JPH08166688A - Toner for developing electrostatic charge image and image forming method using the same - Google Patents

Abstract

PURPOSE: To obtain a color toner excellent in removability, low-temp. fixability, anti-offsetting property and pulverizability and to form a fixed image in which an entry can be made with writing utensils on the surface of a transfer body with the color toner. CONSTITUTION: This toner contains a colorant and a bonding resin consisting of two kinds of polyesters. The weight ratio between the 1st and 2nd polyesters is 70:30 to 30:70. The 1st polyester has a number average mol.wt. of 3,500 to <5,000, a wt. average mol.wt. of 10,000 to <100,000, 90-130 deg.C softening point and 60-75 deg.C glass transition temp. and contains <=10% THF-insoluble component. The 2nd polyester has a number average mol.wt. of 2,500 to <3,500, a wt. average mol.wt. of 8,000 to <50,000, 90-130 deg.C softening point and 60-75 deg.C glass transition temp. When development and fixation are carried out using this toner, a releasing agent is applied to a heating roll so that the amt. of the releasing agent transferred to a transfer body is regulated to 2.0×10<-6> -2.0×10<-5> g/cm<2> .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic charge image developing toner used in electrophotography, electrostatic recording, electrostatic printing and the like, and an image forming method using the toner.

[0002]

2. Description of the Related Art Conventionally, as a method for fixing a developed visible image on an image support in electrophotography or the like,
Methods such as (1) pressure fixing, (2) flash fixing, oven fixing, and (3) heating roller fixing are known.
The method (1) is inferior in fixability because the toner is only mechanically pressed against the surface of the image support such as paper, and
The method (2) has a problem that since it is a non-contact type, its thermal efficiency is poor and sufficient fixing property cannot be expected, and in order to increase the fixing speed, it is necessary to use a special binder resin. On the other hand, the method (3) is widely and generally used because it has good thermal efficiency, has a relatively excellent fixing property, and can be easily downsized.

In the fixing method using a heating roller, the surface of the heating roller and the surface of the molten toner on the image support, which is the member to be fixed, come into pressure contact with each other, so that the toner is fused to the heating roller and the paper or the like sent later is transferred. In some cases, a so-called offset phenomenon occurs, which shifts to the image support. Generally, since the lower limit fixing temperature is between the low temperature offset and the high temperature offset, the temperature range in which the fixing is actually possible is between the lower limit fixing temperature and the high temperature offset. Therefore, by lowering the fixing lower limit temperature as much as possible and raising the temperature at which high-temperature offset occurs as much as possible, the fixing temperature range can be expanded and low-temperature fixability can be imparted, so that the toner has low-temperature fixability and offset resistance. Always required.

More recently, full-color copying machines have been attracting attention, and it has become necessary to satisfy the required characteristics unique to full-color from the viewpoint of fixability. An image forming method for full-color copying is based on a three-color combining method such as a subtractive coloring method. Specifically, first, at least three types of electrostatic latent images are formed on a photoconductor by exposure, and then toner is added. Each color is developed a plurality of times and the transfer is repeated to form at least three different toner layers on the same image support such as paper. Then, the toner images thus superposed are fixed in one fixing step using a heating roller or the like. Compared to black and white development, which requires one development and transfer process, color development increases the thickness of the fixed image by the overlap of several types of toner layers, and if the film strength of the fixed image is low, the image will crack. May occur, the gloss may be impaired, or an image defect may occur when bent. Therefore, the fixed color toner is required to have appropriate gloss and excellent film strength. From the viewpoint of film strength, it is known that a polyester resin having a large molecular condensing power is excellent, but it is conceivable to increase the molecular weight as a means for further increasing the film strength. However,
Since the softening point of the toner is increased by such means, when the heating roller fixing method is adopted, a large amount of heat energy is lost to the image, and the low-temperature fixability is impaired.

