JPH04242266A - Toner for electrophotography - Google Patents

Abstract

PURPOSE:To provide a magenta toner for electrophotography having superior image reproducibility and image retentivity. CONSTITUTION:C.I. Disperse Red 92 or a deriv. thereof as a dye is dispersed in an aq. medium and particles of the resin binder of a toner are dispersed in the medium and dyed with the dye to obtain a magenta colored color toner.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic toner used as a developer in electrophotographic copying machines, laser printers, and the like. More specifically, the present invention relates to process color toners used for forming color images, and particularly to toners colored magenta.

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 base material such as paper or film as necessary, it is fixed by a method such as pressurization or heating. 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. Conventionally, toners used in electrophotographic developers are made by adding colorants, charge control agents, fluidity modifiers, grinding aids, etc. to thermoplastic resins, kneading them, pulverizing them, and then classifying them. Particles made by milling methods have been used.

Color toners used to form color images generally have predetermined tones called process colors, ie, yellow, magenta, cyan,
Toners colored in the three primary colors of subtractive color mixing are used. As a method for coloring electrophotographic toner magenta by these pulverization methods, a method is mainly used in which a coloring material is kneaded into a resin and then pulverized. 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.

[0005]

[Problems to be Solved by the Invention] Many of the conventionally known inorganic pigments have health and safety problems, and as a practical matter, toners containing these pigments are used in general copiers, printers, etc. That is impossible. There are also some organic pigments that have health and safety issues.
There are limits to what can actually be used as coloring materials. 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 color image retention.

[0006] In coloring with pigments, transparency is poor because the coloring material is simply dispersed in the binder resin of the toner. 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 pulverize 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.

[0007]

[Means for Solving the Problems] In view of the above-mentioned circumstances, the inventors of the present invention have carried out intensive research to obtain a magenta toner that has particularly excellent color reproducibility as a color toner, and as a result, they have arrived at the following invention. That is, the present invention provides C. I. DISP
An electrophotographic toner characterized by containing a dye classified as ERSE RED92 and its derivatives.
It is. The dyes used in the present invention are generally classified as disperse dyes or oil-soluble dyes.

In the present invention, VI is used for hue adjustment.
OLET dyes can be blended. VIOLET
As the dye, it is preferable to use dyes classified as disperse dyes and oil-soluble dyes. Dyes that can be used include C. I. DISPERSE VIOLET
11, 17, 26, 31, 35, 36, 43, 61
, 84, C. I. SOLVENT VIOLET
26, 32, 36, etc. can be exemplified. Furthermore, other coloring materials may be used in combination to adjust the hue and the like.

The content of the dye in the binder resin is not particularly limited, but is approximately 0.1 to 15.0, preferably 0.4 to 10.0, more preferably 0.8 to 15.0.
It is about 4.0% by weight.

In the present invention, to obtain the toner dyed with the above-described dye, a so-called dispersion dyeing method is used, in which the dye and resin particles are dispersed in an aqueous medium and treated at a predetermined temperature. I can do it. 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) or when using an oil-soluble dye. ), dispersant, and aqueous medium in a 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.

[0011] 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. Dyeing may be carried out under pressure to increase the boiling point of water. In the present invention, it is particularly preferable to carry out the dyeing at a temperature approximately 40° C. higher than the glass transition point of the resin.

[0012] The ratio of the aqueous medium to the dispersed resin particles during dyeing is not particularly limited, but in order to improve the dyeing efficiency, it is preferable that the resin particles account for 20% by weight or more based on the entire aqueous dispersion.

[0013] The resin that is the main component of the particles in the present invention 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 a polyester resin containing an ionic group. is more preferable.

As the polyester resin, both saturated polyester resin and unsaturated polyester resin can be used. The polyester resin in the present invention is
It mainly consists of a dicarboxylic acid resin and a glycol component.

Examples of dicarboxylic acid components include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, and 1,5-naphthalic acid; aromatic dicarboxylic acids such as p-oxybenzoic acid and p-(hydroxyethoxy)benzoic acid; aliphatic dicarboxylic acids such as succinic acid, adipic acid, azelaic acid, sebacic acid, and dodecanedicarboxylic acid; Saturated aliphatic and alicyclic dicarboxylic acids can be used. As the acid component, a small amount of tri- and tetracarboxylic acids such as trimellitic acid, trimesic acid, and pyromellitic acid may be included if necessary.

Examples of the glycol component include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6 -hexanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, 2,2,4-trimethyl-1,3-pentanediol, 1,4-cyclohexanedimethanol, spiroglycol , 1,4-phenylene glycol, 1,4-
Diols such as ethylene oxide adducts of phenylene glycol, dimethylolheptane, tricyclodecanediol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, bisphenol
Ethylene oxide adducts and propylene oxide adducts of Formula A, ethylene oxide adducts and propylene oxide adducts of hydrogenated bisphenol A, and the like can be used.

