JPH08328301A - Toner for two-component magnetic developer and developer - Google Patents

Abstract

PURPOSE: To ensure enough electric charges of a toner for development without blending with a negative charge controlling agent, to prevent the transfer of an electrostatic charge controlling agent to the surface of a carrier and defective electrostatic charge due to this spending, to stabilize the electrostatic chargeability of the toner over a long period of time and to prolong the serive life of the toner and carrier. CONSTITUTION: This toner is a negative charge type two-component toner contg. carbon black dispersed in a fixing resin medium and not blended with an electrostatic charge controlling agent. The fixing resin medium is a styrene-acrylic copolymerized resin or resin compsn. having free or neutralized anionic polar groups, having an acid value of 4-30 obtd. by measuring the anionic polar groups in the form of a free acid and contg. PE resin having a number average mol.wt. of 1,000-7,000 by 0.5-5 pts.wt. per 100 pts.wt. of the fixing resin medium. The pH of the carbon black is <7, the value of (7-pH)/specific surface area (m<2> /g) is 0.010-0.05 and the carbon black is used by 4-15wt.% of the amt. of the fixing resin medium.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-component magnetic developer toner excellent in spent resistance, and more specifically, it does not contain a transferable charge control agent, and more The present invention relates to a toner in which toner is not scattered, transfer is efficiently performed, a high-density image can be formed, fixing is good, and the life of the toner and the carrier is extended.

[0002]

2. Description of the Related Art A so-called two-component magnetic developer is widely used as a developer for developing an electrostatic charge image formed on an electrophotographic photosensitive member. This two-component magnetic developer is
It is composed of a composition of a magnetic carrier composed of iron powder, ferrite particles and the like, and an electroscopic toner composed of a colored resin composition. During development, by mixing a magnetic carrier and toner, the toner particles are charged to a constant polarity, the mixture is conveyed to the photoconductor in the form of a magnetic brush, and the surface of the photoconductor is rubbed with the magnetic brush. The charged toner is adsorbed and held on the charge image on the surface of the photoconductor to form a visible image.

In order to control the polarity of toner particles due to triboelectric charging to a constant level, a charge control agent is generally contained in the toner particles. For negatively chargeable toner, metal-containing complex salt dye or oxycarboxylic acid is used. A negative charge control agent such as a metal complex of an acid is used (for example, Japanese Patent Laid-Open No. 3-67268), and for a positively chargeable toner, a positive chargeability control such as an oil-soluble dye such as nigrosine or an amine-based control agent is used. Agent (for example, JP-A-56
No. 106249) is used.

It has been known for a long time to use a magnetic toner as a toner for a two-component magnetic developer. For example, the above-mentioned JP-A-56-106249 and JP-A-59-1.
Japanese Patent Laid-Open No. 62563 describes use of a magnetic powder internally-added toner in which magnetic powder is contained in the toner, while Japanese Patent Application Laid-Open No. 3-67268 discloses adding and mixing silica powder and magnetic powder to a toner base. The magnetic powder externally added toner is described.

[0005]

A two-component magnetic developer is one in which a magnetic carrier and a toner are mixed and used, but even if they show satisfactory charging performance, they are charged due to the generation of so-called spent (toner). It is known that performance deteriorates and its life is shortened. The spent (toner) is a phenomenon in which the toner component adheres and deposits in the form of a film on the surface of the magnetic carrier, and since the surface of the magnetic carrier becomes closer to that of the toner, the triboelectric charging line approaches and a predetermined amount of toner is generated. The charging performance cannot be obtained. Thus, when the spent occurs, the magnetic carrier must be discarded and replaced with a new magnetic carrier.

Therefore, an object of the present invention is to provide a two-component magnetic developer which is excellent in spent resistance and has a long life of toner and carrier. Another object of the present invention is that the toner particles do not contain a transferable charge control agent and do not contain a CCA (charge control agent) capable of increasing the apparent development sensitivity without toner scattering during development (CCA). (2) To provide a toner for a two-component magnetic developer.

Still another object of the present invention is a CCA-less two-component system in which the transfer from the surface of the photoconductor to the paper is efficiently performed and the fixing is excellent even though it does not contain a transferable charge control agent. To provide a magnetic developer.

[0008]

According to the present invention, in a negatively chargeable two-component magnetic developer toner in which carbon black is dispersed in a fixing resin medium, the fixing resin medium is free. Or a neutralized anionic polar group-containing styrene acrylic copolymer resin or resin composition having an acid value of the anionic polar group measured in the form of a free acid in the range of 4 to 30, and having a number average molecular weight of 1000 to 700
0.5 to 5 parts by weight per 100 parts by weight of the fixing resin medium, and the carbon black has a pH of less than 7 and (7-pH) / specific surface area (m).
² / g) is in the range of 0.010 to 0.050 and is compounded in an amount of 4 to 15% by weight with respect to the fixing resin medium. Provided.

According to the present invention, there is also provided a two-component magnetic developer comprising the above-mentioned toner and a resin-coated magnetic carrier or a magnetic carrier obtained by dispersing magnetic powder in a resin.

[0010]

The present inventors have found the following interesting facts in the process of conducting research to prevent the generation of toner spent. FIG. 1 of the accompanying drawings shows that among toners for conventional two-component magnetic developers used for developing positively charged images, toners containing a chromium complex salt dye (2: 1 type) as a charge control agent were extracted by extraction with methanol. FIG. 2 is an absorbance curve of a liquid at a wavelength of 200 to 700 nm, which has a peak in a wavelength range of 400 to 700 nm, and FIG. 2 shows a value of a methanol extract of a toner using a salicylic acid metal complex as a charge control agent at a wavelength of 200 to 700 nm. It is an absorbance curve, and the wavelength is 280 to 35.
It has a peak in the region of 0 nm.

According to these results, all the extract liquids showed a characteristic absorption peak based on the charge control agent, which means that the surface of the toner particles contains the charge control agent in a considerably high concentration. ing.

