JP2002123032A - Electrophotographic transfer sheet and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic transfer sheet which ensures superior gradation reproducibility and line reproducibility of an image superior clearness of a color image and to provide an image forming method. SOLUTION: A porous coating layer is formed on the surface of a sheetlike base from a resin-containing bubble solution containing a water-soluble or water- dispersible resin as a principal component in such a way that the average pore diameter of pores in the surface part of the coating layer is adjusted to 0.5-30 μm. When an image is formed on the porous coating layer with an electrophotographic system printing machine by a method based on ISO-13660 draft standard-QEA(Quality Engineering Associates, Inc.), mottle in 40 μm tile size is <=6 GSV(gray scale value) and a clear color toner image can be formed on the resulting transfer sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer sheet for electrophotography and an image forming method. More specifically, when the present invention is used in a full-color or monochrome copier of an indirect dry electrophotographic system, and a printer, there is no disturbance of a mottle or a halftone dot in a recorded image portion and a high line reproducibility. The present invention relates to a transfer sheet capable of obtaining a high-quality image and an image forming method.

[0002]

2. Description of the Related Art Hitherto, in electrophotographic copying machines and printers, along with colorization and digitization, high quality of electrophotographic images has been studied. In particular, in electrophotographic full-color copying machines and printers,
In order to obtain high-quality images, digitization of image input / output has advanced, and image input methods, input image processing methods, developing methods, transfer methods, fixing methods, and the like have been greatly improved. Further, the developer and the image forming material of the photoreceptor have been improved in correspondence with digital high-definition and high-color-forming color recording.

However, in the above-described improved electrophotographic full-color copying machine and printer, when high-quality paper or coated paper is used as an image support, mottle or halftone printing is performed from a halftone portion to a high-density image portion in a solid image. There is a problem in that the points are distorted, and the sharpness of the image is impaired, and the image quality is lower than that of a photographic image and a printed image. Further, the glossiness of the high-density image portion becomes excessive, the difference in gloss between the halftone portion and the blank portion becomes remarkable, and there is a defect that a very unnatural impression is given as the whole image.

On the other hand, in electrophotographic full-color copying machines and printers, toners having high sharp-melt properties are used in order to meet the demand for good melting and color mixing properties of toners during heat fixing. .
However, when this type of toner is applied to plain paper, the molten toner tends to excessively enter the gaps between the fibers of the paper, and as a result, the granularity of the toner is deteriorated. Further, in the case of coated paper, since the penetration of the molten toner into the paper is small, the molten toner spreads on the surface of the coated paper, and in this case, too, the granularity of the toner deteriorates. Further, the line reproducibility of an image is also deteriorated due to the penetration of toner into gaps between fibers in plain paper and the spread of toner on the surface of coated paper. Therefore, whether you use plain paper or coated paper,
In both cases, there is a problem that the obtained image is inferior to the photographic image and the printed image.

In order to solve the above problem, Japanese Patent Laid-Open No. 9-1
Japanese Patent Application Laid-Open No. 71266 proposes a method of reducing the gloss of an image by providing a void layer for absorbing toner on an image support and embedding the toner in the void layer using a fixing device. However, the above method of embedding the toner in the void layer involves:
Although the toner swell can be suppressed to some extent,
The paper having the void layer easily adheres to the fixing device at the time of fixing, and is easily wrapped around. Therefore, there is a problem that the fixing device is broken and a normal image cannot be obtained. Then, in a low humidity environment, image defects such as discharge marks may occur.

Further, Japanese Patent Application Laid-Open No. Hei 5-297621 proposes a method in which a minute amount of pigment is applied on a base paper to form regular voids on the paper surface or the like, and the toner is fixed in the voids. Have been. However, a sufficient amount of voids cannot be ensured by merely applying a fine pigment, so that the toner cannot be sufficiently absorbed in the secondary color and the tertiary color having a large amount of toner. Cannot be avoided, gloss becomes high, and gloss unevenness and graininess cannot be improved.

Further, Japanese Patent Application Laid-Open No. 8-171306 proposes a method for controlling the gloss of an image by fixing conditions of an image forming apparatus. However, in the method of controlling the gloss of the image according to the fixing condition, the step between the image portion and the blank portion cannot be eliminated, and unevenness remains on the screen, so that the sense of incongruity in the image quality cannot be eliminated.

[0008]

SUMMARY OF THE INVENTION The present invention solves the above problems and provides an electrophotographic transfer sheet and an image forming method which are excellent in image gradation reproducibility, line reproducibility and color image clarity. What you want to do.

