JPS61223849A - Positively triboelectrifiable toner - Google Patents

Abstract

PURPOSE:To obtain a positively triboelectrifiable toner good in high-speed fixability by using a heat roll fixing system and a toner binder resin contg. a polyester resin, a lactone modified epoxy resin. CONSTITUTION:The positively triboelectrifiable toner contains the binder resin, a colorant, and a triboelectrification controller, and the binder resin contains a (5-75):(95-25) weight ratio mixture of polyester resin and lactone modified epoxy resin having a softening point of 90-130 deg.C, thus permitting the obtained toner to be positively triboelectrifiable and improved in fixability and offset resistance, and not detriorated in storage stability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an electrophotographic developer, and particularly to a positively charged toner having good high-speed fixing properties using a heat roll fixing method.

[Background of the invention]

Conventionally, in electrophotography, an electrostatic latent image is formed on a photoreceptor such as selenium, lenium, zinc oxide, or an organic photoconductor, and the electrostatic latent image is insulated with a carrier such as a glass ball, iron powder, or ferrite powder. The toner is mixed with a colored fine powder toner, and the toner is triboelectrically charged and brought into contact with a developer to perform electrostatic development. Then, a method is adopted in which this is directly recorded or the toner is transferred by stacking transfer sheets and applying an electric field.

In the above-mentioned direct recording method, the electrostatic latent image formed on photosensitive paper or electrostatic recording paper is developed and then fixed directly, which eliminates the need for a master photoreceptor or a transfer process, making it possible to downsize Seiko's photographic equipment. However, it also has the disadvantage that it requires specially treated recording paper. On the other hand, in the plain paper copy (hereinafter abbreviated as PPC) method, an electrostatic latent image is visualized with toner on a master photoreceptor such as selenium, zinc oxide, or an organic photoconductor and is transferred to plain paper, etc. This method is used in printers, transfer machines, printers, facsimile machines, etc.

In the PPC method, it is necessary to fix the transferred toner on the paper, and the fixing methods include pressure fixing using only a pressure roll at room temperature, heat fixing using open heating, flash fixing using a halogen lamp, etc., and thermocompression fixing using a heat roll. etc. Among these, pressure fixing has the advantage that it consumes less power and can be started quickly, but has the disadvantage that absolute fixing performance is weak. In contrast, heat roll fixing has the advantage of good fixing properties and is effective even in high-speed fixing.

In heat roll fixing, as the toner comes into pressure contact with the heat roll surface in a heated and molten state, some of the toner adheres to the roll surface and then re-adheres to the paper, which tends to cause an offset phenomenon that stains the paper. It is necessary to prevent this as much as possible.

Heat roll fixing methods include, for example, a type that uses silicone rubber or fluororesin with good mold release properties and coats the heat roll with a release agent such as silicone oil. There is a type that uses pre-impregnated silicone rubber as a heat roll. These devices require an accessory device for supplying silicone oil, and if the supply of silicone oil stops, an offset occurs, resulting in poor reliability. Therefore, recently, a device in which a metal roll is thinly coated with a fluororesin has been developed, and a system is being used in which a small amount of silicone oil is supplied or no silicone oil is supplied at all.

On the other hand, various methods have been proposed from the viewpoint of material composition to prevent toner offset. For example, a method of using a specific toner fixing resin and increasing its molecular weight distribution (Japanese Patent Publication No. 55-6895);
A method of preventing toner from adhering to the heat roll by mixing a specific fixing resin with a liquid or solid resin having release properties (Japanese Patent Publication No. 53-15655, No. 53-21655)
No. 53-23084, No. 53-25496, No. 53-25653, No. 53-25654, No. 53-
25655), etc.

Traditionally, vinyl copolymers containing cysteine monomers have been often used as fixing resins for Mat1 toners, but in recent years, polyester resins with good properties have been developed, and conventional styrene copolymers have been used. A toner with better fixing properties and anti-offset properties was obtained.

These are Special Publication No. 52-22996 and No. 52-254.
Starting from a linear polyester resin synthesized from a diol component and a dicarboxylic acid component as described in various publications such as No. 20 and No. 58-42462, it was initially used for oven fixing, but it was also used for electronic copying using a heat roll fixing method. With the spread of devices, non-linear polyester resins produced from dicarboxylic acids and diols, including polyols or polycarboxylic acids, with good fixing properties and offset resistance in heat roll fixing, have been developed.

Examples of polyols, polycarboxylic acids, diols and dicarboxylic acids for producing this non-linear polyester resin include JP-A-56-1952, JP-A-58-11955, JP-A-58-100139, and JP-A-59-11902. For example, there are the following.

