JPH06282117A - Magenta liquid developer for electrostatic photography - Google Patents

Abstract

PURPOSE:To provide a magenta color liquid developer suitable for developing colors in a color picture image, especially, a developer suitable for color electrostatic photography by overlap development, so that color tones can be freely designed according to the picture output system such as the order of colors or to the color tones of other liquid developers except for the magenta color, and that reproducibility of secondary colors by overlapping of colors can be improved. CONSTITUTION:The liquid developer has dispersion of toner particles in a carrier liquid, and the toner particle essentially consists of a coloring agent and a resin. The coloring agent consists of at least Pigment Violet 19 and Pigment Red 122. More preferably, the mixture of these pigments are subjected to flashing treatment with ethylene/vinylacetate copolymers and polyethylene wax having 60-130 deg.C softening point and <=1.0KOHmg/g acid value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magenta liquid developer for electrostatic photography, in particular, electrostatic latent images formed on an electrophotographic photosensitive member or an electrostatic recording material to electrostatically adhere toner particles to a visible image. The present invention relates to a magenta liquid developer for electrostatography used in a process of superimposing color.

[0002]

2. Description of the Related Art In order to obtain a full-color image by electrophotography or electrostatic recording, an electrostatic latent image is formed on an electrophotographic photosensitive member or electrostatic recording paper by a conventional method, and a primary color in accordance with the destructive color mixing method is used. It can be obtained by electrostatically adhering toner particles in a liquid developer to form a visible image and color superposition. Liquid developer used in this method, cyan, magenta, and each pigment for yellow rosin, linseed oil, soybean oil, modified alkyd resin, styrene-butadiene resin,
It is obtained by pulverizing and dispersing in a carrier liquid having a high insulating and low dielectric constant such as an aliphatic hydrocarbon together with a resin such as an acrylic resin or fats and oils. In color electrostatic photography, it is desired that the liquid developer has various performances in order to superimpose the toners of the respective primary colors as described above, and the greatest requirement is that good color reproduction can be obtained.

As a pigment generally used for magenta, Carmine 6B is used because of its vivid purple color tone and excellent transparency.
The azo lake pigment represented by No. 1 is used, but the toner obtained using the azo lake pigment has a drawback that background fog occurs. The reason for this is not completely clear, but since there is a hydrophilic group such as a carboxyl group in the structure of the azo lake pigment, aggregation of toner particles easily occurs in the carrier liquid that is a non-aqueous system, and it is also difficult to It is considered that the polarity of the toner particles is unclear due to the presence of such acidic groups.

As another method for improving the color tone of a magenta monochromatic image, a rhodamine-based pigment and a quinacridone-based pigment are used as pigments (JP-A-56-75660).
No.) was also tried, and a monochromatic image having a color tone close to the ideal magenta color was obtained. However, in the process of expressing a secondary color by color superposition, a magenta color that is more reddish or bluish with respect to the ideal color may be required depending on the color superposition order and the tone of other colors. In the above-mentioned pigment mixture system, the adjustment range of the color tone (particularly the hue angle) is narrow, so it is difficult to deal with such a process.
Further, among these pigment-based pigments, the rhodamine-based pigments are generally inferior in light resistance, which causes a problem that the color tone of an image changes with time.

On the contrary, as a method for eliminating background fog, Naphthol AS-based water-insoluble azo pigment, Naphthol A
The use of S-benzimidazolone pigments and β-naphthol pigments as toner pigments has also been investigated (Japanese Patent Laid-Open Publication No. 6-58242).
No. 4-2065), a liquid developer using these pigments alone improved the background fog and showed no other abnormalities, but the color tone shifted to the red side compared to the ideal magenta color. Further, since the color tone cannot be set arbitrarily and continuously, good color reproducibility could not be obtained even in red and blue due to color overlapping depending on the selection of liquid developers of other colors. Further, in the liquid developer obtained by the method described above, that is, by dispersing the pigment together with the resin in the carrier liquid, the pigment is not dispersed into the primary particles, so that the transparency is poor and a cause of poor color reproducibility. Has become.

