JPH0455304B2 - - Google Patents

Description

Detailed Description of the Invention [Industrial Application Field] The present invention develops an electrostatic latent image using powdered toner, fixes the transferred recording paper with a heating roll, and smoothly discharges the image. This invention relates to an improvement of a copying apparatus that uses paper.

[Prior art]

The recording paper carried into the copying machine is fed in synchronization with the rotation of the photoreceptor drum, which is an image carrier, and transfers and carries the toner powder image of the document formed on the circumferential surface of the photoreceptor drum. Thereafter, it is separated from the photosensitive drum and conveyed to a fixing section.

As a means for fixing a toner powder image on a recording paper, a fixing method using a heating roll is known as the most efficient method and a method capable of obtaining a high-quality image.

That is, according to this method, the recording paper is continuously fixed and conveyed by the rotation of the heating roll without even temporarily stopping in the fixing section, so it is easy to synchronize with the cycle of the image forming section described above.
Further, since the toner powder is melted by high-temperature heating within a short period of time and is immediately fixed, it has the advantage that there is little disturbance in the image.

However, it also has the disadvantage that when the toner powder is in a molten state, it becomes sticky and adheres to the heating roll, making it difficult to separate the recording paper from the heating roll smoothly even after passing through the heating roll and completing fixing. are doing.

In particular, when a dense image is transferred to the leading edge of the recording paper, the amount of toner adhering to the heating roll is large, and the recording paper cannot be separated at all and winds up around the heating roll. Not only will this result in burnout, but it will also result in interruption of subsequent copying operations.

In order to prevent such accidents, a method was devised in which a non-image area is always provided at the leading edge of the recording paper, regardless of whether there is an image on the original, to prevent toner powder from being transferred to that area. However, one example of this is proposed in Japanese Patent Publication No. 54-36502.

In the above proposal, as shown in the cross-sectional view of the document table in FIG. A white light shielding part 3 is provided to prevent the leading edge 2a of the original 2 from being exposed to light.
Instead, a non-image area is provided at the leading end of the recording paper by recording an image on the white light-shielding portion 3.

According to this proposal, if exposure is performed only with the irradiation light A and the angle is constant, the tip portion 2a becomes a complete non-image area, and the above-mentioned effect can be expected due to this.
In the case of a copying machine that uses auxiliary light B from different angles in order to prevent the formation of shadows even when exposing pasted originals or originals with uneven surfaces, the auxiliary light B that comes into contact with the leading edge 2a of the original 2 is used. Portion 2b is underexposed compared to portion 2 of the document, and a gray document image is formed adjacent to the non-image area at the leading edge, resulting in a significant loss of copy quality.

In order to avoid such defects, it is of course conceivable to provide the light shielding section on the upper surface of the document table.

However, when white paint is applied to the glass surface of the document table, it becomes mirror-like and cannot diffusely reflect the irradiated light that has passed through the glass, and both sides of the non-image area at the tip become black, resulting in the above-mentioned problem. Not suitable for non-image area.

Alternatively, as shown in FIG. 2, a method can be considered in which a thin white light shielding member 5 is placed on the original table 1, and the entire surface of the document table is covered with a transparent sheet 6 and then glued. Since a small space 7 is unavoidably created between the edge and the transparent sheet 6, the space 7 becomes a shadow, resulting in black lines or fog on the recording paper.

Note that if a dry adhesive is used to adhere the transparent sheet 6, the space 7 can be made smaller, but this is not practical as it tends to cause bubbles and wrinkles and has poor workability.

[Purpose of the invention]

An object of the present invention is to provide a copying apparatus that provides a complete non-image area at the leading edge of a recording paper even when exposed to light from different angles, thereby preventing it from wrapping around a heating roller. It is something.

