JPH10254170A - Toner for developing electrostatic charge image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a toner excellent in fixability, anti-offsetting property and image quality without coating a fixing part in a recorder having a heat fixing mechanism with a releasing agent such as silicone oil or adding wax, etc., to a developer. SOLUTION: This toner contains linear polyester resin produced from polycarboxylic acids and polyols as a resin binder. The polycarboxylic acids chiefly include arom. dicarboxylic acid, preferably naphthalenedicarboxylic acid and the polyols include 0.05-5mol.% polypropylene glycol having an average mol.wt. of >=250 but do not include arom. polyol, especially a bisphenol deriv.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording apparatus involving heat fixing, mainly an electrophotographic printer such as a laser printer or an LED printer, a printing apparatus, or an electrostatic recording system such as ion flow, ion injection, discharge recording and the like. The present invention relates to an electrostatic image developing toner used for developing a latent image due to an electrostatic charge in printers and printing equipment using the same. More specifically, the present invention relates to a toner for developing an electrostatic image which is excellent in color image recording quality, and which does not require a release agent such as silicone oil at the time of thermal fixing, which has been demanded due to recent miniaturization and maintenance-free printers. .

[0002]

2. Description of the Related Art In an electrophotographic system, an electrostatic recording system or the like, a powder which develops an electrostatic latent image and is finally transferred to a base material such as a recording paper or a film to form an image is referred to as a toner. As such a toner for developing an electrostatic image, a colorant, a charge controlling agent, and the like are added to a binder resin, kneaded, and then pulverized, further classified, and a fluidity modifier or the like is externally added as necessary. Particles produced by a pulverization method are used. As the binder resin, a styrene / acrylic copolymer resin has been mainly used. However, in recent years, a polyester resin having an excellent low-temperature fixing property and an excellent image surface gloss tends to be used with the increase in speed and color.
The polyester resin mainly used is an unsaturated polyester resin obtained by polycondensation of an aliphatic unsaturated carboxylic acid such as fumaric acid and maleic acid with a diol having a bisphenol structure. Recently, a saturated polyester resin comprising an aromatic polycarboxylic acid such as terephthalic acid and isophthalic acid and an aliphatic diol such as ethylene glycol, an alicyclic diol such as cyclohexane dimethanol, and the above-mentioned aromatic diol having a bilphenol structure. Many patent proposals have been made. Since the polyester resin has excellent gloss on the image surface after fixing, it has good color development and realizes a wide color reproduction range. In particular, when an image is recorded on a transparent film such as an overhead projector, the light transmittance is high and the quality of the projected image is high. Generally, in a dry electrophotographic system or an electrostatic recording system, a toner obtained by developing an electrostatic latent image on a recording sheet is heated and fixed. As a heating method, a heat roll is generally used. In some models, a method of heating with a thermal head or the like via a heat-resistant film or the like has been put to practical use.

When the toner particles come into contact with such a heat source, the toner particles are melted and fixed on the recording paper. However, the molten toner resin partially adheres not only to the recording paper but also to the heat source (roll surface or film surface) side. Contaminates the fixing roll or film surface. This phenomenon is called the offset phenomenon,
If the fixing process is further continued with the contaminated fixing roll, the contamination is transferred to the subsequent recording paper, and the quality of the recorded image is significantly reduced. In order to prevent such an offset phenomenon, generally, a silicone rubber, a fluorine rubber or the like having high releasability is used as a fixing roll, and a release agent such as silicone oil is applied to the surface.

[0004] However, the method of applying a release agent such as silicone oil is not preferable because the size of the fixing device is increased, the cost is increased, and the device is complicated and troubles are liable to occur. In addition, it becomes necessary to supply silicone oil as a consumable, and maintenance becomes complicated. Furthermore, the recording paper may become sticky because the silicone oil adheres to the recording paper. In particular, when recording on a transparent film for an overhead projector, the surface is very sticky, which may cause image contamination due to fingerprints or the like.

