JP3232858B2 - Electrophotographic toner composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophotographic method, an electrostatic recording method, in an electrostatic printing method or the like, about the electrophotographic toner composition for developing an electrostatic charge image.

[0002]

2. Description of the Related Art Conventionally, as a method of visualizing an electrostatic latent image with toner in electrophotography, for example, a magnetic brush method described in U.S. Pat. No. 2,674,063 and a U.S. Pat. , 616,552, and the like, and the dry developer used in these methods is a one-component developing method using a toner itself in which a colorant is dispersed in a binder resin. And a two-component developer in which a carrier is mixed with the toner. Since these developers by themselves do not have sufficient properties such as storability, transportability, developability, transferability, and chargeability, additives are externally added to the toner for the purpose of improving these properties. That is often done. As an additive, hydrophobic silica fine powder (JP-A-56-12895)
No. 6), silica fine particles to which aluminum oxide or titanium oxide fine particles are added (JP-A-60-2388).
No. 47), those obtained by subjecting a vapor-phase method titanium oxide to a hydrophobizing treatment (JP-A-59-52255), anatase-type titanium oxide (JP-A-60-112052), and aluminum oxide-coated titanium oxide (JP-A-60-12052). No. 57-79961) and the like. Further, titanium oxide fine particles that have been surface-treated with a coupling agent (JP-A-4-404)
No. 67, 4-348354, etc., surface treatment of an inorganic compound used as an external additive has already been proposed.

[0003]

Generally, fine particles of several nm to several tens nm are used as external additives. Most of the fine particles are present as primary particles, but some are present as aggregates of several to several hundreds.They have a particle size distribution similar to the toner, and the external additive itself is several μm. Coarse particles exist. When the external additive and the toner are mixed using a mixer, most of these aggregates can be loosened, but there are aggregates that remain without being loosened, and the size of the toner particles is larger than the toner particle size. Something is also allowed. In particular, when the external additive is subjected to a surface treatment with a treating agent, it exists as strong aggregates, which are released without adhering to the toner (hereinafter referred to as free external additives). It is often recognized that these free external additives migrate to the photoconductor together with the toner when the toner is developed on the photoconductor surface, remain on the photoconductor surface even after transfer, and adhere to the photoconductor surface without being cleaned. Can be When these free external additives accumulate on the surface of the photoreceptor, they often cause image quality defects on copying (filming, comet) and scratches on the surface of the photoreceptor. Is causing it to be shorter. In addition, there is a problem that the toner is spilled from the developing machine during development and contaminates the inside of the copying machine. The conventionally proposed additives in the above-mentioned developer did not sufficiently solve the above-mentioned problems caused by free external additives.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a toner having excellent charge amount, environmental stability of charge, toner admix property, durability and the like, and image quality caused by free external additives in a copying machine and photoreceptor contamination. Ru near to provide a toner for electrophotography which can obtain high-quality images without defects.

[0005]

Means for Solving the Problems The present inventors have intensively studied and studied an electrophotographic toner composition in order to improve the above-mentioned drawbacks in the prior art. It has been found that the above object can be achieved by using a titanium oxide having a component amount of not more than a predetermined value, and further using a titanium oxide having a predetermined particle size distribution, thereby completing the present invention.

That is, the electrophotographic toner composition of the present invention is an electrophotographic toner composition comprising a toner particle containing a colorant and a binder resin and an additive, wherein the additive is produced by a wet method. Titanium oxide fine particles that have been subjected to a surface treatment, wherein the additive is 30
0 nm transmittance is 7% to 30% and 600n
m transmittance is 80% to 100%. The surface-treated titanium oxide fine particles of the present invention are a step of mechanically highly dispersing titanium oxide fine particles produced by a wet treatment in a medium, a step of subjecting the fine particles to a surface treatment with a treating agent, and a treatment obtained. It can be produced by a process of crushing fine particles.

