JPH0149940B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an encapsulated toner for pressure fixing used in electrophotographic development. Conventionally, heat-fixing toner has been widely used as toner for electrophotography, but the heat-fixing method using it requires high heat to melt the toner.
In addition to consuming a large amount of power, it also takes a long time to fix. Furthermore, it has various drawbacks, such as the need to rapidly cool the toner after it is melted and fixed. In recent years, there has been a demand for energy-saving electrophotographic devices and high-speed electrophotography, and pressure fixing methods are being considered as an alternative to heat fixing methods, but the properties of pressure fixing toners are insufficient and the fixing performance is poor. Currently, it is not widely used because it is inferior to the heat fixing method. The pressure fixing method is an energy-saving method that does not require a heat source, but there are various drawbacks to the pressure toners currently being considered, such as the need for high pressure during fixing and the toner agglomerating or changing its characteristics during storage. There is. In particular, the disadvantage of requiring high pressure is that paper with high mechanical strength may cause wrinkles and tears, and the type of paper must be selected, which limits its use. Ru. Furthermore, in devices that use continuous paper such as roll paper, problems such as paper jams and tears may occur due to the slight distortion that occurs during pressurization, and this drawback becomes a major problem especially when operating at high speeds. There is. The inventors of the present invention have conducted extensive research to improve the triboelectric charging characteristics of toner while simultaneously improving the drawbacks. As a result, a specific vinylidene fluoride copolymer has excellent triboelectric charging properties as a shell material for pressure fixing toners. It also has a low glass transition temperature and is therefore susceptible to deformation and destruction at low pressures, and a high melting temperature that prevents agglomeration during use and storage. They found that they can be maintained in a smooth state without forming, and that they can be easily encapsulated because they can be dissolved in a solvent, leading to the completion of the present invention. The vinylidene fluoride copolymer used in the present invention has the general formula (): CXX'=CYY' () (wherein, X, X', Y, Y ′ are the same or different and are hydrogen or fluorine) (excluding vinylidene fluoride), or the general formula (): CXX′=CYZ () where X, X' and Y are the same as above, Z is an alkyl group having 1 to 10 carbon atoms, a fluoroalkyl group, an alkyl ester, a fluoroalkyl ester group, an alkyl ether group, a fluoroalkyl ether group, a phenyl group, or a chlorine atom) Examples include copolymers with the monomers () shown below. Examples of these copolymers include vinylidene fluoride and vinyl fluoride, chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene, trifluoroethylene, perfluorovinyl ether having an alkyl group having 10 or less carbon atoms, and chlorofluoroethylene. Vinylidene, 3,
3,3-trifluoro-2-trifluoromethylpropylene, pentafluoropropylene, perfluoroacrylate or perfluoromethacrylate having an alkyl group or fluoroalkyl group having 10 or less carbon atoms, fluoroalkyl group having 10 or less carbon atoms Acrylates, methacrylates, vinyl compounds or allyl compounds, fluorine-based monomers such as perfluorostyrene; Olefins such as ethylene, propylene, butylene;
Halogenated olefins that do not contain fluorine atoms such as vinyl chloride and vinylidene chloride; Acrylates or methacrylates having an alkyl group having 10 or less carbon atoms; Vinyl ether compounds; Vinyl acetate; One or more monomers such as styrene, etc. Examples include copolymers of The above vinylidene fluoride copolymer is produced by emulsion polymerization method,
It can be produced by either a solution polymerization method or a suspension polymerization method. Generally 1~50Kg/ ^cm2
The polymer is produced in high yield under pressure of G in the presence of a polymerization initiator, usually a peroxide such as diallyl peroxide, peroxide ester, peracid fluoro compound or persulfate, such as ammonium persulfate or potassium persulfate. It can be grown. The shell material used in encapsulated toner for low-pressure fixing must be able to transform and break at low pressure;
Therefore, it is necessary to adjust the compressive strength and tenacity of the vinylidene fluoride copolymer used in the present invention as appropriate to meet these objectives. The main factor that determines these properties is the molecular weight; if the molecular weight is too large, the compressive strength will be high and it will become especially sticky, so the shell will not break under low pressure and will cause poor fixation. On the other hand, if the molecular weight is too small, the compressive strength and tenacity will decrease, causing damage during handling due to friction with the carrier, causing fogging and bead pricking. The desirable molecular weight of the vinylidene fluoride copolymer is that the intrinsic viscosity [η] is 0.1 to 2.5, preferably
It is in the range of 0.2 to 1.5. The intrinsic viscosity [η] shown here is widely used as a guideline for molecular weight, and the above value is based on a solution obtained by dissolving vinylidene fluoride copolymer in N,N'-dimethylacetamide. 35℃ using Uberose viscometer
It was measured at Furthermore, the glass transition temperature of the vinylidene fluoride copolymer used in the present invention is generally -40°C or lower,
Melting temperature is 100-170°C. The vinylidene fluoride copolymer preferably has 60 mol % or more of vinylidene fluoride as its constituent unit. When the vinylidene fluoride content is less than 60%, rubber elasticity and strength tend to decrease in many cases, and fluidity and abrasion resistance also tend to decrease.
