JPH04235570A - Toner for electrophotography - Google Patents

Abstract

PURPOSE:To obtain color images of good tone which are excellent in color reproducibility and image holding property by putting a specific dye in a toner for coloration. CONSTITUTION:A dye expressed by the formula is contained in a toner for electrophotgraphy. In the formula, R1 represents hydrogen or a methyl group and R2, R3 and R6 represent groups selected among an alkyl group of carbon number 1 to 8, an alkyl halide group, an alkanol group, an alkoxyl group, alkyl ether, halogen and a hydroxyl group, and R4 and R5 represent groups selected among hydrogen, an alkyl group of carbon number 1 to 8, an alkyl halide group, an alkanol group, an alkoxyl group, an alkyl ether group, halogen, a hydroxyl group, an allyl group of carbon number 6 to 15, an allyl halide group, an allyl ether group and a hydroxyallyl group.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to an electrophotographic copying machine,
The present invention relates to an electrophotographic toner used as a developer in laser printers, etc. More specifically, the present invention relates to process color toners used for forming color images, and particularly relates to colored toners.

0002

[Prior Art] Electrophotography generally refers to photoconductive materials (often processed into a drum shape) made of inorganic materials such as selenium, amorphous silicon, and zinc oxide, or organic materials such as diazo compounds and dyes. : A photosensitive drum) is first uniformly charged, then irradiated with image-modulated light to form an electrostatic latent image, and developed by attaching powder to the electrostatic latent image using electrostatic force. After the powder is transferred onto a material such as paper or film as necessary, it is fixed by applying pressure, heating, or the like. Electrophotographic methods are currently widely used in copying machines, laser printers, and the like.

In electrophotography, a powder that develops an electrostatic latent image on a photosensitive drum and is ultimately transferred to a base material such as paper or film to form an image is called a toner. These toners usually contain carrier particles (such as iron powder or ferrite).
: carrier) and used as a so-called developer. Color toners used to form color images are generally colored in predetermined tones called process colors, that is, toners colored in the three subtractive primary colors of yellow, magenta, and cyan. Conventionally, toners used in electrophotographic developers include:
Particles have been used that are produced by a so-called pulverization method, in which a coloring agent, a charge control agent, a fluidity modifier, a pulverization aid, etc. are added to a thermoplastic resin, the mixture is kneaded, and then pulverized and further classified. As a method for coloring electrophotographic toner using these pulverization methods, a method in which a coloring material is kneaded with a resin and then pulverized is mainly used. When a resin and a coloring material are kneaded in advance before pulverization, the coloring material needs to withstand the high temperatures during kneading with the resin. Since many dyes change color or fade depending on the temperature during kneading, the usable coloring materials are limited to pigments.

0004

[Problems to be Solved by the Invention] Many of the inorganic pigments known in the past have safety and health problems, and as a practical matter, it is difficult to use toners containing these in general copiers, printers, etc. It's impossible. Some organic pigments also have safety and health problems, and the ones that can actually be used as coloring materials are limited. Even if there are no health and safety issues, there are many that have problems with image retention. That is, many organic coloring materials undergo discoloration and fading due to exposure to ultraviolet rays, and there are few that are particularly satisfactory in terms of retention of color art materials. When coloring with pigments, the coloring material is merely dispersed in the binder resin of the toner, resulting in poor transparency. Therefore, the color reproducibility when a plurality of colors are overlapped is insufficient, and the reproduction range of intermediate colors becomes narrow. Further, the influence of transparency is particularly noticeable when an image is formed on a transparent sheet for an overhead projector. In other words, because the transparency of the toner layer is poor, the projected image has a dim and muddy tone, and the reproduction of not only intermediate colors but also primary colors is inhibited. The problem of transparency can be improved to some extent by reducing the particle size of the pigment particles to below the wavelength of light, that is, to the submicron level. However, it is difficult to grind pigments to submicron size, and the cost of coloring materials increases significantly. Furthermore, it is difficult to uniformly disperse pigments that have been pulverized to a submicron size in a resin, and as a practical matter, they exist as agglomerated aggregates to some extent in the resin, making it impossible to fully utilize the effect of pulverization. In view of this situation, the inventors of the present invention have conducted extensive research to obtain a toner with particularly excellent color reproducibility as a color toner, and as a result, have arrived at the following invention.

