JPH0483261A - Electrophotographic developer - Google Patents

Abstract

PURPOSE:To stabilize an electrostatic charge characteristic by limiting the ratio of the acryl component in a resin for fixing of a toner and the coating resin of a carrier within a prescribed range and incorporating dodecyl methacrylate into the coating resin of the carrier. CONSTITUTION:This developer consists of the toner consisting of a styrene/ acrylic copolymer having the ratio occupied by the acryl component within the 10 to 30wt.% range as the resin for fixing and the carrier which contains at least the dodecyl methacrylate and is coated with a styrene/acrylic copolymer having the ratio occupied by the acryl component within the 70 to 90wt.% ratio as the coating resin. The ratio CA/TA of the content ratio TAwt.% of the acryl component in the resin for fixing and the content ratio CAwt.% of the acryl component in the coating resin is within the range of 3<CA/TA<6. The electrophotographic developer having always the stable electrostatic charge characteristic is obtd. in this way.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an electrophotographic developer, and more particularly to a toner used in image forming apparatuses such as electrostatic copying machines and laser beam printers. The present invention relates to a two-component electrophotographic developer comprising: and a carrier.

<Prior Art> In the image forming apparatus described above, an electrophotographic developer is brought into contact with an electrostatic latent image formed by exposing the surface of a photoconductor using a developing device, and the toner in the electrophotographic developer is After electrostatic deposition and visualization of the electrostatic latent image as a toner image,
Image formation is performed by transferring this toner image from the surface of the photoreceptor onto paper and fixing it.

A two-component developer is generally used as an electrophotographic developer, which includes a toner and a carrier that holds the toner electrostatically by triboelectrically charging it and circulates within a developing device.

The toner used is one in which a fixing resin is blended with a coloring agent such as carbon black, a charge control agent, etc., and then granulated to a predetermined particle size.

On the other hand, as a carrier, particles such as ferrite are used as a carrier core material and the surface is coated with a coating resin for the purpose of controlling the charge amount and polarity of the toner, improving the humidity dependence of the charge amount, and preventing filming. is preferably used.

As the fixing resin and coating resin, styrene-acrylic copolymers are preferably used from the viewpoint of ease of handling.

In the above-mentioned styrene-acrylic copolymer, the content ratio of the styrene component and the acrylic component influences the mechanical properties and the performance as a developer, such as the fixability of the toner to paper and the offset property.

For this reason, in the toner fixing resin and the carrier coating resin, the content ratios of the styrene component and the acrylic component are set in consideration of the above-mentioned characteristics.

<Problem to be Solved by the Invention> However, with conventional electrophotographic developers, the rise in charging characteristics is unstable when the toner and carrier are stirred and mixed to be charged, such as during manufacturing or toner replenishment. or
There is a problem in that charging characteristics deteriorate over time and become unstable due to repeated development operations.

When the charging characteristics become unstable, there are problems in that the image density becomes unstable and the image becomes foggy due to toner scattering.

According to the inventors' studies, the charging characteristics of electrophotographic developers are determined by the functional groups (for example, -C) of the acrylic components contained in the fixing resin of the toner and the coating resin of the carrier.
It was found that it is almost determined by the type and amount of the 00-group, etc.). However, as mentioned above, in the past, the ratio of styrene component to acrylic component was determined by considering the mechanical properties of toner and carrier coatings, and charging characteristics were not considered. This is because the characteristics were not stable.

Therefore, in order to stabilize the charging characteristics without impairing the mechanical properties, etc., the range of the content ratio of the acrylic component in the fixing resin of the toner, the range of the content ratio of the acrylic component in the coating resin of the carrier, and An attempt was made to determine the range of the ratio of the above-mentioned content ratios. However, by limiting each of the above ranges, it was not possible to completely stabilize the charging characteristics.

The present invention has been made in view of the above circumstances, and
The object of the present invention is to provide an electrophotographic developer whose charging characteristics are always stable.

Means and Effects for Solving the Problems> In order to solve the above problems, the inventors further investigated the causes of variations in the charging characteristics of electrophotographic developers even if the above range is limited. Ta. As a result, it was found that the main cause of variation in charging characteristics was the coating resin of the carrier.

