JPH09138525A - Image forming method and toner therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming method and the toner therefor satisfying both low-temp. fixability and hot preservability and ensuring a fixing temp. range. SOLUTION: In a fixing device in which a toner image T is heat-fixed by passing between two rolls 1, 2, the thickness of the roll 1 brought into contact with a toner image supporting face S is <=1.0mm and an image forming method in which surface pressure (load on the rolls/contact area) applied between the rolls 1, 2 is <=1.5×10<5> Pa is adopted. A toner contg. a resin compsn. consisting of two kinds of polyester resins (A), (B) and contg. a discontinuous phase formed by the resin A in the resin B is used.

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 and an image forming toner used for developing an electrostatic latent image such as an electrophotographic method, an electrostatic recording method, an electrostatic printing method, and the like. The present invention relates to an image forming method and an image forming toner for the purpose of achieving both low-temperature fixability and heat storability and ensuring a fixing temperature range.

[0002]

2. Description of the Related Art Conventionally, as an electrophotographic method, US Pat. No. 2,297,691 and Japanese Patent Publication No. 49-23910.
Various methods are described in JP-B No. 43-24748 and JP-B No. 43-24748. Generally, a photoconductive substance is used to form an electric latent image on a photoconductor by various means.
Then, the latent image is developed with toner, and the toner powder image is transferred to paper or the like as required, and then fixed by heating, pressurizing, solvent vapor or the like to obtain a copy image.

The methods for developing an electric latent image are roughly classified into a liquid development method using a developer in which various pigments and dyes are finely dispersed in an insulating organic liquid, and a cascade method.
There is a dry developing method using a toner in which a colorant such as carbon black is dispersed in a natural or synthetic resin, such as a magnetic brush method and a powder cloud method, and the dry developing method has been widely used in recent years.

As a fixing method in the electrophotographic method, a heating heat roller method is widely used because of its good energy efficiency. Further, the thermal energy applied to the toner at the time of fixing tends to be small as in low temperature fixing or high speed copying for energy saving in recent years. In response to this, the fixing device has been improved, and in order to improve the thermal energy efficiency, an attempt has been made to make the thickness of the roller on the side in contact with the toner image supporting surface 1.0 mm or less.
This fixing device made the energy efficiency extremely high. However, the mechanical strength of the rollers themselves becomes weak, and when a large load is applied between the rollers, the rollers are deformed, so that a large load cannot be applied. For this reason, the toner used in such a fixing device is required to have a low temperature fixing that is incomparable with conventional toner.

For the toner used for such low temperature fixing, it has been attempted to improve the low temperature fixing property by using a resin or wax having a low softening point. However, such a low-temperature fixing toner is known to cause so-called blocking, which is hardened by the heat of the machine used and the heat during storage because it is thermally weak. Further, it is also difficult to secure a sufficient fixing temperature range, and even if a polyester resin which is said to have relatively good heat storage property despite having good low temperature fixing property is used, a toner still solving this problem can still be obtained. Not not.

To solve these problems, several methods using two kinds of polyester resins having different characteristics have been proposed. For example, a method of mixing a non-linear polyester resin and a linear polyester resin (Japanese Patent Application Laid-Open No. 6-68242)
0-90344), Tg of 50 ° C. or higher, and softening point of 20.
A method of mixing a crosslinked polyester resin at 0 ° C. or lower with a linear polyester resin having a softening point of 150 ° C. or lower and MW of 3,000 to 50,000 (JP-A-64-15755),
A method of containing a non-linear polymer polyester resin having a MW of 5,000 or more and a dispersion ratio of 20 or more and a non-linear polyester resin having a MW of 1,000 to 5,000 and a dispersion ratio of 4 or less (JP-A-2-82267); A method of containing an organometallic compound composed of a linear polyester resin having an acid value of 5 to 60 and a non-linear polyester resin having an acid value of less than 5 (Japanese Patent Laid-Open No. 3-2.
No. 29264), a method of mixing different polyester resins with saturated polyester resins having different acid value ratios of 1.5 or more (JP-A-3-41470), and the like. However, in recent years, low-temperature fixing has been more and more progressed, and when the above-mentioned thin roller and low-load low-temperature fixing device are used, the above-mentioned technique can secure sufficient low-temperature fixing property and fixing temperature range. Compatibility with heat preservation is becoming difficult.

