JP2008203896A - Image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming method using a full-color toner which has satisfactory fixing property while obtaining high luster. <P>SOLUTION: In the image forming method using the full-color toner, the full-color toner includes at least a binder resin and a coloring agent and uses a styrene acrylic resin as the binder resin. A molecular weight distribution of the toner measured by GPC has at least one peak and has a peak of a main component in an area of 2×10<SP>3</SP>-1×10<SP>4</SP>molecular weight. Further, the whole toner contains ≤20 wt.% components of ≤5×10<SP>2</SP>in molecular weight and ≤7 wt.% components of ≥2×10<SP>5</SP>in molecular weight and satisfies 1≤Mw/Mn≤5, where Mw is weight average molecular weight and Mn is number average molecular weight. Even at both of low and high fixing temperatures, predetermined glossiness can be obtained. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming method using a full color toner such as electrophotography, and more particularly to an image forming method using a full color toner using a styrene-acrylic resin as a binder resin.

  In recent years, electrophotographic image forming apparatuses such as copying machines and printers use color toners of three primary colors of yellow, magenta, and cyan, in addition to conventional monochrome images using only black toner, and furthermore these color toners. In addition, there are many full-color copiers, full-color printers, etc. that can reproduce various colors by appropriately superimposing black toner. Many of the full-color images created by the above apparatus are bright and glossy.

  On the other hand, since the heat efficiency is high, the operating temperature is relatively low at 160 to 200 ° C., the safety is excellent, and the apparatus can be miniaturized. Has been widely used in the past. In this roller fixing method, generally, a transfer paper is passed between upper and lower fixing rollers with built-in heaters, and toner is melted and fixed on the transfer paper while the transfer paper passes through the upper and lower fixing rollers. The glossiness varies depending on the fixing temperature described above.

Further, although it relates to a non-magnetic one-component toner, there is one in which the molecular weight distribution of the binder resin for the toner is improved with the aim of low-temperature fixing while considering colorization (Patent Document 1). reference).
In order to accurately reproduce a photographic document as a full-color image, a high glossiness is preferable.

  In addition, a toner that can be fixed at a lower fixing temperature has been desired due to a demand for energy reduction or the like.

  So far, full-color toners using a polyester resin as a binder resin have been developed to obtain the above-described high-gloss images.

  On the other hand, from the viewpoint of environmental stability and cost, it may be considered to produce a full-color toner using a styrene-acrylic resin as a binder resin. However, when a full-color toner is produced using a conventionally used styrene-acrylic resin, only low gloss can be obtained, and a desired high gloss image cannot be obtained. Further, a so-called offset occurs in which toner adheres to the fixing roller.

Further, in the toner described in Patent Document 1, when the weight average molecular weight is Mw and the number average molecular weight is Mn, the value of Mw / Mn is as high as 8 or more, so that a cold offset may occur as described later. .
JP 05-019530 A

  The present invention has been made in view of such a conventional problem, and an object thereof is an image forming method using a full color toner using a styrene-acrylic resin as a binder resin, and obtaining high gloss. Another object is to provide an image forming method in which no offset occurs.

According to the present invention, there is provided an image forming method using a full-color toner having at least a binder resin and a colorant as a full-color toner and using a styrene-acrylic resin as a binder resin by GPC. Toner having at least one peak in the molecular weight distribution of the toner to be measured, having a main component peak in the region of molecular weight 2 × 10 ³ to 1 × 10 ⁴ and having a molecular weight of 5 × 10 ² or less. When the ratio of the total weight of the component having a molecular weight of 2 × 10 ⁵ or more to the total toner is 7% by weight or less, the weight average molecular weight is Mw, and the number average molecular weight is Mn. When a full color toner having a Mw / Mn value of 1 ≦ Mw / Mn ≦ 5 was used and solid images were formed at a fixing temperature of 140 ° C. and 180 ° C., Gloss in data image (JIS-Z8741 60 degree specular gloss measurement method complies / incident angle: 60 °) is, the image forming method is provided which is characterized in that both become 10 or more.

