JPH079545B2 - Toner for electrophotography - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic method or an electrostatic printing method,
It relates to toners used to develop electrical or magnetic latent images. More specifically, in the heat roll fixing method, fixing is sufficiently performed at a lower temperature, and the offset property is good,
In addition, the present invention relates to a heat-fixing dry toner having excellent fixing properties without causing caking or blocking during development or storage.

Conventionally, as electrophotography, a number of 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.
Generally, a photoconductive substance is used to form an electric latent image on a photoconductor by various means, and then the latent image is developed with a toner, and a toner image is formed on a transfer material such as paper, if necessary. After transfer, the image 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 and the like, a fine powder in which a dye or a pigment is dispersed in a natural or synthetic resin is 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.

The material of the toner is selected to be 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.

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

As described in Japanese Examined Patent Publication No. 51-23,354, such an offset phenomenon, especially a hot offset phenomenon is likely to occur when a low molecular weight resin is used. Therefore, by using a crosslinked resin as described in the publication,
It is thought that the offset phenomenon can be prevented to some extent,
As a matter of course, simply using a cross-linked resin raises the fixing temperature and causes an unfixed portion under normal fixing conditions, causing a problem of low temperature offset in the unfixed portion.

The roller that comes into contact with the toner image usually has at least a surface layer made of silicon rubber or fluorine resin, which has a good releasability, but in order to prevent offset and to prevent fatigue on the roller surface. There is also a method of applying a releasing oil such as silicone oil. However, in the method of applying oil, there are problems that the fixing device is complicated by providing an oil application system and that the user feels uncomfortable due to evaporation of oil. Therefore, it is unfavorable to prevent the offset by applying the oil, and at present, it is desired to develop a toner having a wide fixing temperature range and good offset resistance. As a matter of course, the toner is required to have excellent blocking resistance, developing property, transfer property, cleaning property, etc. in addition to the fixing property. However, the conventional toner has the following defects. Had one or more. That is, most of toners that are easily melted by heating are likely to be caked or aggregated during storage or in a copying machine.
Many toners have poor triboelectric properties and fluidity due to environmental humidity changes. In many toners, the resulting image density changes due to the mutual deterioration of the toner particles, the carrier particles and the photosensitive plate due to the collision between the toner particles and the carrier particles due to the repeated development due to continuous use and the contact between them and the surface of the photosensitive plate. Alternatively, the background density is increased and the quality of the copy is degraded. Therefore, there is a demand for a toner which has various toner properties and is suitable for the heat roller fixing method.

More recently, high-speed fixing has been aimed at in order to improve the efficiency of copying work. For the purpose of increasing the fixing speed in the conventional heat fixing method, attempts have been made to easily perform heat fixing by lowering the softening point of the binder resin of the toner, but if the softening point of the resin is lowered, the toner will be used during use. Problems such as particle agglomeration and blocking occur. Thus, there is a strong demand for a toner that is suitable for higher-speed heat roller fixing, has no roller offset, and has excellent toner properties such as aggregation and blocking.

As a result of various studies on a material having a good high-speed fixing property on a hot roll and an excellent offset resistance, we have found that a polyester resin satisfies such requirements. Further, they have found that among the polyester resins, an amorphous one having a network structure is preferable for the offset resistance. It has been found that controlling the physical properties of this polyester resin can further improve the above-mentioned characteristics, and has reached the present invention.

An object of the present invention is to provide a heat fixing toner that solves the above problems.

It is an object of the present invention to provide a heat roller fixing toner having particularly good fixing property and good offset resistance.
A further object of the present invention is to provide a toner for fixing on a heat roller, which has good loadability, shows stable chargeability at all times during use, and produces a clear and fog-free image.
Another object of the present invention is to provide a toner for fixing on a heat roller, which has excellent fluidity, does not cause aggregation, and has excellent impact resistance. Further, an object of the present invention is to provide a toner for fixing on a heat roller, which has less adhered to the toner holding member or the surface of the photoreceptor. Another object of the present invention is to provide a magnetic toner which, when used as a magnetic developer, exhibits good and uniform magnetism and can be fixed on a heat roller.

