JP2789225B2 - Image forming method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method, and more particularly to a full-color image forming method with good color mixing.

[Prior Art] At present, color copiers have gradually begun to penetrate the market, and the replacement of monochrome copiers with color copiers has begun to progress. However, for people who have seen more beautifully processed color images, such as televisions, photographs, and color prints, full-color electrophotographic images currently in practical use are not always satisfactory.

Indeed, in the Journal of the Society of Electrophotography, Vol. 26, No. 1 (1987), etc., a technical approach for improving the image quality of electrophotography has been made, and application of the technology to color copying is also being studied. . However, the current level is approaching photography and printing, but it has not reached the level where it is comparable. The greatest concern of color copying in electrophotography is how to achieve perfect color mixing and faithful reproduction of fine lines.

Color image formation by full-color electrophotography generally reproduces colors using three color toners of three primary colors, yellow, magenta, and cyan.

In this method, an electrostatic latent image is formed on a photoconductive layer by passing light from a document through a color separation light transmission filter having a complementary color relationship with the color of the toner. Next, the toner is held on a support through development and transfer steps. Subsequently, the above-described steps are sequentially performed a plurality of times, and while the registration is being performed, the toner is superimposed on the same support, and a final full-color image is obtained by one-time fixing.

One of the decisive differences between electrophotography and printing is that in electrophotography the main focus is on the use of plain paper as the image support, whereas in printing the image support depends on the printed document. Being able to choose the body. Particularly in the case of multi-color printing using gravure printing or high-grade offset printing, printing paper is carefully selected, and in many cases, so-called coated paper, in which irregularities on the paper surface are significantly reduced, is generally used.

Plain paper generally used in electrophotography has a relatively large surface irregularity having a Beck smoothness of about 20 to 50 (seconds), a low fiber density, and many voids between fibers. For this reason, the toner after the transfer falls into the voids of the fibers or is unevenly arranged due to the unevenness of the fibers.

Further, in the case of color copying in which three or four toners including black toner are superimposed, it is more susceptible to the influence of the unevenness of the paper fibers and the gap between the fibers. I can't get it.

That is, if the toner layer, which is the image surface, is smooth, the incident light enters the toner layer without causing irregular reflection, absorbs and transmits only a specific wavelength in the toner layer, and then emits light having a desired specific wavelength. Will be in our eyes. However, if the toner layer has a rough surface, the incident light will be scattered more, and it will not be possible to obtain a sufficient amount of light inside the toner layer. Becomes

Conventionally, in order to deal with these problems,
No. 64 and Japanese Patent Application Laid-Open No. 63-92965 disclose a technique for providing a transparent resin layer on an image support. Of note in these methods is the softening point of the selected transparent resin. If the softening point of the resin is lower than that of the toner as described in the above publication, the toner itself does not cause a high-temperature offset when passing through a fixing device, particularly a heating roll fixing device, but the resin layer provided on the support has a high-temperature offset. Inconvenience is likely to occur, for example, Japanese Patent Application Laid-Open No. Sho 62-232671 proposes that the same thermoplastic resin is used for the toner receiving layer and the toner.

Although the method can prevent the toner and the receiving layer from being separately offset from each other, at the time of heating roll fixing,
The toner is taken into the inside of the receiving layer, and especially thin lines such as characters and lines in the image, which are parts with little toner, are compatible with the resin constituting the surrounding receiving layer and apparently bleed and thicken the characters, A reduction in sharpness results in image defects.

In the above-mentioned publication, it is described that it is more preferable that the toner can be buried in the toner-receiving layer by press-fitting. And the intention is greatly different.

Further, JP-A-48-81539 and JP-A-50-81339 disclose the technology of a toner transfer electrophotographic film having a resin layer on a plastic film.
These are all those in which a matting agent is contained in the resin layer, and a device for intentionally giving irregularities to the resin layer has been devised. Such a method has a different purpose from a method of forming a color image having excellent color mixing properties by superposing several kinds of toner layers having a smooth surface, which the present inventors consider.

[Problems to be Solved by the Invention] As described above, according to the present invention, in forming a full-color image by superimposing toner, color mixing and sharpness capable of faithfully reproducing an original document are obtained, and a heating roll is used. An object of the present invention is to provide an image forming method in which no offset occurs when a fixing device is used.