By the way, the market of full-color copying machines is currently broadly expanded from office use to various design professionals or the light printing industry, and its application range is expanding further. However, in full-color copying machines currently commercialized, a releasing oil such as silicone oil or fluorine is used as a releasing agent for the purpose of promoting separation of toner from the roller during fixing, extending the life of the roller, and preventing offset. Ingenuity such as applying oil to a heating roller has been made, and in most cases, an oily release agent is applied in some form. The support of the color image fixed by a fixing device equipped with a coating device for coating these release agents has a release agent on the surface, so writing with a ball-point pen and adhesion of an adhesive tape are not possible. There is a problem that color reproducibility and transparency of a color image fixed on an OHP (overhead projector) sheet are significantly deteriorated. On the other hand, when the amount of the release agent applied is reduced, the release property is maintained to some extent at the beginning of use due to the smoothness and cleanliness of the roller surface. However, since the image area is large, in the case of a color copy image in which the toner coverage on a support such as paper is significantly larger than that of a black-and-white copy image, the releasability of the roller gradually decreases when the copying is repeated, and the offset Tends to occur.

Therefore, as a means for reducing the amount of release agent of the roller while maintaining the image gloss required for a full-color image, the viscoelasticity of the binder resin is increased and the surface cohesive force when the toner is melted is increased. Therefore, it has been attempted to impart releasability to the toner itself. However, in order to increase the viscoelasticity of the binder resin, increase the degree of polymerization of the polymer,
Alternatively, when a crosslinked structure is provided and a gel component is contained, the pulverizability is deteriorated accordingly. On the other hand, on the other hand, the particle size of toner has been reduced due to the demand for high image quality such as obtaining halftone gradation and graininess of digital images, and it is known that the preferable toner particle size is 9 μm or less. Is. However, when a binder resin having high viscoelasticity is used, there is a problem in that the production efficiency when obtaining the small-sized toner required for high image quality is lowered and the manufacturing cost is increased.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned actual situation in the prior art and aims to improve the situation. That is, an object of the present invention is to provide a toner for developing an electrostatic charge image that satisfies all the following requirements. (1) It has excellent releasability from the heat roller, and the amount of the release agent supplied can be made minute. (2) The fixed toner image has a fixing strength that does not cause image loss due to external stress such as bending, and is excellent in low-temperature fixing property and offset resistance. (3) Excellent pulverizability. Another object of the present invention is to provide an image forming method using a toner satisfying the above requirements.

[0008]

Means for Solving the Problems As a result of intensive studies conducted by the present inventors to achieve the above object, the above object can be achieved by using two specific polyesters as a binder resin for a color toner. This has led to the completion of the present invention. The toner for developing an electrostatic image of the present invention contains a colorant and a binder resin, and the binder resin comprises a first polyester and a second polyester. The weight ratio of the second polyester to the polyester is 70:30 to 30:70, and the first polyester has a number average molecular weight of 3,500 or more and less than 5,000 and a weight average molecular weight of 10,000 or more and 100,000.
Less than 0, softening point 90 to 130 ° C, glass transition point 6
0 to 75 ° C. and a THF insoluble content of 10% or less,
The second polyester has a number average molecular weight of 2,500 or more and less than 3,500, a weight average molecular weight of 8,000 or more and less than 50,000, a softening point of 90 to 130 ° C., and a glass transition point of 60 to 75 ° C. Is characterized in that.

Further, the image forming method of the present invention comprises a step of forming a latent image on the image forming member, a step of developing the latent image on the image forming member with a developer, and a step of developing the developed image on the transfer body. And a step of fixing the toner image on the transfer body, wherein the above-mentioned toner for developing an electrostatic image is used as a developer, and a releasing agent is applied to a heating roller in the fixing step. The amount of transfer of the release agent to the transfer member is 2.0 × 10 ^{−6 to} 2.0 × 10 ⁻⁵ by using a coating device for coating, a fixing device having a heating roller and an elastic roller (pressure roller). It is characterized in that the release agent is applied to the heating roller so as to be within the range.

Hereinafter, the present invention will be described in detail. First, the electrostatic image developing toner of the present invention will be described. In the present invention, the polyester resin used as the binder resin includes the first polyester and the second polyester having the above physical properties.
It is a mixture of polyester. Both of these polyesters can be manufactured from a polyhydric alcohol component and a polycarboxylic acid component. As the polyhydric alcohol component, as the dihydric alcohol component, ethylene glycol, propylene glycol, 1,4-butanediol,
2,3-butanediol, diethylene glycol, triethylene glycol, 1,5-pentanediol, 1,
6-hexanediol, neopentylene glycol,
1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, bisphenol A, hydrogenated bisphenol A, etc. can be used. Of these, bisphenol A, hydrogenated bisphenol A, and the like are preferably used, and the bisphenol A derivative represented by the following formula is particularly preferable.

