JP2002014485A - Electrophotographic image transfer sheet and method for image formation by using the electrophotographic image transfer sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for image formation such that abnormality in an image, particularly a so-called worm-hole image in which the image except the outline is not transferred can be prevented by imparting proper elasticity to an electrophotographic transfer sheet of the device for image formation without using a special belt for image formation, and to provide the electrophotographic transfer sheet to be used for the device for image formation. SOLUTION: 1. The electrophotographic transfer sheet to be used for the method for electrophotographic image formation has at least one layer of an elastic layer which uses hollow particles on the transfer side of the supporting body of the sheet. 2. In the method for image formation, the image on a secondary transfer body transferred from a primary transfer body which carries the transferable image is transferred to the electrophotographic transfer sheet to form the image.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic transfer sheet, particularly to an electrophotographic transfer sheet having characteristics suitable for an image forming apparatus using an intermediate transfer belt, and an image forming apparatus using the transfer sheet. It is.

[0002]

2. Description of the Related Art An electrophotographic apparatus using an intermediate transfer member is
Since a color image can be created by sequentially stacking and transferring a plurality of component color images, not only can color misregistration be reduced when superposing toner images of each color, but also a variety of transfer sheets can be selected. It is a very effective method because it can be done. However, it is known that the physical properties of the intermediate transfer member, particularly its elastic modulus, greatly affect the image quality after transfer. For example, if the elasticity is too low, an image abnormality in which toner scatters around the image at the time of transfer tends to occur, and if the elasticity is too high, an image abnormality in which portions other than the outline of the image are not transferred occurs. To prevent this, the elasticity of the intermediate transfer member is adjusted, but the long-term reliability of the intermediate transfer member is reduced, and an image abnormality due to expansion and contraction is caused.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object the following:
Even if a special image forming belt is not used, by providing a moderate intermediate transfer body with elasticity on the side of the electrophotographic transfer sheet, image abnormalities, especially the so-called "worm-eating image" in which the outside of the contour part is not transferred, can be obtained. An object of the present invention is to provide an electrophotographic transfer sheet which does not occur, and an image forming method using the electrophotographic transfer sheet.

[0004]

According to a first aspect of the present invention, there is provided an electrophotographic apparatus for use in an electrophotographic image forming method, comprising an elastic layer using at least one hollow particle on a transfer-receiving side of a support. The present invention relates to an image transfer sheet for use. Second invention
The present invention relates to the first electrophotographic image transfer sheet used in an electrophotographic image forming method using an intermediate transfer member. The third aspect of the present invention relates to the electrophotographic image transfer sheet according to the above item 1 or 2, wherein the elastic layer has a thickness of 10 μm or more.

A fourth aspect of the present invention relates to the first to third electrophotographic image transfer sheets, wherein the hollow particles have a hollow ratio of 80% or more. The fifth aspect of the present invention is characterized in that the hollow particles are heat-expandable hollow particles and are in a state of being foamed before image transfer.
4. The image transfer sheet for electrophotography according to any one of 4. A sixth aspect of the present invention relates to the first to fifth electrophotographic image transfer sheets, wherein the elastic layer is formed by coating and calendered after coating.

A seventh aspect of the present invention is that the support is made of resin or paper,
Alternatively, the present invention relates to the first to sixth electrophotographic image transfer sheets, which are a composite material or a laminated material thereof. An eighth aspect of the present invention is the electrophotographic apparatus according to any one of the first to seventh aspects, wherein each of the front and back surfaces of the sheet has a surface resistance of 1 × 10 ¹³ Ω or less when conditioned at 20 ° C. × 65% RH. The present invention relates to an image transfer sheet. A ninth aspect of the present invention relates to the electrophotographic image transfer sheet according to any one of the first to eighth aspects, wherein the elastic layer has an uneven surface.

According to a tenth aspect of the present invention, a transfer image on a secondary transfer member transferred from a primary transfer member having a transferable image formed thereon is
The present invention relates to an image forming method, wherein an image is formed by transferring images onto the first to ninth electrophotographic image transfer sheets. An eleventh aspect of the present invention relates to the tenth image forming method, wherein the image is a color image.

In the present invention, the layer using hollow particles, especially 1 layer, is used on the copy side of the support of the electrophotographic transfer sheet.
By providing the layer having a thickness of 0 μm or more, the elasticity required for the secondary transfer body was imparted to the electrophotographic transfer sheet, and the above-mentioned problem could be solved. The reason for using the hollow particles is that air contained in the hollow particles serves as a cushion. As a means to fulfill the role of the cushion, the density of the support itself is reduced,
A method using the cushion is also conceivable, but in that case, the surface of the electrophotographic transfer sheet becomes rough, so that sufficient image quality cannot be obtained. On the other hand, when hollow particles are used as in the present invention, the surface becomes uniform, so that the transfer sheet for electrophotography is more sufficient than the surface obtained by reducing the density of the support itself. It became dense and sufficient image quality could be obtained.