That is, the above coating resin usually has a resistance adjuster such as carbon black dispersed therein in order to adjust the charging characteristics, but the conventional styrene-acrylic copolymer is not compatible with the above resistance adjuster. Poor solubility makes it impossible to uniformly disperse the resistance adjuster. For this reason, the initial charging characteristics of the coating resin vary, and the charging characteristics become unstable when the toner is stirred and mixed with the carrier and charged during manufacturing, toner replenishment, etc.

In addition, in coating resins made of styrene-acrylic copolymers, the content of the acrylic component is usually set at 70% by weight or more in order to improve charging characteristics, or the content of the acrylic component is A high styrene-acrylic copolymer results in insufficient adhesion to the carrier core material and insufficient film strength of the coating.

For this reason, when the development process is repeated, the coating resin may be scraped off or partially peeled off due to mechanical pressure, impact force, friction, etc. inside the development device, resulting in the surface of the carrier being damaged. The smoothness is lost, the surface condition of the carrier changes, and the charging characteristics become unstable over time.

Therefore, the inventors further investigated the range of the content ratio of the acrylic component and the material of the coating resin, and as a result, completed the present invention.

Therefore, the electrophotographic developer of the present invention contains a toner in which the fixing resin is a styrene-acrylic copolymer in which the proportion of the acrylic component is within the range of 10 to 30% by weight, and at least dodecyl methacrylate. , a carrier coated with a styrene-acrylic copolymer as a coating resin in which the proportion of the acrylic component is within the range of 70 to 90% by weight, and the proportion of the acrylic component in the fixing resin is TA type weight. , content ratio of acrylic component in coating resin C
Ratio to type A weight CA/TA A, 3<CA/TA
<6.

Further, another electrophotographic developer of the present invention is a styrene-acrylic copolymer containing the above toner and at least 2-hydroxyethyl acrylate, and the proportion of the acrylic component is within the range of 70 to 90% by weight. and a carrier coated as a coating resin, and the ratio CA/TA of the content ratio T^ type weight of the acrylic component in the fixing resin to the content ratio CA type weight of the acrylic component in the coating resin is - It is characterized by being within the specified range.

In the electrophotographic developer of the present invention having the above structure, the resistance adjusting agent improves the compatibility between the dodecyl methacrylate contained in the coating resin of the carrier, the coating resin, and the resistance adjusting agent such as carbon black. can be uniformly dispersed.

In addition, in another electrophotographic developer of the present invention, 2-hydroxyethyl acrylate contained in the coating resin of the carrier improves the film strength of the coating and the adhesion of the coating resin to the carrier core material. Therefore, it is possible to prevent the coating from being scraped or partially peeled off.

As the carrier, as mentioned above, dodecyl methacrylate or
-Styrene containing hydroxyethyl acrylate-
A coating resin made of acrylic copolymer is used.

In the present invention, the coating resin containing dodecyl methacrylate may also contain 2-hydroxyethyl acrylate, and conversely, the coating resin containing 2-hydroxyethyl acrylate may contain dodecyl methacrylate.

In the styrene-acrylic copolymer for coating resin, the proportion of the acrylic component must be within the range of 70 to 90% by weight.

If the content of the acrylic component is less than 70% by weight, the charging properties (charging properties) that charge the toner by stirring and mixing with the carrier, especially the charging properties at the time of start-up, will deteriorate, and if it exceeds 90% by weight, the coating resin will deteriorate. The adhesion to the carrier core material and the strength of the coating will decrease.

In the case of the above styrene-acrylic copolymers containing dodecyl methacrylate, the proportion of dodecyl methacrylate in the acrylic component should be 5% by weight or less, especially within the range of 0.1 to 2% by weight. preferable.

If the content of dodecyl methacrylate in the acrylic component is less than 0.1% by weight, the compatibility between the coating resin and the resistance adjuster such as carbon black may decrease, and the resistance adjuster may not be able to be uniformly dispersed. . on the other hand,
If the content of dodecyl methacrylate exceeds 5% by weight, the moisture resistance will decrease, the charging characteristics at the time of startup will deteriorate, and the amount of charge may decrease significantly due to changes over time.

In addition, among styrene-acrylic copolymers containing 2-hydroxyethyl acrylate, the proportion of 2-hydroxyethyl acrylate in the acrylic component is 5% by weight or less, particularly 0.1 to 2% by weight. It is preferable that it is within the range of .

