JPH0456966A - Two-component developer - Google Patents

Abstract

PURPOSE:To suppress the formation of image voids by carrier splashing by specifying the (resistance value of the core material of the carrier)/(the resistance value of the carrier) to >=0.020 and constituting a toner of a styrene/ acrylic thermoplastic resin having a specific mol. wt. distribution. CONSTITUTION:The (resistance value of the core material of the carrier)/(the resistance value of the carrier) of the two-component developer consisting of the carrier and the toner contg. a fixing resin component is specified to >=0.020. The fixing resin component of the toner is constituted of the styrene/acrylic thermoplastic resin having the mol. wt. distribution which has the max. value PH of the high mol. wt. on the side nearer the high mol. wt. side than 1X10<5>mol. wt. and the max. value PL of the low mol. wt. in a 2X10<4> to 500mol.wt. range and in which the mol. wt. has the min. value VM between both and the area ratio of valleys by the min. value to the total of the peak area SH of the high mol. wt. and the peak area SL of the low mol. wt. is <=0.30. The image voids by the carrier splashing are prevented in this way and the good-quality images having excellent fixability are obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a two-component developer, and more particularly to a two-component developer used in an image forming apparatus such as an electrostatic copying machine.

[Conventional technology]

Conventionally, in image forming apparatuses such as copying machines that utilize the Carlson process, a charging process is used to uniformly charge a photoreceptor using corona discharge, and an electrostatic charge process in which a document image is exposed to the charged photoreceptor corresponds to the document image. A developing process in which a latent image is developed with a developer to form a toner image, a transfer process in which the toner image is transferred to a base material such as paper, and a fixing process in which the toner image transferred to the base material is fixed to form an image. The so-called Carlson process is widely used.

As the developer used in the developing process, a two-component developer consisting of a carrier and a toner is widely used.

The carrier consists of a carrier core material and a polymeric coating layer covering the surface of the carrier core material.

Further, the toner is generally made of a fixing resin mixed with a coloring agent and a charge control agent, which have a predetermined particle size. Various proposals have been made to improve blocking resistance, impact resistance, offset resistance, etc. while maintaining low-temperature fixing properties by coexisting high-molecular-weight components and low-molecular-weight components in the fixing resin. There is.

[Problem to be solved by the invention]

However, in electrostatic copying using a conventional two-component developer, a phenomenon called carrier fly-off occurs, in which the carrier adheres to the surface of the electrostatic latent image along with the toner, resulting in minute spots appearing in the image area. There have been cases where white spots have occurred. Such white spots are also called carrier fireflies.

The following is presumed to be the cause of such carrier flying.

In other words, due to the edge effect (edge phenomenon) in which the density at the center of the image becomes thinner than at the periphery, the potential around the outside of the image area is lower than the residual potential level. The potential above is the potential difference between the potential around the solid black part of the solid black image and the residual potential ■
1.

On the other hand, in the proximity line image, the potential difference (■2) between the potential between the proximity lines and the residual potential is influenced by the potential around the outside of both proximity lines, and
becomes something bigger than. (■2-2V,). moreover,
In the fine mesh image, the potential difference (3) between the potential of the white portion surrounded by each line and the residual potential is larger than the potential difference (2) of the adjacent line image (V,>V2>V). On the other hand, since a bias voltage of the same polarity as the latent image is applied to the sleeve of the image forming device, carriers that have left the sleeve tend to adhere to the periphery of the image area due to the principle of reversal development, causing carrier flying. do. As is clear from the above description, such carrier jumps tend to occur in the order of mesh images, proximity line images, and solid black images.

SUMMARY OF THE INVENTION An object of the present invention is to provide a two-component developer that prevents the carrier flying phenomenon from occurring and suppresses image area blanking due to carrier flying to such an extent that it does not pose a problem in actual use.

[Means and effects for solving the problem] Carrier flying, where the carrier adheres to the surface of the electrostatic latent image, is caused by the lines of electric force near the photoreceptor and the afterimage that remains in the carrier when the toner is separated from the carrier during development. It is thought that this occurs due to interaction with a counter charge (accumulated charge), and the larger the counter charge, the higher the frequency of carrier jump occurrence.

Conventionally, it has been thought that the magnitude of this counter charge is determined by the resistance value of the entire carrier. but,
As a result of extensive research by the inventors, we found that there is no correlation between the resistance value of the entire carrier and the carrier flyoff, and that the carrier flyoff is determined by the resistance value of the polymer coating layer covering the surface of the carrier and the toner flyoff. We have discovered a completely new fact that the present invention is deeply related to the molecular weight distribution of the fixing resin component.

