JP2001166534A - Electrophotographic toner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide excellent electrophotographic toners with which an electrostatic charge quantity may be stably maintained even under the environment having a humidity fluctuation. SOLUTION: A polyester resin of the electrophotographic toners consisting of a master batch composed of at least organic coloring agents and the polyester resin and a binder resin has an acid value of <=3 mgKOH/g.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an excellent electrophotographic toner capable of stably maintaining a charge amount even in an environment where humidity varies.

[0002]

2. Description of the Related Art Many types of latent image forming methods such as electrophotography have been used. In electrophotography, an electric latent image is generally formed on a photoreceptor by various means using a photoconductive substance, and the obtained latent image is formed into an electrophotographic toner (hereinafter, referred to as “toner”). After transferring the toner image to a transfer material such as paper as necessary, heating,
A copy is obtained by fixing a toner image by pressurization and solvent vapor.

[0003] Development methods in electrophotography are broadly classified into a two-component development method using a toner and a carrier such as iron powder and a one-component development method using no carrier. In both development systems, toner particles are charged by friction between the toner particles and a carrier having a different charging sequence or a developing roller, and the latent image on the photoconductor is developed.

Therefore, in development, the charging characteristics of the toner particles are particularly important. As a factor largely affecting the stability of the charge amount, for example, the amount of water contained in the toner particles can be mentioned. In an environment of high humidity, the water content of the toner particles is increased, the resistance of the toner is reduced, and the generated charge is reduced, so that problems such as an increase in image density and fog occur. On the other hand, in an environment of low humidity, the water content of the toner particles decreases, the resistance of the toner increases, the generated charge amount and the counter potential increase, and the development efficiency and image density decrease, and a clear image is reproduced. become unable. Further, an increase or decrease in the charge amount in the one-component developing method also causes a ghost.

Further, the fluctuation of the water content of the toner particles also affects the fluidity of the toner particles, and in the two-component developing system, the stirring and transporting properties between the toner and the carrier fluctuate.
The developing characteristics become unstable, and the formation of a thin toner layer becomes unstable in the one-component developing system.

As a method for suppressing a change in the amount of charge of the toner due to a change in the use environment, for example, Japanese Patent Application Laid-Open No. H11-1909
No. 13 discloses, as a binder resin, 1 to 5 mg KOH /
g of a polyester resin having an acid value of 30 to 80 mgKOH / g and a 30% RH (24%
It is disclosed that the water content of the toner in the time humidity control is suppressed to 5000 ppm or less. According to this method, it is possible to prevent a decrease in the charge amount in a high-humidity environment, but in a low-humidity environment, the charge amount increases, the development amount and the transfer amount decrease, and the image density decreases. descend.

Further, JP-A-8-314180 and JP-A-10-268565 disclose that a wet cake of an organic colorant and the above-mentioned resin are heated and kneaded under reduced pressure to remove residual water and remove the master water. It is described that a batch is created. However, these prior arts do not consider the fluctuation of the water content of the masterbatch and its adverse effects at all.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an excellent toner capable of stably maintaining the charge amount even in an environment having humidity fluctuations.

[0009]

Means for Solving the Problems The present inventors have conducted intensive studies to find an excellent toner capable of stably maintaining the charge amount even in an environment where the humidity varies, and as a result, at least from an organic colorant and a polyester resin. By using a polyester resin having an acid value in a specific range as a resin for the masterbatch in a toner comprising a masterbatch and a binder resin, the charge amount and image density are stabilized, and the development characteristics are improved. Heading, the present invention has been reached.

Thus, according to the present invention, in a master batch composed of at least an organic colorant and a polyester resin and a toner composed of a binder resin, the polyester resin has an acid value of 3 mgKOH / g or less. An electrophotographic toner is provided.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION As the binder resin used in the toner of the present invention, a polyester resin is preferable. The polyester resin can be synthesized from a polyhydric alcohol and a polycarboxylic acid as exemplified below, but is not limited thereto.

Examples of the polyhydric alcohol include 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 2,3-butanediol, diethylene glycol, triethylene glycol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, bisphenol A, hydrogenated bisphenol A, and polyoxyethylenated bisphenol And dihydric alcohols such as bisphenol A alkylene oxide adducts such as A and polyoxypropyleneated bisphenol A (bisphenol A propylene oxide).

