JPH05346730A - Image forming method - Google Patents

Abstract

PURPOSE:To obtain an image forming method which gives the narrow distribution of electrostatic charged amount and where developing performance is improved. CONSTITUTION:This image forming method is provided with a latent image forming stage, a developing stage, and a transfer stage. In the developing stage, a one-component developing device is used, which is provided with a developer carrier 1 arranged to be opposed to an electrostatic latent image holding body and a developer regulating member 2 forming the thin layer of developer by nipping a soft elastic member 22 fixed to one end of a spring member 21 on the developer carrier 1, and also provided with a substance whose specified area from a front end on a developer inflow side nips the developer carrier 1 through the developer and where an angle theta formed by its nip surface 22a and its front end surface 22b satisfies the relation of 105 deg.<=theta<=165 deg. as the soft elastic member; and one-component type developer consisting of at least binding resin, electrostatic charging control agent and magnetic powder is used as the developer. In such a case, the resin where number average molecular weight (Mn) is 2000 to 15000, Z average molecular weight (Mz) is 2400000, and Mz/Mn is 50 to 600 is used as the binding resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method applied to an image forming apparatus such as an electrophotographic copying machine and a printer, and more particularly, to an image forming method between an electrostatic latent image holding member and a developer carrying member. The present invention relates to an image forming method using a one-component developing device that develops an electrostatic latent image by flying a one-component developer in an oscillating electric field.

[0002]

2. Description of the Related Art As an image forming method for developing an electrostatic latent image formed on a latent image carrier to form a visible image, various types of conventional developing methods have been used depending on the type of developer used. A device using the device has been proposed. Among them, an image forming method using a one-component developing device shown in FIG. 3, for example, is known as one using a one-component developer consisting of only toner. In FIG. 3, a hopper a containing a developer t made of a magnetic toner and a plurality of magnets b2 are fixedly arranged in a rotatable cylindrical sleeve b1, and the developer t attracts the developer t on the sleeve b1 by magnetic force. Agent carrier b (hereinafter referred to as "developing roll") and spring plate member c
A soft elastic member c2 having a substantially flat plate shape fixed to one end of 1 is nipped in the developing roll b, and a developer regulating member c for thinning the transported developer t is formed.

[0003]

In this one-component developing device, the developer t, which is thinned to a predetermined layer thickness by the developer regulating member c, flies from the developing roll b toward the electrostatic latent image carrier e. Then, the electrostatic latent image f is developed, but the density of the toner image formed by the development is significantly affected by the layer thickness of the developer thinned on the sleeve b1 and its uniformity.
Therefore, since it is necessary to appropriately control the layer thickness and the uniformity of the developer in the axial direction and the circumferential direction of the developing roll, the developer regulating member responsible for thinning the developer is a nip of the soft elastic member with respect to the developing roll. It is required that the position be strictly specified and attached to the holder. In the conventional developer regulating member, the allowable error in attaching to the holder was about 2 mm. And, each component of the developing device is designed with a certain degree of tolerance,
Considering the fact that the actually assembled device has a cumulative tolerance of 1 to 2 mm, there is a problem that the mounting of the developer regulating member has to be extremely strict.

Therefore, the inventors of the present invention firstly made the soft elastic member of the developer regulating member nip the developing roll through the developer in a predetermined region from the front end of the developer inflow side, and
The angle θ between the nip surface and the front end surface is 105 ° ≦ θ ≦
A so-called tip cutting blade method using a one-component developing device having a relationship of 165 ° has been proposed. (Patent application flat 2
However, according to this tip cut blade method, the front end surface of the nip is in a direction in which the entire blade moves away from the developing roll due to the component force of the force received from the toner layer, so that the component force varies in the axial direction. As a result, it has been found that there is a defect that the charge amount given to the toner in the nip is likely to vary, resulting in a wide charge amount distribution of the toner. The present invention has been made in view of the above circumstances, and an object thereof is to prevent a wide charge amount distribution phenomenon that occurs in the tip cutting blade method developed in consideration of a setting error of the developer regulating member. An object of the present invention is to provide an image forming method for improving the developing property.