If the content of 2-hydroxyethyl acrylate in the acrylic component is less than 0.1% by weight, the adhesion of the coating resin to the carrier core material and the film strength of the coating may become insufficient. On the other hand, if the content of 2-hydroxyethyl acrylate exceeds 5% by weight, it may adversely affect the constitutional properties and charging characteristics.

In addition to styrene, the styrene components constituting the styrene-acrylic copolymer include vinyltoluene, α-
Styrenic monomers such as methylstyrene can also be used. As the acrylic component other than dodecyl methacrylate and 2-hydroxyethyl acrylate, an acrylic monomer represented by the following general formula [I] can be used.

In the formula, R1 is a hydrogen atom or a lower alkyl group, and R2 is a hydrogen atom, a hydrocarbon group having up to 12 carbon atoms, a hydroxyalkyl group, a vinyl ester group, or an aminoalkyl group.

The acrylic monomers represented by the above general formula (11) include acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, and phenyl acrylate. , ethyl methacrylate, methyl methacrylate,
Hexyl methacrylate, 2-ethylhexyl methacrylate, ethyl β-hydroxyacrylate, propyl γ-hydroxyacrylate, butyl δ-hydroxyacrylate, ethyl β-hydroxymethacrylate, propyl aminoacrylate, γ-N, N -diethylaminopropyl acrylate, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, and the like.

The most preferred styrene-acrylic copolymer for the coating resin is a styrene/ethyl methacrylate copolymer, particularly 10 to 30% by weight of styrene, 70 to 90% by weight of ethyl methacrylate, dodecyl methacrylate or 2-hydroxyethyl. Those containing 0.1 to 5% by weight of acrylate are preferably used. Among acrylic monomers other than dodecyl methacrylate and 2-hydroxyethyl acrylate, the above-mentioned ethyl methacrylate (ethyl methacrylate) has excellent stability in the start-up of charging characteristics, and also has less deterioration of charging characteristics over time. Excellent preventive action.

The above copolymer can be produced from each monomer by a conventionally known polymerization method such as a solution polymerization method.

In the above coating resin, as a resistance adjuster,
About 0.5 to 5% by weight of carbon black and about 0.5 to 3% by weight of a metal complex or the like as a charge control agent may be blended.

As carrier core materials, particles of iron, oxidized iron, reduced iron, magnetite, copper, silicon steel, ferrite, nickel, cobalt, etc., particles of alloys of these materials with manganese, zinc, aluminum, etc., iron- Particles of nickel alloy, iron-cobalt alloy, etc., particles of the above various particles dispersed in binder resin, titanium oxide, aluminum oxide, copper oxide,
Ceraminox particles such as magnesium oxide, lead oxide, zirconium oxide, silicon carbide, magnesium titanate, barium titanate, lithium titanate, lead titanate, lead zirconate, lithium niobate, ammonium dihydrogen phosphate (NR1R2PO4 ), potassium dihydrogen phosphate (KH2P 04 ), Rochelle salt, and other particles of high electrical conductivity substances. Among these, iron powder such as iron oxide and reduced iron, and ferrite are preferable because they have excellent image characteristics and are inexpensive.

As a method for coating the surface of the carrier core material with the coating resin made of the styrene-acrylic copolymer, any known method such as a fluidized bed method or a transfer layer method can be employed.

The particle size of the carrier core material is 30 to 200 μm, preferably 5
A value of about 0 to 130 is good, and the coating thickness is 0.1
~5 μm, preferably about 0.5 to 3 μm.

Together with the carrier, the toner constituting the electrophotographic developer of the present invention contains a fixing resin made of a styrene-acrylic copolymer containing a colorant, a charge control agent, a release agent (offset prevention agent), etc. It is manufactured by blending additives and granulating it to an appropriate particle size.

The styrene-acrylic copolymer used as a fixing resin is
It consists of the styrene monomer and acrylic monomer illustrated above.

In the styrene-acrylic copolymer for fixing resin, the proportion of the acrylic component must be within the range of 10 to 30% by weight.

If the content of the acrylic component is less than 10% by weight, there is a risk that charging characteristics and fixing properties to paper will deteriorate;
If the toner exceeds this value, there is a risk that the environmental resistance, that is, the resistance of charging characteristics to humidity and temperature, may deteriorate, and at the same time, so-called reverse polarity toner, which is charged in the opposite polarity to the required polarity, is likely to be generated.