[0009]

An electrophotographic transfer sheet according to the present invention comprises a sheet-like support and one surface of the support.
Having a porous coating layer formed from a resin-containing foamed liquid containing a water-soluble or water-dispersible resin as a main component, wherein the average pore diameter of the pores in the surface portion of the porous coating layer is 0.5. From 30
When an image in the range of μm and an image was formed on the porous coating layer based on a method based on ISO-13660 draft standard / QEA using an electrophotographic printing machine, the mottle at a tile size of 40 μm was , 6
GSV (Grey Scale Value) or less. Further, in the transfer sheet for electrophotography of the present invention, an ISO-line of a line on which an image is formed on the porous coating layer by using an electrophotographic printing machine.
It is preferable that the ragedness based on the 13660 draft standard is 9 μm or less. In the transfer sheet for electrophotography according to the present invention, the diameter of pores having 50% or more of the total number of pores existing on the surface of the porous coating layer is 5 to 2 or less.
It is preferably in the range of 0 μm. Further, the electrophotographic image forming method of the present invention is characterized in that a color toner image is transferred and fixed to the electrophotographic transfer sheet of the present invention.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have made intensive studies to achieve the above object, and as a result, by forming a porous coating layer comprising a resin-containing film on a sheet-like support, The present inventors have found that the above problems can be solved by optimizing the average pore diameter, the open area ratio, and the density of the coating layer on the surface of the porous coating layer, and have completed the present invention. That is, in a full-color or monochrome copier of the indirect dry electrophotography system, and a transfer sheet used for recording by a printer, a resin-containing liquid is subjected to mechanical stirring to form and contain a large number of fine bubbles, and the bubble-containing resin is formed. Is coated on a sheet-like support and dried to form a porous coating layer, and the average pore diameter of the pores in the portion of the surface of the porous coating layer is controlled in the range of 0.5 to 30 μm. As a result, compared with the conventional transfer paper for electrophotography, it was possible to obtain a high-quality image in which the mottle and halftone dots were not disturbed in the recorded image portion and the gloss contrast between the blank portion and the image portion was small.

As the support used in the electrophotographic transfer sheet of the present invention, paper containing pulp as a main component, coated paper, laminated paper and the like, and woven fabric and non-woven fabric can be used. it can. Further, as a support, polyolefin,
Plastic films such as methacrylates and cellulose acetate, synthetic papers composed of polyolefins and pigments, and porous synthetic resin films such as foamed polyethylene terephthalate films and foamed polypropylene films can also be used. It should be noted that paper containing pulp as a main component, such as coated paper, has the advantage that it can be recycled when used as a support. At this time, if ECF or TCF pulp is used as the pulp, it is a preferable product in consideration of the global environment.

The support used in the electrophotographic transfer sheet of the present invention has a basis weight of 7 specified in JIS P8124.
Those in the range of 0 to 180 g / m ² , preferably 80 to 150 g / m ² are suitable. Specifically, plain paper such as high quality paper, medium quality paper, recycled paper, coated paper for printing, art paper,
Cast-coated paper can be used, but is not limited thereto. When the grammage is less than 70 g / m ² , the stiffness of the transfer sheet becomes weak, and as a result,
In a roll-type fixing device, the transfer sheet tends to wind around the roll, and the transfer sheet tends to curl after fixing the toner. Conversely, if it exceeds 180 g / m ² , the amount of heat required to embed the toner in the image receiving layer of the transfer sheet becomes insufficient, and there is a possibility that uneven gloss may occur.

In particular, a so-called coated paper produced by applying a paint containing a pigment and an adhesive as a main component to the surface of paper and smoothing the surface with a super calender or the like,
It can be suitably used as a support. In the present invention, when coated paper is used as the support, the surface can be easily flattened when the porous coating layer is formed by applying the bubble-containing liquid. The adhesion to the recording medium is improved, and mottle is less likely to occur, and an extremely good recording screen can be obtained.

When the transfer sheet for electrophotography is printed using an electrophotographic printing machine, ISO-1366 is used.
0 Draft standard and QEA-compliant method (N.
Jones, S.M. J. Sargeant, J.M. C. B
riggs, and M.R. K. Tse: IST NIP
14 International Conference
e on Digital Printing Techn
In this case, the mottle at a tile size of 40 μm based on the technologies (1998) was set to 6 GSV (gray scale value: value at 256 tones) or less, thereby realizing excellent image tone reproducibility.