Various methods for measuring the particle diameter of the external additive have been conventionally studied. Among them, it is well known that a confirmation method using a SEM (scanning transmission electron microscope) photograph is an effective means. However, methods for investigating particle variation (particle size distribution) and oversize (aggregate) are hardly known, and when information is to be obtained from SEM photographs, it is necessary to confirm from a large number of photographs. However, there is a problem that it takes an enormous amount of time. However, in the present invention, the above-mentioned conventional problems can be solved by employing the measurement method described below. The transmittance by the UV absorption method in the present invention means a value measured as follows. That is, polyoxyethylene (10) octyl phenyl ether 1
25.0 mg was precisely weighed and dispersed in 250 ml of an aqueous solution, stirred with a magnetic stirrer for 5 minutes, further dispersed with an ultrasonic shaker for 5 minutes, immediately diluted 10-fold, and used with a UV spectrophotometer. 300 nm and 600
Measure the transmittance in nm. In the present invention, 300 nm
Has a particle size and particle size distribution of the external additive, and a transmittance of 600 nm reflects the presence of aggregates of the external additive. Therefore, by defining the transmittance at 300 nm and 600 nm, it becomes possible to control the particle size, particle size distribution, and oversize of the external additive.

Hereinafter, the present invention will be described in detail. As the colorant constituting the toner particles of the present invention, known colorants can be used. For example, carbon black is used as the black toner, and C.I. I. Pigment Red 48: 1, C.I. I. Pigment Red 12
2, C.I. I. Pigment Red 57: 1, C.I. I. Pigment Yellow 97, C.I. I. Pigment Yellow 12, C.I. I. Pigment Yellow 17, C.I. I.
Pigment Blue 15: 3 and the like can be exemplified as typical ones. Similarly, as the binder resin constituting the toner particles, known resins may be used. For example, styrenes such as styrene, vinyl styrene and chlorostyrene; monoolefins such as ethylene, propylene, butylene and isobutylene; vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate and vinyl butyrate; methyl acrylate; Esters of α-unsaturated aliphatic monocarboxylic acids such as ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate; Examples of vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl butyl ether; homopolymers or copolymers of vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and vinyl isopropenyl ketone It can be. Further, polyester, polyurethane, epoxy resin and the like can be used alone or in a mixed form.

Among these binder resins, it is particularly effective to use polyester. The polyester can be produced by reacting a polyhydroxy compound with a polybasic carboxylic acid or a reactive acid derivative thereof.
Examples of the polyhydroxy compound constituting the polyester include diols such as ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, and 1,4-butanediol; and hydrogenated bisphenols. A, bisphenol A such as polyoxyethylenated bisphenol A, polyoxypropylene bisphenol A
Examples include alkylene oxide adducts, other dihydric alcohols, and dihydric phenols such as bisphenol A. As the polybasic carboxylic acid, for example, malonic acid, succinic acid, adipic acid, sebacic acid, alkyl succinic acid, maleic acid, fumaric acid, mesaconic acid, citraconic acid, itaconic acid, glutaconic acid, cyclohexanedicarboxylic acid, Fumaric acid, isophthalic acid, terephthalic acid,
Other divalent carboxylic acids or their anhydrides,
And reactive acid derivatives such as alkyl esters and acid halides. In addition to these carboxylic acids, a polyhydric hydroxy compound having a valence of 3 or more and / or a polybasic carboxylic acid having a valence of 3 or more can be added in order to make the polymer non-linear so as not to cause insolubles in tetrahydrofuran. . Among these polyesters, a linear polyester resin comprising a polycondensate containing bisphenol A and an aromatic polycarboxylic acid as main monomer components can be particularly preferably used. As for the physical properties of the polyester, the softening point is 90 to 150 ° C, the glass transition point is 50 to 70 ° C, the number average molecular weight is 2,000 to 6,000, and the weight average molecular weight is 8,000.
Resins having a range of 15000, an acid value of 5 to 30, and a hydroxyl value of 5 to 40 can be particularly preferably used.

In the present invention, the content of the colorant in the toner particles is preferably in the range of 1 to 8 parts by weight based on 100 parts by weight of the binder resin. When the content of the colorant is less than 1 part by weight, the coloring power is weakened, and when the content is more than 8 parts by weight, the transparency of the toner is deteriorated. If necessary, known additives such as a charge control agent and a fixing aid may be contained in the toner particles. Further, as the toner particles, those having an average particle size of about 30 μm or less, preferably 5 to 20 μm can be used.

In the present invention, the surface-treated titanium oxide fine particles to be added as an external additive are obtained by subjecting titanium oxide fine particles produced by a wet method to a surface treatment, and have a transmittance of 300 nm in the above-mentioned predetermined UV absorption method. Those having a transmittance of 7% to 30%, preferably 9% to 28% and a transmittance of 600 nm of 80% to 100%, preferably 85% to 100%, particularly preferably 87 to 98% are used. When the transmittance at 300 nm is lower than 7%, the particle diameter of the titanium oxide fine particles increases, and the mixing property and fluidity deteriorate. When the transmittance is higher than 30%, the particle diameter of the titanium oxide fine particles increases. Smaller,
Mixability and fluidity deteriorate. When the transmittance at 600 nm is lower than 80%, agglomerates of titanium oxide fine particles are generated, and the free external additives adhere to the photoreceptor, thereby causing image defects.

