JPH04254864A - Electrophotography toner - Google Patents

Abstract

PURPOSE:To obtain a color picture image excellent in color reproducibility and picture image retainability and having a good color tone by containing a specific (J) dye. CONSTITUTION:A dye expressed in a formula is contained. R<1>-R<6> represent substances in the formula as follows: R<1> and R<4>: hydrogen or a methyl group, R<2>: an alkyl group, alkyl halide group, alkanol group, alkyl ether group, or hydroxyl group having a carbon number of 1-8, R<3>: an alkyl group, alkyl halide group, halogen, or hydroxyl group having hydrogen and carbon number 1-8, and R<5> and R<6>: an alkyl group, alkyl halide group, alkanol group, alkoxy group, alkyl ether group, halogen, hydroxyl group, aryl group, aryl halide group, aryl ether group, or hydroxy aryl group having a hydrogen and carbon number of 1-8.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to electrophotographic toners used as developers in electrophotographic copying machines, laser printers, etc., and in particular to process color toners used for forming color images. This is related to toner.

0002

[Prior Art] In general, the electrophotographic method consists of (1) inorganic photoconductive materials such as selenium, amorphous silicon, and zinc oxide; or organic photoconductive materials (often processed into a drum shape) such as diazo compounds and dyes; A photosensitive drum) is first uniformly charged, then an electrostatic latent image is formed by irradiating it with image-modulated light, and powder is attached to the electrostatic latent image using electrostatic force. ■ After transferring the powder onto a base material such as paper or film as necessary,
■It is fixed by methods such as pressurization and heating. Such electrophotographic methods are currently widely used in copying machines, laser printers, and the like.

[0003] Toner in electrophotography is 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. These toners are usually mixed with carrier particles (generally referred to as a carrier) such as iron powder or ferrite, and used as a so-called developer. On the other hand, color toners used to form color images are generally colored in predetermined tones called process colors, that is, toners colored in three subtractive primary colors of yellow, magenta, and cyan.

Toners conventionally used in electrophotographic developers are made by adding colorants, charge control agents, fluidity modifiers, grinding aids, etc. to particles produced by a so-called pulverization method, that is, thermoplastic resins. It has been used after kneading, pulverizing, and further classifying. 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. However, when adopting a method of kneading resin and coloring material before crushing, the coloring material must be able to withstand the high temperatures during kneading with resin. Because dyes change color and fade depending on the temperature during kneading, the reality is that the only coloring materials that can be used are pigments.

[0005]

[Problems to be Solved by the Invention] However, many of the inorganic pigments that have been known so far have safety and health problems, and as a practical matter, toners containing these pigments are commonly used in general copiers, printers, etc. That is impossible. Furthermore, some organic pigments are known to have safety and health problems, and the substances that can actually be used as coloring materials are limited. On the other hand, many substances that do not pose health and safety problems have problems with image retention. That is, many organic coloring materials are susceptible to discoloration and fading due to exposure to ultraviolet rays, and there are few that are particularly satisfactory in terms of color image retention.

Furthermore, when coloring with pigments, the coloring material is 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. That is, since 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 crushed to a submicron size in resin, and in practice, they tend to exist as agglomerated aggregates to some extent in resin, making it difficult to take full advantage of the effects of crushing. I can't.

In view of this situation, the present inventors have conducted extensive research to obtain a toner with excellent color reproducibility, particularly as a color toner, and have finally arrived at the present invention.

[0009]

[Means for Solving the Problems] That is, the present invention provides the general formula

0010

[Chemical formula 2] R1, R4: hydrogen, or methyl group R2: alkyl group having 1 to 8 carbon atoms, halogenated alkyl group, alkanol group, alkyl ether group, or hydroxyl group R3: hydrogen, alkyl group having 1 to 8 carbon atoms,
Halogenated alkyl group, halogen or hydroxyl group R5, R
6: Represented by hydrogen, alkyl group having 1 to 8 carbon atoms, halogenated alkyl group, alkanol group, alkoxy group, alkyl ether group, halogen, hydroxyl group, allyl group, halogenated allyl group, allyl ether group, or hydroxyallyl group This is an electrophotographic toner characterized by containing a dye and being colored.

