JPS6349768A - Electrophotographic toner composition - Google Patents

Abstract

PURPOSE:To enhance fixability, spreadability, and offset resistance of a toner by using the toner composed essentially of a specified linear polyurethane- modified polyester. CONSTITUTION:The toner composition is composed essentially of the linear polyurethane-modified polyester (C) obtained by reacting the linear polyester (A) with diisocyanate (B), and it has a glass transition point of 40-80 deg.C and an acid value of <=5. The polyester to be used as said component A is the polycondensation product of dicarboxylic acid, such as isophthalic acid, and diol, such as diethylene glycol, and it has a number average molecular weight of 1,000-20,000, and an acid value of <=5, and substantially it has hydroxyl groups on the terminal. The component (C) is obtained by reacting 0.3-0.95mol of the component (B), such as diphenylmethane-4,4'-diisocyanate, with 1mol of the component (A).

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an electrophotographic toner composition.

(Prior Art) In recent years, in electrophotography, as the number of reproductions has increased and diversified, the development of full-color electrophotography has become an important issue in response to the colorization of original documents.

Furthermore, for the purpose of improving the efficiency of copying work, achieving high-speed copying is an important issue.

The establishment of full-color electrophotography and the achievement of high-speed copying are in no small part due to the design of copying machines, including the copy A mechanism, but this alone does not solve the problem. Much depends.

However, the current situation is that conventional toners are not necessarily satisfactory for high-speed full-color electrophotography.

The reason for this is that full-color electrophotography is, for example, 3! ~5B (1986), it is basically based on color mixing by overlapping monochrome colors, which can be said to be an extension of monochromatic colors. The rougher the mixed color, the thicker the toner layer becomes, and in the fixed image, the thickness of the toner layer changes greatly depending on the color and shade, making it difficult to obtain a smooth image with good color reproducibility. There are things that cannot be done.

Although such problems largely depend on the heat fixing characteristics of the toner used, they cannot be solved only by the conventionally discussed concepts of minimum fixing temperature, fixing strength, etc.

In other words, in order to obtain a smooth, full-color image with good color reproducibility, it is essential that the toner has good spreadability during heat fixing and good penetration into the copying paper. The main reason for this is that this cannot be achieved with toners whose main component is a binder mainly composed of polyester having a partially crosslinked structure.

As a means to solve this problem, if you try to obtain a toner with high spreadability by using a binder with a low molecular weight and a low softening point, such as a styrene binder with a low molecular weight and a low softening point, or a polyester with a relatively low molecular weight, it is possible to obtain a toner with high spreadability. In addition, at high fixing temperatures at which good smoothness and color reproducibility are obtained, offset resistance is markedly reduced and image distortion occurs, which is a major problem in practical use. There's a problem.

In addition, partially cross-linked polyester-based binders have a wide fixable temperature range and are suitable materials for high-speed copying, but gelation in the binder resin is a problem! 71! The structured portion exhibits so-called rubber-elastic behavior, has extremely poor spreadability and paper penetration during heat fixing, and the resulting image is poor in smoothness. Toner containing a polyester resin binder has a high concentration of terminal carboxyl groups, so it has poor moisture resistance.
The influence of moisture at high temperatures causes a decrease in the charge amount of the toner and a decrease in image quality, which poses a practical problem.

(Problems to be Solved by the Invention) The present invention has been made in order to provide a heat fixable toner that solves the above-mentioned problems.

An object of the present invention is to provide a heat fixing toner that has good fixing properties, good toner spreadability, smooth images after fixing, and good offset resistance.

Furthermore, it is an object of the present invention to meet the various performances required of toners in practice, namely, excellent storage stability, excellent PVC plasticity resistance,
Furthermore, the present invention provides a heat fixing toner that satisfies the fact that stable images can be obtained even during long-term continuous use and under high temperature and high humidity conditions.

That is, considering the class II, skeleton and molecular weight range, thermal properties, mechanical properties, etc. of the binder resin used,
The present invention has realized a toner that is practically suitable not only as a normal monochromatic toner but also as a full-color toner, and also has performance such as high-speed copying properties.

(Means for Solving the Problems) As a result of intensive studies to achieve these problems, the present inventors discovered that a linear polyester resin (A) obtained by reacting a diisocyanate (B) with The toner whose main component is urethane-modified polyester resin (C) has good fixing properties, and the toner spreadability during fixing is good, resulting in smooth images with good color reproducibility, and offset resistance. At the same time, we found that toners containing this resin as a main component have good storage stability and resistance to PVC plasticizers, and furthermore, image stability during long-term continuous use and image quality at high temperatures are also good. They found this and completed the present invention.