[0011]

Embedded image (In the formula, R represents an ethylene group or a propylene group,
Both a and b are integers, and the sum of both is 2-7. ) As a specific example thereof, polyoxypropylene (6)-
2,2-bis (4-hydroxyphenyl) propane, polyoxyethylene (2.2) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (2.2) -2,2-bis ( 4-hydroxyphenyl)
Examples thereof include propane and polyoxypropylene (2.0) -polyoxyethylene (2.0) -2,2-bis (4-hydroxyphenyl) propane. Further, as trihydric or higher alcohol components, glycerin, sorbitol,
1,4-sorbitan, trimethylolpropane, etc. can be used.

Examples of the polycarboxylic acid component include maleic acid, maleic anhydride, fumaric acid, phthalic acid, terephthalic acid, isophthalic acid, malonic acid, succinic acid, glutaric acid, dodecenylsuccinic acid, n-octylsuccinic acid, n
-Dodecenyl succinic acid, 1,2,4-benzenetricarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid,
1,2,4-naphthalene tricarboxylic acid, 1,2,5-
Hexanetricarboxylic acid, 1,3-dicarboxyl-2
-Methyl-2-methylenecarboxypropane, tetra (methylenecarboxy) methane, 1,2,7,8-octanetetracarboxylic acid, trimellitic acid, pyromellitic acid and lower alkyl esters of these acids can be used.

The first polyester and the second polyester used in the present invention are required to have the following physical properties. First polyester (high molecular weight): number average molecular weight: Mn = 3,500 or more, less than 5,000, weight average molecular weight: Mw = 10,000 or more, 100,0
Less than 00 Softening point is 90 to 130 ° C, Glass transition point is 60 to 75
° C, THF insoluble content is 10% or less Second polyester (low molecular weight): Number average molecular weight: Mn = 2,500 or more, less than 3,500, Weight average molecular weight: Mw = 8,000 or more, 50,000
Less than Softening point 90 ~ 130 ℃, Glass transition point 60 ~ 75
℃,

When either the number average molecular weight or the weight average molecular weight of the first polyester is larger than the above range, the low temperature fixability and the glossiness of the fixing surface as a color image, and further the fine pulverizability are low. descend. On the other hand, when either the number average molecular weight or the weight average molecular weight is smaller than the above range, the anti-offset property is poor and the toner releasability from the heating roller is deteriorated when a minute amount of the releasing agent is supplied.

In the above second polyester, when either the number average molecular weight or the weight average molecular weight is larger than the above range, the low temperature fixing property and the glossiness of the fixing surface as a color image, and further the fine pulverizing property are obtained. descend. On the other hand, when either the number average molecular weight or the weight average molecular weight is smaller than the above range, not only the anti-offset property is poor, but also the strength of the fixed image is deteriorated, and further blocking is caused in the developing machine. Become.

Further, the first polyester and the second polyester
The polyester has a softening point (Tm) of 90 to 130 ° C., preferably the first polyester has a softening point of 100 to 130 ° C., and the second polyester has a softening point of 90 to 120 ° C. is there. When the softening point is lower than 90 ° C, the hot offset resistance is deteriorated. On the other hand, if the temperature is higher than 130 ° C., the fixability tends to be poor and the low temperature fixability is impaired.

Further, in the present invention, the difference in softening point Tm between the first polyester and the second polyester is 10-2.
It is preferably in the range of 0 ° C. When the difference in the softening point Tm is in the above range, the excellent properties of each polyester can be exhibited. However, when the difference in the softening point Tm is outside the above range, the first polyester and the polyester The development of the excellent properties of each of the polyesters of No. 2 is suppressed, and as a result, any one of the properties of offset resistance, releasability, low-temperature fixability, gloss of the fixing surface, and pulverizability tends to be impaired.

In the present invention, the glass transition point (Tg) of the first polyester and the second polyester is 6
It is necessary to be 0 to 75 ° C. When Tg is less than 60 ° C., the blocking resistance is deteriorated, while 7
When it is higher than 5 ° C, the pulverizability is lowered.