The most preferable styrene-acrylic copolymer for the fixing resin is a styrene/methyl methacrylate/butyl acrylate copolymer, especially when styrene is 75 to 8
5% by weight, 0.5-5% by weight of methyl methacrylate,
A material containing 10 to 20% by weight of butyl acrylate is preferably used.

Examples of the coloring agent include various colored pigments, extender pigments, conductive pigments, magnetic pigments, photoconductive pigments, and the like. These may be used singly or in combination of two or more depending on the purpose.

As the colored pigment, the following are preferably used.

Furnace black, channel black, thermal,
Gas black, oil black, carbon black such as acetylene black, lamp black, aniline black.

White Zinc white, titanium oxide, antimony white, zinc sulfide.

Red Red Red Garla, Cadmium Red, Red Lead, Mercury Sulfide, Permanent Red 4R1 Resole Red, Pyrazolone Red, Watching Red Calcium Salt, Lake Red D1
Brilliant Carmine 6B, Eosin Lake, Rhodamine Lake B1 Alizarin Lake, Brilliant Carmine 3B.

Orange red mouth yellow lead, molybdenum orange, permanent orange GTR, pyrazolo orange, palkan orange, indanthrene brilliant orange RK1 benzidine orange G1 indanthrene brilliant orange GK0 Xianlu yellow lead, zinc white, cadmium yellow, yellow iron oxide, Mineral Futist Yellow, Ni-Noketsu Titanium Yellow, Navels Yellow, Naphthol Yellow 81 Hanser Yellow G, Hansa Yellow 10G1 Hengejin Yellow G1 Hengejin Yellow GR, Quinoline Yellow Lake, Nono Manent Yellow NCG, Tart Radin rake.

Green chrome green, chromium oxide, pigment green B1
Malachite Green Lake, Final Yellow Green G0 Blue Navy Blue, Cobalt Blue, Alkaline Blue Lake, Victoria Blue Lake, Phthalocyanine Blue Partially Chlorinated, Fast Sky Blue, Indanthrene Blue BC
0 Purple Manganese Purple, First Violet B1 Methyl Violet Lake.

Examples of extender pigments include palite powder, barium carbonate, clay silica, white carbon, talc, and alumina white.

Examples of the conductive pigment include conductive carbon black and aluminum powder.

Magnetic pigments include various ferrites, such as triiron tetroxide (Fe i O4), iron sesquioxide (γ-F@20s), zinc iron oxide (ZnFez O,), and yttrium iron oxide (Y 3 Fe, O+□). ), iron cadmium oxide (CdFe204), iron gadolinium oxide (Gd3Fe504), iron oxide steel (CuFe2O
4), iron oxide complex (PbFs 12019), neodymium iron oxide (NdFa O3), barium iron oxide (BaFe 12019), magnesium iron oxide (1'bFe204), iron manganese oxide (r
'lTlFe 204), lanthanum iron oxide (LzFe
O3), iron powder, cobalt powder, nickel powder, etc.

Examples of photoconductive pigments include zinc oxide, selenium, cadmium sulfide, and cadmium selenide.

The colorant is used in an amount of 1 to 30 parts by weight, preferably 2 to 20 parts by weight, based on 100 parts by weight of the binder resin.

As the charge control agent, two types of charge control agents are used, one for positive charge control and one for negative charge control, depending on the polarity of the toner.

As a charge control agent for positive charge control, an organic compound having a basic nitrogen atom, such as a basic dye, aminovirine,
Examples include pyrimidine compounds, polynuclear polyamino compounds, aminosilanes, and fillers surface-treated with the above compounds.

Examples of the charge control agent for negative charge control include compounds containing a carboxy group (for example, alkyl salicylic acid metal chelates, etc.), metal complex dyes, fatty acid soaps, naphthenic acid metal salts, and the like.

The charge control agent is used in an amount of 0.1 to 100 parts by weight of the binder resin.
It is used in a proportion of 10 parts by weight, preferably 0.5 to 8 parts by weight.

Examples of mold release agents (offset inhibitors) include aliphatic hydrocarbons, aliphatic metal salts, higher fatty acids, fatty acid esters or partially saponified products thereof, silicone oil, various waxes, and the like. Among them, those with a weight average molecular weight of 10
Aliphatic hydrocarbons having a molecular weight of about 00 to 10,000 are preferred.

