JPH01185663A - Toner for developing electrostatic latent image - Google Patents

Abstract

PURPOSE:To obtain a toner which has excellent fixability and offset resistance and is suitable for fixing with a heating roller by incorporating nonlinear polyester obtd. from a monomer component contg. tri- or higher valent monomers and vegetable wax and/or montan ester wax as well as an antioxidant into the toner for developing electrostatic latent images. CONSTITUTION:The nonlinear polyester obtd. from the monomer component contg. the tri- or higher valent monomers and the vegetable wax and/or montan ester wax as well as the antioxidant consisting of a sulfur-contg. metal complex compd. are incorporated into the toner for developing the electrostatic latent images. The electrostatic latent images formed by an electrophotographic method, electrostatic recording method, electrostatic printing method, etc., are developed by this toner to improve the fixability and offset resistance and are developed by the heating roller. Fogging, and unequal solid black by use in high-temp. and high humidity environment is eliminated and the sharp image characteristic having the excellent durability is obtd.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a toner for developing electrostatic latent images formed in electrophotography, electrostatic recording, electrostatic printing, etc. .

[Background of the invention]

As a conventional electrophotographic method, U.S. Patent No. 2,297.691
No. 2,357.1li09, etc., an electrostatic latent image is formed on the surface of a photoreceptor, and the electrostatic latent image is made into a toner image using a dry developer made of colored fine powder. First, the toner image is transferred to a transfer sheet such as paper, and then permanently fixed by heating, pressure, etc. to form a copy image.

Recently, there has been a trend toward higher speed and smaller size of copying machines, and as a fixing process that meets these demands, a heated roller fixing method that has good thermal efficiency, has a compact mechanism, and is capable of increasing speed is preferably used.

However, in the heating roller fixing method, because the heating roller surface and the toner image surface come into contact, the so-called "offset phenomenon" occurs in which the toner is transferred to the heating roller surface and then transferred to the paper that is fed, staining the image. Occur.

In order to prevent such offset phenomenon, especially hot offset, Japanese Patent Publication No. 51-23354 proposes using a styrene-based cross-linked resin as a binder resin for toner, but it is only used as a styrene-based cross-linked resin. In this case, the fixing temperature rises, and under normal fixing conditions, the image becomes unfixed, causing stains due to low temperature offset in the unfixed area.

In order to cope with the above-mentioned hot offset and low-temperature offset (insufficient running stability), Japanese Patent Publication No. Sho 59-11902 proposes the use of a polyester resin having a three-dimensional network structure as a binder resin for toner.

Furthermore, it is known that vegetable-based natural waxes and montan-based ester waxes are useful for adjusting the physical properties related to the developability and fixing properties of toners.

However, the inventors of the present invention have conducted detailed studies and found that toners using such polyester resins are somewhat satisfactory in terms of preventing the offset phenomenon and improving fixing properties, but they do not work well under high temperature and high humidity conditions. It has been found that the image characteristics and durability of the heated roller fixing device are often affected.

Furthermore, since the above-mentioned two types of waxes contain a considerable amount of free alcohol and fatty acids, they have poor thermal stability and are easily decomposed. For example, the terminal functional group density increases due to oxidation during kneading, crushing, and standing after classification, and decomposition due to ozone generated by corona discharge. Moreover, when a non-linear polyester obtained from a polyvalent monomer component is used as the binder resin, the above-mentioned tendency is remarkable.

That is, when copying is performed many times in a high-temperature, high-humidity environment, the constancy of the image is lost, such as increased fogging, toner scattering, and occurrence of a solid black problem in which a solid black image is mixed with a white background. Further, toner gradually adheres and accumulates on the surface of the heating roller of the heating roller fixing device, shortening the life of the fixing roller, and the toner accumulated on the heating roller transfers to the back side of the transfer paper, causing backside stains.

[Purpose of the invention]

The present invention addresses the above-mentioned problems, and an object of the present invention is to provide a toner for developing electrostatic latent images that has good fixing properties and anti-offset properties and is suitable for fixing with a heating roller.

