JP2010224108A - Wet-type developer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve such a problem that fixability degrades when a low-volatile carrier liquid having a flash point of at least 70°C is used. <P>SOLUTION: A wet-type developer includes a toner which is dispersed in a carrier liquid having a flash point of least 70°C by using a polymer dispersant. In addition, the developer contains one or more liquids the boiling point of which is equal to or lower than that of the carrier liquid, and which have no compatibility with the carrier liquid, and do not dissolve the toner. In this case, the amount of the contained liquid is 0.5-23 pts.wt. based on the toner of 100 pts.wt. The wet-type developer is excellent in storability and fixability even if it uses a low-volatile carrier liquid having a flash point of at least 70°C. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a wet developer used in a wet electrophotographic image forming apparatus such as a copying machine, a printer, or a digital printing machine.

  In electrophotographic image formation, an electrostatic latent image is formed on an electrostatic latent image carrier such as a photosensitive member by image exposure according to a document image or image data, and the electrostatic latent image is developed. A visible toner image is formed, and the toner image is transferred and fixed on a recording material to obtain a target image. The electrophotographic development method can be divided into a dry development method and a wet development method. The dry development method develops using only toner, whereas the wet development method uses an electrically insulating dispersion medium (carrier liquid). And a liquid developer in which toner is dispersed. According to the wet development method, a toner having a smaller particle diameter can be used as compared with the dry development method, so that a high-definition image can be obtained. For example, the toner particle size in the dry development method is limited to about 5 μm, but in the wet development method, the particle size can be reduced to a submicron order. Also, a reduction in toner consumption can be expected.

  Conventionally, a volatile solvent having a flash point of less than 70 ° C. and designated as the second petroleum of the Fire Service Act has been used for a carrier liquid of a wet developer. However, in order to solve the problems of odor and health hazard caused by VOC (volatile organic compounds), a lower volatile solvent designated as a third petroleum having a flash point of 70 ° C. or higher has come to be used. (For example, Patent Document 1).

Japanese translation of PCT publication No. 2002-522582

  However, the present inventor has found that, when a polymer dispersant is added to a wet developer using the above-mentioned low-volatile solvent as a carrier liquid, the storage property is improved but the fixing property is lowered.

  Accordingly, an object of the present invention is to provide a wet developer that is excellent in storability and fixability even when a low-volatile solvent is used as a carrier liquid.

  In order to solve the above problems, the wet developer of the present invention is a wet developer in which toner is dispersed in a carrier liquid having a flash point of 70 ° C. or higher with a polymer dispersant, and has a boiling point lower than that of the carrier liquid. Thus, 0.5 to 23 parts by weight of one or more liquids that are not compatible with the carrier liquid and do not dissolve the toner are included with respect to 100 parts by weight of the toner.

  The difference between the SP value of the liquid and the SP value of the carrier liquid (SP value of the liquid−SP value of the carrier liquid) is preferably 4 to 30.

  In addition, the absolute value of the difference (SP value of the liquid−SP value of the binder resin) between the SP value of the hydrogen bonding solvent or the liquid SP value of the liquid and the binder resin constituting the toner particles is 4 or more. It is preferable to use a certain solvent.

  The liquid is preferably at least one liquid selected from the group consisting of water, acetic acid, methanol, ethanol, 2-ethoxyethanol, and ethylene glycol.

  According to the wet developer of the present invention, it is possible to improve the fixability while ensuring storage stability. The reason for this is that, conventionally, the polymer dispersant is present in the toner layer in a state in which the carrier liquid is incorporated, and the incorporated carrier liquid remains in the toner layer, so that the fixability is lowered. it is conceivable that. Although details are not clear, it is considered that according to the present invention, the added liquid facilitates discharge of the carrier liquid from the toner layer.

It is a schematic diagram showing an example of a configuration of a wet image forming apparatus using the wet developer of the present invention.

Hereinafter, the present invention will be described in detail.
The wet developer of the present invention has 0.5 to 23 parts by weight of one or more liquids having a boiling point equal to or lower than that of the carrier liquid and incompatible with the carrier liquid and not dissolving the toner with respect to 100 parts by weight of the toner. It is characterized by including.

