JPS6348336B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to dry developers for direct and indirect electrophotography. In general, electrophotography is a method in which developer particles (toner) having a charge opposite to that of the triboelectrically charged latent image are attached to the electrostatic latent image by electrical attraction (Coulomb force) using static electricity (positive development). Alternatively, toner having the same charge as the latent image is deposited on the image-receiving sheet directly or indirectly by a method (reversal development) in which toner is deposited by an electric field between a magnetic brush and the recording surface, and then solvent vapor is applied to the toner particles. bring into contact. The recording is completed by fixing it by applying pressure, heating, etc.
Among these fixing methods, the heated roll fixing method involves direct contact between a heating element and toner particles, and can achieve high speed recording. On the other hand, due to the contact between the hot roll and the toner particles adhering to the image receiving sheet, the toner particles are not only fixed on the image receiving sheet but also adhere to the hot roll, contaminating the hot roll and transferring to the next image receiving sheet, which is called offset. Undesirable development occurs. Further, there is a problem in that the image receiving sheet is wound up on the roll due to the fusing force of the toner particles melted on the heated roll. For this reason, a method has been proposed in which the roll surface is formed of a material with good releasability, such as silicone rubber or fluorine-based resin, and a release agent such as silicone oil is further applied. However, since the release agent application method complicates maintenance of the fixing device and the device, it is desired to develop a toner with good offset resistance. The purpose of the present invention is to improve the offset properties of the above-mentioned hot roll fixing method as a dry type developer for electrophotography, and furthermore, it has good charging properties and maintains a stable charge amount even during use, so that clear and fog-free images can be obtained. The present invention provides toner for heat roll fixing. As a result of extensive studies, the present inventors found that the difference between the adhesive activation temperature and thermal melting temperature of the binder resin changes depending on the molecular weight, molecular weight distribution, crosslinked structure, etc. of the resin, and that We have found that the temperature difference is expanded, the temperature range between the fixing temperature and the offset temperature is expanded, and the offset properties are improved. The inventors have discovered that the resin can improve offset properties without impairing fixing properties, and have arrived at the present invention. That is, the present invention provides an electrophotographic dry developer containing a binder resin and a colorant as main components, in which the binder resin contains (a) a styrene monomer, and (b) a (meth)acrylic acid monomer. The present invention provides a dry developer for electrophotography, which is a copolymer of (c) an unsaturated polyester resin and contains 2 to 5% by weight of (c). The dibasic acid component used for producing the unsaturated polyester resin according to the present invention is at least one unsaturated dibasic acid such as maleic acid, maleic anhydride, fumaric acid, itaconic acid, and succinic acid. , succinic anhydride, adipic acid, phthalic anhydride, isophthalic acid, terephthalic acid, and the like can be used in an amount of 80 mol % or less in the dibasic acid component. Further, glycol components used for producing the unsaturated polyester resin according to the present invention include ethylene glycol, diethylene glycol, neopentyl glycol, polyethylene glycol, polypropylene glycol, 2,2-
Bis(4-cyclohexanol)propane, 4,
4-bis(2-hydroxyethoxyphenyl)-
One or more polyester-forming glycols such as 2,2-propane and 4,4-bis(2-hydroxypropoxyphenyl)-2,2-propane may be used. Furthermore, polybasic acids or polyhydric alcohols used in ordinary polyesterification reactions can also be used as part of the constituent components of the unsaturated polyester resin. The sum of carboxyl groups of these unsaturated polyester components is (A) and the sum of hydroxyl groups is