Another object of the present invention is to provide an electrostatic charger that provides excellent durability and clear image characteristics without causing fogging, toner scattering, or nonuniform solid black even after repeated use in high temperature and high humidity environments. An object of the present invention is to provide a toner for developing latent images.

Another object of the present invention is to provide a toner for developing electrostatic latent images which can significantly extend the life of the heating roller without causing stains on the heating roller or on the back side.

[Means for achieving the invention]

The object of the present invention is to contain a non-linear polyester obtained from a monomer component containing a trivalent or higher polyvalent monomer, a plant-based natural wax and/or a montan-based ester wax, and an antioxidant. This is achieved by an electrostatic latent image developing toner characterized by:

In addition, as an aspect of the present invention, good results can be obtained by applying a sulfur-containing metal complex compound as the antioxidant.

[Actions and effects of the present invention]

The polyester resin used as the binder resin of the toner of the present invention contains a trivalent or higher valent monomer, which gives the polyester resin a three-dimensional structure, improves the mold releasability during melting, and provides good offset resistance. do. In addition, polyester resin easily melts even at low temperatures and has good melt penetration into paper at low temperatures, making it possible to prevent low-temperature offset.

However, in polyester resins that are given a three-dimensional structure by using the monomers with a valence of 3 or more, there is no opportunity for reaction due to steric hindrance, and unreacted -COO)l from the monomers with a valence of 3 or more is not available. A large amount of groups or -〇〇 groups will remain. Furthermore, the wax according to the present invention also has a high content of -Cool groups and -OH groups.

Toners whose binder resin is made of polyester resin with a high residual amount of -〇〇〇 groups or some H groups are subject to oxidation during toner manufacturing processes such as heating and melting, kneading, etc., or to oxidation in the charger or transfer device in the copying machine. Due to the oxidation of the toner surface portion by ozone generated from As more copies are made, the adsorption of moisture in the air on the toner surface gradually increases.If the adsorption of moisture becomes excessive, the charge on the toner surface may leak, especially under conditions of high temperature and humidity. This can lead to an increase in fog due to a decrease in toner charge, toner scattering due to a decrease in electrostatic adhesion between toner particles and carrier particles, expansion of charge distribution (increase in low charge toner particles), and increase in moisture content. Due to the decrease in fluidity of toner particles due to adsorption, developability is reduced, and undeveloped areas of white background appear in a solid black image, impairing the uniformity of the solid black.

Due to such factors, the durability of the developer is eventually lost.

In addition, in the heating roller fixing step, the adhesion of toner particles to the heating roller surface increases due to an increase in some 〇〇 groups and some H groups as oxidation progresses on the toner surface, and some of the toner particles becomes more likely to adhere to and accumulate on the surface of the heating roller. When this phenomenon becomes excessive as the number of copies increases, the toner accumulated on the upper roller of the heating roller transfers to the lower roller, contaminates the lower roller, and accumulates on the lower roller during fixing. The toner transfers to the surface of the transfer paper, causing stains on the back surface.

Therefore, the toner of the present invention has been studied with a focus on preventing the progress of oxidation, which is considered to be the main cause of the above-mentioned problems. It was discovered that the problem could be solved by incorporating an antioxidant.

That is, the sulfur-containing metal complex antioxidant used in the present invention prevents the progress of oxidation of the polyester resin, which is relatively easily oxidized during the kneading process in the manufacturing process, and also prevents the progress of oxidation of the toner surface due to ozone generated in the copying machine. can be prevented.

When using such a toner, the progress of oxidation is prevented, which prevents excessive adsorption of moisture onto the toner surface, which prevents a decrease in the amount of charge on the toner and a decrease in the resistance of the toner surface, resulting in a long-term lifespan. Increased fogging and toner scattering due to use can be prevented. Further, since the charge amount distribution can be narrowed and the fluidity of the toner is not reduced, the developability is also stable and good, and a uniform solid black image can be provided. Therefore, durability is also improved.