(Carrier liquid)
A low-volatile and electrically insulating solvent can be used for the carrier liquid. Here, in the present invention, low volatility means that the flash point is 70 ° C. or higher, and electric insulation means that the volume resistance at 25 ° C. is 10 ¹² Ω · cm or higher. Examples of such a solvent include liquid paraffin, silicone oil, animal and vegetable oils, mineral oil and the like from the viewpoint of odor, pollution-free property, and cost. The boiling point of the carrier liquid is preferably 200 ° C. or higher. Examples thereof include liquid paraffin having a boiling point of 300 ° C. or higher and silicone oil having a boiling point of 200 ° C. or higher. Here, the boiling point refers to the boiling point at 1 atm. The same applies to the following description, and the boiling point refers to the boiling point at 1 atm.

  The flash point of the carrier liquid is 70 ° C. or higher, more preferably 200 ° C. or higher. However, in general, when the flash point becomes higher, the viscosity becomes higher, so that another problem arises that developability is lowered. Therefore, the flash point is preferably 170 ° C. or higher and 250 ° C. or lower for liquid paraffin, and the flash point is preferably 170 ° C. or higher and 300 ° C. or lower for silicone oil. Examples of liquid paraffin with a flash point within the range include P40, P70, P120, P300, and P500 of Moresco White manufactured by Matsumura Petrochemical Laboratory Co., Ltd., IP2028 manufactured by Idemitsu Kosan Co., Ltd. and IsoperM manufactured by Exxon Can do. Examples of the silicone oil include TSF451-10, 20, 30 manufactured by Momentive Performance Materials.

(liquid)
The liquid added to the carrier liquid in the present invention (hereinafter referred to as additive liquid) has a boiling point lower than that of the carrier liquid, is incompatible with the carrier liquid, and does not dissolve the toner.
In the present invention, the added liquid has a boiling point lower than that of the carrier liquid, preferably lower than 200 ° C., more preferably lower than 100 ° C. The lower the boiling point, the less likely blisters occur. When the boiling point is increased, the volatilization rate is decreased and remains in the toner layer, so that the fixing property is decreased. In the present invention, when the additive liquid is composed of two or more liquids, the boiling point of the additive liquid means the boiling point of each liquid constituting the additive liquid, and the boiling point of each liquid is the carrier liquid's boiling point. It is lower than the boiling point.

Further, in the present invention, the additive liquid is not compatible with the carrier liquid means that the difference between the solubility parameter (SP value) of the additive liquid and the solubility parameter of the carrier liquid (SP value of the additive liquid−SP value of the carrier liquid). It means 4 or more. Preferably, the difference between the SP value of the additive liquid and the SP value of the carrier liquid is 4 to 30, more preferably 8 to 30.
Here, the solubility parameter is an amount defined by the following equation, where ΔH is the molar evaporation heat of the liquid and V is the molar volume.

[Equation 1]
δ = (ΔH / V) ^1/2

In general, the solubility of a two-component system increases as the difference between the solubility parameters of the two components decreases. The unit of SP value is (MPa) ^1/2 . As the solubility parameter, the value described in Polymer Handbook 4th Ed. Was used. Compounds not described in the Polymer Handbook were calculated by the group contribution method (RFFedors, Polym. Eng. Sci., 14, 147 (1974)).
In the present invention, when two or more kinds of liquids are used as the additive liquid, the SP value of the additive liquid means the SP value of each liquid constituting the additive liquid, and the SP value of each liquid The difference from the SP value of the carrier liquid is 4 or more.

In the present invention, in order to prevent the additive liquid from dissolving the toner, a hydrogen bonding solvent is used for the additive liquid, or the difference between the SP value of the additive liquid and the SP value of the binder resin constituting the toner particles ( It is preferable to use a solvent having an absolute value of (SP value of added liquid−SP value of binder resin) of 4 or more. More preferably, the absolute value of the difference in SP value is 8 or more. When the absolute value of the difference in SP value is less than 4, the additive liquid dissolves or swells the toner particles, thereby reducing the storage property of the wet developer.
Here, the hydrogen bonding solvent used in the present invention is classified into three classes of strong (s), medium (m), and weak (p) in the hydrogen bond strength of the solvent in the Polymer Handbook 4th Ed. Although it is classified (hereinafter referred to as hydrogen bond class), it means a solvent classified as strong (s). For example, water, acetic acid, lower alcohols such as methanol and ethanol, ethylene glycol, 2-ethoxyethanol and the like are included.
In the present invention, when two or more kinds of liquids are used as the additive liquid, the SP value of the additive liquid means the SP value of each liquid constituting the additive liquid, and the SP value of each liquid The absolute value of the difference from the SP value of the binder resin is 4 or more.