Specifically, low molecular weight polypropylene, low molecular weight polyethylene, paraffin wax, low molecular weight olefin polymers consisting of olefin units having 4 or more carbon atoms, etc.
A species or a combination of two or more species are suitable.

The mold release agent is used in an amount of 0.1 to 10 parts by weight per 100 parts by weight of the binder resin.
It is used in proportions of 0.5 to 8 parts by weight, preferably 0.5 to 8 parts by weight.

The toner is prepared by pre-kneading the above-mentioned components homogeneously using a dry blender, Henschel mixer, ball mill, etc.
- After uniformly melting and kneading using a kneading device such as a shaft or twin-screw extrusion kneader, the resulting mixed material is cooled and pulverized;
In addition to being produced by classification as necessary, it can also be produced by a suspension polymerization method or the like.

The particle size of the toner is 3 to 35 μm, preferably 5 to 25 μm.
It is.

The surface of the toner can be sprinkled with a conventionally known surface treatment agent such as inorganic particles such as hydrophobic silica particles or fluororesin particles to improve fluidity.

The above-mentioned toner and carrier have a ratio CA/T9 of the content ratio TA type weight of the acrylic component in the fixing resin of the toner to the content ratio CA type weight of the acrylic component in the coating resin of the carrier, 3 < CA / It must be within the range of T A < 6.

When the ratio CA/TA is 3 or less, the proportion of the acrylic component in the coating resin of the carrier becomes relatively small, the chargeability of the carrier decreases, and image fogging occurs due to toner scattering. On the other hand, the above ratio CA
When /TA is 6 or more, the proportion of the acrylic component in the coach ink resin of the carrier becomes relatively large, the chargeability of the toner becomes too high, and the image density decreases.

The mixing ratio of the toner and carrier can be changed as appropriate depending on the model of the image forming apparatus used.

<Examples> The present invention will be described below based on Examples and Comparative Examples.

Examples 1-10. Comparative Examples 1 to 10 The following toners and carriers were mixed in the combinations shown in Table 1 at a weight ratio of 3.5:96.5, and a Nauta mixer (trade name: NX manufactured by Honkawa Micron Co., Ltd.) was used. −
By stirring and mixing according to step 3), developers of Examples and Comparative Examples were manufactured.

Toner (al styrene (St)/methyl methacrylate (MMA)/
Butyl acrylate (BA) copolymer [St:MMA:
BA-80:5:15 (weight ratio), acrylic component content T A "20% by weight] 100 parts by weight, 8 parts by weight of carbon black as a coloring agent, 1 part by weight of a negative polar dye as a charge control agent. , and 1 part by weight of low molecular weight polypropylene as an offset inhibitor were mixed, and after melt-kneading, cooling, pulverization, and classification were performed to prepare toner (a) having a median particle size of 12 mm.

Toner Mountain) As a formulation, in place of 100 parts by weight of the copolymer used in the toner (Al), styrene (St)/methyl methacrylate (MMA)/butyl acrylate (BA) copolymer [
St: MMA: BA-88 near: 5 (weight ratio), acrylic component content TA = 12% by weight] 10
A toner (toner pile) was prepared in the same manner as J except that 0 parts by weight was used.

Toner (C1) In place of 1.0 parts by weight of the copolymer used in toner (ω), styrene (St)/butyl acrylate (
BA) Copolymer [St: BA-72:28 (weight ratio), acrylic component content TA-28% by weight] 1
Toner (C1) was prepared in the same manner as toner (al) except that 00 parts by weight was used.

Toner (d+) In place of 100 parts by weight of the copolymer used in toner (al), styrene (St)/methyl methacrylate (MMA)/butyl acrylate (BA) copolymer [
St: MMA: BA-923:5 (weight ratio)
Toner (d+) was prepared in the same manner as toner (ω) except that 100 parts by weight of acrylic component content TA-8% by weight was used.

Carrier (1) Styrene (St)/ethyl methacrylate (EMA)/dodecyl methacrylate (as coating resin)
DMA) copolymer [St:EMA:DMA-18: 8
0:2 (weight ratio), content ratio of acrylic component CA
A mixture of 100 parts by weight of -82% by weight and 2 parts by weight of carbon black as a resistance adjuster was coated on the surface of ferrite as a carrier core material by a fluidized bed method, and the center particle size was 95t13. A carrier (1) with a coating layer having a thickness of 2 μm was prepared.

