JPH0441347B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to color electrophotography, and more particularly to a color electrophotography method capable of obtaining clear and wide-ranging color tones. Traditionally, electrophotography has been covered by U.S. Patent No.
No. 2297691, Special Publication No. 23910, Special Publication No. 1977-
As described in Publication No. 24748, uniform electrostatic charge is applied to the photoconductive layer by corona discharge,
By exposing this to a light image according to the original, the electric charge in the exposed portion is extinguished and a latent image is formed. Development is carried out by depositing a finely powdered electrostatic substance, so-called toner, on the obtained electrostatic latent image. The toner is attracted to the electrostatic latent image depending on the amount of charge on the photoconductive layer, forming a toner image having a density. This toner image is transferred to the surface of a support such as paper or cloth as required, and permanently fixed to the surface of the support using an appropriate fixing means such as heating, pressure, solvent treatment, or overcoating. Alternatively, if it is desired to omit the toner image transfer step, the toner image can be fixed onto the photoconductive layer. There are many known methods for developing a developer. Cascade development method described in U.S. Patent No. 2,618,552; magnetic brush method described in U.S. Pat. No. 2,874,063;
Examples include the touch-down method described in US Pat. No. 2,895,847, and other fur brush development methods. Particularly typical developing methods are known as the cascade method and the magnetic brush method. In the cascade method, non-magnetic particles such as glass beads are used as a developer by attaching fine powder toner to the surface. When this developer cascades over the surface of the photoconductive layer bearing the electrostatic latent image, the toner selectively adheres only to the charged portions of the electrostatic latent image and does not adhere to the uncharged portions, thereby performing development. Further, the magnetic brush method uses magnetic particles such as steel or ferrite as carriers. A developer consisting of toner and a magnetic carrier is held by a magnet, and the magnetic field of the magnet arranges the developer in a brush shape. When this magnetic brush contacts the electrostatic latent image surface on the photoconductive layer, only toner is attracted from the brush to the electrostatic latent image to effect development. Touch-down development is a method in which a support layer, such as a web or sheet, carries developer material to a latent image-bearing surface and develops the electrostatic latent image. The development method described above can be used not only to obtain conventional black and white copies, but also to obtain multicolor copies. That is, first of all, light from an original is passed through a blue filter to expose the photoconductive layer, and the electrostatic latent image formed is developed with yellow toner, which has a complementary color to that of the filter. Then similarly,
Exposure is performed through a green filter and a red filter in alignment with the previous latent image, and the formed latent images are developed with magenta toner and cyan toner, respectively. The three colors of developed toner are sequentially transferred to the same support and a final color copy is obtained with a single fixing. Of course, in this color development method, the order of development can be changed as appropriate, regardless of the order of yellow, magenta, and cyan described above. In color electrophotography, which requires multiple development steps, the color toner should have the following properties: (1) It must be a transparent colored toner that does not interfere with the different colored toner layers below the toner layer. is necessary. (2) Each toner must have sufficient hue and lightness, have a wide range of color mixing properties, and have a wide range of color tone reproduction. (3) When mixing colors, a combination of color toners that produces a deep black color that matches the black image of the original must be selected. (4) Furthermore, the toner must have triboelectric charging properties and fluidity that are favorable for electrophotographic properties. (5) The toner must be shelf-stable without caking or clumping during handling or storage. and so on. but. It is difficult to obtain a conventional color toner that satisfies all of these requirements. For example, as proposed in Japanese Patent Publication No. 49-46951, an appropriate colorant is selected and applied to color electrophotography. However, in most of these, when selecting a colorant that focuses on the toner's hue, spectral reflection characteristics, and color tone reproducibility, it is not possible to impart sufficient electrophotographic characteristics and there are problems with charging characteristics and storage stability. On the other hand, if emphasis is placed on the electrophotographic properties of a toner, the resulting toner will have reduced brightness, poor spectral reflection properties, and narrow color tone reproducibility. In general, in color toners, the tonal characteristics and electrophotographic characteristics of the toner can be said to be two sides of the same coin. In order to overcome these drawbacks, the present inventors, after extensive research, have discovered a color electrophotographic method using a color toner that has a wide range of color tone reproducibility and has favorable electrophotographic properties. That is, an object of the present invention is to provide a novel color electrophotographic method using a toner having preferable spectral reflection characteristics. Another object of the present invention is to provide a color electrophotographic method using a toner that exhibits good color mixing properties when mixing yellow, magenta, and cyan colors and provides a wide range of color tone reproducibility. Another object is to provide a color electrophotographic method using toner having sufficient triboelectric charging properties. Another object of the present invention is to provide a new color electrophotographic method using a toner having good storage stability that can withstand long-term storage. Specifically, the present invention provides CI.Solvent Yellow77
and developing the electrostatic latent image using a yellow toner containing CI.Disperse Yellow164 to obtain a yellow toner image, and developing the electrostatic latent image using a magenta toner containing CI.Solvent Red52 and CI.Solvent Red49 The method comprises a step of developing a latent image to obtain a magenta toner image, and a step of developing the electrostatic latent image using a cyan toner containing CI.Pigment Blue15 to obtain a cyan toner image. The present invention relates to a multicolor electrophotographic method characterized in that a multicolor image is formed by superimposing at least two kinds of toner images among a toner image, a magenta toner image, and a cyan toner image. The color toner in the present invention is easily dispersed or dissolved in the binder resin and has excellent hue and brightness. Using this toner, the spectral reflectance of an image copied in only a single color is as shown in FIGS. 1 to 3. In addition, the spectral reflectance of blue, green, and red images obtained by superimposing two color toners is preferable as shown in FIGS. 4 to 6, and the combination of the three color toners provides A wide range of color reproducibility can be obtained. On the other hand, as a colorant for yellow toner, CI.
If only Solvent Yellow77 is used, CI.
Solvent Yellow 77 has a strong negative triboelectric charging property, so the yellow toner's negative tribostatic charging property becomes too strong and it is easy to charge up.
It becomes difficult for the toner to transfer smoothly from the carrier to the electrostatic latent image, and the image density tends to decrease.
CI is also used as a coloring agent for yellow toner.
When using only Disperse Yellow164,
CI.Disperse Yellow 164 has a strong positive triboelectrification characteristic and is therefore unsuitable as a colorant for yellow toners with negative triboelectrification properties. In the present invention, as described above, CI.Solvent Yellow77 and CI.
By using it in combination with Disperse Yellow 164, the color tone and electrophotographic properties of the yellow toner can be well adjusted. Additionally, CI is used as a coloring agent in magenta toner.
If only Solvent Red52 is used, the negative triboelectricity of the magenta toner will become too strong.
It is easy to charge up and the image density tends to decrease. CI is also used as a coloring agent for magenta toner.
When using only Solvent Red49, CI.
Solvent Red 49 has strong positive triboelectric properties and is therefore unsuitable as a colorant for magenta toner, which has negative triboelectric properties. In the present invention, as described above,
By using CI.Solvent Red52 and CI.Solvent Red49 in combination, the color tone and electrophotographic properties of the magenta toner are well adjusted. The coloring agent is 0.1% by weight or more based on the binder resin,
The content is preferably 30% by weight or less, more preferably 0.5% by weight or more and 20% by weight or less. Examples of the binder resin for the color toner used in the present invention include monopolymers of styrene and substituted products thereof such as polystyrene, polyP-chlorostyrene, and polyvinyltoluene; styrene-P-chlorostyrene copolymers, and styrene-propylene copolymers. polymer,
Styrene-vinyltoluene copolymer, styrene-
Vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methyl methacrylate copolymer , styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-alpha chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinylethyl Ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-
Styrenic copolymers such as isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid copolymer, and styrene-maleic acid ester copolymer; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, Polyvanyl acetate, polyethylene, polypropylene, polyester, polyurethane, polyamide, epoxy resin, polyvinyl butyral, polyacrylic resin, rosin, modified rosin, terpene resin, phenolic resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin,
Parafine wax and the like can be used alone or in combination. As the carrier used in the present invention, either a magnetic material or a non-magnetic material can be used. For example, iron, steel, γ-ferrite Ba
-ferrite, Sr-ferrite and chromium,
Cerium, magnesium oxides, zirconium silicon, and silicon dioxide are mentioned, and these substances are used as particles of 20 to 1000 microns. The toner of the present invention may be mixed with various additives such as a charge control agent, a lubricant, and the like, if necessary. The spectrophotometer used in the spectral reflectance measurement in the present invention is a Beckmann spectrophotometer DK-2A model, and the concentration measurements in the examples were performed using a Kodatsu Kratten filter #47 as a blue filter, a green filter, and a red filter. , #58,
Depends on the Macbeth reflection densitometer (manufactured by Macbeth) using #25. Embodiments of the present invention will be described below with reference to the drawings. First, an example of a color electrophotographic copying machine to which the color electrophotographic developing method according to the present invention is applied will be explained with reference to FIG. The electrostatic latent image formed on the photosensitive drum 1 by an appropriate means is made visible by the developer in the developing device _16-1 , and is applied to the transfer material already held on the transfer drum 19 by the gripper 20.
The developed toner powder image is transferred by the transfer corotron No. 1. Furthermore, the toner powder image developed by the developer in the developing device _16-2 as the second color is also transferred onto the transfer material by the transfer corotron 21, and the same process is performed for the third color. In this manner, the transfer drum 19 rotates a predetermined number of times while holding the transfer material, and images of a predetermined number of colors are multiple-transferred. Example The developer in the first color developing device _16-1 , the developer in the second color developing device 16-2, and the developer in the _third color developing device _16-3 have a structure as shown in the table below. carried out. (All parts in the table indicate parts by weight)