  Specific examples of the additive liquid include lower alcohols such as water (boiling point 100 ° C., SP value 47.9), methanol (boiling point 65 ° C., SP value 29.7) and ethanol (boiling point 78 ° C., SP value 26), 2 -Ethoxyethanol (boiling point 135 ° C, SP value 23), acetic acid (boiling point 118 ° C, SP value 20.7), ethylene glycol (boiling point 198 ° C, SP value 29.9) and the like. At least one or more types can be used. Of these, water is preferable because it is highly safe and does not have a problem of odor.

  The addition amount of the additive liquid is 0.5 to 23 parts by weight with respect to 100 parts by weight of the toner. Preferably, it is 0.5-20 weight part. If the amount is less than 0.5 parts by weight, the effect on the fixing property is not sufficient. If the amount is more than 23 parts by weight, the viscosity increases, the latent heat for evaporation increases, and the energy required for fixing increases, which is not preferable. . When a large amount of an additive liquid having a low flash point is added, it may fall under the Fire Service Act, so it is preferable that the amount added is small.

(Toner particles)
The toner particles used in the present invention contain at least a colorant and a binder resin.
The binder resin is a thermoplastic resin and is not particularly limited as long as it does not substantially dissolve in the carrier liquid. A polyester resin is particularly preferable. The polyester resin has sharp melt properties, and it is possible to achieve both storage stability and fixability. Here, the toner particles do not dissolve in the carrier liquid means that the absolute value of the difference between the SP value of the binder resin constituting the toner particles and the SP value of the carrier liquid (SP value of the binder resin−SP value of the carrier liquid). It means 4 or more. Preferably, the absolute value of the difference in SP value is 8 or more

  Specifically, the polyester resin means a resin obtained by polycondensation of a polybasic acid and a polyhydric alcohol. As polybasic acids, isophthalic acid, terephthalic acid, malonic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, fumaric acid, maleic acid, itaconic acid and its acid anhydride, trimellitic acid, trimesic acid, pyromellitic An acid etc. can be mentioned. Isophthalic acid, terephthalic acid, and trimellitic acid are preferable.

  As the polyhydric alcohol, the polyhydric alcohol is not limited to these, but propylene glycol such as ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, dipropylene glycol, 1,4- Butanediols such as butanediol, neopentyl glycol, alkylene glycols (aliphatic glycols) such as 1,6-hexanediol and their alkylene oxide adducts, bisphenols such as bisphenol A and hydrogenated bisphenol, and their addition of alkylene oxides Phenolic glycols of the product, alicyclics such as monocyclic or polycyclic diols, and aromatic diols, triols such as glycerin and trimethylolpropane, and the like. These can be used alone or in admixture of two or more.

  A desired polyester resin can be obtained by polycondensation of the above polybasic acid and polyhydric alcohol. A conventionally known polycondensation method can be used as the polycondensation method. Although it varies depending on the type of raw material monomer, it is generally carried out at a temperature of about 150 ° C to 300 ° C.

  Moreover, it can carry out on arbitrary conditions, such as using inert gas as atmospheric gas, using various solvents, or making the reaction container internal pressure normal pressure or pressure reduction. An esterification catalyst may be used to promote the reaction. As the esterification catalyst, metal organic compounds such as tetrabutyl zirconate, zirconium naphthenate, tetrabutyl titanate, tetraoctyl titanate, 3/1 stannous oxalate / sodium acetate, etc. can be used, but they are products. Those that do not color the ester are preferred. Moreover, you may use an alkyl phosphate, an allyl phosphate, etc. as a catalyst or a hue regulator.

