JPH05119523A - Electrophotographic toner - Google Patents

Abstract

PURPOSE:To obtain an electrophotographic toner excellent in picture image characteristics and resistance to vinyl chloride plasticizer by using a polyester resin having specified or higher specific gravity for a binder resin. CONSTITUTION:A polyester resin having >1.3 specific gravity is used as the main structural component of the binder resin. This polyester resin essentially consists of polyvalent carboxylic acids and polyhydric alcohols. As for the polyvalent carboxylic acids, terephthalic acid, isophthalic acid, etc., are used. As for polyhydric alcohols, aliphatic diols and/or alicyclic diols are preferably used. The aliphatic diols are preferably ethylene glycol, propylene glycohol, 2, 3-butan diol. As for alicyclic diols, tricyclodecane dimethanol, cyclohexane diol, cyclohexane dimethanol are preferable. With this toner, picture images obtd. are free from damages even when these piacture images are stored for a long time with a eraser rubber provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner used as a developer in electrophotographic copying machines, laser printers, facsimiles and the like.

[0002]

2. Description of the Related Art Generally, the electrophotographic method is an inorganic type such as selenium, amorphous silicon, zinc oxide, or
An organic photoconductive substance (often processed into a drum shape) such as a diazo compound or a dye (in most cases, a photosensitive drum) is first charged uniformly and then irradiated with image-modulated light for static charging. An electrostatic latent image is formed, and the electrostatic latent image is developed by adhering the powder to the electrostatic latent image, and the powder is transferred onto a base material such as paper or film, if necessary, and then pressure is applied.
It is fixed by a method such as heating. The electrophotographic system is currently widely used in copiers, laser printers, facsimiles and the like.

A powder that develops an electrostatic latent image on a photosensitive drum in an electrophotographic system and is finally transferred to a base material such as paper or film to form an image is called a toner. These toners are usually mixed with carrier particles (: carrier) such as glass beads, iron powder, and ferrite, and used as a so-called developer. As a toner used in a developer for electrophotography, a colorant, a charge control agent, a fluidity modifier, a pulverization auxiliary agent, etc. are added to a binder resin, and the mixture is kneaded and then pulverized.
Particles produced by a so-called pulverization method for further classification are used. As the binder resin, a styrene / acrylic copolymer resin has been mainly used, but in recent years, a polyester resin having an excellent low-temperature fixing property tends to be used with the increase in speed of electrophotography and coloration. Conventionally used polyester resins are mainly unsaturated polyester resins obtained by polycondensation of aliphatic unsaturated carboxylic acids such as fumaric acid and maleic acid with dioles having a bisphenol structure.

[0004]

In the toner using the conventional styrene / acrylic copolymer resin and unsaturated polyester resin, the plasticizer used in the vinyl chloride resin, the eraser, etc. easily migrates, If the copied image is saved in a transparent file, sandwiched between desk mats, left with an eraser on it, or left with an eraser residue attached, it may be affected by vinyl chloride or the plasticizer contained in the eraser. There is a problem that the image is damaged, or the transparent sheet and the eraser are contaminated.

[0005]

In view of the above situation, the inventors of the present invention have earnestly studied to obtain an electrophotographic toner having excellent plasticizer resistance, and have arrived at the next invention. That is, the present invention is a toner for electrophotography, which uses a polyester resin having a specific gravity of 1.3 or more as a main constituent component of a binder resin.

The polyester resin in the present invention is mainly obtained from polyvalent carboxylic acids and polyhydric alcohols. Examples of the polycarboxylic acids include terephthalic acid, isophthalic acid, orthophthalic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, aromatic dicarboxylic acids such as diphenic acid, and p-oxybenzoic acid. , Aromatic oxycarboxylic acids such as p- (hydroxyethoxy) benzoic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid and other aliphatic dicarboxylic acids, fumaric acid, maleic acid, itaconic acid, Hexahydrophthalic acid, tetrahydrophthalic acid, and other unsaturated aliphatic and alicyclic dicarboxylic acids, and other polyvalent carboxylic acids such as trimellitic acid, trimesic acid, and pyromellitic acid. The polyvalent carboxylic acid and the like can be used. In the present invention, the polycarboxylic acid is preferably 40 to 95 mol% of terephthalic acid, 5 to 60 mol% of isophthalic acid, and the sum of terephthalic acid and isophthalic acid is preferably 80 mol% or more. The content of terephthalic acid is 60 ~ 95mol%, and more preferably 70 ~ 90mol%
Is more preferable, and the total sum of terephthalic acid and isophthalic acid is more preferably 90 mol% or more. When the content of terephthalic acid is less than the above range, the quality of the copied image may be impaired by the plasticizer contained in the eraser, vinyl chloride and the like. Further, the polyvalent carboxylic acid preferably contains 0.5 to 8 mol% of a trivalent or higher polyvalent carboxylic acid such as trimellitic acid, trimesic acid and pyromellitic acid.