In addition, one coon group or -OH on the toner surface
This prevents the increase in the number of groups, and the effect spreads to the prevention of increase in adhesion to the heating roller, prevention of toner adhesion and accumulation on the heating roller, prevention of contamination of the lower roller, and prevention of contamination of the back surface.

In addition to the above-mentioned effects, the present invention also has the effect of providing a toner with more stable triboelectric charging properties than conventional toners by selecting an antioxidant with good triboelectric charging properties.

Next, specific examples of sulfur-containing metal complex compounds as antioxidants according to the present invention will be listed, but the present invention is not limited to these examples.

The melting point ("O) is also written in parentheses.

: Exemplary compounds: SC1, zinc diethyldithiocarbamate (175°) SC2, zinc dibutyldithiocarbamate SC3, nickel dibutyldithiocarbamate (>85°) A melting point of 20° is particularly important in maintaining good toner blocking resistance and fluidity. The melting point is preferably 230° C. or higher, and preferably 230° C. or lower in order to maintain the fixing properties of the toner.

Further, the content in the toner is preferably 0.01 to 10% by weight, particularly 0.1 to 5% by weight, and if it is less than 0.01% by weight, the antioxidant effect is small, and 10% by weight.
If the amount exceeds % by weight, the toner offset property may deteriorate, contaminating the fixing roller, and impairing the durability of the fixing roller.

The binder resin used in the present invention is preferably a polyester resin, which is obtained by condensation polymerization of a divalent or higher polyhydric alcohol monomer and a divalent or higher polyhydric carboxylic acid monomer. A non-linear polyester resin made non-linear using a monomer having a valence of 3 or more is preferable in terms of offset resistance.

Examples of diols include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-7'ropylene glycol, 1,4-butanediol, neopentyl glycol,
Diols such as 1,4-butynediol, 1,4-bis(hydroxymethyl)cyclohexane, hisphenols such as bisphenol A1 hydrogenated bisphenol A, polyoxypropylene (2,2)-2,2-(4) -hydroxyphenyl)propane, polyoxypropylene (
3,3)-2,2-bis(4-hydroxyphenyl)propane, polyoxyethylene(2,0)-2,2-bis(4-hydroxyphenyl)propane, polyoxypropylene(2,0)-poly Oxyethylene (2,0)-2
, 2-his(4-hydroxyphenyl)propane, etherified bisphenols such as polyoxypropylene (6,0)-2,2-bis(4-hydroxyphenyl)propane, and other dihydric alcohol monomers. can be mentioned.

Matashicarponic acids include ÷leic acid, 7-malic acid, succinic acid, adipic acid, sebacic acid, malonic acid, itaconic acid,
Examples include derivatives such as citraconic acid, mesaconic acid, glutaconic acid, cyclohexanedicarboxylic acid, heptatalic acid, isophthalic acid, terephthalic acid, and acid anhydrides or esters thereof.

For non-linearization, in addition to the above divalent monomer components, a trivalent or higher valent monomer component may be used. Examples of such multivalent monomers, such as trivalent or higher polyol monomers, include sorbitol! , 2,3.6-hexanetetrol, 1.4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, Satsuma M, 1.2.4-butanetriol, 1.2.
5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane,! , 3,5-trihydroxymethylbenzene, and others.

Examples of trivalent or higher polycarboxylic acid monomers include 1.2.4-benzenetricarboxylic acid and l.

2.5-benzenetricarboxylic acid, 1.2.4-cyclohexanetricarboxylic acid, 2,5.7-su7talentricarboxylic acid, 1.2.4-naphthalenetricarboxylic acid, 1.2゜4-butanetricarboxylic acid , 1.2.5-hexanetricarboxylic acid, l,3-dicarboxyl-2-
Methyl-2-methylenecarboxylpropanecarboxyl)methane, pyromellitic acid, 1.2.7.
Examples include 8-octanetetracarboxylic acid, cyclohexanetetracarboxylic acid, 1.2.5.6-hexanetetracarboxylic acid, embol trimer acid, and acid anhydrides or lower alkyl esters thereof.