In order to make the polymer non-linear to the extent that tetrahydrofuran-insoluble matter is not generated, a trihydric or higher polyhydric alcohol can be used. Glycerin, sorbitol, 1,3
2,3,6-hexanetetraol, 1,4-sorbitan, pentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, 2-methylpropanetriol, 2-methyl-1,2 , 4-butanetriol, trimethylolethane, trimethylolpropane and 1,3,5-trihydroxymethylbenzene.

On the other hand, as the polyvalent carboxylic acid, for example,
Maleic acid, fumaric acid, mesaconic acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, terephthalic acid, isophthalic acid, cyclohexanedicarboxylic acid, malonic acid,
Dibasic carboxylic acids such as succinic acid, adipic acid, sebacic acid, glutaric acid and alkyl succinic acids (eg, n-octylsuccinic acid and n-dodecenylsuccinic acid), trimellitic acid and their anhydrides and alkyl esters. Can be Examples of the combination of the above polyhydric alcohol and polyvalent carboxylic acid include a combination of bisphenol A propylene oxide with terephthalic acid, fumaric acid, trimellitic anhydride or a mixture thereof.

[0015] Since the polyester resin itself has negative chargeability, the polyester resin is generally suitable as a binder resin for negatively chargeable toner. However, a toner using a polyester resin as a binder resin has a drawback that the moisture content is highly dependent on the environment and the charge amount fluctuates greatly in an environment with a fluctuation in humidity. This is presumably because the negative chargeability of the polyester resin is caused by a carboxy group or an ester bond, which is a polar group, and the chargeability of these polar groups is easily affected by a change in humidity.

However, by adopting the constitution of the toner of the present invention, the above-mentioned disadvantages can be avoided even if a polyester resin is used as the binder resin. The polyester resin used as the binder resin preferably has an acid value of 5 to 20 mgKOH / g. When the acid value of the polyester resin is less than 5 mgKOH / g, the negative chargeability of the toner becomes weak, which is not preferable. When the acid value of the polyester resin exceeds 20 mgKOH / g, it is difficult to control the water content of the toner, which is not preferable.

The masterbatch used in the toner of the present invention is prepared by melt-kneading an organic colorant and a polyester resin having an acid value of 3 mg KOH / g or less, and pulverizing the mixture. There is also a method in which the wet cake of the agent and the above-mentioned resin are heated and kneaded under reduced pressure to remove residual moisture, thereby preparing the wet cake.

As a resin for the master batch, 3 mgK
By using a polyester resin having an acid value of OH / g or less, fluctuations in the water content of the toner due to fluctuations in humidity can be reduced, and fluctuations in the charge amount of the toner can be reduced. This is because the change in moisture content due to humidity change is small.
Since the polyester resin having an acid value of not more than mgKOH / g is uniformly dispersed at a high concentration around the organic colorant having a large variation in water content, the variation in the moisture content of the entire toner is reduced. Conceivable.

The organic colorant constituting the master batch includes a yellow (Y) colorant, a magenta (M) colorant, a cyan (C) colorant, and a black colorant. These organic colorants are used in combination as appropriate.

As the colorant for the yellow (Y) toner, for example, C.I. I. Pigment Yellow 1, C.I. I. Pigment Yellow 5, C.I. I. Pigment Yellow 12, C.I. I.
Pigment Yellow 15, C.I. I. Azo pigments such as CI Pigment Yellow 17; Examples of the dye include C.I. I. Nitro dyes such as Acid Yellow 1; I. Solvent Yellow 2, C.I. I. Solvent Yellow 6, C.I. I. Solvent Yellow 1
4, C.I. I. Solvent Yellow 15, C.I. I. Solvent Yellow 19, C.I. I. Solvent Yellow 21
And other oil-soluble dyes. Among them, C.I. I. Benzidine pigments such as CI Pigment Yellow 17 are preferred in terms of color as a yellow colorant. In addition, inorganic pigments such as yellow iron oxide and loess can be used as the auxiliary colorant.