Examples of polyols include pentaerythritol, dipentaerythritol, tripentaerythritol, sorbitol, glycerol, 1. 2. 4-butanetriol, 1,2,5-pentanetriol, 2-methylpropanetriol, 1,3゜5-trihydroxymethylbenzene, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylol Propane, 1.
2. 3゜6-hexantetrol, 1,4-sorbitan, glucose, lactose sucrose, polyoxyethylene (10) sorbitol, polyoxyethylene (4) 1
．． 4-sorbitan, polyoxyethylene (30) pentaerythritol, polyoxypropylene (5) 1,2,
There are compounds containing approximately 3 to 9 hydroxyl groups, such as 3,5,6-hexanehentol, but alkoxylated polyols are particularly preferred.

As polycarboxylic acids, 1. 2. 5-hexanetricarboxylic acid, 1. 2. 4-butanetricarboxylic acid, tetra(methylenecarboxyl)methane, 1, 2.
7. 8-octanetetracarboxylic acid, l.

2.4-benzenetricarboxylic acid, 1,2.5-benzenetricarboxylic acid, 1. 2. 4-cyclohexanetricarboxylic acid, 1. 2. 4-naphtha V/tricarboxylic acid, 2,5.7-naphthalene tricarboxylic acid, 1,3
-dicarboxyl-2-methichu-2-methylenecarboxypropane, 1. 2. There are compounds having approximately 3 to 8 carboxyl groups, such as 7°8-octane tetracarboxylic acid and embol triple acid.

Examples of diols include ethylene glycol, propinone glycol, tetramethinone glycol, 1,4-butynone diol, pentamethinone glycol, butane diol, neopentyl glycol, phtendiol diethylene glycol, p-di(hydroxymethyl)benzene,
2,2-bis(4-hydroxyphenyl) furonokun,
Bis(4-hydroxyphenyl)methane, bis(4-hydroxyphenyl)ketone, bis(4-hydroxyphenyl)ether, his(hydroxyphenyl)sulfone, 2,2-bis(2,3,5,6-tetrapromo) 4-
Hydroxyphenyl)butane, bisphenol A1 Hydrogenated bisphenol A1 Bo)lyoxyethylated bisphenol A1 Polyoxypropylated bisphenol A
etc., but bisphenols are preferred, and etherified bisphenols are particularly preferred.

Furthermore, dicarboxylic acids include fumaric acid, maninic acid,
Succinic acid, itaconic acid, phthalic acid, malonic acid, cyclohexanedicarboxylic acid, mesaconic acid, citraconic acid, glutaconic acid, isophthalic acid, terephthalic acid, adipic acid, heptano(tinic acid and their acid anhydrides, lower alkyl Examples include a dimer of ester and lino-Vinic acid, and other divalent organic acid monomers, but among these, fumaric acid, isophthalic acid, and -°maleic acid are preferred.

If these are used and a carboxylic acid and a hydroxy compound are polycondensed by a known method, a non-linear polyester resin having good fixing properties and offset resistance can be obtained. In particular, a suitable resin is obtained when etherified bisphenols are used as the diol component, and is moderately crosslinked with polyol or polycarboxylic acid.Nineth, it has strong mechanical strength and excellent next developability, and also has low It is possible to obtain a toner that has a fixing point and has little offset to the fixing roll. Therefore, toners using these polyester resins are suitable for high-speed fixing and have come to be used in high-speed electrophotographic copying machines. However, polyester resins generally have unreacted carboxyl residues and exhibit electron-withdrawing properties, and exhibit strong negative triboelectrification when triboelectrified with ordinary carriers. Ninthly, negatively charged toners are easily available, such as a regular development method using a positively charged selenium photoreceptor, or a reversal development method using a negatively charged zinc oxide or organic photoreceptor. However, it is suitable for reversal development using a positively charged 7V photoreceptor, or
It is difficult to apply to regular development methods that use negatively charged zinc oxide or organic photoreceptors.

[Purpose of the invention]

In view of the above circumstances, the present invention provides that, when a non-linear polyester resin is used, it can be inverted with respect to a positively charged selenium photoconductor, or a negatively charged symbiotic zinc or organic photoconductor, respectively. It also has excellent regular developability, is particularly suitable for fixing using the heat roll method, and has good high-speed fixing properties.
Another object of the present invention is to provide a toner composition of type 1 toner composition with excellent storage stability and extremely little offset phenomenon.