[0007]

SUMMARY OF THE INVENTION Therefore, a first object of the present invention is to provide an image forming method and an image forming toner which are compatible with low-temperature fixability and heat storability. A second object is to provide an image forming method and a toner for forming an image in which a fixing temperature range is secured.

[0008]

As a result of intensive studies, the inventors of the present invention used an image forming method with a specific thickness and a specific surface pressure, and used two kinds of polyester resins having different characteristics relating to the method. In this way, the inventors have found that the first and second problems described above can be solved, and have found that the characteristics of the toner can be improved by the dispersed state of the two types of polyester resins having different characteristics, and have reached the present invention.

That is, according to the present invention, firstly, in the image forming method of fixing the toner image by heating, the toner image supporting surface is passed by passing the support carrying the toner image between the two rollers. An image characterized in that the thickness of the fixing roller on the side in contact with the roller is 1.0 mm or less, and the surface pressure (roller load / contact area) applied between the two rollers is 1.5 × 10 ⁵ Pa or less. A method of forming is provided. Secondly, in the toner used in the first image forming method, the resin component is composed of two kinds of polyester resins,
Moreover, there is provided an image-forming toner characterized in that the polyester resin A forms a discontinuous phase in the polyester resin B. Thirdly, the second polyester resin is characterized in that the glass transition temperature and the molecular weight of the polyester resin A are higher than those of the polyester resin B, and the polyester resin A contains a resin containing a tetrahydrofuran insoluble component. An image forming toner is provided. Fourthly, the image forming toner described in the above third, wherein the polyester resin A has an acid value of less than 20 mgKOH / g and the polyester resin B has an acid value of 20 mgKOH / g or more. Provided. Fifth, there is provided the image forming toner described in the third or fourth, wherein the polyester resin B has a glass transition temperature of 52 to 60 ° C. Sixth, there is provided the toner for image formation described in any one of the third to fifth, wherein the content of tetrahydrofuran insoluble matter in the polyester resin A is 5 to 60% by weight. Seventh, there is provided the image-forming toner as described in any one of the third to sixth, which further contains a free fatty acid type carnauba wax as the resin component. Eighth, there is provided the image forming toner as described in any one of the above third to seventh, wherein the resin component further contains a hydrogenated petroleum resin having a hydrogenation rate of 50% or more. .

In the toner of the present invention, the resin component is composed of two kinds of polyester resins, and the polyester resin A
Since a discontinuous phase is formed in the polyester resin B, the toner image is fixed in the fixing device by passing the support carrying the toner image between the two rollers. The thickness of the fixing roller on the side in contact with the supporting surface is 1.0 mm or less, and the surface pressure (roller load / contact area) applied between the two rollers is 1.5 × 10 ^5.
Even when it is used in a fixing device having a pressure of Pa or less, both low-temperature fixability and storability can be achieved and a fixing temperature range can be secured.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The fixing device used in the present invention is
Basically, a support carrying a toner image is passed through between two rollers to heat and fix the toner image, and for example, has a configuration shown in FIG. In FIG. 1, 1 is a fixing roller and 2 is a pressure roller. The fixing roller 1 has RTV, silicone rubber, tetrafluoroethylene-perfluoroalkyl vinyl ether (PFA), polytetrafluoroethylene on the surface of a metal cylinder 3 made of a good heat conductor such as aluminum, iron, stainless steel or brass. An offset prevention layer 4 made of (PTFE) or the like is covered. A heating lamp 5 is arranged inside the metal cylinder 3. . The metal cylinder 6 of the pressure roller 2 is often made of the same material as the metal cylinder 3 of the fixing roller 1, and its surface is covered with an offset prevention layer 7 made of PFA, PTFE or the like. Also,
Although not necessary, a heating lamp 8 is arranged inside the pressure roller 2. Although not shown, the fixing roller 1 and the pressure roller 2 are pressed against each other by springs at both ends,
Rotate. Between the fixing roller 1 and the pressure roller 2, a support S (transfer paper such as paper) to which the toner image T is attached is passed to perform fixing.