[Table] The toner was manufactured by premixing the toner components shown in Table 1, kneading them with two rolls, passing through a coarse crushing and finely crushing process, and finally a classification process to obtain a color toner with a size of 5 to 20 μm. When this toner was mixed with carrier iron powder (manufactured by Nippon Steel Powder) to obtain an appropriate toner density and printed on an NP-color copier (manufactured by Canon), the electrostatic latent image with a positive charge was changed to a negative one. Good development was achieved with each color toner having a triboelectric charge of 1,000 yen, and very good color tone reproduction was obtained. In addition, as a storage test, the developer was left in a constant temperature bath at 50℃ for about 2 months.
When I reproduced the image using an NP-color copier, I obtained an image that was the same as before storage. From the colored image obtained by the present invention,
FIG. 7 shows the range of tones that can be expressed by the present invention and deviations from the ideal toner by determining the Preucil color circle. In this case, the ideal toner is one-third of the visible spectrum in the three primary color toners using the subtractive color method.
A toner that has uniform high absorption throughout and does not absorb strongly over the entire wavelength range that is absorbed by the other two toners, so as not to cause overlapping absorption bands.In other words, it is a toner that is totally reflected. point to Preucil's color circle is a pie chart as shown in Figure 7, and is often used to determine the color reproduction range of set inks. For example, according to Shigeru Hasegawa, The Science of Printing (edited by the Printing and Publishing Research Institute), it is stated that it can be determined by the following method. The color circle has hues -Y (yellow) and M on the outer circumference.
(magenta), C (cyan) and its secondary color B
(blue), G (green), and R (red) are the scale, and at this position, the outer periphery is the clearest and brightest color, and the turbidity increases toward the center, so the center is black. Then, divide the middle of each into 100 equal parts. The first step in using a color circle is to measure the density of the solid ink area. That is, Y, M, C
Ink B (Ratuten No. 47), G (Ratuten No. 58),
R (Ratten No. 25) was measured using each filter, and calculations were performed as follows, with the highest density of each ink as H, the middle as M, and the lowest as L. Hue error (color tone error) = M-L/H-L x 100
% Grayness (turbidity) = L/H x 100% In the present invention, monochrome yellow, magenta,
Obtain images of cyan, blue, green, and red that are superimposed on two colors, and measure the image density using a Macbeth reflection densitometer to determine hue error and turbidity (Table 2).The image plotted on the color circle is the seventh image. It is a diagram.