Specifically, the present invention relates to an electrophotographic toner containing at least a polyester resin and a colorant, wherein the polyester resin is a polyester resin synthesized from a carboxylic acid and an alcohol component, and the carboxylic acid is trivalent. At least the above aromatic polycarboxylic acids are used, at least etherified bisphenol is used as the alcohol component, and the polyester has the following formula 30,000 ≦ Mw ≦ 110,000 and [In the formula, Mw represents the weight average molecular weight of the polyester resin, and mp represents the melting point of the polyester resin. ] The toner for electrophotography, which has a melting point and a weight average molecular weight satisfying the following conditions.

The melting point and weight average molecular weight of the binder resin in the present invention can be obtained by the following measuring methods.

The melting point of the resin was measured by a METTLER FP61 type fully automatic melting point measuring device. The principle of this device is based on the property that a substance reflects incident light when it is in a solid state and transmits incident light when it is in a molten or softened state. The sample resin was packed in a capillary and attached to a fully automatic melting point measuring device, and the measurement was carried out at a starting temperature of 80 ° C and an upper temperature rate of 1 to 2 ° C / min. In addition,
The melting point in the present invention is defined as the melting point at which the transmittance of incident light becomes 48%. On the other hand, the weight average molecular weight, using Waters ALG / GPC244, detector [RI] 401, column GMH-
6 (manufactured by Toyo Soda). 20 toner samples
The weight average molecular weight was obtained by measuring mg / 4 ml THF under the conditions of a flow rate of 1.2 ml / min, a temperature of 20 to 25 ° C., and a sample injection amount of 200 μ.

In the present invention, the polyester resin used for the toner is measured from the viewpoint of the melting point and the weight average molecular weight, and it is an object of the present invention to obtain a resin satisfying both low temperature fixing property and offset resistance. FIG. 1 shows the condition range in the present invention. In FIG. 1, the polyester resin in the range above the upper limit straight line has poor fixability,
As a toner for a high speed copying machine, a fixing device having a high temperature setting and a wide nip width is required, which is a practical problem. In addition, the polyester resin that falls in the lower part of the lower straight line has many soft components that are easily thermally deformed at low temperatures, and when it is used as a toner, cohesiveness increases, and blocking may occur during storage. become worse.

Further, in the case of a high molecular weight polymer having a weight average molecular weight outside the range of the present invention, the fixability is poor and the pulverizability is practically problematic. On the other hand, a low-molecular weight substance having a lower molecular weight than that of the present invention is difficult to handle during kneading, and easily causes blocking during storage and storage, and also easily causes offset.

From the above, the condition range in the present invention is 30,000 ≦ Mw ≦ 110,000 and More preferably, 40,000 ≤ Mw ≤ 100,000 and As the binder resin to achieve the present invention more preferably,
As a result of investigating various resins, it has been completed by finding a polyester resin, particularly a polyester resin obtained by reacting a polycarboxylic acid with an etherified bisphenol.

The carboxylic acids used in the polyester of the present invention include divalent aromatic carboxylic acids such as phthalic acid, isophthalic acid, phthalic anhydride, terephthalic acid, and their derivatives. Examples include 1,2,4 benzene tricarboxylic acid, 1,2,5-benzene tricarboxylic acid, 1,2,4 naphthalene tricarboxylic acid, 2,
There are 5,7 naphthalenetricarboxylic acid, 1,2,4,5benzenetetracarboxylic acid, and their anhydrides and 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 and itaconic acid. 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 particularly propoxylated and / or ethoxylated. These are bisphenol 1
It has 2 to 3 moles of oxypropylene or oxyethylene per mole. Specific examples include polyoxypropylene 2.2-bis (4-hydroxyphenyl) propane, polyoxypropylene 2.2-bis (4-hydroxy, 2.6-dichlorophenyl) propane, polyoxyethylene (1. 0) -Polyoxypropylene (1.5)
-Bis (4-hydroxyphenyl) propane and the like.