When (B) is used, (B) is used in an amount of 0.5 to 1.5 equivalents, preferably 0.8 to 1.2 equivalents relative to (A). The polyesterification reaction for producing the unsaturated polyester resin according to the present invention is carried out by heating and stirring the above-mentioned dibasic acid component and the above-mentioned glycol component at 150°C to 240°C for several hours under a stream of inert gas. At that time, if necessary, a small amount of silicone antifoaming agent and hydroquinone or paramethoxyphenol are added to inhibit the polymerization and oxidation of unsaturated dibasic acids. The reaction can be controlled and tracked using indicators such as acid value, softening point, and melt viscosity during the reaction. In this way, the unsaturated polyester resin used in the present invention can be produced. The binder resin according to the present invention is a partially crosslinked copolymer comprising (a) styrene, α-methylstyrene,
Styrenic monomers such as p-chlorostyrene and vinyltoluene, (b) acrylic acid monomers such as (b) acrylic acid, methacrylic acid, acrylic acid esters, and methacrylic acid esters, (c) unsaturation as mentioned above. Obtained using polyester resin as a copolymer component. Among the components constituting this binder resin, (c) unsaturated polyester resin provides a partially crosslinked structure, (b) styrene monomer forms the main skeleton of the resin, and (b) (meth)
The acrylic acid monomer becomes a component that controls the thermal properties such as the softening point of the resin, determines the charge, and controls the amount of charge. If the unsaturated polyester resin content in the copolymerization component is less than 2% by weight, the offset property, which is the objective of the present invention, cannot be improved;
If it exceeds this, fixing performance will decrease. The amount of (meth)acrylic acid monomer used varies greatly depending on the type of (meth)acrylic acid monomer, the desired thermal properties of the binder resin, etc., but it is usually around 5 to 70% by weight of the binder resin. is used. In addition, when only a normal (meth)acrylic acid alkyl ester is used as this component, a negatively charged binder resin is obtained, and a (meth)acrylic ester containing a tertiary amino group, such as dimethylaminoethyl-(meth) When using acrylate, a positively charged material can be obtained. The method for producing a binder resin by copolymerizing a styrene monomer and a (meth)acrylic acid monomer using the unsaturated polyester resin of the present invention as a crosslinking agent component is based on free radical, anion, and cation polymerization methods. This is carried out by a well-known addition polymerization reaction such as Next, the present invention will be explained with reference to Examples. All composition ratios shown in Examples are expressed in parts by weight. Example 1 242 parts of fumaric acid, 726 parts of 4,4-bis(2-hydroxypropoxyphenyl)-2,2-propane
parts, polyethylene glycol (average molecular weight 1000)
31 parts and 0.5 parts of hydroquinone in a nitrogen gas stream
React at 200℃ for about 7 hours to achieve acid value of 20 and softening point of 90℃.
(ring and ball method) unsaturated polyester resin was synthesized. Add xylene to a reactor equipped with a stirrer, nitrogen inlet, thermometer, reflux condenser and dropping funnel.
Prepare 300 parts and adjust the temperature to 80℃. 800 parts of styrene and n-butyl methacrylate under nitrogen stream
180 parts and α,α′-azobisisobutyronitrile
18 parts of the mixed solution was dropwise polymerized over 4 hours. Next, a mixture of 20 parts of the unsaturated polyester resin, 20 parts of xylene, and 2 parts of α,α'-azobisisobutyronitrile was dropwise polymerized over a period of 2 hours. After dripping
The mixture was heated to 120°C and aged for 4 hours, and after completion of polymerization, it was cooled, reprecipitated in alcohol, and dried to obtain a resin powder. Example 2 Using the same reactor as in Example 1 above, 400 parts of α-methylstyrene was poured into 300 parts of xylene at 80°C under a nitrogen stream.
parts, vinyltoluene 225 parts, n-butyl methacrylate 280 parts, dimethylaminoethyl methacrylate
75 parts and α, α′-azobisisobutyronitrile 18
of the mixture was added dropwise over 4 hours, and then Example 1
20 parts of the unsaturated polyester resin listed and 20 parts of xylene
A mixture of 1 part and 2 parts of α,α'-azobisisobutyronitrile was added dropwise over 2 hours to polymerize. After the dropwise addition was completed, the temperature was raised to 120°C, and an aging reaction was carried out for 4 hours. After cooling, the mixture was reprecipitated in alcohol and dried to obtain a resin. Example 3 100 parts of fumaric acid, 120 parts of succinic acid, 20 parts of neopentyl glycol, 580 parts of 4,4-bis(2-hydroxypropoxyphenyl)-2,2-propane, and 0.4 parts of paramethoxyphenol were mixed in a nitrogen gas stream. React at 200℃ for about 10 hours with acid value of 15 and softening point of 105.