In order to prevent such an offset phenomenon, improvements have been made in the binder resin of the toner.
It is known that the offset phenomenon can be reduced by broadening the molecular weight distribution of the binder resin and partially crosslinking or gelling, and many patent proposals have been made. However, the offset phenomenon has not been completely prevented without applying silicone oil to the heat roll.

Various proposals have been made regarding the composition of the binder resin. Particularly, in a polyester resin, an attempt has been made to avoid an offset phenomenon by copolymerizing an alkyl-substituted succinic acid or the like, thereby introducing a long-chain alkyl group into a polyester side chain to lower the surface tension of the resin. However, such measures cannot solve problems such as decomposition odor, coloring, and reduction in blocking resistance of the resin caused by the alkyl-substituted succinic acid.

JP-A-5-94040 discloses etherified diphenols which are aromatic diols and 3 to 4 repeating units.
It has been proposed to use a non-linear polyester containing 15 to 40 mol% of a polyalkylene glycol as an essential component. Japanese Patent Application Laid-Open No. H7-181735 similarly proposes using a crosslinked polyester resin containing aromatic diols and polypropylene glycol having a molecular weight of 500 to 2000 as essential components. Such a proposal is to solve the above-mentioned problems of the alkyl-substituted succinic acid. In other words, an offset resistance is imparted by copolymerizing a polyalkylene glycol, and an attempt is made to introduce a large amount of an aromatic diol in order to increase the glass transition temperature lowered by the polyalkylene glycol copolymerization. Although the offset resistance is improved by such a measure, the use of aromatic diols, substantially bisphenol A derivatives, leads to deterioration of the weather resistance of the resin and a decrease in the plasticizer resistance for vinyl chloride.

Many proposals have also been made regarding improvements in the components of the toner. The toner is produced by kneading and dispersing a colorant, a charge control agent, and in some cases, a magnetic powder and the like into a binder resin, and externally adding a fluidizing agent after pulverizing and classifying by a jet mill or the like. It has been proposed to reduce the offset phenomenon by blending waxes. For example, JP-A-59-164
560 and JP-A-59-228661 propose that an amide wax, a ketone wax, a specific alkyl ketene dimer, or the like is blended as an offset preventing agent. It has been shown that this technique can prevent the offset phenomenon without applying silicone oil to the heat roll. However, when such waxes are added, the resin layer becomes opaque and cloudy due to the phase separation between the wax and the binder resin, and the color image quality is remarkably deteriorated. Only a projection image of a color tone can be obtained.

[0009]

As described above, in the conventional image recording technique of performing thermal fixing using the toner for developing an electrostatic image, particularly in the recording of a color image,
It is essential to use a release agent such as silicone oil for the fixing machine, which is a hindrance to the spread of small color machines. In addition, although it has been reported that the method of adding a release agent such as a wax to a toner enables fixing without using a silicone oil, a sufficiently high image quality cannot be obtained in a color image. In view of such circumstances, the present inventors have conducted intensive studies to avoid the offset phenomenon without using silicone oil for the fixing device and obtain a toner capable of realizing higher image quality. Reached.

[0010]

That is, the present invention relates to a polyvalent carboxylic acid mainly composed of an aromatic compound and a polyvalent carboxylic acid having a molecular weight of 250.
The above object is attained by an electrostatic image developing toner characterized in that a polypropylene resin is an essential component and a linear polyester resin obtained from a polyhydric alcohol substantially not containing an aromatic ring is used as a binder resin. Solvable.

The polyester resin in the present invention is obtained mainly by polycondensation of a polycarboxylic acid and a polyhydric alcohol. As the polyvalent carboxylic acids used in the polyester resin, for example, terephthalic acid, isophthalic acid, orthophthalic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid,
Aromatic dicarboxylic acids such as diphenic acid, aromatic oxycarboxylic acids such as p-oxybenzoic acid p- (hydroxyethoxy) benzoic acid, succinic acid, alkyl succinic acid, alkenyl succinic acid, adipic acid, azelaic acid, sebacic acid, Aliphatic dicarboxylic acids such as dodecane dicarboxylic acid, fumaric acid, maleic acid, itaconic acid, mesaconic acid, citraconic acid, hexahydrophthalic acid, tetrahydrophthalic acid, dimer acid, trimer acid, hydrogenated dimer acid, cyclohexanedicarboxylic acid, cyclohexene Unsaturated aliphatics such as dicarboxylic acids, and alicyclic dicarboxylic acids and the like, and as the polyvalent carboxylic acids, trimellitic acid, trimesic acid, and trivalent or more polyvalent carboxylic acids such as pyromellitic acid, etc. Can be used.