According to the ISO-13660 draft standard, an image having a minimum size of 20 mm × 20 mm is defined as a 2 mm image.
Divide into × 2 mm cells, measure the optical density of each cell,
The standard deviation of all measurements is defined as mottle. However, the human eye is more sensitive to non-uniformities in finer parts than 2 mm × 2 mm, so making the cell range smaller makes it closer to the naked eye. In addition, since the optical density and the amount of reflection of light from the surface have a logarithmic relationship, analysis based on the optical density is not suitable for images in which the change in the amount of reflection is wide, such as color printing, and ,
It would be better to measure other physical values that are linearly related to the amount of light reflection. Therefore, in the QEA improvement method, the size of the measurement range is made variable, and the nonuniformity (unevenness) in the smallest range is measured. In the QEA improvement method, a physical property value for evaluating the amount of reflected light is also represented by a gray scale value that is linearly related to the amount of reflected light (the reflectance is set to 256 gradations so that the white portion is 0 and the solid colored portion is 255). , The gray scale value of each cell is measured, and the standard deviation of each measured value in the entire measurement range is calculated. , Defined as mottle. In this patent, QEA
Based on the improved method, the entire measurement range of the image was 400 μm × 40
0 μm, the size of each cell was 40 μm × 40 μm, and the standard deviation in the entire measurement range of the gray scale measured for each cell was defined as mottle.

[0016] The transfer sheet of the present invention, when an image is formed on the above-mentioned electrophotographic transfer sheet by using an electrophotographic printing machine, by controlling the ridgedness based on the ISO-13660 draft standard to 9 μm or less. This makes it possible to form an image with excellent line reproducibility.

According to the ISO-13660 draft standard, when the reflectance of the maximum density of the line image portion is 0% and the reflectance of the blank portion is 100%, the portion having a reflectance of 60% or less is the image portion and the reflectance is 60%. % Is defined as a blank page. The standard distance between the ideal edge and the actual edge when the ideal edge is drawn parallel to the line so that the area of the blank part included in the image part and the area of the image part included in the blank part become the same. The deviation is defined as the ragedness.

The porous film constituting the coating layer of the transfer sheet of the present invention is mainly composed of a transparent resin or a transparent resin and a pigment. It can be formed by forming and containing a large number of bubbles, applying the resin solution containing the bubbles on a support, and drying.

To form the porous coating layer of the present invention, a water-soluble resin or a water-dispersible resin is used, and various kinds of processing such as polyvinyl alcohol and its derivatives having various molecular weights and saponification degrees, and oxidized starch are used. Starch and its derivatives are used. For example, various modified starches such as oxidized starch; cellulose derivatives such as methoxycellulose, carboxymethylcellulose, methylcellulose, and ethylcellulose; sodium polyacrylate, polyvinylpyrrolidone, acrylamide / acrylate copolymer, acrylamide / acryl Water-soluble resins such as acid ester / methacrylic ester copolymers, alkali salts of styrene / maleic anhydride copolymers, polyacrylamide and derivatives thereof, and polyethylene glycol;
And polyvinyl acetate, polyurethane, styrene / butadiene copolymer, acrylonitrile / butadiene copolymer, polyacrylate, vinyl chloride / vinyl acetate copolymer and polybutyl methacrylate, ethylene
Water-dispersible resins such as latex such as vinyl acetate copolymer, styrene-butadiene-acrylic copolymer and polyvinylidene chloride; and glue, casein, soy protein, gelatin, sodium alginate, etc. . However, it is not limited to these.
These resins can be used alone or as a mixture of two or more, if necessary.

The pigment contained in the porous coating layer of the present invention includes, for example, zinc oxide, titanium oxide, calcium carbonate,
Inorganic pigments such as silicate, clay, talc, mica, calcined clay, aluminum hydroxide, barium sulfate, lithopone, silica, and colloidal silica; polystyrene, polyethylene, polypropylene, epoxy resins, and styrene-acrylic copolymers Organic pigments called plastic pigments processed into various shapes such as spheres, hollows, spines, donut and flat shapes; and starch powder, cellulose powder and the like can be used, but are not limited thereto. Not something. In addition, these pigments can be used alone or in combination of two or more as needed.

In the present invention, the method of generating and dispersing air bubbles in the resin-containing liquid (foaming method) is, for example, used in a stirrer having a stirring blade rotating while performing planetary motion, for example, a foaming machine for confectionery, generally emulsified dispersion and the like. A homomixer, a stirrer such as a Cowles dissolver, or an apparatus capable of dispersing and mixing air as fine bubbles, for example, mechanically stirring while continuously feeding a mixture of air and a resin-containing liquid into a closed system, for example, Continuous foaming machines such as Gaston County of the United States and Stoke of the Netherlands can be used, but are not particularly limited thereto.