The first polyester is THF.
The (tetrahydrofuran) insoluble content must be 10% or less. When the THF insoluble content exceeds 10%, the gloss, low temperature fixability and pulverizability of the fixing surface deteriorate. However, when the THF insoluble content is less than 2%, the offset resistance and the peeling property become insufficient, and when it exceeds 7%, the gloss, low temperature fixability and pulverizability of the fixing surface may deteriorate. , THF insoluble matter is preferably 2 to 7%. Further, the second polyester is preferably non-linear, and the one having a THF insoluble content in the range of 0.1 to 5% is preferable from the viewpoint of film strength.

The mixing ratio (weight) of the first polyester and the second polyester is 70:30 to 30:
It is necessary to be 70, and particularly preferably 60:40 to 40:60. When the compounding ratio of the first polyester is more than 70, low temperature fixing property and glossiness and pulverizability of the fixing surface are deteriorated, while when the compounding ratio of the first polyester is less than 30, a very small amount. Initially, the toner releasability from the heating roller under the supply of the releasing agent is good, but it rapidly deteriorates as tens of thousands of copies are made, and the hot offset resistance becomes insufficient.

In the present invention, as the colorant to be contained in the toner together with the polyester resin, known colorants can be mentioned. For example, carbon black, aniline blue, calcoil blue, chrome yellow, ultramarine blue, DuPont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue,
Malachite Green Oxalate, Lamp Black, Rose Bengal, C.I. I. Pigment Red 48: 1,
C. I. Pigment Red 122, C.I. I. Pigment Red 57: 1, C.I. I. Pigment Yellow 9
7, C.I. I. Pigment Yellow 12, C.I. I. Pigment Yellow 17, C.I. I. Pigment Blue 1
5: 1, C.I. I. Pigment Blue 15: 3 can be illustrated as a typical example. In the present invention,
The content of the colorant is preferably in the range of 2% by weight to 8% by weight. When the content of the colorant is less than 2% by weight, the coloring power is weakened, and when it is more than 8% by weight, the transparency of the color toner is deteriorated.

Further, a releasing agent may be added to the toner of the present invention in order to complete offset resistance. Further, in order to improve the durability, fluidity or cleaning property of the toner, if necessary, silica,
Resin fine particles such as titanium oxide, fluorine-based resin, polyethylene fine particles, and acrylic resin fine powder may be added as an external additive.

Next, the image forming method of the present invention will be described. The image forming method of the present invention comprises a step of forming a latent image on an image forming member, a step of developing a latent image on the image forming member with a developer, a step of transferring the developed image onto a transfer body, It has a step of fixing the toner image on the transfer body,
The step of forming a latent image on the image forming member can be carried out by a conventionally known method. As the image forming member, an electrophotographic photosensitive member and a dielectric can be used. For example, when an electrophotographic photosensitive member is used as the image forming member, the electrostatic latent image may be formed by uniform charging and image exposure. The formed electrostatic latent image is then visualized in the developing process, and the above-mentioned toner for developing an electrostatic image is used as a developer so that a thin layer is formed on the developer carrying member by a layer regulating member, for example. When the electrostatic latent image developing toner is charged, the charged electrostatic image developing toner is attached to the electrostatic latent image on the latent image carrier to visualize the electrostatic latent image. The formed toner image is transferred by a conventional method,
For example, it is transferred onto paper and then fixed in a fixing step.

In the present invention, in the fixing step,
A coating device for applying a release agent to the heating roller, a fixing device having a heating roller and an elastic roller is used, and the transfer amount of the release agent to the transfer body is 2.0 × 10 ^−6.
Fixing is carried out by applying a release agent to the heating roller so that the release agent is in the range of 2.0 × 10 ⁻⁵ g / cm ² . When the coating amount of the release agent is less than 2.0 × 10 ⁻⁶ g / cm ² , the releasability and body offset property are deteriorated, while when it exceeds 2.0 × 10 ⁻⁵ cm ^2. Causes a problem that it becomes impossible to write a ballpoint pen on a fixed image or attach an adhesive tape.