The fixing device used in the present invention improves the temperature rise characteristic of the fixing roller by setting the thickness of the metal cylinder of the fixing roller to 1.0 mm or less. Can be launched. The preferable thickness of the metal cylinder varies depending on the strength and thermal conductivity of the material used, but is 0.2 to 0.7.
mm is preferred. The load (contact pressure) applied between the fixing roller and the pressure roller is preferably 1.5 × 10 ⁵ Pa or less. The surface pressure is a value obtained by dividing the load applied to both ends of the roller by the roller contact area. The roller contact area is
Between the rollers heated to the fixing temperature, pass a sheet whose surface property greatly changes due to heating, such as OHP paper,
It is stopped halfway and discharged after several tens of seconds, and the area of the portion where the surface property has changed is determined. A higher roller surface pressure is more advantageous for fixing a toner image, but in the fixing device having the metal cylinder thickness of 1.0 mm or less, a large load is not applied because it causes distortion of the roller, and the load is 1 .5 x 1
0 ⁵ Pa or less, preferably 0.4 to 1.0 × 10 ⁵
Pa or less.

In the toner used in the present invention, polyester resin A forms a discontinuous phase in polyester resin B as a resin component. The polyester resin used in the present invention is obtained by polycondensation of alcohol and carboxylic acid. Examples of the alcohol used include glycols such as ethylene glycol, diethylene glycol, triethylene glycol and propylene glycol, etherified bisphenols such as 1.4-bis (hydroxymethyl) cyclohexane and bisphenol A, and other divalent alcohols. Examples thereof include monomers and trihydric or higher polyhydric alcohol monomers. Examples of the carboxylic acid include maleic acid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid, succinic acid, malonic acid and other divalent organic acid monomers, 1,2,4-benzenetricarboxylic acid, 1 , 2,5-benzenetricarboxylic acid, 1,
2,4-cyclohexanetricarboxylic acid, 1,2,4-
Trivalent or higher polyvalent carboxylic acid such as naphthalenetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methylenecarboxypropane, 1,2,7,8-octanetetracarboxylic acid Mention may be made of the quantity.

In the present invention, it is necessary to form a discontinuous phase in the polyester resin. Here, the discontinuous phase is 2
It means a state in which two or more kinds of phases are dispersed without being mixed with each other, and the shape of each phase does not matter. By forming such a discontinuous phase, unlike those consisting of a continuous phase,
The different characteristics of each phase are exhibited, and it becomes possible to secure the low temperature fixing property and the fixing temperature range and improve the heat storability.
When it does not form a discontinuous phase, it exhibits intermediate properties of the resin consisting of a continuous phase, and secures low temperature fixability and fixing temperature range,
No improvement in heat preservation is achieved. The size of the resin forming the discontinuous phase (dispersion diameter) is 2 to 500 μm. When it is less than 2 μm, the heat storability is deteriorated. If it exceeds 500 μm, it becomes difficult to secure the low temperature fixability and the fixing temperature range. The dispersion diameter is observed by a transmission electron microscope (TEM) after making the toner into a thin layer using a microtome. In this method, the center of the dispersed resin, which is the main component, cannot always be captured, but it can be measured by increasing the number of samples. There is no particular difficulty in making the polyester resin a discontinuous phase, and it can be adjusted by the kneading conditions (temperature, time, etc.) and the compounding ratio. The ratio of the polyester resin A and the polyester resin B is A / B = 10/90 to 70/30, preferably 25/75 to 60/40.

The glass transition temperature (hereinafter sometimes abbreviated as Tg) and molecular weight of the polyester resin A must be higher than those of the polyester resin B. The Tg of the polyester resin A and the molecular weight ensure a fixing temperature range, and the Tg of the polyester resin B and the molecular weight aim at low temperature fixing. Therefore, when the molecular weights of Tg of polyester resins A and B are the same as or opposite to each other (B is higher), such an effect cannot be obtained. Polyester resin A
It is preferable that the weight average molecular weight of is 3,000 to 50,000 and the Tg is 54 to 65 ° C. Also, polyester resin B
The weight average molecular weight of is preferably 2,000 to 40,000. When the molecular weight and Tg of the polyester resin exceed the above ranges, problems occur in low temperature fixing property, securing of fixing temperature range and heat storability. The Tg of the polyester resin B is particularly important, and it is particularly preferable to set it in the range of 52 to 60 ° C. When the temperature is lower than 52 ° C, the heat storability is deteriorated, and when the temperature is higher than 60 ° C, the low temperature fixing property tends to be deteriorated. The weight average molecular weight of the present invention was measured by gel permeation chromatography (GPC). The glass transition temperature Tg was measured by a differential scanning calorimeter (DSC).
The weight average molecular weight of the polyester resin A is a value excluding insoluble matter of tetrahydrofuran (hereinafter sometimes abbreviated as THF).