The polyhydric alcohols include ethylene glycol, propylene glycol, 1,3-propanediol, 2,3-butanediol and 1,4-butanediol.
1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol
, Dipropylene glycol, 2,2,4-trimethyl-1,3-pentanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, spiroglycol, paraxyleneglycol -, Meta-xylene glycol, ortho-xylene glycol, 1,4-phenylene glycol, ethylene oxide adduct of 1,4-phenylene glycol, polyethylene glycol, polypropylene glycol, polytetra Methylene glycol
Such as diol, bisphenol A, bisphenol A
Ethylene oxide adduct and propylene oxide adduct, hydrogenated bisphenol A, ethylene oxide adduct and hydrogenated bisphenol A ethylene oxide and propylene oxide adduct, trimethylolethane, trimethylol-
As propane, glycerin, pentaerythritol, and other triols, tetraols, and polyester polyols, lactone-based polyester polyols and the like obtained by ring-opening polymerization of lactones such as ε-caprolactone It can be illustrated.

In the present invention, it is preferable to use an aliphatic diol and / or an alicyclic diol as the polyvalent alcohol. It is preferable to use ethylene glycol, propylene glycol or 2,3-butanediol as the aliphatic diols. As the alicyclic diols, it is preferable to use tricyclodecane dimethanol, cyclohexane diol, or cyclohexane dimethanol. In the present invention, the content of ethylene glycol and / or propylene glycol as the polyhydric alcohol is preferably 70 mol% or more, more preferably 80 mol% or more, still more preferably 90 mol% or more.

The glass transition point of the polyester resin in the present invention is 55 ° C. or higher, preferably 60 ° C. or higher, more preferably 63 ° C. or higher, and even more preferably 65 ° C. or higher. If the glass transition point is lower than this, blocking tends to occur during handling or storage, which may cause storage stability problems. The softening point of the polyester resin in the present invention is in the range of 80 to 150 ° C. In a toner having a resin softening temperature lower than this, there is a tendency for the toner to aggregate during handling or storage, and the fluidity may be greatly deteriorated particularly during long-term storage. If the softening point is higher than this, the fixability is 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 substrate to be copied are limited.

The polyester resin according to the present invention permits use of a trivalent or higher polyvalent carboxylic acid component and / or a combination of trivalent or higher polyvalent alcohols, but its purpose is to broaden the molecular weight distribution of the polyester resin. The purpose is not to gel the resin. The gelation of the resin makes it particularly difficult to take out the resin from the polyester polymerization apparatus, resulting in a marked decrease in productivity. In the present invention, it is necessary that there is substantially no gelation, and more specifically, the chloroform insoluble content is 0.5% by weight or less, preferably 0.25% by weight or less. The acid value of the polyester resin in the present invention is preferably 3 mgKOH / g or less,
1 mg KOH / g is more preferable, still 0.5 mg
It is preferable to adjust so as not to exceed KOH / g.

The polyester resin of the present invention has a specific gravity of 1.3.
It is essential that the above is satisfied, and 1.31 or more, and further 1.32 or more are more preferable. Further, the polyester resin of the present invention preferably does not dissolve in a single solvent such as methyl ethyl ketone and toluene or tetrahydrofuran at room temperature. If the specific gravity and the solubility in a solvent are low, the PVC plasticizer resistance may decrease. The solubility in a solvent can be adjusted mainly by the copolymerization ratio of terephthalic acid and isophthalic acid or the composition ratio of alicyclic polyvalent alcohol and aliphatic polyvalent alcohol.

In the present invention, 0.1 to 6 mol% of an ester-forming carboxylic acid containing a sulfonic acid group and / or a salt thereof may be used as the carboxylic acid component. This component is used for the purpose of improving the charging stability of the toner. Examples of the polycarboxylic acid containing a metal sulfonate copolymerizable with polyester include sulfoterephthalic acid and 5-
Examples thereof include sulfoisophthalic acid, 4-sulfophthalic acid, 4-sulfonaphthalene-2,7 dicarboxylic acid, 5 [4-sulfophenoxy] isophthalic acid, and salts thereof. In addition, by using a metal salt of sulfobenzoic acid together, a metal sulfonate base can be introduced at the polymer terminal. Examples of salts include ammonium ions, salts of Li, Na, K, Mg, Ca, Cu, Fe and the like, and particularly preferred are K salt or Na salt.