The thermally expandable hollow particles used in the present invention are hollow plastic fillers containing, for example, a thermoplastic material as a shell and containing a low-boiling solvent therein, and have a property of expanding by heating. is there. Such thermally expandable hollow particles are conventionally known, and various types thereof can be used. As the thermoplastic resin serving as the shell of the thermally expandable particles, the same thermoplastic resin as the hollow particles can be used. Further, as the foaming agent contained in the shell, propane and butane are generally used.

The hollow ratio of the hollow particles is preferably 80% or more. This is because the higher the hollow ratio, the higher the elasticity even with the same thickness of the elastic layer. As the hollow particles, thermally expandable hollow particles are preferable, and it is preferable that the hollow particles are in a state of being expanded before the image is transferred.

When the heat-expandable hollow particles are used, a dispersion of the heat-expandable hollow particles is prepared and applied in an unfoamed state, and the hollow particles are foamed by heating for foaming after drying during drying. Is preferred. Two advantages are obtained by adopting such a foaming method. The first merit is that, similarly to the first and second cases, the hollow ratio can be made very large and the function as the elastic layer can be maximized. The second advantage is that when hollow particles having a large hollow ratio are used as they are for coating, they tend to float in the dispersion used for coating and have poor processability. The use of hollow particles is advantageous in that the stability of the dispersion is good and the workability is excellent because the specific gravity is small during coating.

When the elastic layer is formed by painting, it is preferable that the elastic layer is calendered after painting. That is, the elastic layer containing the hollow particles coated as described above,
The surface has reduced apparent smoothness. Although the image is unlikely to be abnormally generated by the action of the elastic layer as it is, extreme irregularities may occur, and it is preferable to perform a calendering process for the purpose of correcting this. As the calender, any of an on-machine calender and an off-machine calender such as a super calender can be used.

The support of the transfer sheet for electrophotography of the present invention includes resin or paper, or a composite material or a laminate thereof. The resin is preferably used as a sheet-like film, and as the resin, a thermoplastic resin, a thermosetting resin, or the like can be used. As the paper, for example, a paper at least partially composed of a paper-based layer containing cellulose fiber as a main component can be used, and a paper based on high-quality paper is generally used. Examples of the composite material include a resin film using cellulose fibers as a part of its constituent material, a resin film mixed with cellulose fibers and cellulose fibers, and a nonwoven fabric. Furthermore, as a laminated material, for example, an arbitrary resin is applied on paper by extrusion processing, or an adhesive is applied on a resin film previously processed into a sheet shape, and another paper is attached to this. And others.

The transfer sheet for electrophotography of the present invention has a temperature of 20 ° C.
It is preferable that both of the surface resistance values of the front and back surfaces of the sheet when the humidity is controlled at × 65% RH are 1 × 10 ¹³ Ω or less. That is, in the electrophotographic transfer sheet using the hollow particles as described above, it is observed that the electrical resistance value of the electrophotographic transfer sheet may increase due to the effect of the hollow particles used. However, when the sheet is used in an electrophotographic copying machine in a situation where the electric resistance value has increased, toner before fixing is scattered due to poor feeding due to adhesion between the sheets due to charging and influence of too high electric resistance. This may cause image abnormalities (often called "stickiness"), which is caused by the fact that the resistance value at the time of humidity control at 20 ° C. × 65% RH is reduced by 1 as described above.
It was found that improvement can be achieved by lowering the resistance to × 10 ¹³ Ω, preferably 1 × 10 ¹² Ω. Adjustment of the electric resistance value of the electrophotographic transfer sheet can be performed by using various commercially available conductive agents, including the conductive agent in the support or the elastic layer, or the support surface or the elastic layer. It may be applied to the surface or the like.

Further, the transfer sheet for electrophotography of the present invention comprises:
Irregularities can be provided on the surface of the elastic layer from an aesthetic point of view. That is, the present inventor has found that even when a design having irregularities is added to the surface by embossing or the like, the image is not extremely deteriorated. The unevenness is generally formed by the embossing described above, but may be formed by printing or the like. However, when these designs are added, it is preferable that the thickness of the elastic layer is equal to or larger than the size of unevenness caused by the designs. Even if the thickness is not more than the size of the irregularities, there is an effect of reducing the image abnormality, but the degree of the image abnormality tends to worsen.

In the formation of a color image by the image forming method of the present invention, for example, the color image formed on the primary transfer member is sequentially transferred to a secondary transfer member (intermediate transfer member), and the secondary transfer member (intermediate transfer member) The transfer can be carried out by transferring a plurality of color images transferred to the electrophotographic transfer sheet of the present invention.