[0005]

Means for Solving the Problems The inventors of the present invention thought that the above problems can be improved by improving the dispersibility of the magnetic powder and the charge control agent in the binder resin in the developer, and have conducted earnest studies. As a result, the Z-average molecular weight (Mz) of the binder resin was increased, and the Z-average molecular weight (Mz) / number-average molecular weight (M
By increasing the ratio of n), it was found that the charge amount distribution is narrow and the developability is improved even in the tip cutting blade method, and the present invention has been completed.

That is, according to the present invention, the step of forming a latent image on the latent image carrier, the step of developing the latent image on the latent image carrier with a one-component developer, and the transfer of the formed toner image. An image forming method having a step of transferring onto a body, wherein the developing step is carried out by carrying out a one-component developer stored in a hopper opposite to an electrostatic latent image carrier to a developing area. A developer carrying member and a developer regulating member that nips a soft elastic member fixed to one end of a spring member to the developer carrying member to form a thin layer of the developer, and the soft elastic member is a developer. A predetermined area from the front end on the inflow side nips the developer carrier via the developer, and the angle θ formed by the nip surface and the front end surface satisfies the relationship of 105 ° ≦ θ ≦ 165 °. Use the provided one-component developing device and use at least as a developer. Used those composed of a binder resin and a charge control agent and magnetic powder, the number average molecular weight of the binder resin (M
n) is 2,000 to 15,000, Z average molecular weight (Mz) is 400,000 or more, and Mz / Mn is 50 to 600.
Is characterized in that

First, the one-component developing device used in the developing step of the present invention will be described. FIG. 2 is a schematic sectional view showing an example of a one-component developing device used in the present invention, and FIG. 1 is an enlarged view showing a main part thereof. This one-component developing device uses a one-component developer, and is arranged such that the developing roll 1 arranged to face the electrostatic latent image holding member D and the leading end portion thereof come into pressure contact with the developing roll 1. The developer regulating member 2 is provided, and these are disposed in a hopper 3 for accommodating the developer T. The developing roll has a plurality of magnetic poles (N
, S ...) is magnetized, and is composed of a magnet roll 11 fixedly supported by the casing, and a cylindrical sleeve 12 that rotates around the magnet roll.
The developer T is adsorbed, conveyed, and released from the sleeve 12 in accordance with the rotation of the roller T according to the magnetic pattern of the magnet roll 11. On the other hand, the developer regulating member 2 includes a spring member 21, a soft elastic member 22 bonded to the tip of the spring member 21, and a support member 23 that supports the rear end of the spring member 21, and the holder 5
It is fixed by screwing on. Further, the holder 5 is biased by the coil spring 6 so that the soft elastic member 22 always nips the sleeve 12 with a predetermined linear pressure. Reference numeral 71 is an AC power source, 72 is a DC power source, and I is an electrostatic latent image formed on the electrostatic latent image holder.

In the present invention, as shown in FIG. 1, in the soft elastic member, a predetermined region LR from the front end of the developer inflow side nips the developing roll 1 through the developer T, and the nip of the nip. Angle θ formed by the surface 22a and the front end surface 22b
Needs to have a trapezoidal shape so as to satisfy the relation of 105 ° ≦ θ ≦ 165 °. When the angle θ is out of the above range, the mounting allowance of the developer regulating member becomes smaller than 4 mm, and the developer regulating member cannot be easily mounted.

Next, the one-component type developer used in the present invention will be described. The one-component type developer is composed of at least a binder resin, a charge control agent and magnetic powder, and the binder resin has a Mn of 2,000 or more in order to obtain heat melting property at low temperature. Those in the range of 15,000, preferably 2,000 to 10,000 are used.
When Mn is less than 2,000, the dispersibility of the magnetic powder and other internal additives deteriorates due to the decrease in viscosity during kneading.
When it exceeds 15,000, the fixability is deteriorated.

In addition, as the binder resin has a larger Mz, the resin strength increases, the viscosity at the time of heat kneading increases, the dispersibility of magnetic powder and other internal additives is improved, and the so-called toner composition distribution is controlled. The charge distribution becomes uniform. Therefore, in order to produce such an effect, Mz needs to be 400,000 or more, preferably 500,000 or more. Furthermore, even during pulverization, the amount of fine powder decreases, and the charge distribution becomes more uniform.

