JPH0713752B2 - Toner for electrophotography - Google Patents

Description

The present invention relates to a toner used in electrophotography, electrostatic printing and the like, and more particularly to an electrostatic charge developing toner suitable for a heat fixing method.

Conventionally, as electrophotography, many methods are known as described in U.S. Pat.No. 2,297,691, Japanese Patent Publication No. 42-23,910 and Japanese Patent Publication No. 43-24,748. After forming an electric latent image on the photoconductor by various means using a conductive substance, developing the latent image with a toner, and transferring the toner image to a transfer material such as paper, if necessary. It is fixed by heating or pressure to obtain a copy.

Various developing methods are also known in which an electric latent image is visualized using toner.

For example, the magnetic brush method described in U.S. Pat. Many developing methods such as developing methods are known. As a toner used in these developing methods, a fine powder in which a dye or a pigment is dispersed in a natural or synthetic resin has been conventionally used. Further, it is known to use a developing fine powder to which a third substance is added for various purposes.

The developed toner image is transferred and fixed on a transfer material such as paper, if necessary.

As a method for fixing the toner image, a method of heating and melting the toner by a heater or a heat roller to fuse and solidify it on the support, a method of softening or dissolving the binder resin of the toner with an organic solvent and fixing it on the support, pressurization There is known a method of fixing the toner to the support by the method.

Toners are selected with materials suitable for each fixing method,
Generally, the toner used for a particular fixing method cannot be used for another fixing method. In particular, it is almost impossible to transfer the toner used in the heat fusion fixing method using a heater, which has been widely used in the past, to the heat roller fixing method, the solvent fixing method, the pressure fixing method and the like. Therefore, toner suitable for each fixing method has been researched and developed.

Various magnetic recording methods are known in which a magnetic latent image is formed and developed with a magnetic toner.

Various methods and devices have been developed for the process of fixing a toner image on paper, but the most common method at present is
This is a so-called thermal roll fixing method in which heat and pressure are applied simultaneously, and this is a method of fixing the toner image on the image receiving sheet by bringing the image receiving sheet carrying the toner image into contact with a heated roller. However, when such a fixing system is used, the conventional toner causes problems such as so-called offset. Offset is an undesirable phenomenon in which a part of the toner carried on the image receiving sheet is transferred to the roller surface.

That is, in recent years, a heat roll type fixing system having a good thermal efficiency has come to dominate the commercial copying machines as the efficiency of copying operations, the energy saving, and the miniaturization and high performance of copying machines have increased. Most of these copiers try to fix the toner on the paper by thermocompression bonding with a heating roller.The non-contact heating method using heat rays allows the heating element to obtain a satisfactory fixed image at a lower temperature. Although there are many advantages such as higher speed and the like, this method also has various drawbacks. As one of the big things, when the roller is kept at a temperature at which the toner should be sufficiently fixed to the holding member such as paper, the toner is fused not only on the paper but also on the heat roll,
Due to this, the heat roll becomes dirty as the copying is repeated, and the blade or the cleaning web that should keep the roll clean cannot completely remove it, and eventually the paper is also soiled. It has serious problems.

Various measures have been attempted for fixing devices and toners in order to solve or alleviate this problem, but they have not been sufficiently solved yet.

As the fixing device, a material such as Teflon or silicon having excellent surface peeling property is used. Alternatively, a device such as applying oil such as silicone oil to the roller has been made, and most of the heat roller fixing devices of currently commercialized copying machines apply oil in some form. However, the oil application causes problems such as oil stains on the sheet and troubles due to complication of the fixing device and an increase in cost.