FIG. 1 shows a schematic structure of a fixing device which can be used in the present invention. The main part of the fixing device is composed of a pressure roller 1 and a heating roller 2, and a transfer body carrying a color toner image 11 passes between the rollers. The heating roller has a structure in which an inner elastic body layer 6 and an outer elastic body layer 3 are provided on a metal core having a heating source 9 therein. Further, the pressure roller has a structure in which the inner elastic body layer 4 and the outer elastic body layer 5 are provided on a metal core having a heating source 9 therein. A release agent supply means is provided on one side of the heating roller 2. That is, the release agent 10 contained in the release agent container is supplied to the surface of the release agent applying roller 8 via the release agent supplying auxiliary section 12 and the release agent supplying roller 7, and then the applying roller 8 and From the outer elastic layer 3 of the heating roller in contact with the transfer roller, the transfer member is applied to the surface of the transfer member when passing between the pressure roller and the heating roller.

As the release agent used in the present invention, an organopolysiloxane represented by the following general formula (1) is suitable. (R) _a SiO _{(4-a) / 2} (1) (In the formula, R represents an alkyl group or an aryl group having 1 to 8 carbon atoms, and a is 1.95 <a <2.20. )

In the organopolysiloxane represented by the general formula (1), the substituent R is specifically a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group or an octyl group. And one or more kinds of hydrocarbon groups selected from an aryl group such as a phenyl group and a tolyl group, and the like, preferably the following general formula (2)

Embedded image (However, in the formula, n is an integer of 0 to 1000.) As a particularly preferred specific example, dimethylpolysiloxane (R = CH ₃ ) can be mentioned. Further, modified products thereof, for example, amino-modified or mercapto-modified polysiloxane and the like can be mentioned.

[0028]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. (Manufacture of Polyester) A polyhydric alcohol component and a polycarboxylic acid component having the raw material compositions shown in Table 1 were placed in a four-neck round bottom flask equipped with a stainless steel stirrer, a glass nitrogen gas introduction pipe, and a flow-down condenser. Then, the flask was set in a mantle heater. Then, nitrogen gas was introduced through the gas introduction pipe, and the temperature was raised while maintaining the inside of the flask in an inert gas atmosphere. After that, raw material mixture 1
Dibutyltin oxide (0.05 g) was added to 00 g, and the reaction was performed for a predetermined time while keeping the temperature of the reaction product at 200 ° C. After that, a trivalent carboxylic acid was added and reacted, and Mn = 3500 to 4500 in GPC measurement.
A first polyester was obtained by terminating the reaction at the point of. Similarly, the second polyester was obtained by terminating the reaction at Mn = 2500-3500. The composition of the synthesized resin is shown in Table 1, and the characteristics of the obtained resin are shown in Table 2. The molecular weight distribution was measured by the GPC method using tetrahydrofuran (THF) as a solvent. The softening point Tm is the elevated flow tester [CFT-5
00] (manufactured by Shimadzu Corporation) and the diameter of the pores of the die is 1 m
m, a pressure of 10 kg / cm ² , and a temperature rising rate of 3 ° C./min, and a temperature corresponding to ½ of the height from the outflow start point to the end point when a 1 cm ³ sample was melted and flown out. did. Further, the glass transition point Tg is measured by using a differential scanning calorimeter (manufactured by JEOL Ltd.) for a sample that has been previously heat-treated in a constant temperature chamber at 40 ° C. for 17 hours under conditions of a heating rate of 10 ° C./min. In addition, the temperature at the intersection of the extension line of the base line below the glass transition point and the tangent line showing the maximum inclination between the peak apex was taken.

[0029]

[Table 1]

[0030]

[Table 2]

A combination of C.I. I. Pigment Red 57: 1 was added in an amount of 16 parts by weight to 100 parts by weight of the binder resin, melted and kneaded in a Henschel mixer, cooled, pulverized by a jet type fine pulverizer, and then by an inertial force classifier. By classification, a toner having a particle size of 7 μm was obtained (Examples 1 to 8). To 100 parts by weight of these toners, 1.5 parts by weight of titanium oxide fine particles were added and mixed with a Henschel mixer to obtain a toner for developing an electrostatic image for evaluation.