Further, during the melt-kneading, it is necessary that the melt is easy at the kneading temperature and the viscosity is high. Therefore, in order to improve the meltability and increase the melt viscosity, Mz / M.
It is necessary that n is 50 to 600. In particular,
The range of 70 to 600 is preferable. When Mz / Mn is less than 50, heat melting property is deteriorated and developability is deteriorated. On the other hand, when it exceeds 600, there is a problem in terms of manufacturability.

In the present invention, the binder resin has a wide range of molecular weights from a low molecular weight region to an ultrahigh molecular weight region where Mz is increased, whereby the above conditions are satisfied. In order to obtain such a binder resin, a low molecular weight polymer and a high molecular weight polymer may be mixed. A low molecular weight polymer is obtained by polymerizing an ethylenically unsaturated monomer with a polymerization initiator, while a high molecular weight polymer uses an ethylenically unsaturated monomer with a polymerization initiator. Instead, it may be formed by a two-step polymerization method in which a high-polymerization rate is polymerized by a bulk polymerization method, a solvent and a polymerization initiator are added, and a high-molecular polymer is synthesized by a solution polymerization method. That is, in order to make Mz larger, the reaction temperature of bulk polymerization for obtaining a high molecular weight polymer is 80 to 150.
The polymerization rate is 30 to 90% by weight, more preferably 3
Good results are obtained with a content of 5 to 85% by weight. Here, if the polymerization rate is less than 30% by weight, it is difficult to obtain a sufficiently large Mz, and if it exceeds 90% by weight, a large Mz is obtained, but post-treatment becomes difficult because of high viscosity. .. The termination of the bulk polymerization reaction can also be achieved by once cooling or by adding a cold solvent. In the subsequent solution polymerization, a single solvent or a combination of two or more compounds selected from aromatic hydrocarbons such as benzene, ethylbenzene and o-xylene can be used as a solvent. The solution polymerization is usually carried out at a reaction temperature of 80 to 150 ° C., but can be carried out outside the range for controlling the molecular weight. The reaction is carried out continuously or dividedly over 1 to 20 hours with the polymerization initiator uniformly mixed with the solvent. In this case, it is easier to obtain a uniform product by continuous addition. In this way, a high molecular weight polymer having Mz of 400,000 or more and Mn of 10,000 or more can be obtained.

On the other hand, various polymerization methods can be used for producing the low-molecular weight polymer, but a solution polymerization method with a small amount of impurities is preferably used. In this case, the molecular weight can be controlled by appropriately using the ratio of the solvent and the monomer, the solvent species, the chain transfer agent, the type and amount of the radical polymerization initiator, the reaction temperature and the like.

Examples of the ethylenically unsaturated monomer usable in the present invention include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate,
Octyl acrylate, cyclohexyl acrylate, lauryl acrylate, stearyl acrylate, benzyl acrylate, furfuryl acrylate, tetrahydrofurfuryl acrylate, hydroxyethyl acrylate, hydroxybutyl acrylate, dimethylaminomethyl acrylate, dimethylamino acrylate Acrylic esters such as ethyl, methyl methacrylate, ethyl methacrylate,
Propyl methacrylate, butyl methacrylate, octyl methacrylate, lauryl methacrylate, stearyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, furfuryl methacrylate, tetrahydrofurfuryl methacrylate, hydroxyethyl methacrylate,
Methacrylic acid esters such as hydroxypropyl methacrylate, hydroxybutyl methacrylate, dimethylaminomethyl methacrylate, dimethylaminoethyl methacrylate, vinyltoluene, α-methylstyrene, chlorostyrene, aromatic vinyl monomers such as styrene, malein Acid dibutyl, dioctyl maleate, dibutyl fumarate,
Unsaturated dibasic acid dialkyl esters such as dioctyl fumarate, vinyl esters such as vinyl acetate and vinyl propionate, nitrogen-containing vinyl monomers such as acrylonitrile and methacrylonitrile, acrylic acid, methacrylic acid and cinnamic acid. Unsaturated carboxylic acids, maleic acid, maleic anhydride, fumaric acid, unsaturated dicarboxylic acids such as itaconic acid, monomethyl maleate, monoethyl maleate, monobutyl maleate, monooctyl maleate, monomethyl fumarate, monoethyl fumarate, fumaric acid Unsaturated monocarboxylic acid monoesters such as monobutyl acid and monooctyl fumarate, styrene sulfonic acid, acrylamide, methacrylamide, N-substituted acrylamide, N-substituted methacrylamide, acrylamide propane sulfonic acid, and the like. At least one body is used. Among these, acrylic acid esters, methacrylic acid esters, styrene, fumaric acid dialkyl esters, acrylonitrile, methacrylic acid, cinnamic acid, fumaric acid monoesters, acrylamide, methacrylamide and the like are particularly preferable.