[Summary of the invention]

The positively charged toner of the present invention includes a binder resin, a colorant, and a charge control agent, wherein the binder resin contains a polyester resin and a lactone-modified epoxy resin. Its characteristics are that the lactone is ε-caprolactone, and that the polyester resin is produced from dicarboxylic acids and diols, including polyols or polycarboxylic acids, but preferably polyester resins and lactone-modified The blending ratio of epoxy resin is 5 to 75% by weight of polyester resin.
, a lactone-modified epoxy resin of 95 to 25 weights is suitable.

The purpose of the present invention is to provide a toner with excellent positive chargeability even when a polyester resin with strong negative triboelectricity is used. Reversal from negative to positive is not sufficient, and it is necessary to further add a resin having positive triboelectric charging properties. As such a resin, a resin containing an electron-donating polar functional group is considered, and alkylamino group-containing acrylic copolymers (% Open and Close No. 48-102633, No. 54-1
Publications such as No. 24731 and No. 54-143647),
Nitrogen-containing heterocyclic vinyl copolymer (JP-A-54-13342
No. 54-89640) have been proposed, but these resins have problems with moisture resistance! 11゜It has not been put into practical use. In addition, amide waxes used as mold release agents are resins with strong positive triboelectric charging properties, but when added to toners, they reduce printing durability on photoreceptors and promote offset during heat roll fixing. .

Therefore, in the present invention, as a result of examining various resins having positive triboelectric charging properties other than those mentioned above, we found that a lactone-modified epoxy resin produced from the reaction of C-caprolactone and a bisphenol type epoxy resin is the most effective in positively charging toner. This is because the resin has excellent insulation and moisture resistance, and also has good heat resistance, so it is less susceptible to deterioration due to heating during toner production and has a stable positive charge. It is considered that the The method for producing this lactone-modified epoxy resin is proposed, for example, in JP-A-59-56422, and is obtained by addition polymerizing ε-capro2 lactone to the secondary hydroxyl group of a bisphenol-type epoxy resin. Lactone-modified epoxy resins having various melt properties can be obtained depending on the molecular weight of the bisphenol-type epoxy resin and the degree of addition polymerization of ε-caprolactone. Generally, the lower the molecular weight of the epoxy resin, the lower the softening point, and the more addition polymerization of ε-caprolactone, the lower the softening point. The rate of addition polymerization of ε-caprolactone is usually determined using bisphenol-type epoxy resin 97
~70 parts by weight, 3 to 30 parts by weight of e-caprolactone, less than 3 parts by weight of ε-caprolactone is less effective in imparting positive charge, and conversely, if it exceeds 30 parts by weight, the softening point becomes low. There is a problem.

The above-mentioned lactone-modified epoxy resin is required to have melt properties within a specific range in order to improve toner storage stability, fixing properties during heat roll fixing, and offset resistance. The present inventors investigated the softening point as a melt property of the lactone-modified epoxy resin, and found that if the softening point is in the range of 90 to 130 t:' (ring and ball method), when added to the above polyester resin, It has been found that the toner is positively charged and has good fixing properties and anti-offset properties, and does not deteriorate the storage stability of the toner (the property that the toner does not cause blocking phenomenon during storage or in the developing box).

Through the above studies, the resin that is the main subject of the present invention can be obtained, but in particular, as a toner for heat roll fixing, it is necessary to maintain fixing properties and Since good anti-offset properties are required, it is possible to add a commonly used anti-offset agent if necessary. Examples of anti-offset agents include polyolefins, fatty acid metal salts, fatty acid esters, partially silicified fatty acid esters, higher fatty acids, higher alcohols, paraffin wax,
Examples include polyhydric alcohol esters, but low molecular weight polypropylene and polyethylene wax having a molecular weight of 50,000 or less are particularly effective.

When preparing a toner by blending each of the above resins, it is necessary to take into consideration the temperature, pressure, etc. during heat roll fixing, and in normal cases, the melt viscosity of the toner at 1601:' is in the range of 100 to to, ooo If the resin composition is selected to produce voids, a toner with good fixing properties and excellent anti-offset properties can be obtained.

The blending ratio of polyester resin and lactone-modified epoxy resin in the present invention is 5 to 75% by weight of polyester resin.
, a range of 95 to 25% by weight of the lactone-modified epoxy resin is suitable. If the amount of polyester resin blended is less than 5 times, the fixing properties and offset resistance of the toner will decrease, and the
This is because if the toner exceeds 75 t, the negative triboelectricity of the toner increases, and even if a charge control agent is added, it becomes difficult to control the toner charge positively.