  With full-color toners using styrene-acrylic resins that have been studied so far, only low gloss images can be obtained. On the other hand, it is considered that the molecular weight of the toner is greatly involved in obtaining a high gloss image desired particularly when the original is a photograph or the like. It is thought that if the molecular weight of the toner is lowered, the viscosity of the toner can be lowered and a high gloss image can be obtained. However, even if the molecular weight is lowered, a high gloss image cannot be obtained and the offset is reduced. It sometimes occurred.

  Further, even if the characteristics of a full-color toner using a polyester resin as a binder resin that has been able to obtain a high gloss image so far are applied to a styrene-acrylic resin as it is, the same performance cannot be obtained.

Thus, as a result of intensive studies on whether or not a high-gloss image can be obtained depending on the degree of distribution and the peak position in the molecular weight distribution of the toner, the present inventors have found that the peak with the largest area exists in a specific range. High-gloss image by making specific distribution such as whether the molecular weight distribution is broad (the molecular weight width where the toner particles are present is wide) or sharp (the molecular weight width where the toner particles are present is relatively narrow) It was found that a toner that does not generate offset can be obtained. This made it possible to meet various machine specifications.
The toner of the present invention can be produced by a per se known method such as a pulverization classification method, a melt granulation method, a spray granulation method, a suspension / emulsion polymerization method or the like. The method can be suitably used. In the pulverization classification method, a toner composition such as a binder resin and a colorant and, if necessary, a magnetic powder, a charge control agent, and a release agent are premixed with a Henschel mixer or a V-type mixer, and then a twin screw extruder or the like. Melt kneading using a melt kneading apparatus. The melt-kneaded product is cooled, then coarsely pulverized and finely pulverized, and then classified as necessary to obtain toner particles having a predetermined particle size distribution. If necessary, the surface of the toner particles is treated with a surface treatment agent to obtain a toner.

  In order to obtain a high-quality image, it is preferable that the toner has a volume center particle size in the range of 5.0 to 12.0 μm.

  In the binder resin of the present invention, a styrene-acrylic resin is used.

  Examples of the monomer that serves as the base of the styrene-acrylic resin include styrene derivatives such as styrene, α-methylstyrene, p-methylstyrene, pt-butylstyrene, p-chlorostyrene, and hydroxystyrene; methacrylic acid, methyl (Meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, glycidyl (meth) acrylate, methoxyethyl (meth) acrylate, propoxyethyl (meth) acrylate, methoxydiethylene glycol (meth) acrylate, Ethoxydiethylene glycol (meth) acrylate, benzyl (meth) acrylate, cyclohexyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, (meth) acrylonitrile, (meth) Kurylamide, N-methylol (meth) acrylamide, ethylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, trimethylolethane tri (meth) acrylate And (meth) acrylic acid esters.

  The mixture of various monomers can be polymerized by any method such as solution polymerization, bulk polymerization, emulsion polymerization, suspension polymerization, and the like, and can be used as a binder resin used in the present invention. In the polymerization, usable polymerization initiators include acetyl peroxide, decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, azobisisobutyronitrile, 2,2′-azobis-2,4-dimethylvaleronitrile, 2 , 2′-azobis-4-methoxy-2,4-dimethylvaleronitrile and other known polymerization initiators can be used. These polymerization initiators are preferably used in the range of 0.1 to 15% by weight based on the total weight of the monomers.

  In the present invention, the molecular weight distribution of the toner is measured using GPC (gel permeation chromatography) as follows. The GPC apparatus used for the measurement is HLC-8220 GPC manufactured by Tosoh Corporation, and the column uses TFKgel GMHxl (two series) manufactured by Tosoh Corporation.