C. (ring and ball method) unsaturated polyester resin was obtained. Using the reactor of Example 1 above, 450 parts of vinyltoluene and 400 parts of styrene were added to 300 parts of xylene at 80°C.
100 parts of n-butyl acrylate and 18 parts of benzoyl peroxide were added dropwise over 4 hours, and then 20 parts of the unsaturated polyester resin, 20 parts of xylene, and 2 parts of benzoyl peroxide were added dropwise over 2 hours.
The temperature was further raised to 120℃, and after aging for 4 hours, the pressure was reduced to 100mmHg, and the temperature was gradually raised to 200℃, while xylene was distilled off. The molten resin was taken out into a stainless steel vat, left to cool, and crushed to form a powdered resin. Obtained. Example 4 Using the reactor of Example 1 above, xylene at 80°C
700 parts of styrene in 300 parts, n-butyl acrylate
After dropping a mixture of 225 parts of diethylaminoethyl methacrylate, 30 parts of α,α'-azobisisobutyronitrile and 18 parts of α,α′-azobisisobutyronitrile over 4 hours, 45 parts of the unsaturated polyester resin described in Example 3, 50 parts of xylene, and α,α A mixture of 2 parts of '-azobisisobutyronitrile was added dropwise over 2 hours, and after the addition, the temperature was raised to 120°C and aged for 4 hours. Next, the pressure was reduced to 100 mmHg and the temperature was gradually raised to 200° C. while xylene was distilled off, and the molten resin was taken out into a stainless steel vat, left to cool, and crushed to obtain a powdered resin. Comparative Example 1 Using the reactor of Example 1, 850 parts of styrene and n-butyl methacrylate were added to 300 parts of xylene at 80°C.
A mixed solution of 150 parts of benzoyl peroxide and 20 parts of benzoyl peroxide was added dropwise over 4 hours, and then the temperature was raised to 120°C and aged for 4 hours.
Thereafter, xylene was distilled off and pulverized by the method of Example 3 to obtain a powdered resin. Comparative Example 2 85 parts of the resin of Comparative Example 1 and 15 parts of the unsaturated polyester resin described in Example 1 were melt-mixed at 160°C to 170°C, cooled and pulverized to obtain a powdered resin. Comparative Example 3 Using the reactor of Example 1, 850 parts of styrene and 140 parts of n-butyl acrylate were added to 300 parts of xylene at 80°C.
parts, 10 parts of divinylbenzene and benzoyl peroxide
20 parts of the mixed solution was added dropwise over 4 hours, and after aging at 120°C for 4 hours, it was reprecipitated in alcohol and dried to obtain a powdered resin. Comparative Example 4 Using the reactor of Example 1, 60 parts of styrene, 35 parts of n-butyl methacrylate, A mixed solution of 5 parts of dimethylaminoethyl methacrylate and 2 parts of α,α'-azobisisobutyronitrile was added dropwise over 2 hours, followed by an aging reaction at 90°C for 5 hours to complete the polymerization, and after cooling, it was filtered and dried to form a powder. A resin was obtained. Examples 95 parts of the resin synthesized in Examples and Comparative Examples and 5 parts of carbon black were mixed in a ball mill, then melted and kneaded using hot rolls, cooled and solidified, coarsely ground in a hammer mill, and finely ground in a jet mill. The particles were pulverized and used as toner except those with particle diameters of 5 μm or less and 20 μm or more. Five grams of this toner was mixed with 95 parts of iron powder of 150 to 200 meshes, and the toner was evaluated using a commercially available developing machine and printer using a magnetic brush method and a hot roll fixing method. The results shown in Table 1 were obtained, and it was found that the toner using the binder resin of the present invention had good image forming properties and offset resistance.

【table】

[Table] *1 Ring and ball method *2 Blow-off method (electrophotography VoL16, No.2,
10 (1978))

Claims (1)

[Claims] 1. In an electrophotographic dry developer whose main components are a filler resin and a colorant, the binder resin comprises (a) a styrene monomer, (b) a (meth)acrylic acid monomer, (3) A dry developer for electrophotography, which is a copolymer of an unsaturated polyester resin and contains 2 to 5% by weight of (3).