As the primary transfer member and the secondary transfer member (intermediate transfer member) used in the image forming method of the present invention, those which have been conventionally used can be used.
A roller shape can be used.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hollow particles The hollow particles used in the present invention are, for example, those having a shell made of a thermoplastic resin and containing air or other gas inside. Examples of the resin include polystyrene, polyvinyl chloride, and polyvinyl chloride. Examples include vinylidene chloride, polyvinyl acetate, polyacrylate, polyacrylonitrile, polybutadiene, and copolymer resins thereof. Among these, a copolymer resin mainly containing vinylidene chloride and acrylonitrile is particularly preferable.

Elastic Layer The elastic layer using the hollow particles is prepared by dispersing the hollow particles in water together with a known binder resin such as a water-soluble polymer or an aqueous polymer emulsion, and applying the resultant to the surface of a support. Obtained by drying. The thickness of the elastic layer can be easily adjusted by the amount of dispersion of the hollow particles or the amount of the dispersion applied at this time, but is preferably 1 μm or more, and more preferably 10 μm or more in order to sufficiently function as the elastic layer. When the thickness is 20 μm or more, the effect as the elastic layer is maximized.

Binder Resin The amount of the binder resin to be applied is required to be an amount that strongly bonds the elastic layer to the support, and is usually 2 to 50% by weight based on the total amount of the hollow particles and the binder resin. Is preferred. If the amount is less than 2% by weight, the bonding strength of the hollow particles to the support is weak, and the peeling of the hollow particles becomes remarkable in an electrophotographic copying machine. If the content is more than 50% by weight, the elastic effect of the hollow particles may be lost by the binder resin.

The binder resin is appropriately selected from conventionally known water-soluble polymers and / or aqueous polymer emulsions. Specific examples thereof include water-soluble polymers such as polyvinyl alcohol, starch and derivatives thereof, cellulose derivatives such as methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose and ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, and acrylamide / acryl. Acid ester copolymer, acrylamide / acrylic ester / methacrylic acid terpolymer, styrene / maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, casein and the like. Also, as the aqueous polymer emulsion,
Latex such as styrene / butadiene copolymer, styrene / butadiene / acrylic copolymer, vinyl acetate resin, vinyl acetate / acrylic acid copolymer, styrene / acrylic ester copolymer, acrylic ester resin, polyurethane resin, etc. And the like.

[0022]

EXAMPLES The present invention will be described below with reference to examples, but these are only one embodiment of the present invention and the present invention is not limited thereto.

Example 1 Non-expandable plastic hollow particles 40 parts (solid content 23.4%, average particle size 3 μm, hollow ratio 30%) Styrene / butadiene copolymer latex 10 parts (solid content 47%) water 50 parts The mixture having the above composition was sufficiently stirred and dispersed to prepare an elastic layer forming liquid, and this was transferred to a commercially available electrophotographic transfer paper (with a basis weight of 7).
0 g / m ² ) to obtain a transfer sheet for electrophotography according to the present invention by applying and drying such that the layer thickness after drying becomes 10 μm.

Example 2 An electrophotographic transfer sheet of the present invention was obtained in the same manner as in Example 1 except that a commercially available OHP sheet for electrophotography was used for the support.

Example 3 An electrophotographic transfer sheet of the present invention was obtained in the same manner as in Example 1, except that coating and drying were performed so that the layer thickness became 20 μm.

Example 4 An electrophotographic transfer sheet of the present invention was obtained in the same manner as in Example 2, except that coating and drying were performed so that the layer thickness became 20 μm.

Example 5 Example 1 except that hollow particles having a hollow ratio of 80% were used.
In the same manner as in the above, an electrophotographic transfer sheet of the present invention was obtained.

Example 6 Example 2 except that hollow particles having a hollow ratio of 80% were used.
In the same manner as in the above, an electrophotographic transfer sheet of the present invention was obtained.

Example 7 Foamable hollow particles were applied so that the layer thickness became 30 μm.
Except for drying and foaming, a transfer sheet for electrophotography of the present invention was obtained in the same manner as in Example 1. In addition, Matsumoto Yushi Pharmaceutical F-30 was used for the expandable hollow particles, and the following formulation was used for the application liquid. For the foaming, a heat roller heated by a nip with a 50 kg spring and heated to a surface temperature of 150 ° C. was used. Expandable plastic hollow particles 25 parts Polyvinyl alcohol 5 parts Water 70 parts

Example 8 Foamable hollow particles were applied so that the layer thickness became 30 μm.
Except for drying and foaming, a transfer sheet for electrophotography of the present invention was obtained in the same manner as in Example 2.

Example 9 The electrophotographic transfer sheet of Example 7 was subjected to a super calender treatment to obtain an electrophotographic transfer sheet of the present invention having a layer thickness of 26 μm.