Here, the wet method is a method of producing a compound through a chemical reaction in a solvent, and the main production methods include a sulfuric acid method and a hydrochloric acid method. In the sulfuric acid method, the following reaction proceeds in a liquid phase to form insoluble hydrous titanium oxide. FeTiO ₃ + 2H ₂ SO ₄ → FeSO ₄ + TiOSO
₄ + 2H ₂ O TiOSO ₄ + 2H ₂ O → TiO (OH) ₂ + H ₂ SO
_{4 In} the hydrochloric acid method, titanium tetrachloride is first dissolved in water.
At this time, the aqueous solution becomes an aqueous hydrochloric acid solution. Next, a strong base such as caustic soda is added to generate titanium hydroxide Ti (OH) ₄ , thereby precipitating titanium hydroxide. Both the hydrous titanium oxide and the titanium hydroxide undergo a firing step to become titanium oxide fine particles.

The water-soluble component content of the titanium oxide fine particles produced by the wet method is preferably less than 0.2% by weight. When the amount of the water-soluble component is 0.2% by weight or more, the charge amount is low as in the case of the conventional titanium oxide,
Even if the surface treatment is performed, the charge amount does not become sufficiently high. When titanium oxide having a water-soluble component content of less than 0.2% by weight is used, the charge amount is increased, and when the surface treatment is performed, a higher charge amount is maintained. Titanium oxide is insoluble in water and has no water-soluble component, but in the case of titanium oxide fine particles produced by a wet method, it is inevitable that a trace amount of a water-soluble component remains from the production process. By the water-soluble component remains, carry a water absorption tends to attract water, although their resistance would reduce the decreased charge amount, by eliminating or reducing water-soluble components, resistance is increased Therefore, it is estimated that a high charge amount is maintained. Water-soluble components include K ⁺ , Na ⁺ , Li ⁺ ,
Mg ²⁺ , PO ₄ ²⁻ , SO ₄ ²⁻ , Cl ⁻ , and the like. For the measurement of the water-soluble component, 5 g of titanium oxide fine particles were boiled with 250 ml of water, cooled, and filtered to obtain a filtrate 10.
It is carried out by evaporating 0 ml and drying the remaining amount. The details are described in JIS K5116-1973 titanium dioxide (pigment), and the water-soluble component in the present invention is measured according to JIS.
The remaining amount is expressed as a percentage by weight based on the original titanium dioxide.

The titanium oxide fine particles produced by the above-mentioned wet method need to be mechanically highly dispersed in a medium before or during the surface treatment. The high dispersion treatment is preferably performed simultaneously with the step of subjecting the fine particles to a surface treatment with a treating agent. That is, in the process of dispersing the titanium oxide and the surface treating agent in the solvent, the use of a dispersing machine called a medium stirring mill can effectively eliminate the aggregates of the titanium oxide before the surface treatment. Organic solvents such as aromatic solvents such as toluene and benzene, and aliphatic solvents such as hexane are used as the solvent. Examples of the medium stirring mill include Ultra Visco Mill (manufactured by Imex Corporation) and Pure Mill (manufactured by Asada Iron Works). By performing this high dispersion treatment, when the surface-treated product is crushed by a pin mill, aggregates can be significantly reduced. If the above-mentioned high dispersion treatment is not performed, aggregates will be present in the titanium oxide before the surface treatment, and as a result, the surface of the aggregates will be covered with the treating agent to form a strong aggregate, so that the surface treatment is performed. Later, it becomes difficult to disintegrate the primary particles in the crushing, especially when the throughput is large. In order to loosen these aggregates, there is a method of increasing the number of pin mills.
It is difficult to loosen to the next particle.