As a toner, a method of adding a small amount of wax such as low-molecular weight polyethylene or polypropylene that is sufficiently melted when heated to increase the peeling property is used, but it is effective in preventing offset, but aggregation of the toner However, it is difficult to say that this is sufficient, because adverse effects such as instability, instability of charging characteristics, and deterioration of durability have been observed. As other methods, various attempts have been made to improve the binder resin. Japanese Patent Publication No. 51-23354 discloses a toner using a crosslinked polymer as a binder resin. According to that method, there is a remarkable improvement in offset resistance and scuffing resistance, but on the other hand, if the degree of cross-linking is increased, the fixing point will rise, and the fixing temperature will be low enough that offset resistance and scuffing resistance will be low. Good and good fixability has not been obtained.
And, the cross-linked polymer is difficult to disperse the pigment and is difficult to be compatible with other polymers, so that the toner using the cross-linked polymer as a binder resin is difficult to obtain good developing characteristics. There is.

As described above, it is the reality that a toner having a charge-separation property, sufficient fixing at a low temperature, and storage stability is not yet obtained in a fixing roller to which oil is not applied.

By the way, recently, low molecular weight amorphous polyester resins and epoxy resins have been attracting attention as adhesives suitable for low temperature fixing. Attempts to use a polyester resin as a binder for toner have been made, for example, in Japanese Patent Publication No. Sho 46-12680 (USP.
3,590,000 specification), JP-B-52-25420 (USP.3,6)
81,106) and the like. According to these descriptions and the experiments and studies by the inventors, the fixing temperature can be certainly lower in the toner using the polyester resin as the main binder than other materials, but the offset phenomenon to the heat roller is sufficiently prevented. Not something you can do.

The main idea so far regarding the prevention of offset in a toner using a polyester resin as a main binder is, as typified by JP-B-52-25420, mixing a trivalent or higher valent polyol and a polyacid to form a polymer. It is intended to improve the offset property at the time of fixing by linearizing it and improving its viscoelasticity.The present inventors have also studied various examples of these, but it is true that these non-linearizations cause offset property. Although it is effective for improvement, this is also similar to the improvement measure by crosslinking in styrene type, and if the non-linearization is carried out until sufficient offset resistance is achieved, the fixing point rises and the polyester type has The result was that the low temperature fixability was almost impaired.

Therefore, this non-linearization attempt should be considered only in terms of offset prevention, but it is not preferable in view of the fixing point and high-speed fixability, and it was found that non-linearization naturally has its limits.

However, the present inventors have found that a non-linear polyester containing a dicarboxylic acid or a diol substituted with a relatively long-chain alkyl group alone or a mixture thereof in order to prevent an increase in the fixing point due to the non-linearization, and a non-linear polyester thereof. In that case, a sufficiently low fixing point can be obtained, but on the other hand, various resins in combination with linear polyester, which has a problem in offset property, are used as a binder resin. As a result, a binder resin that has an effect of preventing offset and is suitable for high-speed fixing by lowering the fixing point was found, and the present invention was completed.

The objects of the present invention are listed below.

1. An object of the present invention is to provide a dry toner suitable for a heat roll fixing method that does not apply oil.

2. It is an object of the present invention to provide a toner that can be sufficiently fixed at a lower temperature and can be reduced in energy, is particularly suitable for high-speed fixing, sufficiently prevents offset, and has a wide fixable temperature range. is there.

3. An object of the present invention is to provide a toner having an acceptable agglomeration temperature and free from blocking during storage and use.

4. An object of the present invention is to provide a toner having stable triboelectric properties under various humidity conditions and good moisture resistance.

5. It is an object of the present invention to provide a toner which has a sufficient image density, is bright and clear, has a high resolution, and has an image quality without fog or the like and having excellent developing characteristics.

6. An object of the present invention is to provide a toner having excellent durability against repeated use and capable of stably maintaining the high-quality image described in the preceding paragraph.

7. An object of the present invention is to provide a toner having excellent powder characteristics such as fluidity and cohesiveness, and good replenishment and storage stability.

8. An object of the present invention is to provide a toner having a high degree of abrasion resistance against mechanical load during the developing process and having excellent impact resistance.

9. It is an object of the present invention to provide a toner having a good transfer rate capable of being easily transferred from an electrostatic image forming surface to an image receiving surface, and having excellent transferability without image irregularity and non-uniformity during transfer. It is in.