  100 mg of toner and 20 ml of THF (tetrahydrofuran) are mixed and stirred with a ball mill or the like until they are uniformly dissolved. Thereafter, the supernatant liquid separated by the centrifuge is used as a GPC sample. The toner concentration in the sample is preferably 1 to 10 mg / ml.

  In the measurement, THF is used as a solvent, the column of the GPC apparatus is stabilized at 40 ° C., and then the column is caused to flow at a flow rate of 1 ml per minute at this temperature, and about 100 μl of the THF sample solution is injected and measured. The molecular weight distribution of the sample is calculated from the relationship between the logarithmic value of the calibration curve prepared using several types of monodisperse polystyrene standard samples and the number of counts. As a standard polystyrene sample for preparing a calibration curve, for example, polystyrene having a molecular weight of 500 to 1,000,000 can be used.

  Examples of the column include a styrene-divinylbenzene-based polymer column.

  The peak in the present invention is a maximum value or a shoulder.

  Here, the peak of the main component in the present invention will be described with reference to FIG. FIG. 1 is an example of a molecular weight distribution diagram measured by GPC. A straight line is drawn downward from the minimum value of the curve and the shoulder in this molecular weight distribution diagram. A portion between such straight lines is defined as a peak area or a shoulder area. In FIG. 1, the numbers 1 to 6 are the respective peak areas or shoulder areas. In the present invention, the peak having the largest area is defined as the main component peak. That is, in FIG. 1, the peak X at 4 is the main component peak.

  If the peak of the main component is too much in the polymer region, when the fixing temperature is low, the toner becomes difficult to melt, the cohesive force between the melted toner and the unmelted toner becomes weak, and so-called cold offset occurs. Further, since the elasticity is strong, the surface of the fixed image becomes rough, and the glossiness of the image becomes low.

  On the other hand, if the peak of the main component exists in a very low molecular region, when the fixing temperature is high, the elasticity of the toner is weakened, the cohesive force between the toners is weakened, and so-called hot offset occurs.

  Even if the molecular region where the peak of the main component exists is in an appropriate range, it is not possible to widen the range where the fixing temperature is not offset even when the fixing temperature is high or low while obtaining a high gloss image. Even if the peak of the main component exists in the appropriate molecular region, if too many toner particles are present in the low molecular region or high molecular region, it will be difficult to melt at both low and high fixing temperatures and offset. Is likely to occur, and the temperature range that can be fixed becomes narrow.

  In addition, the molecular region where the main component peak exists is in an appropriate range, and there are few toner particles in the low molecular region or the high molecular region, or there are almost no toner particles in the appropriate range. In such a case, when the fixing temperature is high, it is melted too much and hot offset occurs.

As a result of repeated experiments, the inventors who have obtained the above viewpoint have at least one peak, and the toner has a main component peak in the region of molecular weight 2 × 10 ³ to 1 × 10 ⁴ , and The proportion of the component having a molecular weight of 5 × 10 ² or less in the whole toner is 20% by weight or less, the proportion of the component having a molecular weight of 2 × 10 ⁵ or more in the whole toner is 7% by weight or less, and the weight average molecular weight is When Mw and the number average molecular weight are Mn, when the value of Mw / Mn is 1 ≦ Mw / Mn ≦ 5, a desired fixing temperature range can be obtained while obtaining a high gloss image.

When the peak of the main component of the toner is in a region lower than the region having a molecular weight of 2 × 10 ³ to 1 × 10 ⁴ , the glossiness becomes too high or hot offset occurs. If the peak of the main component of the toner is in a region higher than the region having a molecular weight of 2 × 10 ³ to 1 × 10 ⁴ , the glossiness becomes too low or a cold offset occurs.

When the proportion of the component having a molecular weight of 5 × 10 ² or less in the whole toner exceeds 20% by weight, hot offset occurs, and the proportion of the component having a molecular weight of 2 × 10 ⁵ or more in the whole toner exceeds 7% by weight. A cold offset occurs.