Carrier (2) In place of 100 parts by weight of the coating resin used in carrier (1), styrene (St)/ethyl methacrylate (EMA)/dodenyl methacrylate (
DMA) copolymer [St:EMA:DMA-29: 7
0:1 (weight ratio), content ratio of acrylic component CA
Carrier (2) was produced in the same manner as Carrier (1) except that 100 parts by weight of the carrier (2) was used.

Carrier (3) In place of 100 parts by weight of the coating resin used in carrier (1), styrene (St)/ethyl methacrylate (EMA)/dodecyl methacrylate (
DMA) copolymer [St:EMA:DMA-10:87
:3 (weight ratio), content ratio of acrylic component CA-90
Weight %] Except for using 100 parts by weight, carrier (
A carrier (3) was produced in the same manner as in 1).

Carrier (4) As a prescription, Coachine 21 used in carrier (1)
In place of 2100 parts by weight of styrene (St)/ethyl methacrylate (EMA) copolymer [St: EMA]
-38: 62 (weight ratio), acrylic component content CA-62% by weight] A carrier [4] was produced in the same manner as carrier (1) except that 100 parts by weight was used.

Carrier (5) In place of 100 parts by weight of the coating resin used in carrier (1), styrene (St)/ethyl methacrylate (EMA)/dodenyl methacrylate (
DMA) copolymer [St:EMA:DMA-8: 90
22 (weight ratio), acrylic component content CA-92% by weight] Except for using 100 parts by weight of the carrier (
A carrier (5) was produced in the same manner as in 1).

Carrier 16) As a prescription, styrene (St)/ethyl methacrylate (HMA)/dodecyl methacrylate (
DMA) copolymer [S t : EMA : DMA-2
A carrier (6) was prepared in the same manner as the carrier (1) except that 8:70:2 (weight ratio) and 1100 parts by weight of the acrylic component content CA-72% by weight were used.

Carrier q) As a formulation, styrene (St)/ethyl methacrylate (EMA)/2-hydroxyethyl acrylate (HEA) copolymer [St :EMA:HE
A carrier (7) was produced in the same manner as carrier (1) except that 100 parts by weight of acrylic component (A-18:80:2 (weight ratio), acrylic component content CA-82% by weight) was used.

Carrier (8) As a formulation, styrene (St)/ethyl methacrylate (EMA)/2-hydroxyethyl acrylate (HE A) copolymer [St:EMA] was used in place of 100 parts by weight of the coating resin used in carrier (1). :HEA
A carrier (8) was prepared in the same manner as the carrier (1), except that -29nia was 0:1 (weight ratio) and the content of the acrylic component was 100 parts by weight of CA-71% by weight.

Carrier (9) As a formulation, in place of 100 parts by weight of the coating resin used in carrier (1), styrene (St)/ethyl methacrylate (EMA)/2-hydroxyethyl acrylate (HEA) copolymer [St:EMA: HEA-
11:87:2 (weight ratio), acrylic component content CA-89% by weight] except that 100 parts by weight was used.
A carrier (9) was produced in the same manner as carrier (1).

Carrier (10) As a recipe, instead of 100 parts by weight of the coating resin used in carrier (1), styrene (St)/ethyl methacrylate (EMA)/2-hydroxyethyl acrylate (HE A) copolymer [St:EMA :HE
Carrier 00) was produced in the same manner as Carrier (1) except that 100 parts by weight of A-28+70:2 (weight ratio) and acrylic component content cA-72% by weight were used.

Carrier (11) As a prescription, Coach 42 F1 used in carrier (1)
Styrene (St)/ethyl methacrylate (EMA)/2-hydroxyethyl acrylate (HEA) copolymer [St:EMA:HEA]
A carrier (11) was produced in the same manner as the carrier (1), except that 100 parts by weight of the acrylic component content CA-62% by weight was used.

Carrier (12) In place of 100 parts by weight of the coating resin used in carrier (1), styrene (St)/ethyl methacrylate (EMA)/dodecyl methacrylate (
DMA)/2-hydroxyethyl acrylate (HE
A) Copolymer [St:EMA:DMA:HEA-20Nia 6:2:2 (weight ratio), acrylic component content C
A carrier (12) was produced in the same manner as carrier (1) except that 100 parts by weight of 80% A-by weight was used.