That is, the larger the resistance value of the coat layer, the more likely the counter charge remains in the coat layer. Carriers with a high counter charge tend to adhere to the surface of the electrostatic latent image, and carrier flying tends to occur.

Further, if a high molecular weight component and a low molecular weight component are used together in the fixing resin for toner, the resin composition in the toner becomes non-uniform and the internal cohesive force decreases. As a result, the I/toner tends to aggregate, so that the toner tends to adhere to one carrier in an aggregated state. When such agglomerated toner is developed, a large counter charge remains in the carrier coating layer, and carrier flying frequently occurs.

Therefore, the two-component developer of the present invention is a two-component developer consisting of a carrier whose surface is covered with a polymer coating layer, and a toner containing at least a fixing resin component. carrier core material resistance value)/(carrier resistance value) is 0.020 or more, and the fixing resin component of the toner has a high molecular weight maximum on the higher molecular weight side than the molecular weight lXl0' in the gel permeation chromatogram. Value, numerator! The molecular weight has a local maximum value in the range of 2 x 104 to 500 and a local minimum value between the two, and the area ratio of the valley due to the minimum value to the sum of the high molecular weight peak area and the low molecular weight peak area is 0°. It is characterized by being a styrene-acrylic thermoplastic resin having a molecular weight distribution of 30 or less.

In such a configuration, r (resistance value of carrier core material)/(
Since it is difficult to measure only the resistance value of the coat layer, the carrier resistance value J is an indirect expression of this value. By setting this (resistance value of carrier core material)/(carrier resistance value) to 0.020 or more, the resistance value of the carrier coating layer becomes small (and the counter charge retention ability in the coating layer is optimized). , carrier flying is prevented.

Furthermore, in the gel permeation chromatogram, the fixing resin component of the toner has a high molecular weight maximum value on the higher molecular weight side than the molecular weight 1X10S, and a molecular weight of 2 x 104 to 500.
has a low molecular weight local maximum value in the range of and a local minimum value between the two, and the area ratio of the valley due to the local minimum value to the sum of the high molecular weight peak area and the low molecular weight peak area is 0.3
By using a styrene-acrylic thermoplastic resin with a molecular weight distribution of 0 or less, especially 0.20 or less, the internal aggregation of the toner resin can be achieved while maintaining both low-temperature fixing properties and anti-offset properties at an excellent level. It is possible to significantly improve the force and prevent toner agglomeration. That is, the thermoplastic resin used as the fixing resin in the present invention has a maximum high molecular weight (Pn) and a maximum low molecular weight (I).
Although there is a significantly large molecular weight difference of 8×10′ or more between the two peaks, both peaks are characterized by a high content of components with a common molecular weight.

In this specification, the valley area ratio (V/
In Figure 2, which explains how to obtain P), this gel permeation chromatogram (GPC) shows a high molecular weight maximum value PH1, a low molecular weight maximum value PL, and a minimum value ■8 between the two. . A high molecular weight peak area SIl is found on the high molecular weight side of this minimum value VM, a low molecular weight peak area S is on the low molecular weight side, and furthermore, the polar settlements P and P
The area Sv of the valley below the straight line connecting L is determined, and S□10SL is calculated from this.

The above peak area to valley area ratio (V/P) represents the degree of approximation of the bimodal molecular weight distribution curve to a quadrilateral shape, and the smaller this value (V/P) is, the more it approximates the quadrilateral shape. It means there is. This also means that the amount of intermediate molecular weight components between the high molecular weight component and the low molecular weight component is within the range that does not impair the range of bimodal properties.

Therefore, as shown in the GPC in Figure 3, by using a resin that has a molecular weight distribution very close to a quadrilateral shape, toner aggregation can be prevented and the proportion of large counter charges remaining in the carrier polymer coating layer can be reduced. As a result, the rate at which carrier jump occurs is reduced.

The present invention will be explained in detail below.

In the carrier of the present invention, any commonly used polymeric material can be used for the carrier core material and the polymeric coating layer covering the surface of the carrier core material.

