JP3120645B2 - Toner for developing electrostatic latent images - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner for developing an electrostatic latent image formed on an image carrier in electrophotography, electrostatic recording and the like.

[0002]

2. Description of the Related Art Conventionally, as a developer for developing an electrostatic latent image, a two-component developer composed of a toner and a carrier or a one-component developer composed of only a toner is known. A developer for electrostatic latent image development may be mixed with a toner to improve the fluidity of the developer or the cleaning property, regardless of whether the developer is a one-component or two-component developer. It has been done.

For example, JP-A-58-1157 describes a toner obtained by treating fumed silica in which silanol groups on the surface are blocked with organosilane and fumed titania.

However, the vapor phase titania has a problem of high cohesiveness and a problem of uniform mixing with the toner, and furthermore has a problem that since the surface state is porous, the charge amount tends to fluctuate due to environmental changes, especially humidity changes. Will happen.

On the other hand, Japanese Patent Application Laid-Open No. Hei 4-3099961 discloses a toner treated with a liquid phase titania. When the liquid phase titania is used, the above-mentioned disadvantages of the vapor phase titania are solved, but the chargeability becomes insufficient, and a problem arises that the charge amount is reduced particularly during printing.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems and provides an electrostatic latent image developing toner having excellent fluidity and sufficient chargeability even after printing. Is the subject.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a toner for developing an electrostatic latent image, which is synthesized by a wet method and contains fine particles of titanium dioxide having a pH of 2.0 to 4.5.

In the present invention, titanium dioxide fine particles synthesized by a wet method such as a sulfuric acid method and a chlorine method are used.
Titanium dioxide fine particles produced by the wet method have less surface irregularities than those synthesized by the gas phase method, so that adsorption of moisture does not easily occur, and the charge amount does not decrease even in a high humidity environment. The crystal form of titanium dioxide is anatase type,
Any of rutile type and brookite type can be used.

As the above-mentioned titanium dioxide fine particles, those having a pH adjusted to 2.0 to 4.5 are used. pH 4.
If it is more than 5, the negative charge property will be low, so that a decrease in the charge amount during printing cannot be effectively prevented. If the pH is less than 2.0, the cohesiveness of the titanium dioxide fine particles themselves will be high, and they will be mixed with the toner. In this case, it is difficult to uniformly attach the toner to the toner surface. Usually, the pH of the titanium dioxide fine particles synthesized by the wet method is about 7 to 8, but a base such as ammonia is added at the time of synthesis, and the concentration, the added amount, the washing method of the obtained titanium dioxide fine particles, and the like are determined. By adjusting, the pH of the titanium dioxide fine particles can be adjusted to 2.0 to 4.5.

[0010] Further, the titanium dioxide fine particles may be a silane coupling agent such as dimethyldichlorosilane, hexamethyldisilazane, n-octyltrimethoxysilane, etc.
Titanium coupling agents such as isopropyl triisostearoyl titanate and tetraoctyl bis (ditridecyl phosphite) titanate; silicone oils such as dimethyl silicone oil, alkyl modified silicone oil; fluorine modified silicone oil; stearin Hydrophobizing treatment with a hydrophobizing agent such as an organic acid such as sodium silicate or sodium laurate is preferable because a change in toner characteristics due to a change in use environment can be suppressed. Although the pH of the titanium dioxide fine particles slightly changes due to the hydrophobic treatment, the pH of the titanium dioxide fine particles subjected to the hydrophobic treatment may be in the range of 2.0 to 4.5.

In the present invention, the above titanium dioxide fine particles may be used as a mixture with the toner, fixed on the surface of the toner, or added inside the toner.

In particular, when the above-mentioned titanium dioxide fine particles are used by being mixed with a toner, the titanium dioxide fine particles themselves have low cohesiveness, and therefore can be uniformly adhered to the toner surface. This has the effect of improving the chargeability and improving the fluidity of the toner.

When the titanium dioxide fine particles are used for a negatively chargeable toner, they have an effect of improving the toner charge amount, and when they are used for a positively chargeable toner, they have an effect of stabilizing the toner charge amount. is there.

The amount of the titanium dioxide fine particles according to the present invention is 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight, per 100 parts by weight of the toner.

The binder resin used in the toner of the present invention is not particularly limited as long as it is commonly used in toners. For example, styrene resins, acrylic resins, methacrylic resins, styrene-acrylic resins -Based resins, styrene-butadiene-based resins, olefin-based resins, polyester-based resins, epoxy-based resins, urethane-based resins, amide-based resins, phenol-based resins, and other thermoplastic or thermosetting resins, and copolymers of these resins , A block polymer, a graft polymer, a polymer blend, and the like.