On the other hand, in FIG. 3, the toner used in the measurement of FIG. 1 is used as a two-component magnetic developer, and the carrier in which the charging failure due to the spent occurs is similarly extracted with methanol. The absorbance curve at 200 to 700 nm is measured, and the wavelength is 400 to 70.
It has a peak in the region of 0 nm. According to this measurement result, the charge control agent adheres to and deposits on the carrier surface in a high concentration, and the charging failure due to the spent is not the mere filming of the carrier surface by the toner resin, which has been considered in the past. The surprising fact that it was a transition to the carrier surface was revealed.

This fact will become more apparent with reference to FIGS. 4 and 5. 4 and 5 show the relationship between the mixing time and the spent amount and the mixing time and the charging amount for the mixture of the toner containing the charge control agent and the magnetic carrier and the mixture of the toner not containing the charge control agent and the magnetic carrier. It is a plot of the relationship with. From these results, it becomes clear that the toner containing the charge control agent has a larger amount of spent than the toner not containing the charge control agent, resulting in a large decrease in the charge amount.

Further, FIG. 6 shows the relationship between the amount of spent spent carrier and the charge control agent in the spent toner, and the dotted line in FIG. 6 plots the predicted value calculated from the toner prescription. It was done. According to these results, it becomes clear that the charge control agent is selectively transferred to and adheres to the carrier surface at the early stage of spent generation. 5 and 6 show the results in the closed system without toner replenishment, and it can be expected that the difference due to the presence or absence of the charge control agent will be further widened when the toner is replaced in the copying machine.

Furthermore, FIG. 7 shows the relationship between the mixing time and the amount of spent when the individual components in the toner are mixed with the magnetic carrier. According to this result, it was clarified that the charge control agent is a component that easily migrates to the carrier surface among the respective components in the toner and easily causes spent. From the above, as shown in the explanatory view of FIG. 8, the charging failure due to the spent generation in the conventional two-component magnetic developer is caused by the spent transfer of the charge control agent to the carrier surface at the initial stage of mixed use. It can be explained that the spent layer is negatively charged as it is formed, and a positively charged opposite polarity toner is formed.

In the present invention, in order to prevent the transfer of the charge control agent to the surface of the magnetic carrier, the addition or blending of the transfer charge control agent to the toner particles is stopped. Along with this, as shown in the absorbance curve of FIG. 9, the toner of the present invention does not have an absorption peak at a wavelength of 400 to 700 nm even when this toner is extracted with methanol.
Alternatively, if present, the absorbance is substantially zero. Further, as shown in the absorbance curve of FIG. 9, even if the absorbance of the above extract is measured at a wavelength of 280 to 350 nm, there is no absorption peak and no absorbance peak. As a result, the first feature of the present invention is that the transfer of the charge control agent to the carrier surface is suppressed and the spent resistance is improved. Incidentally, in the present specification, the absorbance is substantially zero,
Even if an absorption peak in the above wavelength region is not detected at all in an extract obtained by extracting 0.1 g of toner with 50 ml of methanol, it means that the absorbance at that peak is 0.05 or less.

By the way, as shown in FIG. 5, the toner containing no charge control agent is inadequate in charge amount as compared with the toner containing the charge control agent. In the present invention, in order to prevent this, a resin or resin composition for copolymerization having an anionic polar group having an acid value of 4 to 30 is used as a fixing resin medium, and carbon black as a colorant is used. Use one whose pH is on the acidic side. By using such a fixing resin medium and carbon black, the minimum charge controllability of triboelectric charging can be obtained during development. By using such a fixing medium and carbon black, the amount of toner charge required for development can be obtained.

That is, the anionic polar group contained in the fixing resin medium imparts negative charge controllability to the toner, and since this polar group exists in the molecular skeleton of the resin, the charge control agent is present. As described above, it does not migrate to the particle surface of the carrier and cause a spent. The fixing resin medium used in the present invention has an acid value related to having an anionic polar group as described above, and the acid value is in the range of 4 to 30. Good. That is, when the acid value is greater than 30, the amount of anionic groups increases, and the hygroscopicity of the toner itself increases.
It tends to be difficult to perform stable triboelectric charging.
If the acid value is less than 4, the amount of anionic groups is small and it may be difficult to secure a sufficient toner charge amount for development. The anionic polar group may be present in a free form (free acid form), or may be present in a metal salt such as sodium salt, that is, in a neutralized form. Is measured in the free acid form. That is, the acid value in the present invention, when at least a part of the anionic polar group is present in a neutralized state,
It is the value measured in the form of free acid by hydrolyzing this.

The anionic polar group having an acid value of 4 to 30 is
Although it imparts charge controllability to the toner, its polar group exists on the side chain or terminal of the polymer that constitutes the resin,
Crosslinking between polar groups (mainly hydrogen bond due to hydroxyl groups) is likely to occur, the binding property of the resin is increased, and the heat-melting property is improved, which is disadvantageous for fixing. Further, the anionic polar group,
In addition to cross-linking, it is also bonded to the resin skeleton, and while it does not migrate to the surface of the toner particles, the bond between the toner particles and carrier in the magnetic brush during development is weakened by the Coulomb force. It is recognized that the scattering is remarkable, which causes the toner contamination of the copying machine and the fog density of the copy to increase.

In the present invention, in order to prevent these, first, a specific amount of a polyethylene resin (polyethylene wax) is contained in the toner, and the toner having a low softening point is used to improve the fixability of the toner. Further, the magnetic powder is contained in the toner in a specific amount so that the toner scattering is prevented by the magnetic attraction force of the toner-carrier in addition to the Coulomb force of the toner-carrier.