The acid value of the polyester resin A used in the present invention is preferably less than 20 mgKOH / g, particularly preferably in the range of 0.1 to 18 mgKOH / g. When the acid value is 20 mgKOH / g or more, the dependency of the toner charge amount on the environment (particularly humidity) becomes large. The acid value of the polyester resin B is preferably 20 mgKOH / g or more, more preferably 25 to 600 mgKOH / g. When the acid value is less than 20 mgKOH / g, the adhesive force between the support such as paper and the toner becomes weak, and the low temperature fixing property tends to deteriorate.

The THF insoluble content of the polyester resin A is 5
It is preferably 60% by weight, more preferably 10 to 50% by weight. The THF insoluble matter is obtained by dissolving the polyester resin A in THF, separating the insoluble matter by filtering with a 250-mesh wire net, and measuring the ratio. If the THF insoluble content is less than 5% by weight, the fixing temperature range becomes narrow,
If it exceeds 60% by weight, the low temperature fixability tends to deteriorate.

It is effective for the toner of the present invention to contain free fatty acid type carnauba wax as a resin component. The free fatty acid-type carnauba wax is a product obtained by removing free fatty acids from ordinary carnauba wax, and as a result, the dispersion in the toner becomes small and an excellent releasing effect is exhibited. Particularly in the present toner, the release agent is preferably dispersed in the polyester resin B, and the released free fatty acid type carnauba wax can be dispersed extremely uniformly. The amount of the free fatty acid type carnauba wax added to the toner is 2 to 20% by weight, preferably 3 to 10% by weight.
It is.

Further, in the present invention, it is effective to contain a hydrogenated petroleum resin having a hydrogenation rate of 50% or more as a resin component of the toner. The hydrogenated petroleum resin used in the present invention preferably has a hydrogenation rate of 50% or more, more preferably 75% or more. Even if the hydrogenation rate is less than 50%, the low temperature fixability is not a problem, but the heat storability is deteriorated. The composition of the hydrogenated petroleum resin is preferably composed of dicyclopentadiene and a C _{6 to} C ₈ aromatic hydrocarbon. The petroleum resin is obtained by refining a cracked oil fraction that is by-produced when producing ethylene, acetylene, propylene and the like by naphtha cracking, and is, for example, C _{5 to} C ₆
Aliphatic petroleum resins, aromatic petroleum resins C ₆ -C _8, aliphatic - there is an aromatic polymer type petroleum resin. The main raw materials include cyclopentadiene and higher olefin hydrocarbons. In the present invention, it is particularly preferable to use a petroleum resin composed of dicyclopentadiene and a C _{6 to} C ₈ aromatic hydrocarbon.
Petroleum resins having other compositions have no problem in low-temperature fixability, but tend to have poor heat storability.

The ring-and-ball softening point of the hydrogenated petroleum resin used in the present invention is preferably in the range of 90 to 140 ° C, more preferably 100 to 130 ° C. When the softening point is less than 90 ° C, the low temperature fixability is not a problem, but the heat storability tends to decrease. When the softening point is higher than 140 ° C., there is no problem in heat storability, but there is a tendency that low temperature fixability is deteriorated.
The ring and ball softening point is measured according to JIS K6863-1.
The measurement was performed according to 994 (Test method for softening point of hot melt adhesive). The content of the hydrogenated petroleum resin of the present invention as a toner resin component is preferably 5 to 50 parts by weight, more preferably 5 to 30 parts by weight. When the content is less than 5 parts by weight, the effect of improving low temperature fixability is small and the effect of improving productivity by improving pulverizability is small. On the contrary, when the content exceeds 50 parts by weight, the heat storability is deteriorated.