[0005]

[Means for Solving the Problems] That is, the present invention is an electrophotographic toner characterized in that it contains a specific dye shown in Chemical Formula 1 and is colored. The dye used in the present invention is generally classified as a disperse dye or an oil-soluble dye. The dye preferably used in the present invention is C.I. I. DISPERSE RED
60 (R1:R2:R3:R4:R5, R6: hydrogen). The content of the dye in the binder resin is not particularly limited, but is approximately 0.1 to 15.0, preferably 0.5 to 10.0, more preferably 1.0 to 6.0.
It is about % by weight. Further, in order to adjust the hue, etc., other coloring materials may be used together.

[0006] In the present invention, as a method for obtaining the toner dyed with the above-described dye, a so-called dispersion dyeing method may be used, in which the dye and resin particles are dispersed in an aqueous medium and treated at a predetermined temperature. can. As a method for dispersing the dye in an aqueous medium, a commercially available form of a disperse dye may be used directly, but it is more preferable to use a dye base (conch cake) when using an oil-soluble dye. , dispersant, aqueous medium and ball mill,
An "aqueous dye dispersion" obtained by mixing and pulverizing with a sand mill, shaker, etc. can be used. Known dispersants can be used as the dispersant, such as alkyl (benzene) sulfonates or sulfuric ester salts, condensates of naphthalene sulfonates, polystyrene sulfonates, copolymers of styrene sulfonates and acrylic acid. It is possible to use things such as merging. Although it is difficult to define the processing temperature for the dye since it varies depending on the dye used, it is generally in the range from the glass transition point of the resin to 150°C. Dyeing may be carried out under pressure to increase the boiling point of water. In the present invention, in particular, the temperature is 40°C further than the glass transition point of the resin.
It is preferable to carry out dyeing at a moderately high temperature. The ratio of the water diameter medium and the dispersed resin particles when dyeing is not particularly limited, but in order to increase the dyeing efficiency, it is preferable that the resin particles account for 20% by weight or more with respect to the entire water diameter dispersion.

In the present invention, the resin that is the main component of the particles is not particularly limited, but styrene/acrylic resins, epoxy resins, polyester resins, etc. can be used. In the present invention, it is preferable that the toner binder resin is an ionic group-containing resin. In addition, from the viewpoint of adhesion to paper, fixability, transparency, etc., it is preferable to use a resin whose main component is a polyester resin consisting of a polyol and a polycarboxylic acid, and more preferably a polyester resin containing an ionic group. . As the polyester resin, both saturated polyester resin and unsaturated polyester resin can be used. The polyester resin in the present invention mainly consists of a dicarboxylic acid resin and a glycol component.

The ionic groups contained in the resin, which is the main component, include carboxyl groups, sulfonic acid groups, sulfate groups,
Anionic groups such as phosphoric acid groups or salts thereof (hydrogen salts, metal salts), or cationic groups such as primary to tertiary amine groups, preferably carboxyl groups, carboxylic acid ammonium bases, Sulfonic acid group, sulfonic acid alkali metal base. Examples of sulfonic acid metal base-containing compounds that can be copolymerized with resin include sulfoterephthalic acid,
Examples include metal salts of 5-sulfoisophthalic acid, 4-sulfophthalic acid, 4-sulfonaphthalene-2,7-dicarboxylic acid, and 5[4-sulfophenoxy]isophthalic acid. Metal salts include Li, Na, K, Mg, Ca, and C.
Examples include salts such as u, Fe, etc., and particularly preferred is Na salt. When the resin is a polyester resin, 5
-Preference is given to using sodium sulfoisophthalic acid. The content of these ionic groups is not particularly limited, but is approximately 0.02 to 0.5 equivalent/1000
A value within the range of g is appropriate.

The glass transition point of the resin used in the present invention is preferably 40°C or higher, more preferably 50°C or higher,
Furthermore, it is preferable that the temperature is 60°C or higher. When the glass transition point is lower than this, there is a tendency to aggregate during handling or storage, which may cause problems in storage stability. Furthermore, the softening point of the resin used in the present invention is 8
The temperature is preferably in the range of 0 to 150°C. Toners in which the softening temperature of the resin is kept lower than this have a tendency to aggregate during handling or storage, and fluidity may deteriorate significantly, especially during long-term storage. If the softening point is higher than this, fixing performance will be impaired. Further, since it is necessary to heat the fixing roll to a high temperature, the material of the fixing roll and the material of the base material to be copied are limited. In the present invention, the average particle diameter D of the toner is 2 to
It is preferably 15 μm, and 0.5D to 2.0
It is preferable that particles having a particle size range of D account for 70% by weight or more of the total weight, and particles having a sphericity of 0.8 or more account for 80% by weight or more.
It is preferable that substantially spherical particles account for at least (number)%. If the shape, average particle size, and particle size distribution of the particles are not within the predetermined ranges, problems may occur in color image reproducibility, particularly in intermediate colors.