[0011]

[Action] R1 to R in the dye compound (A) of the present invention
To explain the various definitions shown in 6 by giving examples, examples of the alkyl group having 1 to 8 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, secondary butyl, tertiary butyl, pentyl, hexyl, 2 - Linear or branched alkyl groups such as methylpentyl, heptyl, 2-ethylpentyl, 2-ethylhexyl, octyl, etc. can be mentioned, and examples of the halogenated alkyl group include fluorine, chlorine, or bromine at any position in the alkyl group mentioned above. , substituted with one or more halogens such as iodine. The alkanol includes those in which one or more hydroxyl groups are substituted at any position of the alkyl group described above.

Examples of the alkyl ether group include alkoxyalkyl groups such as methoxymethyl, methoxyethyl, ethoxymethyl, ethoxyethyl, propoxymethyl, propoxyethyl, methoxypropyl, and ethoxypropyl; examples of the alkoxy group include methoxy, ethoxy, Examples include propoxy, butoxy, secondary butoxy, tertiary butoxy, pentyloxy, hexyloxy, heptyloxy, octyloxy and the like. Examples of allyl groups include phenyl, 1-naphthyl, 2-naphthyl, etc.
As the halogenated allyl group, any position in the allyl group as described above is replaced by 1 or 2 by the halogen as described above.
Examples of the above-mentioned substitutions include those substituted with a hydroxyl group, examples of the hydroxyallyl group include those in which any position in the allyl group as described above is substituted with a hydroxyl group, and examples of the allyl ether group include phenoxyphenyl.

Among the above-mentioned dyes, those classified as disperse dyes or oil-soluble dyes are particularly preferred, and particularly preferred among them are C.I. I. SOLVENT VIOL
ET 26 (In the above general formula, R1, R3, R4,
A compound in which R5 and R6 are hydrogen and R2 is a methyl group). The content of the dye in the binder resin is not particularly limited, but is approximately 0.1 to 15% by weight.
, preferably 0.5 to 10% by weight, more preferably 1
It is about 6% by weight. Also, for the purpose of adjusting hue etc.
There is no problem in using other coloring materials together.

In the present invention, the so-called dispersion dyeing method,
That is, a method can be used in which both the dye and the resin particles are dispersed in an aqueous medium and treated at a predetermined temperature. As a method for dispersing the dye in an aqueous medium, it is possible to directly use a commercially available form of a disperse dye, but it is more preferable to use an oil-soluble dye and add the raw material of the dye (conch cake) and a dispersant. An "aqueous dispersion of dye" is used, which is obtained by mixing and pulverizing an aqueous medium, etc. together in a ball mill, sand mill, shaker, etc.

As the dispersant, known dispersants can be used, such as alkyl (benzene) sulfonates or sulfuric ester salts, condensates of naphthalene sulfonates, polystyrene sulfonates, styrene sulfonates and acrylic esters, etc. An acid copolymer or the like can be used.

[0016] The processing temperature during dyeing is difficult to define unconditionally since it varies depending on the dye used, but it is generally in the range from the glass transition point of the resin to 150°C. There is no problem in dyeing by applying pressure to increase the boiling point of water. In the present invention, it is particularly preferable to carry out dyeing at a temperature approximately 40° C. higher than the glass transition point of the resin. The ratio of the aqueous medium to the resin particles during dyeing is not particularly limited, but in order to increase the dyeing efficiency, the ratio of the resin particles to the entire aqueous dispersion should be 20% by weight.
It is preferable to set it as above.

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 polyol and polycarboxylic acid, and even more preferable is a polyester resin containing an ionic group. It is.

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, but does not exclude those using oxycarboxylic acid.

The ionic groups in the resin, which is the main component, include anionic groups such as carboxyl groups, sulfonic acid groups, sulfuric acid groups, phosphoric acid groups, or salts thereof (hydrogen salts, metal salts), or A cationic group such as a primary to tertiary amino group, preferably a carboxyl group, an ammonium carboxylate base, a sulfonic acid group, or an alkali metal sulfonate base.