In the present invention, as the resin component in the toner, a resin other than the polyester resin may be used in combination within the range not impairing the performance of the toner. Examples of resins that can be used in this case include the following. Polystyrene, chloropolystyrene, poly α-methylstyrene, styrene / chlorostyrene copolymer, styrene / propylene copolymer, styrene / butadiene copolymer, styrene / vinyl chloride copolymer, styrene / vinyl acetate copolymer, styrene / Maleic acid copolymer, styrene / acrylic acid ester copolymer (styrene / methyl acrylate copolymer, styrene / ethyl acrylate copolymer, styrene / butyl acrylate copolymer, styrene / octyl acrylate copolymer Polymer, styrene / phenyl acrylate copolymer, etc., styrene / methacrylic acid ester copolymer (styrene / methyl methacrylate copolymer, styrene / ethyl methacrylate copolymer, styrene / butyl methacrylate copolymer, styrene / Phenyl methacrylate copolymer, etc.), styrene Styrene resin such as / α-methyl chloroacrylate copolymer, styrene / acrylonitrile / acrylic ester copolymer (homopolymer or copolymer containing styrene or styrene substitution product),
Vinyl chloride resin, styrene / vinyl acetate copolymer, rosin-modified maleic acid resin, phenol resin, epoxy resin, polyethylene resin, polypropylene resin, ionomer resin, polyurethane resin, silicone resin, ketone resin, ethylene / ethyl acrylate copolymer, Xylene resin, polyvinyl butyral resin, etc. These resins are not limited to being used alone, but may be used in combination of two or more kinds. Further, the production method thereof is not particularly limited, and any of bulk polymerization, solution polymerization, emulsion polymerization and suspension polymerization can be used.

The toner of the present invention comprises, in addition to the resin components such as the above polyester resin, free fatty acid type carnauba wax, and hydrogenated petroleum resin, a colorant, a charge control agent, and other release agent, if necessary. It is also possible to add a fluidity improver or the like. As the colorant, for example, carbon black,
Lamp Black, Iron Black, Aniline Blue, Phthalocyanine Blue, Phthalocyanine Green, Hansa Yellow G, Rhodamine 6C Lake, Chalco Oil Blue, Chrome Yellow, Quinacridone, Benzidine Yellow, Rose Bengal, Triallyl methane dyes, etc.
Any conventionally known dyes and pigments can be used alone or in combination. The amount of these colorants used is usually 1 to 30% by weight, preferably 3 to 20% by weight, based on the toner resin component.

As the charge control agent, any conventionally known polarity control agent such as a nigrosine dye, a metal complex salt type dye and a quaternary ammonium salt can be used alone or in combination. The amount of these polarity control agents used is 0.1 to 10 parts by weight, preferably 1 to 5 parts by weight, based on the toner resin component.

As the releasing agent other than the free fatty acid type carnauba wax, any conventionally known releasing agent such as solid silicone varnish, higher fatty acid higher alcohol, montan ester wax, oxidized rice wax, low molecular weight polypropylene wax and the like can be used. Can also be mixed and used. The amount of these release agents used is 1 to 20 with respect to the toner resin component.
Parts by weight, preferably 3 to 10 parts by weight.

As the fluidity improver, any conventionally known fluidity improvers such as silicon oxide, titanium oxide, silicon carbide, aluminum oxide and barium titanate can be used alone or in combination. The amount of these fluidity improvers used is 0.1 to 5 parts by weight, preferably 0.5 to 2 parts by weight, based on the weight of the toner.

The method for producing the toner of the present invention may be a conventionally known method, such as polyester resin, released free fatty acid type carnauba wax, hydrogenated petroleum resin and other resin components, and if necessary, a coloring agent and charge control. After mixing the agents and the like with a mixer or the like, the mixture is melted and kneaded with a kneader such as a hot two-roll or an extruder, cooled and solidified, and this is crushed and classified with a crusher such as a jet mill. Thereafter, if necessary, the fluidity improver may be mixed using a mixer or the like.

[0027]

The present invention will now be described in more detail by way of examples, which should not be construed as limiting the invention. In addition, all the parts shown below are based on weight.

Example 1 <Preparation of Toner> 45 parts of polyester resin (A) (weight average molecular weight of 2,000, Tg of 62 ° C., THF insoluble content of 0%, acid value of 25 mgKOH / g) Polyester resin (B) of 53 parts ( Weight average molecular weight 15,500, Tg 50 ° C., acid value 15 mgKOH / g) Low molecular weight polypropylene 5 parts (Viscor 550P: Sanyo Chemical Co., Ltd.) Carbon black 10 parts (# 44: Mitsubishi Kasei Co.) Metal complex salt dye 2 parts The mixture of the above materials was kneaded using an extruder. The kneaded product was crushed by jet crushing and then classified to obtain a toner having a volume average particle size of 10.5 μm. To 100 parts of this toner, 0.5 part of silicon oxide (R-972: manufactured by Nippon Aerosil Co., Ltd.) was mixed using a Henschel mixer to obtain a toner of Example 1.