In such a resin, the number average molecular weight Mn and the molecular weight distribution (Mw / Mn: weight average molecular weight Mw) are 1000 ≦ Mn ≦ 20000, 2 ≦ M
It is preferable to use w / Mn ≦ 80 and to use a number average molecular weight of 2000 ≦ Mn ≦ 15000. Further, the glass transition point of the resin is 55 ° C.
It is desirable to use a material having a softening point of 70 ° C and a temperature of 80 ° C to 140 ° C.

When used as a full-color toner, full-color images are usually reproduced by superimposing cyan, magenta, yellow and black toners. However, fog by one color toner is small. However, since the amount of fogging of the image increases due to the superposition of the respective colors, it is necessary to lower the toner fog as compared with the normal mono-color image reproduction. ADVANTAGE OF THE INVENTION According to the toner of this invention, toner fogging based on the fall of the charge amount after printing can be prevented favorably, and can be used suitably as a full-color toner.

When a translucent color toner for OHP or full color is obtained, a polyester resin is used as a binder resin from the viewpoints of vinyl chloride resistance, translucency and adhesion to an OHP sheet. It is desirable to do. Further, in this case, the glass transition point is 55 to 90 ° C, the softening point is 80 to 150 ° C, and the number average molecular weight (Mn) is 2,0.
00-15,000, molecular weight distribution (Mw / Mn) is 20
The following linear polyesters are desirable.

The colorant is not particularly limited as long as it is commonly used in toners.
For example, as a black pigment, carbon black, copper oxide, manganese dioxide, aniline black, activated carbon, ferrite, magnetite, etc., as a yellow pigment, graphite,
Zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, navels yellow, naphthol yellow S, banza yellow G, banza yellow 10G, benzidine yellow G,
Benzidine yellow GR, quinoline yellow lake, permanent yellow NCG, tartrazine lake, etc.
Red pigments include red lead, molybdenum orange, permanent orange GTR, pyrazolone orange, vulcan orange, and induslen brilliant orange G
K, Bengala, Cadmium Red, Lead Red, Permanent Red 4R, Risor Red, Pyrazolone Red, Watching Red, Lake Red C, Lake Red D, Brilliant Carmine 6B, Eosin Lake, Rhodamine Lake B, Alizarin Lake, Brilliant Carmine 3
B, Permanent Orange GTR, Vulcan Fast Orange GG, Permanent Red F4RH, Permanent Carmine FB and the like, and as the blue pigment, navy blue, cobalt blue, alkali blue lake, Victoria blue lake, phthalocyanine blue and the like can be used. The amount of these colorants is 1 to 20 parts by weight, preferably 3 to 15 parts by weight, based on 100 parts by weight of the resin in the toner.

Examples of the anti-offset agent for improving the fixing property include low molecular weight polyethylene wax, low molecular weight oxidized polyethylene wax, low molecular weight polypropylene wax, low molecular weight oxidized polypropylene wax, higher fatty acid wax, higher fatty acid ester wax and sasol wax. , Carnauba wax and the like can be used alone or in combination of two or more.

The amount of the offset preventing agent used is 1 to 15 parts by weight, preferably 2 to 8 parts by weight, based on 100 parts by weight of the resin in the toner.

Further, a charge control agent may be added to the toner of the present invention. Examples of positive charge control agents include nigrosine base EX, quaternary ammonium salts, polyamine compounds,
An imidazole compound or the like can be used, and as the negative charge control agent, a chromium complex salt type azo dye, a copper phthalocyanine dye, a chromium complex salt, a zinc complex salt, an aluminum complex salt,
A calixarene compound or the like can be used. The amount of these charge control agents is 0.1 to 10 parts by weight, preferably 0.5 to 100 parts by weight, based on 100 parts by weight of the resin in the toner.
５5 parts by weight.

Further, magnetic particles may be added to the toner of the present invention. As the magnetic particles, cobalt, iron, metals showing ferromagnetic material such as nickel, aluminum, cobalt, iron, lead, magnesium, nickel, zinc, antimony, beryllium, bismuth, cadmium, calcium,
Alloys of metals such as manganese, selenium, titanium, tungsten, and vanadium, and mixtures thereof, and fine particles of known magnetic substances such as oxides and fired bodies (ferrites) can be used. The amount of the magnetic particles depends on the amount of the resin 100 in the toner.
It is desirable to use 1 to 80 parts by weight, preferably 5 to 60 parts by weight with respect to parts by weight.

Further, the toner of the present invention contains silica, alumina, magnesium fluoride, silicon carbide, boron carbide, titanium carbide, zirconium carbide, boron nitride, titanium nitride, zirconium nitride, magnetite, molybdenum disulfide, aluminum stearate, Inorganic fine particles such as magnesium stearate and zinc stearate may be added and mixed.

Further, when these inorganic fine particles are subjected to a hydrophobizing treatment with a hydrophobizing agent such as a silane coupling agent, a titanium coupling agent, a higher fatty acid, or silicone oil,
It is preferable because a change in toner characteristics due to a change in use environment can be suppressed.