In order to control the molecular weight of the product polyester resin, the polymerization temperature, reaction system pressure, reaction time, etc. may be adjusted. The acid value can be controlled by the molar ratio of the carboxylic acid to be reacted and the alcohol, the molecular weight of the polymer, and the like. The molecular weight is preferably a weight average molecular weight (Mw) of 3000 to 100,000. If the lower limit is not reached, the storage property is deteriorated, and if the upper limit is exceeded, melting by heat becomes difficult.

  The acid value of the polyester resin is preferably 20 mgKOH / g or more. More preferably, it is 20-80 mgKOH / g. This is because a polyester resin having an acid value of 20 mgKOH / g or more can improve storage stability and fixability.

  In addition to polyester resin, binder resin may be styrene-acrylic copolymer resin, styrene-acrylic modified polyester resin, polyolefin copolymer (especially ethylene copolymer), rosin modified phenolic resin, rosin modified as required. An appropriate amount of maleic resin, paraffin wax, etc. can be mixed within a range of 30% by weight or less of the total weight.

As the colorant used in the developer of the present invention, known pigments and dyes can be used.
Specifically, furnace black, lamp black, acetylene black, channel black, C.I. I. Pigment Black, Orthoaniline Black, Toluidine Orange, Permanent Carmine FB, First Yellow AAA, Disazo Orange PMP, Lake Red C, Brilliant Carmine 6B, Phthalocyanine Blue, Quinacridone Red, C.I. I. Pigment blue, C.I. I. Pigment Red, C.I. I. Pigment Yellow, Dioxane Violet, Pictoria Pure Blue, Alkali Blue Toner, Alkali Blue R Toner, First Yellow 10G, Ortho Nitroaniline Orange, Toluidine Red, Barium Red 2B, Calcium Red 2B, Pigment Scar Red 3B Lake, Anthosine 3B Lake, Rhodamine 6B lake, methyl violet lake, basic blue 6B lake, first sky blue, reflex blue G, brilliant green lake, phthalocyanine green G, bitumen, ultramarine blue, iron oxide powder, zinc white, calcium carbonate, clay, barium sulfate, alumina Examples thereof include white, aluminum powder, daylight fluorescent pigment, and pearl pigment.

  In order to improve the dispersibility of the colorant, a colorant having a functional group such as a carboxyl group, a sulfonic acid group, a hydroxyl group, an amino group, or an amide group on the surface by surface treatment or surface modification can be used. .

  The blending amount of the colorant is 3 to 50 parts by weight, preferably 5 to 30 parts by weight with respect to 100 parts by weight of the binder resin. This is because if it is less than 3 parts by weight, the desired concentration cannot be obtained, and if it exceeds 50 parts by weight, the dispersibility and fixability in the binder resin may be impaired.

(Polymer dispersant)
The polymer dispersant is not particularly limited, and a polymer dispersant that is adsorbed on the toner particles and dissolved or semi-dissolved in the carrier liquid can be used. As the polymer dispersant used in the present invention, polyhydroxycarboxylic acid ester, polyaminoamide and salt thereof, polycarboxylic acid and salt thereof, polyalkylolaminoamide and salt thereof, high molecular weight unsaturated acid ester, modified polyurethane, modified polyurethane Polyester, modified polyacrylate, vinyl pyrrolidone copolymer, naphthalene sulfonic acid formalin condensate, polyoxyethylene alkyl phosphate ester, polyoxyethylene alkyl amine, polyester polyamine, polyamine fatty acid condensate, amino modified silicone, etc. it can. Specific examples include V216 and V220 (vinyl pyrrolidone copolymer) manufactured by ISP, Solsperse-S13940 (polyamine fatty acid condensate) manufactured by Nippon Lubrizol, Disperbyk-109 (high molecular weight alkylol manufactured by Nippon Big Chemie). Aminoamide), Wacker Finish WR1100 (amino-modified silicone) manufactured by Asahi Kasei Wacker Silicone, and the like.

  As the molecular weight of the polymer dispersant, those having a weight average molecular weight (Mw) of 2000 to 100,000 can be used. More preferably, it is 5000 to 100,000. When the molecular weight is less than 2000, the dispersion effect is not sufficient, and the storability is lowered. When the molecular weight is greater than 100,000, the solubility in the carrier liquid is lowered and the storability is lowered.