In the present invention, the number average molecular weight is 100.
0 to 7000 polyethylene resin as resin medium 100
One of the salient features is that the incorporation of 0.5 to 5 parts by weight per part by weight prevents the deterioration of fixing when a resin having a specific acid value is used. The reason is considered as follows. That is, the number average molecular weight is 1000
The polyethylene resin of to 7000 has a low softening point,
Further, it has a characteristic of sharp melting (melting rapidly due to a sharp decrease in viscosity) in the vicinity of the softening point, as compared with a styrene acrylic resin used as a toner fixing resin. Therefore, at the time of fixing, in the toner medium, the polyethylene resin is first melted and penetrates into the paper (wet the paper), and the affinity of the paper for coating is reduced. Then, it has the function of making the permeability of the subsequently melted toner fixing resin into paper advantageous, and it is considered that the fixing property is improved. Therefore, even if a fixing resin having a specific acid value, which has a defect that the fixing property is deteriorated as compared with the conventional fixing resin, in the present invention, a toner fixing property equal to or higher than that of the conventional toner can be obtained. Of.

The number average molecular weight of the polyethylene resin is 10
When it is less than 00, the softening point of the resin is low, so that the toner fixing property is improved, but the durability is deteriorated due to the blocking of the toner in the toner hopper or the like and the increase in the amount of spent due to poor dispersion of the resin. When the number average molecular weight of the polyethylene resin is more than 7,000, the softening point of the resin becomes too high, and the effect of improving the toner fixing property, which is the purpose of mixing the resin, cannot be obtained.

The content of polyethylene resin is resin medium 1
If the amount is less than 0.5 parts by weight per 100 parts by weight, the effect of improving the toner fixing property cannot be obtained. On the other hand, when the content of the resin is more than 5 parts by weight, drum filming occurs and the image is remarkably deteriorated. Alternatively, the durability is deteriorated due to the increase in the amount of spent.

Further, as described above, in the present invention,
As the colorant, carbon black having a pH on the acidic side (that is, less than 7) and a (7-pH) / specific surface area (m ² / g) in the range of 0.010 to 0.050 is used. It is important to. Generally, carbon black has a pH of about 8 and is biased toward neutral or alkaline side. In addition, although carbon black acid-treated to have a pH of less than 7 is known in order to control the conductivity, in the present invention, even if a carbon black having a pH of less than 7 is selectively used, the conductivity is reduced. Does not mean that controlled carbon black is used.

According to the study by the present inventors, it was confirmed that when the carbon black and the magnetic carrier were mixed and stirred, the carbon black was negatively charged. That is, in the present invention, by using the carbon black which has been treated with an acid and has a pH of less than 7, the negative chargeability of the fixing resin medium having the anionic polar group is reinforced, and the negative charge control agent is used. It is possible to effectively prevent the deterioration of the charging property due to the unblended.

The value of (7-pH) / specific surface area (m ² / g) mentioned above in the present invention is an index showing the degree of acid treatment, that is, the density of acid functional groups present on the surface of carbon black. Is smaller than the above range, the negative chargeability is not sufficiently reinforced and the chargeability is unavoidably deteriorated. On the other hand, when it is larger than the above range, the hygroscopicity of the toner becomes high, and it becomes difficult to secure a stable triboelectric charge amount. The pH of carbon black is 1 for 5 g of sample.
Put in 100 ml of deionized water, boil for 5 minutes, let cool,
It can be measured by replenishing the evaporated water, filtering this with filter paper, and measuring the filtrate with a commercially available glass electrode pH meter.

The toner of the present invention is generally 5 to 15 μm.
However, it is desirable to attach spacer particles having a particle size of 0.05 to 1.0 μm to the surface of the toner particles. Generally, in order to improve the powdery fluidity of the toner, a fluidity improver such as fine particle silica is externally attached and used. In the present invention, a particle size of 0.05 or less is used together with the fluidity improver. By interposing spacer particles having a thickness of 1.0 μm to 1.0 μm, the bond between the toner image and the latent image on the surface of the photoconductor is weakened so that the toner image can be easily separated. It has succeeded in improving efficiency.

[0028]

Preferred Embodiment of the Invention

(Fixing Resin Medium) The fixing resin medium used in the present invention is a copolymer resin or resin composition having an anionic polar group having an acid value of 4 to 30. Examples of the anionic polar group include any polar group such as carboxylic acid, sulfonic acid, phosphonic acid and the like, and a carboxylic acid type group is particularly preferable. The copolymer resin having an anionic polar group is a resin having a monomer having an anionic polar group incorporated into the resin by random copolymerization, block copolymerization, graft copolymerization or the like. Suitable examples of comonomers are:

Examples of the carboxylic acid type include ethylenically unsaturated carboxylic acids such as acrylic acid and methacrylic acid,
Examples thereof include lower alkyl half esters such as crotonic acid, maleic acid, maleic anhydride, fumaric acid, maleic acid and fumaric acid. Examples of the sulfonic acid type include styrene sulfonic acid and 2-acrylamido-2-methylpropane sulfonic acid.

Examples of the phosphonic acid type include 2-acid phosphoxypropyl methacrylate, 2-acid phosphoxyethyl methacrylate, and 3-chloro-2-acid phosphoxypropyl methacrylate. These anionic polar group-containing monomer units may be a free acid, or may be neutralized with an alkali metal such as sodium or potassium, an alkaline earth metal such as calcium or magnesium, or zinc. .

The other monomer, which is the main component of the resin or resin composition, is one in which the resulting polymer has the fixability and chargeability required for the toner, and is a monomer having an ethylenically unsaturated bond. 1 or a combination of two or more thereof is used. Suitable examples of such monomers include acrylic acid ester-based monomers, monovinyl aromatic monomers, vinyl ester-based monomers, vinyl ether-based monomers, diolefin-based monomers,
Monoolefin-based monomers and the like. Specifically, the following can be exemplified. In addition, in the following description, the lower alkyl group means one having 5 or less carbon atoms.