Further, emulsion polymerization, soap-free emulsion polymerization,
Styrene, acrylic, methacrylic, granulated by wet polymerization such as non-aqueous dispersion polymerization, or gas-phase polymerization
Volume average particle size of benzoguanamine, silicon, Teflon, polyethylene, polypropylene, etc. 0.01 to 5 μm
About various kinds of organic fine particles may be added to and mixed with the toner.

The above-mentioned inorganic and organic fine particles are not particularly required when the toner of the present invention is in a form in which titanium dioxide fine particles are added to and mixed with toner particles, and may be added supplementarily to titanium dioxide fine particles. Further, when the titanium dioxide fine particles are added to the toner particles of the toner of the present invention, it is preferable to add and mix the above inorganic or organic fine particles to the toner.

The average particle size of the toner is preferably set to 3 to 15 μm. Particularly, when a high-definition image is reproduced,
The average particle size is desirably 3 to 9 μm, preferably 3 to 8 μm.

The toner obtained as described above can be used as a one-component developer composed of only a toner or as a two-component developer together with a carrier. When used as a two-component developer, the above-described toner and a known carrier may be mixed and used.

As the carrier, those usually used such as an iron powder carrier, a ferrite carrier, a coating carrier, a binder type carrier and the like can be used.

As the coating carrier, one coated with various synthetic resins or ceramic layers using iron or ferrite as a core material is used. Examples of the synthetic resin include polystyrene resin, poly (meth) acrylic resin, styrene-acrylic resin, polyolefin resin, polyamide resin, polycarbonate resin, polyether resin, and polysulfonic acid. -Based resin, polyester-based resin, epoxy-based resin, polybutyral-based resin, urea-based resin, urethane / urea-based resin, silicone-based resin, polyethylene-based resin, Teflon-based resin and other thermoplastic resins and thermosetting Resins and mixtures thereof, and copolymers, block polymers, graft polymers and polymer blends of these resins are used. Further, resins having various polar groups may be used to improve the chargeability. Further, in order to improve the chargeability and other various developer properties, various organic and / or inorganic materials may be dispersed and / or dissolved and coated, and these materials may be fixed on the surface of the coating carrier. A thing may be used.

As the binder type carrier, a carrier obtained by dispersing a magnetic powder in the above synthetic resin is used.

Next, a specific embodiment of the present invention will be described, and it will be apparent that the toner according to the embodiment of the present invention is excellent.

[0034]

【Example】

(Synthesis of Titanium Dioxide 1) 900 g of titanium tetrachloride is gradually added to 1 kg of water cooled to 4 ° C. while stirring.
Next, an aqueous ammonium sulfate solution was added and the mixture was boiled, then cooled, and aqueous ammonia was added to precipitate white crystals. The precipitate is washed with water and dried at 110 ° C., followed by 1 hour at 900 ° C.
The mixture was heated for a period of time to obtain titanium dioxide 1 having a pH of 4.0.

(Synthesis 2 of titanium dioxide) Titanium sulfate 80
1 kg of water is added to 0 g and boiled to obtain a white precipitate. The precipitate is washed with water and dried at 110 ° C.
For 2 hours to obtain titanium dioxide 2 having a pH of 2.5.

(Surface Treatment of Titanium Dioxide) The titanium dioxide 1 was subjected to a surface treatment with hexamethyldisilazane,
3.8 titanium dioxide 3 was obtained.

(Method of measuring pH) 4 g of titanium dioxide was weighed into a 500 cc polybeaker, 50 cc of methanol was added, and the mixture was stirred gently. Thereafter, 50 cc of water is added, and the mixture is gently stirred, and stirred with a homomixer (TK homomixer: manufactured by Tokushu Kika Kogyo Co., Ltd.) at a rotation speed of 2000 rpm for 5 minutes. This dispersion is measured with a pH meter (PH51: manufactured by Yokogawa Electric Corporation).

(Production Example of Tona-1) Bisphenol A type polyester resin 100 parts by weight (softening point 121 ° C., glass transition point 66 ° C.) Carbon black (MA # 8: manufactured by Mitsubishi Kasei Kogyo Co., Ltd.) 5 parts by weight -Bontron E-84 (manufactured by Orient Chemical Industry Co., Ltd.) 3 parts by weight
After kneading with a screw extruder, the mixture was cooled. The kneaded material was coarsely pulverized, and a toner having an average particle diameter of 3 to 20 μm (average particle diameter 10.0 μm) was obtained by air classification.

To 100 parts by weight of the toner, 1.0 part by weight of the above titanium dioxide 1 was added and mixed to obtain toner 1.

(Toner-2 Production Example) Toner-2 was obtained in the same manner as in Tona-1 Production Example except that titanium dioxide 1 was changed to titanium dioxide 3.