[Means and Actions for Solving the Problems] According to the present invention, on a transparent coat layer of an image support having a transparent coat layer on the surface, a yellow toner, a magenta toner, a cyan toner and a black toner are selected. that a combination of color toner to form a color toner image, the full color toner image in the image forming method of heat-fixing to the image support, the temperatures T ₁ the apparent melt viscosity of the color toner is 10 ⁵ poise, the and temperature T ₂ of the apparent melt viscosity of the coating layer member for forming a transparent coating layer is 10 ⁵ poise,
The present invention relates to an image forming method characterized by satisfying the following relationship: 3 ° C. <T ₂ −T ₁ <40 ° C.

In the heating roll fixing method, when the image support is passed through a heating roll, the melt apparent viscosity of the toner on the support is understood to be generally fixable with less than 10 ⁵ poise. Temperature sheet passing speed of the heating roll, a toner size of paper is selected in accordance with the melting of the toner appropriately, the melt viscosity of the toner low temperature setting is higher than 10 ⁵ poises to an image support on Are not sufficiently fixed, and poor fixing occurs due to easy peeling due to weak rubbing or bending.

However the present inventors have completed the interest to the present invention the temperature at which the apparent melt viscosity of the toner and the coat layer member considered whether the critical viscosity toner is fixed becomes 10 ⁵ poise.

That is, in the present invention, the temperature T _{1 at} which the apparent melt viscosity of the color toner is 10 ⁵ poise and the apparent melt viscosity of the coat layer member for forming the transparent coat layer are 10 ⁵
And temperature T ₂ which is a poise, it is better to satisfy the following relationship _{3 ℃ <T 2 -T 1 <} 40 ℃.

Relative temperatures T ₁ that the apparent melt viscosity of the color toner is 10 ⁵ poise, temperature T ₂ of the apparent melt viscosity of the coating layer member for forming a transparent coating layer is 10 ⁵ poise 3
If the temperature is not higher than 0 ° C., that is, if T ₂ −T ₁ is 3 ° C. or less, the toner and the coating layer member are compatible and integrated when passing through the fixing roll, and as described above, the reproducibility of the fine line is hindered. . Relative temperatures T ₁ that the apparent melt viscosity of the color toner is 10 ⁵ poise, temperature T ₂ of the apparent melt viscosity of the coating layer member for forming a transparent coating layer is 10 ⁵ poise
Is higher than 40 ° C., that is, when T ₂ −T ₁ is higher than 40 ° C., the coating layer member is not subjected to any thermal deformation when passing through the roller, so that sufficient adhesion between the toner and the coating layer can be obtained. Instead, the toner is peeled off by the rubbing of a nail or the like. In particular, it is remarkable in fixing a full-color image in which four color toners are layered.

Therefore, the temperatures T ₁ , T _{2 of} the color toner and the coat layer member
The preferred range of the difference is 5 ° C. <T ₂ −T ₁ <35 ° C., and more preferably 8 ° C. <T ₂ −T ₁ <27 ° C.

As the color toner and the coating layer member used in the present invention, a general thermoplastic resin having transparency can be used.

For example, polystyrene, chloropolystyrene, poly-α
-Methylstyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene-maleic acid copolymer, Styrene-acrylate copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer,
Styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-phenyl acrylate copolymer), styrene-methacrylic ester copolymer (styrene-methyl methacrylate copolymer, styrene-methacrylic acid) Styrene type such as ethyl copolymer, styrene-butyl methacrylate copolymer, styrene-phenyl methacrylate copolymer), styrene-α-methyl methacrylate copolymer, styrene-acrylonitrile-acrylate copolymer Resin (a homopolymer or copolymer containing styrene or a substituted styrene), vinyl chloride resin, styrene-vinyl acetate copolymer, rosin-modified maleic acid resin, phenol resin, epoxy resin, polyester resin, low molecular weight polyethylene, low Molecular weight polypropylene, Iono Chromatography resins, polyurethane resins, silicone resins, ketone resins, ethylene - ethyl acrylate copolymer, a xylene resin, polyvinyl butyral resin. In particular, in the color toner of the present invention, particularly preferred resins include styrene-acrylate resins and polyester resins.