For example, carrier core materials include iron powder, oxidized iron powder, reduced iron, magnetite, copper, silicon steel, ferrite, nickel, cobalt, alloys of these with manganese, zinc, aluminum, etc., iron-nickel alloys, Magnetic materials such as iron-cobalt alloys and iron-aluminum alloys, particles with magnetic materials dispersed in binder resin, titanium oxide, aluminum oxide, copper oxide, magnesium oxide, lead oxide, zirconium oxide, silicon carbide, and titanic acid. magnesium,
Ceramics such as barium titanate, lithium titanate, lead titanate, lead zirconate, lithium niobate, AD
P (NH, H□po,), KDP (KH2PO4)
, high dielectric constant substances such as Rochelle salt, etc. Among these, iron powders such as iron oxide and reduced iron, and ferrite are preferred because they are inexpensive and have excellent image characteristics.

The carrier core material is not limited to one type, and two or more types may be used in combination.

Further, the particle size of the carrier core material is preferably about 30 to 200 μm, preferably about 50 to 130 μm.

Examples of the polymer material for forming the coat layer include acrylic polymers, styrene polymers, styrene-acrylic polymers, polyethylene, chlorinated polyethylene,
Olefin polymers such as polypropylene, polyvinyl chloride, polyester, unsaturated polyester, polyamide,
Examples include various polymers such as polyurethane, epoxy resin, polycarbonate, silicone resin, polytetrafluoroethylene, polychlorotrifluoroethylene, fluorocarbon resin such as polyvinylidene fluoride, phenol resin, xylene resin, and diallyl phthalate resin. Among these, it is preferable to use acrylic polymers, styrene polymers, styrene-acrylic polymers, silicone resins, or fluorocarbon resins in terms of frictional charging properties with toner and mechanical strength. The coating layer is not limited to using only one type of polymer, but a mixture of two or more types may be used.

The coating layer may contain a resistance adjuster or a charge control agent.

As a method for coating the carrier core material with a polymeric material, any known method such as a fluidized bed method or a transfer layer method can be employed. For example, when ferrite is used as the carrier core material and silicone resin is used as the polymer coating layer, it can be manufactured as follows.

That is, ferrite as a carrier core material is placed in a fluidized bed type coating device, and air is supplied from the bottom of the coating device to suspend the ferrite and bring it into a fluidized state. On the other hand, a silicone resin solution in which a predetermined amount of silicone resin is dissolved in a solvent is prepared, and is sprayed from above the coating device onto the floating and fluid ferrite to coat it with the silicone resin.

The carrier of the two-component developer of the present invention has a ratio of (resistance value of carrier core material)/(carrier resistance value) of 0.020 or more, preferably 0.020 to 0.20.

(Resistance value of carrier core material)/(Carrier resistance value) is 0.
If it is less than 020, counter charges tend to remain in the polymer coating layer, and carrier flying tends to occur.

The toner of the present invention is colored fine particles composed of a fixing resin, a colorant, a charge control agent, a release agent, and the like.

In order to produce the styrene-acrylic copolymer having a molecular weight distribution of the present invention as the fixing resin, a method of widening the dispersion or molecular weight distribution (MP/M) of a low molecular weight resin component,
There is a method of widening the MW/MN of the high molecular weight resin component and a method of widening the M w /MN of both resin components.In short, it is sufficient to increase the overlap of the molecular weight distributions of both resin components. In general, M u / M N of high molecular weight components
It is desirable to increase the toner properties, and the dispersion M, /M of the high molecular weight component is 2.7 to 3.7, especially 3.
A range of 0 to 3°4 is preferable. On the other hand, the dispersion M, /M, of low molecular weight components is 1. 5 to 2.5, especially 1°8
It is preferable that it be in the range of ~2.2. Further, the ratio of S and SL is preferably in the range of 15:85 to 50:50, particularly 20:80 to 45:55, assuming a total of 100.

The styrene-acrylic copolymer used in the present invention is produced by homogeneously melt-blending multiple types of styrene-acrylic copolymers with different molecular weight distributions so that the molecular weight distribution falls within the above-mentioned range. It is produced by using a step polymerization method.

For example, as shown in FIG. 4, a styrene-acrylic copolymer (low molecular weight) having a molecular weight distribution shown in curve A,
When equal amounts of a styrene-acrylic copolymer (high molecular weight) having a molecular weight distribution shown in curve B are melt blended, a styrene-acrylic copolymer having a molecular weight distribution within the range of the present invention shown in curve C can be obtained. .