As the polymerization initiator to be used, generally, any one that can be used as a radical polymerization initiator can be used, for example, 2,2'-azobisisobutyronitrile, 2,2 '. -Azobis (4-methoxy-2,4-
Dimethylvaleronitrile), 2,2'-azobis (2,2
4-dimethylvaleronitrile), 2,2'-azobis (2-methylbutyronitrile), dimethyl-2,2'-
Azobisisobutyrate, 1,1'-azobis (1-cyclohexanecarbonitrile), 2- (carbamoylazo) isobutyronitrile, 2,2'-azobis (2,2
4,4-trimethylpentane), 2-phenylazo-
2,4-dimethyl-4-methoxyvaleronitrile, 2,
Azo-based polymerization initiators such as 2′-azobis (2-methylpropane), ketone peroxides such as methylethylketone peroxide, acetylacetone peroxide and cyclohexanone peroxide, 1,1-bis (1-
Peroxyketals such as butylperoxy) -3,3,5-trimethylcyclohexane, 1,1-bis (butylperoxy) cyclohexane, 2,2-bis (t-butylperoxy) butane, t-butylhydro Peroxide, cumene hydroperoxide, 1,1,3
Hydroperoxides such as 3-tetramethylbutyl hydroperoxide, di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butyl) Peroxy) hexane, dialkyl peroxides such as α, α′-bis (t-butylperoxyisopropyl) benzene, isobutyryl peroxide, octanoyl peroxide, decanoyl peroxide, lauroyl peroxide, 3,5,5. 5-trimethylhexanoyl peroxide, benzoyl peroxide, m-
Acyl peroxides such as toluoyl peroxide, di-isopropyl peroxydicarbonate, di-
2-ethylhexyl peroxydicarbonate, di-n
-Propyl peroxydicarbonate, di-2-ethoxyethyl peroxycarbonate, di-methoxyisopropyl peroxydicarbonate, di (3-methyl-3)
-Methoxybutyl) peroxycarbonate and other peroxydicarbonates, acetylcyclohexylsulfonyl peroxide and other sulfonyl peroxides,
t-butylperoxyacetate, t-butylperoxyisobutyrate, t-butylperoxydecanoate, cumylperoxyneodecanoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxy Oxylaurate, t-butylperoxybenzoate, t-butylperoxyisopropyl carbonate,
Examples thereof include peroxyesters such as di-t-butyldiperoxyisophthalate. The kind and the amount of these can be appropriately selected and used depending on the reaction temperature, the polymerization rate of the bulk polymerization and the like, and usually, it is 0.
01 to 10 parts by weight are used.

As the magnetic powder contained in the binder resin, known magnetic powders can be used, and examples thereof include iron, cobalt, nickel and their alloys, Fe ₃ O ₄ , γ-Fe ₂ O.
₃ , powder of metal oxide such as cobalt-added iron oxide, powder of Mn ferrite, Ni ferrite, Zn ferrite and the like are preferable, and magnetite powder is particularly preferably used. The content of the magnetic powder is preferably in the range of 30 to 70% by weight, more preferably 40 to 60% by weight, based on the binder resin. If the amount of magnetic powder is less than 30% by weight, problems such as fog on the background and contamination inside the machine occur,
On the other hand, if it is more than 70% by weight, problems such as deterioration in density reproducibility and defective fixing occur.

Further, the binder resin contains a charge control agent. As the charge control agent, any known charge control agent can be used. For example, a fluorosurfactant, a metal-containing complex such as a chromium salicylate complex,
Polymeric acids such as polymers containing maleic acid as a monomer component, quaternary ammonium salts, azine dyes such as nigrosine, carbon black and the like can be used. In order to produce a toner, the above toner materials may be mixed using a Banbury mixer, a kneader coater, a CM mixer, an extruder or the like, melt-kneaded, and pulverized and classified, and the average particle diameter is about 30 μm or less. , Especially 3 to 20
It is preferable to use fine particles of μm.