A foam stabilizer or a foaming agent may be added to the resin-containing liquid. These improve the stability of the bubbles in the bubble-containing liquid when bubbles are formed and contained in the resin-containing liquid, the mechanical stirring ability is insufficient, and the desired bubble-containing state is not obtained, or It is added when necessary. Foam stabilizers or foaming agents include, specifically, higher fatty acids such as stearic acid and palmitic acid, higher fatty acid salts such as sodium lauryl sulfate, ammonium stearate and ammonium palmitate, and alkyl alkanolamides and sorbitan fatty acid esters. The higher fatty acid modified products are particularly suitable because they have a high effect of enhancing the foaming property of the resin-containing liquid and improving the dispersion stability of the bubbles. Although there is no strict restriction on these choices, it is preferable to avoid those which may significantly impair the fluidity of the resin-containing mixed liquid or impair coating workability. Further, the compounding amount of the foaming agent and the foaming agent, the solid content of 100 parts by weight of the resin or the mixture of the resin and the pigment, the solid content is 30 parts by weight or less,
Preferably, the amount is in the range of 1 to 20 parts by weight, and even if it is added in an amount of more than 30 parts by weight, the desired effect of addition cannot be improved.

The surface electric resistance of the porous coating layer of the present invention is:
Normally 1 × 10 ⁸ to 1 ×
It is adjusted to a range of 10 ¹² Ω, preferably 1 × 10 ⁸ to 1 × 10 ¹¹ Ω, and more preferably 1 × 10 ⁹ to 1 × 10 ¹¹ Ω. If it is lower than 1 × 10 ⁸ Ω, the transfer of the toner to the transfer sheet in a high-humidity environment may be insufficient, and the density may be reduced or the density may be uneven. It is 1
If it exceeds × 10 ¹² Ω, the toner may be scattered when the transfer sheet is peeled off from the photoreceptor after the toner transfer in a low humidity environment, and the image may be disturbed and the image quality may be deteriorated. Examples of the conductive agent include inorganic salts such as sodium chloride, potassium chloride, magnesium chloride, sodium sulfate, and sodium aluminate; electronic conductive conductive agents such as zinc oxide, tin oxide, and titanium oxide; and styrene-maleic acid copolymer. The combined salts, quaternary ammonium salts such as alkyltrimethylammonium chloride, dialkyldimethylammonium chloride and alkylbenzyldimethylammonium chloride are preferably used, but are not limited thereto.

The coating method for forming the porous coating layer on the support includes a Meyer bar method, a gravure roll method, a roll method, a reverse roll method, a blade method, a knife method, an air knife method, an extrusion method, and a cast method. Etc. can be arbitrarily selected from known methods.

The transfer sheet having a porous coating layer according to the present invention can obtain a good image even when the bubble-containing resin mixed liquid is applied and dried, but if necessary, it can be further coated with a metal roll. Using a super calender composed of a resin roll, or a metal roll and a cotton roll as appropriate, the porous coating layer is subjected to a finishing treatment to further improve the smoothness of its surface. be able to. After coating, the semi-dried or dry sheet is brought into contact with a mirror-finished heated or non-heated cast drum or the like to further improve the surface smoothness of the porous coating layer. Is also good.

However, when the above-mentioned smooth finishing treatment is performed under excessive pressure, the resin wall surrounding the air bubbles of the porous coating layer is broken, the coating layer is densified, and the heat insulation and cushioning properties are reduced. In addition, since the pores on the surface of the porous coating layer may be destroyed and the excellent transfer performance of the porous coating layer may be lost, it is necessary to appropriately set processing conditions in the above-mentioned smooth finishing treatment.

Further, when the transfer sheet of the present invention is manufactured by applying the bubble-containing liquid on the sheet-like support, the transfer sheet itself is subjected to the coating in the steps of coating, drying and winding. Curling may occur with the surface inside or outside. In this case, when the transfer sheet is cut and processed into an image forming sheet having a predetermined size, the sheet may not be normally supplied to the image forming apparatus, and the running property in the apparatus may deteriorate. Troubles may occur.

In order to prevent various troubles caused by such curling, it is desirable to minimize the difference in shrinkage or expansion between the porous film and the support during heating. For this purpose, an anti-curl layer may be coated or laminated on the back surface of the transfer sheet, that is, on the surface opposite to the porous coating layer. There is no limitation on the material, forming method, coating amount, laminating amount, etc. of the anti-curl layer, and various types such as the type of support, the thickness or the properties of the porous coating layer, that is, the material composition, expansion ratio, coating amount, etc. In consideration of the above factors, optimization can be achieved.

Further, depending on the selection of the material of the support, when the transfer sheet travels in the image forming apparatus, it receives various frictional forces derived from the mechanism of the apparatus, or the humidity inside the apparatus decreases due to heating, As a result, static electricity may be charged on the transfer sheet. When a large number of images are continuously formed in such a state, an image forming surface of the transfer sheet,
The back surface of the next transfer sheet electrostatically adheres to the transfer sheet, making it difficult for the transfer sheet to peel off. In particular, since various types of plastic sheets and synthetic paper are inherently easily charged, when they are used as a support, static electricity is generated during the cutting process and during storage after processing, so that the sheet may be charged. Front and back hardly come off. As a matter of course, even when paper is used as the support, the above-mentioned troubles may occur.