Carrier (13) In place of 100 parts by weight of the coating resin used in carrier (1), styrene (St)/ethyl methacrylate (EMA)/dodecyl methacrylate (
DMA)/2-hydroxyethyl acrylate) (HE
A) Copolymer [St:EMA:DMA:HEA-12:
82:3:3 (weight ratio), content ratio of acrylic component C
Carrier 13> was prepared in the same manner as Carrier (1) except that 100 parts by weight of A-88% by weight was used.

The following tests were conducted on the electrophotographic developers of the above Examples and Comparative Examples.

Image density test The above electrophotographic developer was used as a start developer in an electrophotographic copying machine (model number DC-5585, manufactured by Sanda Kogyo Co., Ltd.), and the same toner contained in the start developer was used for replenishment. Using it as a toner, 50,000 sheets of black solid manuscript were continuously copied. Then, a total of 51 samples were extracted, including the first copy at the start of copying and one sample for every 1,000 copies.
C-6D), the density of the copied images was measured, and the developer obtained from 50 or more images with an image density of 1.3 or more was
The developer obtained from 40 to 49 sheets was evaluated as Δ, and the developer obtained from 39 sheets or less was evaluated as ×.

Image fog test The electrophotographic developer described above was used as a start developer in the same electrophotographic copying machine as described above, and the same toner contained in the start developer was used as a replenishment toner to produce a black and white original. 50,000 copies were made continuously. Then, a total of 51 samples were extracted, including the first copy at the start of copying and one sample for every 1000 copies, and the density of the blank area of the copied image was measured using the reflection densitometer, and the fog density was determined to be 0.
01 for the developer that produced 50 or more images of ゜003 or less.
The developer obtained from 40 to 49 sheets was evaluated as Δ, and the developer obtained from 39 sheets or less was evaluated as ×.

Resolution test The above electrophotographic developer was used as a start developer in the same electrophotographic copying machine as above, and the same toner contained in the start developer was used as a replenishment toner to meet JIS B 7174. 50,000 consecutive copies of resolution measurement chart conforming to the regulations of 1962 were made. Then, a total of 51 samples were extracted, including the first copy at the start of copying and one sample for every 1000 copies, and the resolution of the copied image (book/dragon) was determined, and an image with a resolution of 4.5 lines/m+s was obtained. The developer obtained from 50 sheets or more was evaluated as 0, the developer obtained from 40 to 49 sheets was evaluated as Δ, and the developer obtained from 39 sheets or less was evaluated as ×.

Toner Scattering Test The margin area of the 50,000th copy image used for the above fog density measurement and the inside of the copying machine after 50,000 copies were made were observed. The case where almost no toner scattering was observed either in the margin of the copied image or inside the copying machine was evaluated as o1, and the case where it was observed in at least one of the margin of the copied image and the inside of the copying machine was evaluated as ×. .

Measurement of charge amount During continuous copying of 50,000 sheets in the above fog density measurement, the developer in the developing device was sunblinked at the start of copying and every 10,000 sheets, and the charge amount of the toner (-μC/g
) was measured by the blow-off method.

The above results are shown in Table 1.

From the results in Table 1 above, in the system containing carrier coating resin and todenyl methacrylate, CA
In Comparative Example 1 where /TA exceeded 6°, a decrease in image density was observed. Further, in Comparative Example 1, the toner charge amount was not constant during continuous copying, and the charge amount increased almost unilaterally. On the other hand, in Comparative Example 5 in which CA/TA was less than 3, toner scattering, fogging, and a decrease in resolution occurred due to the decrease in chargeability, and variations were observed in the toner charge amount during continuous copying. In Comparative Example 2 in which a toner with a TA of less than 10% by weight was used and a CA/TA of more than 6, the image density was significantly lowered and the toner charge amount varied greatly during continuous copying. In addition, after continuous copying of around 40,000 copies, a decrease in the amount of charge was observed, and as a result,
Toner scattering, fogging, and decreased resolution occurred. Further, a toner containing less than 10% by weight of TA and 9% by weight of CA or
In Comparative Example 4, in which a carrier exceeding 0 was used and CA/TA exceeded 6, the toner charge amount decreased almost unilaterally during continuous copying, resulting in toner scattering, fogging, and resolution reduction due to the decrease in charging property. or occurred. In Comparative Example 3 in which a carrier containing dodenyl methacrylate and containing less than 70% by weight of CA was used, the toner charge amount fluctuated during continuous copying, and all of the above characteristics were insufficient. Ta. On the other hand, Examples 1 to 4, which are the configurations of the present invention, are excellent in each of the above characteristics, and
It was found that the amount of charge was always stable even when 50,000 copies were made continuously. In addition, the carrier of the above-mentioned developer is
When observed using an electron microscope at a magnification of 1,000 times before use and after continuous copying of 50,000 sheets, the carriers of Comparative Examples 3 and 4 showed that the coating resin did not wear off after continuous copying of 50,000 sheets. Although it was observed that the carriers were significantly deteriorated due to peeling and peeling, almost no deterioration was observed in the carriers of each example even after continuous copying of 50,000 sheets.