In the present invention, the polyester resin may contain a component having an ionic group other than the group of the sulfonic acid or its salt for the purpose of improving the charge stability of the toner. As the ionic group, an anionic group such as a carboxyl group, a sulfuric acid group, a phosphoric acid group, a phosphonic acid group, a phosphinic acid group or an ammonium salt or a metal salt thereof, or a cation such as a primary to tertiary amine group And a carboxyl group or an ammonium carboxylate group can be preferably used. It is preferable that these ionic groups are contained in a form copolymerized with polyester or introduced into the polymer terminal. The carboxyl group can be added to the polymer terminal by introducing a polyvalent carboxylic acid such as trimellitic acid into the system at the final stage of polymerization of polyester. Further, by neutralizing this with ammonia, sodium hydroxide or the like, it can be exchanged for a carboxylate group. The content of these ionic groups, including the groups of sulfonic acid groups and / or salts thereof, is 10 to 10 with respect to the polyester resin.
00 m equivalent / 1000 g, preferably 20 to 500 m equivalent / 1000 g, more preferably 50 to 200 m equivalent /
It is 1000 g. When the content of the ionic group is less than the predetermined amount, sufficient charge stability cannot be obtained. Further, if the ionic group content is unnecessarily large, it may be particularly susceptible to humidity, and long-term storage stability may be deteriorated.

When the polyester resin of the present invention contains an ionic group, it exhibits water dispersibility. in this case,
An ionic group-containing polyester resin stably micro-dispersed in an aqueous medium, in a plasticized state of the micro-dispersed particles, the surface of the micro-dispersed particles, and the micro-dispersed fine particles present near the surface are stabilized in the aqueous medium. The ionic group-containing polyester is formed by disrupting the stable state of the micro-dispersed particles in the medium by means of reducing the amount of ions that have the function of causing the micro-dispersed particles to be reduced under a uniformly controlled condition. Particles can be obtained.

As means for reducing the amount of ions present on the surface of the micro-dispersed particles and in the vicinity of the surface, the ionic groups contained in the polyester resin can be released by photolysis, thermal decomposition, hydrolysis or the like, Control of dissociation degree by scanning of temperature, pH, etc., blocking of ionic group by counterion, and destruction of electric double layer by addition of electrolyte can be used. In the present invention, a reactive monomer having a counterionic group is added to the system, and the ionic group is blocked using a polyion complex formed by polymerizing the counterionic group-containing monomer. It is preferable to use a method or a method in which an ionic group introduced into a polymer chain through an ester bond or the like or a monomer portion having an ionic group as a part thereof is cleaved off in combination with a perhydrolysis catalyst. be able to. The polyester particles thus obtained have an average particle diameter D of 1 to 15 μm.
And 70% by weight of the whole in the range of 0.5D to 2.0D
It has a particle size distribution in which the above particles exist, and the sphericity (minor axis /
Particles having a major axis of 0.9 or more account for 80% by weight or more of the entire particles and become substantially spherical particles.

The electrophotographic toner of the present invention has good fastness to light even when it is colored with a dye. Therefore, a dye that is more excellent in transparency, hue, and saturation than a pigment can be used as a coloring material. As the dye, it is preferable to use "a dye insoluble in water at room temperature". These are generally classified as disperse dyes or oil-soluble dyes. More specifically, C.I. I. Disperse Yellow 198 C.I. I. Disperse Yellow 42 C.I. I. Disperse Red 92 C.I. I. Disperse Violet 26 C.I. I. Disperse Violet 35 C.I. I. Disperse Blue 60 C.I. I. At least one dye selected from Disperse Blue 87 is preferably used. These are particularly excellent in light fastness, sublimation fastness, hue and saturation, and are preferable as three primary colors for process color. Other known dyes and pigments may be used in combination for fine adjustment of hue, but the amount used should be minimized. However, when it is necessary to realize the black toner with dyes, it is not necessary to stick to these dyes. These dyes may be directly used in the form of dyes which are commercially available as disperse dyes for dyeing textiles, and those which are not available in such forms include dye bases (conquer cakes), dispersants, Aqueous medium is mixed with a ball mill, sand mill, shaker, etc. to obtain a dye
It is possible to use a form in which the ki is further finely pulverized and finely dispersed. As the dispersant, a condensate of naphthalene sulfonate, polystyrene sulfonate, a copolymer of styrene sulfonate and acrylic acid, or the like can be used.