  The polymer dispersant is preferably added in an amount of 0.5 to 20 parts by weight, more preferably 1 to 5 parts by weight, based on 100 parts by weight of the toner. When the amount is less than 0.5 part by weight, the storage property is deteriorated. When the amount is more than 20 parts by weight, the conductivity of the developer is increased, and a problem occurs in the charging property.

  Note that additives such as a known charge control agent and wax can also be added to the wet developer of the present invention, if necessary.

(Manufacture of developer)
Carbon black is kneaded with a kneader into a polyester resin (Kao Corporation, Mn = 3200, Mw = 36000, Tg = 75 ° C., acid value = 50 mgKOH / g, SP value 23), dry pulverized, and coarsely pulverized toner Manufactured. Subsequently, the coarsely pulverized toner, the carrier liquid, a predetermined amount of additive liquid, and a polymer dispersant (based on 100 parts by weight of toner (in the range of 1 to 5 parts by weight) so that the toner concentration becomes 25% by weight. And a wet developer was produced by wet pulverization in a sand mill.

  The toner used this time was dried at 30 ° C. under reduced pressure for 1 day, and the water content was measured to be about 0.3%. The water content of the carrier liquid and the dispersant was on the order of ppm. Therefore, the coarsely pulverized toner used in Table 2 and below was used after drying under reduced pressure and removing water. The toner particle diameter D50 was 2 to 3 μm. The particle size was measured using a laser diffraction particle size distribution analyzer SALD-2200 (manufactured by Shimadzu Corporation).

(Fixability test)
FIG. 1 is a schematic diagram illustrating an example of a configuration of an experimental machine of a wet image forming apparatus. Around the developing roller 104, a charging device 106, a photosensitive member 201, a cleaning blade 105, and a supply roller 103 are sequentially arranged in the rotation direction indicated by an arrow. Around the photosensitive member 201, the cleaning blade 202 and the transfer roller 301 are arranged. Is arranged.

  The surface of the developing roller 104 is uniformly charged to a predetermined surface potential by the charging device 106 to form an electrostatic latent image on the surface of the developing roller 104. Next, the supply roller 103 supplies the developing solution 101 from the developing tank 100 containing the developing solution 101 to the developing roller 104 to form a developing solution coating layer on the surface of the developing roller 104. The developer coating layer is maintained at a constant thickness by the regulating blade 102. When an anilox roller is used as the supply roller, the roller is dug with a developer, and a prescribed amount is measured by the regulating blade.

  Next, the toner particles move at the nip between the developing roller 104 and the photoconductor 201 to form a toner image on the photoconductor. The toner image is transferred to the transfer roller 301 by applying a predetermined voltage to the transfer roller 301. Thereafter, fixing is performed by one or more stages of heat rollers (not shown).

The operating conditions of the image forming apparatus are as follows.
System speed: 40 cm / sec
Photoconductor: negatively charged OPC
Charging potential: -700V
Development voltage (developing roller applied voltage): -450V
Transfer voltage (transfer roller applied voltage): +600
Pre-development corona charging: Needle applied voltage -3 to 5 kV
Squeeze roller applied voltage: -500V
Scorotron charging before transfer: Needle applied voltage -6 kV, grid -150 to 500 V

(Fixability evaluation)
Using the image forming apparatus of FIG. 1, solid patterns (10 cm × 10 cm, attached amount 2 mg / m ² ) of wet developers of Examples and Comparative Examples were formed on fine paper / coated paper. Subsequently, fixing was performed with a heat roller (180 ° C. × nip time 50 msec) (one-step fixing). Further, multistage fixing was performed twice at 180 ° C. × nip time 50 msec.
Thereafter, the part without the offset was rubbed twice with an eraser (Lion 26111, manufactured by Lion Koki Co., Ltd.) with a pressing load of 9.8 N, and the residual ratio of the image density was determined by “X-Rite model 404 manufactured by X-Rite. ”And a four-level rank evaluation was performed based on the following criteria.
A: Image density remaining rate is 95% or more.
○: Image density residual ratio is 90% or more and less than 95%.
Δ: Image density remaining rate is 80% or more and less than 90%.
X: Image density residual ratio is less than 80%.

