JP2783846B2 - Liquid developer for electrostatic latent images - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a liquid developer for electrostatic latent images.

[Prior Art] A liquid developer for an electrostatic latent image is obtained by dispersing a toner mainly composed of a colorant and a resin together with a polarity controlling agent, if necessary, in a carrier liquid having a high insulating property and a low dielectric constant. .

Conventionally, it is said that cyclohexane, decalin, kerosene, isoparaffinic solvents, light oil, gasoline, and salt fluorinated hydrocarbons can be used as the carrier liquid.

The carrier liquid has practically high electric resistance (10 ¹⁴ Ωcm or more), low dielectric constant (3 or less), low dissolving power (solubility coefficient is about 7), no odor, Properties such as transparency, harmlessness without irritation to the skin, low flammability, fast drying, etc. are required, and isoparaffinic solvents have been put into practical use from such circumstances [for example, Exxon Isopar (trade name: Isopar)].

[Problems to be Solved by the Invention] By the way, wet-type copiers have become paper-free today, and higher image densities have been demanded. To cope with this, a large amount of toner is deposited on transfer paper. I've been. However, when the toner adhesion amount is increased,
In order to improve the fixing performance, it is necessary to raise the temperature of the fixing roller of the fixing device or to use a carrier liquid having good evaporating properties. May have an unusual or unpleasant odor. This tendency is particularly remarkable in a large-volume, continuous copying operation, which is unfavorable in terms of hygiene.

In view of the above circumstances, the present invention provides a liquid for electrostatic latent image liquid that can cope with an increase in fixing speed, uses a carrier liquid that does not cause any odor in the generated steam, and has no problem in the indoor environment. It is intended to provide a developer.

Means for Solving the Problems The inventors of the present invention have been studying the above to solve the above-mentioned problems, and as a result, a specific silicone oil has a carrier, such as an insulating property, a low dielectric constant, and a toner dispersibility. The present invention was found to satisfy the basic required performance as described above and to generate no unpleasant odor, leading to the present invention.

That is, the present invention provides a liquid developer for electrostatic latent images in which toner particles are dispersed in an insulating carrier liquid, wherein at least a part of the insulating carrier liquid is made of phenylmethyl-based silicone oil. Characteristic liquid developer for electrostatic latent images.

Next, prior to describing the liquid developer of the present invention, a wet electrophotographic copying machine to which the developer is applied will be described.

FIG. 1 is a schematic view showing an example of a wet type electrophotographic copying machine. An electrostatic image on a photosensitive drum 1 is developed by holding a developing solution which is driven to rotate with a small gap from the photosensitive drum 1. The images are visualized by the rollers 2 and 3, and the developing rollers 2 and 3 are cleaned by the scrapers 4 and 5. At the time of copying, the photosensitive drum 1 is rotated in a direction indicated by an arrow at a constant speed by a driving device (not shown).
, The original image is projected through the optical system 7 to form an electrostatic image. The portion other than the image forming area on the photosensitive drum 1 is discharged by the eraser 8.

The electrostatic image is developed by the wet developing device having the developing rollers 2 and 3 as described above, and then this toner image is supplied from the paper feeding device (not shown) through the conveying rollers 9 and 10 as indicated by broken arrows. The image is transferred to the transferred transfer paper 11 by the transfer charger 12. The transfer paper 11 having an image is separated from the photosensitive drum 1 by separation rollers 13 and 14, and is guided to a fixing device shown in FIG. In this fixing device, the transfer paper 11 carrying the toner 207 is
The fixing is performed by a heat roller 201 having a heater 202 therein and a pressing roller 204. In FIG. 2, reference numeral 203 denotes a cleaning pad, 205 denotes a cleaning brush, and 206 denotes an exterior.

After the transfer paper is separated from the photosensitive drum 1, the residual developing solution is removed by the cleaning unit 16 and the residual charge is removed by the static eliminator (the static elimination lamp 17 or the static elimination charger), and is used for the next copy. The cleaning unit 16 includes a cleaning foam roller 161, a squeezing roller 162, a cleaning blade 163, and the like. The residual developer collected here is extracted to the outside through the drainage collecting hole 164. In the above wet developing device, the developing rollers 2, 3 are provided in the developing section.
A squeeze roller 18 and a scraper 19 in contact with the squeeze roller are also provided. The number of the developing rollers may be one or two or more, but it is desirable that the gap between the developing rollers 2 and 3 and the photosensitive drum 1 is separated by about 0.1 to 0.2 mm. Similarly, the gap between the squeeze roller 18 and the photosensitive drum 1 is desirably about 0.05 to 0.09 mm. Then, the developing rollers 2 and 3 are rotated at a peripheral speed higher than the peripheral speed of the photosensitive drum 1 by the driving device, and
Reference numeral 18 denotes a higher peripheral speed, the surface of which is rotated in a direction opposite to the surface of the photosensitive drum at the facing portion. The supply and circulation of the developer to the developing unit are performed through a developer supply pipe 20, a developer supply nozzle 21, a developer recovery hole 22, and a developer recovery pipe 23. In the drawings, 24 is a pump motor, 25 is a pump, 26 is a developer concentration detector, 27 is a float switch (liquid level detector), 28 is a replenishing developer tank, 29 is a replenishing carrier liquid tank, 30 is Represents a developing tank.

