JPH0368962A - Liquid developer for electrostatic latent image - Google Patents

Abstract

PURPOSE:To prevent the generation of a foul odor from a liq. developer at the time of fixing and to make the developer adaptable to high-speed bulk copying by using polydimethylsiloxane having a specified viscosity as the liq. carrier of the developer. CONSTITUTION:When toner particles are dispersed in a liq. insulating carrier to obtain a liq. developer for an electrostatic latent image, polydimethylsiloxane having <=1cs viscosity is used as the liq. carrier. Polydimethylsiloxane has a structure represented by formula I and is commercially available and the viscosity depends on the number of n in the formula I. Since this polydimethylsiloxane has relatively high thermal stability, unlike a developer using the conventional isoparaffin solvent the resulting developer does not generate a foul odor at the time of fixing, does not pollute the environment even at the time of high-speed bulk copying and is hygienically favorable. In the case of >1cs viscosity, the developer foams up and the sharpness of an image is remarkably reduced.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a liquid developer for electrostatic latent images.

[Prior Art] A liquid developer for electrostatic latent images is made by dispersing a toner mainly consisting of a colorant and a resin, optionally with a polarity control agent, in a carrier liquid with high insulation and low dielectric constant. .

Conventionally, carrier liquids include cyclohexane, decalin, kerosene, isoparaffinic solvents, light oil, gasoline,
It is believed that salt fluorinated hydrocarbons can be used.

Practically speaking, carrier liquids with high electrical resistance (10"081
11 or more), low dielectric constant (3 or less), low dissolving power (solubility coefficient of about 7), odorless, transparent, non-irritating to the skin, and harmless. For these reasons, isoparaffinic solvents have been put into practical use (for example, Exxon's Isopar (trade name: 1sopar)).

[Problem to be solved by the invention] Nowadays, wet-type copying machines are also becoming paper-free.
Furthermore, higher image density is required, and this has been met by depositing a large amount of toner on the transfer paper. However, when increasing the amount of toner adhesion, it is necessary to increase the temperature of the fixing roller of the fixing device or use a carrier liquid with good evaporability in order to improve fixing performance. Carrier liquid vapor concentration may increase and a strange or unpleasant odor may be felt. This tendency is particularly noticeable during large-volume, continuous copying work, and is unfavorable from a sanitary standpoint, so consideration must be given to indoor ventilation and, in some cases, it may be necessary to limit the copying speed.

In view of these circumstances, the present invention has been developed to provide an electrostatic latent image liquid that can accommodate higher fixing speeds, does not emit any strange odor from the generated vapor, and uses a carrier liquid that poses no problems for the indoor environment. The purpose is to provide a developer.

[Means for Solving the Problems] The present inventors have attempted to solve the above-mentioned problems.
It was discovered that it satisfies the above-mentioned basic performance requirements for a carrier liquid, such as low dielectric constant and toner dispersibility, and does not generate any off-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, characterized in that the insulating carrier liquid is made of polydimethylsiloxane of 1 cs or less. Liquid developer for electrostatic latent images, (2)
The liquid developer for electrostatic latent images according to claim (1), wherein the carrier liquid is a blend of polydimethylsiloxane and isoparaffin, and (3) the carrier liquid is heated to a temperature of 1 cs or less. ) is a liquid developer for electrostatic latent images.

Next, before explaining the liquid developer of the present invention, a wet type electrophotographic copying machine to which this developer is applied will be described.

FIG. 1 is a schematic diagram showing an example of a wet-type electrophotographic copying machine, in which an electrostatic charge image on a photoreceptor drum l is formed by a developer holding a developer which is rotated with a minute gap between the photoreceptor drum and the photoreceptor drum l. The image is developed by rollers 2 and 3, and the developing rollers 2 and 3 are cleaned by a scraper 4.5.During copying, the photosensitive drum l is moved at a constant speed in the direction of the arrow by a drive device (not shown). After being rotated and uniformly charged by the main charger 6, the original image is projected through the optical system 7 to form an electrostatically charged image.The area other than the image forming area on the photosensitive drum l is neutralized by the eraser 8. be done.

The electrostatic charge image is developed by a wet type developing device having developing rollers 2 and 3 as described above, and then this toner image is transferred from a paper feeder (not shown) to a conveying roller 9 as indicated by a broken line arrow. The image is transferred by the transfer charger 12 onto the transfer paper 11 fed through the lO. The transfer paper 11 with the image is transferred to the photosensitive drum by separation rollers 13 and 14.
2 and guided by a conveyor belt 15 to a fixing device shown in FIG. In this fixing device, toner 207
The transfer paper 11 carrying the image is fixed by a heat roller 201 having a built-in heater 202 and a presser roller 204 .

In addition, in FIG. 2, 203 is a cleaning bat;
205 is a cleaning brush, and 206 is an exterior.

After the photosensitive drum 1 is separated from the transfer paper, residual developer is removed by a cleaning unit 16, and a static eliminator (static eliminator 1) is used to remove the residual developer.
7 or static elimination charger) to remove the residual charge and use it for the next copy. In addition, the cleaning unit (6 is a cleaning foam roller 161, a squeezing roller 162)
and a cleaning blade 163, and the residual developer collected here is extracted to the outside from a drain liquid collection hole 164.