Using the above toner, the following (1) to (6)
Was evaluated. The fixing property and offset property were evaluated as follows. That is, 5 parts of each of the above toners and 100 parts of resin-coated ferrite fine particles (average particle size 50 μm) are mixed to prepare a two-component developer, which is used in a commercially available electrophotographic copying machine (A-colo).
r630, manufactured by Fuji Xerox Co., Ltd.) was used for copying to obtain an unfixed image. Then, using a fixing device shown in FIG. 1, that is, an external fixing machine including a heating roller having a surface layer formed of silicone rubber and a pressure roller having a silicone rubber layer coated with a fluorine-based resin, a fixing temperature of 120 to The image fixing property and offset property were evaluated while increasing stepwise between 220 ° C. At this time, dimethylpolysiloxane was supplied to the heating roller 2 as a release agent, and the amount of oil transferred to the transfer body was 1.8 × 10 ⁻⁵ g /
It was adjusted to be cm ² .

(1) Evaluation of low temperature fixability The low temperature fixability was evaluated by the minimum fixing temperature. (2) Evaluation of Film Strength Regarding the film strength, after fixing a 25 mm × 25 mm solid image at 160 ° C., it was bent using a weight with a constant load, and the degree of image loss in that portion was qualitatively evaluated. (Evaluation Criteria) G1: There is no image defect. G2: A line-like mark remains on the bent portion, but there is no image loss and there is no problem. G3: White lines appear in places at the bent portions, and the image is missing. G4: Image loss occurs in areas other than the bent portion. (3) Hot offset property The hot offset property was evaluated by the hot offset generation temperature. (4) Evaluation of Storage Stability Regarding blocking resistance, the ratio of aggregates was evaluated after each toner was allowed to stand under conditions of 50 ° C. and 50% relative temperature for 24 hours. The evaluation criteria are as follows. ⊚: no agglomeration observed, ∘: less than 0.5 wt% of agglomerates, Δ: 0.5 to less than 2% of agglomerates, × ... 2% or more

(5) Evaluation of initial peeling property With respect to a solid image of 4 cm × 8 cm, the fixing temperature is increased stepwise between 120 ° C. and 220 ° C., and the image is lost by the peeling claw provided in the fixing device. The grade and the degree of residual nail marks were evaluated. (Evaluation Criteria) G1: Image loss due to the peeling nail and residual nail mark are not confirmed over the entire temperature range. G2: After fixing, some nail marks are seen in the entire temperature range, but this is not a problematic level. G3: In a certain temperature range, a nail due to a peeling nail is conspicuously seen in the fixed image. G4: Paper wrinkles due to the peeling claw or image loss due to the peeling claw is remarkable. (6) Crushability Using a jet type crusher, the crushing ability for obtaining a crushed particle size of 7 μm is based on the sample of Example 1 as k standard. Was evaluated as x.

The results are shown in Table 3.

[Table 3]

As is clear from Table 3, in the case of the example, the low temperature fixing property, the offset resistance and the peeling property are superior to those of the comparative example, and moreover, the fixed solid image can withstand bending and the like. It has sufficient film strength to obtain. Further, the storage stability is good, and the pulverizability suitable for producing a toner having a small particle size is remarkably improved.

Next, 5 parts each of the toners of Examples 1 to 3 and Examples 9 and 10 shown in Table 4 below and 100 parts of resin-coated ferrite particles (average particle size 50 μm) were mixed to prepare a two-component developer. Was prepared and an unfixed solid image of 5 cm × 10 cm was obtained using a commercially available electrophotographic copying machine (A-color 630, manufactured by Fuji Xerox Co., Ltd.). Next, using a fixing device shown in FIG. 1, that is, an external fixing machine including a heating roller having a surface layer formed of silicone rubber and a pressure roller having a silicone rubber layer coated with a fluororesin, a release agent Under different oil application amounts shown in Table 4, a fixing test was repeatedly performed at 160 ° C., and the peelability (long-term peelability) after fixing 10,000 sheets and the possibility of writing with a ballpoint pen were evaluated.

(Long-term releasability) G1: Even after fixing 10,000 sheets, there is no winding around the roller or offset, and there is no problem in releasability. G2: A slight offset phenomenon began to be seen from about 7,000 sheets, and wrapping occurred up to 10,000 sheets. G3: A remarkable offset phenomenon began to be seen from about 5,000 sheets, and thereafter, wrapping constantly occurred. (Ballpoint pen writing) Evaluation criteria are as follows. ○: writable, △: ink is hazy in some places, making it difficult to write. ×: Writable (no ink is deposited).

