JPH04249278A - Transfer device - Google Patents

Abstract

PURPOSE:To prevent the surface of a photosensitive body from being hurt on the sharp parts of the projecting parts of a roughened surface, on a transfer device on which the surface of a transfer material supporting body formed with a dielectric film and a transfer drum is used. CONSTITUTION:As a characteristic, the projecting part of the roughened surface of the transfer material supporting body is a spherical surface or a surface approximate to a plane. This roughened surface is obtained in such a manner that spherical blast powder such as a glass bead is used and sandblast-processed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer device for an image forming apparatus such as a superimposed transfer type color copying machine.

0002

2. Description of the Related Art As shown in FIG. 4, in a color copying machine using an electrostatic photographic process, blue, green, and red color separation filters 2B, 2G, 2R and a yellow filter 2Y are sequentially passed onto one photoreceptor drum 1. The color-separated light image of the original 3 is exposed to form four types of latent images, and the respective latent images are transferred to yellow, magenta, cyan, and black developing units 4Y and 4M arranged around the photosensitive drum 1. , 4C, and 4BK, and the resulting four-color toner image is transferred from a paper feed section 6 to a transfer drum 5 that is in contact with the photoreceptor drum 1 and rotates synchronously at the same linear speed.
The transfer paper S is superimposed and transferred by the action of the transfer charger 7 onto the wound transfer paper S fed to the position , and after the four transfers are completed, the transfer paper is separated from the transfer drum 5 by the separating claw 8 at the part B. A color copying machine using a so-called color separation image overlapping transfer method, in which a color copy is obtained by fixing images in a fixing device 9, is well known.

As shown in FIG. 5, the above-mentioned transfer drum has a frame body made of metal such as aluminum, which is composed of annular parts 10 at both ends of the drum and a connecting part 11 connecting these parts; A dielectric material whose front and rear edges in the drum rotation direction are held by a connecting portion 11 of the frame, and whose side edges are in contact with the outer peripheral surface of the frame and are wound around the frame. It is formed into a hollow cylindrical shape by a transfer material support 12 made of a flexible film, and has a clamper 13 that grips the leading edge of the transfer paper S fed from the paper feed section 6 at the connection section 11 of the frame body. are widely used. As the transfer material support 12, for example, a polyethylene terephthalate film (trade name: Mylar) of about 75 to 150 μm is generally used. The four-color toner image is electrostatically attracted to the transfer material support 12 charged by the charging charger 14, adheres tightly to the transfer drum 5 without shifting, and rotates integrally with the transfer drum. They are superimposed and transferred without being shifted from each other.

[0004] In the transfer device having the above structure, it is important that the transfer material support and the transfer paper, and the transfer paper and the photosensitive drum are in close contact with each other without any gaps in the transfer section. When transfer paper is exposed to a humid atmosphere, it becomes wavy to various degrees depending on the degree of humidity or due to dryness. Air that has partially accumulated between the surface of the body and the back side of the transfer paper is difficult to escape to the surrounding area, and an air layer remains, and the transfer charger acts on the transfer paper through the air layer at the transfer section. Transfer defects occur in that area, resulting in blank copies.

[0005] Recently, the types of paper used in copying machines have increased, and it is now necessary to be able to use ordinary paper, and some papers are highly hygroscopic and have large waves or curls. In addition, for the purpose of adjusting charging characteristics, etc., moisture is intentionally added to control the humidity.

[0006] In view of the above-mentioned actual circumstances,
Publication No. 54 states that even when using regular paper in humid conditions during the rainy season, paper that has been intentionally humidity-controlled, or paper that is curled or wavy, uniform copies can be made without white spots. In order to obtain this, it has been proposed that the surface roughness of the transfer material support should be set to 10 to 30 microns.

[0007] By doing this, the suction force between the transfer material support and the transfer paper is reduced, so even when using transfer paper that is wavy or curled due to humidity or dryness, air can be removed. The layers can escape faster,
It is said that the entire surface of the transfer paper adheres to the transfer material support, eliminating transfer gaps and producing images without white spots. Incidentally, according to the JIS standard, surface roughness is expressed by the distance between two parallel straight lines when the standard length of the cross-sectional curve of the surface is sandwiched between two parallel straight lines. In other words, it merely represents the height between the deepest valley and the highest peak of the surface unevenness, and cannot be said to show the various aspects of the surface condition.

For example, as shown in FIGS. 6(a) and 6(b), even with the same surface roughness Rmax, the number of unevenness per unit length (
They may have different spatial frequencies (spatial frequencies), or may have a sawtooth shape or a sine curve shape, as shown in FIGS. 6(b) and 6(c). Furthermore, as shown in (d) and (e), the ratio of the area of the protrusion to the area of the recess may be different.

[0009] For the purpose of releasing an air layer when a transfer paper is adsorbed and supported on a transfer material support, the cross-sectional shape may not matter much as long as the surface roughness is the same, but there are other From this perspective, the cross-sectional shape of the surface may become an issue.

Sandblasting is used as a method to roughen the surface of the dielectric film forming the transfer material support, but alumina oxide powder has conventionally been generally used as the blasting powder from the standpoint of mass production and cost. . As shown in FIG. 7, the alumina oxide powder has a shape with sharp corners protruding in all directions and easily forms an uneven surface on the surface of the dielectric film, but some of the fragments pierce the dielectric film 12. Even if the cleaning process is carried out, the thorn-shaped thorns may remain stuck and cannot be removed, as shown by reference numeral 15 in FIG. 8, and even if they are removed, the dielectric film may be scratched.