In the above-mentioned wet type developing device, a developing roller 2.3, a squeeze roller 18, and a scraper 19 in contact with the squeeze roller are disposed in the developing section. The number of developing rollers may be one or two or more, but the gap between these developing rollers 2.3 and the photosensitive drum 1 is 0.
．． It is desirable to keep them separated by about 1 to 0.2 m+n.

Similarly, the gap between the squeeze roller 18 and the photosensitive drum 1 is preferably 0.05 to 0.09 um. The developing rollers 2 and 3 are connected to the photosensitive drum 1 by a driving device.
The squeeze opening l8 is rotated at a peripheral speed faster than the peripheral speed of the photoreceptor drum, and the surface of the squeeze opening l8 is rotated at an even faster peripheral speed in the direction opposite to the surface of the photoreceptor drum. The developer is supplied and circulated to the developing section through a developer supply pipe 20, a developer supply nozzle 21, a developer recovery hole 22, and a developer recovery vibrator 23.

In addition, in the drawing, 24 is a pump motor, 25 is a pump, 2
6 is a developer concentration detector, 27 is a float switch (liquid level detector), 28 is a developer tank for replenishment, 29 is a carrier liquid tank for replenishment, and 30 is a developer tank.

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

As already mentioned, the liquid developer is made by dispersing a toner mainly consisting of a colorant and a resin in a carrier liquid.

The carrier liquid used in the present invention is (1) polydimethylsiloxane of 1 cs or less, (2) a blend of polydimethylsiloxane and isoparaffin, or (3)
cs or less, or a blend of polydimethylsiloxane and isoparaffin.

Here, the polydimethylsiloxane has the structure shown below.

Various viscosities are commercially available depending on the number of n. For example, KP9BL O, 85csSKP98L 1c
s.

KF-96L 2cs (manufactured by Shin-Etsu Silicone)
, 5H2001cs, 5H-2001,5cs (manufactured by Toray Silicone), and the like.

This polydimethylsiloxane has relatively high thermal stability and does not emit an odor when it comes into contact with a hot roll during fixing, unlike when conventional isoparaffin solvents are used, and is environmentally friendly even in high-speed, large-volume copying. It is very desirable from a sanitary point of view.

Furthermore, it has the advantage that loss due to evaporation is extremely small compared to isoparaffinic solvents.

As described above, polydimethylsiloxane is excellent as a carrier liquid for a liquid developer for developing electrostatic latent images, and is particularly well suited for high-speed, large-scale copying. The polydimethylsiloxane used in the present invention must have a viscosity of 1 cs or less. When a carrier liquid having a viscosity of more than 1 cs is used as a carrier liquid, the liquid developer foams, which significantly reduces the sharpness of the image formed. Although this foaming occurs even when the viscosity is 1 cs or less, the degree of foaming is slight and does not have such an adverse effect that it becomes a practical problem.

However, even if the viscosity exceeds 1 cs at room temperature, if it is maintained at 1 cs or less by heating when used as a liquid developer carrier liquid, the negative effects of foaming may appear in practical use as described above. can be avoided. This heating can be performed, for example, by providing a heater inside the developing tank 30.

Isoparaffins that can be used in combination with this polydimethylsiloxane include, for example, Isopar L (boiling point 188-210°C), Isopar M (205-252°C), and Isopar G (manufactured by Exxon).
158-177℃) Isopar H (174-190℃
), IP Solvent 2028 (21
0-265℃) IP Solvent 2835 (275
~350°C), IP Solvent 1620 (188~20
5℃), Isosol 400 (206~
257°C), indodecane (176°C) manufactured by BP Chemical Co.
~185°C), and isooctane, ligroin (both have boiling points of 120~190°C), and the like. When these isoparaffins are used in combination with polydimethylsiloxane, the polysiloxane is used in a proportion of 5Vo 1% or more, preferably 25Vo 1% or more. Polydimethylsiloxane is 5Vo
If it is less than 1%, a strange odor will be felt during continuous copying.

As toner particles to be dispersed in the polydimethylsiloxane carrier liquid of the present invention, conventionally known toner particles can be used.

For example, as a colorant constituting toner particles, (1)
Degussa's Printex G1 Printex v1 Printex U1 Special Black 15, Special Black 4, etc. (3) Mitsubishi Kasei's #44, #3
0, MR-11, MA-100, etc. (3) Morgam L1 Black Pearl 1300 manufactured by Cabot. Black Baal 1100, Black Pearl 900, Sogal 40
0, Tugal 660, etc., (4) Inorganic pigments such as Neo Spectra■ manufactured by Columbia, Robin 1035, Robin 1252, etc., Phthalocyanine Blue, Phthalocyanine Green, Sky Blue, Rhodamine Lake, Malachite Green Lake, Methyl Violet Lake, Peacock Blue Lake. , Naphthol Green B1 Naphthol Green Y1 Naphthol Yellow S1 Naphthol Red, Linole Fast Yellow 2G, Permanent Red 4R, Brilliant Fast Scarlet, Hansa Yellow, Benzidine Yellow Lysol Red, Lake Red C1 Lake Red D1 Brilliant Carmine 8B
, Paanent Red F5R, Pigment Scarlet
Organic pigments such as 3B, indigo, thioindigo, oil pink, Bordeaux 10B are used.