Example 2 <Preparation of Toner> 45 parts of polyester resin (A) (weight average molecular weight 12,000, Tg 59 ° C., THF insoluble content 3%, acid value 25 mgKOH / g) Polyester resin (B) 38 parts ( Weight average molecular weight 15,500, Tg 50 ° C., acid value 5 mgKOH / g) Low molecular weight polypropylene 5 parts (Viscor 550P: Sanyo Chemical Co., Ltd.) Carbon black 10 parts (# 44: Mitsubishi Kasei Co.) Metal complex salt type dye 2 parts As in Example 1, the mixture of the above materials was kneaded using an extruder. The kneaded product was crushed by jet crushing and then classified to obtain a toner having a volume average particle size of 10.5 μm. To 100 parts of this toner, silicon oxide (R
-972: manufactured by Nippon Aerosil Co., Ltd.) was mixed with a Henschel mixer to obtain a toner of Example 2.

Comparative Example 1 <Preparation of Toner> 42 parts of polyester resin (A) (weight average molecular weight 15,000, Tg 61 ° C., THF insoluble content 0%, acid value 25 mgKOH / g) polyester resin (B) 41 parts ( Weight average molecular weight 8,000, Tg 63 ° C., THF insoluble matter 0%, acid value 15 mg KOH / g) Low molecular weight polypropylene 5 parts (Viscor 550P: Sanyo Chemical Co., Ltd.) Carbon black 10 parts (# 44: Mitsubishi Kasei Co., Ltd.) Metal complex salt type dye 2 parts As in Example 1, a mixture of the above materials was kneaded using an extruder. The kneaded product was crushed by jet crushing and then classified to obtain a toner having a volume average particle size of 10.5 μm. To 100 parts of this toner, silicon oxide (R
-972: manufactured by Nippon Aerosil Co., Ltd.) was mixed with a Henschel mixer to obtain a toner of Comparative Example 1.

Comparative Example 2 <Preparation of Toner> 83 parts of polyester resin (weight average molecular weight 8,500, Tg 55 ° C., THF insoluble content 0%, acid value 20 mgKOH / g) Low molecular weight polypropylene 5 parts (Viscole 550P: Sanyo Kasei) Carbon black 10 parts (# 44: Mitsubishi Kasei Co., Ltd.) Metal complex salt type dye 2 parts As in Example 1, a mixture of the above materials was kneaded using an extruder. The kneaded product was crushed by jet crushing and then classified to obtain a toner having a volume average particle size of 10.5 μm. To 100 parts of this toner, silicon oxide (R
-972: manufactured by Nippon Aerosil Co., Ltd.) was mixed with a Henschel mixer to obtain a toner of Comparative Example 2.

<Evaluation of low-temperature fixability> A two-component developer was prepared with 3.0 parts of toner and 97.0 parts of a silicone-coated carrier, and the fixing temperature was changed with Imagio Mf530 (a copying machine manufactured by Ricoh Co.) to obtain a Macbeth density. Image density of 1.2
I got a copy of the image. The copy image at each temperature was rubbed 10 times with a clock meter equipped with a sand eraser, the image density before and after the rubbing was measured, and the fixing ratio was determined by the following formula. (Image density after 10 times of sand eraser) / (Previous image density) x 1
00 = Fixing rate (%) The temperature at which the fixing rate is 70% or more is the lower limit fixing temperature. The lower limit temperature for fixing conventional toner is about 150 to 170 ° C.

<Evaluation of fixing temperature range> A two-component developer was prepared with 3.0 parts of toner and 97.0 parts of silicone coat carrier, and Imagio Mf530 (a copying machine manufactured by Ricoh Co., Ltd., but with the silicone oil application function removed). Check the occurrence of hot offset on the image by changing the fixing temperature with). The range from the lower limit fixing temperature to the hot offset generation temperature is called the fixing temperature range. The fixing temperature range of the conventional toner is about 150 to 200 ° C.

<Evaluation of heat storability> A glass container is filled with toner and left in a constant temperature bath at 60 ° C. for 4 hours. This toner is cooled to 24 ° C. and subjected to a penetration test (JIS K2235
-1991) to measure penetration. The larger the value, the better the storage stability against heat. This value is 5m
If it is less than m, there is a high possibility that a problem will occur during use.