Examples of the sulfonic acid metal group-containing compound copolymerizable with the resin include sulfoterephthalic acid, 5-sulfoisophthalic acid, 4-sulfophthalic acid, 4-sulfonaphthalene-2,7-dicarboxylic acid, 5-(4- Examples include metal salts such as sulfophenoxy)isophthalic acid. Examples of metal salts include alkali metals such as Li, Na, and K, Mg,
Examples include salts of alkaline earth metals such as Ca, and heavy metals such as Cu and Fe, with Na salt being particularly preferred. When the resin is a polyester resin, it is preferable to use 5-sodium sulfoisophthalic acid. The content of these ionic groups is not particularly limited, but
A range of approximately 0.02 to 0.5 equivalent/1000g 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, and even more preferably 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 low have a tendency to aggregate during handling or storage, and fluidity may significantly deteriorate, particularly during long-term storage. On the other hand, if the softening point is high, fixing performance will be impaired. Furthermore, 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 of the toner is preferably 2 to 15 μm, and when the average particle diameter is D, particles having a particle diameter in the range of 0.5D to 2.0D account for 70% of the total weight. % or more, and it is particularly preferable that particles with a sphericity of 0.8 or more account for 80% or more (by number) of substantially spherical particles. (This is the ratio of the diameter to the major axis.) 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.

[0024] Toner obtained by the conventional method of mixing a pigment with a resin and pulverizing and classifying it cannot obtain a toner having uniform charging characteristics because the content and distribution of the pigment contained in each toner particle varies. . On the other hand, in the toner obtained by the dispersion dyeing method, the content of the dye contained in each toner particle is uniform, and the distribution within the particle is also uniform. Therefore, the resulting toner has very uniform charging characteristics.

Incidentally, electrophotographic toners are often blended with a charge control agent to stabilize charge, but ordinary charge control agents are colored, which poses a problem when used in color toners in particular. There are many things. On the other hand, the dye used in the present invention has a hue as a process color,
Not only does it have excellent chroma and light fastness, but it also acts as a charge control agent to stabilize the triboelectric properties of the dyed resin, so there is no need to use a charge control agent.

Due to the above-mentioned effects, the toner of the present invention is uniform with no variation among the individual particles constituting the toner.
Moreover, it has highly stable charging characteristics and is also excellent in hue, saturation, and light fastness as a process color.

[0027]

[Examples] Examples will be described below, but the present invention is not limited to these in any way. The physical properties of the resins shown in Examples and Comparative Examples were measured by the following method.・Melting point, glass transition point The heating rate was 10 using a differential scanning calorimeter (manufactured by Shimadzu Corporation).
Measured in °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 In an autoclave equipped with a thermometer and a stirrer,
Dimethyl terephthalate 81
5 parts by weight dimethyl isophthalate
320 parts by weight ethylene glycol 491
Part by weight Neopentyl glycol
549 parts by weight Zinc acetate

0.6 parts by weight was charged and heated at 120 to 230°C for 120 minutes to perform transesterification reaction. Then, 5-sodium sulfoisophthalic acid 40
Part by weight was added, the reaction was continued for 60 minutes at 220-230°C, and the temperature was further raised to 250°C, and the system pressure was reduced to 1-1
As a result of continuing the reaction for 60 minutes at 0 mmHg, a copolymerized polyester resin (A1) was obtained. The obtained copolymerized polyester resin (A1) had a molecular weight of 2500, and a sulfonic acid metal base content of 116 milliequivalents/1000 g. The amount of sulfonic acid metal base was determined by measuring the sulfur concentration in the copolyester resin.

Further, as a result of NMR analysis, the composition of the copolymerized polyester resin (A1) revealed that the acid component was terephthalic acid.
70.0 mol% isophthalic acid
27.
5 mol% 5-sodium sulfoisophthalic acid 2.5 mol%, alcohol component is ethylene glycol
48.0 mol% Neopentyl glycol 52.0 mol%
Met.

Preparation of aqueous microdispersion 34 parts by weight of the obtained copolyester resin (A1),
After dissolving 10 parts by weight of butyl cellosolve at 110°C, 56 parts of water at 80°C was added to obtain an aqueous microdispersion of copolyester resin with a particle size of about 0.1 μm. Furthermore, the obtained aqueous microdispersion was placed in a distillation flask,
Distillation was carried out until the distillate temperature reached 100°C, and after cooling, water was added to make the solid content concentration 38% (B1).