Furthermore, suspension polymerization and emulsion polymerization generally produce higher molecular weight polymers than solution polymerization. Thus, when producing a styrene-acrylic copolymer,
A suspension polymerization method or an emulsion polymerization method and a solution polymerization method are combined in this order or in the reverse order to perform multistage polymerization, and by controlling the molecular weight at each step, it is possible to obtain a molecular weight distribution within the range of the present invention. A styrene-acrylic copolymer can be obtained. The molecular weight and molecular weight distribution are controlled by selecting the type and amount of the initiator, the type of solvent involved in chain transfer, and the type of dispersant or emulsifier.

As the styrene monomer, in addition to styrene, vinyltoluene, α-methylstyrene, etc. are used. As an acrylic monomer, formula % is used.In the formula, R1 is a hydrogen atom or a lower alkyl group.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. Acrylic monomers such as acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, phenyl acrylate, methyl methacrylate, hexyl methacrylate , 2-ethylhexyl methacrylate, ethyl β-hydroxyacrylate, propyl T-hydroxyacrylate, propyl γ-N,N-diethylaminoacrylate, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, etc. Ru.

A styrene-acrylic copolymer suitable for the purpose of the present invention is styrene (SL)/methyl methacrylate (HMA).
/butyl acrylate (BA) copolymer resin, especially containing 75 to 85% by weight of St, 0.5 to 5% by weight of
and BA in an amount of 10 to 20% by weight.

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.

Examples of colorants include black pigments such as carbon black, acetylene black, and aniline black: yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, nickel titanium yellow, naphthol yellow S5 Hansa Yellow 61
Quinoline Yellow Lake, Permanent Yellow NCG
, yellow pigments such as tartrazine lake; orange pigments such as red yellow lead, molybdenum orange, permanent orange GTR; red iron, cadmium red, red lead, permanent red 4R, pyrazolone red, lake red D, brilliant carmine 65B, rhodamine lake B1 Red pigments such as Alizarin Lake and Brilliant Carmino 3B:
Purple pigments such as manganese violet, First Violet B, and Methyl Violet Lake; Blue pigments such as ultramarine blue, cobalt blue, partially chlorinated phthalocyanine blue, and First Sky Blue Indan Stremburu-BC; chrome green, chromium oxide, pigment green B, Green pigments such as malachite green lake; zinc white, titanium oxide,
White pigments such as antimony white and zinc sulfide; Extender pigments such as pallite powder, barium carbonate, clay silica, talc, and alumina white; Conductive pigments such as conductive carbon black and aluminum powder; Magnetic pigments such as various ferrites; Zinc oxide , photoconductive pigments such as selenium, cadmium sulfide, and cadmium selenide.

The colorant is used in an amount of 1 to 20 parts by weight, preferably 3 to 15 parts by weight, based on 100 parts by weight of the fixing resin.

There are two types of charge control agents: one for positive charge control and one for negative charge control.

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 polyamine compounds, aminosilanes, and fillers surface-treated with these compounds.

On the other hand, examples of charge control agents for controlling negative charges 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 0.1 parts by weight per 100 parts by weight of the fixing resin.
It is used in a proportion of ~10 parts by weight, preferably 0.5-8 parts by weight.

Examples of the mold release agent (offset inhibitor) include aliphatic resins, aliphatic metal salts, higher fatty acids, fatty acid esters, and partially saponified products thereof. Among these, low molecular weight aliphatic resins having a weight average molecular weight of 1,000 to 10,000 are preferred. Specifically, one or a combination of two or more of low molecular weight polypropylene, high molecular weight polyethylene, paraffin wax, and low molecular weight olefin polymers consisting of olefin units having 4 or more carbon atoms are suitable. In addition to the above-mentioned substances, silicone oil, various waxes, etc. can also be used.

The release agent should be added in an amount of 0.1 to 1.00 parts by weight of the fixing resin.
It is used in a proportion of 10 parts by weight, preferably 0.5 to 8 parts by weight.

I.ner premixes the above-mentioned components homogeneously using a dry blender Henschel mixer, ball mill, etc.
This mixture is melt-kneaded using a kneading device such as a Banbury mixer, roll, screw or twin-screw extrusion kneader, and the kneaded product is cooled, pulverized and, if necessary, classified to produce the product.

The particle size distribution of toner can be adjusted not only by the pulverization process but also by classification.

〔Example〕

Hereinafter, the two-component developer of the present invention will be explained in detail with reference to Examples.