Example 3 <Preparation of Toner> 45 parts of polyester resin (A) (weight average molecular weight 12,000, Tg 59 ° C., THF insoluble content 3%, acid value 5 mgKOH / g) polyester resin (B) 38 parts ( Weight average molecular weight 5,500, Tg 50 ° C., acid value 25 mgKOH / g) Low molecular weight polypropylene 5 parts (Viscor 550P: Sanyo Chemical Co., Ltd.) Carbon black 10 parts (# 44: Mitsubishi Kasei Co.) Metal complex salt dye 2 parts As in Example 1, the mixture of the above materials was kneaded using an extruder. Next, the kneaded product was jet-pulverized and classified using a jet pulverizer to obtain a toner having a volume average particle diameter of 10.5 μm. To 100 parts of this toner, silicon oxide (R-972: manufactured by Nippon Aerosil Co., Ltd.)
0.5 part was mixed using a Henschel mixer to obtain the toner of Example 3.

Example 4 <Preparation of Toner> 45 parts of polyester resin (A) (weight average molecular weight 10,000, Tg 59 ° C., THF insoluble content 3%, acid value 5 mgKOH / g) polyester resin (B) 38 parts ( Weight average molecular weight 4,500, Tg 55 ° C., acid value 25 mgKOH / g) Low molecular weight polypropylene 5 parts (Viscor 550P: Sanyo Chemical Co., Ltd.) Carbon black 10 parts (# 44: Mitsubishi Kasei Co.) Metal complex salt type dye 2 parts As in Example 1, the mixture of the above materials was kneaded using an extruder. Next, the kneaded product was jet-pulverized and classified using a jet pulverizer to obtain a toner having a volume average particle diameter of 10.5 μm. To 100 parts of this toner, silicon oxide (R-972: manufactured by Nippon Aerosil Co., Ltd.)
0.5 part was mixed using a Henschel mixer to obtain the toner of Example 4.

Example 5 <Preparation of Toner> 45 parts of polyester resin (A) (weight average molecular weight 15,000, Tg 59 ° C., THF insoluble matter 45%, acid value 5 mgKOH / g) polyester resin (B) 38 parts ( Weight average molecular weight 4,000, Tg 55 ° C., acid value 35 mg KOH / g) Low molecular weight polypropylene 5 parts (Viscor 550P: Sanyo Chemical Co., Ltd.) Carbon black 10 parts (# 44: Mitsubishi Kasei Co.) Metal complex salt type dye 2 parts As in Example 1, the mixture of the above materials was kneaded using an extruder. Next, the kneaded product was jet-pulverized and classified using a jet pulverizer to obtain a toner having a volume average particle diameter of 10.5 μm. To 100 parts of this toner, silicon oxide (R-972: manufactured by Nippon Aerosil Co., Ltd.)
0.5 part was mixed using a Henschel mixer to obtain the toner of Example 5.

Example 6 <Preparation of Toner> 45 parts of polyester resin (A) (weight average molecular weight 15,000, Tg 59 ° C., THF insoluble matter 45%, acid value 5 mgKOH / g) polyester resin (B) 38 parts ( Weight average molecular weight 4,000, Tg 55 ° C., acid value 35 mg KOH / g) Free fatty acid type carnauba wax 5 parts (melting point 82 ° C., acid value 1) carbon black 10 parts (# 44: Mitsubishi Kasei Co.) metal complex salt Type Dye 2 parts As in Example 1, a mixture of the above materials was kneaded using an extruder. Next, the kneaded product was jet-pulverized and classified using a jet pulverizer to obtain a toner having a volume average particle diameter of 10.5 μm. To 100 parts of this toner, silicon oxide (R-972: manufactured by Nippon Aerosil Co., Ltd.)
0.5 part was mixed using a Henschel mixer to obtain the toner of Example 6.

Example 7 <Preparation of Toner> 40 parts of polyester resin (A) (weight average molecular weight 15,000, Tg 59 ° C., THF insoluble matter 45%, acid value 5 mgKOH / g) Polyester resin (B) 33 parts ( Weight average molecular weight 4,000, Tg 55 ° C., acid value 35 mg KOH / g) Hydrogenated petroleum resin (softening point 110 ° C., hydrogenation rate 95%, 10 parts composition dicyclopentadiene + aromatic type) Defreeized fatty acid type carnauba Wax 5 parts (melting point 82 ° C., acid value 1) Carbon black 10 parts (# 44: manufactured by Mitsubishi Kasei Co.) Metal complex salt type dye 2 parts As in Example 1, a mixture of the above materials was kneaded using an extruder. did. Next, the kneaded product was jet-pulverized and classified using a jet pulverizer to obtain a toner having a volume average particle diameter of 10.5 μm. To 100 parts of this toner, silicon oxide (R-972: manufactured by Nippon Aerosil Co., Ltd.)
0.5 part was mixed using a Henschel mixer to obtain the toner of Example 7.