10. An object of the present invention is to provide a toner which does not adhere to the toner holding member or the electrostatic latent image and is not contaminated.

11. An object of the present invention is to provide a toner having almost no carrier contamination in a two-component developer due to adhesion to the carrier, fusion and the like.

12. An object of the present invention is to provide a one-component magnetic toner having good dispersibility of magnetic powder.

13. An object of the present invention is to provide a toner having a good cleaning property of the photosensitive surface by causing mechanical abrasion of the electrostatic image forming surface.

14. An object of the present invention is to provide a toner which is easy to manufacture, can be stably produced, and is low in cost.

15. It is an object of the present invention to provide a toner having a high commercial value, which is excellent in overall characteristics in which various performances required for the toner are balanced.

Specifically, the present invention relates to (A) polyoxypropylene-ized, or polyoxypropylene- and polyoxyethylenated etherified bisphenol having 50% or more of oxypropylene groups, and a divalent aromatic compound. Non-linear polyesters 50 to 95 obtained by reacting a mixture of a carboxylic acid and a trivalent or more aromatic carboxylic acid, and an alkyl-substituted dicarboxylic acid, an alkyl-substituted diol or a mixture of an alkyl-substituted dicarboxylic acid and an alkyl-substituted diol
An electron characterized by containing as a binder resin a mixture containing 50% by weight of a linear polyester obtained by reacting (B) polyoxypropyleneated bisphenol with a divalent carboxylic acid. The present invention relates to photographic toner.

In the polyester resin of the present invention, the non-linear polyester (A) is mainly composed of aromatic dicarboxylic acids and aromatic polycarboxylic acids represented by phthalic acids as the acid component among the acid components and alcohol components constituting the polyester. In addition, as the alcohol component, an etherified bisphenol mixture is mainly used.

In particular, the etherified bisphenol is composed mainly of polyoxypropyleneized bisphenol and is partially mixed with polyoxyethylenated bisphenol. And
In addition to these, as a component, an alkyl-substituted dicarboxylic acid or diol is particularly contained.

The advantage of introducing an aromatic group into polyester is great in terms of the generation of triboelectric charge of the insulating electrophotographic toner and the ability to retain the triboelectric charge, as is conventionally known for vinyl polymers and the like. Furthermore, the thermal properties during fixing are also large, and the amorphous non-linear structuring by introducing an aromatic polycarboxylic acid raises the Tg (glass transition point) of the polyester, and a low melting point blocking-free and offset-free binder for toner. It is a big element to use as. at the same time,
The non-linearity of the polyester makes the toner harder and contributes greatly to the durability.

In the linear polyester (B), a dicarboxylic acid, preferably an aliphatic carboxylic acid, is used as the acid component, and the polyoxypropylene bisphenol among the etherified bisphenols is used as the alcohol component.
This linear polyester has a great influence on the fixability of the toner, and is effective in lowering the fixing point by mixing a small amount with the binder resin. On the other hand, a large amount of the compound is apt to cause offset and contamination due to the adhesion of the toner to the fixing device roll. The use of the mixture of the non-linear polyester (A) and the linear polyester (B) as the binder resin for the toner is one of the advantages of the high Tg hard resin, which is an advantage of the offset resistance and durability, and the soft resin on the other hand. Both of the improvement of the fixing property due to the above are satisfied, and therefore, the selection of the mixing ratio of the resin is effective and particularly important for carrying out the present invention. The composition ratio of the linear polyester (B) is preferably 5 to 50% by weight, more preferably 7 to 40% by weight, and the non-linear polyester (A) is preferably 50 to 95% by weight, More preferably, it is 60 to 90% by weight. The non-linear polyester always gives a better result when the ratio in the binder resin is higher than that of the linear polyester.

