JPH0695222B2 - Development method - Google Patents

Description

The present invention relates to a method for developing an electrostatic latent image, more specifically, a method for developing an electrostatic latent image with a one-component developer.

[Conventional technology]

As the developer used for developing the electrostatic latent image, a two-component developer composed of two components of toner and carrier and a one-component developer composed of only toner are used. In the case of a one-component developer, since only toner particles are used, there is a problem in how to impart an electric charge to the toner. When a charge is applied to the toner by electrostatic induction using a relatively conductive toner, a change over time in charging such as triboelectric charging and environmental dependence can be ignored, and good developability can always be obtained. However, since the conductive or semi-conductive toner is used, the transfer onto paper or the like cannot be performed well. A method of applying an electric charge to a toner by contact between a toner and a developing device component such as a trimmer or a sleeve, triboelectric charging, or triboelectric charging of toner particles has been proposed and put into practical use. Therefore, the drawbacks of the conventional two-component developer, such as the change in chargeability over time and the dependence on the environment, cannot be essentially eliminated. A method of charging a toner by ion irradiation using a corotron (Japanese Patent Laid-Open No. 50-9833) has many practical problems such as uneven charging, corotron contamination, and ozone generation. A method utilizing dielectric polarization has also been proposed (Japanese Patent Laid-Open No. 49-90931), but in this case, only a portion where the change in electric field strength is large can be developed in principle, which is not common. As described above, the conventional one-component developing method cannot sufficiently satisfy the chargeability, developing property and transferability of the toner, and the drawbacks of the two-component developing method have not been solved yet.

[Problems to be solved by the invention]

An object of the present invention is to solve the above-mentioned problems in the one-component developing method and to provide a developing method excellent in developability and transferability.

Another object of the present invention is to provide a developing method in which charging, developing and transferability are stable against environmental changes such as temperature and humidity.

Still another object of the present invention is to provide a developing method with excellent image quality.

[Means and Actions for Solving Problems] The above-mentioned object is to provide toner particles (A) containing a binder resin containing a polymer of a monomer having a nitrogen-containing polar group as an essential component, and the toner particles (A). A uniform thin layer of a developer prepared by mixing with A) a master particle (B) in which a discontinuous layer of external additive particles having a pH of ≤4 is formed on at least the surface layer is arranged facing the electrostatic latent image. It is achieved by a developing method which is characterized in that it is formed on the developed developer carrying member and is developed under an alternating electric field. Hereinafter, the configuration of the present invention will be described in more detail. First, as a monomer component for introducing a nitrogen-containing polar functional group into the developer binder resin, N-methylaminoethyl acrylate,
Substituted amino group-containing acrylates such as N-ethylaminoethyl acrylate, N, N-diethylaminoethyl acrylate, N, N-dibutylaminoethyl acrylate, N, N-diethylaminopropyl acrylate, aminoethyl methacrylate, N, N-dimethylamino Ethyl methacrylate, N, N-diethylaminoethyl methacrylate, N-methylaminoethyl methacrylate, N-ethylaminoethyl methacrylate, 2-N, N-dicyclohexylaminoethyl methacrylate, N, N-dibutylaminoethyl methacrylate, 2-phenylaminoethyl Methacrylates, substituted amino group-containing methacrylates such as 2-dibenzylaminoethyl methacrylate, aminostyrene, dimethylaminoethylstyrene, N-methylaminoethylstyrene, dimethyl Amino styrenes amino ethoxy styrene, allylamine, allyl amines such as allyl methyl amine, N- vinylpyridine, 2-
Vinyl pyridines such as vinyl-5-methyl pyridine, vinyl amines, vinyl quinolines and allyl quinolines, acrylamides, N-vinyl amides and the like can be used.

A nitrogen-containing polar functional group introduced into the binder resin by polymerizing such a monomer component, particularly a functional group rich in electron donor property or cationic property such as a substituted amino group is an electron-withdrawing component, particularly ionic or A surface conductive electron-withdrawing component that easily causes electron transfer is used as an external additive containing a carboxyl group (-COOH group) and / or a phenol group (-OH group) of pH ≤ 4 (measured by JIS K 6221). It exhibits a good charge exchange property in the coexistence, but in order to satisfy all the various physical and chemical requirements from every step of image formation as a developer, a substituted amino group represented by the following general formula (A) is required. It is desirable to use a binder resin containing a polymer of group-containing methacrylate or acrylate monomers.