Examples of the polyhydric alcohols used in the polyester resin include aliphatic polyhydric alcohols, alicyclic polyhydric alcohols, and aromatic polyhydric alcohols.
Aliphatic polyhydric alcohols include ethylene glycol
, Propylene glycol, 1,3-propanediol-
2,3-butanediol, 1,4-butanediol
1,5-pentaneddiol, 1,6-hexanediol, neopentyl glycol, diethylene glycol
, Dipropylene glycol, dimethylol heptane,
2,2,4-trimethyl-1,3-pentaneddiol,
Polyethylene glycol, polypropylene glycol,
Aliphatic diols such as polytetramethylene glycol,
Triols and tetraols such as trimethylolethane, trimethylolpropane, glycerin and pentaerthritol can be exemplified.

The alicyclic polyvalent alcohols include 1,4-
Cyclohexanediol, 1,4-cyclohexanedimethanol, spiroglycol, hydrogenated bisphenol A, ethylene oxide adducts and hydrogenated bisphenol A adducts of propylene oxide, tricyclodecanediol, Examples include tricyclodecane dimethanol, dimer diol, hydrogenated dimer diol, and the like. Examples of aromatic polyhydric alcohols include para-xylene glycol,
Meta-xylene glycol, ortho-xylene glycol,
Examples thereof include 1,4-phenylene glycol, an ethylene oxide adduct of 1,4-phenylene glycol, bisphenol A, an ethylene oxide adduct of bisphenol A, and a propylene oxide adduct.

Further, as a polyester polyol, ε
-Lactone-based polyester polyols obtained by ring-opening polymerization of lactones such as caprolactone. Monofunctional monomers may be introduced into the polyester for the purpose of blocking the polar group at the terminal of the polyester polymer and improving the environmental stability of the toner charging characteristics. Monofunctional monomers include benzoic acid, chlorobenzoic acid, bromobenzoic acid, parahydroxybenzoic acid, monoammonium sulfobenzoate, monosodium sulfobenzoate, cyclohexylaminocarbonylbenzoic acid,
n-dodecylaminocarbonylbenzoic acid, tert-butylbenzoic acid, naphthalenecarboxylic acid, 4-methylbenzoic acid, 3-methylbenzoic acid, salicylic acid, thiosalicylic acid,
Phenylacetic acid, acetic acid, propionic acid, butyric acid, isobutyric acid,
Use of monocarboxylic acids such as octanecarboxylic acid, lauric acid, stearyl acid and lower alkyl esters thereof, and monoalcohols such as aliphatic alcohols, aromatic alcohols and alicyclic alcohols. Can be.

[0015] The polyester resin in the present invention comprises a polyvalent carboxylic acid mainly composed of aromatic compound and a molecular weight of 250.
The above is a linear polyester resin obtained from polyhydric alcohols containing polypropylene glycol as an essential component.
The average molecular weight of the polypropylene glycol is preferably 400 or more, more preferably 800 or more.
It is preferable to use those having a value of 00 or more, and more preferably 2000 or more. Polyhydric alcohols include polypropylene glycol GA.RTM. Having a propylene glycol content of 99.9 to 90 mol% and a molecular weight of 250 or more. 0
5 to 5 mol% or 95 to 60% by weight of propylene glycol 5 to 4 of polypropylene glycol having a molecular weight of 250 or more
0% by weight, preferably 5 to 70% by weight of propylene glycol and 15 to 15% of polypropylene glycol having a molecular weight of 250 or more.
More preferably, it is 30% by weight.