  On the other hand, if the value of Mw / Mn is smaller than 1, hot offset occurs. If the value of Mw / Mn is greater than 5, a cold offset occurs.

  The molecular weight distribution of the toner in the present invention is adjusted by the molecular weight of the monomer based on the molecular weight distribution of the styrene-acrylic resin as the binder resin, or at the melt kneading stage of the toner production stage. It can be obtained by adjusting the kneading conditions.

  The binder resin used preferably has a glass transition temperature in the range of 55 to 65 ° C. This is because if the glass transition temperature is less than 55 ° C., the toner may be hardened in the developing device or the toner cartridge, and if it exceeds 65 ° C., the toner may not be sufficiently fixed on the transfer object such as paper.

Examples of the colorant to be contained in the binder resin include the following.
Black toner colorant:
Carbon black, acetylene black, lamp black, aniline black, etc.
Colorant for yellow toner:
C. I. Pigment yellow 1, C.I. I. Pigment yellow 5, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 180, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 4, C.I. I. Pigment yellow 81, C.I. I. Pigment yellow 97, C.I. I. Azo pigments such as CI Pigment Yellow 93; inorganic pigments such as yellow iron oxide and ocher; I. Nitro dyes such as Acid Yellow 1; C.I. I. Solvent Yellow 2, C.I. I. Solvent Yellow 6, C.I. I. Solvent Yellow 14, C.I. I. Solvent Yellow 15, C.I. I. Solvent Yellow 19, C.I. I. Oil-soluble dyes such as Solvent Yellow 21
Colorant for magenta toner:
C. I. Pigment red 49, C.I. I. Pigment red 57, C.I. I. Pigment red 81, C.I. I. Pigment red 122, C.I. I. Pigment red 184, C.I. I. Pigment red 238, C.I. I. Solvent Red 19, C.I. I. Solvent Red 49, C.I. I. Solvent Red 52, C.I. I. Basic Red 10, C.I. I. Disperse Red 15 etc.
Colorant for cyan toner:
C. I. Pigment blue 15, C.I. I. Pigment blue 16, C.I. I. Solvent Blue 55, C.I. I. Solvent Blue 70, C.I. I. Direct Blue 25, C.I. I. Direct Blue 86 etc.

  The above-mentioned colorant is used in an amount of 2 to 20 parts by weight, particularly 4 to 15 parts by weight, per 100 parts by weight of the fixing resin.

  Moreover, a charge control agent can be contained as needed. As the charge control agent, conventionally known charge control agents can be used. For example, as the positively chargeable charge control agent, nigrosine dye, fatty acid-modified nigrosine dye, carboxyl group-containing fatty acid-modified nigrosine dye, quaternary ammonium salt, amine series Compounds, organometallic compounds, and the like can be used, and as the negatively chargeable charge control agent, metal complexes of oxycarboxylic acids, metal complexes of azo compounds, metal complex dyes, salicylic acid derivatives, and the like can be used.

  Moreover, a mold release agent can be contained as needed. Examples of the release agent include conventionally known waxes, for example, aliphatic hydrocarbon waxes such as paraffin wax, petroleum wax, polyethylene wax, polypropylene wax, polyethylene oxide wax, montan wax, carnauba wax, beeswax, and wood wax. Used.

  These release agents preferably have a melting point of 50 to 140 ° C., particularly 70 to 120 ° C.

  The content of these release agents is usually 1 to 20 parts by weight, particularly 3 to 10 parts by weight per 100 parts by weight of the binder resin component.

  Moreover, a surface treating agent can be used as needed. Surface treatment agents include inorganic fine powders such as silica, alumina, titanium oxide, zinc oxide, magnesium oxide, and calcium carbonate; organic fine powders such as polymethyl methacrylate to adjust the charge controllability and fluidity of the toner. A fatty acid metal salt such as zinc stearate can be used, and one or more of these can be used in combination. The addition amount of the surface treatment agent is preferably in the range of 0.1 to 2.0 wt% per toner particle. The surface treatment agent and toner particles can be mixed using, for example, a Henschel mixer, a V-type mixer, a turbula mixer, a hybridizer, or the like.