Comparative Example 1 A comparative electrophotographic transfer sheet was obtained in the same manner as in Example 1, except that the commercially available electrophotographic transfer sheet used for the support in Example 1 was used.

Comparative Example 2 An electrophotographic transfer sheet for comparison was obtained in the same manner as in Example 2 except that the commercially available OHP sheet for electrophotography used for the support in Example 2 was used.

Comparative Example 3 An electrophotographic transfer sheet for comparison was obtained in the same manner as in Example 1 except that coating and drying were performed so that the layer thickness was 5 μm.

Comparative Example 4 An electrophotographic transfer sheet for comparison was obtained in the same manner as in Comparative Example 3, except that the support was a commercially available OHP sheet for electrophotography.

Table 1 shows the results of these trial production conditions and image abnormalities.
It was shown to. Although a slight deviation occurred between the target layer thickness and the actually measured value, the difference was such that there was no problem in confirming the effect. The layer thickness was measured by observing the cross section after freezing and breaking with liquid nitrogen with a scanning electron microscope. Evaluation of image abnormalities was made by Ricoh Imageio
A copy was made on a Color 2800 and the image was used. However, in order to clarify the effect, the pressure of the transfer nip from the secondary transfer belt to the transfer-receiving sheet was arbitrarily increased slightly, and the test was performed under the condition that the problematic image abnormality “worm-eating image” easily occurs.

[0037]

[Table 1] Degree of insect-eating image; × = very noticeable, Δ = slightly noticeable, ○ = not noticeable, ◎ = not seen at all

[0038]

[Effect] 1. Claims 1 to 3 and 5 Because the elasticity of the air inside the hollow particles makes it difficult to produce a wormy image, even in a situation where a wormy image is likely to occur in the secondary transfer of an electrophotographic copying machine, in other words, in particular, it is particularly An apparatus which does not easily produce a worm-like image even with an electrophotographic copying machine using a conventional resin belt without using an elastic belt was obtained. 2. According to a fourth aspect of the present invention, there is provided an image forming apparatus in which, when the surface is roughened by the influence of the application of the hollow particles, the smoothness is corrected, and an image abnormality due to a decrease in the smoothness is less likely to occur. 3. 6. An image such as "battery" due to an excessive increase in surface resistance by lowering the surface resistance of an electrophotographic transfer sheet, which may increase when hollow particles are used, by using a conductive agent or the like. An image forming apparatus capable of preventing abnormalities was obtained. 4. According to a seventh aspect of the present invention, there is provided an image forming apparatus in which image abnormality is unlikely to occur even when a design due to unevenness is formed on the elastic layer by utilizing the elasticity of the hollow particles. 5. Claims 8 and 9 A transfer sheet for electrophotography suitable for the image forming apparatus was obtained. 6. Claims 10 to 11 Since the worm-like image is hardly generated by the elasticity of the air inside the hollow particles, even in a situation where the worm-like image is likely to be generated in the secondary transfer of the electrophotographic copying machine, in other words, special elasticity is required. An image forming method which does not easily produce an worm-like image even in an electrophotographic copying machine using a conventional resin belt without using a belt having the same was obtained.

Claims (11)

[Claims] 1. An electrophotographic image transfer sheet for use in an electrophotographic image forming method, comprising an elastic layer using at least one hollow particle on a transfer-receiving side of a support. 2. The electrophotographic image transfer sheet according to claim 1, which is used in an electrophotographic image forming method using an intermediate transfer member. 3. The elastic layer has a thickness of 10 μm or more.
Or the image transfer sheet for electrophotography according to 2. 4. The electrophotographic image transfer sheet according to claim 1, wherein the hollow particles have a hollow ratio of 80% or more. 5. The electrophotographic image according to claim 1, wherein the hollow particles are heat-expandable hollow particles and are in a state of being expanded before image transfer. Transfer sheet. 6. The image transfer sheet for electrophotography according to claim 1, wherein the elastic layer is formed by painting, and is calendered after painting. 7. The method according to claim 1, wherein the support is resin or paper, or a composite material or a laminate thereof.
7. The image transfer sheet for electrophotography according to any one of items 6 to 6. 8. The sheet according to claim 1, wherein the surface resistance values of both sides of the sheet are 1 × 10 ¹³ Ω or less when the humidity is controlled at 20 ° C. × 65% RH. Image transfer sheet for electrophotography. 9. The image transfer sheet for electrophotography according to claim 1, wherein the elastic layer has an uneven surface. 10. An electrophotographic image transfer sheet according to claim 1, wherein a transfer image on a secondary transfer member transferred from a primary transfer member having a transferable image formed thereon is transferred. An image forming method comprising: 11. The image forming method according to claim 10, wherein the image is a color image.