It is extremely effective to form a so-called antistatic layer on the back surface of the transfer sheet in order to prevent troubles caused by such charging. Further, in order to prevent troubles due to charging, it is effective to use an antistatic material or to reduce the friction coefficient between the back surface of the transfer sheet and the porous coating layer (the surface of the transfer sheet). As described above, the antistatic layer can be formed by appropriately selecting from a wide range of materials and methods similarly to the formation of the anti-curl layer.

If the ratio of the pores having a diameter larger than 20 μm among the pores on the surface of the porous coating layer is too high, the reproducibility of the image is deteriorated. Further, when the distribution ratio of pores having a diameter of less than 5 μm increases, the maximum glossiness after printing increases because toner is not embedded in the pores.

Next, a color image forming method will be described. The toner used in the indirect dry type full-color electrophotographic copying machine and the printer is required to have good melting property and color mixing property when heat is applied. Therefore, it is preferable to use a toner having a high sharp melt property. The toner can be produced, for example, by melt-kneading, pulverizing, and classifying a toner-forming material such as a binder resin such as polyester, a colorant, and a charge control agent.

FIG. 1 is an example of a schematic sectional view of an electrophotographic apparatus for forming a full-color surface image used in the present invention.
The electrophotographic apparatus includes a transfer material transport system provided from the lower side of the apparatus main body to a substantially central portion of the apparatus main body, and a transfer drum 10 constituting the transfer material transport system at a substantially central portion of the apparatus main body. The latent image forming section is roughly divided into a latent image forming section and a developing device arranged close to the latent image forming section.

The transfer material transport system includes, at the lower side of the apparatus main body, supply trays 15 and 16, feed rollers 17 and 18 disposed almost directly above the respective trays, Paper feed guides 19 and 20 are provided near the mouth roller, and a transfer material separating charger 21 is provided near the outer peripheral surface near the paper feed guide 20. The transfer device 11 and the electrode 24 are disposed on the inner peripheral side, and the transfer drum 10 is rotatable in the direction of the arrow, the contact roller 23 that is in contact with the outer peripheral surface, the transfer device 13, and the transfer device The fixing device 14 includes a fixing device 14 disposed close to the end in the transport direction and a detachable discharge tray 22.

The outer peripheral surface of the latent image forming section has the transfer drum 1
An electrostatic latent image holding member (photosensitive drum) 1 which is disposed in contact with the outer peripheral surface of the photosensitive drum 0 and is rotatable in the direction of an arrow;
A charger 8 disposed near the outer peripheral surface of the electrostatic latent image carrier; and an image exposure device such as a laser beam scanner for forming an electrostatic latent image on the outer peripheral surface of the electrostatic latent image carrier. A writing unit 9 having a unit and an image exposure / reflection unit such as a polygon mirror, and a cleaning unit 12 are provided.

The developing device comprises a developer carrier 7 and a housing 6, and is formed on the outer peripheral surface of the electrostatic latent image holder at a position facing the outer peripheral surface of the electrostatic latent image holder 1. Black developing machine 2 for visualizing the formed electrostatic latent image,
It has a magenta developing machine 3, a cyan developing machine 4 and a yellow developing machine 5.

A sequence when an image is formed by the electrophotographic apparatus having the above configuration will be described by taking a full color mode as an example. The above-described electrostatic latent image holder 1
Is rotated in the direction of the arrow, the surface of the electrostatic latent image holding member is uniformly charged by the charger 8. Next, an electrostatic latent image is formed on the electrostatic latent image holder 1 through a writing device 9 by a laser beam modulated by a black image signal of a document (not shown), and the electrostatic latent image is formed by a black developing machine 2. Image development takes place.

On the other hand, the transfer sheet conveyed from the supply tray 15 or 16 via the paper feed rollers 17 or 18 and the paper feed guides 19 or 20 is applied to the transfer rollers 23 or 23.
Is electrostatically wound around the transfer drum 10 by an electrode 24 opposed to the transfer drum 10. The transfer drum 10 includes the electrostatic latent image holder 1
Rotates in the direction of the arrow in synchronization with the
The developed image developed by the transfer device 1 is a portion where the outer peripheral surface of the electrostatic latent image holder 1 and the outer peripheral surface of the transfer drum 10 are in contact with each other.
1 transcribed. The transfer drum 10 continues to rotate, and prepares for the transfer of the next color (magenta in FIG. 1).