Particularly useful in the present invention are propoxylated bisphenols, which do not contain ethoxylated bisphenols, but are preferred to have a composition in which the molar amount does not exceed the amount of propoxylated bisphenols, and both propoxylated and ethoxylated. In the case of a bisphenol that has been alkoxylated with a species, it is preferred that the amount of ethoxylation does not exceed the amount of propoxylation. That is, in the case of a toner composition using a polyester using an etherified diphenol in which ethoxylated bisphenol accounts for the majority, the characteristics at high humidity are obviously inferior as compared with those using a propoxylated bisphenol. It is presumed that this reflects the difference in hydrophilicity and hygroscopicity of the obtained toner composition. That is, the toner using the etherified bisphenol in excess of ethoxylated bisphenol has a high hygroscopicity under high humidity of the toner, and therefore the triboelectric charging property is lowered, resulting in poor developing performance and consequently a low image density.

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

Other alcohol components, if necessary, within the range of 20 mol% of the total polyol, such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,5
-Pentanediol, 1,6-hexanediol, glycerin, trimethylolethane, trimethylolpropane, pentaerythritol and other aliphatic polyols, 1,4
Aliphatic polyols such as 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.
Is desirable. If the glass transition temperature exceeds 80 ° C, excessive heat energy is required during heat fixing, and the high-speed heat fixing property deteriorates. If the glass transition temperature is less than 50 ° C., the offset resistance during fixing becomes poor. The number average molecular weight is preferably 2000 to 20,000, more preferably 30.
When the molecular weight is less than 2000, the releasing property to the heat fixing roller is deteriorated to cause an offset phenomenon, and when it exceeds 20,000, the heat fixing force is lowered together with the increase of the softening point. The acid value of the polyester used is preferably
It is 10 to 100, more preferably 10 to 60. If the acid value is less than 10, the toner obtained is insufficient in terms of offset during heat fixing, and the releasability from the fixing roller becomes poor. Conversely 10
If it exceeds 0, the obtained toner may have poor fixing property,
Alternatively, it is likely to be affected by humidity and the image under high humidity becomes worse.

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.

The alkyl-substituted dicarboxylic acid has 6 to 18 carbon atoms.
Alkyl-substituted succinic acid, maleic acid, fumaric acid, and acid anhydrides thereof can be mentioned. The higher the carbon number of the alkyl, the more effectively the fixing point can be lowered by adding a small amount, but the action is strong. If it is too much, toner blocking will occur in the 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. They have the same effect as alkyl-substituted dicarboxylic acids.

Examples of the charge control agent used in the toner of the present invention include organic metal compounds which are organic salts or complexes containing divalent or higher valent metals. In particular, a metal complex salt type monoazo dye is used. A metal complex salt type monoazo dye is a complex salt obtained by chemically binding a metal to a monoazo dye molecule, and is a 1: 1 type, 2 dye molecule in which one metal atom is bound to one dye molecule. Bonded one metal atom to
There are 2: 1 type and 3: 1 type complex salts as well, but in the present invention,
The 2: 1 type is particularly preferable, and the metal atom includes Cr, Co, Cu, Fe and the like, and Cr, Co are preferably used.

As commercial products of these metal complex salt type monoazo dyes,
For example, Vali Fast Black + 3804, Bontron S-22, Bontron S-34 manufactured by Orient Chemical Co., Ltd., Spiron Black TRH, BH manufactured by Hodogaya Chemical Co., Ltd., Zapon Fast Red GE manufactured by BASF and the like can be mentioned. The amount added is preferably 0.2 to 10% by weight.

If necessary, a colorant and a fluidity modifier may be added to the toner of the present invention, and the charge control agent and the fluidity modifier may be mixed (externally added) with the toner and used. . Conventionally known dyes and pigments can be used as the colorant, and colloidal silica, fatty acid metal salts and the like can be used as the fluidity modifier.

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. Can be used.

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 to the heat fixing roll more complete.