In particular, (Wherein R is an ethylene or propylene group, x and y are each a positive integer of 1 or more, and the average value of x + y is 2 to 10) or a bisphenol derivative represented by the formula: A carboxylic acid component composed of a carboxylic acid or an acid anhydride or a lower alkyl ester thereof as a diol component (for example, fumaric acid, maleic acid, maleic anhydride, phthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid) And a polyester resin obtained by co-condensation polymerization with at least one acid is more preferable because of having sharp melting properties.

As the image support, paper, cloth, polyester film, vinyl chloride film, butadiene film, polyvinylidene fluoride film and the like can be used.

The thickness of the transparent coat layer is in the range of 10 to 500 μm, preferably 25 to 300 μm. As the image support, in particular, when using paper or cloth, a thickness sufficient to cover the irregularities and pores of the support is necessary. It is.

The following pigments or dyes may be mentioned as colorants suitable for the color toner of the present invention. In the present invention, CIDisperse Y164, CISolvent Y77 and C.
Colorants such as I. Solvent Y93 are not recommended.

As the dye, for example, CI Direct Red 1, CI
Direct Red 4, CI Acid Red 1, CI Basic Red 1, CI Modern Red 30, CI Direct Blue 1, CI Direct Blue 2, CI Acid Blue 9, CI Acid Blue 15, CI Basic Blue 3, CI Basic Blue 5, There is CI Modant Blue 7.

As the pigment, naphthol yellow S, Hansa yellow G, permanent yellow NCG, permanent orange GTR, pyrazolone orange, benzidine orange G,
Permanent Red 4R, Watching Red Calcium Salt, Brilliant Carmine 3B, Fast Violet B, Methyl Violet Lake, Phthalocyanine Blue, Fast Sky Blue, Indanthrene Blue BC
There is.

In particular, pigments such as disazo yellow, insoluble azo,
Copper phthalocyanine is preferred, and a basic dye or an oil-soluble dye is preferred as the dye.

Particularly preferably, CI Pigment Yellow 17, CI Pigment Yellow 15, CI Pigment Yellow 13, CI Pigment Yellow 14, CI Pigment Yellow 12, CI
Pigment Red 5, CI Pigment Red 3, CI Pigment Red 2, CI Pigment Red 6, CI Pigment Red 7, CI Pigment Blue 15, CI Pigment Blue 16, or a phthalocyanine skeleton having the structural formula (1) shown below. And copper phthalocyanine pigments having 2-3 substituted groups.

Dyes include CI Solvent Red 49, CI Solvent Red 52, CI Solvent Red 109, CI Basic Red 12, CI Basic Red 1, and CI Basic Red 3b.

In the present invention, apparent viscosity and glossiness were determined according to the following methods.

Apparent viscosity measurement: Use a flow tester model CFT-500 (manufactured by Shimadzu Corporation). The sample weighs about 1.0 to 1.5 g of a 60mesh pass product. This is pressed for 1 minute at a load of 100 kg / cm ² using a molding machine. The pressurized sample is subjected to a flow tester measurement under the following conditions under normal temperature and normal humidity (temperature: about 20 to 30 ° C., humidity: 30 to 70% RH) to obtain a temperature-apparent viscosity curve. From smooth curve obtained, determine the temperature at which the apparent viscosity becomes 10 ⁵ poise.

RATE TEMP 6.0D / M (℃ / 1 minute) SET TEMP 70.0DEG (℃) MAX TEMP 200.0DEG INTERVAL 3.0DEG PREHEAT 300.0SEC (second) LOAD 20.0KGF (kg) DIE (DIA) 1.0MM (mm) DIE (LENG 1.0MM PLUNGER 1.0CM ² (cm ² ) Glossiness measurement: Using a VG-10 gloss meter (manufactured by Nippon Denshoku), measure each solid image used for chromaticity measurement as a sample image.

For measurement, first set to 6V with a constant voltage device. Next, the light projection angle and the light reception angle are each adjusted to 60 °.