(Production Example of Tona-3) Toner-3 was obtained in the same manner as in the production example of Tona-1, except that titanium dioxide 1 was changed to titanium dioxide 2.

(Tona-4 Production Example) In the same manner as in the Tona-1 production example, except that titanium dioxide 1 was changed to vapor-phase titanium dioxide P-25 (manufactured by Nippon Aerosil Co., Ltd.).
4 was obtained.

(Production Example of Toner-5) In the production example of Toner-5, titanium dioxide 1 was replaced by wet-processed titanium dioxide MT-600.
B (manufactured by Teica) except that the toner-5
I got

(Production Example of Tona-6) In the production example of Tona-1, titanium dioxide 1 was replaced by hydrophobic vapor phase titanium dioxide T-8.
Toner-6 was obtained in the same manner except that the toner was changed to 05 (manufactured by Nippon Aerosil Co., Ltd.).

(Production Example of Toner 7) 100 parts by weight of styrene / acrylic resin (softening point 132 ° C., glass transition point 61 ° C.) 5 parts by weight of carbon black (MA # 8: manufactured by Mitsubishi Kasei Kogyo Co., Ltd.) 5 parts by weight of nigrosine base EX (Manufactured by Orient Chemical Industry Co., Ltd.) 3 parts by weight ・ The above-mentioned titanium dioxide 1 2 parts by weight After sufficiently mixing the above materials with a Henschel mixer, 2 parts by weight
After kneading with a screw extruder, the mixture was cooled. The kneaded material was coarsely pulverized, and a toner having an average particle diameter of 3 to 20 μm (average particle diameter 10.0 μm) was obtained by air classification.

To 100 parts by weight of this toner, 0.3 parts by weight of hydrophobic silica R972 (manufactured by Nippon Aerosil Co., Ltd.) was added and mixed to obtain toner-7.

(Production Example of Toner-8) In the production example of Toner-7, titanium dioxide 1 was replaced by a wet process titanium dioxide MT-600.
B (Toyca)
I got

(Evaluation) Toners 1 to 4 obtained in the above production examples
8 was evaluated for toner fluidity, toner charge amount, and printing durability.

(Fluidity of toner) The apparent specific gravity of the toner is measured by a bulk density measuring instrument (Kuramo Kagaku Kikai Seisakusho, JIS K5101). The larger the value, the more the toner
Of 0.400 g / cm ³
The above shows excellent fluidity (○), 0.380 g /
cm ³ or more 0.400 g / a cm below ³ indicates a practical use flowable (△), was evaluated as 0.380 g / a cm below ³ that is not sufficient practical upper not flowable (×) .

(Toner charge amount and printing durability test)
Each of Nos. 1 to 8 was mixed with a silicone / acrylic resin-coated ferrite carrier at a weight ratio of 8:92 to prepare a developer. 100,000 sheets using a copying machine EP570Z (manufactured by Minolta Camera) for a developer using toners 1 to 6, and a copying machine EP470Z (manufactured by Minolta Camera) for a developer using toners 7 and 8. Was carried out, and the toner charge amount at the initial stage and after the printing period was measured to evaluate the charging stability after the printing period.

The initial charge amount is 20.0 to 28.
0 μc / g for ○, 12.0 to 20.0 μc / g for Δ, 1
X was 2.0 μc / g or less.

The amount of charge after 100,000 sheets has been printed is as follows:
If the difference from the initial charge amount is 5.0 μc / g or less, and there is no fog on the image, ○ indicates that the difference is greater than 5.0 μc / g and 8.0 μc / g or less, and the fog is slight. Was evaluated as △, and x was obtained when the difference was greater than 8.0 μc / g or fog was remarkable. The difference from the initial charge amount was 8.0 μm.
If it exceeds c / g, the control range on the copying machine side will be exceeded, and the difference in image density will be remarkable.

[0053]

[Table 1]

[0054]

According to the present invention, it is possible to provide a toner for developing an electrostatic latent image having excellent fluidity and sufficient chargeability after printing.

[0055]

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-4-30961 (JP, A) JP-A-5-134445 (JP, A) JP-A-5-19528 (JP, A) JP-A-1- 105961 (JP, A) JP-A-64-574 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 9/08

Claims (3)

(57) [Claims] 1. A composition synthesized by a wet method and having a pH of 2.0 to
4.5. An electrostatic latent image developing toner containing 4.5 titanium dioxide fine particles. 2. The electrostatic latent image according to claim 1, wherein the titanium dioxide fine particles have been subjected to a hydrophobic treatment with a hydrophobizing agent, and the pH of the titanium dioxide fine particles after the hydrophobic treatment is 2.0 to 4.5. Development toner. 3. The toner for developing an electrostatic latent image according to claim 1, wherein the titanium dioxide fine particles are mixed with the toner.