  The toner of the present invention can be used as a one-component developer or a two-component developer. There are no limitations on the carrier used when used as a two-component developer, for example, magnetic metals such as iron, nickel, cobalt and their alloys, or alloys containing rare earths, hematite, magnetite, manganese-zinc Sintering and atomizing magnetic materials such as ferrite, nickel-zinc ferrite, manganese-magnesium ferrite, lithium ferrite and other soft ferrites, copper-zinc ferrite and other iron-based oxides, and mixtures thereof The magnetic particles produced by this method, and those obtained by coating the surfaces of the magnetic particles with a resin can be used.

The particle diameter of the carrier is generally 30 to 200 μm, particularly preferably 40 to 150 μm, expressed in terms of particle diameter by electron microscopy. Further, the apparent density of the carrier is preferably in the range of 2.4 to 3.0 × 10 ³ kg / m ³ , although it varies depending on the composition of the magnetic material, the surface structure, etc. when the magnetic material is mainly used.

  The toners and the two-component developers of Examples 1 to 4 and Comparative Examples 1 to 6 were prepared as follows.

(Binder Resin Production Example 1)
A monomer solution composed of 70 parts by weight of styrene and 30 parts by weight of butyl acrylate was added to 10 parts by weight of a polymerization initiator V-59 (2,2′-azobis (2-methylbutyronitrile), manufactured by Wako Pure Chemical Industries, Ltd.). And 200 parts by weight of toluene as a solvent (containing a condenser and refluxing toluene) was added dropwise over 3 hours (temperature 40 ° C.). After completion of the dropping, the polymerization start temperature was set to 40 ° C., and toluene that had been subjected to the polymerization reaction for 12 hours while being heated at 4 ° C. per hour was removed by distillation under reduced pressure, and the binder for the toner of Example 1 shown in Table 1 was removed. Resin No. 1 was obtained.

(Binder Resin Production Example 2)
The toner of Example 2 shown in Table 1 was prepared in the same manner as in Production Example 1 except that 11 parts by weight of V-59 was used as the polymerization initiator, the polymerization initiation temperature was 60 ° C., and the polymerization reaction was carried out at a constant temperature for 12 hours. Binder resin no. 2 was obtained.

(Binder Resin Production Example 3)
In the same manner as in Production Example 1 except that 8 parts by weight of V-59 was used as the polymerization initiator, the binder resin No. 1 for Toner of Example 3 described in Table 1 was used. 3 was obtained.

(Binder Resin Production Example 4)
Except for using 15 parts by weight of V-59 as a polymerization initiator, the binder resin No. 1 for Toner of Example 4 described in Table 1 was prepared in the same manner as in Production Example 2. 4 was obtained.

(Binder Resin Production Example 5)
Comparative Examples described in Table 1 in the same manner as in Production Example 2 except that 12 parts by weight of V-65 (2,2′-azobis (2.4-dimethylvaleronitrile), manufactured by Wako Pure Chemical Industries, Ltd.) was used as the polymerization initiator. No. 1 binder resin No. 1 5 was obtained.

(Binder Resin Production Example 6)
The binder resin for the toner of Comparative Example 2 described in Table 1 in the same manner as in Production Example 2 except that a mixture obtained by mixing 5 parts by weight of V-59 and 3 parts by weight of V-65 was used as the polymerization initiator. No. 6 was obtained.

(Binder Resin Production Example 7)
The binder resin for the toner of Comparative Example 3 described in Table 1 in the same manner as in Production Example 2 except that a mixture obtained by mixing 15 parts by weight of V-59 and 3 parts by weight of V-65 was used as the polymerization initiator. No. 7 was obtained.