[Structure of the invention]

The present invention is constructed by covering and pasting a transparent sheet with white opaque printing at a position corresponding to the leading edge of the document, covering the entire surface of the document mounting table. In a copying apparatus that electrostatically transfers the formed toner powder image onto recording paper and then fixes the toner powder image on the recording paper with a heating roll, on the upper surface of the document mounting table,
This is achieved by a copying apparatus characterized in that a transparent sheet on which a white part is printed is attached to a portion corresponding to the leading edge of a recording paper, excluding the white part.

〔Example〕

One embodiment according to the invention is shown in FIG.

Reference numeral 10 indicates a part of the original document placement section provided on the top surface of the copying device 20, which is placed from a transparent glass plate facing an exposure device (not shown) built into the top of the copying device 20. A document mounting table 11 is installed.

A transparent sheet 13 on which a white light-shielding portion 14 according to the present invention is provided by printing or the like is tightly adhered to the entire upper surface of the document table 11, except for the light-shielding portion 14. It is in a state where it is held between scale plates 12 attached to the side ends of the document mounting table 11.

The unattached light shielding section 14 has a width slightly wider than the scale plate 12, so that the leading end 15a of the document 15 placed in contact with the scale plate 12 is exposed to the light source A or B of the exposure device. It is made of white printing that is opaque and capable of diffuse reflection so that it will not be exposed to radiation from outside.

Therefore, the thickness of the light shielding part 14 is extremely thin compared to other light shielding members, and may cause a step in the pasted transparent sheet 13, or may cause shadows on the image due to the thickness of the light shielding part 14. Such inconveniences do not occur at all. Furthermore, since the transparent sheet 13 itself can be made significantly thinner than a glass plate, the light shielding section 14 can be provided at a position extremely close to the image surface of the original 15.

That is, according to the present invention, the original 15 is covered with a completely flat transparent sheet 1 by the platen cover 16.
Since the light shielding part 14 is located extremely close to the image surface of the original 15, the light shielding part 14 can be placed in close contact with the image surface of the original 15, so that unnecessary black lines and fogging as in the conventional example are not caused. Even when irradiated from different angles, almost no shadows such as fog occur on the image.

The transparent sheet 13 used here is suitably a thin film that has high transparency and strong surface strength, and will not cause scratches on the contact surface with the original even after long-term use, such as polyester film. Good results have been obtained using polycarbonate and polycarbonate films.

In addition, the white light shielding part 14 is printed or coated with white printing ink.
For example, by mixing fine powder of magnesium oxide into this ink, the diffusion effect of the white portion can be enhanced. Of course, good results have also been obtained using white fluorescent ink or white fluorescent paint.

Such a transparent sheet 13 is adhered to the upper surface of the original table 11 with an adhesive, except for the white light-shielding portion 14, so as to prevent air bubbles or wrinkles from occurring therebetween. The adhesive used here is a transparent rubber-based adhesive, such as "water glue", and generally a quick-drying adhesive is not suitable.

〔Effect of the invention〕

According to the present invention, since the recording paper to which an image has been transferred always has a clear non-image area at its leading edge, the conventional accidents caused by the recording paper being wrapped around the heating roll can be prevented, and furthermore, the black line Copying apparatuses that can produce high-quality copies without fog or fog have now been provided.

[Brief explanation of the drawing]

1 and 2 are sectional views of main parts of a conventional document mounting table. FIG. 3 is a sectional view of a main part of a document mounting table in a copying apparatus according to the present invention. 10...Document placement unit, 11...Document placement table, 1
2... Scale plate, 13... Transparent sheet, 14
...light-shielding section, 13...manuscript, 15a... (manuscript)
Tip part, 16... platen cover, 20... copying device (part), A... irradiation light, B... auxiliary light.

Claims (1)

[Claims] 1. In a copying machine that electrostatically transfers a toner powder image formed on a photoreceptor drum onto a recording paper, and then fixes the toner powder image on the recording paper with a heated roll, 1. A copying apparatus characterized in that a transparent sheet having a white portion printed on a portion corresponding to the leading end of the recording paper is attached to the upper surface thereof, excluding the white portion.