The electrostatic latent image carrier 1 is neutralized by a static eliminator (not shown), is cleaned by a cleaning device 12, is uniformly charged again by the charger 8, and is converted to the next magenta image signal. Based on the image exposure, an electrostatic latent image is formed and developed by the magenta developing device 3 to form a visible image. Subsequently, a visible image is similarly formed for cyan and yellow colors. When the transfer for four colors is completed, the multicolored visual image formed on the transfer sheet is transferred to the charger 21.
, And is sent to the fixing device 14 by the paper conveying device 13,
After fixing by heat and pressure, a series of full-color image forming sequences is completed.

The main part of the fixing device 14 is composed of a heat roll 14a and a pressure roll 14b having the same structure. The heat roll 14a has 50 inside.
A substrate roll made of a steel core material having an outer diameter of 44 mmφ, provided with a 0 W Colts lamp, and a fluorine-based rubber having a rubber hardness of 60 and a thickness of 40 μm provided on the substrate roll via a primer as appropriate. (For example, Viton rubber manufactured by DuPont). On the other hand, the pressure roll 14b has the same configuration, and has an outer diameter of 48 mm.
It is composed of a substrate roll made of a φ steel core material and an elastic layer made of silicon rubber with a thickness of 1 mm provided on the substrate roll, and the other configurations are exactly the same as those of the heat roll 14a.

The heat roll is supplied with a release agent composed of dimethylpolysiloxane containing a functional group (for example, an amino group) in order to modify the surface of the fluororubber to a highly releasable surface. As a supply means, an oil donor roll made of silicone rubber is brought into contact. The oil donor roll is supplied with a release agent by an oil pickup roll immersed in an oil pan.

The heat roll 14a and the pressure roll 14b are pressed against each other by a pressure mechanism, and a nip width of 6 mm is formed at the center. In addition, both rolls are set so that the surface temperature is set to 150 ° C., and the rolls are rotated so that the surface speed in the direction of the arrow becomes 160 mm / sec. However, for paper having a basis weight of more than 105 g / m ² , the paper is rotated so that the surface speed becomes 60 mm / sec.

[0043]

The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto. Note that “parts” and “%” in Examples and Comparative Examples are
Unless otherwise specified, "parts by solids" and "% by weight" are indicated.

Example 1 Preparation of Resin Mixture Aqueous polyurethane resin (trade name: Adekabon Titer HUX-381: 50 parts, manufactured by Asahi Denka Kogyo KK, trade name: R-9679: 50 parts, manufactured by Zeneca Corp.) , 100 copies,
5 parts of higher fatty acid amide-based foam stabilizer (manufactured by San Nopco Co., Ltd., trademark: DC-100A), 3 parts of carboxymethyl cellulose for viscosity adjustment (for thickening) (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trademark: AG gum) . Using a stirrer (trade name: Kenmix Iiko PRO, manufactured by Aikosha Seisakusho Co., Ltd.), the resin mixture of the above composition (solid content: 30%) was stirred at a stirring speed of 490 rpm for 3 minutes to perform a foaming treatment.

Preparation of Transfer Sheet Immediately after the foaming of the bubble-containing resin mixture,
Coating is performed on the surface of a high-quality paper having a basis weight of 130 g / m ² using an applicator bar so that the coating amount (dry amount) is 10 g / m ^2, and the paper moisture immediately after opening is 5.0%. The resultant was dried to form a porous coating layer, and the transfer sheet of Example 1 was produced.

Preparation of Color Toner A cyan toner was prepared by mixing 96 parts by weight of a polyester resin, 1 part by weight of a charge controlling agent, and 3 parts by weight of a cyan pigment. Further, the magenta toner, the yellow toner, and the black toner were similarly prepared using a magenta pigment, a yellow pigment, or a black pigment instead of the cyan pigment of the cyan toner. The volume average particle diameter D50 of these cyan toner, magenta toner, yellow toner, or black toner was 7 μm.

Picture Transfer Test The transfer sheet and the color toner described above were applied to the electrophotographic apparatus shown in FIG. 1 and subjected to a picture paint test under an environment of 23 ° C. and 50% RH. Electronic As black toner 1.0 mg / cm ² of toner amount of input halftone dot area percentage of 100% unit's a picture condition on the transfer sheet, the yellow, magenta, cyan toners becomes 0.65 mg / cm ² The photographic equipment was adjusted. In addition, the evaluation chart used for the drawing has a primary color of yellow, magenta, cyan, black, a secondary color of red, green, and blue, and a tertiary color of yellow, magenta, and cyan. Of which the dot area ratio varies from 0 to 100%.
In addition, the squares of the solid colored portions were 10 mm square, and the lines used for measurement were vertical lines in an area of 475 pixels (0.881 mm) and horizontal lines in an area of 640 pixels (1.187 mm).