As a method for incorporating the dye into the polyester resin, a high temperature dispersion dyeing method can be used. The method of directly kneading the dye base material into the resin is not preferable in consideration of the damage of the dye due to heating. Since the polyester resin of the present invention exhibits good stable dispersibility in water due to the action of ionic groups, it is possible to carry out dyeing at a high concentration while maintaining the particulate state. Carbon black or the like may be used to obtain a black toner. As the carbon black, thermal black, acetylene black, channel black, furnace black, lamp black and the like can be used. In the electrophotographic toner of the present invention, a charge control agent may be used in combination so as to give a predetermined charge amount. In the toner of the present invention, a fluidity modifier such as alumina fine particles or silica fine particles may be added. The toner used without being mixed with the carrier particles (: carrier), that is, the toner in the case of a one-component developer is required to have magnetism. In such a case, iron, cobalt, nickel, an alloy mainly containing them, or an oxide such as ferrite may be contained, if necessary.

The electrophotographic toner of the present invention has good image characteristics, fixing characteristics, blocking resistance, storage stability, plasticizer resistance, and charge stability. This realizes a low melt viscosity at high temperature in a state where the polyester resin used in the present invention maintains a relatively high glass transition temperature, and further has an affinity with a plasticizer contained in a vinyl chloride resin, an eraser or the like. This is because the plasticizer does not migrate to the toner resin because it is low, and because the toner resin itself has a certain degree of crystallinity, the bleeding of the coloring material in the toner is suppressed. Therefore, even when the copy made by the toner using the polyester resin of the present invention is stored for a long time in a state of being in contact with a transparent vinyl chloride sheet, a plastic eraser, etc., the transfer of the coloring material and the transfer of the resin to the sheet Does not cause adhesion. The polyester resin of the present invention is excellent in color development during dyeing and has high stability to dyes, and thus exhibits high light fastness. Further, the toner according to the present invention is excellent in transparency and therefore not only develops color in the case of a single color, but also exhibits excellent color reproducibility in the case of being overlapped with another color, and thus is excellent in reproducibility of intermediate colors. When an image is formed on a transparent film used for an over head projector, etc.,
A good color tone is exhibited even in an image projected on a screen.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto.

EXAMPLES (Synthesis of Polyester Resin) In an autoclave equipped with a thermometer and a stirrer, 128 parts by weight of dimethyl terephthalate, 54 parts by weight of dimethyl isophthalate, and 5-sodium sulfoisophthalate. -Tomethyl ester 6 parts by weight, trimellitic anhydride 8 parts by weight, ethylene glycol 95 parts by weight, propylene glycol 34 parts by weight, tricyclodecane dimethanol 20 parts by weight, tetrabutoxy titanate 0.1 parts by weight. Was charged and heated at 180 to 230 ° C. for 120 minutes to carry out a transesterification reaction. Then, the reaction system was heated to 240 ° C., and the reaction was continued for 60 minutes at a system pressure of 1 to 10 mmHg, and as a result, a copolyester resin (A1) was obtained. The composition, glass transition temperature, and specific gravity of the obtained copolyester resin (A1) are shown in Table 1 below. Shown in. Then, the raw materials were changed, and the same polymerization was performed, as shown in Table 1. Table 2 below. To obtain polyester resins (A2) to (A15).

Ethylene oxide adduct 70 of bisphenol A was placed in an autoclave equipped with a thermometer and a stirrer.
By weight, 19.6 parts by weight of maleic anhydride and 0.2 parts by weight of hydroquinone were charged, nitrogen gas was introduced into the reaction system to maintain an inert atmosphere, and 0.05 parts by weight of dibutyltin oxide was added to 200 ° C. And reacted to obtain a polyester resin (A16). The composition, glass transition temperature, and specific gravity of the polyester resin (A16) are shown in Table 2. Shown in.

(Preparation of toner 1: Grinding / classifying method) 96 parts by weight of polyester resin (A1), 3 parts by weight of carbon black (Eftex-8 [manufactured by Cabot Corporation]), and yellow dye (Sumiplast Yellow GC) ), Red dye (Sumiplast Red FB), and blue dye (Sumiplast Blue S) [above Sumitomo Chemical] 1 part by weight each were added and melt-kneaded. Then, after pulverizing with a fine pulverizer, classification with a zigzag classifier, 2 parts by weight of silica fine powder (trade name Aerosil) was mixed with 100 parts by weight of the obtained pulverized particles with a Henschel mixer, and an average particle size of 8. 8 μm black toner (K11) was obtained. Similarly, the polyester resin is changed to the following Table 3.
The toner shown in FIG. (K21 to K161).