In a system where the carrier coating resin contains 2-hydroxyethyl acrylate, CA/TA
In Comparative Example 6, in which the value exceeds 6, a decrease in image density was observed. On the other hand, in Comparative Example 9 where CA/TA was less than 3, toner scattering, fogging, and resolution decreased due to the decrease in chargeability, and the toner charge amount during continuous copying decreased almost unilaterally. In Comparative Example 7 in which a toner with a TA of less than 10% by weight was used and a CA/TA of more than 6, not only was the image density significantly lowered, but also the amount of toner charge during continuous copying increased significantly. In addition, a decrease in resolution also occurred. In Comparative Example 8 in which a carrier containing less than 70% by weight of CA was used, the amount of toner charge during continuous copying was significantly reduced, and this caused toner scattering, fogging, and a reduction in resolution. On the other hand, Examples 5 to 8, which are the configurations of the present invention, are excellent in each of the above characteristics and have 5.
It was found that the amount of charge remained stable even after continuous copying of 10,000 sheets.

In Comparative Example 10, in which a carrier coating resin contained dodecyl methacrylate and 2-hydroxyethyl acrylate, a toner with TA of less than 10% by weight was used, and CA/TA exceeded 6. The toner charge amount decreased almost unilaterally, and fogging and toner scattering occurred accordingly. On the other hand, both Examples 9 and 10, which are the configurations of the present invention, are excellent in each of the above characteristics, and the amount of charge remains stable even after continuous copying of 50,000 sheets. did.

<Effects of the Invention> The electrophotographic developer of the present invention is configured as described above, and the ratio of the acrylic component in the toner fixing resin and the carrier coating resin is limited within a predetermined range, and the carrier The coach ink resin contains dodecyl methacrylate, which improves compatibility with resistance modifiers such as carphone black, disperses the resistance modifiers uniformly, and equalizes the initial charging characteristics. The charging characteristics are always stable.

In addition, in other electrophotographic developers of the present invention, the upper g
In addition to limiting the ratio of the acrylic component in the toner fixing resin and the carrier coating resin to within a predetermined range, the carrier coating resin is used to increase the film strength of the coating and to improve the adhesion of the coating resin to the carrier core material. Since it contains 2-hydroquine ethyl acrylate which increases the charging properties, the charging properties are always stable.

Claims (1)

[Scope of Claims] 1. A toner in which a fixing resin is a styrene-acrylic copolymer in which an acrylic component accounts for 10 to 30% by weight, and a toner containing at least dodecyl methacrylate and in which an acrylic component accounts for and a carrier coated as a coating resin with a styrene-acrylic copolymer having a proportion within the range of 70 to 90% by weight, and the content proportion T of the acrylic component in the fixing resin.
The ratio C_A/T_A of _A weight % and the content ratio C_A weight % of the acrylic component in the coating resin is,
An electrophotographic developer in which the range of 3<C_A/T_A<6 is satisfied. 2. The electrophotographic developer according to claim 1, wherein the coating resin contains ethyl methacrylate. 3. A toner in which the fixing resin is a styrene-acrylic copolymer in which the proportion of the acrylic component is within the range of 10 to 30% by weight, and a toner containing at least 2-hydroxyethyl acrylate and the proportion of the acrylic component in the range of 70 to 30% by weight. ~9
a carrier coated with a styrene-acrylic copolymer as a coating resin in the range of 0% by weight, the content of the acrylic component in the fixing resin T_A% by weight, and the content of the acrylic component in the coating resin. Ratio C_A/ to proportion C_A weight%
An electrophotographic developer in which T_A is within the range of 3<C_A/T_A<6. 4. The electrophotographic developer according to claim 3, wherein the coating resin contains ethyl methacrylate.