JP2748189B2 - Image transfer method - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an image transfer method for transferring an unexposed portion of an image forming sheet having an image-exposed photosensitive layer to an image receptor. More specifically, the present invention relates to an image transfer method capable of forming a multicolor image of excellent quality without misregistration by accurate alignment.

[Prior Art] In the printing industry, a prepress proof has been used as a means for checking the finish, color tone, and the like of a final printed matter before printing. As a method for preparing the prepress proof, a method has been proposed in which an image forming sheet having an image-exposed photosensitive layer is brought into contact with an image receptor such as paper under pressure, and an unexposed portion of the photosensitive layer is transferred to the image receptor. Have been. When the prepress proof is multicolor, that is, in the case of color proof, image transfer is performed by repeating at least two colors, generally four colors. In such multicolor image transfer, accurate alignment between the first color and the second color, and further between the second color and the third color, etc., is important for maintaining excellent image quality without misregistration.

A conventional image transfer method using the image forming sheet,
Hereinafter, description will be made with reference to FIGS. 7 and 8.

FIG. 7 shows a metal roller (1) with an image receptor (not shown) and an elastic roller (2) with an image forming sheet (not shown) driven by gears (3) and (4). It is sectional drawing which shows that it is in the state performed. The elastic roller is a roller covered with rubber or the like, and generally has a hardness of 60 to 90. Wedge marks (5) and (6) indicate the home position of the leading end of the image receiving sheet attached to the metal roller (1) and the image forming sheet attached to the elastic roller (2) in the rotational direction indicated by the arrow. The metal roller (1) and the elastic roller (2) are rotated in the direction of the arrow to set them at the image transfer start points (indicated by wedge marks (5) and (6)). Then, after stopping the rotation of the metal roller (1) and the elastic roller (2), as shown in FIG. 8, the elastic roller (2) is moved in the direction of the arrow around the rotation axis of the gear (4) as the driving mediating means. The rollers are moved so that both rollers come into contact with each other to form a nip pressure necessary for image transfer. After the nip pressure is formed, the connection between the elastic roller (2) and the driving mediating means (gear in the above description) is released, and then the metal roller (1) and the elastic roller (2) are rotated in the direction of the arrow by rotating the metal roller (1). To transfer from the image forming sheet to the image receptor.

However, when the above-mentioned transfer method was used, misregistration occurred between the first color and the second color, or between the second color and the third color, and the color proof was not satisfactory.

[Problems to be Solved by the Invention] The present inventors have conducted intensive studies on the cause of the misregistration, and as a result, depending on the conventional transfer method,
It is presumed that the following phenomenon has occurred.

For example, when the elastic roller is moved to perform pressure contact, the elastic roller moves about the rotation axis of a gear, which is a driving mediating means of the elastic roller, and is pressed against the metal roller. This contact pressing mechanism will be described in more detail with reference to FIGS. 9 to 11.

FIG. 9 shows a state in which the metal roller (1) and the elastic roller (2) are in contact at the positions of the wedge marks (5) and (6), which are transfer start points. When the elastic roller is further moved to the center of the rotation axis of the gear to be displaced toward the metal roller in order to apply a necessary nip pressure by the transfer pressure, the elastic portion (7, for example, a rubber coating portion) of the elastic roller is dented, and this denting is performed. A rotational displacement corresponding to minutes occurs between the wedge marks (5) and (6), as shown in FIG. This shift accumulates as a deformation of the elastic part (7) of the elastic roller (2). Since a slip occurs between the metal roller (1) and the elastic roller (2) in the process of forming a dent in the elastic roller (2), a wedge mark (5) of the metal roller and a wedge of the elastic roller as shown in FIG. A displacement occurs between the mark (6). This slip occurs when both the elastic roller (2) and the metal roller (1) are rotated by the gears (3) and (4) after the contact pressure, or the elastic roller (2) is rotated after the contact pressure. It has been found that this also occurs when the connection between the gear and the gear (4) is released and only the metal roller (1) is driven and rotated, and the elastic roller (2) is rotated by the rotation. Since the displacement caused by the slip causes the displacement of the transfer start position, the positioning in the transfer of the multicolor image is made inaccurate, and it becomes difficult to obtain an image with high registration accuracy.

An object of the present invention is to solve the problems of the above-described conventional image transfer method and to provide a multicolor image transfer method having excellent registration accuracy.

[Means for Solving the Problems] According to the present invention, the image forming sheet and the image receptor are rotated by rotating an elastic roller on which the image-formed image-exposed sheet is mounted and a metal roller on which the image receptor is mounted. Through a nip formed by the elastic roller and the metal roller to selectively transfer an unexposed portion of the image forming sheet to an image receptor. The alignment with the body is performed in the following steps: (a) The elastic roller on which the image forming sheet is mounted and the metal roller on which the image receptor is mounted are rotated in a non-contact state by a driving mediating means for interlocking to start transfer. Stopping the rotation of both rollers after the alignment, (b) moving one of the two rollers toward the other roller, (C) a step of releasing the contact between at least one of the rollers and the drive mediating means; and (d) increasing the contact pressure between the two rollers to a pressure necessary for transfer by moving the one of the rollers. (E) performing a transfer from the image forming sheet to the image receptor by driving and rotating any one of the rollers.