In the present invention, the polyhydric alcohol component does not substantially contain aromatic diols, particularly bisphenol A derivatives. The phrase “substantially not contained” means that the content is essentially 5 mol% or less, preferably 3 mol% or less, more preferably 1 mol% or less based on all alcohol components.
It is preferably not more than mol%, and even more preferably not contained at all. In the present invention, the polyvalent carboxylic acid is 1 to 5
Preferably, it contains 0 mol% of naphthalenedicarboxylic acid. The content of naphthalenedicarboxylic acid is 5
The content of naphthalenedicarboxylic acid in the acid component is preferably 40 mol%, more preferably 15 to 35 mol%, and the content mol% of the naphthalenedicarboxylic acid with respect to the total polyhydric alcohol component is represented by “X” wt%. ,
It is preferably in the range of "0.8X" to "2.0X" mol%. If the composition ratio of the polypropylene glycol to the naphthalenedicarboxylic acid is out of this range, the glass transition temperature of the polyester resin may decrease, and the storage stability of the toner may decrease. If the ratio is less than this range, the offset resistance may decrease.

The polyester resin used in the present invention must have a glass transition point of 50 to 80 ° C., preferably 55 ° C. or higher, more preferably 60 ° C. or higher, and still more preferably 65 ° C. or higher. . When the glass transition point is lower than this, there is a tendency to agglomerate during handling or storage, which may cause a problem in storage stability. The softening point of the resin used in the present invention is 80 to 15
Preferably it is in the range of 0 ° C. In a toner in which the softening temperature of the resin is kept lower than this, there is a tendency to agglomerate during handling or storage, and especially during long-term storage, the fluidity may be significantly deteriorated. If the softening point is higher than this, the fixability will be impaired. Further, since it is necessary to heat the fixing roll to a high temperature, the material of the fixing roll and the material of the base material to be copied are limited.

The above is the polyester resin as the binder resin which characterizes the toner for developing an electrostatic image of the present invention. In the present invention, it is essential to use such a polyester resin as a main component of all the binder resins. The present polyester resin is at least 50% by weight of the binder resin, preferably at least 70% by weight, more preferably at least 80% by weight.
% Or more. The colorant, charge control agent, fluidity modifier and the like incorporated in the electrostatic image developer of the present invention are not particularly limited, and known ones can be used as needed. Dyes, pigments, carbon black, or the like may be used as the colorant. These dyes, pigments and car
Bon black or the like may be used alone, or may be used in combination as needed. It is particularly preferable to use a dye from the viewpoint of spectral transmission characteristics. When a pigment is used for coloring, benzidine-based or azo-based pigments are used for yellow-coloring, and azo lake-based or rhodamine-free pigments are used for magenta coloring.
Ki-based, quinacridone-based, naphthol-based, and diketopyrrolopyrrole-based pigments are preferably used, and phthalocyanine-based pigments are preferably used for cyan coloring. When black toner is obtained, carbon black or the like may be used. Car
As Bon Black, thermal black, acetylene black, channel black, furnace black,
Lamp black or the like can be used. When a dye is used for coloring, azo, nitro,
Quinoline, quinophthalone and methine dyes are preferably used for magenta coloring, and anthraquinone, phthalocyanine and indoaniline dyes for cyan coloring are preferably used.