[0010] Toners obtained by the conventional method of mixing a pigment with a resin and pulverizing and classifying the resin have variations in the content and distribution of the pigment contained in each toner particle (exposed on the surface, near the surface, inside the particle). It is not possible to obtain a toner with uniform charging characteristics. In the toner obtained by the dispersion dyeing method of the present invention, the content of dye contained in each toner particle is uniform, and the distribution within the particle is also the same. Therefore, the resulting toner has very uniform charging characteristics. Now, in electrophotographic toners, a charge control agent is used to stabilize the charge. Usually, charge control agents are colored, and many of them have problems, especially when used in color toners. The dye used in the present invention not only has excellent hue, saturation, and light fastness as a process color, but also functions as a charge control agent to stabilize the triboelectric properties of the dyed resin. . As a result of the above work, the toner of the present invention has uniform and highly stable charging characteristics with no variation among the individual particles constituting the toner, and also has excellent hue, saturation, and light fastness as a process color. It becomes something.

[0011]

[Examples] The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to these in any way. In addition, the physical properties of the resin in Examples and Comparative Examples were measured by the following method.・Melting point, glass transition point A heating rate of 1 was measured using a differential scanning calorimeter (manufactured by Shimadzu Corporation).
Measurement was performed at 0°C/min. - Softening point was measured according to JIS K2351.・Number average molecular weight (vapor pressure method) Measured using a molecular weight measuring device (manufactured by Hitachi, Ltd.). (Synthesis of polyester resin) Dimethyl terephthalate in an autoclave equipped with a thermometer and a stirrer.
815 parts by weight, dimethyl isophthalate 320 parts by weight, ethylene glycol
491 parts by weight, neopentyl glycol 549
parts by weight, and zinc acetate
0.6 parts by weight was charged and heated at 120 to 230°C for 120 minutes to perform transesterification reaction. Next, 40 parts by weight of 5-sodium sulfoisophthalic acid was added to give 220 to 23 parts by weight.
The reaction was continued for 60 minutes at 0°C, and then the temperature was raised to 250°C, and the reaction was continued for 60 minutes at a system pressure of 1 to 10 mmHg, to obtain a copolymerized polyester resin (A1). The molecular weight of the obtained copolymerized polyester resin (A1) is 2
500, sulfonic acid metal base is 116 m equivalent/1000
It was g. The amount of sulfonic acid metal base was determined by measuring the sulfur concentration in the copolyester resin. In addition, as a result of NMR analysis, the composition of the copolymerized polyester resin (A1) was found to be terephthalic acid as an acid component.
70.0 MOL%
isophthalic acid
27.5 MOL%
5-Sodium sulfoisophthalic acid 2.5MO
L% Alcohol component: Ethylene glycol
48.0MOL% Neopentyl glycol 52.
It was 0MOL%.

(Production of polyester particles) 34 parts by weight of the obtained copolymerized polyester resin (A1) and 10 parts by weight of butyl cellosolve were dissolved at 110°C, and then 5 parts by weight of water at 80°C were dissolved.
6 parts were added to obtain an aqueous microdispersion (B1) of copolyester resin having a particle size of about 0.1 μm. Furthermore, the obtained aqueous microdispersion was placed in a distillation flask and distilled until the distillate temperature reached 100°C, and after cooling, water was added to make the solid content concentration 38% (B2). The obtained copolymerized polyester aqueous dispersion (B
2) 270 parts by weight (solid content 38% by weight), acrylic acid/
Sodium styrene sulfonate copolymer (Toughtic A
8 parts by weight of D (manufactured by Nippon Exlan Kogyo) were added, and the temperature was raised to 70°C while stirring. Next, sodium chloride 1.5
26 parts by weight of deionized water in which 5 parts by weight had been dissolved was added dropwise over 40 minutes, and stirring was continued for an additional 180 minutes while maintaining the temperature at 70°C. As a result, the copolymer with a submicron-order particle size that was present in the copolymerized polyester aqueous dispersion underwent particle growth, and the average particle size D was 6.3 μm and 0.5D.
Polyester particles were obtained with an occupancy of 82% of particles having particle diameters in the range of ~2D. The obtained polyester particles were thoroughly filtered and washed with deionized water to finally obtain an aqueous dispersion (C1) with a solid content concentration of 20% by weight.

(Example 1) As a dye, C.I. I. DIS
Using the raw material of PERSE RED 60, that is, conch cake, 20 parts by weight of dye conch cake, 14 parts by weight of dispersant Mignol 802 [manufactured by Ipposha Yushi Kogyo], 0.1 part by weight of silicone antifoaming agent, 65 parts by weight of deionized water. The mixture was charged into a sand mill at a mixing ratio of .9 parts by weight, and pulverized and dispersed for about 3 hours to obtain a dye dispersion with an average particle size of 0.2 μm.