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

[Polyester Production Example-1] 545 parts of polyoxypropylene (2,5) -2,2-bis (4-hydroxyphenyl) propane were placed in a four-necked flask, and a stirrer, a condenser, a thermometer, and a gas introduction tube were added. 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, the reaction is followed by measuring the acid value every hour to see the end point of the reaction after about 5 hours. The melting point of the obtained resin is 107 ° C, the acid value is 12.0, and the weight average molecular weight is 995.
It was 00.

[Production Example-2 of 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 88 parts of trimellitic acid, and the mixture is heated and stirred at 210 ° C. for reaction, and after completion of the reaction, cooled to room temperature. The obtained resin had a melting point of 106 ° C., an oxidation of 15.0 and a weight average molecular weight of 82800.

[Production Example-3 of Polyester] In the same manner as in Production Example 1, 545 parts of polyoxypropylene (2,5) -2,2-bis (4-hydroxyphenyl) propane was placed in a flask, and the atmosphere was replaced with nitrogen and 50 ° C. Heating. 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. Melting point of the obtained resin
It was 104 ° C., the acid value was 16.0, and the weight average molecular weight was 57,700.

[Production Example-4 of Polyester] Polyoxypropylene (2.2) -2,2-bis (4-
Hydroxyphenyl) propane 226 parts and sorbitol 1
4 parts, 22 parts of ethylene glycol with an alkyl substituent having 8 carbon atoms are placed in a round bottom flask. Next, nitrogen gas was introduced and heated to 50 ° C. while continuing stirring, 104 parts of terephthalic acid / 53 parts of trimellitic acid, 54 parts of malonic acid having an alkyl substituent having 8 carbon atoms were added to the reaction vessel, and 210 ° C.
After reacting for 5 hours, the pressure was gradually reduced and reacted at about 100 mmHg, and when the acid value of the resin reached 25.0, the reaction was terminated. The resin obtained had a melting point of 100 ° C. and a weight average molecular weight of 74,800.

[Comparative Polyester Production Example-1] In Production Example 4, ethylene glycol having an alkyl substituent having 8 carbon atoms and malonic acid were not added and the same was applied except that the reaction time and the reaction temperature were variously changed. The reaction was terminated when the acid value did not decrease and became an acid value of 75.

The obtained resin had a melting point of 142.5 ° C. and a weight average molecular weight of 11,600.

[Comparative Polyester Production Example-2] The same as in Production Example 4 except that the amount of malonic acid having an alkyl substituent having 8 carbon atoms was 81 parts and the ethylene glycol having an alkyl substituent having 8 carbon atoms was 67 parts. The reaction was terminated when the acid value of the resin reached 20. The obtained resin had a melting point of 83 ° C. and a weight average molecular weight of 49,400.

[Examples 1 and 2] The polyester resins of Production Examples 1 and 2 were made into toner by the following method.

Polyester resin 100 parts by weight Magnetite (Fe ₃ O ₄ ) 65 parts by weight Low molecular weight polypropylene 5 parts by weight Metal complex salt type monoazo dye 2 parts by weight (Bontron S-34) The mixture of the above methods is heated and kneaded with a roll, coarsely pulverized and finely pulverized. A finely pulverized product (that is, toner powder) having a uniform particle size distribution with an average particle size of 5 to 20 μm was obtained through the processes of pulverization and classification. To this, 0.3 part by weight of colloidal silica (R-972) was added to obtain a toner. To evaluate the fixability, take out the fixing unit of the NP-400RE copier and replace the heat roller temperature with 10
The nip width is set to 8.5 mm by a separate fixing device that can be controlled from 0 ° C to 250 ° C and the linear velocity can be varied from 100 to 500 mm / sec, and the surface of the heat roller is coated with Teflon. The properties and fixing points were evaluated without applying oil.

The blotting property was evaluated by allowing 20 g of the toner to stand in a constant temperature bath set at 50 ° C. for 24 hours, allowing it to cool at room temperature, and determining the degree of agglomeration.

As a result, the toner of this example had a sufficiently low fixing point (minimum temperature at which fixing is practically sufficient), and no offset development occurred in a wide temperature range. Furthermore, neither blocking nor aggregation occurred during storage. In addition, this toner
Using NP-400RE, continuous printing of 10,000 sheets at room temperature and normal humidity gave clear images without fog until the end.