The method for producing the toner for developing an electrostatic charge image in the present invention is not particularly limited. A colorant, a charge control agent and the like are mixed with a binder resin and then pulverized with a jet mill or the like to remove the fluidity modifier or the like. A so-called pulverization method for adding can be used. When the content of polypropylene glycol is relatively large, the pulverizability of the resin is reduced. Therefore, it is sometimes preferable to cool the inside of the pulverization system and perform the pulverization. Further, as another method, a toner is formed by a wet process in which a colorant, a charge control agent, and the like are mixed and dispersed in a solution including a solvent and a binder resin, and then the solution is introduced into an aqueous system, suspended or coarsely emulsified, and classified and dried. Can be used. If the polypropylene glycol content is relatively high, the pulverizability of the resin is reduced, so that it may be preferable to use a method other than the pulverization method exemplified below. Preferably 5-
Polyester resin that has been made hydrophilic by copolymerizing a monomer having an ionic group such as sodium isophthalic acid is dissolved in a water-soluble solvent such as ketones, alcohols, tetrahydrofuran, cellosolves, and dioxane. Then, water is added, and the solvent is removed by azeotropic distillation, whereby an aqueous dispersion of the polyester resin can be obtained.
Slow coagulation is possible by adding an appropriate electrolyte into such an aqueous dispersion system and controlling the temperature. In particular, a method of adding an amino group-containing ester composed of an amino alcohol and a carboxylic acid, hydrolyzing the ester in the system by raising the temperature, adjusting the pH, and the like to form an amine salt of a carboxylic acid,
This is preferable as a method for leading to a slow aggregation region. Particles containing a pigment (carbon black) can be produced if water-dispersed fine particles such as a pigment and carbon black coexist in a mildly agglomerated region. It is also possible to obtain toner particles colored with the dye by coexisting the dye at the time of emulsification, and it is also possible to post-color the obtained colorless particles by a high-temperature dispersion dyeing method.

The aromatic polycarboxylic acid as the first essential component in the copolymerized polyester resin of the present invention gives a hard skeleton to the main chain of the polyester resin, and the polypropylene glycol as the second essential component is It forms a soft and fluid segment in the main chain of the polyester resin.By balancing the two, the storage stability as a powder and the function of suppressing the adhesiveness when the resin is in a molten state are achieved. It is compatible with each other, and as a result, leads to improvement of anti-offset property. Since the glass transition temperature of the polyester resin is lowered by copolymerizing the polypropylene glycol, the storage stability as a powder is lowered. Therefore, it is necessary to devise a method that does not lower the glass transition temperature. The naphthalenedicarboxylic acid preferably used has a function of increasing the glass transition temperature of the polyester resin. Many copolymerization components are added to increase the glass transition temperature. However, when polypropylene glycol is used as the glycol component, combining naphthalenedicarboxylic acid with a dicarboxylic acid component achieves particularly excellent toner properties. Most preferred above. In recent years, it has been pointed out that bisphenol A, which is usually used to increase the glass transition temperature, has mutagenic properties, and it is not preferable to use bisphenol A as a raw material for toner, which is a powder that is easily dispersed. In addition, light resistance is poor, and dyes and pigments are deteriorated, particularly when a dye is used. The ionic group, which is preferably a component to be introduced, is necessary for producing a substantially spherical toner in a wet process. Spherical toner is said to be highly suitable for recent non-magnetic one-component development systems, etc.
Similarly, the toner of the present invention, which can realize a silicone oil-less fixing mechanism required for a small color machine, has a toner composition suitable for non-magnetic one-component development, which is an effective developing mechanism for a small color machine. Is particularly important in enhancing the value of the invention. Being a linear polyester is an important requirement in the present invention. In general, a resin for toner is made non-linear by introducing a branch, and at the same time, has a broadened molecular weight distribution, and imparts viscoelastic properties at the time of hot melting of the resin to thereby improve the offset resistance. However, particularly for the purpose of reproducing a high-quality color image, the linear resin is superior in the smoothness of the fixing surface, and a higher-quality image can be obtained.