(Binder Resin Production Example 8)
Except for using 8 parts by weight of V-65 as a polymerization initiator, the binder resin No. 1 for the toner of Comparative Example 4 described in Table 1 was prepared in the same manner as in Production Example 1. 8 was obtained.

(Binder Resin Production Example 9)
The binder resin for the toner of Comparative Example 5 shown in Table 1 in the same manner as in Production Example 2 except that a mixture obtained by mixing 13 parts by weight of V-59 and 3 parts by weight of V-65 was used as the polymerization initiator. No. 9 was obtained.

(Binder Resin Production Example 10)
The binder resin No. 1 for the toner of Comparative Example 6 shown in Table 1 was prepared in the same manner as in Production Example 2 except that 9 parts by weight of V-65 was used as the polymerization initiator. 10 was obtained.

[Example 1]
Binder resin no. 1, 3 parts by weight of a quaternary ammonium salt compound (P-51, manufactured by Orient Chemical Co., Ltd.) as a charge control material, 4 parts by weight of a cyan pigment (PB15-3, manufactured by Cibagayki) as a colorant, and a fisher as a release agent -5 parts by weight of Tropsch wax (FT-100, manufactured by Nippon Seiki) was mixed with a Henschel mixer, and then melt-kneaded with a twin screw extruder to prepare a resin composition for toner. The obtained resin composition for toner was finely pulverized with an airflow pulverizer and classified with an air classifier to obtain toner particles having an average particle diameter of 8 μm on a volume basis. 0.5 parts by weight of hydrophobic silica (TG820, manufactured by Cabot Corporation) as a surface treatment agent and 0.8% by weight of titanium oxide (EC-100T, manufactured by Titanium Industry) with respect to 100 parts by weight of the toner particles. The toner was added and mixed with high stirring with a Henschel mixer to obtain a toner.

  This toner was blended with a ferrite carrier (EF-60B, manufactured by Powder Tech Co., Ltd.) having an average particle diameter of 80 μm whose surface was coated with a silicone resin so that the toner concentration was 5% by weight, and the mixture was uniformly stirred and mixed. A system developer was obtained.

  The molecular weight distribution of the obtained toner is shown in Table 1 described later.

[Examples 2 to 4 and Comparative Examples 1 to 6]
A toner was produced in the same manner as in Example 1 using the binder resin produced as described above, and then a two-component developer was produced in the same manner as in Example 1.
The molecular weight distribution of the obtained toner is shown in Table 1 described later.

  The toners in Examples 1 to 4 and Comparative Examples 1 to 6 have different molecular weight distributions, but these are adjusted by changing the molecular weight of the monomer that forms the styrene-acrylic resin and the polymerization time. The molecular weight distribution is changed by changing the temperature of kneading and kneading conditions at the time of toner preparation.

  For the developers of the above examples and comparative examples, the color printer LS-8000C (manufactured by Kyocera Corporation) is replaced with a modified machine (the developer of the developing device is replaced with the developer prepared as described above, and the fixing temperature of the fixing device is changed. The image was formed using a modification so as to be variable, and the glossiness and offset when the fixing temperature was 140 ° C. and the glossiness and offset when the fixing temperature was 180 ° C. were evaluated.

  The evaluation criteria of the above examples and comparative examples are as follows.

(Image gloss)
The glossiness at fixing temperatures of 140 ° C. and 180 ° C. was measured. For the measurement, A4 size paper (Fuji Xerox Co., Ltd., C2 paper, 70 g paper) was used, and the short side was the transport direction. The image used for the measurement is three solid images of 3 x 3 cm on the line connecting the midpoints of the short sides of the paper, the center of which is placed on the line, and the center of the central solid image is the center of the paper The distance between the centers of the images was 10 cm. The toner amount of the solid image was 0.7 mg / cm ² .