Furthermore, if the proportion of vinylidene fluoride becomes too large, the crystallinity of the generally obtained copolymer becomes high, and as a result, there is a tendency that even higher pressure is required for fixing. Therefore, the composition range of the vinylidene fluoride copolymer used in the present invention is such that the monomer copolymerized with vinylidene fluoride is a monomer represented by the general formula () (excluding vinylidene fluoride). For example, in the case of ethylene, vinyl fluoride, trifluoroethylene, tetrafluoroethylene, etc., the molar ratio of vinylidene fluoride to the monomer is 95 to
60: ranges from 5 to 40. If the proportion of vinylidene fluoride is larger than this range, high pressure will be required for fixing, while if the proportion of vinylidene fluoride is smaller than this range, a decrease in strength will occur, which is generally not a desirable tendency. Furthermore, the monomer copolymerized with vinylidene fluoride is a monomer represented by the general formula (), such as propylene, butylene, hexafluoropropylene, pentafluoropropylene, chlorotrifluoropropylene, 3,3,3-trifluoro- In the case of 2-trifluoromethylpropylene, perfluoroalkyl vinyl ether, perfluoroalkyl acrylate, perfluoroalkyl methacrylate, allyl acrylate, perfluorostyrene, alkyl vinyl ether, vinyl acetate, styrene, etc., vinylidene fluoride: the monomer The molar ratio is in the range of 99-80:1-20. The proportion of vinylidene fluoride exhibits rubber elasticity lower than this range, which tends to be generally unfavorable. When using both monomers of the general formula () and (), the monomer of the general formula () is usually used in an amount of 1/3 or less (molar ratio) to the monomer group of the general formula (). It is preferable to copolymerize in proportion. The vinylidene fluoride copolymer described in detail above is usually used as a shell material for encapsulated toner for pressure fixing, but it may also be used in the form of a core material dispersed and included in the shell material of the present invention. As the core material, any adhesive rubber-like or soft resin-like material having a glass transition temperature of usually 50°C or lower, preferably 30°C or lower can be used. Specific examples include rosin ester, modified rosin ester, alkyl polyester, urethane polyester, acrylic polyester, epoxy acrylate, urethane acrylate, polyether acrylate, melamine acrylate, alkylated acrylate, acrylic styrene copolymer, and vinyl ether maleic anhydride copolymer. Polymers, urethane elastomers, vinyl acetate acrylic copolymers, vinyl acetate styrene copolymers, vinyl acetate vinyl chloride copolymers, butadiene styrene copolymers, polyisobutylene rubber, coumaron indene resins, polyterpene resins, etc. However, it is not limited to these. If the vinylidene fluoride copolymer used as the shell material is to have properties other than triboelectric properties, such as lubricity and abrasion resistance, the amount should be 1 to 20% by weight.
lubricants such as low molecular weight polytetrafluoroethylene, low molecular weight polyethylene, solid lubricants that do not impair triboelectric properties such as mica powder, talc, and graphite fluoride, and wear resistance improvers such as finely powdered silica. May be used. Both pigment-based colorants and dye-based colorants can be used as colorants, and they may be included in either the core material or the shell material, but when primarily included in the core material, the coloring density can be increased without impairing the triboelectric properties. Can be adjusted. The appropriate amount is 1 to 20% by weight based on the core material and shell material. Specific examples of colorants used include carbon black,
Examples include, but are not limited to, cobalt blue, oil blue, quinoline yellow, phthalocyanine blue, phthalocyanine yellow, aniline blue, and oil red. The encapsulated toner for pressure fixing can be produced by, for example, a spray drying method, an electrostatic coalescence method, etc., and is prepared into encapsulated spherical particles having a particle size of 1 to 50 μm. The blending ratio of the shell material and the core material varies depending on the compressive strength, tenacity, and particle size of the vinylidene fluoride copolymer, and the weight ratio of the shell material to the core material ranges from 1:10 to 1:10.