The toners of Examples 1 to 7 and Comparative Examples 1 and 2 were evaluated for low-temperature fixability, fixing temperature range, and heat storability, and the results are summarized in Table 1.

[0041]

[Table 1]

It can be seen from Table 1 that the toner of the present invention is superior to the toner of the comparative example in low-temperature fixability, secures a sufficient fixing temperature range, and has good heat storability.

[0043]

According to the image forming method of the first aspect of the present invention, in the fixing device for fixing the toner image by heating, the fixing member carrying the toner image is passed between the two rollers and is brought into contact with the toner image supporting surface. The thickness of the fixing roller is 1.0mm
Since the surface pressure (roller load / contact area) applied between the two rollers is 1.5 × 10 ⁵ Pa or less, the method according to the present invention has a low temperature fixability, a constant temperature and a sufficient temperature. It is possible to obtain an image in which the fixing temperature range is secured and the heat storability is good.

The image forming toner according to claim 2 is characterized in that the resin component is composed of two kinds of polyester resins, and the polyester resin A forms a discontinuous phase in the polyester resin B. The image forming toner of item 3 is the polyester resin of claim 2, wherein the polyester resin A has a higher glass transition temperature and a higher molecular weight than those of the polyester resin B, and
Since these toners contain a resin containing a tetrahydrofuran insoluble matter, when these toners are used in the image forming method of claim 1, more favorable low temperature fixing property and fixing temperature range can be secured, and further heat storage is possible. It is possible to obtain an image with good properties.

In the image forming toner of claims 4 to 6, the acid value of the polyester resin A is less than 20 mgKOH / g, and the acid value of the polyester resin B is 20 mgK.
OH / g or more, and / or the glass transition temperature of the polyester resin B is 52 to 60 ° C., or /
And the content of tetrahydrofuran insoluble matter in the polyester resin A is 5 to 60% by weight,
The low-temperature fixability, the fixing temperature range and the heat storability are further improved.

The image-forming toner according to claims 7 to 8 further contains, as the resin component, a free fatty acid type carnauba wax and / or a hydrogenated petroleum resin having a hydrogenation rate of 50% or more. Therefore, the low temperature fixability, the fixing temperature range and the heat storability are further improved.

[Brief description of the drawings]

FIG. 1 is a schematic view of a fixing device used in the present invention.

[Explanation of symbols]

 1 Fixing Roller 2 Pressure Roller 3 Metal Cylinder 4 Offset Preventing Layer 5 Heating Lamp 6 Metal Cylinder 7 Offset Preventing Layer 8 Heating Lamp T Toner Image S Support (Transfer Paper such as Paper)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masanori Suzuki Inc. 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Akihiro Koban 1-3-6 Nakamagome, Ota-ku, Tokyo Stock company Ricoh

Claims (8)

[Claims] 1. In an image forming method for heating and fixing a toner image by passing a support carrying a toner image between two rollers, the thickness of the fixing roller on the side in contact with the toner image supporting surface is The surface pressure (roller load / contact area) applied between the two rollers of 1.0 mm or less is 1.5 ×
An image forming method characterized by being 10 ⁵ Pa or less. 2. The toner used in the image forming method according to claim 1, wherein the resin component is composed of two kinds of polyester resins, and the polyester resin A forms a discontinuous phase in the polyester resin B. An image forming toner characterized by the following. 3. The polyester resin according to claim 2,
An image forming toner, wherein the polyester resin A has a higher glass transition temperature and a higher molecular weight than those of the polyester resin B, and further contains a resin containing a tetrahydrofuran insoluble component in the polyester resin A. 4. The acid value of the polyester resin A is 20 m.
less than gKOH / g and said polyester resin B
4. The image forming toner according to claim 3, wherein the acid value is 20 mgKOH / g or more. 5. The image forming toner according to claim 3, wherein the glass transition temperature of the polyester resin B is 52 to 60 ° C. 6. The toner for image formation according to claim 3, wherein the content of tetrahydrofuran insoluble matter in the polyester resin A is 5 to 60% by weight. 7. The image-forming toner according to claim 3, further comprising free fatty acid type carnauba wax as the resin component. 8. The toner for image formation according to claim 3, further comprising a hydrogenated petroleum resin having a hydrogenation rate of 50% or more as the resin component.