The developer in the present invention may contain carbon black or other pigments or dyes, if necessary. Further, in order to make the offset resistance more complete, a release agent may be added. As the release agent, polypropylene wax or the like can be used. Further, paraffins having 8 or more carbon atoms, for example, paraffin wax, paraffin latex, microcrystalline wax, etc. may be added. Further, a fluidizing agent such as silica, titania, or alumina, and an external additive such as a cleaning aid or a transfer aid such as polystyrene fine particles, polymethylmethacrylate fine particles, or polyvinylidene fluoride fine particles can be used. In particular, the primary particle size is 5 nm to 3
0 nm hydrophobic silica is preferably used.

[0019]

EXAMPLES The present invention will be specifically described below with reference to examples. All "parts" mean "parts by weight". Example 1 1) Preparation of Binder Resin (High Molecular Weight Polymer) 60 parts of styrene as a monomer and 40 parts of butyl methacrylate were charged into a flask substituted with nitrogen, heated in an oil bath, and kept at 130 ° C. for 3 minutes. Mass polymerization was carried out for a period of time. The polymerization rate at this time was 37% by weight. Next, 120 parts of xylene was added, and azoisobutyronitrile (hereinafter, referred to as AIB) was mixed and dissolved in advance.
N) 1 part and xylene 80 parts while maintaining at 100 ℃ 1
Polymerization was completed by continuously adding over 0 hours and then continuing the reaction for 2 hours. Mn: 2.4 × 10 ⁴ , Mz: 45.
It was 5 × 10 ⁴ . (Low molecular weight polymer) 100 parts of xylene was charged into a flask and kept at 120 to 155 ° C.
Part, butyl acrylate 20 parts and AIBN 3 parts were continuously added over 5 hours, and then the polymerization was continued for 2 hours. Mn: 4.1 × 10 ³ , Mz: 2.21 × 1
It was 0 ⁴ . (Binder Resin) The above two polymers were heated and mixed in a weight ratio of 50:50, and heated in vacuum to remove the solvent. After cooling, it was crushed to obtain a binder resin. (Mn: 6.9 × 10
³ ; Mz: 45.2 × 10 ⁴ ; Mz / Mn: 65.5. )

2) Preparation of one-component developer 100 parts of the above binder resin 100 parts of magnetite (particle size: 0.22 to 0.26 μm, saturation magnetization: about 80 emu / g) Low molecular weight polypropylene 2 parts Charge control agent (including Chromium dye) 1 part After premixing the above ingredients with a Henschel mixer,
The mixture was kneaded with an extruder heated to 160 ° C. After cooling, it was roughly crushed with a crusher, and mechanically crushed and air classified to obtain a toner having a particle size of about 9 μm. 0.8 wt% of hydrophobic silica fine powder was externally added to the obtained toner to prepare a one-component developer.

3) Image formation The obtained developer is supplied to a one-component developing device having the structure shown in FIG. 2 equipped with the developer regulating member having the structure shown in FIG. 1 to output an image. , The image quality was evaluated. In the used one-component developing device, as the sleeve 12 of the developing roll, a phenol resin having a resistance value of 5 × 10 ⁹ Ω · cm was formed into a cylindrical shape having a thickness of 1.0 mm, and the surface thereof was J
A semiconductive sleeve was used, which was polished in the longitudinal direction so that the average roughness of 10 points of IS was R _Z = 4.3 μm. As the developer regulating member, a supporting member 23 having a thickness of 1 mm (made of non-magnetic stainless steel SUS304, tensile strength 53 kg)
f / mm ² , proof stress 21 kgf / mm ² , and a soft elastic member 22 (made of silicon rubber: rubber hardness 5) with a thickness of 1 mm at the tip.
0 °) spring plate member 21 with a thickness of 0.05 mm
(Made of SUS304CSP3 / 4H: Tensile strength 95k
A supporter of gf / mm ² and proof stress 68 kgf / mm ² ) was used. In that case, as the soft elastic member, the nip width LR = 1.0 mm, and the nip surface 22a and the front end surface 22 are
A shape having an angle θ of 135 ° with b was used. The distance between the latent image carrier D and the sleeve 12 is 200 μm.
Meanwhile, an AC power supply 71 and a DC power supply 72 were connected to the sleeve 12, and a DC superimposed AC voltage having a frequency of 2.4 kHz, a peak-to-peak voltage of 2400 N and a DC component of 200 V was applied.

