JPH08272141A - Electrophotography toner and production thereof - Google Patents

Abstract

PURPOSE: To perform fixing at a low fixing temperature so as to provide excellent strength for fixing to transfer paper and an excellent image property without any problem in a non-offset property by containing a low melting point resin whose melting starting temperature is within a specific range, specific polyester resin, polyester polyol, and isocyanate. CONSTITUTION: A low melting point resin with a melting starting temperature of 50-100 deg.C a polyester resin containing polyhydric alcohol of trivalent or more as a constituent, polyester polyol obtained from dicarboxylic acid and diol, and isocyanate are contained at least. When a melting starting temperature of the low melting point resin is less than 50 deg.C problems in a preservation property are generated, and when it is 100 deg.C or more, a fixing properly deteriorates. For the low melting point resin, a polyester resin and a styrene group resin are desirable, and a straight chain polyester resin synthesized from thcarboxylic acid and diol is desirable for the polyester resin for setting the melting starting temperature of the low melting point resin to be 50-100 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic toner, and more particularly to an electrophotographic toner for a copying machine or printer which employs heat roll fixing and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, electrophotographic copying machines and printers have been widely used in general households and the like. (Reduction of power consumption), high speed for the purpose of spreading to so-called gray area located at the boundary between printing machine and copying machine, or low roll pressure for simplification of fixing roll to reduce machine cost. Is desired. In addition, copiers equipped with a double-sided copy function and an automatic document feeder have become widespread with the sophistication of copiers, and therefore the electrophotographic toner used in copiers and printers has a low fixing temperature and is durable. There is a demand for a sheet having excellent offset properties and excellent fixing strength on a transfer sheet in order to prevent stains during double-sided copying and stains in the automatic document feeder.

In order to meet the above requirements, the prior art has proposed proposals for improving the molecular weight and molecular weight distribution of the binder resin. Specifically, attempts have been made to lower the fixing temperature by lowering the molecular weight of the binder resin. However, when the molecular weight is lowered, the melting point is lowered, but at the same time, the melt viscosity is also lowered, so that there is a problem that an offset phenomenon occurs on the fixing roll. In order to prevent this offset phenomenon, the molecular weight distribution of the binder resin has conventionally been widened. Specifically, as a method for broadening the molecular weight distribution of the polyester resin, crosslinking has been performed using a polyfunctional monomer having a valence of 3 or more. However, in this method, although the offset phenomenon can be prevented by increasing the crosslink density, there is a problem that the melt viscosity increases and the fixability deteriorates. In addition, in order to have sufficient fixability, the glass transition temperature (T
It was unavoidable that the g) was lowered and the preservability of the toner was impaired. Further, in order to solve this problem, there is a method of widening the entire molecular weight distribution by a method of mixing a high molecular weight polyester resin and a low molecular weight polyester resin at the time of melt-kneading to achieve both offset property and fixability, but this method is extremely difficult. Since the resins having different melt viscosities are kneaded and dispersed, the dispersion of the resins is deteriorated, and sufficient fixability and offset resistance cannot be obtained.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the problems of the above-mentioned conventional toners, and the purpose thereof is to fix at a low fixing temperature, and even in the non-offset property, practically nothing. An object of the present invention is to provide an electrophotographic toner excellent in fixing strength on transfer paper and image characteristics without causing a problem, and a method for producing the same.

[0005]

According to the present invention, a low melting point resin having a melting start temperature of 50 ° C. or higher and 100 ° C. or lower, a polyester resin containing a polyhydric alcohol having a valence of 3 or more as a constituent, a dicarboxylic acid and a diol. A toner for electrophotography, which comprises at least a polyester polyol obtained from the above, and an isocyanate, and a method for producing the same.

The present invention will be described in detail below. The present invention comprises urethanizing a polyester resin containing a polyhydric alcohol component having a valence of 3 or more as a constituent component in the presence of a low melting point resin and a polyester polyol obtained by condensing a dicarboxylic acid and a diol with an isocyanate. The molecular weight distribution of the polyester resin is expanded as compared with the conventional binder resin. The low melting point resin contributes to the fixing strength, and the generated high molecular weight urethane has an elastic action to improve the offset resistance. It is something like. The melting point of the low-melting resin is set to 50 ° C. or higher and 100 ° C. or lower in order to improve the fixability at low temperatures. 50 ° C
If it is less than 100 ° C., there is a problem in storage stability, and if it is higher than 100 ° C., the fixing property is deteriorated.