Using the zero point adjustment and the standard plate, after the standard setting, the sample image is placed on the sample table, three white papers are superimposed and measured, and the numerical value indicated on the mark is read in%. At this time, S, S / 10 changeover switch is set to S, angle, sensitivity changeover
SW is adjusted to 45-60.

 Use a sample with an image density of 1.5 ± 0.1.

 Hereinafter, the present invention will be described in detail with reference to examples.

Examples Example 1 A color toner was obtained using the following formulating amounts of a coloring agent and a charge control agent with respect to 100 parts by weight of a polyester resin obtained by condensing propoxylated bisphenol and fumaric acid.

The mixture having a predetermined amount of each of the above components is sufficiently premixed with a Henschel mixer, melt-kneaded for at least two times with a three-roll mill, cooled, roughly crushed to about 1 to 2 mm using a hammer mill, and then cooled. The powder was finely pulverized to a particle size of 40 μm or less by a pulverizer using an air jet method.
Furthermore, the obtained finely pulverized product was classified, and 2 to 20μ was mainly selected so as to have an average particle size of 8μ to obtain a classified product. 0.5 parts by weight of silica fine powder treated with hexamethyldisilazane as a flow improver was externally added to 100 parts by weight of each classified product to obtain a color toner.

To 4 to 6 parts by weight of the color toner, a vinylidene fluoride-tetrafluoroethylene copolymer (copolymer weight ratio 8: 2) and styrene-2-ethylhexyl acrylate-methyl methacrylate (copolymer weight ratio 45:20) were used. : 35) to 5
Cu-Zn coated about 0.5% by weight at a weight ratio of 0:50
A two-component developer was prepared by mixing -Fe-based ferrite carrier (average particle size: 48 µm; 250 mesh pass, 350 mesh on 79% by weight; true density: 4.5 g / cm ³ ) so that the total amount becomes 100 parts by weight.
In consideration of color tone reproducibility and toner scattering, the developer concentrations of the yellow, magenta, cyan, and black color toners were set to 4% by weight, 5% by weight, 6% by weight, and 5% by weight, respectively.

A copy test was performed using a color electrophotographic apparatus having the OPC photosensitive drum shown in FIGS. 1 and 2 and a supply-development system.

The development and transfer of each color toner were performed in the order of magenta toner, cyan toner, yellow toner, and black toner. At the time of transfer, the transfer current supplied to the transfer corotron was 200 mA for the magenta toner, 250 mA for the cyan toner, 300 mA for the yellow toner, and 350 mA for the black toner.

The replenishment toner sent by the supply screw 16 in the toner transport cable 4 is supplied to the developing device 2-2 through the toner replenishment port 15.
And supplied into the developing device. When the developing device rotates and comes to a position facing the photosensitive drum 1, the replenishment toner is uniformly mixed with the developer within a very short time by the mixing-conveying screw 12, and the two-component developing with a constant developer concentration is performed. It became an agent. The amount of the developer becomes a fixed amount by the developer regulating blade 14 on the developing sleeve 13, and the developer is reversely developed by using the J / B developing method at the opposite portion of the photosensitive drum 1 having the negatively charged electrostatic latent image. The negatively charged toner was transferred onto the photosensitive drum by the method.

Next, the toner image on the photosensitive drum 1 was transferred via the transfer charger 8 to an image support having a transparent coat layer electrostatically attracted to the transfer drum 6 previously conveyed from a paper cassette. The support further passed through a heat fixing roller 10 to form a final full-color copy.

FIG. 3 shows a temperature-apparent viscosity curve of the toner and the coat layer member used in the examples.

Using a high-density high-quality paper as the image support,
The coating layer is made of 10 g of a polyester resin composed of terephthalic acid, trimellitic acid, propoxyl bisphenol, and ethoxylated bisphenol in methyl ethyl ketone 1
The mixture was dissolved in 00 g, and coated on the high-quality paper using a No. 14 bar coater.

The obtained full-color copy was excellent in color tone of a color original and reproducibility of a character portion. The chromaticity diagram at that time is shown in FIG.

The glosses of the monochromatic images of yellow, magenta, and cyan used for the chromaticity measurement were 27%, 32%, and 25%, respectively.