In the above formula, R ₁ is a hydrogen atom or a methyl group, and R ₂ and
R ₃ is hydrogen or a lower alkyl group having 1 to 4 carbon atoms,
May be the same or different, and at least one of R ₂ and R ₃ is a lower alkyl group having 1 to 4 carbon atoms,
n is an integer of 1 to 4. Hereinafter, the particles having the above structure will be referred to as toner particles, and the toner particles with an external additive mixed with the toner particles will be hereinafter referred to as master particles. The master particles are obtained by adding and mixing an external additive to the toner particles as follows. As the external additive, it is possible to use inorganic oxides such as metal oxides, which show pH ≦ 6 when dispersed or dissolved in ion-exchanged water, inorganic halides, inorganic salts, carbon and the like. If necessary, these may be used after organically treating the surface with a silane coupling agent, a titanate coupling agent, a higher fatty acid and its derivative, a higher alcohol or the like. Further, it may be subjected to a composite treatment with another inorganic substance. Furthermore, resin fine particles prepared by emulsion polymerization or suspension polymerization or obtained by a pulverization method, higher fatty acids and their derivatives, organic oxides, organic halides, organic salts and the like can also be used. Above all, pH ≦ 4
When the inorganic fine particles having a polar functional group of a carboxyl group (—COOH group) and / or a (—OH group) are used, the overall performance as a developer and the developing characteristics can be easily controlled. Preferably, acidic carbon black [Carbon Black Association's edition, "Handbook of Carbon Black", Book Publishing Co., Ltd., issued November 25, 1972, 2.3 Surface Structure (183-
196)], silica fine powder, titanium oxide fine powder, etc., and those having a particle size of 1 μm or less, particularly 0.1 μm or less are conveniently used. Master particles are obtained by mixing the above-mentioned external additives with the above-mentioned toner particles, but the toner particles and the master particles are mixed in a ratio of (5-10): 1 to develop the toner used in the invention. It can be an agent.

The developer having the above structure is uniformly formed in a thin layer on the developer carrier, and an alternating electric field is applied to develop the developer, thereby achieving both developability and transferability, and against environmental changes. It is possible to obtain a stable copying machine. The alternating electric field has a frequency of 1 to 5 KHz, preferably 1 to 3 KHz, and a maximum and minimum potential width (peak-to-peak potential V _PP ) of 500 to 2000 V, preferably 10 as a waveform optimal for using this developer.
By setting it to 00-1500V, a copy with excellent image quality can be obtained.

By combining the above developer and developing method,
The reason why the developability and the transferability are compatible with each other and the development can be stably performed against environmental changes is not clear, but the present inventors consider as follows. As a step in which the toner particles finally have a true charge, the charge generated by the charge exchange between the nitrogen-containing polar functional group of the toner particles and the polar group of the master particle is used. That is, as shown in FIG. 1, charge exchange is performed between the amino groups 2 of the toner particles 1 and the electron-withdrawing polar groups 3 of the external additive 4 of the master particles, whereby the toner particles 1 and the outside of the master particles. The four parts of the additive are respectively charged to form a pair on the particle surface (Fig. 2). After that, in the developing area, due to mutual contact of particles under the developing electric field, charge exchange further occurs, or charge transfer through the external additive occurs, and a true charge is generated on the side of the photosensitive material in the developer. (Fig. 3).

Since the true charge generated at this time is the charge generated in the insulating particles, it is not caused by frictional electrification or induction of the conductive toner, which is easily influenced by environmental conditions. For this reason, it is considered that it is stable against changes in environmental conditions and that no transfer failure occurs.

Further, when this developer is used, excellent image quality can be obtained in the range of the alternating electric field described above because the particles having a true charge respond to the alternating electric field and form an image with the developer carrier. It is considered to reciprocate between the carriers to clean the particles adhering to the background portion and the extra particles around the image.

As described above, the developer used in the present invention is a developer containing an amino group in the toner particles in the developer particles and an electron-withdrawing polar group as an external additive on the surface of the master particle. It utilizes the charge generated by the charge exchange between the amino groups of the toner particles in the particles and the polar groups in the external additive on the surface of the master particle. The external additive may be insulative or conductive, but insulative. It is necessary to form a discontinuous layer on the surface layer of the particles and adjust the developer to 10 ₁₄ Ωcm or more.

Further, it is considered that the optimum ratio of the toner particles to the master particles is (5 to 10): 1 because the charge exchange property effective for development is exhibited when the ratio is within the range.

〔Example〕

 The developing method of the present invention will be described below with reference to examples.