Examples of the acrylic ester-based monomer include the following formula (1): CH ₂ ═C (R ¹ ) —COOR ² (1) where R ¹ is a hydrogen atom or a lower alkyl group, and R ² is , An alkyl group having 11 or less carbon atoms, or an alkyl group having 12 or more carbon atoms, or a hydroxyalkyl group having 11 or less carbon atoms, in particular, methyl acrylate, ethyl acrylate, butyl acrylate, acrylic acid-2 -Ethylhexyl, cyclohexyl acrylate, phenyl acrylate, methyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, ethyl β-hydroxyacrylate, γ-hydroxypropyl propyl, δ-
Butyl hydroxy acrylate, β-hydroxyethyl methacrylate, lauryl acrylate, tridecyl acrylate, stearyl acrylate, docosyl acrylate, dicyclohexylmethyl acrylate, dicyclohexylpropyl acrylate, cyclododecyl acrylate,
Cycloundecane methyl acrylate, lauryl methacrylate, tridecyl methacrylate, stearyl methacrylate, docosyl methacrylate, dicyclohexylmethyl methacrylate, dicyclohexylpropyl methacrylate,
Examples thereof include cyclododecyl methacrylate and cycloundecane methyl methacrylate.

As the monovinyl aromatic monomer, for example, the following formula (2): CH ₂ ═C (R ³ ) -Φ-R ⁴ (2) In the formula, R ³ is a hydrogen atom, a lower alkyl group or a halogen atom. Or an alkyl group having 12 or more carbon atoms, R ⁴ is a hydrogen atom, a lower alkyl group, an alkyl group having 12 or more carbon atoms,
A halogen atom, an alkoxy group, an amino group, a nitro group, Φ is a phenylene group, as a substituent, a lower alkyl group, an alkyl group having 12 or more carbon atoms, a halogen atom,
Alkoxy groups, amino groups, optionally having nitro groups, monovinyl aromatic hydrocarbons such as styrene, α
-Methylstyrene, vinyltoluene, α-chlorostyrene, o-, p-, m-chlorostyrene, p-ethylstyrene, as well as m- or p-laurylstyrene, m- or p-stearylstyrene, α-methyl-3. -Stearyl styrene, m- or p- stearoxy styrene, 4-vinyl benzoate stearyl, 4-stearoyl amino styrene etc. can be mentioned.

Examples of the other monomer include those represented by the following general formula (3), (4), (5) or (6). CH in ^{_{2 = CH-OOCR 5 (3}} ) formula, R ⁵ is a hydrogen atom, a lower alkyl group, or 1 carbon atoms
Vinyl esters of two or more alkyl groups, such as vinyl formate, vinyl acetate, vinyl propionate, as well as vinyl laurate, vinyl tridecanoate, vinyl stearate, vinyl docosanoate, vinyl triacontanate,
Vinyl pentyl cyclohexanoate, vinyl dicyclohexyl acetate, etc.

CH ₂ ═CH—O—R ⁶ (4) In the formula, R ⁶ is an alkyl group having 11 or less carbon atoms or 12 or more carbon atoms, such as vinyl ether, for example vinyl methyl ether, vinyl ethyl ether, vinyl- n-butyl ether, vinyl phenyl ether, vinyl cyclohexyl ether, vinyl lauryl ether, vinyl stearyl ether, vinyl docosyl ether, vinyl cyclododecyl ether and the like.

CH ₂ ═C (R ⁷ ) —C (R ⁸ ) ═CH—R ⁹ (5) In the formula, each of R ⁷ , R ⁸ , and R ⁹ is a hydrogen atom, a lower alkyl group, or a carbon number of 12 or more. An alkyl group or a halogen atom, a diolefin such as butadiene, isoprene, chloroprene, and 1,3-hexadecadiene,
1,3-docosadiene, 2-methyl-1,3-docosadiene and the like.

CH ₂ ═C (R ¹⁰ ) —R ¹¹ (6) In the formula, each of R ¹⁰ and R ¹¹ is a hydrogen atom, a lower alkyl group, or an alkyl group having 12 or more carbon atoms. Classes such as ethylene, propylene, isobutylene, butene-1, pentene-1, 4-methylpentene-1, as well as 1-tetradecene and 1-eicocene.

A suitable copolymer resin contains an anionic polar group-containing monomer and one or more kinds of the acrylic acid ester-based monomer of the formula (1) as an essential component, and optionally a formula ( 2) to a copolymer resin containing the monomer of the formula (6) as an optional component, and most preferably a styrene-acrylic copolymer resin. Taking a copolymer resin having an alkyl group having 12 or more carbon atoms in its side chain as a specific example, specific examples thereof include styrene- (meth) acrylic acid-stearyl (meth) acrylate stearyl copolymer and styrene- (meth). Acrylic ester- (meth) acrylic acid stearyl- (meth) acrylic acid copolymer, styrene- (meth) acrylic acid stearyl- (meth) acrylic acid copolymer, styrene- (meth) acrylic acid stearyl-maleic acid copolymer Examples thereof include polymers.

In the present invention, the anionic polar group-containing copolymer resin having an acid value of 4 to 30 can be used alone as described above, or a composition containing two or more anionic polar group-containing copolymer resins, or It can also be used as a fixing resin medium in the form of a composition of a copolymer resin containing an anionic polar group and a copolymer resin having no anionic polar group. When the fixing resin medium is composed of the resin composition, the content of the anionic polar group in the resin composition as a whole is preferably in the range described above for the copolymer resin.

(Polyethylene resin) The polyethylene resin is a low-density and / or high-density low-molecular-weight polyethylene resin having a number average molecular weight of 1,000 to 7,000.
Is used. Further, the polyethylene resin is
Generally used as a release agent for fixing rollers,
As the release agent for heat fixing, the polyethylene resin alone, various waxes, or low molecular weight olefin resin may be used in combination.