The ratio is selected within the range of 10:1, but those with less shell material are usually used. Next, the present invention will be explained with reference to Examples and Comparative Examples, but the present invention is not limited only to these Examples. Example 1 1.5 ion-exchanged water and 1 g of perfluorooctaniac acid ammonium salt were charged into a stainless steel autoclave with an internal volume of 3, the autoclave was sealed, and the autoclave was replaced with nitrogen gas. molar ratio)
After charging a mixed gas ^of
g was added to initiate polymerization. After the start of polymerization, the pressure decreased, but the pressure was maintained at 8 Kg/cm ² G by adding a mixed gas of vinylidene fluoride and hexafluoropropylene at a molar ratio of 90:10. A KCl aqueous solution was added to the obtained polymer emulsion for salting out to obtain 300 g of vinylidene fluoride-hexafluoropropylene copolymer. The obtained copolymer is
It contained 10 mol% hexafluoropropylene and had an intrinsic viscosity [η] of 0.9. This copolymer was dissolved in methyl ethyl ketone to prepare a 1% by weight solution. On the other hand, Vylon (linear saturated polyester resin, manufactured by Toyobo Co., Ltd.) was used as the core material, and the Vylon
100 parts (by weight, the same applies hereinafter), 5 parts of Peerless 155 (carbon, manufactured by Columbia Ribbon and Carbon Manufacturing Co., Ltd.), and Oil Black BW
(Colorant, manufactured by Orient Chemical Industry Co., Ltd.) (5 parts) was added to toluene, and after dissolving and dispersing in a ball mill for 24 hours, the concentration was adjusted to 5% by weight. The obtained dispersion is dried by blowing air from below while being sprayed from the nozzle of a spray dryer, and the copolymer solution is sprinkled in a shower while the obtained dry powder is fluidized to perform the pressurization of the present invention. I got encapsulated toner for fixing. The average particle size of the resulting encapsulated toner was 13.5μ. 10 parts of this encapsulated toner and an average particle size of about 300μ
A developer was prepared by mixing 90 parts of iron powder (manufactured by Nippon Tetsuko Co., Ltd.), and when the image clarity and fog were examined using the xerography method, clear images with no fog were obtained. I got it. The image quality remained unchanged even after making 10,000 copies. Next, the following test was conducted to examine fixability. Using two chrome-plated steel rolls,
A test paper was prepared by applying a linear pressure of 20 kg/cm ² to fix the developer onto high-quality copying paper. Next, a sheet of blank copy paper was pasted with double-sided adhesive tape to the entire bottom of a 20 mm x 20 mm rectangular steel column weighing 200 g, and the test paper was placed with the side to which the toner was fixed facing up. Place the steel material on the paper with the copy paper facing down, move the steel material back and forth over a certain distance 10 times using only its own weight, and measure the stains caused by the toner transferred to the blank copy paper using a reflectance meter (RM-50 model, ( (manufactured by Murakami Color Research Institute). The evaluation is A for those with a reflectance of 90 to 100%.
70-90% B, 50-70% C, 50%
Those below were ranked as D. The fixing degree of this example was A rank. Example 2 1.5 ml of 1,2,2-trifluoro-1,1,2-trichloroethane was charged into a stainless steel autoclave with a volume of 3, 2 ml of ethyl acetate was added as a chain transfer agent, and after sealing, the autoclave was replaced with nitrogen.
A mixed gas of vinylidene fluoride containing 1.2 mol% chlorotrifluoroethylene was charged and the temperature was 50°C.