  The measurement was performed at three locations for one solid image, and the average value of the five solid image portions was defined as the glossiness. For the measurement of glossiness, the solid image portion is measured at an incident angle of 60 degrees using a gloss meter (Nippon Denshoku PG-1M) according to JIS-Z8741 60-degree specular gloss measurement method.

  When the glossiness was 10 or more at either temperature, it was rated as “◯”, and when the glossiness was below 10, it was marked as “x”. The numerical values in the table are the better ones of the measurement results at the two fixing temperatures, that is, the higher ones.

(offset)
Image formation was carried out at a fixing temperature of 140 ° C. and 180 ° C., and it was confirmed whether or not toner was adhered to the fixing roller. An offset at 140 ° C. was a cold offset, and an offset at 180 ° C. was a hot offset. For the offset measurement, A4 size paper (Fuji Xerox Co., C2 paper, 70 g paper) was used, and the short side was set as the transport direction. The image used for the measurement has three 3 × 3 cm solid images arranged on the line connecting the midpoints of the long sides of the paper so that the center is on the line. The center solid image has its center at the center of the paper. The distance between the centers of the images was set to 7 cm, together with the center. The toner amount of the solid image was 0.7 mg / cm ² .

  The results are shown in Table 1.

When Mw / Mn is low, the glossiness becomes too high when the fixing temperature is 180 ° C., and hot offset occurs. When Mw / Mn is high, the glossiness becomes too low when the fixing temperature is 180 ° C., and cold offset occurs. When the peak molecular weight of the main component is less than 2 × 10 ³ , the glossiness becomes too high and hot offset occurs. If the peak molecular weight of the main component is larger than 1 × 10 ⁴ , the glossiness becomes too low and a cold offset occurs. When the proportion of the component having a molecular weight of 5 × 10 ² or less exceeds 20% by weight, the gloss becomes too high and hot offset occurs. When the proportion of the component having a molecular weight of 2 × 10 ⁵ or more exceeds 7% by weight, the glossiness becomes too low and a cold offset occurs.

  On the other hand, in the present invention, even when the fixing temperature is changed in a wide range of 140 ° C. and 180 ° C., a high gloss image (glossiness of 10 or more) can be obtained, and no offset occurs.

  As described above in detail, according to the image forming method using the full-color toner of the present invention, it is possible to form an image with high gloss and no offset.

The molecular weight distribution map measured by GPC which is an example for demonstrating the peak of the main component which concerns on this invention.

Claims (4)

An image forming method using a full color toner,
The full color toner has at least a binder resin and a colorant,
Using a styrene-acrylic resin as the binder resin,
In the toner molecular weight distribution measured by GPC, it has at least one peak,
It has a main component peak in the region of molecular weight 2 × 10 ³ to 1 × 10 ⁴ , and
The proportion of the component having a molecular weight of 5 × 10 ² or less in the whole toner is 20% by weight or less,
The proportion of the component having a molecular weight of 2 × 10 ⁵ or more in the whole toner is 7% by weight or less,
Using a full-color toner in which the value of Mw / Mn is 1 ≦ Mw / Mn ≦ 5 when the weight average molecular weight is Mw and the number average molecular weight is Mn,
When solid images are formed at a fixing temperature of 140 ° C. and 180 ° C., the glossiness of each solid image (according to JIS-Z8741 60 ° specular gloss measurement method / incident angle: 60 °) is both 10 or more. An image forming method characterized in that a value is obtained.   2. The image forming method according to claim 1, wherein a value of Mw / Mn in the full color toner is set to a value within a range of 3.6 ≦ Mw / Mn ≦ 5.   The image forming method according to claim 1, wherein the full-color toner contains a quaternary ammonium salt compound as a charge control agent.   The image forming method according to claim 1, wherein the binder resin in the full-color toner is a styrene-acrylic resin obtained by polymerizing a monomer component in a solvent. .