That is, the present invention is directed to a linear polyester resin (A
) A linear urethane-modified polyester resin (C) obtained by reacting 0.3 to 0.95 mol of diisocyanate (B) per mol, and the glass transition temperature of the resin (C) is 40 to 80°C. The present invention relates to an electrophotographic toner composition characterized by containing as a main component an acid value of 5 or less.

The linear polyester resin (8) referred to in the present invention is one obtained by polycondensation of a divalent carboxylic acid and a diol. The dicarboxylic acids mentioned here include, for example, aliphatic dibasic acids such as malonic acid, succinic acid, azelaic acid, sebacic acid, and hexavitrophthalic anhydride; maleic acid, maleic anhydride, fumaric acid, itaconic acid, and citraconic acid; Examples include aliphatic unsaturated dibasic acids, aromatic dibasic acids such as phthalic anhydride, phthalic acid, terephthalic acid, and isophthalic acid, and lower alkyl esters and acid halides thereof.

In addition, the diols mentioned here include, for example, ethylene glycol, 1,2-propylene glycol, 1,3-
Propylene glycol, 1,2-butanediol, 1,
3-butanediol, 1.4-butanediol, 1.6
-hexanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, cyclohexane dimetatool, hydrogenated bisphenol A1 bisphenol A ethylene oxide adduct, bisphenol A propylene oxide adduct, polyethylene glycol,
Examples include polypropylene glycol and polytetramethylene glycol.

As the polycondensation method, commonly known high temperature polycondensation, solution Mwi synthesis, interfacial polycondensation, etc. are used.

The ratio of dicarboxylic acid and diol used is usually 0.8-1.
4 is devastating.

Further, the molecular weight of the polyester resin (A) is preferably 1000 to 20000 in number average molecular weight, particularly preferably 2000 to 1000o. If the number average molecular weight of (A) is less than 1,000, the offset resistance of the urethane-modified resin (C) will decrease, which is undesirable, and if it exceeds 20,000, the fixing properties of the urethane-modified resin (C) and the smoothness of the resulting image will decrease. I don't like it.

Further, as the diisocyanate (B) according to the present invention, for example, hexamethylene diisocyanate (IiDI), isophorone diisocyanate (IPDI), tolylene diisocyanate (TDI), diphenylmethane-4,4
Examples include °-diisocyanate-1-(MDI), xylylene diisocyanate (XDI), and tetramethylxylylene diisocyanate (TMXDI).

The diisocyanate (B) is usually used in an amount of 0.3 to 0.95 mol per mol of the polyester resin (A), particularly preferably 0.5 to 0.9 mol. If the amount of diisocyanate (B) is less than 0.3 mol, offset resistance and vinyl chloride plasticizer resistance will deteriorate, which is undesirable, and if it exceeds 0.95 mol, the smoothness of the image obtained by fixing will deteriorate, which is undesirable.

Further, the glass transition temperature of the linear urethane-modified polyester resin (C) is preferably 40 to 80°C, especially 50°C.
The temperature is preferably 70°C. Glass transition temperature is 40℃
If it is less than 8, the blocking resistance decreases, which is undesirable.
If it exceeds 0°C, the minimum fixing temperature will be high and image smoothness will deteriorate, which is not preferable.

Furthermore, the acid value of the linear urethane-modified polyester resin (C) is preferably 5 or less; if it exceeds 5, the charge amount of the toner will be greatly reduced during development at high temperatures.
This is not preferable because the background density reaches an upper limit and a clear image cannot be obtained.

In addition, in the case of a urethane crosslinked polyester resin obtained using a component such as a trivalent carboxylic acid or a triol as a polyester resin, the fixable temperature range is slightly lower than that in the case of using the linear urethane modified polyester resin (C) of the present invention. Although the fixing temperature was high and the range was narrow, there were no major problems in this regard, but the images obtained by fixing generally lacked smoothness, and the spreadability of the toner was such that it could not be used for overlapping copying. It was poor quality.

A similar phenomenon is observed in urethane crosslinked polyester resins obtained by reacting linear polyester resins (A) with polyfunctional isocyanates; in both cases, the inclusion of a gel structure in the binder resin provides good spreadability and image quality. This is thought to be the reason why smoothness cannot be achieved.

Regarding branched urethane-modified polyesters that do not have a gel structure and are obtained by using a very small amount of polyhydric carboxylic acid, polyhydric alcohol, or polyfunctional isocyanate, the smoothness of the image is insufficient, although to a lesser extent, and the present invention cannot be used. It was not possible to fully achieve the objective.