Image Evaluation Images were evaluated using an automatic printer image quality evaluation system (APQS; manufactured by Oji Scientific Instruments). The outline of this system is as follows. Three-board CCD camera: XC
-003 (manufactured by Sony Corporation), stereo microscope: SMZ-U
(Nikon Corporation) Lighting: Lumina Ace LA150S
E (manufactured by Hayashi Watch Industry Co., Ltd.).

The mottle of the image was 10 μm using APQS.
m, yellow, magenta, cyan,
A 100% solid image of a single black color was evaluated by a method based on ISO 13660 draft standard / QEA, and the average was used as the mottle of the evaluation sample.

The image ragedness was evaluated by an ISO 13660 draft standard for an image in which the vertical and horizontal lines of yellow, magenta, cyan, and black were captured by APQS, and the average was taken as the ragedness of the evaluation sample.

The granularity of the image was visually determined for the fixed image. When the graininess was equivalent to that of JD paper of Fuji Xerox Co., Ltd., it was evaluated as △, when it was better, ○, and when it was worse, ×.

Judgment of Discharge Mark The transfer sheet was allowed to stand for more than 10 o'clock in an environment of 10 ° C. and 15%, and then subjected to a drawing test in the same manner as described above. The judgment of the discharge mark was evaluated as ○ when no discharge mark was generated, and as X when generated.

Judgment of Transferability The transferability was determined by visually observing the fixed image. If no transfer omission occurred, it was judged as ○, and if it occurred, it was judged as x.

Evaluation of wrapping around and adhesion to the fixing unit Evaluation of wrapping around and adhesion to the fixing unit is made by visually checking whether the wrapping around the fixing unit is actually performed using the chart or whether the trace of the adhesion remains on the image area of the transfer sheet. Was determined.

Results of Example 1 As a result of the above test, the transfer sheet of Example 1 had a mottle of 4.7, a rage edge of 8.9, and an average pore diameter of 10 μm on the surface of the porous coating layer. .2 μm,
62% of the total pore number had a pore diameter in the range of 5-20 μm. The graininess was evaluated as ○, no discharge mark was generated, no transfer failure occurred, no winding around the fixing device and no trace of adhesion, and the quality was good.

Example 2 A resin mixture having the following composition (solids concentration 30
%) Was foamed in the same manner as in Example 1. The expansion ratio was 1.6 times. 100 parts of an aqueous polyurethane resin (manufactured by Asahi Denka Kogyo Co., Ltd., trade name: Adekabon Titer HUX-381), higher fatty acid amide-based foam stabilizer (manufactured by San Nopco Co., Ltd., trade name: DC-)
100A) 5 parts, 3 parts of carboxymethyl cellulose for viscosity adjustment (for thickening) (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trademark: AG gum). A transfer sheet was produced in the same manner as in Example 1. Example 2
In the transfer sheet of No. 5, the mottle was 5.2, the ragedness was 8.6, the average pore diameter of the surface of the porous coating layer was 9.7 μm, and 59% of the total number of pores was 5 to 20 μm.
m in the range of m. The graininess evaluation was ○,
There was no discharge mark, no transfer failure, no winding around the fixing device, no trace of adhesion, and the quality was good.

COMPARATIVE EXAMPLE 1 A resin mixture of the same composition as in Example 1 was applied to the surface of a high-quality paper having a basis weight of 80 g / m ² using an applicator bar (dry matter) without foaming. Coating was performed so as to be 10 g / m ^2, and drying was performed so that the paper moisture content was 5.0%. In the transfer sheet of Comparative Example 1, the mottle was 6.8, the ragedness was 9.7, and the average pore diameter on the surface of the coating layer was 0.1.
μm and only 1% of the total number of pores had a pore diameter in the range of 5-20 μm. × for graininess evaluation
Met. In addition, no discharge mark was generated, no transfer failure occurred, and there was no winding around the fixing device or no trace of adhesion.

COMPARATIVE EXAMPLE 2 A resin mixture having the same composition as in Example 1 was stirred at 490 rpm for 30 minutes with the same stirrer as in Example 1, and allowed to stand for 5 minutes after foaming. coating amount with an applicator bar on the surface of the quality paper of m ² (amount of dry matter) is then applied so that the 10 g / m ^2, and dried so that the paper moisture is 6.0% by porosity To form a functional coating layer,
A transfer sheet of Comparative Example 2 was produced. In the transfer sheet of Comparative Example 2, the mottle was 6.2 and the ragedness was 9.4.
The average pore diameter of the surface of the porous coating layer is 34.
At 6 μm, 36% of the total number of pores had a pore diameter in the range of 5-20 μm. The evaluation of graininess was Δ, but discharge marks were generated. In addition, there is no improper transfer,
There was no wrapping around the fixing unit or no trace of adhesion.