The present invention will be described in more detail with reference to the following Examples, which by no means limit the present invention. The physical properties and the like in the examples were measured by the following methods. 1. The acid value resin was dissolved by heating in benzyl alcohol, cooled to room temperature, and titrated with a 1/50 N KOH benzyl alcohol solution. 2. Glass transition temperature The glass transition temperature Tg was defined as the intersection between the tangent to the endothermic curve near Tg and the tangent to the baseline when measured at a heating rate of 5 ° C./min using a differential scanning calorimeter. 3. Temperature at which melt viscosity becomes 10000 poise Using a Shimadzu elevated flow tester CFT-500C, nozzle 1.0 mmφ × 10 mmL, load 30 kg, heating rate 3
It was determined under the conditions of ° C / min and a sample amount of 1.0 g. 4. Number average molecular weight Determined by gel permeation chromatography. 5. Composition analysis The resin was decomposed with hydrazine and analyzed by NMR method, which was corrected based on the result of quantitative analysis performed by liquid chromatography. 6. Transparent resin was methyl ethyl ketone / tetrahydrofuran = 2 /
Dissolve in the mixed solution of No. 1, cast into a glass substrate, and then dry to form a coating film having a thickness of 50 ± 5 μm. Measure the light transmittance in the region of 400 to 700 nm with a spectrophotometer. 90% or more was evaluated as "O" as being transparent, and less than 90% was evaluated as "X" as being opaque. 7. Coloring The sample used for the transparency evaluation was placed on a white standard plate, and CIELAB 19 was measured with a Minolta colorimeter CR-210.
The chromaticity coordinates of the 76 (D65 light source) system were measured, and those with b * of 3 or more were rated as “x” with coloring, and those with less than 3 were rated as “○” without coloring.

Examples (Example of polymerization of polyester resin) In an autoclave equipped with a thermometer and a stirrer, 73 parts by weight of dimethyl naphthalate 97 parts by weight of dimethyl terephthalate 39 parts by weight of dimethyl isophthalate Parts, 167 parts by weight of propylene glycol and 0.07 parts by weight of tetrabutoxy titanate were charged and heated at 170 to 220 ° C. for 180 minutes to carry out a transesterification reaction. Then, the reaction system was cooled to 170 ° C., 21 parts by weight of polypropylene glycol (average molecular weight: 2,000) 0.2 parts by weight of Irganox 1330 [manufactured by Ciba Geigy] was added, and the temperature of the reaction system was raised to 220 to 240 ° C. The reaction was continued for 90 minutes at a system pressure of 1 to 10 mmHg. (A1) was obtained. Thereafter, polymerization was carried out in the same manner as in Table 1. Was obtained. Table 1. Medium, NDC: naphthalenedicarboxylic acid TPA: terephthalic acid IPA: isophthalic acid DSA: dodecenylsuccinic acid TMA: trimellitic acid EG: ethylene glycol PG: propylene glycol PPG950: polypropylene glycol (average molecular weight 950) PPG1200: polypropylene glycol (average molecular weight 1200) PPG2000: polypropylene glycol (average molecular weight 2000) BPA-EO: bisphenol A ethylene oxide adduct BPA-PO: bisphenol A propylene oxide adduct DADO: hydrogenated dimer diol.

Example 1 95 parts by weight of the copolymerized polyester resin (A1) obtained in the polymerization example of the polyester resin was coarsely pulverized by a chopper mill, and a copper phthalocyanine cyan pigment Heliogen Blue S7084 [BASF] 5 After preliminarily mixing with a weight part with a ball mill, kneading with a hot roll mill, cooling, coarsely pulverizing again, and then finely pulverizing with a jet mill, followed by classification to obtain a cyan toner (C1) having an average particle diameter of 7.2 μm. Obtained.
5 parts by weight of the obtained toner is mixed with a ferrite carrier F-
100 [manufactured by Powder Tech Co., Ltd.] and 95 parts by weight were charged into a ball mill and stirred for about 15 minutes to obtain a developer. (Fixing characteristics) The obtained developer was loaded into a modified testing machine based on a dry electrophotographic copier so that the heat roll temperature of the fixing machine could be adjusted and the use / non-use of silicone oil could be selected. As a result, a clear image without fog and blur was obtained. Silicone oil is not used, and the temperature of the heat roll is increased from 80 ° C to 10 ° C.
The image was taken out one by one, and the fixing state and the offset generation state were observed. The fixing start temperature was 110 ° C., and the offset start temperature was 160 ° C. The fixability was evaluated by attaching a cellophane tape to an image portion having a toner thickness of about 5 μm or more at a constant pressure, peeling the cellophane tape at a constant speed, and determining whether toner adhered to the cellophane tape. The feed speed of the recording paper was about 20 sheets per minute in the A4 vertical direction. (Vinyl chloride plasticizer resistance) In a fixing test, an image obtained by fixing at an intermediate temperature between the fixing start temperature and the offset start temperature is applied to a transparent vinyl chloride sheet containing DOP (dioctyl phthalate) as a plasticizer. The scissors were left in an environment of 50 ° C. for 24 hours under a load of 1 kg applied to a 5 cm square, and the presence or absence of toner attached to the vinyl chloride sheet was examined. "X" indicates that the vinyl chloride sheet had toner adhered, and "O" indicates that it did not. (Image Transparency) The heat roll temperature was set to a fixing start temperature + 10 ° C., an image was formed and fixed on a transparent polyester film without using silicone oil, and the image was projected and observed with an overhead projector. The projected image had a clear cyan color. Table 2 shows the results. Shown in