Example 1 28 parts of styrene resin (ST-120, Sanyo Chemical Co., Ltd.), 12 parts of low molecular weight polyethylene wax (2203A, acid value 40, Mitsui Petrochemical Co., Ltd.) containing a carboxyl group (V-COOH group), magnetic 60 parts of the body (EDT-1000, manufactured by Toda Kogyo Co., Ltd.) is melt-kneaded by a rotor rotary type kneader for 10 minutes, cooled, coarsely crushed by a crusher, and then finely crushed by a jet crusher, and then by an air classifier. Fine powder of 5 μm or less and coarse powder of 40 μm or more were removed to obtain toner particles having an average particle size of 13 μm. To the toner particles, 0.5% by weight of the developer and acidic carbon black having a pH of 3 were added and mixed to obtain master particles. The toner particles and the master particles were mixed at a ratio of 7: 1 to obtain a developer (Sample A). And

Next, a diethylaminoethylmethacrylate-styrene copolymer (diethylaminoethylmethacrylate component 7 mol%, number average molecular weight 5000, amine value 30) was used in place of the styrene resin, and otherwise the toner had an average particle diameter of 13 μm with exactly the same formulation. The particles were obtained. To the toner particles, 0.5% by weight of the developer and acidic carbon black having a pH of 3 are added and mixed to obtain master particles, and the toner particles and the master particles are mixed at a ratio of 7: 1 to prepare a developer (sample B) was obtained.

Using the above two types of toner, a thin toner layer is uniformly formed on a developer carrier made of magnetrol, and development is carried out under the conditions of DC and AC developing electric fields shown in Table 1 to obtain a copy. It was The results are shown in Table 2.

From the results shown in Table 2, it was found that when the developer of Sample B was used and development was performed by an alternating electric field, environmental stability, transferability and image quality, which were the conventional problems, were all solved.

Example 2 Toner particles and master particles were prepared in the same manner as in Sample B, and the five types of developers shown in Table 3 were prepared by changing the ratio of the toner particles to the master particles.

When the above five kinds of developers were used and the respective characteristic values were evaluated under an alternating electric field under the same conditions as in Example 1, the results shown in Table 4 were obtained.

From Table 4, the ratio of the toner particles and the master particles is (5
10) It was revealed that good results were obtained when the ratio was 1: 1.
Regarding the developing electric field, in addition to the experimental conditions of the above-mentioned example as an AC electric field, a peak-to-peak potential V _PP of 50
0 to 2000V, frequency 1 to 5KHz, DC component | 100 | V to | 500
| V was available.

〔The invention's effect〕

The present invention is an external addition of pH ≦ 4 to at least the surface layer of toner particles (A) containing a binder resin containing a polymer of a monomer having a nitrogen-containing polar group as an essential component and the insulating particles (A). A uniform thin layer of developer consisting of master particles (B) on which a discontinuous layer of developer particles is formed is formed on a developer carrier arranged so as to face the electrostatic latent image and developed under an alternating electric field. This is because all of the problems in the conventional one-component development method, such as incompatibility of developability and transferability, environmental dependency of image quality, temporal dependency of image quality, poor image quality, etc. As a result, a stable copy can be obtained over a long period of time and against environmental changes, so that a highly reliable copying machine can be provided, and maintenance costs can be reduced.

[Brief description of drawings]

FIG. 1, FIG. 2 and FIG. 3 are explanatory views of true charge formation by the developer used in the developing method of the present invention. Symbols in the figure: 1 ... Insulating toner particles; 2 ... Amino group; 3 ... Electron-withdrawing group; 4 ... External additive.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Takashi Yamamuro 2274 Hongo, Ebina City, Kanagawa Prefecture Fuji Zero Tux Co., Ltd.Ebina Business Office (72) Inventor Takayuki Sunaga 2274, Hongo, Ebina City, Kanagawa Fuji Zero Tux Co., Ltd.Ebina Business In-house (56) Reference JP-A-58-17454 (JP, A) JP-A-57-130047 (JP, A) JP-A-55-18658 (JP, A)

Claims (5)

[Claims] 1. Toner particles (A) containing a binder resin containing a polymer of a monomer having a nitrogen-containing polar group as an essential component, and at least the surface layer of the toner particles (A) has a pH of 4 (JIS
According to K 6221), a uniform thin layer of developer formed by mixing with master particles (B) forming a discontinuous layer of external additive particles is arranged so as to face the electrostatic latent image. A developing method, which comprises forming on top and developing under an alternating electric field. 2. A monomer having a nitrogen-containing polar group is represented by the general formula [In the formula, n is an integer of 1 to 4, R ₁ is a hydrogen atom or a methyl group, R ₂ and R ₃ may be the same or different, and a hydrogen atom or a carbon atom number 1 to 4 is a lower alkyl group, but R ₂ and R ₃ are not hydrogen atoms at the same time. ] The developing method according to claim 1, which is a compound represented by the formula [1]. 3. External additive particles having pH ≦ 4 (according to JIS K 6221)
2. The developing method according to claim 1, wherein the developing agent is carbon black. 4. The development according to claim 1, wherein the developer is obtained by mixing the toner particles (A) in a ratio of 5 to 10 with respect to the master particles (B) 1. Method. 5. The maximum and minimum potential width (V _PP ) is 500 V ≦ V _PP ≦ 2000 V, and the frequency (f) is 1 KHz ≦ f ≦ 5 KHz.
The developing method according to claim 1, wherein the developing is performed by an alternating electric field.