Production of aqueous dispersion of resin particles 1 (combination granulation) 270 parts by weight of the copolymerized polyester aqueous dispersion (B1) was placed in a four-necked 1-liter separable flask equipped with a thermometer, condenser, and stirring blade. (Solid content: 38% by weight) and 8 parts by weight of acrylic acid/sodium styrene sulfonate copolymer [Toughtic AD (manufactured by Nihon Exlan Kogyo)] were added, and the temperature was raised to 70° C. with stirring. Next, 26 parts by weight of deionized water in which 1.55 parts by weight of sodium chloride was dissolved was added dropwise over 40 minutes, and stirring was continued at 70° C. for an additional 180 minutes. As a result, the particles of the copolymer with a submicron-order particle size that existed in the copolymerized polyester aqueous dispersion grew, and the average particle size D became 6.3.
Substantially spherical polyester particles were obtained in which the occupancy of particles having a particle diameter in the range of μm, 0.5 D to 2 D was 82% by weight. The obtained polyester particles are thoroughly filtered and washed with deionized water, and the final solid content concentration is 20% by weight.
An aqueous dispersion (C1) was obtained. Preparation of disperse dye As a dye (Example 1), C.I. I. SOLVENT
VIOLET 26

[0032]

[Chemical formula 3] In (Example 2)

[0033]

[C4] In (Example 3)

[0034]

[Formula 5] Using each raw material, 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, and defoamer. It was charged into a sand mill at a mixing ratio of 65.9 parts by weight of ionized water, and pulverized and dispersed for about 3 hours until the average particle size was 0.
．． A dye dispersion of 2 μm was obtained. Moreover, as (Comparative Example 1), dye C. I. DISPERSE RED 15

[0035]

[C6] A dye dispersion was obtained in the same manner.

100 parts by weight of an aqueous dispersion (C1) of dyed resin particles,
3 parts by weight of the dye (conch cake equivalent) was placed in a stainless steel pot of a dyeing tester "Mini Color" manufactured by Texam Giken, and the temperature was raised from room temperature to 130°C at a rate of 3°C/min. After holding for 60 minutes, the mixture was 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 tested using an electrophotographic method to obtain an average film thickness of 7 μm.
It was fixed on paper so that it became m, and was used as a sample for light resistance evaluation. Light resistance was evaluated using a fade meter, and the degree of discoloration after 20 hours of exposure to a carbon arc lamp (CIEEL
Evaluation was made using the color difference ΔE) in the AB coordinate system. A colorimeter CR-210 (manufactured by Minolta) was used to measure the chromaticity coordinates. A gradation image was copied onto a transparent film using the same obtained toner, and was observed and evaluated using an overhead projector (OHP). The results are shown in Table 1. Also, charging characteristics,
No particular problems were observed in the humidity dependence of fluid properties, insulation properties, fixing properties, sharp melt properties, offset printing resistance, etc.

(Comparative Example 2) Using 95 parts by weight of the copolymerized polyester resin (A1) obtained in Example 1 and 5 parts by weight of the azo magenta pigment (C.I. PIGMENT RED 48), these were mixed in a ball mill. After premixing,
The mixtures were melted and mixed in a roll mill, pulverized and classified in a pulverizer to obtain a colored toner having an average particle size of 7.4 μm.

The obtained toner was fixed on paper using the electrophotographic method in the same manner as in the examples so as to have an average film thickness of 7 μm, and was used as a sample for light resistance evaluation. Using the same obtained toner, a gradation image was copied onto a transparent film and observed and evaluated using an OHP. The results are shown in Table 1.

[0040]

[Table 1]

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 prepare a developer. 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.

When the toners obtained in Examples 1 to 3 were used, no significant difference was observed between the images at the beginning of the test and the images at the end of the test. In the toner obtained in Comparative Example 1, some "fading" was observed after 8000 sheets. 4000 in the toner obtained in Comparative Example 2
After 7,000 sheets, "fogging" occurred, and after 7,000 sheets, both "fogging" and "fading" increased, and the image quality deteriorated significantly. This is due to variations in the charging characteristics of individual toner particles and uneven consumption of toner, and as the number of copies increases, toner particles with poor charging characteristics remain in the copying machine. be.

[0043]

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

Claims (1)

[Claims] 1. An electrophotographic toner comprising a dye represented by the following general formula. [Formula 1] R1, R4: hydrogen, or methyl group R2: alkyl group having 1 to 8 carbon atoms, halogenated alkyl group, alkanol group, alkyl ether group, or hydroxyl group R3: hydrogen, alkyl group having 1 to 8 carbon atoms,
Halogenated alkyl group, halogen or hydroxyl group R5, R
6: Hydrogen, alkyl group having 1 to 8 carbon atoms, halogenated alkyl group, alkanol group, alkoxy group, alkyl ether group, halogen, hydroxyl group, allyl group, halogenated allyl group, allyl ether group, or hydroxyallyl group