The linear urethane-modified polyester resin (C) can be obtained, for example, by the following method. That is, into a linear polyester resin (A) alone, preferably into a solution containing the linear polyester resin (A), diisocyanate (B) is added all at once or in portions at a temperature of 50 to 120°C, and the reaction is allowed to proceed for several hours. Subsequently, when the reaction is completed, it may be treated under high temperature and high vacuum to remove unnecessary solvents, moisture, residual odors, etc. due to heat-degraded products, etc. Here, the linear polyester resin (A) alone is diisocyanate) (B
) is not advantageous because it is difficult to control the reaction and the state of the resulting urethane-modified resin (C) is stable and uniform.

The most common method for obtaining the electrophotographic toner composition of the present invention includes, for example, pulverizing the linear urethane-modified polyester resin (C) to a particle size of 0.5 to 5 mm;
Optional coloring agents, and if necessary, acrylic resins, styrene resins, epoxy resins, maleated rosins, petroleum resins, coloring agents, and small amounts of vI electrostatic agents and waxes may be added to an extent that does not reduce the effect of the present invention. After mixing with a Henschel mixer etc., the temperature is 100-150℃ with a kneader etc.
The lump obtained by melt-kneading is crushed and classified to have a particle size of 5 to 20.
Examples include a method of obtaining micrometer particles.

The electrophotographic toner composition thus obtained provides a clear image with low heat and high speed copying, has sufficient image smoothness even when multilayered and copied, and can withstand long-term use and high temperatures. It can maintain good image quality even when copying at high humidity, and has excellent toner storage stability, impact resistance, and powder fluidity, making it extremely suitable for full-color and single-color high-speed copying.

(Example) Next, the linear urethane-modified polyester resin (C) of the present invention
The present invention will be specifically explained with reference to production examples, examples and comparative examples.

In addition, hereinafter, "parts" represent parts by weight unless otherwise specified.

Production Example ■ ~ XrV 5640 flask equipped with a reflux condenser, water separator, nitrogen gas inlet tube, thermometer, and stirring I! The dicarboxylic acids and diols shown in Table 1 were charged, nitrogen was introduced into the flask, and dehydration polycondensation was carried out at an internal temperature of 240°C.
A polyester resin (A) having the properties shown in was obtained. Thereafter, the internal temperature was cooled to 140° C., and then xylene in the weight parts shown in Table 1 was added to obtain a xylene solution of polyester resin (A).

Solid content of this polyester resin (A) in xylene solution is 100! To the if part, diisocyanate in the weight parts shown in Table 1 was added and reacted for 4 hours. After confirming that the solution viscosity did not change over time, the flask was equipped with a vacuum desolvation device and heated at high temperature. Xylene was distilled off under reduced pressure to obtain urethane-modified polyester resins ① to X[V having the properties shown in Table 1.

Comparative Production Example 1=vi After polycondensing the dicarboxylic acid and diol shown in Table 2 in the same manner as in Production Examples ① to XrV, a urethane-modified polyester having the properties shown in the table was prepared using the diisocyanate shown in Table 2. Resin 1xvii was obtained.

Comparative Production Example ix % The polyvalent isocyanate shown in Table 3 was mixed with a Henschel mixer under a stream of dry nitrogen, and the resulting mixture was immediately melt-kneaded at 180°C using a twin-screw kneader to obtain the properties shown in Table 3. The urethane crosslinked polyester resin i had ~xiv.

Examples and Comparative Examples After pulverizing the solid resins obtained in Production Example 1-XrV and Comparative Production Examples 1 to xiv, they were mixed with a colorant in a Henschel mixer at the ratios shown in Tables 4 and 5, and then subjected to twin-screw extrusion. After kneading in a machine at 150° C. for 30 minutes, the mixture was coarsely pulverized in a cutter mill to obtain coarse toner particles having a particle size of about 0.8a+II+.

The coarse particles are finely pulverized with a jet pulverizer, and then classified with an air classifier to have a particle size of 5 to 20 μm (approximately 10 μm particles with an average particle size of 5 μm or less, including 1% by weight of 5 μm or less, and 2% by weight of 20 μm or more. ) toner particles were obtained.

The storage stability of this toner particle is shown in Tables 4 and 5.

Next, 5 parts by weight of these toner particles and ferrite carrier (1 part by weight)
45-350 mesh, Nippon Iron Powder F-150) 95
parts by weight were mixed to prepare a developer.