 Next, the liquid developer of the present invention will be described.

As described above, the liquid developer is obtained by dispersing a toner mainly composed of a colorant and a resin in a carrier liquid.

The carrier liquid used in the present invention contains at least silicone oil called phenylmethyl silicone oil.
It contains 5 vol% or more, preferably 50 vol% or more.
More preferably, it is 95 vol% or more. This phenylmethyl silicone oil is obtained by substituting some methyl groups of the silicone oil with phenyl groups in terms of chemical structure. This silicone oil has high thermal stability and does not generate oxides that generate off-flavors when it comes in contact with high-temperature rolls during fixing, unlike conventional isoparaffin solvents, and can be used at high speeds and in large-scale copying. Very favorable for hygiene without damaging the environment.

In addition, although this is the same silicone oil, it does not have foaming properties as seen in dimethyl silicone oil, and does not adversely affect the formed image.

Furthermore, there is an advantage that the loss due to evaporation is extremely small as compared with an isoparaffin-based solvent.

As described above, phenylmethyl-based silicone oil is excellent as a carrier liquid for a liquid developer for developing an electrostatic latent image, and is particularly suitable for high-speed and large-volume copying. Such a phenylmethyl-based silicone oil is obtained by substituting at least one methyl group of a dimethylpolysiloxane oil with a phenyl group.
It is commercially available as 200, SRX310, PRX404, PRX407, or Shin-Etsu Silicone KF56, KF58 and the like. As the other carrier liquid that can be used by mixing with the silicone oil, any of conventionally known carrier liquids can be used.

For example, Isopar L manufactured by Exxon (boiling point 188-2
10 ° C), Isopar M (205-252 ° C), Isopar G
(158-177 ° C), Isopar H (174-190 ° C), IP Solvent 2028 (210-265 ° C), IP Solvent 2835 (275-350 ° C), IP Solvent 1620 (166-2
05 ° C), ISOSOL 400 manufactured by Nisseki Chemical Co. (206-257)
° C) and indodecane (176-185 ° C) manufactured by BP Chemical Co., Ltd. In addition, isooctane, ligroin (boiling point: 120-190 ° C) and the like can also be mentioned.

As the toner particles dispersed in the phenylmethyl-based silicone oil carrier liquid of the present invention, conventionally known toner particles can be used.

For example, as a colorant constituting the toner particles,
(1) Degussa Printex G, Printex V, Printex U, Special Black 15, Special Black 4, etc. (3) Mitsubishi Chemical # 44, # 3
0, MR-11, MA-100, etc. (3) Cabot's Mogal L, Black Pearl 1300, Black Pearl 1100, Black Pearl 900, Legal 400, Legal 660, etc.
(4) NeoSpectra II, Robin 103 manufactured by Columbia
5, In addition to inorganic pigments such as Robin 1252, phthalocyanine blue, phthalocyanine green, sky blue, rhodamine lake, malachite green lake, methyl violet lake, peacock blue lake, naphthol green B, naphthol green Y, naphthol yellow S, naphthol red, Lisor First Yellow 2
G, Permanent Red 4R, Brilliant Fast Scarlet, Hansa Yellow, Benzidine Yellow, Lisor Red, Lake Red C, Lake Red D, Brilliant Carmine 6B, Permanent Red F5R, Pigment Scarlet 3B, Indigo, Thio Indigo, Oil Pink, Bordeaux 10B etc. Organic pigments are used.

The following general formula (1) is used as the binder resin constituting the toner particles. [However, R ¹ is hydrogen or a methyl group, R ² is -COOC _n H
_{2n + 1} (n is an integer of 6 to 20). And a vinyl monomer A represented by the following general formula (II): [However, R ¹ is hydrogen or a methyl group, R ³ is -COOC _n H
_{2n + 1} (n is an integer of 1 to 5), -COOCH ₂ CH ₂ OH, shows a _{-COOCH 2 CH 2 N (CH 3} ) 2 or _{-COOCH 2 CH 2 N (C 2} H 5) 2. And copolymers and graft copolymers with vinyl monomers, vinyl pyridine, vinyl pyrrolidone, ethylene glycol dimethacrylate, styrene, divinyl benzene or vinyl toluene (monomer B). In addition to these, (a) N-10, N-11, N manufactured by Eastman Chemical Company
-12, N-14, N-34, N-45, C-10, C-13, C-
15, C-16, E-10, E-11, E-12, E-14, E-1
5, Mitsui Petrochemical's 110P, 220P, 220MP, 320MP, 410M
P, 210MP, 10MP, 405MP, 200P, 4202E, 4053E, 131P, 151P, 161P, 171P, E300, E250 manufactured by Sanyo Chemical Industries, Ltd.
P, Sasol H1, H2, A1, A2, A3, A4, BASF OA WAX, A WAX, Petrolite BARECO5
00, BARECO2000, E-730, E-2018, E-2020, E-1
040, Petronava C, Petronava C-36, Petronava C
-400, Petronava C-7500, PE580, PE1 manufactured by Hoechst
30, PED121, PED136, PED153, PED521, PED522, PED53
4. DYNI, DYNF, DYNH, DYNJ, DY manufactured by Union Carbide
NK, Monsite ORIZON805, 705, 50, DuPont
ALATHON3, 10, 12, 14, 16, 20, 22, 23, AC polyethylene manufactured by Allied Chemical Co., 6, 6A, 15, Epaflex 150, 210, 22 manufactured by Mitsui Polychemicals
0, 250, 260, 310, 360, 410, 420, 450, 460, 550, 56
(B) natural waxes such as carnauba wax, montan wax, candelilla wax, sugar cane wax, auricurie wax, beeswax, wood wax, and brass wax; (c) Natural resins such as ester gum, cured rosin, etc. (d) Natural resin modified maleic acid resin, natural resin modified phenol resin, natural resin modified polyester resin, natural resin modified pentaerythritol resin, natural resin modified cured resin such as epoxy resin It can be appropriately used as a binder resin.