(Storage evaluation)
About half of the developer was placed in a sample bottle and stored at room temperature (20 to 26 ° C.) for 6 months. After 6 months, the presence or absence of sedimentation was confirmed by visual evaluation.

Whether it was redispersed by shaking or whether it was redispersed by stirring with a spatula was confirmed and evaluated based on the following four-stage criteria.
(Double-circle): It does not settle.
○: Re-dispersed if shaken.
Δ: Re-dispersed when stirred with a spatula.
X: Even if it stirs with a spatula, it does not re-disperse.

  The physical properties of the carrier liquid used are shown in Table 1.

The polymer dispersant used is as follows.
a. Ganex V-220, V-216 manufactured by ISP: Vinylpyrrolidone-α-olefin copolymer b. Solsperse S13940, S11200 manufactured by Nippon Lubrizol
c. Disperbyk-109 manufactured by Big Chemie Co., Ltd .: High molecular weight alkylol aminoamide d. Wacker Finish WR1100 manufactured by Asahi Kasei Wacker Silicone Co .: amino-modified silicone oil

(result)
The evaluation results of the manufactured developer are shown in Tables 2 to 4.

  Table 2 shows the results when water is used as the additive liquid, IP2028 is used as the carrier liquid, V216 is used as the dispersant, and the amount of water added is changed. Here, (SP value of the additive liquid−SP value of the carrier liquid) is 33.6. The absolute value of (SP value of the additive liquid−SP value of the binder resin) is 24.9. The absolute value of (SP value of binder resin−SP value of carrier liquid) is 8.7.

As shown in Table 3, tetrahydrofuran had a large difference between the SP value of the additive liquid and the SP value of the binder resin, but the toner was dissolved, so that the storage property was deteriorated. Further, when the boiling point was increased as in diethylene glycol, the fixability was not improved. Further, since hexane is compatible with the carrier liquid, the fixability was not improved. Further, when IsoperG having a boiling point lower than 200 ° C. was used for the carrier liquid, the fixability was not improved. The SP values of tetrahydrofuran, diethylene glycol, and hexane are 18.6, 24.8, and 14.9, respectively.
In addition, Example 13 was performed under the same conditions as in Example 2 except that Epicoat 1101 (SP value 22) manufactured by Japan Epoxy Resin Co., Ltd., which is an epoxy resin, was used instead of the polyester resin as the binder resin. In addition, even when an epoxy resin was used as the binder resin, the result that the fixing property and the storage property were excellent was obtained.
In Table 3, the hydrogen bond class is the hydrogen bond strength of the solvent classified in the aforementioned Polymer Handbook 4th Ed., Which is strong (s), medium (m), and weak (p). It is classified into three classes.

  Table 4 shows the results when TSF451-20, which is a silicone oil, was used as the carrier liquid. As in the case of using the liquid paraffin shown in Tables 2 and 3, the fixability could be improved by using the additive liquid of the present invention.

DESCRIPTION OF SYMBOLS 100 Developing tank 101 Developer 102 Control blade 103 Supply roller 104 Developing roller 105 Cleaning blade 106 Charging device 201 Photoconductor 202 Cleaning blade 301 Transfer roll

Claims (4)

A wet developer in which a toner is dispersed in a carrier liquid having a flash point of 70 ° C. or higher by a polymer dispersant,
A wet developer containing 0.5 to 23 parts by weight, based on 100 parts by weight of toner, of one or more liquids having a boiling point equal to or lower than that of the carrier liquid and incompatible with the carrier liquid and does not dissolve the toner.   The wet developer according to claim 1, wherein the difference between the SP value of the liquid and the SP value of the carrier liquid (SP value of the liquid-SP value of the carrier liquid) is 4 to 30.   In the liquid, the absolute value of the difference (SP value of the liquid−SP value of the binder resin) between the SP value of the hydrogen bonding solvent or the liquid resin and the SP value of the binder resin constituting the toner particles is 4 or more. The wet developer according to claim 1, wherein a solvent is used.   The wet developer according to claim 1, wherein the liquid is at least one liquid selected from the group consisting of water, acetic acid, methanol, ethanol, 2-ethoxyethanol, and ethylene glycol.

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