Examples of the divalent aromatic carboxylic acid as the carboxylic acid used in the polyester of the present invention include phthalic acid, isophthalic acid,
There are phthalic anhydride, terephthalic acid, and their derivatives such as esters, and examples of trivalent or higher aromatic polycarboxylic acids include 1,2,4-benzenetricarboxylic acid and 1,2,5-benzenetricarboxylic acid. , 1,2,4 naphthalene tricarboxylic acid, 2,5,7 naphthalene tricarboxylic acid, 1,2,4,5benzenetetracarboxylic acid, or their anhydrides or esterified products. The amount of trivalent or higher aromatic polycarboxylic acid preferably does not exceed 40 mol% of the acid component.

Examples of the divalent aliphatic carboxylic acid include maleic acid, fumaric acid, succinic acid, adipic acid, sebacic acid,
Itaconic acid etc.

In addition, an acid component can be used as long as the object of the present invention is not impaired.

The etherified bisphenol used in the present invention is mainly an etherified bisphenol obtained by etherifying bisphenol, and in particular, a polyoxypropylene compound, or a polyoxypropylene compound and a polyoxyethylene compound. These have 2-3 moles of oxypropylene or oxyethylene per cell of bisphenol. Specific examples include polyoxypropylene 2,2
-Bis (4-hydroxyphenyl) propane, polyoxypropylene 2,2-bis (4-hydroxy, 2,6-dichlorophenyl) propane, polyoxyethylene (1,0)-
Examples include polyoxypropylene (1,5) -bis (4-hydroxyphenyl) propane.

Particularly useful in the present invention are polyoxypropyleneated bisphenols, preferably containing no polyoxyethylenated bisphenols or containing polyoxypropyleneated bisphenols in a molar amount not exceeding the amount of polyoxypropyleneated bisphenols. In the case of a bisphenol which has been subjected to both types of alkoxylation, i.e., polyoxyethylenated, it is preferable that the polyoxyethylenated amount does not exceed the polyoxypropyleneated amount. That is, in the case of a toner composition using a polyester using an etherified bisphenol in which polyoxyethylenated bisphenol accounts for 50% or more, it is clear that the toner composition under high humidity is better than that using a polyoxypropyleneized bisphenol. Is inferior. It is presumed that this reflects the difference in hydrophilicity and hygroscopicity of the obtained toner composition. That is, the toner using the polyoxyethylenated bisphenol in excess of the etherified bisphenol has a high hygroscopicity under high humidity of the toner, so that the triboelectrification property is deteriorated, resulting in poor developing performance and consequently a decrease in image density. Therefore, the ratio of polyoxypropylene groups in etherified bisphenol is 50.
% Or more is essential.

The etherified bisphenol can be obtained by directly adding ethylene oxide or propylene oxide to diphenol or by reacting an olefin halohydrin with diphenol.

As other alcohol component, if necessary, for example, ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, glycerin, trimethylol, as long as the present invention is not impaired. Aliphatic polyols such as ethane, trimethylolpropane and pentaerythritol, and alicyclic polyols such as 1,4-cyclohexanediol and 1,4-cyclohexanedimethanol can be used.

The polyester used in the present invention has a glass transition temperature of 50 to 80 ° C.
A softening point of 60 to 130 ° C is desirable. If the glass transition temperature exceeds 80 ° C or the softening point exceeds 130 ° C, excessive heat energy is required during heat fixing, and high-speed heat fixing properties tend to deteriorate. When the softening point is less than 60 ° C, the offset resistance at the time of fixing is lowered, and the number average molecular weight is preferably 2,000 to 20,000, more preferably 3,000 to 10,000. If the molecular weight is less than 2,000, the heat fixing roller is used. The releasability to the mold deteriorates and an offset phenomenon occurs, and conversely, when it exceeds 20,000, the fixing force tends to decrease together with the increase in the softening point.

The acid value of the polyester used is preferably 10 to 10
It is 0, and more preferably 10 to 60. When the acid value is less than 10, the toner obtained is insufficient in offset at the time of heat fixing, and the releasability from the fixing roller becomes poor. On the other hand, when it exceeds 100, the toner obtained has poor fixability or is easily affected by humidity, resulting in poor images under high humidity.