The above trivalent or higher polyvalent monomer component accounts for 0.1 to 80 mol%, preferably 5 to 5 mol% of each of the alcohol component or acid component as a structural unit in the polymer.
It is desirable that the content be 0 mol%. If it is too small, the durability will be poor, and if it is too large, the fixing performance will be poor.

Among the above-mentioned monomer components, benzenetricarboxylic acid is preferably used because it has excellent effects such as fixing properties, anti-offset properties, and triboelectric charging properties.

Further, it is preferable to use etherified phenols as the diol component since they are excellent in offset resistance and durability of the triboelectric developer.

The softening point of the polyester resin of the present invention is 100 to 150°
C is preferable, and if it is less than 100° C., the offset resistance will be poor; if it is more than 150′a, the fixing property will be poor.

Furthermore, the glass transition point of the polyester resin of the present invention is 55
Preferably, the temperature is from 70°C to 70°C, and if it is less than 55°C, the blocking resistance will be poor, and if it exceeds 70°C, the fixing property will be poor.

Further, the acid value of the polyester resin of the present invention is preferably 50 or less, and if it exceeds 50, fogging, toner scattering,
The fixing roller may become heavily soiled.

The polyester resin of the present invention is prepared by combining a polycarboxylic acid component and a polyol component in an inert gas atmosphere to a concentration of 100 to 250%.
It can be produced by a polycondensation reaction in the temperature range of .degree. C., and a catalyst such as diptyltin oxide, zinc oxide, titanium oxide, tin oxide, etc. may be used to accelerate the reaction.

Next, specific examples of the plant-based natural wax and montan-based ester wax according to the present invention will be given.

(1) Plant-based natural wax 1.1 Plant-based wax (2) Montan-based ester wax (Hoechst) The wax is 0.5 to 25vt relative to the binder of the toner.
%, preferably l=10 wt%.

The toner of the present invention may also contain other resins such as linear polyester, polyamide, polyurethane, epoxy, styrene, etc.
Although a resin such as an acrylic copolymer may be contained, the proportion thereof is preferably within a range of 30% by weight or less of the resin.

In the present invention, toner components such as a colorant, a charge control agent, a fixability improver, magnetic particles, and other property improvers may be dispersed and contained in the toner particles.

All known colorants can be used in the toner of the present invention, such as carbon black, benzidine yellow, quinacridone, and rhodamine 81 phthalocyanine blue.

The magnetic particles used in the toner of the present invention include substances that are magnetized when placed in a magnetic field, such as powders of ferromagnetic metals such as iron, cobalt, and nickel, or compounds such as magnetite, maghematite, and ferrite. There is. When iron oxide magnetic material is used as a colorant, it is preferably contained in the toner in an amount of 10 to 80% by weight.

Further, the charge control agent used in the toner of the present invention includes:
Examples include metal complex dyes and nigrosine dyes.

Examples of the fixability improver contained in the toner of the present invention include polyolefins, fatty acid metal salts, fatty acid esters, partially saponified fatty acid esters, higher fatty acids, higher alcohols, polyhydric alcohol esters, silicone fluorocarbons, aliphatic fluorocarbons, and the like. be able to. By using such a fixing property improving agent, the mold release properties are improved and paper jams in the heat roller fixing device can be prevented.

To give an example of a preferred method for producing the toner of the present invention, first, the material resin of the binder resin or a toner component such as a colorant added thereto as necessary is melt-kneaded using an extruder, and after cooling, The particles are pulverized using a jet mill or the like, and then classified to obtain a toner having a desired particle size.

Furthermore, the toner of the present invention is preferably used by mixing carrier particles with iron powder, ferrite powder, particles whose surfaces are treated with resin, etc., for stabilizing triboelectric charging. In particular, the use of resin-surface-treated particles as carrier particles is effective in improving the durability of the developer and stabilizing triboelectric charging against environmental changes.