As the treating agent used for the surface treatment, water
Those which react with an acid group can be mentioned. For example,
Coupling agent, titanate coupling agent, aluminate
For coupling agents, zirconium coupling agents, etc.
Can use springing agent, silicone oil, etc.
You. Among them, sila represented by the following chemical formula
Coupling agents and silicone oils are preferred.
You. R_4-xSi (NCO)_x R_4-xSi (OR₁)_x R_4-xSiCl_x (X is an integer of 1 to 3, and R is an alkyl having 1 to 16 carbons.
Kill group or perfluoroalkyl group, OR₁Is metoki
(Indicates an alkoxy group such as a silyl group or an ethoxy group.) Specifically, (CH_Three)_TwoSi (NCO)_Two, CH_ThreeS
i (NCO)_Three, C_TenH _{twenty one}Si (OCH_Three)_Three, CF_Three
Si (OCH_Three)_ThreeWhere x is 3
This is preferable in that the charge amount increases. For similar reasons, R is
An alkyl group having 7 to 16 carbon atoms or perfluoroalkyl
Preferred is a thiol group. Also, as silicone oil,
Methyl silicone, methyl phenyl silicone, monomer
Use modified silicone oil in addition to chill silicone
can do. The processing amount of the processing agent is 2 to 3
It can be used in the range of 0% by weight.

The surface-treated titanium oxide fine particles obtained by the surface treatment as described above are then subjected to a crushing treatment by a pin mill or the like. Thereby, the titanium oxide aggregated at the time of the surface treatment is loosened to become primary particles.

In the toner composition of the present invention, the titanium oxide fine particles are added in an amount of 0.5 to 3% by weight based on the toner particles. Further, titanium oxide fine particles having an average particle diameter in the range of 5 to 30 nm are used, and may be used in combination with other additives such as silica and alumina. The additive can be attached to the surface of the toner particles by, for example, a high-speed mixer. In particular,
Henschel mixer, mechanofusion system (manufactured by Hosokawa Micron), mechanomill (manufactured by Okada Seiko) and the like.

The electrophotographic toner composition of the present invention may be a one-component developer using no carrier or a two-component developer using a carrier. However, it is desirable to use it as a two-component developer. When a carrier is used, the carrier is not particularly limited as long as it is a known carrier, and an iron powder-based carrier, a ferrite-based carrier, a surface-coated carrier, a magnetic powder-dispersed carrier, or the like can be used.

[0019]

In the present invention, the surface-treated titanium oxide fine particles shown below are added to the toner particles as an external additive to maintain the toner charge required for development under high temperature and high humidity, while maintaining the toner charge amount. The charge uniformity, charge exchange between toner particles,
The charge distribution can be sharpened, and as a result, a high-quality image free from image quality defects due to contamination in the copying machine and contamination of the photoconductor can be obtained.

[0020]

The present invention will be described below with reference to examples. 1) Production of Toner Particles Polyester resin (condensate of bisphenol A ethylene oxide 100 parts by weight adduct and terephthalic acid, Mn = 3000, Mw = 9000) Magenta colorant (CI pigment red 57: 1) 4 Parts by weight The above components were melted and kneaded, pulverized and classified to obtain a toner having an average particle diameter of 8 μm. 2) Production of Additives In the production of the following additives, rutile-type titanium oxide (MT-150A; manufactured by Teica Co., Ltd.) having an average particle size of 15 nm produced by a sulfuric acid method was used as wet titanium oxide.
The titanium oxide contained 0.30% by weight of a water-soluble component. (Additive a) 400 g of titanium oxide fine powder was washed with water and the water-soluble component was adjusted to 0.18% by weight to a toluene solvent in which 64 g of decyltrimethoxysilane was dissolved, followed by ultrasonic dispersion. Then, after performing a high dispersion treatment by a medium stirring mill, the toluene in the dispersion is evaporated and dried,
Heat-treat with a dryer set at 120 ° C and remove with pin mill.
It was pulverized twice to obtain titanium oxide fine particles surface-treated with decyltrimethoxysilane. Polyoxyethylene (10)
In 250 ml of 1% aqueous solution of octyl phenyl ether,
A finely weighed 25.0 mg of this titanium oxide was dispersed, stirred for 5 minutes with a magnetic stirrer, further dispersed for 5 minutes with an ultrasonic shaker, immediately diluted 10-fold, and using a UV spectrophotometer. 300nm and 600n
m was measured. As a result, the transmittance at 300 nm was 24.3%, and the transmittance at 600 nm was 93.3%.
No precipitate was generated even after standing for 0 minutes.