Examples of the colorant for the magenta (M) toner include C.I. I. Pigment Red 49, C.I. I.
Pigment Red 57, C.I. I. Pigment Red 8
1, C.I. I. Pigment Red 122, C.I. I. Solvent Red 19, C.I. I. Solvent Red 49, C.I.
I. Solvent Red 52, C.I. I. Basic Red 10, C.I. I. Disperse Red 15 and the like. Among them, C.I. I. A quinacridone-based pigment such as Pigment Red 122 is preferred in terms of the color as a magenta-based colorant.

As a colorant for cyan (C) toner,
For example, C.I. I. Pigment Blue 15, C.I. I. Pigment Blue 16, C.I. I. Solvent blue 55,
C. I. Solvent Blue 70, C.I. I. Direct Blue 25, C.I. I. Direct Blue 86 and the like. Among them, C.I. I. Pigment Blue 15 and other copper phthalocyanine pigments are preferred in terms of color as a cyan-based colorant.

As the black coloring agent, carbon black is preferably used. On the other hand, examples of the polyester resin used for preparing a masterbatch together with the coloring agent as described above include those exemplified as the binder resin and having an acid value of 3 mgKOH / g or less.

The weight ratio of the polyester resin contained in the master batch is desirably 40% by weight or more. If the weight ratio of the polyester resin is less than 40%, the effect of suppressing an increase in the water content of the toner cannot be expected, which is not preferable. The organic colorant is used in an amount of 1 to 30 parts by weight, preferably 2 to 20 parts by weight, based on 100 parts by weight of the melt-kneaded polyester resin.

The toner of the present invention may contain additives such as a charge control agent (charge control agent) usually used in this field, in addition to the binder resin and the masterbatch. Further, an external additive may be further added to the toner in which such an additive is added.

The charge control agent is blended for the purpose of controlling the triboelectric charging property of the toner. Specific examples include oil-soluble dyes such as oil black and spiron black, metal-containing azo dyes, metal salts of naphthenic acids, metal salts of alkyl salicylic acids, fatty acid soaps and resin acid soaps. When the charge control agent is added, the amount added is as follows.
The amount is 0.1 to 10 parts by weight, preferably 0.5 to 8 parts by weight based on 00 parts by weight. In the case of a color toner, a colorless metal salt of alkyl salicylic acid (for example, a zinc compound) is preferable as the charge control agent.

Examples of the external additive include aluminum oxide powder, titanium oxide powder, and fine powder silica, and hydrophobic inorganic fine particles obtained by subjecting these to hydrophobic treatment are preferred. By externally adding the hydrophobic inorganic fine particles to the toner, that is, by subjecting the toner to the surface treatment with the hydrophobic inorganic fine particles, it is possible to suppress the fluctuation of the fluidity of the toner caused by the increase or decrease of the water on the toner surface due to the fluctuation of the humidity. Agitation with carrier,
The transportability and the chargeability can be stabilized. The surface treatment with the hydrophobic inorganic fine particles can be performed by a known method.

Further, other external additives may be used in combination. Examples of such external additives include vinylidene fluoride fine powder, polytetrafluoroethylene fine powder, fatty acid metal salt, zinc stearate and calcium stearate. And the like.

The toner of the present invention can be obtained by simply mixing the above-mentioned binder resin with the masterbatch and optionally added additives, and the mixture is further melt-kneaded and pulverized as follows. Is preferred. That is, the binder resin, the masterbatch and optionally added additives are homogeneously premixed by a known blending device such as a dry blender, a super mixer and a ball mill, and the resulting mixture is subjected to a Banbury mixer, a roll, a single screw extruder. Or melt-kneaded uniformly with a known kneading device such as a twin-screw extruder, cooled the obtained kneaded material and pulverized with a known pulverizer such as a cutting mill, and if necessary, such as an ultrasonic jet mill. It can be manufactured by finely pulverizing with a pulverizer and classifying the obtained pulverized product with a known classifier. Further, if necessary, an external additive is added to the obtained toner by using a known mixing device such as a super mixer and a ball mill.

In the toner thus obtained, a change in the water content of the toner due to a change in humidity is small, and the charge amount is stably maintained. Above all, it has a water content of 0.3% by weight or more in an environment of an absolute humidity of 10 g / m ³ and a water content of 0.6% by weight or less in an environment of an absolute humidity of 35 g / m ^{3 by} the Karl Fischer method. Are particularly preferred.