In addition to these, small amounts of triols and tetraols such as trimethylol ethane, trimethylolpropane, glycerin, and pentaelthritol may be included, if necessary. The polyester polyol may also include lactone-based polyester polyols obtained by ring-opening polymerization of lactones such as ε-caprolactone.

Among polyester resins, it is preferable to use polyester resins containing 80 mol % or more of terephthalic acid and/or isophthalic acid as the acid component, especially when coloring is carried out with dyes.

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 the sulfonic acid metal group-containing compound copolymerizable with the resin include sulfoterephthalic acid, 5-sulfoisophthalic acid, 4-sulfophthalic acid, 4-sulfonaphthalene-2,7dicarboxylic acid, 5[4-sulfophenoxy ]
Examples include metal salts such as isophthalic acid. Examples of metal salts include salts of Li, Na, K, Mg, Ca, Cu, Fe, etc., and particularly preferred is Na salt. 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 is approximately 0.02 to 0.5 equivalent/
A range of 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,
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 tend 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
is preferably 2 to 15 μm, and 0.5D to
It is preferable that particles with a particle size range of 2.0D account for 70% by weight or more of the whole, and it is further preferable that particles with a sphericity of 0.8 or more account for 80% (by number) or more of substantially spherical particles. . If the particle shape, average particle diameter, and particle size distribution are not within the predetermined ranges, problems may occur in color image reproducibility, particularly in intermediate color reproducibility. (Sphericity is the ratio of the short axis to the long axis obtained from the projection of the particle.)

In the present invention, when an ionic group-containing resin is used as the resin, the ionic group-containing resin is stably microdispersed in an aqueous medium, and the microdispersed particles are plasticized. The amount of ions existing on the surface and near the surface (which has the function of stabilizing microdispersed particles in an aqueous medium) is
By means of reducing it under uniformly controlled conditions,
An aqueous dispersion of ionic group-containing resin particles obtained by disrupting the stable state of microdispersed particles in a medium and combining the microdispersed particles can be used. In the present invention, the term "microdispersion" refers to a state in which it is dispersed in water by forming stable micelles through the formation of an electric double layer, and generally refers to dispersion in an emulsion or colloidal state. It is something to do.

Examples of methods for plasticizing the resin include a method in which the temperature of the system is raised above the glass transition temperature or softening temperature, a method using a solvent, a plasticizer, etc.

Means for reducing the amount of ions existing on the surface of microdispersed particles and in the vicinity of the surface under uniformly controlled conditions include: - A compound containing a counter ion to an ionic group contained in the resin. - A method of blocking ionic groups by adding into the system, - A method of cutting off ionic groups contained in the resin, - pH
Examples include a method of adjusting the degree of dissociation of an ionic group by scanning, and a method of adding an electrolyte.

[0028] In toner for electrophotography, the triboelectric charging property of the toner is very important. Generally, coloring materials (dyes, pigments) have amino groups, nitro groups, azo groups, etc.
It is known that when blended into resin and dyed, it affects the triboelectric properties of the resin. Toners obtained by the conventional method of mixing pigments with resin and pulverizing and classifying each toner are
It is not possible to obtain a toner with uniform charging characteristics because the content and distribution (exposed on the surface, near the surface, and inside the particle) of the pigment contained in the particles vary.

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 furthermore, the distribution within the particle is also the same. Therefore, the resulting toner has very uniform charging characteristics.

A charge control agent is used in toner for electrophotography to stabilize charge. Usually, charge control agents are colored, and many of them are problematic, 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. be.

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

[0032]

[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 and glass transition point Measured using a differential scanning calorimeter (manufactured by Shimadzu Corporation) at a heating rate of 10° 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 was added 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. Then, 5-sodium sulfoisophthalic acid 40
After adding parts by weight, the reaction was continued at 220-230°C for 60 minutes, and the temperature was further raised to 250°C, and the pressure of the system was increased to 1-230°C.
As a result of continuing the reaction for 60 minutes at 10 mmHg, a copolymerized polyester resin (A1) was obtained. The molecular weight of the obtained copolymerized polyester resin (A1) was 2500, and the amount of sulfonic acid metal base was 116 m equivalent/1000 g. The amount of sulfonic acid metal base was determined by measuring the sulfur concentration of the copolyester resin. In addition, copolymerized polyester resin (
As a result of NMR analysis, the composition of A1) was found to be terephthalic acid as an acid component.
70.0 MOL%
isophthalic acid
27.5 MOL% 5-sodium sulfoisophthalic acid 2.5 MOL%,
Ethylene glycol as an alcohol component
48.0MOL% Neopentyl glycol 52
．． It was 0MOL%.