The toner of the present invention further improves fluidity, developability,
It is preferable to mix and use inorganic fine particles that improve transferability.

The primary particle diameter of the inorganic fine particles is preferably 5I11μ to 2μm, particularly preferably 5μ to 500μm.

In addition, the specific surface area by BET method is 20-500m”/
9 is preferred. The proportion of the inorganic fine particles used is preferably 0.01 to 5% by weight, particularly preferably 0.01 to 2.0% by weight of the toner.

Specific examples of inorganic fine particles include silica, alumina, titanium oxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, silica sand, clay, mica, wollastonite, diatomaceous earth, chromium oxide, and chromium oxide. Examples include cerium, red iron oxide, antimony trioxide, magnesium oxide, zirconium oxide, barium sulfate, barium carbonate, calcium carbonate, silicon carbide, and silicon nitride. Particularly preferred is fine silica powder.

As specific examples of fine silica powder, there are various commercially available products, but those having a hydrophobic group on the surface of the fine particles are particularly preferred.For example, "Aerosil R-972J, rAerosil R
-9744, Aerosil R-805J, Aerosil R-812J (manufactured by Aerosil), Taranox 500J (manufactured by Talco), etc. can be preferably used.

As a method for fixing the toner of the present invention, a hot roller fixing method is preferred, in which the upper roller of the fixing roller is coated with a fluorine-based resin, and the lower roller is silicone rubber or a fluorine-based resin coated on silicone rubber. A relatively soft material is preferable in terms of fixing properties, anti-offset properties, prevention of paper jams, and durability of the roller.

[Synthesis examples and examples]

Next, synthesis examples and examples of the present invention for typical resins of the present invention will be described, but the present invention is not limited to these examples.

: Synthesis example: (1) Binder A ・Polyoxypropylene (2,2)-2,2-bis(4
'-Hydroxyphenyl)propane 443g・Polyoxyethylene(2)-2,2-bis(4'-hydroxyphenyl)propane 1769・Terephthalic acid 1209・Diisopropyl orthotitanate (esterification catalyst) 0.89 or more substances , a thermometer, a stainless steel stirrer, a glass nitrogen gas inlet tube, and a down-flow condenser. was introduced to maintain an inert atmosphere inside the flask, and the temperature was increased to 2.
The temperature was raised to 30°C and the reaction was carried out under stirring. When the water produced by the reaction stopped flowing out, the acid value was measured and found to be 1.5.

Furthermore, 1,2,4-benzenetricarboxylic acid anhydride 1399 was added and reacted for about 8 hours, and the reaction was terminated when the acid value reached 17.

The obtained resin was a pale yellow solid, and the softening point of this resin was determined by "70-Tista CFT-500J (manufactured by Shimadzu Corporation)".
It was measured at 125°C.

(2) Binder B ・Polyoxypropylene (2,2)-2,2-bis(4
'-hydroxyphenyl)propane 482g/polyoxyethylene(2)-2,2/bis(4'-hydroxyphenyl)propane 1269/1,6-hexanediol 249/7 malic acid
1749 Diisopropyl orthotitanate (esterification catalyst) 0.89 or more substances are reacted in the same manner as in the production of binder A, and further, anhydride of 1,2,4-benzenetricarboxylic acid 779
was added and reacted for about 8 hours, and the reaction was terminated when the acid value reached 22.

The obtained resin was a pale yellow solid, and the softening point of this resin was measured using "70-Tista CFT-500" (manufactured by Shimadzu Corporation) and was found to be 125°C.

Examples 1 to 4 and Comparative Examples (1) and (2) (Manufacture of toner) Based on the combination listed in Cloth-1 below, 100 parts by weight of the binder resin of the synthesis example and carbon black [Mogal L
After mixing 10 parts by weight of J (manufactured by Capot Co., Ltd.), 3 parts by weight of polypropylene (Viscol 660P, manufactured by Sanyo Chemical Industries, Ltd.), 1 part by weight of the sulfur-containing metal complex antioxidant according to the present invention, and 3 parts by weight of wax, 100-1 with two rollers
Thoroughly melt-knead at 30°C, then cool, coarsely pulverize with a hammer mill, further finely pulverize with a jet mill, and then classify, so that the particle size is within the range of 3 to 30 μm and the average particle size is 1000 μm. A sample toner was obtained. Note that the comparative toner did not contain any sulfur-containing metal complex antioxidant.