When the water content of the toner is 0.3% by weight or more in an environment with an absolute humidity of 10 g / m ³ , a decrease in development efficiency and image density that occurs in an environment with a low humidity is suppressed, and the toner is sharper. Image can be obtained. When the water content of the toner is 0.6% by weight or less in an environment with an absolute humidity of 35 g / m ³ , an increase in image density and fogging generated in an environment with a high humidity are suppressed, and a clearer image is formed. Can be obtained.

The toner of the present invention preferably has an average particle size of 5 to 10 μm. Average particle size of toner is 5μ
When the value is less than m, the balance between the chargeability of the toner and the powder characteristics deteriorates, such being undesirable. If the average particle diameter of the toner exceeds 10 μm, high quality image formation cannot be expected, which is not preferable.

When the toner of the present invention is used as a developer of a one-component developing system, the toner of the present invention can be used as it is. When the toner of the present invention is used as a developer of a two-component developing system, The toner of the present invention is mixed with a known carrier.

[0034]

EXAMPLES The present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited by these Examples.

(Examples 1 and 2 and Comparative Examples 1 and 2) After the following materials were uniformly mixed with a super mixer, the resulting mixture was melt-kneaded with a twin-screw extruder and cooled. -100 parts by weight of binder resin [polyester resin (bisphenol A propylene oxide, terephthalic acid and fumaric acid), acid value of 16.6 mgKOH / g]-Melting master batch [quinacridone pigment and polyester resin ^* (weight ratio 4: 6) Kneaded and pulverized] 12 parts by weight

* In each of Examples and Comparative Examples, bisphenol A propylene oxide and the following polycarboxylic acids were used as raw materials for the polyester resin. Example 1: Terephthalic acid and fumaric acid Example 2: Terephthalic acid and fumaric acid Comparative example 1: Terephthalic acid and fumaric acid Charge control agent (zinc compound of salicylic acid) 2.0 weight Department

The obtained kneaded material was roughly pulverized by a cutting mill, finely pulverized by an ultrasonic jet mill, and fine powder having a particle size of 5 μm or less was removed by a classifier to obtain a classified toner. The particle size of the classified toner was distributed in the range of 5 to 16 μm, and the average particle size was 8.0 μm. Examples 1 and 2 and Comparative Example 1
Table 1 shows the acid value (mg KOH / g) of the polyester resin (batch resin) used in the master batch and the water content of the obtained classified toner.

The water content was measured using a Karl Fischer titrator (manufactured by Mitsubishi Chemical Corporation, KF-06). At the time of measurement, a sample was previously placed in a measurement environment (absolute humidity 10 g /
m ³ and 35 g / m ³ ) for 15 hours. The measurement was performed at a sample amount of 120 to 170 mg and a heating furnace temperature of 170 ° C.

[0039]

[Table 1]

Next, 0.4% by weight of hydrophobic silica was added as an external additive to the obtained classified toner, and this was mixed with a super mixer to obtain an externally added toner. Further, ferrite particles as a carrier were mixed with the obtained externally added toner so that the toner concentration became 4.0% by weight, to obtain a developer.

The developer was evaluated using an electrophotographic apparatus having an OPC photosensitive drum. That is, each of the obtained developers is set in an electrophotographic apparatus, and is placed under low temperature and low humidity (10 ° C., 4
0% RH) and high temperature and high humidity (35 ° C., 80% RH) for 15 hours, a running test was performed on about 10,000 sheets, and the image density, fog and the amount of toner charge on the sleeve were measured. . The charge amount was measured using a blow-off charge amount measuring device (manufactured by Toshiba), and the image density was measured using a Macbeth reflection densitometer. Table 2 shows the obtained results.

[0042]

[Table 2]

Comprehensive evaluation was made from the appropriate ranges of image density and fog (density) shown in Table 2, and those which were suitable as a developer were evaluated as "O" and those which were unsuitable as "X". With the developers obtained in Examples 1 and 2, good results were obtained with respect to image density and fog. On the other hand, in the developers obtained in Comparative Examples 1 and 2, the charge amount is reduced particularly under high humidity and high humidity,
An increase in image density and fogging occurred.