(Carbon Black) In the present invention, the carbon black dispersed in the fixing resin medium has a pH of less than 7, preferably 2 to 5, and (7-pH) / specific surface area ( As long as m ² / g) is in the range of 0.010 to 0.050, particularly 0.015 to 0.040, any one can be used, but in general, furnace black is used, which is What was prepared by processing to have a pH value satisfying the above-mentioned conditions is preferable. The acid treatment can be carried out using, for example, an inorganic acid such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, or an organic acid such as acetic acid, citric acid, propionic acid, benzoic acid, salicylic acid, or toluenesulfonic acid. An acidic group such as a carboxyl group is introduced on the surface of carbon black to reinforce the negative chargeability of the toner. The amount of acid used for the treatment is, as is clear from the above pH conditions,
Since it is a very small amount, it does not adversely affect the electrical characteristics of the toner.

The specific surface area of such carbon black is usually 50 m ² / g or more, particularly 100 to 300 m ²
The range of / g is preferable from the viewpoint of dispersibility in the resin. Such carbon black is blended in an amount of 4 to 15% by weight, particularly 6 to 12% by weight, based on the fixing resin medium. If this blending amount is less than the above range, the negative chargeability of the toner becomes unsatisfactory,
Fog is likely to occur. If it is used in a larger amount than the above range, the fixability of the toner will deteriorate.

(Other compounding agents) In the two-component magnetic developer toner of the present invention, various toner compounds known per se other than the above carbon black are used except that the charge control agent is not compounded. An agent such as an extender pigment may be dispersed and compounded in the fixing resin medium.

For example, as the extender pigment, barite powder,
Examples thereof include barium carbonate, clay, silica, white carbon, talc, and alumina white. Such pigments are used in an amount of 2 to 20 parts by weight, especially 5 to 15 parts by weight, per 100 parts by weight of the fixing resin medium.

Further, in the present invention, it is preferable to disperse and mix the magnetic powder in the fixing resin medium, and the mixing of the magnetic powder causes the toner particles in the magnetic brush at the time of development to have a magnetic attraction force in addition to the Coulomb force. Since it is also held by the carrier by means of the carrier, the toner scattering is more reliably prevented, and it is extremely preferable from the viewpoint of preventing toner contamination of the copying machine and fogging of the copy. Such advantages are required as the copying speed increases. The addition of such magnetic powder also has the advantage that the amount of charge per toner particle can be reduced, the developing sensitivity can be improved, and a high-density image can be obtained.

Examples of such magnetic powder include magnetic powders conventionally used in toners, for example, iron tetroxide (Fe ₃ O).
₄ ), ferric oxide (γ-Fe ₂ O ₃ ), zinc iron oxide (Z
nFe ₂ O ₃ ) and yttrium iron oxide (Y ₃ Fe ₅
O ₁₂ ), iron cadmium oxide (CdFe ₂ O ₄ ), iron gadolinium oxide (Gd ₃ Fe ₅ O ₁₂ ), iron oxide copper (CuFe)
₂ O ₄ ), lead iron oxide (PbFe ₁₂ O ₁₉ ), iron nickel oxide (NiFe ₂ O ₄ ), iron neodymium oxide (NdFeO)
₃ ), iron oxide barium (BaFe ₁₂ O ₁₉ ), iron oxide magnesium (MgFe ₂ O ₄ ), iron manganese oxide (MnF)
e ₂ O ₄ ), lanthanum iron oxide (LaFeO ₃ ), iron powder (Fe), cobalt powder (Co), nickel powder (Ni), and the like. A particularly suitable magnetic powder is fine particle triiron trioxide (magnetite). The preferred magnetite has a regular octahedral shape and a particle size of 0.05 to 1.0 μm. The magnetite particles may be surface-treated with a silane coupling agent, a titanium coupling agent, or the like.

The above-mentioned amount of the magnetic powder compounded is the resin medium 10
0.1 to 5 parts by weight, especially 0.5 to 3.
A small amount such as 0 parts by weight is sufficient. Conventionally, in the magnetic toner used for the one-component magnetic developer, the magnetic powder is used in an amount of more than 10 parts by weight per 100 parts by weight of the resin medium, but the amount used in the present invention is considerably smaller than this. Therefore, it is possible to form a high-density image while preventing toner scattering with such a small amount of internal addition. The amount of magnetic powder used is 0.1
If the amount is less than 5 parts by weight, toner scattering tends to occur, while if the amount is more than 5 parts by weight, the developing density may decrease.

(Toner Manufacturing Method) The toner of the present invention can be manufactured by a known method such as a pulverizing and classifying method, a melt granulating method, a spray granulating method and a polymerization method, but the pulverizing and classifying method is generally used. is there. That is, the above-mentioned fixing resin medium and various toner compounding agents are premixed with a mixer such as a Henschel mixer, and then kneaded with a kneading device such as a twin-screw extruder, and the kneaded composition is cooled and then pulverized. , Classify to obtain toner.
The particle size of the toner is preferably such that the volume-based average particle size (median size by Coulter counter) is in the range of 5 to 15 μm, particularly 7 to 12 μm.

If necessary, a fluidity improver such as hydrophobic vapor phase silica may be externally added to the surface of the toner particles to improve the fluidity of the toner. Such a fluidity improver usually has a primary particle size of 0.005 to 0.05.
It is an extremely fine powder of about 0 μm, and is externally added in an amount of 0.1 to 2.0% by weight based on the total weight of the toner (that is, based on the total amount of the toner particles and the external additive described above). Good.

According to a preferred embodiment of the present invention, at this time, together with the fluidity improver, spacer particles having a particle size of 0.05 to 1.0 μm, which is larger than the above fluidity improver, are contained to improve the transfer efficiency. Improve.