(Transparency of OHP) 4 cm on OHP sheet
An unfixed solid image of × 5 cm was formed, and the transparency of OHP after fixing at 160 ° C. was visually evaluated according to the following criteria. A: Both color reproducibility and transparency are excellent. B: There is no particular problem in color reproducibility, but the saturation is lowered and the transparency is slightly poor. C: Color reproducibility and transparency are poor, and the OHP transparent image looks dull overall. (Comprehensive Evaluation) O: Good color reproducibility, OHP transparency, and writability, and excellent oilless property and color image. Δ: Color image characteristics are good, but suitability for less oil is poor. X: Color image and suitability for less oil are inferior.

The results are shown in Table 4.

[Table 4] In Table 4, the oil type “dimethyl oil” is dimethyl polysiloxane. As is clear from this table, the example is superior to the comparative example in long-term releasability due to repetition, enables writing with a ballpoint pen on a fixed image, and
The HP transparent image had no dullness and had excellent transparency.

[0041]

EFFECT OF THE INVENTION In the toner for developing an electrostatic charge image of the present invention, by using as a binder resin, a polyester resin in which two kinds of polyester resins having specific physical properties are mixed in a specific ratio, peeling in fixing with a heating roller is performed. Sex, OHP
The transparency of the image can be improved. Further, since the coating amount of the release agent is reduced on the fixed image surface obtained by the image forming method of the present invention, it is possible to write with a writing instrument.

[Brief description of drawings]

FIG. 1 is a side cross-sectional explanatory view of a fixing device used to carry out the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Pressure roller, 2 ... Heating roller, 3, 5 ... Outer elastic body layer, 4, 6 ... Inner elastic body layer, 7 ... Release agent supply roller, 8 ... Release agent application roller, 9 ... Heating source, 10 ... Release agent, 11 ... Toner image, 12 ... Release agent supply auxiliary section.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masanori Ichimura 1600 Takematsu, Minamiashigara City, Kanagawa Prefecture Fuji Xerox Co., Ltd.

Claims (2)

[Claims] 1. An electrostatic charge image developing toner comprising a colorant and a binder resin, wherein the binder resin comprises a first polyester and a second polyester, and the first polyester and the second polyester. With the weight ratio of 70:30 to 3
0:70, the first polyester has a number average molecular weight of 3,500 or more and less than 5,000, a weight average molecular weight of 10,000 or more and less than 100,000, a softening point of 90 to 130 ° C., glass The transition point is 60 to 75 ° C., and the THF insoluble content is 10% or less. The second polyester has a number average molecular weight of 2,500 or more and less than 3,500 and a weight average molecular weight of 8,000 or more, 50, A toner for developing an electrostatic charge image, which has a softening point of 90 to 130 ° C and a glass transition point of 60 to 75 ° C. 2. A step of forming a latent image on an image forming member, a step of developing a latent image on the image forming member with a developer, a step of transferring the developed image to a transfer body, and a transfer body. In the image forming method including the step of fixing the toner image of
As a developer, a colorant and a binder resin are contained, and the binder resin is composed of a first polyester and a second polyester,
The weight ratio of the first polyester to the second polyester is 70:30 to 30:70, and the first polyester has a number average molecular weight of 3,500 or more and less than 5,000.
A weight average molecular weight of 10,000 or more and less than 100,000, a softening point of 90 to 130 ° C., a glass transition point of 60 to 75 ° C., and a THF insoluble content of 10% or less;
The polyester has a number average molecular weight of 2500 or more, 35
Less than 00, weight average molecular weight of 8,000 or more, 50,000
A toner having a softening point of less than 00, a softening point of 90 to 130 ° C. and a glass transition point of 60 to 75 ° C., and in a fixing step, a coating device, a heating roller and an elastic roller for applying a release agent to the heating roller. Using the fixing device, the release agent is applied to the heating roller so that the transfer amount of the release agent to the transfer body is in the range of 2.0 × 10 ^{−6 to} 2.0 × 10 ^−5. Image forming method.