As the binder of the toner of the present invention, other known binder resins may be mixed and used as long as the performance of the present invention is not impaired. For example, there are polyester resins, epoxy resins, styrene-acrylic resins, butyral resins, styrene-butadiene resins and the like which are not included in the present invention.

Examples of the alkyl-substituted dicarboxylic acid used in the present invention include succinic acid, maleic acid, fumaric acid, and their acid anhydrides in which an alkyl group having 6 to 18 carbon atoms is substituted. A larger amount can effectively lower the fixing point by adding a small amount, but if the action is too strong, blocking of the toner occurs in a low temperature range, so the amount must be strictly within the above range.

As the alkyl-substituted diol, glycols substituted with an alkyl group having 6 to 18 carbon atoms can be equally used.
Especially ethylene glycol is preferable. It has the same effects as those of the alkyl-substituted dicarboxylic acid.

A charge control agent, a colorant, and a fluidity modifier may be added to the toner of the present invention as necessary. The charge control agent and the fluidity modifier are mixed (externally added) with the toner. You may use.
This charge control agent includes metal-containing dyes, nigrosine, etc., conventionally known dyes / pigments can be used as colorants, and fluidity modifiers include colloidal silica, fatty acid metal salts, etc. .

Further, when it is desired to obtain a magnetic toner, magnetic fine particles may be added to the toner. Does the magnetic substance show magnetism,
Any material that can be magnetized, such as iron, manganese, nickel, cobalt, chromium, and other fine metal powders, various ferrites, alloys and compounds such as manganese, and other ferromagnetic alloys such as magnetite, are conventionally known as magnetic materials. What is present can be used appropriately.

Further, polyolefins such as low molecular weight polyethylene and low molecular weight polypropylene can be added to the toner in order to make the releasability from the heat fixing roll more complete.

Hereinafter, the present invention will be specifically described with reference to a resin producing agent, examples, and comparative examples, but these do not limit the present invention in any way. All used parts are parts by weight.

[Production Example-1 of Non-Linear Polyester] 545 parts of polyoxypropylene (2,5) -2,2-bis (4-hydroxyphenyl) propane were placed in a four-necked flask, and a stirrer, condenser, thermometer, gas Set the introduction tube and place it in the mantle heater. After replacing the inside of the reaction vessel with nitrogen gas, when the contents were adjusted to 50 to 60 ° C,
135 parts of terephthalic acid, 77 parts of succinic acid (C ₁₆ H ₃₀ O ₄ ) substituted with a C ₁₂ alkyl group, and 38 parts of trimellitic acid are added so that the amount of carboxyl group is 0.9 equivalent to 1 equivalent of hydroxyl group. The mixture system is heated to 210 ° C. with stirring. After removing the water of reaction, after about 5 hours, the reaction is followed by measuring the acid value every hour in order to see the end point of the reaction. When the acid number is about 30, the reaction is cooled to room temperature.

[Production Example-2 of Non-Linear Polyester] Polyoxypropylene (2,
5) -2,2-bis (4-hydroxyphenyl) propane 54
Put 5 parts in a flask, replace with nitrogen and heat at 50 ° C. To this are added 135 parts of isophthalic acid, 77 parts of succinic acid substituted with a C ₁₂ alkyl group, and 38 parts of trimellitic acid, and the mixture is heated and stirred at 210 ° C. to react, and after completion of the reaction, it is cooled to room temperature.

[Production Example-3 of Non-Linear Polyester] According to the same method as in Production Example 1, 545 parts of polyoxypropylene (2,5) -2,2-bis (4-hydroxyphenyl) propane was placed in a flask and replaced with nitrogen. Heat at 50 ° C. To this, 108 parts of terephthalic acid, 24 parts of adipic acid, 77 parts of succinic acid substituted with a C ₁₂ alkyl group, and 38 parts of trimellitic acid are added, and the mixture is heated and stirred at 210 ° C. to react. After completion of the reaction, it is cooled to room temperature.

