small-diameter lens array 21 arranged in the width direction.

As illustrated in FIG.
1, the photoreceptor 1 is exposed to light to prevent the developer from adhering to the non-image area.

〔Example〕

Sharp cut f of the electrophotographic apparatus of the present invention shown in FIG.
FIG. 3 shows a front view of an embodiment of the light emitting section of the LED array 20, which is the i-light source. LED20.・2021I203
... are arranged in a straight line at a pitch of 0.5 to 5 intestines. The LEDs 201, 202, 203, . . . emit light without interruption in the width direction of the photoreceptor. The length of the LED array 20 is set at the minimum length during image formation on the photoreceptor 1.
There is enough to cover the width So of the non-image area when (see FIG. 2).

In the LEI) array 20 configured in this way, for example, A
When forming images of four sizes, the LED is emitted by the width S of the non-image area.

The light emission distribution in the longitudinal direction (the width direction of the photoreceptor) of this LED array 20 is shown in FIG. Individual LED20□・2
02, 203, . . . have unevenness in light emission amount by about ±10 to 30%. Point P indicates the boundary of blinking at the exposure amount S (see FIG. 2).

FIG. 5 shows an example of the arrangement of the short-focus self-converging small-diameter lens array 21, in which each lens 211, 212
・213...This is an example of a single row of fists.

Short focus self-converging small diameter lens 211.21.・213・
. . is used as a plastic SELFOC lens (trade name) to form an array 21, and when the lens array 21 forms an image of the light emitted from the LED array 20 onto the photoreceptor l, the exposure amount distribution is shown in FIG. This is an indication. Although plastic SELFOC lenses have a relatively large aperture angle, their imaging performance is not very good. Therefore, the unevenness of the exposure amount is reduced due to image blurring, and the exposure amount at each position all exceeds the threshold value Q at which the copied image becomes white. If there is image blurring due to the lens array, the sharp cutting performance at the exposed edge will deteriorate.However, even if the sharp cutting performance deteriorates to this extent, the image area will still be slightly smaller than the size of the copy paper. Since the exposure amount is set to be small with a margin of , the exposure amount does not fall below the threshold value in the non-image area.

[Other Examples]

Figure 7 shows short focus self-converging small diameter lenses 211 and 212.
-213...This shows the exposure amount distribution when a glass SELFOC lens is used. The light emission distribution of the light source LED array 20 is as shown in FIG. In the case of a glass SELFOC lens, the resolving power is better than that of a plastic SELFOC lens, so the unevenness in the light emission distribution of the LED array 20 directly becomes the exposure amount unevenness on one surface of the photoreceptor. Since the aperture angle is about 20 degrees or less in half angle, which is smaller than that of a plastic cellular lens, the light transmittance is low and the amount of exposure is small overall. Therefore, the exposure amount may fall below the threshold value Q depending on the location.

There may be small areas where toner adheres in the form of black streaks. In such a case, each LED2
0. The amount of light emitted may be increased by increasing the current applied to the middle 2021+203, . . . -.

Plastic SELFOC lenses are made using diffusion copolymerization or photocopolymerization, so they can have a large difference in refractive index. Therefore, the aperture angle can be made sufficiently large. When the diameter of a plastic self-cleaning lens is 2 to 3 mmφ, N, A, (numerical aperture) ≧0.35, and the spatial frequency of resolving power (M, T, F,) is 20% at 6 mm/dia. It is as follows. On the other hand, glass SELFOC lenses are manufactured using ion exchange or ion implantation methods, so it is not possible to maintain a large difference between the refractive index at the center of the lens and the refractive index at the outer periphery.

Therefore, there is a limit to increasing the aperture angle. When the diameter of glass SELFOC lens is 1■φ, 0.1≦
N, A, ≦0.33, and the spatial frequency of resolution is about 50% at 6 lines/rats.

FIG. 8 is a front view of another embodiment of the light emitting part of the LED array 20, and is an example in which a plurality of LEDs are arranged in a staggered manner at a pitch.

FIG. 9 shows another embodiment of the arrangement of the convergent small diameter lens array 21, in which the convergent small diameter lens array 21 is arranged in two rows.

〔Effect of the invention〕

As described above, according to the electrophotographic apparatus of the present invention, since the non-image area is exposed to light, there is no possibility that a black frame will be formed on the periphery of the copy paper or that toner will be wasted.

The exposure width for this purpose is the light source LED array 2 that is imaged by the converging small diameter lens array 21.
It is regulated by 0 being lit. Each LED202/20
2 ・203...The pitch of the fist is sufficiently small and the lens array 21 has sufficient resolution for practical use, so even if the image area changes continuously, the sharp cut exposure amount will also be continuous accordingly. can be changed to

In addition, since the sharp cut exposure does not extend to the image area side, the contrast of the periphery of the copied image does not deteriorate or the area becomes white, which is an excellent feature.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an electrophotographic apparatus to which the present invention is applied;
Fig. 2 is a perspective view of the main parts, Fig. 3 is a front view of an embodiment of the light emitting diode array, Fig. 4 is a light emission distribution diagram of the light emitting diode array, and Fig. 5 is a diagram of the light emitting diode array. 6 and 7 are exposure distribution diagrams for the photoreceptor, FIG. 8 is a front view of another embodiment of the light emitting diode array, and FIG. 9 is a short focus self-focusing small diameter lens array. FIG. 3 is a front view of the embodiment. (2) is a photoreceptor, 20 is a light emitting diode array, 21 is a short focus self-focusing small diameter lens array 4. A41t image area width,
S is in the non-image area, 0 is the original.

Claims (1)

[Claims] 1. A light source array consisting of light emitting diodes and short-focus self-converging small-diameter lenses arranged in the width direction of the photoreceptor is turned on during image formation on the photoreceptor, so that no image is formed on the photoreceptor. 1. An electrophotographic apparatus characterized in that a 1-width area is exposed to light to prevent developer from adhering to the area.