Comparative Example 3 As a transfer sheet, a commercially available transfer sheet for electrophotography (R transfer paper for electrophotography manufactured by Fuji Xerox Co., Ltd.) was used as it was. When the transfer sheet of Comparative Example 3 was evaluated in the same manner as in Example 1, the mottle was 7.0, the ragedness was as high as 9.9, the average pore diameter on the surface was 2.0 μm, and 7% of the total number of pores. Had a pore diameter in the range of 5-20 μm. The evaluation of graininess was "A". No discharge mark was generated, no transfer failure occurred, and there was no winding around the fixing device and no trace of adhesion.

Comparative Example 4 A commercially available transfer sheet for electrophotography (transfer paper J for electrophotography manufactured by Fuji Xerox Co., Ltd.) was used as it was as a transfer sheet. When the transfer sheet of Comparative Example 4 was evaluated in the same manner as in Example 1, the mottle was 9.8 and the ragedness was 1
It was as high as 0.9, the average pore diameter of the surface was 1.1 μm, and only 3% of the total number of pores had a pore diameter in the range of 5 to 20 μm. The evaluation of graininess was "A". No discharge mark was generated, no transfer failure occurred, and there was no winding around the fixing device and no trace of adhesion.

Comparative Example 5 As a transfer sheet, a commercially available electrophotographic transfer sheet (J-coated paper for electrophotographic transfer paper, manufactured by Fuji Xerox Co., Ltd.) was used as it was. When the transfer sheet of Comparative Example 5 was evaluated in the same manner as in Example 1, the mottle was 6.7, the ragedness was as high as 9.4, and the average pore diameter on the surface of the coating layer was 0.4.
1 μm and only 1% of the total number of pores had pores in the range of 5-20 μm. The evaluation of graininess was "A". No discharge mark was generated, no transfer failure occurred, and there was no winding around the fixing device and no trace of adhesion.

Table 1 shows that the transfer sheets of Examples 1 and 2 and Comparative Examples 1 to 5 have the mottle, the ragedness and the 5 to 20 μm.
2 shows the distribution ratio of pores having a pore diameter of.

[0063]

[Table 1]

[0064]

According to the present invention, by adopting the above-mentioned specific structure, even in an image formed on a transfer sheet by a copying machine and a printer for full-color electrophotography, the gradation reproducibility of the image, the line reproducibility, and the like can be improved. An electrophotographic transfer sheet having excellent color image clarity and an image forming method can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an indirect dry electrophotographic apparatus for carrying out an image forming method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Electrostatic latent image holder 2 ... Black developing machine 3 ... Magenta developing machine 4 ... Cyan developing machine 5 ... Yellow developing machine 6 ... Housing 7 ... Developer carrier 8 ... Charging device 9 ... Writing device 10 ... Transfer drum DESCRIPTION OF SYMBOLS 11 ... Transfer device 12 ... Cleaning device 13 ... Conveying device 14 ... Fixing device 14a ... Heat roll 14b ... Pressure roll 15, 16 ... Supply tray 17, 18 ... Supply roller 19, 20 ... Supply guide 21 ... Charging device 22: discharge tray 23: contact roller 24: electrode

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yo Nakamura 1-10-6 Shinonome, Koto-ku, Tokyo Inside Oji Paper Co., Ltd. Shinonome Research Center (72) Inventor Kiyoshi Hosoi 2274 Hongo, Ebina-shi, Kanagawa Prefecture Fuji Zero (72) Inventor Ryosuke Nakanishi 2274 Hongo, Ebina-shi, Kanagawa Prefecture Fuji Xerox Co., Ltd.

Claims (4)

[Claims] 1. A sheet-like support, comprising, on one surface of the support, a porous coating layer formed from a resin-containing foamed liquid containing a water-soluble or water-dispersible resin as a main component, The average pore diameter of the pores in the surface portion of the porous coating layer is in the range of 0.5 to 30 μm, and the porous coating layer is subjected to ISO-13660 draft standard QEA using an electrophotographic printing machine. (Quality Engineer
ring Associates, Inc. The mottle at a tile size of 40 μm when an image is formed based on a method conforming to (6) is 6 GSV (Grey Sc).
(Ale Value) or less. 2. An ISO-136 line formed on the porous coating layer by using an electrophotographic printing machine.
Ragedness based on 60 draft standards is 9
2. The transfer sheet for electrophotography according to claim 1, which has a thickness of not more than μm. 3. The transfer sheet for electrophotography according to claim 1, wherein the diameter of pores having 50% or more of the total number of pores existing on the surface of the porous coating layer is in the range of 5 to 20 μm. 4. An electrophotographic image forming method, comprising: transferring and fixing a color toner image to the electrophotographic transfer sheet according to claim 1.