[Production Example-4 of Non-Linear Polyester] In the same manner as in Production Example 1, 436 parts of polyoxypropylene (2,5) -2,2-bis (4-hydroxyphenyl) propane and 18 parts of glycerin were placed in a flask. Fill nitrogen and replace 5
Heat to 0 ° C. To this, 179 parts of terephthalic acid and 77 parts of succinic acid substituted with a C ₁₂ alkyl group were added, and the mixture was heated and stirred at 210 ° C. to react. After completion of the reaction, it is cooled to room temperature.

[Production Example-5 of Non-Linear Polyester] Polyoxypropylene (2,5) -2,2-bis (4-hydroxyphenyl) propane (436 parts) and a C ₃ alkyl group were prepared in the same manner as in Production Example 1. 64 parts of the substituted ethylene glycol (C ₁₀ H ₂₂ O ₂ ) is placed in a flask and replaced with nitrogen, and heated to 50 ° C. 179 parts of terephthalic acid, 38 parts of trimellitic acid
Parts are added and the mixture is heated to about 210 ° C. with stirring to react. After completion of the reaction, it is cooled to room temperature.

[Production Example-6 of Non-Linear Polyester] According to the same method as in Production Example 1, 545 parts of polyoxypropylene (2,5) -2,2-bis (4-hydroxyphenyl) propane was placed in a flask and purged with nitrogen. Heat to 50 ° C.
To this, 112 parts of terephthalic acid and 95 parts of trimellitic acid are added, and the mixture is heated and stirred at about 210 ° C. to react. After completion of the reaction, it is cooled to room temperature.

[Production Example-7 of Non-Linear Polyester] According to the same method as in Production Example 1, polyoxypropylene (2,
5) -2,2-bis (4-hydroxyphenyl) propane 54
Put 5 parts in a flask and replace with nitrogen, and heat to 50 ° C. To this, 135 parts of terephthalic acid and 155 parts of succinic acid substituted with a C ₁₂ alkyl group are added, and the mixture is heated and stirred at about 210 ° C. to react. After completion of the reaction, it is cooled to room temperature.

(Production Example-1 of Linear Polyester) The fumaric acid 18 was added to the acid component of Production Example 1 of non-linear polyester.
Replace with 5 parts and heat mix the mixture system at 210 ° C. to remove water of reaction. The reaction ends when the acid value reaches 20,
Cool the resin to room temperature. At this time, the softening point was 108 ° C.

(Production Example-2 of Linear Polyester) According to the same method as in Production Example 1 of non-linear polyester,
The acid component was replaced with 120 parts of maleic anhydride, dehydrated and condensed, and the reaction was stopped at an acid value of 25 to obtain a linear polyester.

(Production Example-3 of linear polyester) The acid component of Production Example 1 of non-linear polyester was converted into succinic acid 12
A linear polyester was obtained in the same manner as in Production Example 1 for linear polyester except that the amount was changed to 5 parts. The softening point of the obtained polyester was 112 ° C.

Example 1 70 parts of non-linear polyester of Production Example 1 30 parts of linear polyester of Production Example 65 parts of magnetite (Fe ₃ O ₄ ) 5 parts A mixture of 5 parts of low molecular weight polypropylene was kneaded by heating with a roll. After allowing this to cool, it was made into a coarsely pulverized product, finely pulverized by an ultrasonic jet mill, and classified by an air classifier to obtain toner particles having an average diameter of about 13 μm. By adding colloidal silica (Aerosil R-972) to this toner and supplying it to a one-component developing type electrophotographic copying machine (Canon NP-400RE), and performing a copy test, sufficient image density and 50,000 sheets or more Development durability was obtained, and no problem in fixing property occurred. In addition, for the purpose of closely examining the heat fixing property, only the fixing unit of the copying machine was separately prepared, and a separately prepared unfixed image on the transfer paper was subjected to a fixing test by changing the roller set temperature with this separate fixing device. The offset phenomenon did not occur in the temperature range, and the fixability was excellent. 50 more of this toner
After leaving it in an atmosphere of ℃ for a long time, no blocking or caking was observed. Further, there was no problem with the developability in a high humidity atmosphere and the developability in a low humidity atmosphere.