The developer of the present invention is charged with these colorants and resins together with the above carrier liquid into a dispersing machine such as a ball mill, a kitty mill, a disc mill, a pini mill, and a vibration mill, and has a particle size of 0.1 to 4.0 μm.
What is necessary is just to knead and disperse such that m toner components are formed. In the preparation of the developer, it is desirable that the colorant is previously treated with a synthetic polyethylene, a natural resin, a cured resin modified with a natural resin, or the like.

Example Next, an example will be described. All parts and percentages are by weight unless otherwise specified.

Example 1 Methyl methacrylate / stearyl methacrylate /
Hydroxyethyl methacrylate / methacrylic acid (10/8
0/10/10) Isopar H dispersion of copolymer (solid content 33
%) 600 parts carbon black (PrintexU manufactured by Degussa) 300 parts
Maleic acid modified with natural resin (Tescon MRP manufactured by Tokushima Essential Oil Co., Ltd.) 2
A concentrated toner was prepared by kneading 1000 parts of a treated pigment, 600 parts of polyethylene (171P, manufactured by Sanyo Chemical Co., Ltd.) with a three-roll mill, and pulverizing 1000 parts of a treated pigment, 2400 parts of Isopar H (manufactured by Exxon) with a pin mill.

Further, 1000 parts of various carrier liquids were added to 100 parts of the concentrated toner and dispersed to prepare a developer. Using this developer, a test was performed with a wet copying machine (CT-5085 manufactured by Ricoh). The results are shown in the table.

[Test conditions] (1) Fixing device Linear speed: 288mm / sec Heater: 700W Fixing roller surface temperature: 210 ± 10 ° C (2) Copying condition Image area ratio 7%, 35CPM (A-4 size, horizontal paper), 15 min continuous copying (3) non-ventilated room laboratory 30 m ³ (stainless clad) test items and evaluation method] (1) phase separation of the liquid developer (after standing for 24 hours) ○: No phase separation △: slight layer Separation (supernatant opaque) ×: Layer separation (supernatant transparent) (2) Aggregation of toner particles in liquid developer (after standing for 24 hours) ○: None (average particle diameter 0.5 to 0.8μ) △: Slight Yes (average particle diameter 0.7 to 2μ) X: Yes (average particle diameter 2μ or more) (3) Sharpness 5: Clear without character collapse 4: Character collapse is slight 3: Character collapse is recognized but there is no problem in use 2 : Slightly blurred characters and slightly unclear 1: Difficult to read-: Image formation impossible (4) Odor after continuous copying for 15 minutes 5: Odorless 4 : Slight odor 3: Clear odor 2: Slightly strong odor 1: Strong odor (5) Image density According to Macbeth densitometer.

(3) Sharpness and (5) Image density are 24
This is the copy image quality of the first sheet when copying is performed using the developing solution left for a while.

[Effects of the Invention] As described above, the liquid developer of the present invention uses phenylmethyl-based silicone oil as a carrier liquid, thereby maintaining excellent copy image characteristics and reducing carrier liquid vapor generated during fixing. No odor based, high speed,
It can cope with mass copying.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a wet electrophotographic machine used for testing the developer of the present invention, and FIG. 2 is a schematic diagram of an identification attaching device.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kenji Kojima 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Ichiro Tsuruoka 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company, Ltd. (72) Katsuhiro Echigo, inventor 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Mayumi Miyao 1-3-6, Nakamagome, Ota-ku, Tokyo Stock Company (56) References JP-B-36-19060 (JP, B1) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 9/12

Claims (1)

(57) [Claims] 1. A liquid developer for electrostatic latent images comprising toner particles dispersed in an insulating carrier liquid, wherein at least a part of the insulating carrier liquid is made of phenylmethyl silicone oil. Liquid developer for electrostatic latent images.