The image forming sheet and the image receptor used in the image transfer method of the present invention are described in Japanese Patent Application No.
This is described in detail in the specification of JP 63-166496. These will be briefly described. The image forming sheet includes a support and a photosensitive layer formed on one surface of the support.

As a support, it is stable to heat, chemicals, light, etc.,
In addition, a material that transmits active light rays for image exposure is preferable. For example, it is a film of cellulose acetate, polystyrene, polyvinyl chloride, polyethylene terephthalate, or the like.

The photosensitive layer is composed of (a) a photopolymerizable compound and a colorant, (b) a photopolymerizable compound, a thermoplastic resin, a colorant, and the like, and further contains a photopolymerization initiator, a thermal polymerization inhibitor, and the like. May be.

As the photopolymerizable compound, at least one selected from monomers, oligomers, and prepolymers is used. As the thermoplastic resin, a polymer which is thermoplastic and does not have photopolymerizability and has excellent compatibility with the photopolymerizable compound is used. As the colorant, those conventionally known as dyes and / or pigments are used. The thickness of the photosensitive layer is preferably about 0.5 to 5 μm.

Image receivers include art paper, coated paper, woodfree paper,
An arbitrary substrate such as a film is appropriately used.

Hereinafter, the image transfer method of the present invention will be described with reference to FIGS.

FIG. 1 shows the start of transfer of the metal roller (1) and the elastic roller (2) driven by the gears (3) and (4) as drive mediating means for interlocking the metal roller (1) and the elastic roller (2). The previous arrangement is shown.
The metal roller (1) and the elastic roller (2) are each driven and rotated to form an image receiver (not shown).
Then, an image forming sheet (not shown) is set at a position before the start of transfer. After being set at the position before the start of transfer, the rotation of the metal roller (1) and the elastic roller (2) is stopped, and the elastic roller (2) is moved in the direction of the arrow in FIG. Then, the metal roller (1) and the elastic roller (2) are brought into contact with each other. In this figure, the case where the elastic roller is moved is shown, but any roller may be moved. Next, after the connection between the elastic roller (2) and the gear (4) is released (FIG. 4), the elastic roller (2) is pressed against the metal roller (1) to make the nip pressure necessary for image transfer ( (Fig. 5). Next, by driving the metal roller (1) through the gear (3), the elastic roller (2) is rotated together to transfer the image from the image forming sheet to the image receiver (6th).
Figure).

[Effects of the Invention] According to the present invention, a metal roller and an elastic roller are brought into contact with each other with a weak pressure, and then one of the rollers is separated from a driving mediator, such as a gear or a belt, by means of a clutch mechanism or the like, and is necessary for transfer. Even if there is a displacement in the normal direction of both rollers in the process of forming the nip pressure, the shaft of the drive mediating means of one of the rollers (elastic roller in the above description) (the rotating shaft of the gear 4 in the above description) An image transfer method is provided in which a displacement between the contact points of the two rollers due to the displacement of the elastic roller centered on ()) does not occur.

That is, according to the present invention, there is provided an image transfer method that eliminates a shift in the contact position between the metal roller and the elastic roller in the process of forming the nip pressure after the contact between the two rollers, and has excellent transfer start position reproduction accuracy.

Further, according to the present invention, there is provided an image transfer method which is excellent in registration accuracy and suitable for transferring a multicolor image.

[Brief description of the drawings]

1 to 6 are explanatory views for explaining an image transfer method of the present invention. 7 and 8 are explanatory views showing a conventional image transfer method, and FIGS. 9 to 11 are explanatory views showing causes of misregistration in the conventional transfer method. 1: Metal roller, 2: Elastic roller 3: Gear, 4: Gear

Claims (1)

(57) [Claims] An image forming sheet and an image receiving member are rotated by rotating an elastic roller provided with an image-formed image forming sheet and a metal roller provided with an image receiving member. In the transfer method of selectively transferring an unexposed portion of the image forming sheet to an image receptor by passing through a nip formed from the image forming sheet, the alignment between the image forming sheet and the image receptor is performed in the following manner. An image transfer method characterized by comprising the steps of: (a) rotating in a non-contact state by a driving mediating means for interlocking an elastic roller attached with an image forming sheet and a metal roller attached with an image receptor to start transfer; Stopping the rotation of both rollers after performing the alignment for (b) moving one of the two rollers toward the other roller, (C) a step of disconnecting at least one of the rollers from the drive mediating means, and (d) a contact pressure between the two rollers, a pressure required for transfer by moving one of the rollers. (E) a step of performing transfer from the image forming sheet to the image receptor by driving and rotating any one of the rollers.