(Additive b) Titanium oxide fine particles surface-treated with decyltrimethoxysilane were treated in the same manner as in the preparation of Additive a, except that the high dispersion treatment was not performed using a medium stirring mill. As a result of measuring the transmittance at 300 nm and 600 nm using a UV spectrophotometer in the same manner as for the additive a, the transmittance at 300 nm was 43.9%, and the transmittance at 600 nm was 78.9%. Things were confirmed. (Additive c) A titanium oxide surface-treated with decyltrimethoxysilane was obtained in the same manner as in the case of Additive b, except that the number of times of pin mill grinding after the surface treatment was four. As a result of measuring the transmittance at 300 nm and 600 nm using a UV spectrophotometer in the same manner as the additive a, the transmittance at 300 nm was 9.0%, the transmittance at 600 nm was 68.7%,
After standing for 30 minutes, a precipitate was observed.

Example 1 1.2 parts by weight of an additive a was added to 100 parts by weight of the toner particles, and mixed with a Henschel mixer to obtain a toner composition. Iron powder coated with a fluorine-containing acrylic resin and having an average particle size of 50 μm was used as a carrier, and the toner composition was mixed to a toner concentration of 8% by weight to prepare a developer. Using this developer, a copier (A-Color6)
35, manufactured by Fuji Xerox Co., Ltd.). The evaluation was performed by examining the state of deposits on the photoreceptor surface after copying 25,000 sheets and examining image quality defects of the obtained images. As a result, no deposits and scratches were observed on the surface of the photoreceptor, and a good image was obtained. Also, no spilling of white powder into the copier and no adhesion to the surface of the transfer drum were observed.

Comparative Example 1 1.2 parts by weight of the additive b was added to 100 parts by weight of the toner particles, and mixed with a Henschel mixer to obtain a toner composition. Iron powder coated with a fluorine-containing acrylic resin and having an average particle size of 50 μm was used as a carrier, and the toner composition was mixed to a toner concentration of 8% by weight to prepare a developer. Using this developer, a copier (A-Color6)
35, manufactured by Fuji Xerox Co., Ltd.). The evaluation was performed by examining the state of deposits on the photoreceptor surface after copying 25,000 sheets and examining image quality defects of the obtained images. As a result, deposits were observed on the surface of the photoreceptor, and the image was also recognized as an image quality defect. In addition, spilling of white powder into the copying machine and adhesion to the transfer drum surface were considerably confirmed.

Comparative Example 2 1.2 parts by weight of the additive c was added to 100 parts by weight of the toner particles, and mixed with a Henschel mixer to obtain a toner composition. Iron powder coated with a fluorine-containing acrylic resin and having an average particle size of 50 μm was used as a carrier, and the toner composition was mixed to a toner concentration of 8% by weight to prepare a developer. Using this developer, a copier (A-Color6)
35, manufactured by Fuji Xerox Co., Ltd.). The evaluation was performed by examining the state of deposits on the photoreceptor surface after copying 25,000 sheets and examining image quality defects of the obtained images. As a result, deposits were found on the surface of the photoreceptor, and slight image quality defects were also found in the image. In addition, spilling of white powder into the copying machine and adhesion to the transfer drum surface were confirmed.

[0025]

The toner composition for electrophotography according to the present invention uses the titanium oxide fine particles which have been subjected to the surface treatment satisfying the above-mentioned conditions as external additives. The effect is that contamination can be suppressed for a long time, and a high-quality image free from image quality defects can be obtained for a long time.

Continuation of the front page (56) References JP-A-4-40467 (JP, A) JP-A-4-30961 (JP, A) JP-A-4-2044751 (JP, A) JP-A-6-11887 (JP, A) JP-A-6-19186 (JP, A) JP-A-5-119517 (JP, A) JP-A-6-118697 (JP, A) JP-A-6-11886 (JP, A) 5-94037 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 9/08

Claims (4)

(57) [Claims] 1. An electrophotographic toner composition comprising toner particles containing a colorant and a binder resin and an additive, wherein the additive is a surface-treated titanium oxide fine particle produced by a wet method. A toner composition for electrophotography, wherein the additive has a transmittance at 300 nm of 7% to 30% and a transmittance at 600 nm of 80% to 100% in a UV absorption method. 2. The method according to claim 1, wherein the additive is 300 nm in a UV absorption method.
2. The electrophotographic toner composition according to claim 1, wherein the transmittance is 9% to 28% and the transmittance at 600 nm is 85% to 100%. 3. The toner composition for electrophotography according to claim 1, wherein the treating agent used for the surface treatment is a coupling agent or a silicone oil. 4. The electrophotographic toner composition according to claim 1, wherein the binder resin is a polyester resin.