As mentioned above, an anti-offset agent is added to the toner of the present invention as necessary, and the anti-offset agent melts at a temperature lower than the softening point of the binder of the toner and is a releasing substance having low surface energy. It is used, but the ratio to the binder is usually 0.5 to 20 weight! -H, preferably 1 to tot@H.

The toner of the present invention contains a colorant, a positive charge control agent, and an anti-offset agent in the above-mentioned binder, and further contains a property improver added as necessary, and when it is made into a magnetic toner, , a magnetic material is contained together with a coloring agent or in place of a coloring agent.

Coloring agents include carbon black, Ani IJ y blue, calco oil blue, chrome yellow, ultramarine blue, Teyubon oil red, quinoline yellow, methinon blue chloride, phthalocyanine blue,
Mention may be made of malachite green oxa V-t, lamp black, rose bengal and the like. These colorants need to be contained in a sufficient proportion to form a visible image of sufficient strength, and are usually added in an amount of 1 to 20% by weight based on the total amount of the toner.

Examples of the magnetic material include alloys or compounds containing ferromagnetic elements such as iron, cobalt, and nickel, including 7-elite and magnetite, and various alloys that exhibit ferromagnetism through some kind of treatment such as geothermal treatment. is used. Let's take a concrete example.

Examples include magnetite (Fesoa), Co-added magnetite, spinel type ferrite, magnet brambite type 7-elite, and the like. These magnetic substances are uniformly dispersed in the binder in the form of fine powder with an average particle size of 0.3 to 1 micron. The smaller the amount of these magnetic powders added, the better from the viewpoint of fixing properties, but when used as a magnetic toner, if the magnetic powder is less responsible, the toner conveying force by the magnetic roll will decrease, and the toner will not scatter. Problems occur, and an offset phenomenon during fixing is also likely to occur. Therefore, 40 to 60% by weight based on the total amount of toner.
A range of is appropriate.

, Nigrosine dye is the most widely used positive charge control agent. Nigrosine dye is described in the “Dye Handbook” (
C, I, Solvent described on page 875 (edited by the Organic Synthetic Chemistry Association, published by Maruzen Co., Ltd.).

Black 5 (C, 1, 5olvent Black
5) and Sea, Eye, Solvent, Black 7 (C0
I.

5olvent Black 7).

Based on these nigeron dyes, reactants with aliphatic basic acids and/or dibasic acids, and reactants of nigeron dyes with carboxyl group-containing resins have been developed, and these dyes can be dispersed in toner resins. Because of its favorable properties, it is particularly effective in stabilizing charge. The amount of these nigrosine dyes added is 1 to 10% by weight based on the total amount of toner.
A range of is appropriate. When the number of grooves is 1, the charge control effect is small, and when the number exceeds 10, the fluidity and aggregation resistance of the toner are reduced, resulting in poor image quality. As positive charge control agents other than nigrosine dyes, triphenylmethane dyes, piperazine polymers, etc. can be effectively used.

The toner of the present invention can be reversed, for example, in the following manner. A coloring agent and a positive charge control agent are premixed using a mixer such as a ball mill or a super mixer, and then a polyester resin, a lactone-modified epoxy resin, and a low molecular weight polypropylene are added and premixed. Then, the mixture is melt-mixed using a kneading machine such as a two-roll or kneader, cooled and solidified after death, and then pulverized using a jet mill and classified using a zigzag classifier to obtain a toner having an average particle diameter of 3 to 44 μm.

If the average particle diameter is less than 3 .mu.m, the image will be often fogged, and if it exceeds 44 .mu.m, the image will be rough, so it is preferably in the range of 3 to 44 .mu.m, preferably in the range of 5 to 30 .mu.m.

In order to improve the fluidity, image properties, and printing durability of the toner on the photoreceptor, it is effective to add a small amount of hydrophobic silica fine powder to the outside of the toner as a property improver. The appropriate amount of addition is in the range of 0.05 to 3% by weight based on the total amount of toner; if it is less than the above range, there is no effect of addition, and if it is more than the above range, the positive chargeability of the toner will be reduced. It becomes unstable and the image characteristics deteriorate.

Evaluation of the fixing properties and anti-offset properties of the toner of the present invention was conducted using a metal heat roll coated with fluororesin and R
The toner image was heated using a TV silicone rubber roller and fixed by passing the toner image between the two, and then evaluated by a cellophane tape peeling test and visual observation.

[Embodiments of the invention]

Hereinafter, the present invention will be specifically explained with reference to Examples.