As the spacer particles, organic or inorganic inert particles having the above particle size can be used. Specific examples of such inert fixed particles include silica, alumina, titanium oxide, magnesium carbonate, acrylic resin powder, styrene resin powder, and magnetic powder, but in general, the above-mentioned magnetic powder, particularly fine particles. Preference is given to using ferrosoferric oxide (magnetite). This is because the magnetic powder existing on the surface of the toner particles also effectively acts on the toner scattering. Such spacer particles may be externally added in an amount of 10% by weight or less, preferably 0.1 to 10% by weight, and most preferably 0.1 to 5% by weight based on the total weight of the toner. When used in excess of this, the image density is reduced. When magnetic powder is used as the spacer particles, when the magnetic powder is internally added to the toner particles, the total amount of the magnetic powder and the internally added magnetic powder is 10% by weight or less based on the fixing resin medium. Is good. This is because, if this total amount becomes excessive, the image density will also decrease.

When the fluidity improver and the spacer particles are externally added to the toner, the fluidity improver and the spacer particles are previously intimately mixed under pulverizing conditions, and this mixture is added to the toner to thoroughly disintegrate the toner. Good to do. As a result, these external additives adhere to the surface of the toner particles, that is, are carried in contact with the surface of the toner particles, or fixed in a state where they are partially driven into the surface of the particles.

(Magnetic Carrier) As the magnetic carrier particles used in combination with the above-mentioned toner, those known per se can be used, but preferably, the following formula (7): MOFe ₂ O ₃ (7) ) In the formula, M is Cu, Zn, Fe, Ba, Ni, Mg, M
a magnetite (M = F) which is at least one metal selected from the group consisting of n, Al and Co.
e), ferrite (M is other than Fe), and among them, M is at least one of Cu, Zn, Mg, Mn, and Ni, preferably a soft ferrite containing two or more, for example, copper-zinc-magnesium ferrite. Sintered ferrite particles, especially spherical particles are preferred.

Since these magnetic carrier particles show little change in electric resistance due to environmental changes or changes over time, they exhibit stable charging properties, and the magnetic brush has soft ears,
This is advantageous in that white streaks such as traces of a magnetic brush are not generated in the formed image. The average spherical diameter of the magnetic carrier is generally 30 to 200 μm, especially 50 to 150 μm.
m is preferable, and the saturation magnetization is 30 to 7
0 emu / g, especially 45 to 65 emu / g, and volume resistivity of 10 5 to 10 9 Ω · cm, especially 10 6 to 10 8 Ω
・ It should be in the cm range.

Further, the magnetic carrier particles can be used by coating them with various kinds of thermoplastic resins or thermosetting resins, using the core as the core. For example, as the thermoplastic resin, there is a thermoplastic acrylic resin, a thermoplastic styrene-acrylic resin, a polyester resin, a polyamide resin, an olefin copolymer resin, or the like, and as the thermosetting resin, a modified or unmodified silicone resin, Examples include thermosetting acrylic resin, thermosetting styrene-acrylic resin, phenol resin, urethane resin, thermosetting polyester resin, epoxy resin, amino resin, fluororesin, and melamine resin. With such a resin coat, the occurrence of spent can be more effectively avoided. Generally speaking, the amount of resin coating is preferably 0.001 to 2.5 parts by weight, particularly 0.005 to 2.0 parts by weight, per 100 parts by weight of the core particles.

Further, in the present invention, it is preferable to introduce a cationic polar group into the above coating resin. That is, by providing the resin coating layer having a cationic polar group, the positive charging property of the carrier is improved, and thus the negative charging property of the toner can be further improved. Such cationic polar groups include basic nitrogen-containing groups such as primary, secondary or tertiary amino groups, quaternary ammonium groups, amide groups, imino groups, imide groups, hydrazino groups,
Typical examples are guanidino group and amidino group, and amino group and quaternary ammonium group are particularly preferable.

The introduction of the cationic polar group may be carried out, for example, by using the above-mentioned monomer having a cationic group as a monomer component to produce a resin, and by using a silane coupling agent having a cationic group. It can also be introduced by carrying out resin expression processing. As such a silane coupling agent, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, N- Phenyl-γ-aminopropyltrimethoxysilane and the like. Furthermore, the cationic polar group can be introduced into the resin by synthesizing the above coated resin by polymerization using a polymerization initiator having a cationic polar group such as an amidine type azobis compound. These cationic polar groups are generally 1.0 to 2000 mmol, especially 0.5
It is preferable to be in the range of 1 to 1500 mmol.

It is of course possible to mix various additives known per se in the resin coating layer, if necessary, such as silica, alumina, carbon black, fatty acid metal salts, silane coupling agents and silicone oil. Is.

The resin coating of the carrier particles to be the core is
It can be carried out by a method known per se, for example, by dissolving the above-mentioned coat resin in a suitable solvent and using this resin solution, a dipping method, a spray method, a fluidized bed method, a moving bed method, a rolling bed method, etc. Thus, resin coating can be performed. When the thermosetting resin is coated, the resin may be cured by heating or the like after the coating is performed by the above method using a solution of an uncured resin or an oligomer.

Further, in the present invention, it is also possible to use a binder type carrier formed by dispersing magnetic powder in a binder resin. As such magnetic powder, the above-mentioned magnetic powder, particularly magnetite, can be preferably used, and the particle size is 2 μm or less, particularly 0.05 to 1.0 μm.
It should be in the range of. This magnetic powder is a binder resin 100
150 to 900 parts by weight, especially 250 to 6 parts by weight
It is preferably used in an amount of 00 parts by weight.

The binder resin may be a thermoplastic resin,
Examples of thermosetting resins in the form of uncured or initial condensate, such as vinyl aromatic resins such as polystyrene, acrylic resins, polyvinyl acetal resins, polyester resins, epoxy resins, phenol resins, petroleum resins, polyolefin resins, etc. it can. Among these, styrene resins, acrylic resins, and styrene-acrylic copolymer resins are preferable.

The binder type carrier may be blended with an auxiliary agent known per se, for example, carbon black whose electric resistance is adjusted, a dispersant, a dispersion auxiliary agent, a low molecular weight or high molecular weight charge control agent and the like. it can. Further, similarly to the above, a cationic polar group may be introduced to enhance the positive chargeability of the carrier and improve the negative chargeability of the toner. Even in such a binder type carrier, the average particle size and the like are preferably in the same range as the above-mentioned carrier.