Therefore, as a manufacturing means for improving the transparency, as disclosed in JP-A-57-34720 and 57-19376, wax and pigment are dispersed in a heating carrier liquid and the pigment is rapidly cooled. Wax treatment and dispersing it in a carrier liquid together with a resin, or as shown in JP-A-57-201248, the wax and pigment are kneaded and spray-granulated by a spray dryer, and the resin is At the same time, it has been proposed to disperse it in a carrier liquid. However, these proposals are still not fully satisfactory. In the method of treating wax and pigment and dispersing them in a carrier liquid together with a resin, the familiarity between the wax and the pigment is not so good that the toner is not dispersed up to the primary particles and the transparency is insufficient. there were.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a magenta liquid developer suitable for color reproduction of color images, especially
Overlapping development type that can improve the color reproducibility of secondary colors by overlapping colors by arbitrarily setting the color tones according to the characteristics of the image output system such as the color overlapping order and the color tones of liquid developers other than magenta. To provide a magenta liquid developer suitable for color electrophotography, and to provide a magenta liquid developer whose color tone is linearly changed according to the ratio of pigments. Especially. A further object is to achieve the above object without causing the above-mentioned problems such as background fog and color tone change due to the problem of light resistance.

[0008]

A first aspect of the present invention is a liquid developer comprising a carrier liquid and toner particles containing a colorant and a resin as main components, the colorant being at least P.
igment Violet 19 and Pigment
It is characterized by comprising Red122. In the second aspect of the present invention, the coloring agent is Pigment Violet 19
Pigment Red 122 is a colorant obtained by flushing a polyethylene wax having a softening point of 60 to 130 ° C. and an acid value of 1.0 KOHmg / g or less and an ethylene / vinyl acetate copolymer. In the third aspect of the present invention, the coloring agent is Pigment Vio.
It is characterized in that it is composed of a mixed system of let19 and Pigment Red 122, and that at least some of these pigments are in solid solution with each other.

By the way, the inventors of the present invention have conducted extensive research in order to solve the above-mentioned problems. As a result, by selecting a specific pigment combination as a colorant, the characteristics of the image output system such as the color superimposing order and magenta. It was found that the color reproducibility of the secondary color due to color superposition can be improved by arbitrarily setting the color tone according to the color tone of the liquid developer other than the color, and these specific pigments are integrated by solid solution. Or it was found that the color tone can be changed linearly according to the ratio of the pigments by subjecting these specific pigments to a flushing treatment with a combination of a specific wax and a resin, and the present invention has been completed. It is a thing.

The present invention will be described in more detail below. P
igment Violet 19 and Pigment
Although both Red122 are classified as quinacridone pigments, the color tones when used individually are considerably different, the former being pink magenta and the latter being strongly bluish magenta. It is difficult to reproduce the color when used alone because they are far from the ideal magenta in color tone. System) has excellent reproducibility of color images, and in particular, toner particles mainly composed of a colorant and a resin dispersed in a carrier liquid can be electrostatically attached to an electrostatic latent image. When used in the process of visualizing and superimposing colors, it is possible to set color tones according to the characteristics of the image output system such as the order of color superimposition and the color tones of liquid developers other than magenta.
The color reproducibility of the next color can be improved.

Pigment Violet 19 and Pi
The blending ratio with gment Red 122 is 2: 8 to 8: 2.
Is the best. When the content exceeds this range, the color tone as magenta is not sufficient, and the color tone of red and blue becomes different from the ideal color, so this range is particularly preferable.

Next, the colorant subjected to the flushing process will be described. The above-described pigment flushing process is performed as follows. First, a pigment or a pigment-containing paste is put together with a resin (the above-mentioned polyethylene wax and ethylene / vinyl acetate copolymer) solution in a kneader called a flasher and mixed well. In this process, the water existing around the pigment is replaced by the resin solution. This is taken out from the kneader, the aqueous layer is discarded, the solvent is removed by drying, and the obtained lump is crushed. In the present invention, this is called a "flushing colorant". In addition, a means for removing water and a solvent by reducing the pressure while kneading with a kneader may be used. The flushing treatment is known to have very good dispersion, since a water-containing paste can be used as a material and the treatment can be performed while kneading with a kneader.