Example 1 Softening point (ring and ball method) is 120C, acid value is 20KOHmg/
40 parts by weight of non-linear type bisphenol polyester resin (manufactured by Kao Seiken, KTR2150), lactone-modified epoxy resin with a softening point (ring and ball method) of 119C (manufactured by Daicel Chemical, Plaxe A/G 701 A% 7 ct) 85 parts by weight of a binder resin consisting of 2 parts by weight of polypropylene with a molecular weight of 8600 (Viscol 660F, manufactured by Sanyo Kasei), oleic acid-modified nigrosine dye (Orient Chemical Exhibition, Bontron 43)
5 parts by weight and carbon black (manufactured by Mitsubishi Kasei, Na44)
Using 10 parts by weight, a toner with a particle size of 5 to 30 μm was produced.

The above toner has 3 parts by weight, a volume resistivity of 109 Ω・α, an apparent density of 4.46 g/crr&'', and a particle size of 74 to 17
9. A developer is made from a 7 μm, almost perfectly spherical iron oxide powder carrier with 100 heavy electric parts. Neutral zone for toner carrier
ltt using the blow-off method (manufactured by Toshiba Chemical, TB-200)
) (e-CdV-
Information is written on the paper, and this is reversely developed using the magnetic brush method using the above-mentioned developer. The toner image was then transferred to continuous paper and fixed using a pressure/heat roll fixing device equipped with a preheating device. As a result, a good image with high image density and no fog or offset was obtained, and it exhibited good fixing properties. Next, while replenishing toner,
When development, transfer and fixing were repeated for 0 hours, good images were continuously obtained from beginning to end.

There was no toner scattering from the developing device, capri, or offset, and no deterioration in fixing performance occurred.

Example 2 Softening point (ring and ball method) is 1410. Acid value is 15.5KOHm
5 to 75 parts by weight of non-linear type bisphenol polyester resin (manufactured by Kao Seiken, KTR2120), lactone-modified epoxy resin with a softening point (ring and ball method) of 123C (Daicel Chemical, Plaxel G701T, lactone-modified 10 (% by weight) 95 to 25 parts by weight, 2 parts by weight of the same polypropylene V as in Example 1 as a binder resin, 5 parts by weight of stearic acid-modified nigrosine dye (Orient Kagakuten, Bontron A2), and the same carbon as in Example 1. Various toners with a particle size of 5 to 30 μm were prepared using 10 parts by weight of black, and toner 3 was prepared using the same carrier as in Example 1.
A developer was obtained from 100 parts by weight of carrier. Using this developer, the amount of charge, offset resistance, and fixing properties of the developer using each toner were investigated using the same apparatus as in Example 1. The results are shown in Table 1.

In this way, as the addition ratio of lactone-modified epoxy resin increases, the amount of positive triboelectric charge increases, but on the contrary, the offset resistance and fixing properties of KTR-2120, 5
Weight part, Praxel G701T.

It was found that at a blending ratio of 95 parts by weight, it became slightly worse.

Comparative Example A toner was prepared in the same manner as in Example 1, except that the lactone-modified epoxy resin was replaced with a bisphenol-type epoxy resin (Shell Chemical Co., Ltd., Ebicor 1007). . A developer was prepared from 3 parts by weight of this toner and 100 parts by weight of the same carrier as in Example 1. As a result, the amount of frictional charging of the toner against the carrier decreased to +5 μC/g, and the positively charged 7V photosensitive It was found that a good image could not be obtained in reverse development with respect to the body.

〔Effect of the invention〕

According to the present invention, the disadvantage of polyester resin, which is that it is difficult to be positively charged, is improved without impairing the fixing ability, which is an advantage of polyester resin, and a toner with a good balance of cleanliness, offset resistance, fixing ability, etc. can be provided.

Claims (1)

[Scope of Claims] 1. A positively charged toner containing a binder resin, a colorant, and a charge control agent, wherein the binder resin contains a polyester resin and a lactone-modified epoxy resin. 2. The positively charged toner according to claim 1, wherein the lactone is ε-caprolactone. 3. Claim 1 or 2, wherein the polyester resin is produced from a dicarboxylic acid containing a polyol or a polycarboxylic acid, and a diol.
Positively charged toner as described in section. 4. Claims 1 and 2, characterized in that the blending ratio of the polyester resin and the lactone-modified epoxy resin is 5 to 75% by weight of the polyester resin and 95 to 25% by weight of the lactone-modified epoxy resin. Or the positively charged toner described in item 3.