The Example 3 made of a polyester resin 100 parts Magnetite Preparation 3 (Fe ₃ O ₄₎ 60 parts of polyethylene wa try 3 metal complex type monoazo dye 5 parts (Bontron S-34) the mixture was heated and kneaded with a roll, After cooling down, crushing,
Classification was performed to obtain a finely pulverized product having a size of 5 to 20 μm. When colloidal silica was further added and a copying test was carried out in the same manner as in Examples 1 and 2, it was confirmed that the fixing property was excellent and sufficient performance was obtained without causing offset or blocking. Also NP
Good results were obtained even when images were printed with -400RE.

Example 4 A toner was prepared in the same manner as in Example 1 except that 3 parts by weight of TRHON SPRON BLOCK was used instead of 3 parts by weight of Bontron S-342, and the electrophotographic characteristics were evaluated. The fixing point was sufficiently low and the humidity range was wide. The offset phenomenon did not occur. Furthermore, blocking agglomeration did not occur during storage. When NP-400RE was used to continuously output 10,000 images at room temperature and humidity, clear images were obtained without fog.

Example 5 Polyester resin 100 parts by weight of magnetite in Production Example ₄ (Fe ₃ O 4) 60 parts by weight low molecular weight polyethylene 2 parts by weight of the metal complex type monoazo dye 3 parts by weight (Spiron wander TRH) heat a mixture of the above formulation The mixture was kneaded with a roll, allowed to cool, pulverized, pulverized, and classified to obtain a finely pulverized product having a constant particle size distribution with an average particle size of 10 to 12μ. Colloidal silica 0.
Toner was added by adding 3 parts by weight. Also in this toner, as in Examples 1 to 4, the fixing property was good in electrophotographic characteristics, the toner did not offset in a wide temperature range, and neither blocking nor agglomeration during storage occurred. In addition, a clear image was obtained with NP-400RE when continuously printing 10,000 sheets at room temperature and normal humidity.

[Comparative Example-1] A toner was obtained in the same manner as in Example 5 except that only the resin of Comparative Production Example-1 was used as the polyester resin. Colloidal silk was added to this toner and a test was conducted in the same manner as in Examples 1 to 5 to find that the offset property was good.
Although neither blocking nor agglomeration occurred, the fixability was insufficient. When printing with NP-400RE at 5 ° C and 10% RH, the image after 10 or more sheets should be rubbed lightly by hand. Then, the toner was peeled off from the paper, which was a problem in practical use. Further, when this toner was left in a high humidity atmosphere of 35 ° C. and 85% RH for 24 hours and then subjected to image formation with NP-400RE, the image density was low and image deletion occurred.

[Comparative Example-2] A toner was obtained in the same manner as in Example 5 except that only the resin of Comparative Production Example-2 was used as the polyester resin. When colloidal silica was added to this toner and a test was conducted in the same manner as in Examples 1 to 5, although a fixing point was sufficiently low, an offset appeared and further blocking was performed. In addition, when printing with NP-400RE at room temperature and humidity, 10
The image offset appeared within the number of sheets.

[Brief description of drawings]

FIG. 1 is an explanatory diagram for explaining the relationship between the melting point of the polyester resin and the weight average molecular weight.

Claims (2)

[Claims] 1. An electrophotographic toner containing at least a polyester resin and a colorant, wherein the polyester resin is a polyester resin synthesized from a carboxylic acid and an alcohol component, and 3 as the carboxylic acid.
At least an aromatic polycarboxylic acid having a valency or higher is used,
At least etherified bisphenol is used as the alcohol component, and the polyester has the following formula 30,000 ≦ Mw ≦ 110,000 and [In the formula, Mw represents the weight average molecular weight of the polyester resin, and mp represents the melting point of the polyester resin. ] A toner for electrophotography, having a melting point and a weight average molecular weight satisfying the following conditions. 2. The electrophotographic toner according to claim 1, wherein the trivalent or higher aromatic polycarboxylic acid is trimellitic acid, and the etherified bisphenol is propoxylated bisphenol.