(Preparation of aqueous microdispersion) 34 parts by weight of the copolymerized polyester resin (A1) obtained 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 of copolyester resin having a particle size of about 0.1 μm. Furthermore, the obtained aqueous microdispersion was placed in a distillation flask, and the distillation temperature was 10
Distillation was carried out until the temperature reached 0°C, and after cooling, water was added to make the solid content concentration 38%. (B1)

(Production of aqueous dispersion of resin particles) Thermometer,
In a four-necked 1-liter separable flask equipped with a condenser and stirring blade, 270 parts by weight of the obtained copolyester aqueous dispersion (B1) (solid content 38% by weight) and acrylic acid/sodium styrene sulfonate were added. 8 parts by weight of a polymer (Toughtic AD [manufactured by Nihon Exlan Kogyo Co., Ltd.]) was added, and the temperature was raised to 70° C. while 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 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 grew into particles, and the average particle size D became 6.3 μm.
, substantially spherical polyester particles were obtained in which the occupancy rate of particles having a particle diameter in the range of 0.5D to 2D was 82% by weight. 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.

(Preparation of disperse dye) As the dye, (1
) C. I. DISPERSE RED 92 (T1
(2)C. I. DISPERSE RED
92 and C. I. DISPE
Mixture of RSE VIOLET 26 (for T2) (6/4 by weight) (3) C. I. DISPERSE RED 9
2 and C. I. DISPERSE
VIOLET 35 mixture (for T3)
(7/3 weight ratio), that is, conch cake, was used to dye conch cake.
20 parts by weight of dispersant Mignol 802 [manufactured by Ipposha Yushi Kogyo] 14 parts by weight, 0.1 part by weight of silicone antifoaming agent,
Pour into a sand mill at a mixing ratio of 65.9 parts by weight of deionized water, grind and disperse for about 3 hours, and each particle has an average particle size of 0.2μ.
A dye dispersion of m was obtained.

(Dyeing) An aqueous dispersion of the obtained resin particles (
C1) 100 parts by weight, dye (conch cake equivalent) 1
．． 5 parts by weight of dyeing tester "Minicolor" manufactured by Texam Giken
The mixture was placed in a stainless steel pot, heated from room temperature 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 and washed, and dried in a spray dryer to obtain colored toners (T1), (T2), and (T3).

(Evaluation) 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. Light resistance was evaluated using a fade meter based on the degree of discoloration (color difference ΔE in CIELAB coordinate system) after being exposed to a carbon arc lamp for 20 hours. Colorimeter CR-210 is used to measure chromaticity coordinates.
[Manufactured by Minolta] was used. ΔE is 1 for T1, 3 for T2,
T3 was 2. (This ΔE value is the average value of n=5, rounded off to the nearest whole number. The same applies hereinafter.)

Using the obtained toner, a gradation image was copied onto a transparent film and observed and evaluated by five subjects using an overhead projector. All of T1, T2, and T3 were clear images (images from an overhead projector). T1 had a clear bluish red color, and T2 and T3 had a clear reddish-purple color.

50 parts by weight of the obtained toner and ferrite carrier F-100 [manufactured by Powder Tech Co., Ltd.] 1000
parts by weight 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. (T1) (T2) (T3)
Regardless of which toner 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. In addition, no particular problems were observed in charging properties, flow properties, humidity dependence such as insulation properties, fixing properties, sharp melt properties, anti-offset properties, etc.

[0041]

[Comparative Example 1] Using the aqueous dispersion (C1) of copolymerized polyester resin particles obtained in Example, C
．． I. A colored toner (T4) was obtained using DISPERSE RED 15 in the same manner as in the examples below. The light resistance of the obtained toner was evaluated using the same method as in the examples.
Image evaluation was performed using an overhead projector. ΔE was 13, the hue was a clear bluish red, and the overhead image was also clear.

[0042]

[Comparative Example 2] 95 parts by weight of the copolymerized polyester resin (A1) obtained in Example 1 and magenta pigment C. I. P
IGMENT RED 48, 5 parts by weight were premixed in a ball mill, melted and mixed in a roll mill, and pulverized and classified in a pulverizer to obtain a colored toner (T5) with an average particle size of 7.2 μm. I got it. Toner obtained in the same manner as in Example
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. Using the similarly obtained toner, a gradation image was copied onto a transparency film and observed and evaluated using an overhead projector. The hue was a clear bluish red, and the ΔE was 1, but
The image from the overhead projector was unclear. 50 parts by weight of the obtained toner and ferrite carrier F
-100 [manufactured by Powder Tech Co., Ltd.] and 1000 parts by weight 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. In the continuous copying test, "fogging" occurred after 5,000 copies, and after 8,000 copies, "fogging" and "fading" both 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. It is.

[0043]

[Effects of the Invention] As described above, the toner according to the present invention has excellent humidity dependence such as charging characteristics, flow characteristics, and insulation properties.
It also provides images with excellent fixing properties, sharp melt properties, anti-offset properties, etc., and particularly in color images, which has excellent color reproducibility and image retention properties and has good tone.

Claims (1)

[Claims] [Claim 1] C. I. DISPERSE RED
1. An electrophotographic toner comprising a dye classified as 92 and its derivatives.