In the above-mentioned one-component developing device, the soft elastic member of the developer regulating member is always at a linear pressure of 8 g / cm.
Development was carried out so as to nip 2. As a result, it was possible to obtain a clear image that was not available in the past. When the charge amount distribution of the toner on the developing roll was measured by a charge amount distribution measuring device, it was confirmed that the distribution was narrower than the conventional one. The results are shown in Table 1 below.

Comparative Example 1 As a binder resin, a styrene-butyl acrylate copolymer (composition ratio (70:30), Mn: 1.6 × 10 ⁴ ; M
z: 82.2 × 10 ⁴ ; Mz / Mn: 51.4) except that the same developer as in Example 1 was used and an image was similarly formed. As a result, the distribution of charge amount was wide, and the level of fogging (on the opposite polarity side) on the image was inferior to that in the case of Example 1.

Comparative Example 2 As a binder resin, a styrene-butyl acrylate copolymer having a maximum value at 8,200 and 240,000 in the molecular weight distribution curve by GPC (composition ratio (70: 3
0), Mn: 3.6 × 10 ³ ; Mz: 25.3 × 1
0 ⁴ ; Mz / Mn: 70.2) was used, and the same developer as in Example 1 was used, and images were similarly formed.
As a result, the distribution of the charge amount was wide, and the level of fog (on the opposite polarity side) on the image was significantly inferior to that in the case of Example 1.

[0025]

[Table 1] 1) Measured value of distribution (trace) of toner that fell on the measurement sheet itself (evaluation of fog level) ○: good, △: somewhat bad, ×: bad. (Evaluation of Fixing Level) Using each toner, an unfixed image was sampled by Fuji Xerox XP-11 and fixed using a heating roll at 190 ° C. This fixed image was rubbed between two rubber rolls, and the degree of image disturbance was qualitatively evaluated. ○: No image distortion, △: Image is slightly disturbed, ×: Image loss occurs.

[0026]

According to the present invention, in the above-mentioned specific one-component developing device, since the one-component type developer using the binder resin having the specific molecular weight is used, the toner charge amount distribution is narrow and The image quality is improved, and an image with excellent image quality without fog is obtained.

[Brief description of drawings]

FIG. 1 is an enlarged view of a main part of an example of a one-component developing device used in the present invention.

FIG. 2 is a schematic sectional view of an example of a one-component developing device used in the present invention.

FIG. 3 is a schematic sectional view of a conventional one-component developing device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Developer carrying body, 2 ... Developer regulating member, 3 ... Hopper, 12 ... Sleeve, 21 ... Spring plate member, 22 ... Soft elastic member, 22a ... Nip surface, 22b ... Front end surface, 23 ... Support member, T ... developer, D ... electrostatic latent image carrier.

Claims (1)

[Claims] 1. A step of forming a latent image on a latent image carrier, a step of developing the latent image on the latent image carrier with a one-component developer,
In an image forming method having a step of transferring the formed toner image onto a transfer body, the developing step includes a one-component system developer disposed opposite to the electrostatic latent image holding body and accommodated in a hopper. The developer carrying member carried out to the developing area and the developer regulating member for nipping a soft elastic member fixed to one end of the spring member to the developer carrying member to form a thin layer of the developer are provided. As an elastic member, a predetermined region from the front end on the developer inflow side nips the developer carrying body through the developer, and an angle θ formed by the nip surface and the front end surface is 105 ° ≦.
A one-component developing device equipped with a material satisfying the relationship of θ ≦ 165 ° is used, and as the developer, at least a binder resin, a charge control agent, and magnetic powder is used. Has a number average molecular weight (Mn) of 2,000 to 1
5,000, Z average molecular weight (Mz) of 400,000 or more, Mz
An image forming method characterized in that / Mn is 50 to 600.