~ ゛ and 1-2 (1) Preparation of carrier Core material: ferrite particle center particle diameter: approximately 100 μm Saturation magnetization: 50 emu/g Coating layer polymer: styrene-acrylic copolymer The above polymer was coated using a fluid coating method. A coating layer was formed by coating the surface of the core material to produce carriers having different resistance values. Table 1 shows the resistance values of each carrier obtained. Further, (resistance value of carrier core material)/(carrier resistance value) was determined from the resistance value of this carrier and the resistance value of the core material determined in advance.

Note that the resistance value of the carrier was measured as shown below.

[Method of measuring carrier resistance]

Imitating the magnetic brush development method, with an inter-electrode spacing of 5 mm,
The poles and south poles are opposed. In this case, the surface magnetic flux density of the magnetic pole is 1500 Gauss, and the area of the opposing magnetic pole is lO10X
Set it to 30. Parallel plate electrodes are arranged between the magnetic poles with an inter-electrode spacing of 2 mm, and 200 mg of a sample is placed between the electrodes and held by magnetic force. Then, the resistance value was measured using an insulation resistance meter or an ammeter.

(2) Preparation of toner Styrene (SL)/Methyl methacrylate (HMA)
/butyl acrylate (BA) copolymer (St: MM
A: BA = 75:5:20), the peak value on the high molecular weight side is 240000, M w / M N is 3.0, the peak value on the low molecular weight side is 11000, and M W / M N is 2.2. is shown in Figure 3 (V/P = 0.048
．． SH:5L-32:6B) using resin, resin 10
0 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 were mixed, and after melt-kneading, cooling, pulverization, and classification were performed. A toner was produced. Then, 0.2 parts by weight of hydrophobic silica was mixed with 100 parts by weight of this toner.

The carrier and toner obtained as described above were mixed in a weight ratio of 100:3.5 to obtain a developer.

[Carrier flight evaluation test]

The obtained developer was transferred to a copying machine (DC manufactured by Sanda Kogyo Co., Ltd.).
3255). On the other hand, a mesh chart was prepared in which a mesh pattern in which a large number of square straight lines were drawn vertically and horizontally at intervals of about 0.57 mm was pasted at 30 locations within a square frame with a side length of 24 mm.

Using this mesh chart as a manuscript, 500 copies were made using the copying machine.
When 0 copies are made, when 0 copies are made, when 500 copies are made, when 1000 copies are made,
2000 sheets, 3000 sheets, 4000 sheets and 50 sheets
At the time of 00 sheets, 5 sheets were each sampled 7 times, and the presence or absence of image blanking due to carrier flying was checked and evaluated according to the following criteria.

The results are shown in Table 1.

○: Image missing in 9 or less places ×: Image missing in 10 or more places In addition, initial image density (ID) and fixability tests were also conducted. The initial image density was measured using a reflection densitometer (MODEL) manufactured by Tokyo Juishokusha.
TC-6D).

The fixing property test was carried out using a DC5585 modified machine (heated pressure roll fixing method) manufactured by Sanda Kogyo Co., Ltd., and the set temperature of the heating roller was increased from 140"C in 2.5°C increments until a toner image was formed. The fixed image was fixed by passing a sheet of transfer paper through it, pressing an adhesive tape against the formed fixed image, and then peeling it off.The density of the fixed image before and after peeling was measured using the above-mentioned reflection densitometer. Then, the minimum fixing temperature was determined by determining the temperature at which the fixing rate was 90%, and the temperature at which high temperature offset occurred was determined in the same manner.

These results are also shown in Table 1.

(1) Preparation of carriers Carriers were prepared in the same manner as in Examples 1 to 4 and Comparative Examples 1 to 2, and the resistance values of the carriers were measured.

(2) Preparation of toner Styrene (sD/methyl methacrylate (HMA)/butyl acrylate (BA) copolymer (St: MMA)
:BA-80:5:15) The peak value on the high molecular weight side is 597000, M u / MN is 3.1, and the peak value on the low molecular weight side is 12200 TeM. /M, is 1.9
5(7) GPC is shown in Figure 5D (V/P = 0-
14+sn:SL=25:75) Toners were prepared in the same manner as in Examples 1 to 4 and Comparative Examples 1 to 2 using the resin, and various tests were conducted. The following is shown in Table 1.

Comparative Example 1 (1) Preparation of carriers Carriers were prepared in the same manner as in Examples 1 to 4 and Comparative Examples 1 to 2, and the resistance values of the carriers were measured.