(Examples 3 to 6 and Comparative Examples 3 to 6) Example 1 was repeated except that a polyester resin having the properties shown in Table 3 was used as a binder resin and that of Example 2 was used as a masterbatch. (Example 3)
To 6 and Comparative Examples 3 to 5). Table 3 shows the water content of the obtained classified toner.

[0045]

[Table 3]

A developer was obtained in the same manner as in Example 5 except that untreated silica was used instead of the hydrophobized silica as an external additive in the classified toner (Comparative Example 6). Each of the obtained developers was evaluated in the same manner as in Example 1. Table 4 shows the obtained results.

[0047]

[Table 4]

With the developers obtained in Examples 3 to 6, good results were obtained with respect to image density and fog. On the other hand, in the developer obtained in Comparative Example 3, the charge amount increased under low temperature and low humidity, and the image density decreased. In the developer obtained in Comparative Example 4, the charge amount decreased and fog occurred. . Also,
In the developer obtained in Comparative Example 5, the charge amount decreased particularly under high temperature and high humidity, and the image density increased and fog occurred. Furthermore, in the developer obtained in Comparative Example 6, the agitation was reduced due to a decrease in fluidity under high temperature and high humidity, and an increase in image density and fog occurred.

Example 7 and Comparative Example 7 A developer was obtained in the same manner as in Example 6 except that the ratio of the polyester resin in the master batch was 45% by weight (Example 7). Moreover, except that the ratio of the polyester resin in the master batch was set to 37% by weight, in the same manner as in Example 2,
A developer was obtained (Comparative Example 7). About the obtained developer,
Evaluation was performed in the same manner as in Example 1. Table 5 shows the obtained results.

[0050]

[Table 5]

With the developer obtained in Example 7, good results were obtained with respect to image density and fog. On the other hand, in the developer obtained in Comparative Example 7, the charge amount decreased particularly under high humidity and high humidity, and the image density increased and fog occurred.

[0052]

The toner of the present invention is characterized in that, in a toner comprising a masterbatch comprising at least an organic colorant and a polyester resin and a binder resin, the polyester resin has an acid value of 3 mg KOH / g or less. . Therefore, it is possible to provide an excellent toner capable of stably maintaining the charge amount even in an environment where the humidity varies.

Further, the toner of the present invention is
Absolute humidity of 10 g / m ^Three0.3 in the environment
Has a moisture content of at least 35% by weight and an absolute humidity of 35 g / m^Three
It has a water content of 0.6% by weight or less in an environment of
Sign. Therefore, development that occurs in a low humidity environment
Efficiency and image density are prevented from lowering, and in high humidity environments
Suppresses the increase in image density and fog that occur, resulting in clearer images
Image can be obtained.

Continued on the front page (72) Inventor Satoshi Ogawa 22-22 Nagaikecho, Abeno-ku, Osaka City, Osaka F-term (reference) 2H005 AA01 AA08 AA21 AB02 CA08 CA12 CA21 CA26 CB13 EA05 EA07 EA10

Claims (6)

[Claims] 1. An electrophotographic toner comprising a masterbatch comprising at least an organic colorant and a polyester resin and a binder resin, wherein the polyester resin is contained in an amount of 3 mg.
An electrophotographic toner having an acid value of KOH / g or less. 2. The electrophotographic toner according to claim 1, wherein the binder resin is a polyester resin having an acid value of 5 to 20 mgKOH / g. 3. The electrophotographic toner according to claim 1, wherein the master batch contains at least 40% by weight of a polyester resin. 4. The toner for electrophotography according to the Karl Fischer method has a water content of 0.3% by weight or more in an environment with an absolute humidity of 10 g / m ³ and a water content of 0.3% in an environment with an absolute humidity of 35 g / m ³ . 4. The composition according to claim 1, which has a water content of 6% by weight or less.
The toner for electrophotography according to any one of the above. 5. The electrophotographic toner according to claim 1, wherein the electrophotographic toner is surface-treated with hydrophobic inorganic fine particles. 6. The electrophotographic toner according to claim 1, wherein the electrophotographic toner has an average particle size of 5 to 10 μm.