As the low melting point resin used in the present invention, polyester resin, styrene resin, styrene-acryl copolymer resin, epoxy resin and the like can be used. Above all, it is preferable to use a polyester resin or a styrene resin from the viewpoints of fixability, chargeability, environmental stability and the like. The polyester resin used as the low melting point resin is a linear polyester resin synthesized from dicarboxylic acid and diol, and the melting start temperature of the low melting point resin can achieve the object of the present invention of 50 ° C. or higher 100 It is preferable that the temperature is not higher than ° C.

The dicarboxylic acid component of the low melting point polyester resin includes fumaric acid, maleic acid,
Phthalic acid, isophthalic acid, itaconic acid, glutaconic acid,
Examples thereof include terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, malonic acid, alkenylsuccinic acid, glutaric acid, pimelic acid and suberic acid. Examples of the diol component include polyoxypropylene (2,2) -2,2-bis (4-hydroxyphenyl) propane and polyoxypropylene (3,3)-.
2,2-bis (4-hydroxyphenyl) propane, polyoxyethylene (2,0) 2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (2,2
0) -polyoxyethylene (2,0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (6) -2,2-bis (4-hydroxyphenyl) propane, ethylene glycol, 1, 2-propylene glycol, 1,3-propylene glycol, 1,4
-Butanediol, neopentyl glycol, 1,4-
Butenediol, 1,5-pentanediol, 1,6-
Hexanediol and the like can be mentioned. In the polyester resin used as the low melting point resin of the present invention, it is necessary to minimize the crosslinking reaction due to isocyanate, and therefore, the hydroxyl value is preferably 5 or less. When the hydroxyl value exceeds 5 and is large, a crosslinking reaction proceeds during melt-kneading with an isocyanate and the melting start temperature of the toner rises, which is not preferable. When a styrene resin is used as the low melting point resin, its molecular weight is adjusted so that its melting start temperature falls within the range of 50 ° C. or higher and 100 ° C. or lower, and the molecular weight range is preferably 3000 or higher and 20000 or lower. .

The polyester resin containing the trihydric or higher polyhydric alcohol component as a constituent component of the present invention is
It is obtained by polycondensation of the dicarboxylic acid with a polyhydric alcohol having a valence of 3 or more, or by polycondensation of the dicarboxylic acid with the diol component and a polyhydric alcohol having a valence of 3 or more. Examples of the trihydric or higher polyhydric alcohol include sorbitol, 1,2,3,6-hexanetetrol, 1,
4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-
Butanetriol, 1,2,5-pentanetriol,
Glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane,
1,3,5-trihydroxybenzene etc. are mentioned.
The hydroxyl value of the polyester resin using the polyhydric alcohol component is preferably 5 or more. If the hydroxyl value is less than 5, crosslinking may not be sufficiently carried out and the high temperature offset may be deteriorated. The mixing ratio of the low-melting point resin and the polyester resin containing a polyhydric alcohol having a valence of 3 or more as a constituent component is usually 5 parts by weight to 100 parts by weight of the polyester resin based on 100 parts by weight of the low-melting point resin. To be

The above-mentioned dicarboxylic acid component and diol component can be used in the polyester polyol obtained by condensing the dicarboxylic acid and the diol constituting the present invention. The dicarboxylic acid component is malonic acid, succinic acid, glutaric acid, Aliphatic saturated dicarboxylic acids such as adipic acid, pimelic acid, and suberic acid are preferable because the melt viscosity of the toner after urethanization does not increase so much and the fixing property becomes good. Examples of the diol include ethylene glycol, propylene glycol, trimethylene glycol, 1,4-butanediol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, 1,5-pentanediol, 1 Alkylene glycols such as 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol and 1,10-decanediol do not increase the melt viscosity of the toner after urethanization. It is preferable because the fixing property becomes good. Of these, ethylene glycol and 1,4-butanediol are preferable because they have good storage stability. A specific example of such polyester polyol is ethylene butylene adipate, trade name: Sun Ester No. 22, Sun Esther AH-
401, Sun Esther AH-405, Sun Esther 24
620, a trade name of ethylene adipate: Sun Ester 2620, a trade name of butylene adipate: Sun Ester 4620 (both manufactured by Sanyo Chemical Industry Co., Ltd.) and the like.