Using a magnetic brush copier equipped with an OPC photoreceptor,
Table 4 shows the results of examining the fixing properties, offset properties, image characteristics, image smoothness when overlapping copies, and image characteristics at high temperatures of this toner. , and are shown in Table 5.

Notes in the above table are as follows.

Note 1) Bisphenol A propylene oxide adduct,
Made by Mitsui Toatsu Kagaku@2) Diethylene glycol 3) Ratio of the molar equivalent of hydroxyl group to the molar equivalent of carboxy group in the raw material 4) According to JIS K-5400 5) Number average molecular weight (value calculated by GPC using standard polystyrene as a standard) 6 ) diphenylmethane-4,4°-diisocyanate 7
) Ratio of the number of moles of diisocyanate (B) to the number of moles of polyester resin (A) calculated from the number average molecular weight 8) Weight average molecular weight (calculated by GPC using standard polystyrene as a standard) 9) Glass transition temperature (DSC) 10) Additive of 3 moles of tolylene diisocyanate to 1 mole of glycerin (manufactured by Mitsubishi Chemical Industries, Ltd.) 11) M8-100 (manufactured by Mitsubishi Chemical Industries, Ltd.)
12) C, 1, Solvent Red 83 (manufactured by Udugaya Kagaku wo Co., Ltd.) 13) C, 1, Solvent Blank 7 (manufactured by Orient Kagaku 91) 14) State of agglomeration of toner particles after being left at 50°C for 24 hours was determined as follows.

◎C Not aggregated at all.

○: Slightly agglomerated, but easily loosened by gently shaking the container, causing no practical problems.

Δ: Some aggregates that do not separate are present.

×; Completely baby booming.

15) The minimum fixing roll surface temperature required to show that the M1% of the toner remaining attached after performing a friction test on the black part of the IQIXIQ1 corner using a Taber-Fj friction tester is 90% or more.

16) The lowest surface temperature of the fixing roll at which the so-called offset phenomenon, in which molten toner adheres to the fixing roll and is fixed onto the copy paper again, begins to occur.

17) The amount of toner adhering to the white background of the bank ground was visually determined.

18) The degree of blackness of the solid black part was visually determined.

19) When the same image was duplicated 1 to 4 times, the degree of difference in the toner layer thickness that changed stepwise was visually determined.

◎: Very good smoothness.

○: Good smoothness.

△: Smoothness is such that there are no problems for actual river use.

×: Absolutely poor smoothness.

20) The image after 50,000 consecutive copies was compared with the 50th image to visually determine image defects.

21) After being left at 30° C. and 85% relative humidity for 72 hours, a copying test was conducted in the same manner as in Note 17).

22) A test similar to Note 18) was conducted under the same conditions as Note 21).

23) PVC film was superimposed on the solid black part of 5 cm x 5 cI11, and after being left at 50° C. for 24 hours under a load of 50 g/cd, the film was released from HA at room temperature.

At this time, the state of transfer of the toner to the PVC film was visually determined.

◎: No migration of dye or toner was observed.

○: Only the dye has migrated.

△: The toner portion has migrated.

×: Most of the toner has migrated.

(Effects of the Invention) According to the method of the present invention, the fixing property that could not be achieved with the conventional technology is good, and the spreadability of the toner during fixing is also good, and the obtained image is smooth and has good offset resistance and storage stability. The present invention has been achieved to a practically satisfactory degree for an electrophotographic toner composition that has excellent properties and resistance to vinyl chloride plasticizers, and is capable of providing stable images even during long-term continuous use and under high temperature and high humidity conditions.

This has been a long-standing problem with conventional technology, but it is made of dicarboxylic acids and diols and has a number average molecular weight of 1000 to 1000.
20,000 and an acid value of 5 or less and whose terminal groups are essentially hydroxyl groups (A) per mole of 0.
A linear urethane-modified polyester resin (c) obtained by reacting 3 to 0.95 mol of diisocyanate (B), and the glass transition temperature of the resin (c) is 40 to 80 ° C.
This was achieved by employing an electrophotographic toner composition characterized by having an acid value of 5 or less as a main component.

Claims (1)

[Claims] Composed of dicarboxylic acid and diol, number average molecular weight is 10
00 to 20,000, obtained by reacting 0.3 to 0.95 mol of diisocyanate (B) per 1 mol of linear polyester resin (A), which has an acid value of 5 or less and whose terminal groups are essentially hydroxyl groups. A linear urethane-modified polyester resin (C), and the glass transition temperature of the resin (C) is 40
An electrophotographic toner composition characterized by containing as a main component an acid value of 5 or less at ~80°C.