(Two-Component Magnetic Developer) The toner of the present invention is used as a magnetic developer by mixing with the above-mentioned various magnetic carriers, and the mixing ratio of these carriers and the toner is generally 98. : 2 to 90:10 weight ratio, especially 97: 3 to 94: 6 weight ratio.

In the electrostatographic copying method using such a two-component magnetic developer, the electrostatic latent image can be formed by any method known per se. After uniformly charging the conductive layer, it can be imagewise exposed to form an electrostatic latent image. Development of the electrostatic image is easily performed by bringing a magnetic brush of a two-component magnetic developer into contact with the substrate. The toner image formed by the development is transferred onto a copy sheet, and the toner image is fixed by bringing it into contact with a heating roll.

[0065]

【Example】

(Example 1) (Toner composition) (Parts by weight) Fixing resin (Styrene-acrylic copolymer having carboxyl group, acid value 8) 100 Carbon black (pH 3.5, (7-pH) / specific surface area 0.025) 7 Magnetic powder (magnetite) 2 Polyethylene resin (molecular weight 4000) 2 The above composition was melt-kneaded by a twin-screw extruder, and then this kneaded product was pulverized by a jet mill and classified by an air classifier to obtain an average particle size of 10. Toner particles of 0 μm were obtained. To the toner particles, 0.3 parts by weight of hydrophobic silica fine particles having an average particle size of 0.015 μm were added per 100 parts by weight of the toner particles, and 0.3 μm of magnetite as spacer particles was added at a ratio of 0.3 parts by weight. The toner of the present invention was obtained by mixing with a Henschel mixer for 2 minutes. The above toner and average particle size 100μ
and a toner carrier of 3.5
A weight% two-component developer was obtained.

Example 2 1000 parts by weight of spherical ferrite particles having an average particle size of 100 μm were dissolved in 3.5 parts by weight of styrene-acrylic resin and 1.5 parts by weight of methylated melamine resin in 200 parts by weight of toluene. The mixture was added to and mixed with the coating liquid, and the mixture was heated and stirred, the solvent (toluene) was dried and removed from the obtained mixture, and further heat-treated at 200 ° C. for 1 hour to obtain resin-coated carrier particles. A two-component magnetic developer having a toner concentration of 3.5% by weight was obtained in exactly the same manner as in Example 1 except that the resin-coated carrier particles were used.

Example 3 Amino group-containing styrene-acrylic resin 100 parts by weight Magnetite (magnetic powder) 400 parts by weight Carbon black (pH = 7) 5 parts by weight was melt-kneaded by a twin-screw extruder, and then this kneading. The product was pulverized by a jet mill and classified by an air classifier to obtain 80 μm binder type carrier particles. A two-component magnetic developer having a toner concentration of 5.0% by weight was obtained in exactly the same manner as in Example 1 except that the binder type carrier particles in which the magnetic powder was dispersed in the resin were used.

Comparative Example 1 A toner and a developer were prepared in the same manner as in Example 1 except that a styrene-acrylic copolymer having no carboxyl group in the resin was used as the fixing resin.

(Comparative Example 2) As carbon black, p
A toner and a developer were prepared in the same manner as in Example 1 except that an acid-free product having H of 9 and (7-pH) / specific surface area-0.013 was used.

Comparative Example 3 A toner and a developer were prepared in the same manner as in Example 1 except that the polyethylene resin was not contained.

(Comparative Example 4) A toner and a developer were prepared in the same manner as in Example 1 except that 7 parts by weight of a polyethylene resin was contained.

Comparative Example 5 A toner and a developer were prepared in the same manner as in Example 1 except that 2 parts by weight of a polyethylene resin having a molecular weight of 800 was contained.

Comparative Example 6 A toner and a developer were prepared in the same manner as in Example 1 except that 2 parts by weight of a polyethylene resin having a molecular weight of 9000 was contained.

(Evaluation Test) The toner and the developer obtained in each of the examples and the comparative examples were evaluated by using a remodeled electronic copying machine (trade name "DC-7085") manufactured by Mita Kogyo Co., Ltd. for 100,000 sheets. The following items were evaluated by copying. The original used for copying was a character original having an area ratio of black portion of 8%, and the original sampled for every predetermined number of sheets had an area ratio of black portion including black solid portion of 15%. Each test method is as follows.

(A) Image Density (ID) The density of black solid parts in up to 100,000 copied images for each predetermined number of sheets is measured by a reflection densitometer (model number "TC-6D" manufactured by Tokyo Denshoku Co., Ltd.). It was measured using.

(B) Fog Density (FD) The density of the non-image area was measured with a reflection densitometer (model number "TC-6D" manufactured by Tokyo Denshoku Co., Ltd.), and the base paper (paper density before copying) was measured.
Expressed as the difference between Table 1 shows the evaluation results.

(C) Transfer Efficiency The amount of toner in the toner hopper before the start of copying and the amount in the toner hopper after copying a predetermined number of sheets were measured, and the toner consumption amount was calculated from the difference. On the other hand, the amount of toner collected in the cleaning process is measured during copying of a predetermined number of sheets,
The amount of toner collected was obtained. From these values, the toner transfer efficiency was calculated for every 20,000 sheets by the following formula. Table 1 shows the evaluation results
Shown in

(D) Toner scattering The toner scattering state in the copying machine at the end of copying 100,000 sheets was visually observed and evaluated according to the following criteria. Table 2 shows the evaluation results. ○: No toner scattering ×: Toner scattering

(E) Fixing Rate (Fixability) A bottom of 400 g has a flat weight, and the exposed bottom is uniformly spread, and the solid black portion of the image is rubbed 5 times at a constant speed. The ID before rubbing and the ID after rubbing were measured, and the peeling rate was determined as the fixing rate. The fixing rate was evaluated according to the following criteria. Table 1 shows the evaluation results
Shown in ○: 90% or more △: 80% or more and less than 90% ×: less than 80%

(F) Spent amount The developer sampled every predetermined number of sheets is placed on a 400-mesh screen, and the toner and the carrier are separated from the bottom by suction with a blower. 5g of carrier remaining on the sieve
Is placed in a beaker, and toluene is further added to the beaker to disperse the toner adhering to the carrier surface. Then, the toluene solution is dropped from under the beaker while the carrier is attracted by the magnet. After repeating this several times until the toluene becomes colorless, the toluene is dried in an oven and the weight is measured. The difference between the weight put in the beaker and the weight after drying is the amount of spent. Spent amount is 1g carrier
It is expressed in mg of spent toner that has been attached. Table 1 shows the evaluation results.