The isocyanate applied to the toner for electrophotography of the present invention is added by mixing the raw materials at the time of manufacturing the toner and manufactured by melt-kneading. Therefore, the storage stability of the material is important. Therefore, it is preferable that the isocyanate is blocked with a blocking agent or the one blocked internally so that there is no problem even when it is stored under high temperature and high humidity such as summer or for a long period of time. An example of these blocked isocyanates is isophorone diisocyanate using ε-caprolactam as a blocking agent, trade name: IPDI-
B 1065, IPDI-B 1530, or internally blocked uretdione-bonded blocked isophorone diisocyanate, trade name: IPDI-BF
1540 (both manufactured by HULS (Hills)). In addition, 2,4 tolylene diisocyanate, 2,6
Tolylene diisocyanate, diphenylmethane-4,
Examples include 4'-diisocyanate, hexamethylene diisocyanate, and the like blocked with oxime.
Examples of oximes include formaldehyde oxime, acetaldehyde oxime, methyl ethyl ketoxime, and cyclohexanone oxime. Trade name D as an example of a blocked isocyanate blocked with oxime
M-60 and DM-160 (both manufactured by Meisei Chemical Co., Ltd.) can be mentioned.

The melting start temperature of the electrophotographic toner of the present invention is preferably 60 ° C. or higher and lower than 100 ° C. If the melting start temperature is 100 ° C. or higher, the fixability may not be sufficient, and if it is lower than 60 ° C., the blocking property may be deteriorated and storage stability may be deteriorated. The melting start temperature as used herein refers to the falling start temperature of the plunger based on the following measuring machine and measuring conditions. Measuring instrument: Shimadzu's advanced flow tester CF-500 Measuring condition: Plunger: 1 cm ² Die diameter: 1 mm Die length: 1 mm Load: 20 KgF Preheating temperature: 50-80 ° C Preheating time: 300 sec Temperature rising rate : 6 ° C / min

In the electrophotographic toner of the present invention, in addition to the above components, other binder resins, colorants, charge control agents, and characteristic improvers such as magnetic materials and fluidizing agents can be used. Examples of the binder resin include resins such as silicone resin and polyamide resin. As the colorant, carbon black, nigrosine dye, aniline blue, chalco oil blue, chrome yellow, ultramarine blue, DuPont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, lamp black, rose bengal, and These mixtures, etc. can be mentioned. It is necessary that these colorants be contained in a sufficient concentration to form a visible image, and the amount is usually about 1 to 20 parts by weight with respect to 100 parts by weight of the binder resin. Also,
Examples of the charge control agent include nigrosine dyes, quaternary ammonium salts, monoazo metal complex dyes, triphenyl dyes and the like.

As the magnetic substance, a metal or alloy exhibiting ferromagnetism such as ferrite, magnetite, and other iron, cobalt, nickel, etc., or a compound containing these elements, or a ferromagnetic element not containing any ferromagnetic element is suitable heat treatment. Alloys that exhibit ferromagnetism when subjected to, for example, alloys of the type called Heusler alloys containing manganese and copper, such as manganese-copper-aluminum, manganese-copper-tin, or chromium dioxide, and the like. it can. These magnetic materials are uniformly dispersed in the binder resin in the form of fine powder having an average particle size of 0.1 to 1 micron. The content is 20 to 70% by weight, preferably 40 to 70% by weight, based on the total amount of the toner. If the amount of the magnetic substance is less than 20% by weight, the magnetic force of the toner is insufficient and it is difficult to form a magnetic brush, which may cause a problem in image formation. On the other hand, if it is more than 70% by weight, the magnetic force of the toner is too strong, the image density may be insufficient, and the fixing property may be deteriorated, which is not preferable.

The method for producing the electrophotographic toner of the present invention comprises:
The low melting point resin, a polyester resin containing a polyhydric alcohol having a valence of 3 or more as a constituent, a polyester polyol, an isocyanate and a colorant, and other additives are mixed at a predetermined mixing ratio, and a roll mill, a pressure kneader,
Using a kneading machine such as a Banbury mixer or an extruder, the mixture is hot melt kneaded at a preset temperature of 130 to 200 ° C. higher than the usual kneading temperature, then the kneaded product is cooled, and then finely ground by a jet mill or the like. After that, classification can be performed with a wind force classifier. The electrophotographic toner of the present invention is
A two-component developer is obtained by mixing with a carrier made of ferrite powder, iron powder, or the like. When a magnetic substance is contained, it may be used as it is as a one-component developer for developing an electrostatic image without mixing with a carrier, or may be mixed with a carrier and used as a two-component developer. Further, it can be applied to a non-magnetic one-component developing method.