【table】 Comparative example 1

[Table] When the toners shown in Table 3 were produced in the same manner as in the examples to make color toners and copied using an NP-color copying machine (manufactured by Canon), the images were inferior to the color tone reproducibility of the examples, and the overall image quality was poor. The color tones were unbalanced. In addition, as in the example, when a storage test was conducted in parallel, it was found that toners other than cyan toner aggregated together, creating so-called clumps, and even when mixed with carrier, sufficient charge could not be maintained. It was not suitable for copying. The Preucil color circle obtained for Comparative Example 1 is shown in the broken line graph in FIG. 7, and the color tone reproducibility range was narrower and less balanced than in the example. Comparative Example 2 100 parts by weight of styrene-acrylic resin, CI.
A yellow toner was prepared using 1.5 parts by weight of Solvent Yellow 77 and 5 parts by weight of a charge control agent, and an image reproduction test was conducted in the same manner as in the above example except that the prepared yellow toner was used. The density of the yellow toner image was low, and the overall color tone was not well balanced. Comparative Example 3 100 parts by weight of styrene-acrylic resin, CI.
A yellow toner was prepared using 1.5 parts by weight of Disperse Yellow 164 and 5 parts by weight of a charge control agent, and an image reproduction test was conducted in the same manner as in the above example except that the prepared yellow toner was used.
Yellow toner images have a lot of fog in non-image areas,
The color tone of the background part of the full-color image was different from the original image. Comparative Example 4 100 parts by weight of styrene-acrylic resin and CI.
A magenta toner was prepared using 1.5 parts by weight of Solvent Red 52, and an image reproduction test was conducted in the same manner as in the above example except that the prepared magenta toner was used. As a result, the density of the magenta toner image was low; The overall color balance was not good. Comparative Example 5 100 parts by weight of styrene-acrylic resin and CI.
A magenta toner was prepared using 1.5 parts by weight of Solvent Red 49, and an image reproduction test was conducted in the same manner as in the above example except that the prepared magenta toner was used. There was a lot of fog in the image area, and the color tone of the background area of the full-color image was different from the original image.

[Brief explanation of the drawing]

FIGS. 1 to 6 are graphs showing the spectral reflectance of the obtained images. Figure 7 is a graph showing Preucil's color circle. FIG. 8 is a schematic cross-sectional view showing an example of a color electrophotographic copying machine to which the color electrophotographic developing method of the present invention is applied. 1...Photosensitive drum. 16...Developing section. 19...
transfer drum. 20... Grizpur. 21...Transcription corotron. 22... Separation claw.

Claims (1)

[Claims] 1 CI.Solvent Yellow77 and CI.Disperse
Developing the electrostatic latent image using a yellow toner containing Yellow164 to obtain a yellow toner image; and developing the electrostatic latent image using a magenta toner containing CI.Solvent Red52 and CI.Solvent Red49. and a step of developing an electrostatic latent image using a cyan toner containing CI.Pigment Blue15 to obtain a cyan toner image. A multicolor electrophotographic method characterized in that a multicolor image is formed by superimposing at least two kinds of toner images among a toner image and a cyan toner image.