Example 2 A toner was obtained in the same manner as in Example 1 except that the non-linear polyester in Example 1 was replaced with that in Production Example 2. The obtained toner was tested in the same manner as in Example 1. As a result, it showed excellent image properties, particularly image density and sharpness, and sufficient fixability and storability.

Example 3 Non-linear polyester of Production Example 3 80 parts Linear polyester of Production Example 6 20 parts Magnetite (Fe ₃ O ₄ ) 60 parts A mixture of polyethylene wax 3 parts was heated and kneaded with a roll. This was coarsely pulverized, finely pulverized, and classified to obtain toner particles of 5 to 20 μm. When colloidal silica was added to this toner and a copying test was conducted in the same manner as in Example 1, sufficient performance could be confirmed. Also, a fixing test with an external fixing device and 50 ° C
There was no problem in the high temperature storage test.

In the durability test by continuous copying, a good image quality was obtained which was the same as the initial one after 50,000 sheets.

Example 4 In Example 1, except that magnetite, which is magnetic powder, was removed from the toner formulation and 8.0 parts of carbon black was added, the same procedure as in Example 1 was repeated except that the average particle size was obtained through the steps of crushing, crushing and classifying. A toner having a diameter of 9.2μ was obtained.

90 parts of carrier iron powder (Nippon Iron Powder, EF
V200 / 300) and supplied to Canon copier NP-6000 for development test. As a result, the initial image and 2
The ten-thousand-sheet durable image was sufficient, and there was no problem in fixing property. In addition, the fixing temperature dependency and the storage test by the different fixing devices shown in Example 1 were also sufficient performance.

Comparative Example 1 A toner was obtained in the same manner as in Example 1 except that only the non-linear polyester of Production Example 5 was used as the polyester. When colloidal silica was added to this toner and a test was conducted in the same manner as in Example 1, sufficient performance was exhibited in initial developability, durability and storability. But in fixing
The fixing point (fixing temperature) tended to be too high.

Comparative Example 2 A mixture of 100 parts of the linear polyester of Production Example 3, 60 parts of magnetic powder and 4 parts of low molecular weight polypropylene was kneaded with a hot roll,
A toner was prepared in the same manner as in Example 1. Colloidal silica was added to the obtained toner, and the toner was subjected to a copy test. When the same test as in Example 1 was conducted, the toner of this example had a remarkable problem particularly in fixing characteristics. That is, a low temperature offset is likely to occur during fixing, the transfer paper tends to be wound around the fixing roll, and the melt viscosity characteristic is clearly poor.

The results of thermal characteristics and durability of the toners of Examples 1 to 4 and Comparative Examples 1 and 2 are shown in the table.

Claims (4)

[Claims] 1. (A) polyoxypropylene-ized, or
A mixture of etherified bisphenol having 50% or more of polyoxypropyleneized and polyoxyethylenated oxypropylene groups, a divalent aromatic carboxylic acid, and a trivalent or more aromatic carboxylic acid, and alkyl substitution 50 to 95% by weight of a non-linear polyester obtained by reacting a dicarboxylic acid, an alkyl-substituted diol or a mixture of an alkyl-substituted dicarboxylic acid and an alkyl-substituted diol,
(B) Linear polyester 50 obtained by reacting polyoxypropylene bisphenol with divalent carboxylic acid
A toner for electrophotography, comprising a mixture containing ˜5% by weight as a binder resin. 2. The electrophotographic toner according to claim 1, wherein the divalent carboxylic acid is fumaric acid. 3. The toner for electrophotography according to claim 1, wherein the binder resin contains a magnetic material. 4. The toner for electrophotography according to claim 3, which contains 30 to 90% by weight of a magnetic material with respect to the binder resin.