[0016]

EXAMPLES The present invention will be described below based on examples. In the examples, “part” means “part by weight”. Example 1 <Low-melting point resin> As the low-melting point resin, a polyester resin [trade name: NCP-001 (manufactured by Nippon Carbide Industry Co., Ltd., number average molecular weight 4500, weight average molecular weight 9000, melting start temperature 79.0 ° C.)] was used. . <Synthesis of Polyester Resin Containing Polyhydric Alcohol as Constituent Component> Polyoxyethylene (2,0) 2,2-
35 mol% of diol component consisting of bis (4-hydroxyphenyl) propane, polyoxypropylene (3,3)
Using 65 mol% of a diol component consisting of -2,2-bis (4-hydroxyphenyl) propane, 5 mol% of a tetrahydric alcohol consisting of pentaerythritol, 55 mol% of isophthalic acid and 45 mol% of terephthalic acid as an acid component. Condensation polymerization is carried out to obtain a number average molecular weight of 6000, a weight average molecular weight of 30,000, a hydroxyl value of 30, and a melting start temperature of 101.9.
A polyester resin containing a polyhydric alcohol having a valency of 3 or more at 0 ° C. was obtained. <Toner adjustment> Next, the raw materials having the following compounding ratios are mixed with a super mixer, and the resin temperature is 150 ° C with a twin-screw kneader.
After hot melt kneading, the mixture was pulverized with a jet mill and then classified with a dry airflow classifier to obtain toner particles having an average particle size of 10 μm. Then, 100 parts of the particles and hydrophobic silica (trade name: Cabosil TS-530 manufactured by Cabot Corporation) 0.4
The resulting mixture was stirred for 1 minute in a Henschel mixer, and hydrophobic silica was adhered to the surface of the particles to obtain the electrophotographic toner of the present invention.

Example 2 The low melting point resin of Example 1 was replaced with a styrene-acrylic copolymer resin [manufactured by Nippon Carbide Industry Co., Ltd., trade name: S-100B.
(Number average molecular weight 5500, weight average molecular weight 15,000,
Melting start temperature 90 ° C.)] Example 1 except that 20 parts were changed
An electrophotographic toner of the present invention was obtained in the same manner as.

Example 3 An electrophotographic toner of the present invention was prepared in the same manner as in Example 2 except that the polyester polyol ethylene adipate was replaced by butylene adipate (manufactured by Sanyo Kasei Kogyo Co., Ltd., trade name: Sun Ester 4620). Obtained.

Example 4 In Example 2, ethylene butylene adipate (manufactured by Sanyo Chemical Industry Co., Ltd., trade name: Sun Ester 2462) was used in place of ethylene adipate which is a polyester polyol.
An electrophotographic toner of the present invention was obtained in the same manner except that it was changed to 0).

Example 5 The blocked isophorone diisocyanate of Example 1 was
An electrophotographic toner of the present invention was obtained in the same manner as in Example 1 except that the blocked isocyanate blocked by oxime (trade name: DM-60 manufactured by Meisei Chemical Industry Co., Ltd.) was used.

Comparative Example 1 A polyester resin [trade name: NCP-002 (manufactured by Nippon Carbide Industry Co., Ltd .: number average molecular weight 8500, weight average molecular weight 18000, melting start temperature 102.0 ° C.)] was used in place of the low melting point resin of Example 1. A comparative electrophotographic toner was obtained in the same manner as in Example 1 except that the toner was used.

Comparative Example 2 An electron for comparison was prepared in the same manner as in Example 1 except that the following polyester resin containing no polyhydric alcohol was used in place of the polyester resin containing polyhydric alcohol as a constituent in Example 1. A photographic toner was obtained. The polyester resin means polyoxyethylene (2,0) 2,2-bis (4-hydroxyphenyl) propane 45 mol%, polyoxypropylene (3,3) -2,2-bis (4-hydroxyphenyl) Polyester resin having a number average molecular weight of 8000, a weight average molecular weight of 16000 and a melting start temperature of 107.8 ° C. was obtained by performing condensation polymerization using 55 mol% of propane, 55 mol% of isophthalic acid and 45 mol% of terephthalic acid as acid components.

Comparative Example 3 A comparative electrophotographic toner was obtained in the same manner as in Example 1 except that the blocked isophorone diisocyanate of Example 1 was not used.

Comparative Example 4 A comparative electrophotographic toner was obtained in the same manner as in Example 1 except that the polyester polyol of Example 1 was not used.