(2) Preparation of toner Styrene (SL)/Methyl methacrylate (HMA)
/butyl acrylate (BA) copolymer (St: MM
A:BA=83:5:12), the high molecular weight side peak value is 600000, M, /MN is 3.0, the low molecular weight side peak value is 120007: M, 1/M N is 2.
0 (DGPC is shown in FIG. 6 (V/P = 0.309.
SH:SL=30:70) Toners were prepared in the same manner as in Examples 1 to 4 and Comparative Examples 1 to 2 using the resin, and various tests were conducted. The following is shown in Table 1.

(1) Preparation of carriers Carriers were prepared in the same manner as in Examples 1 to 4 and Comparative Examples 1 to 2, and the resistance values of the carriers were measured.

(2) Preparation of toner Styrene (St)/Methyl methacrylate (MMA)
/butyl acrylate (BA) copolymer (St: MM
A:BA=82:4:14), the peak value on the high molecular weight side is 85000, M W / M)l is 3.0,
The low molecular weight side peak value is 5000 and M, /MN is 2.3
The GP-C of is shown in FIG. 7 (V/P = 0.152.
Toners were prepared in the same manner as in Examples 1 to 4 and Comparative Examples 1 to 2 using a resin (Sll:SL = 24: 76), and various tests were conducted. The following is shown in Table 1.

(Left below) As can be seen from Table 1, (resistance value of carrier core material)/(
Examples 1 to 5 in which the carrier resistance value) is 0.020 or more
It was confirmed that carrier flying was prevented and image blanking was hardly a problem. Further, the temperature difference between the minimum fixing temperature and the high-temperature offset generation temperature was wide, and the fixable temperature range was wide. Furthermore, the amount of spent toner was also small.

On the other hand, Comparative Example 1.2, in which (resistance value of carrier core material)/(resistance value of carrier) is small, has a large amount of carrier flying and has a lower initial image density than Examples 1 to 5. In addition, in Comparative Examples 3 and 4, (resistance value of carrier core material)/(carrier resistance value) is 0.020 or more, and the initial image density is high, but the fixing resin component has a high molecular weight. Because any one of the peak position, the peak position on the low molecular weight side, and the V/P value was out of the range of the present invention, carrier flying was not prevented and many white spots were observed in the image. . Furthermore, the fixing properties were also inferior to those of Examples 1 to 5.

As described above, compared to Comparative Examples 1 to 4, the two-component developers obtained in Examples 1 to 5 were all prevented from carrier flying, had almost no image white spots, and had good initial image density. It showed the value.

〔Effect of the invention〕

According to the two-component developer of the present invention, (resistance value of carrier core material)/(carrier resistance (liquid) is 0.020 or more, and the fixing resin component of the toner is determined in a gel permeation chromatogram. , a high molecular weight maximum value on the higher molecular weight side than the molecular weight lXl0', a molecular weight of 2 x 104 to 50
The low molecular weight maximum value is in the range of 0, and the molecular weight has a minimum value in the middle between the two, and the area ratio of the valley due to the minimum value to the sum of the high molecular weight peak area and the low molecular weight peak area is 0.
Since it is a styrene-acrylic thermoplastic resin having a molecular weight distribution of 30 or less, it is possible to prevent image whitening due to carrier flying. Moreover, it is possible to produce high-quality images with high initial image density and excellent fixing properties.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing potential patterns on the photosensitive drum when solid black, proximity lines, and mesh patterns are respectively copied. FIG. 2 is an explanatory diagram showing the area ratio of valley to peak area (V/
FIG. 4 is an explanatory diagram for obtaining a resin having the molecular weight distribution of the present invention, and FIGS. 3, 5, 6, and 7 are diagrams for explaining how to obtain P). It is GPC which shows the molecular weight distribution of the resin of the Example of invention and a comparative example. Patent applicant Sanda Kogyo Co., Ltd. S+:5L=32:68

Claims (1)

[Scope of Claims] A two-component developer consisting of a carrier whose surface is covered with a polymeric coating layer and a toner containing at least a fixing resin component, )/(carrier resistance value) is 0.020 or more, and the fixing resin component of the toner has a high molecular weight maximum value on a higher molecular weight side than a molecular weight of 1×10^5 and a molecular weight of 2 in a gel permeation chromatogram. x 10^4 to 500, and the molecular weight has a minimum value between the two, and the area ratio of the valley due to the minimum value to the sum of the high molecular weight peak area and the low molecular weight peak area is 0. A two-component developer characterized by being a styrene-acrylic thermoplastic resin having a molecular weight distribution of .30 or less.