After increasing the temperature to 5 kg/cm ² G, 2 g of diisopropyl peroxydicarbonate was charged to start polymerization. Charge polymerization was carried out continuously so as to maintain the pressure at cm ² G, and a vinylidene fluoride copolymer containing 8 mol % of chlorotrifluoroethylene and having an intrinsic viscosity [η] of 1.05 was obtained. The obtained copolymer was encapsulated in the same manner as in Example 1, a developer was prepared, and it was subjected to copying in the same manner as in Example 1. No problems such as image sharpness or fog occurred. The degree of fixing was also rank A, indicating good fixing properties. Example 3 Perfluoro-3-butenoic acid trifluoroethyl ester was used in place of chlorotrifluoroethylene in the polymerization method of Example 2, and the mixing ratio was changed. A vinylidene fluoride copolymer containing 15 mol % of 3-butenoic acid trifluoroethyl ester and having an intrinsic viscosity [η] of 0.86 was obtained. The obtained copolymer was encapsulated in the same manner as in Example 1, a developer was prepared, and it was subjected to copying in the same manner as in Example 1. No problems such as image sharpness or fog occurred. The degree of fixation was also ranked A. Example 4 A vinylidene fluoride copolymer containing 29 mol% of tetrafluoroethylene and having an intrinsic viscosity [η] of 0.94 was obtained in the same manner as in Example 2, except that tetrafluoroethylene was used instead of chlorotrifluoroethylene. The obtained copolymer was encapsulated in the same manner as in Example 1, a developer was prepared, and it was subjected to copying in the same manner as in Example 1. No problems such as image sharpness or capri occurred. The degree of fixation was also ranked A. Examples 5 to 15 Vinylidene fluoride polymers having the compositions shown in Table 1 were obtained in the same manner as in Example 4, except that the monomers shown in Table 1 were used. Table 1 shows the intrinsic viscosity [η] of each copolymer obtained. Each of the obtained copolymers was encapsulated in the same manner as in Example 1, a developer was prepared and subjected to copying in the same manner as in Example 1, and image clarity and fog were examined. The results are shown in Table 1. In Table 1,
◎ indicates very good, 〇 indicates good, and × indicates poor. Further, according to the method shown in Example 1, the degree of fixation of the toner obtained in each example was examined. The results are shown in Table 1.

[Table] Comparative Examples 1 to 6 Polymers having the compositions shown in Table 2 were obtained in the same manner as in Example 4, except that the monomers shown in Table 2 were used (only vinylidene fluoride was used in Comparative Example 1). The intrinsic viscosity [η] of each of the obtained polymers, the image clarity and degree of fog, and the fixability of toners using each polymer were examined in the same manner as in Example 4. The results are shown in Table 2.

【table】

[Table] The polymer obtained in Comparative Example 2 was difficult to dissolve in N,N-dimethylacetamide, and therefore the intrinsic viscosity [η] could not be measured. Furthermore, it was poorly soluble in methyl ethyl ketone and could not be encapsulated. In addition, the polymer obtained in Comparative Example 5 was particularly difficult to encapsulate. Regarding triboelectricity, as described in Hiroharu Sasaki, "Surface", Vol. 13, No. 6, p. 354,
There is a correlation between electrical resistance. Examples 1 to 15
All vinylidene fluoride copolymers obtained are
It had a volume resistivity of 10 ¹⁴ Ωcm or more, and satisfied the triboelectric charging characteristics required for an encapsulated toner for pressure fixing. The composition of the copolymer is the one manufactured by Hitachi, Ltd.
Using an NMR measuring machine (R-42 model), ¹ H and ¹⁹ F were measured using a 10 to 20 wt% copolymer solution dissolved in dimethylacetamide etc. as a sample.
It was calculated from the peak area of the obtained MNR spectrum chart.

Claims (1)

[Claims] 1 N,N-dimethylacetamide as a solvent
Intrinsic viscosity [η] measured at 35℃ is 0.1~
2.5, one of the monomers copolymerized with vinylidene fluoride has the general formula (): CXX'=CYY' () (wherein, X, X', Y, Y' are the same or different and are hydrogen or fluorine) (excluding vinylidene fluoride), or the general formula (): CXX'=CYZ () (in the formula , X, X' and Y are the same as above, Z is an alkyl group having 1 to 10 carbon atoms, a fluoroalkyl group, an alkyl ester group, a fluoroalkyl ester group, an alkyl ether group, a fluoroalkyl ether group, a phenyl group or chlorine atoms)
The monomer () has a vinylidene fluoride content of 60 mol% or more, and the vinylidene fluoride content of the monomer ()
An encapsulated toner for pressure fixing, characterized in that a vinylidene fluoride copolymer containing 80 mol% or more is used as a shell material.