[0011] When such a dielectric film is attached to a transfer drum as a transfer material support and rotated together with the photosensitive drum without the transfer paper being wound around it, the dielectric film remains stuck to the transfer material support. The remaining sharp alumina oxide spines and convex scratches generate pinholes or scratches extending in the circumferential direction on the surface of the photoreceptor drum. Even if the transfer paper is wound, if the size of the transfer paper is small, the same problem will occur because the transfer film will come into direct contact with the photoreceptor drum outside this range.

0012

SUMMARY OF THE INVENTION In view of the above-mentioned drawbacks of the conventional transfer material support having a rough surface, the present invention provides a transfer device equipped with a transfer material support that does not damage the surface of a photoreceptor. The challenge is to provide.

[0013]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention is characterized in that the protrusions on the rough surface of the transfer material support are spherical or nearly flat surfaces without sharp parts.

[0014]

[Operation] As mentioned above, since the convex part of the transfer material support is made into a spherical surface or a nearly flat surface without sharp parts, it is possible to rotate the transfer drum without wrapping the transfer paper around it, or to wrap a small-sized transfer paper around the transfer drum. Even if the surface of the transfer material support and the surface of the photoreceptor come into direct contact when the transfer material is attached and rotated, the surface of the photoreceptor will not be damaged.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a transfer material support 12 according to an embodiment of the present invention.
FIG. 2 is an enlarged view showing a cross-sectional shape near the surface of the wafer. The protrusions on the surface of this transfer film are spherical, and the valleys are also rounded, so that no particles of blast sand remain stuck in them.

Further, as shown in FIG. 2, the protruding portion can be formed into a flat shape without any sharp parts.

Forming these rough surfaces on the surface of the dielectric film is achieved by using spherical blasting powder such as glass beads instead of using sharp-shaped blasting powder such as alumina oxide during sandblasting. This is achieved by using flour.

FIG. 3 shows an enlarged external view of an example of glass beads used for this purpose. By performing sandblasting using glass beads with such a shape as blasting powder, there will be no fragments sticking into the dielectric film, and no convex scratches will occur, so the transfer drum can be moved without wrapping transfer paper. Even when it comes into contact with the photoreceptor drum and rotates, there will be no pinholes or scratches on the surface of the photoreceptor drum.

In order to increase the number of copies per unit time, the transfer drum is controlled to perform copying as quickly as possible by increasing the speed of the transfer drum for a certain period of time at a time when there is no problem with image formation. If the body has sharp parts, the photoreceptor will be more likely to be damaged as the speed increases, so the present invention is more effective. From the viewpoint of releasing air accumulated between the transfer film and the transfer material, the surface roughness of the transfer film may be 10 to 30μ.

[0021]

As described above, according to the present invention, when the transfer paper is not wound around the transfer drum or when a small-sized transfer paper is wound around the transfer drum, the transfer film on the transfer drum and the photosensitive There is no risk of pinholes or scratches on the photoreceptor drum even when it rotates in direct contact with the photoreceptor drum, and it also prevents white spots caused by air trapped between the transfer paper and the transfer film. be done.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a cross-sectional shape near the surface of a transfer material support according to an example of the present invention.

FIG. 2 is a cross-sectional view showing a cross-sectional shape near the surface of a transfer material support according to another embodiment of the present invention.

FIG. 3 is a perspective view showing the outer shape of an example of glass beads used in sandblasting to form a rough surface of the transfer material support of the present invention.

FIG. 4 is a sectional view showing the overall configuration of an example of a color copying machine using a transfer drum.

FIG. 5 is a perspective view showing the structure of the transfer drum.

6(a), (b), (c), (d), and (e) are cross-sectional views showing examples of different cross-sectional shapes with the same surface roughness; FIG.

FIG. 7 is an enlarged perspective view of aluminum oxide powder for sunblasting to roughen the surface of a conventional transfer material support.

FIG. 8 is an explanatory diagram illustrating problems in a conventional method of roughening the surface of a transfer material support.

[Explanation of symbols]

1 Photoreceptor drum 5 Transfer drum 10 Annular parts at both ends of the frame 11 Frame connection part 12 Transfer material support 13 Gripping means 15 Spiny fragments of blast powder

Claims (3)

[Claims] Claim 1: A metal frame body consisting of annular parts at both ends of the drum, a single connecting part connecting these parts and extending in the axial direction, and a front end edge and a rear end edge in the rotational direction of the drum. A transfer material support made of a dielectric flexible film held by the connecting part of the frame body and wound around the frame body with its side edges along the outer circumferential surface of the annular part of the frame body; The transfer material has a front end gripping means at a connecting portion of the frame, a transfer drum that rotates in synchronization with the photosensitive drum at the same circumferential speed, and the front end of the transfer material is gripped by the gripping means. A transfer device for an image forming apparatus that transfers a toner image formed on a photosensitive drum to a transfer material adsorbed and supported by the transfer material support, the surface of the transfer material support having a rough surface. The transfer device according to the invention, wherein the convex portion of the rough surface is a spherical surface or a nearly flat surface without sharp parts. Claim 2: The surface roughness of the transfer material support is 10.
2. The transfer device according to claim 1, wherein the transfer device has a thickness of ˜30 μ. 3. The transfer device according to claim 1, wherein the rough surface is formed by sandblasting using glass beads as blasting powder.