(G) Toner charge amount 200 mg of the developer was used as a "blow-off powder charge amount measuring device".
(Manufactured by Toshiba Chemical Co., Ltd.) was measured by a conventional method, and the charge amount was expressed per 1 g of toner. Table 1 shows the evaluation results.

(H) Durability Copying is performed using a character original having an area ratio of black portion of 8%.
The toner transfer efficiency was calculated from the toner consumption amount for every 20,000 copies and the collected toner amount. The durability was evaluated based on the number of copies when the transfer efficiency first became less than 70%.

[0083]

[Table 1]

[0084]

According to the present invention, in a two-component magnetic developer toner, a copolymer resin or resin composition having an anionic polar group is used as a fixing resin medium and dispersed in the resin medium. As the carbon black to be used, one having a pH of less than 7 and a ratio of (7-pH) / specific surface area (m ² / g) of 0.010 to 0.050 is used, and thereby a negative charge control agent is blended. In this way, it is possible to secure a sufficient amount of toner charge for development, eliminate the transfer of the charge control agent to the carrier surface and the charging failure due to this spent, and stabilize the toner charging performance for a long time. It was possible to extend the life of the toner and the carrier. Further, the number average molecular weight is 1,000 to 7,000.
By fixing a predetermined amount of the above polyethylene resin in the toner, the fixability could be improved.

[Brief description of drawings]

Figure 1: Chromium complex salt dye (2: 1 type) as charge control agent
3 is an absorbance curve at a wavelength of 200 to 700 nm of an extraction liquid obtained by extracting a toner containing a toner with methanol.

FIG. 2 Wavelength 200 to 700 nm of a methanol extract of toner using a salicylic acid metal complex as a charge control agent.
It is an absorbance curve in.

FIG. 3 is a diagram showing a carrier used in the measurement of FIG. 1 as a two-component magnetic developer and a carrier in which charging failure is caused by a spent is similarly extracted with methanol, and the absorbance of the extract at a wavelength of 200 to 700 nm. It is the graph which measured the curve.

FIG. 4 is a graph plotting a relationship between a mixing time and a spent amount when a mixture of a toner containing a charge control agent and a magnetic carrier and a mixture of a toner containing no charge control agent and a magnetic carrier are mixed. Is.

FIG. 5 is a graph in which the relationship between the mixing time and the charge amount is plotted when a mixture of a toner containing a charge control agent and a magnetic carrier and a mixture of a toner not containing a charge control agent and a magnetic carrier are mixed. Is.

FIG. 6 is a graph showing the relationship between the amount of spent spent carrier and the charge control agent in spent toner.

FIG. 7 is a graph showing the relationship between the mixing time and the amount of spent when the individual components in the toner are mixed with the magnetic carrier.

FIG. 8 is an explanatory diagram illustrating the occurrence of charging failure due to spent generation in a conventional two-component magnetic developer.

FIG. 9 is an absorbance curve at a wavelength of 200 to 700 nm in an extract obtained by extracting the toner of the present invention with methanol.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical indication location G03G 9/113 G03G 9/10 331 351 (72) Inventor Hideaki Kawada 1-2-2 Tamatsukuri, Chuo-ku, Osaka City Mita Engineering Co., Ltd. (72) Inventor Yoshiteru Hatase 1-2-2 Tamatsukuri, Chuo-ku, Osaka Mita Engineering Co., Ltd. (72) Tomohide Iida 1-2-2 Tamatsukuri, Chuo-ku, Osaka Mita Kogyo (72) Inventor Eiichi Tamura 1-2-2 Tamatsukuri, Chuo-ku, Osaka Mita Kogyo Co., Ltd.

Claims (6)

[Claims] 1. A negatively chargeable two-component magnetic developer toner comprising carbon black dispersed in a fixing resin medium, wherein the fixing resin medium is a free or neutralized anionic polar group. In the styrene-acrylic copolymer resin or resin composition having the above, the acid value of the anionic polar group measured in the form of free acid is in the range of 4 to 30, and the number average molecular weight is 1000.
0.5 to 5 parts by weight per 100 parts by weight of the fixing resin medium, and the carbon black has a pH of less than 7 and (7-p
H) / specific surface area (m ² / g) is 0.010 to 0.05
0 to 4 and 1 to 4 per fixing resin medium
A toner for a two-component magnetic developer, which is blended in an amount of 5% by weight. 2. The toner according to claim 1, wherein the extract obtained by extracting the toner with methanol has a substantially zero absorbance in the wavelength region of 400 to 700 nm and no absorption peak in the region of 280 to 350 nm. 3. The resin medium 1 is used as the fixing resin medium.
The toner according to claim 1, which contains 0.1 to 5 parts by weight of magnetic powder per 100 parts by weight. 4. The volume-based average particle diameter of the toner particles is 5
2. The toner according to claim 1, wherein spacer particles having a volume-based average particle diameter of 0.05 to 1.0 μm are attached to the surface of the toner particles. 5. A two-component magnetic developer comprising the toner according to claim 1 and a resin-coated magnetic carrier. 6. A two-component magnetic developer comprising the toner according to claim 1 and a magnetic carrier formed by dispersing magnetic powder in a resin.