Examples 2 to 4, Comparative Examples 1 to 4 Toner (C2) was prepared by using the copolymerized polyester resin (A2) obtained in the polymerization example of the polyester resin and operating the same as in Example 1 except for the above. Obtained. Hereinafter, the toners of Example (C3) are similarly prepared from the copolymerized polyester resins (A3) to (A8).
To (C4) and Comparative Example Toners (C5) to (C8).
Thereafter, evaluation was performed in the same manner as in Example 1. Table 2 shows the results. Shown in

Examples 6 to 8 Using a copolymerized polyester resin (A4), 5 parts by weight of a magenta pigment Hostaperm Pink E02 (toner grade) [manufactured by Hoechst] and Nova Palm Yellow P-HGVP2066 as a yellow pigment [Hoechst) 5M parts by weight, and 5 parts by weight of PRINTEX 150T [manufactured by Degussa] as a black pigment, to obtain toners (M4), (Y4) and (K4) in the same manner as in the following Examples. The results evaluated in the same manner as in the following Examples are shown in Table 2. (Color image forming test) For color printing, a toner (C4) obtained in the example using a YMCK 4-color positive image (landscape photograph) color-separated and halftone-converted with 175 lines as a document, The toner (M4)
Using (Y4) and (K4), the fixing temperature was set to an intermediate value between the average value of the fixing start temperatures of the four colors and the average value of the offset occurrence temperatures by the above-described tester. A full-color image was formed by superimposing a magenta image, then cyan and black in this order on the obtained image. The obtained image shows a clear color although some misregistration occurs, shows good fixability without causing offset even in a portion where toners of different colors overlap, and also preferably produces a secondary color. Met. Similarly, a full-color image was formed on a transparent film and observed with an overhead projector, but a clear projected image could be obtained.

[0026]

As described above, the toner according to the present invention has a sufficient fixing temperature range (difference between the offset start temperature and the fixing start temperature) without applying a release agent such as silicone oil to the fixing roll. And excellent in the transparency of the resin layer and the surface smoothness of the fixed image, so that the reproducibility of the color image is excellent.

[0027]

[Table 1]

[0028]

[Table 2]

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yozo Yamada 2-1-1 Katada, Otsu City, Shiga Prefecture Toyobo Co., Ltd. Research Laboratory

Claims (4)

[Claims] 1. A binder comprising: a polyvalent carboxylic acid mainly composed of aromatics; and a linear polyester resin obtained from a polyhydric alcohol containing a polypropylene glycol having a molecular weight of 250 or more as an essential component and substantially not containing an aromatic ring. A toner for developing an electrostatic image, wherein the toner is a resin. 2. The polyhydric alcohol according to claim 1, wherein the propylene glycol is 99.9 to 90 mol% and the molecular weight is 25.
A toner for developing an electrostatic image, wherein a linear polyester resin containing 0.05 to 5 mol% of 0 or more polypropylene glycol is used as a binder resin. 3. The binder resin according to claim 1, wherein the polyhydric alcohol is a linear polyester resin containing 95 to 60% by weight of propylene glycol and 5 to 40% by weight of polypropylene glycol having a molecular weight of 250 or more. A toner for developing electrostatic images, characterized by the following. 4. The polycarboxylic acid according to claim 1, wherein
A toner for developing electrostatic images, comprising 50 mol% of naphthalenedicarboxylic acid.