(Preparation of Developer) Developers were prepared by mixing 4 parts by weight of each of the sample toners and 96 parts by weight of a carrier (spherical ferrite particles rF-1504 manufactured by Nippon Tetsuko Co., Ltd.).

The developer obtained in Examples 1 to 4 was "developer l", respectively.
” to “Developer 4” and the developers obtained in Comparative Examples (1) and (2) as “Comparative Developers (1) and (2)”. Under the environmental conditions of
An electrophotographic copying machine R U-B 1x-5 formed by VJ (manufactured by Shin-Etsu Chemical Co., Ltd.) and equipped with a heat roller fixing device consisting of a backup lower roller and a cleaning device.
000J (manufactured by Konica Co., Ltd.) using the above-mentioned developer, a photocopy test was conducted in which copied images were continuously formed 100,000 times at a temperature of 33° C. and a relative humidity of 80%, and the following items were evaluated. did.

The results are shown in Table 2 below.

Table 2 <Characteristics measurement> (1) Fog Determined by measuring the relative density of the white area of the original with a density of 0.0 with respect to the copied image using a "Sakura densitometer" (manufactured by Konica Corporation) . Note that the white background reflection density is 0.0.
And so. In the evaluation, if the relative concentration is less than 0.01, it is evaluated as “○”.
'', and when it was 0.01 or more and less than 0.03, it was ``Δ'', and when it was 0.03 or more, it was rated ``x''.

(2) The solid black uniformity halftone dot analysis device "Sakura Area Adakku-100" manufactured by Konica Corporation was used to measure and determine the white ground area ratio in the copied image area corresponding to the black ground area of the original image.

"○" if the white area ratio is less than 5%, 5% or more 10%
The case where it was less than 10% was rated as "△", and the case where it was 10% or more was rated as "x".

(3) Toner scattering Visually observe the inside of the copying machine and the copied image, and if it is in good condition with almost no magnetic toner scattering, it is rated "O", and if the toner scattering is slightly comparable but at a practical level, it is rated "Δ". '', and cases where a lot of toner scattering was observed and there was a problem in practical use were rated "×".

(4) The back side of the copy paper after staining was visually observed, and those with significant stains were rated "x", those with slight stains were rated "Δ", and those with no stains observed were rated "O".

(5) Fixing roller dirt The determination was made by visually observing the heat roller constituting the fixing device. The evaluation is ``rx4'' when there is a lot of heat roller dirt and it is a practical problem, and ``△'' when the heat roller dirt is slightly comparable but at a practical level, and there is almost no heat roller dirt observed. The case was marked as “○”.

Note that the melting point in the present invention is measured using a normal melting point measuring device.

In addition, the softening point (Tsp) in the present invention is determined using a flow tester rCFT-500J (manufactured by Shimadzu Corporation), and the measurement conditions are: load 20, 9/CII"% nozzle diameter l1
Feng, nozzle length l w + m, preheated to 40°C 10
min, heating rate 6℃/+*in, sample amount 1 c
+m” (weight expressed as intrinsic specific gravity This is the temperature at 2.

In the present invention, the acid value refers to the number of milligrams of potassium hydroxide required to neutralize the acid contained in Sample 19.

Claims (2)

[Claims] (1) Non-linear polyester obtained from a monomer component containing a trivalent or higher polyvalent monomer, a plant-based natural wax and/or
Or, a toner for developing electrostatic latent images characterized by containing a montan-based ester wax and an antioxidant. (2) The toner for developing electrostatic latent images according to claim 1, wherein the antioxidant is a sulfur-containing metal complex compound.