100 parts by weight of the obtained aqueous dispersion of resin particles (C1) and 3 parts by weight of the dye dispersion (conch cake equivalent) were placed in a stainless steel pot of a dyeing tester "Mini Color" manufactured by Texam Giken, and heated from room temperature. The temperature was raised to 130°C at a heating rate of 3°C/min, held at 130°C for 60 minutes, and then cooled to room temperature to obtain dyed particles. The obtained dyed particles were filtered, washed, and dried with a spray dryer to obtain a colored toner.

The obtained toner was fixed on paper using an electrophotographic method so that the average film thickness was 7 μm, and a sample for light resistance evaluation was prepared. For light resistance evaluation, use a fade meter.
The degree of discoloration (color difference ΔE in CIELAB coordinate system) after exposure to a carbon arc lamp for 20 hours was evaluated. A chromaticity meter CR-210 [manufactured by Minolta] was used to measure the chromaticity coordinates. Using the same obtained toner, a gradation image was copied onto a transparent film and observed and evaluated using an overhead projector. The hue is a clear bluish red, △E is 2, and the overhead projector (OH
The image of P) was clear. Also, charging characteristics, flow characteristics,
No particular problems were observed in the humidity dependence of insulation properties, fixing properties, sharp melt properties, anti-offset properties, etc.

(Example 2) The same procedure as in Example 1 was carried out except that the dye represented by the following chemical formula 2 was used.

[0017]

[Chemical Formula 2] The hue was a clear bluish red, ΔE was 2, and the OHP image was clear.

(Example 3) The same procedure as in Example 1 was carried out except that the dye represented by the following chemical formula 3 was used.

[0019]

embedded image The hue was a clear reddish purple, the ΔE was 3, and the OHP image was clear.

(Comparative Example 1) A dye represented by the following chemical formula 4 (
C. I. It was carried out in the same manner as in Example 1 except that DISPERSE RED 22) was used.

[0021]

[Chemical formula 4] The hue is clear bluish red, △E is 14, OHP
The image was clear.

(Comparative Example 2) 95 parts by weight of the copolyester resin (A1) obtained in Example 1 and an azo magenta pigment (C.I. PIGMENT RED 48)
5 parts by weight are premixed in a ball mill, melt-mixed in a roll mill, pulverized in a pulverizer, and classified to have an average particle size of 7.
A colored toner of 4 μm was obtained. This colored toner was used in Example 1.
It was evaluated in the same way. The hue was a clear bluish red, and the ΔE was 2, but the OHP image was unclear.

50 parts by weight of the toner obtained in each of the Examples and Comparative Examples and 1000 parts by weight of ferrite carrier F-100 (manufactured by Powder Tech) were placed in a ball mill and stirred for about 15 minutes to form a developer. did. Using the obtained developer, a continuous copying test of 10,000 sheets was conducted using an analog type copying machine having an amorphous silicon photosensitive drum. Examples 1-3. When the toner obtained by the method was used, no significant difference was observed between the images at the beginning of the test and the images at the end of the test. Comparative example 1. In the toner obtained in 1, some "fading" was observed after 8,000 sheets were printed. Comparative example 2. With the toner obtained in
After that, "fogging" and "fading" increased, and the image quality deteriorated significantly. This is because toner particles with poor charging characteristics remain in the copying machine as the number of copies increases because the charging characteristics of individual toner particles vary and the amount of toner consumed is uneven.

[0024]

Effects of the Invention As described above, the toner according to the present invention provides color images with excellent color reproducibility and image retention, and has good tone, and the individual particles constituting the toner are extremely It has stable and uniform charging characteristics.

[C5]

Claims (1)

[Claims] 1. An electrophotographic toner comprising a dye represented by the following chemical formula 1. [Chemical 1] In the above chemical formula 1, R1 represents hydrogen or a methyl group,
R2, R3, and R6 represent a group selected from an alkyl group having 1 to 8 carbon atoms, a halogenated alkyl group, an alkanol group, an alkoxy group, an alkyl ether, a halogen, and a hydroxyl group, and R4 and R5 are hydrogen and a group having 1 carbon number. 8 alkyl group, halogenated alkyl group, alkanol group, alkoxy group, alkyl ether group, halogen, hydroxyl group, and carbon number 6
represents a group selected from 15 allyl groups, halogenated allyl groups, allyl ether groups, and hydroxyallyl groups.