The liquid developer obtained by using the flushed pigment as a colorant can be set in any color tone without causing background fog, and its hue angle is linearly changed depending on the ratio of pigments. Therefore, it can be specified by calculation from the hue angle of two different pigment ratios. Moreover, since the pigment is dispersed close to the primary particles by the flushing treatment, the transparency is also excellent. As a result, it is possible to improve the color reproducibility when a color image is obtained by color overlapping development.

As a polyethylene wax used in the flushing treatment of the pigment, when the acid value is large, it is difficult to be positively charged, the image density is not increased, and the dispersion stability is deteriorated. In addition, when the softening point is low, stability at high temperature storage is poor,
On the other hand, if the softening point is high, the fixability will be poor. Therefore, in the present invention, the softening point is 60 to 130 ° C. and the acid value is 1.0.
It is preferred to use a polyethylene wax which is KOH mg / g or less.

Examples of commercially available polyethylene waxes used in the present invention include the following. Manufacturer Product name Softening point Acid value Sanyo Kasei Sun Wax 131P 108 0 151P 107 0 161P 111 0 165P 107 0 171P 105 0 Mitsui Oil High Wax 100P 121 0 110P 113 0 220MP 113 1.0 BASF WAX A 98-108 AM -6 95 to 10 20 Allied AC polyethylene 1702 850 Chemical 6 & 6A 106 0 9 & 9A 117 0 Hoechst Hoechst wax PA-520 103 to 107 0 PA-130 119 to 1250

Examples of commercially available ethylene / vinyl acetate copolymers used in the flushing treatment include the following. Manufacturer Trade name Vinegar% Mitsui DuPont Evaflex 45X 46 Chemical 〃 150 33 〃 220 28 28 〃 310 25 〃 410 19 〃 550 14 Sumitomo Chemical Sumitate PB10 10 〃 11 R 28 A 11 〃 HA 20 A

The polyethylene wax and the ethylene / vinyl acetate copolymer are used in a weight ratio of 90:10.
A range of 40:60 is preferred. If the amount of polyethylene wax is more than the above range, the dispersion will be poor and the sharpness of the image will be reduced. On the other hand, when the ethylene / vinyl acetate copolymer exceeds the above range, the image density and the adhesiveness deteriorate, so the above range is preferable.

Next, a colorant obtained by solid solution of two kinds of pigments will be described. The solid solution of the pigment can be performed by a known method such as a thermal method in which pigment mixing, calcination, and pulverization are repeated several times, a mechanical method applying a mechanochemical reaction, or a combination thereof. . However, when the thermal method is used, the pigment may be decomposed depending on the temperature, so that it is necessary to adjust the atmosphere during the calcination and to pressurize it in some cases. In addition, during the solution treatment, an auxiliary agent for accelerating the solution may be added as necessary within a range that does not affect the color tone and various physical properties of the pigment. A liquid developer obtained by using this solid solution pigment as a colorant can have an arbitrary color tone, and its hue angle can be linearly changed depending on the ratio of the solid solution pigment. It can be specified by calculation from the hue angle of the solid solution pigment, and as a result, the color reproducibility can be improved, and the color tone can be easily determined.

Pigmen obtained as described above
t Violet19 and Pigment Red
In order to prepare a liquid developer using a colorant mixed with 122, or subjected to a solution treatment or a flushing treatment, the colorant, the binder and the carrier liquid are mixed with an attritor,
The toner may be kneaded and dispersed by a ball mill, a sand mill or the like to obtain a concentrated toner, and if necessary, this may be diluted with a similar carrier liquid. Regarding the mixing ratio of the colorant and the others, in the case of the mixed colorant and the solution-treated colorant, the binder (solid content) 1 to 50 parts by weight with respect to 1 to 10 parts by weight of the colorant.
It is suitable to use 40 parts by weight of the carrier liquid and 40 to 100 parts by weight of the carrier liquid, and in the case of the colorant subjected to the flushing treatment,
5 to 20 parts by weight of the colorant, 5 to 5 parts by weight of the binder (solid content)
50 parts by weight and 30 to 90 parts by weight of carrier liquid are suitable. Further, if necessary, a charge control agent can be added to the concentrated toner and / or at the time of dilution in order to adjust the charge amount to a desired value.