(Preparation of Toner 2: Wet Granulation / Dyeing) 8 parts by weight of 34 parts by weight of copolyester resin (A1), 15 parts by weight of methyl ethyl ketone, and 10 parts by weight of tetrahydrofuran.
After dissolving at 0 ° C, 56 parts of water at 80 ° C was added to obtain an aqueous microdispersion of a copolyester resin having a particle diameter of about 0.1 µm. Further, the obtained water-based microdispersion was put into a distillation flask and distilled until the distillation temperature reached 100 ° C. After cooling, water was added to make the solid content concentration 30%. Into a four-necked 1-liter separable flask equipped with a thermometer, a condenser, and a stirring blade, 330 parts by weight of the aqueous dispersion of copolymerized polyester, 10 parts by weight of a salt of polymethacrylic acid and dimethylaminoethanol were put, The temperature was raised to 90 ° C.
The stirring was continued while maintaining the temperature at 70 ° C. for 240 minutes. As a result, the copolymer having a particle size of submicron order, which was present in the polyester water-based microdispersion, grew as a united particle and had an average particle size of 7.3 μm and a diameter of 0.5D to 2D.
Polyester particles having an occupation rate (number) of particles having a particle diameter in the range of D of 95% were obtained. The obtained polyester particles were filtered and washed with water, and water was added again to obtain a 25% by weight aqueous dispersion of polyester particles.

Polyester Particle Aqueous Dispersion 400 Obtained
Parts by weight, yellow dye as miketone / polyester /
Yellow-YL (CI Disperse Yellow
w42) [Mitsui Toatsu Dye] 2 parts by weight (dye equivalent)
Was placed in a stainless pot of a dye tester, Mini Color [manufactured by Texum Giken], and dyed at 130 ° C. for 60 minutes. Thereafter, the mixture was cooled to room temperature, dehydrated, washed with water, spray-dried, and treated with silica and wax using a Henschel mixer to obtain a yellow toner (Y12). Similarly, as the magenta dye, Sumikaron Brilliant Red S-BL
F (C.I. Disperse Red 92), Sumikaron Turquoise Bull-S-GL (C.I. Disp
erse Blue 60), as a black dye, Sumicaron Navy Blue-S-GL (CI Dispe
rse Blue 79) 3 parts by weight, Macrolex
Magenta toner (M12), cyan toner (C12), and black toner (K12) were obtained using 3 parts by weight of Orange R (manufactured by Bayer).

(Evaluation of plasticizer resistance) Toner-5 parts by weight and ferrite carrier F-100 [manufactured by Powder Tech Co., Ltd.] 9
5 parts by weight were mixed by stirring with a ball mill to obtain a two-component developer. Using the obtained two-component developer, a solid pattern of 7 cm square was formed on paper by an electrophotographic copying machine. The average thickness of the toner layer on the paper was normalized to 8 μm. Put an eraser (Plastic Eraser PL-50 [Made by Lion]) on the obtained solid pattern, and
The sample was left in a constant temperature bath at 50 ° C. for 20 hours while applying a load corresponding to 0 g / cm ² . After standing, the paper and the eraser were peeled off and each surface was observed. [○] indicates that the eraser does not adhere to the paper and there is no color transfer on the eraser side, [△] indicates that the eraser is not adhered to the paper, but the eraser side does slightly transfer, and [x] indicates the paper Indicates that the eraser has completely adhered. The results are shown in Table 3. Shown in.

[0025]

As described above, the electrophotographic toner according to the present invention has been shown to exhibit a high degree of plasticizer resistance.

[0026]

[Table 1] Table 1. In Table 2, NDP is 1,5-naphthalenedicarboxylic acid TPA is terephthalic acid IPA is isophthalic acid MA is maleic acid TMA is trimellitic acid SIP is 5-sodium sulfoisophthalic acid EG is ethylene glycol PPG is propylene glycol NPG is neopentyl glycol CHD is cyclohexanediol CHDM is cyclohexanedimethanol TCD is tricyclodecanedimethanol PXG is paraxylene glycol BPE is ethylene oxide adduct of bisphenol A BPP is propylene oxide adduct of bisphenol A Tg is glass transition temperature.

[0027]

[Table 2]

[0028]

[Table 3]

Claims (1)

[Claims] 1. A toner for electrophotography, comprising a polyester resin having a specific gravity of 1.3 or more as a main constituent component of a binder resin.