Repeated copying was performed on 5,000 sheets using the image support having the transparent coating layer described above, but no offset occurred on the heat fixing roll.

Example 2 A styrene-acryl copolymer composed of styrene, methyl methacrylate, and 2-ethylhexyl acrylate was used as a coat layer member, and a colorant for magenta was CI Pigment Red 122 4.0 parts and CI Solvent Red 49 1.
A copy test using magenta single color was performed in the same manner as in Example 1 except that the number of copies was changed to 0.

An image with excellent brightness and saturation and high gloss (gloss) was obtained. By the way, the gross at this time was 38%.

Comparative Example 1 Instead of the image support having the transparent coat layer of the present invention,
Full-color copying was performed using high-quality plain paper.

The chromaticity at that time is shown in FIG. It can be seen that the hue is similar to that of Example 1, but the saturation is clearly reduced. Yellow, magenta and cyan gloss
They were 15%, 18% and 16%.

Example 3 A cyan colorant was replaced with a styrene acrylic copolymer composed of styrene-butyl acrylate-maleic acid-2-ethylhexyl acrylate as a binder resin for a toner.
The test was conducted in the same manner as in Example 1 except that the CI pigment blue 15 was changed to 6.0 parts by weight, and the yellow colorant was changed to 2.3 parts by weight of CI Disperse Yellow 54. An image with excellent lightness and saturation, high gloss, and good color balance was obtained. FIG. 3 shows a temperature-apparent viscosity curve of the used toner.

Example 4 Full-color copying was performed in the same manner as in Example 1 except that the transparent coat layer member was changed to a styrene-acryl copolymer made of styrene-butyl methacrylate made of a polyester resin. A full-color image with higher gloss and excellent chroma than in Comparative Example 1 was obtained. FIG. 3 shows a temperature-apparent viscosity curve of the coating layer member.

Example 5 The transparent coat layer member was made of epoxy resin, and the image support was
Full-color copying was performed in the same manner as in Example 1 except that a polyethylene film having a thickness of 200 μm was used. OH
The P image was excellent in yellow transparency.

Comparative Example 2 Full-color copying was performed in the same manner as in Example 1 except that the binder resin for toner used in Example 3 was used as the transparent coating member. The obtained image had noticeable fatness and bleeding of the characters, and particularly had a sharp bleeding, especially for a type having a size of 5 points or less, and made the fine line breaks in the character part unclear.

After repeated copying using this image support,
When only 1200 sheets were copied, the offset to the heating roller was large and the entire image was offset.

[Effects of the Invention] In the present invention, the apparent melt viscosities of the toner and the coating layer member are reduced.
By defining the temperature difference of 10 ⁵ poise in an appropriate range, color mixing and sharpness capable of faithfully reproducing the original can be obtained, and there is no offset to the heating roller.

[Brief description of the drawings]

1 is a schematic view of a color electrophotographic apparatus having an OPC photosensitive drum, FIG. 2 is a schematic view of a replenishment-development system of the apparatus of FIG. 1, and FIG. −
FIG. 4 shows an apparent viscosity curve, and FIG. 4 shows a chromaticity diagram of a color original.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G03G 13/01 G03G 15/01-15/01 117 G03G 13/20 G03G 15/20-15/20 302

Claims (3)

(57) [Claims] 1. A full-color toner image is formed by combining a color toner selected from the group consisting of a yellow toner, a magenta toner, a cyan toner and a black toner on the transparent coat layer of an image support having a transparent coat layer on the surface. formed, the color toner image in the image forming method of heat-fixing to the image support, the temperatures T ₁ the apparent melt viscosity of the color toner is 10 ⁵ poise, coating layer for forming a transparent coating layer the image forming method of the apparent melt viscosity of the member and the temperature T ₂ to be ¹⁰⁵ poise, characterized in that it satisfies the following relationship _{3 ℃ <T 2 -T 1 <} 40 ℃. 2. The image forming method according to claim 1, wherein said image support is formed by forming said transparent coat layer on the surface of paper or cloth. 3. An image support comprising a polyester film,
2. The image forming method according to claim 1, wherein the transparent coat layer is formed on a surface of a vinyl chloride film, a butadiene film or a polyvinylidene film.