In the present invention, the binder is alkyd resin, rosin-modified phenol formaldehyde resin,
Polyhydric alcohol ester of hydrogenated rosin, polyacrylic or polymethacrylic ester resin, styrene resin,
A chlorinated rubber or the like is used, and it is particularly effective to use a mixed resin of the following resin (A) and resin (B).

Resin (A) At least one of styrene / butadiene resin or vinyltoluene / butadiene resin and the following general formula (1)
A non-aqueous resin obtained by polymerizing at least one type of monomer selected from

[Chemical 1] In the formula, R is —H or —CH ₃ , X is —COOCnH ₂ n + 1, —
Represents OCOCnH ₂ n + 1, n is an integer of 6-20.

Resin (B) Lauryl methacrylate / glycidyl methacrylate / methyl methacrylate (8 /
1/1) Copolymer To manufacture the resin (A), for example, a styrene / butadiene copolymer is dissolved in a non-aqueous solvent, and then the general formula (1) is used.
The monomer of azobisisobutyronitrile (A
The polymerization reaction may be carried out at a temperature of about 60 to 120 ° C. in the presence of a polymerization initiator such as IBN) or benzoyl peroxide (BPO) which initiates the polymerization at a relatively low temperature.

The monomer represented by the general formula (1) is a monomer which can be a solvated component even after polymerization, and specific examples thereof include lauryl methacrylate, lauryl acrylate stearyl methacrylate, stearyl acrylate, 2-ethylhexyl methacrylate and 2-ethylhexyl. Acrylate, dodecyl methacrylate, dodecyl acrylate, hexyl methacrylate, hexyl acrylate, octyl methacrylate, octyl acrylate, cetyl methacrylate, cesyl acrylate,
There are vinyl laurate, vinyl stearate, nonyl methacrylate, nonyl acrylate, decyl methacrylate, decyl acrylate, cyclohexyl methacrylate, cyclohexyl acrylate, and the like. Examples of the polymerization initiator used in the present invention include AIBN and BP described above.
In addition to O, phenylazotriphenylmethane, lauroyl peroxide, t-butyl peroxide and the like can be mentioned.

The carrier liquid used in the developing solution of the present invention is preferably an aliphatic hydrocarbon or its derivative. Specific examples thereof include paraffinic or isoparaffinic hydrocarbons (Esso H, Isopar G, Isopar L, Isopar K, No. 6 Solvesso 100, etc.), ligroin, n-hexane, n-heptane, Iso-octane, n-octane, carbon tetrachloride, trichlorotrifluoroethane, cyclohexane and the like are used alone or in combination of two or more.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. All parts shown below are based on weight.

Claims (5)

[Claims] 1. A liquid developer obtained by dispersing toner particles containing a colorant and a resin as a main component in a carrier liquid, wherein the colorant comprises at least Pigment Violet 19 and Pigment Red 122. Magenta liquid developer. 2. A magenta liquid developing device for use in a process in which toner particles mainly composed of a colorant and a resin dispersed in a carrier liquid are electrostatically attached to an electrostatic latent image to form a visible image for color superposition. Agent, the coloring agent is at least Pig.
ment Violet 19 and Pigment R
A magenta liquid developer for electrostatic photography, which comprises ed122. 3. The coloring agent is at least Pigment V.
The iolet 19 and the Pigment Red 122 are flushed with a polyethylene wax and an ethylene vinyl acetate copolymer having a softening point of 60 to 130 degrees and an acid value of 1.0 KOHmg / g or less. Magenta liquid developer for electrostatic photography. 4. The magenta liquid developer for electrostatic photography according to claim 1, wherein a part of the colorants are in solid solution with each other. 5. Pigment Vio in the colorant
The magenta liquid developer for electrostatic photography according to claim 1 or 2, wherein the mixing ratio of let19 and Pigment Red 122 is 2: 8 to 8: 2.