Next, the following items were tested for the above-mentioned Examples and Comparative Examples. (1) Non-Offset Temperature Region and Non-Offset Temperature Width First, 4 parts of each electrophotographic toner obtained in the above-mentioned Examples and Comparative Examples and a ferrite carrier not coated with a resin (trade name: FL-1020 manufactured by Powder Tech Co., Ltd.). ) 96 parts were mixed to prepare a two-component developer. Next, a commercially available copying machine (trade name: SF-, manufactured by Sharp Corp.) is used using the developer.
9800), a plurality of belt-shaped unfixed images having a length of 2 cm and a width of 5 cm were formed on an A4 transfer paper. Next, a heat fixing roll having a surface layer made of a fluororesin (trade name: Teflon Co., Ltd.) and a pressure fixing roll having a surface layer made of silicone rubber are paired to rotate a fixing device having a roll pressure of 1K.
The surface temperature of the heat-fixing roll is changed stepwise so that the toner image of the transfer paper having the above-mentioned unfixed image at each surface temperature is adjusted to g / cm ² and roll speed of 50 mm / sec. It was fixed. At this time, it was observed whether or not the toner was smeared in the blank area, and the temperature region where the toner was not smeared was defined as the non-offset temperature region. Further, the difference between the maximum value and the minimum value in the non-offset temperature region was defined as the non-offset temperature width.

(2) Fixing Strength The surface temperature of the heat fixing roll of the fixing device was set to 140 ° C., and the toner image on the transfer paper on which the unfixed image was formed was fixed. Then, the formed fixed image was rubbed with a cotton pad, and the fixing strength was calculated by the following formula to be used as an index of low energy fixing property. As the image density, a reflection densitometer RD-914 manufactured by Macbeth was used. Fixing strength (%) = (image density of fixed image after rubbing / image density of fixed image before rubbing) × 100 (3) Melting start temperature According to the above-mentioned measuring machine and measuring conditions. Table 1 shows the test results of the above items.

[0027]

[Table 1]

As is clear from the test results shown in Table 1, the non-offset temperature range of the electrophotographic toner of the present invention is 80-9.
It was confirmed that a practically sufficient range of 0 ° C. was maintained. Further, the fixing strength at a fixing temperature of 140 ° C. is 9
It was confirmed that the fixing strength was 0% or more, and the fixing strength at a low temperature was practically sufficient. On the other hand, in Comparative Example 1, it was confirmed that the non-offset temperature width was as narrow as 45 ° C. and the fixing strength at 140 ° C. was as low as 70% or less. In Comparative Examples 2 and 4, the non-offset temperature width was as narrow as 20 ° C., and at 140 ° C., offset occurred and the fixing strength could not be measured. In Comparative Example 3, an offset occurred in the entire temperature range, which was a problem in practical use. In addition, using each of the developers described in (1) above, a commercially available copying machine (trade name: BD-3801 manufactured by Toshiba Corp.) was used.
As a result of conducting a continuous copy test up to 000 sheets, in all of Examples 1 to 5, the triboelectric charge amount was from -20 μc / g to -25 μc from the initial stage to 10000 sheets.
It was confirmed that there was no problem in practical use because the image density changes from 1.45 to 1.40 from the initial stage to 10,000 sheets. The copied original is A4 with a black portion of 6%, the triboelectrification amount is measured using a blow-off triboelectrification amount measuring device manufactured by Toshiba Chemical Co., and the image density is a reflection densitometer RD-9 manufactured by Macbeth.
14 was used.

[0029]

The electrophotographic toner of the present invention can maintain a sufficient non-offset temperature range, can be fixed at a low temperature, has excellent fixing strength, and can obtain a sufficient number of image densities. There is an effect that can be.

Claims (7)

[Claims] 1. A low melting point resin having a melting start temperature of 50 ° C. or higher and 100 ° C. or lower, a polyester resin containing a polyhydric alcohol having a valence of 3 or more as a constituent component, a polyester polyol obtained from a dicarboxylic acid and a diol, and an isocyanate. An electrophotographic toner containing at least: 2. The toner for electrophotography according to claim 1, wherein the low melting point resin is a polyester resin synthesized from dicarboxylic acid and diol. 3. The toner for electrophotography according to claim 1, wherein the dicarboxylic acid is an aliphatic saturated dicarboxylic acid. 4. The toner for electrophotography according to claim 1, wherein the diol is alkylene glycol. 5. The toner for electrophotography according to claim 4, wherein the alkylene glycol is at least one of ethylene glycol and 1,4-butanediol. 6. The melting start temperature of the toner is 60 ° C. or higher and 10
The toner for electrophotography according to claim 1, which has a temperature of less than 0 ° C. 7. A low melting point resin having a melting start temperature of 50 ° C. or more and 100 ° C. or less, a polyester resin containing a polyhydric alcohol having a valence of 3 or more as a constituent component, a polyester polyol obtained from a dicarboxylic acid and a diol, and an isocyanate. And at least a colorant are melt-kneaded and then pulverized and classified to obtain a toner for electrophotography.