The binder resin constituting the toner particles is expressed by the following formula (1
) R'/CH2-C...(1) \2 [However, R1 is hydrogen or methyl group R2 is COOCo
H2n++ (n is an integer of 6 to 20). Vinyl monomer A represented by
H2n++ (n is an integer from 1 to 5), -COOCH2C
H20) 1. -COOCH2CH2N(CH3) 2
Or -COOCH2CH2N (C2Hs) 2 is shown. ] Vinyl monomer vinylpyridine,
Copolymers and graft copolymers with vinylpyrrolidone, ethylene glycol dimethacrylate, styrene, divinylbenzene or vinyltoluene (monomer B) are used. In addition to these, (a) N-10 and N-11 manufactured by Eastman Chemical Company
, N-12, N-14, N-34, N-45, C-
10, C-13, C-15, C-16, E-10, E-
11, E-12, E-14, E-15, ll0P, 220P, 220MP manufactured by Mitsui Petrochemicals,
320MP, 410MP, 210MP, I
OMP.

405MP, 200P, 4202E, 4053
E.

131PS151P, 1BL P manufactured by Mitsubishi Kasei.

171PSE 300, E 250P.

Sasol Hl, B2, A1, A2, A3, A4, OA WAX, A WAX manufactured by BASF.

BARECO500, BARE C manufactured by Petrolite
O2000, E-730, E-2018, E-2020
, E-1040, Petronava C1 Petronava C-36
, Petronava C-400, Petronava C-7500, H
PE580, PE130, P manufactured by oechst
ED121, PED13G, PED153
, PED521 , PED522 , PED522 , PED521 , PED522 , PED522
D534, DYNISD manufactured by Union Carbide
YNFSDYNH, DYNJ, DYNK.

Manufactured by Monsite 17) ORIZON 805.705.
50, ALATHON 3.10.12 manufactured by DuPont
．． 14.16.20.22.23, AC polyethylene 6.8A, 1 manufactured by Allied Chemical Co.
5. Evaflex 150.210 manufactured by Mitsui Polychemical Co., Ltd.
．． 220.250.260.310, 380.410
．． Synthetic polyethylene, polypropylene or modified products thereof such as 420.450.480.550.560, (b) Carnauba wax, montan wax, candelilla wax, sugar cane wax, auriculie wax, beeswax, wood wax, bran wax Natural waxes such as (C) Natural resins such as ester gum, hardened rosin, (d
) Natural resin-modified cured resins such as natural resin-modified maleic acid resin, natural resin-modified phenol resin, natural resin-modified polyester resin, natural resin-modified pentaerythritol resin, and epoxy resin can be used as the binder resin.

The developer of the present invention is prepared by charging these colorants and resins together with the carrier liquid into a dispersing machine such as a ball mill, kitty mill, disc mill, vinyl mill, vibration mill, etc. to obtain a particle size of 0.1 to 4.
Crosstalk dispersion may be performed so that a toner component of 0 μ4 is formed. In preparing this developer, it is desirable to treat the colorant in advance with synthetic polyethylene, natural resin, natural resin-modified cured resin, or the like.

[Example] Next, an example will be shown. Parts and percentages herein are based on weight unless otherwise specified.

Example 1 Methyl methacrylate/stearyl methacrylate/hydroxyethyl methacrylate/methacrylic acid (10/80/10/lo
) Copolymer Isopar H dispersion (solid content 33%) 800 parts carbon black (Pr1ntex II manufactured by Degussa)
300 parts of natural resin-modified maleic acid (Tescon M RP manufactured by Tokushima Seishi Co., Ltd.) and 800 parts of polyethylene (171P manufactured by Sanyo Chemical Co., Ltd.) were kneaded in a three-roll mill and pulverized to give 1000 parts of a treated pigment.
(manufactured by Exxon) were kneaded in a pin mill to prepare a concentrated toner.

In addition, 100 parts of various carrier liquids are added to 100 parts of this concentrated toner.
0 parts was added and dispersed to prepare a developer. A test was conducted using this developer using a wet copying machine (CT-5085 manufactured by Ricoh). The results are shown in the table.

[Test conditions] (1) Fixing device ■ Linear speed: 228 IIIl/sec ■ Heater: 700 W ■ Fixing roller surface temperature: 210 ± 10°C (2) Copying conditions Image area ratio 7%, 35 CPM (A-4 size, horizontal Paper), continuous copying for 15 minutes (3) Testing room 30m3 unventilated room (stainless steel lining) [Test items and evaluation method (1) Sharpness 5: Clear with no crushed letters 4: Some letters crushed 3: Letters crushed No problem in use 2: Characters are crushed and slightly unclear 1: Difficult to read: Image cannot be formed (2) Odor after 15 minutes of continuous copying 5: No odor 4: Slight odor 3: Obvious odor 2: Slightly strong odor 1: Strong odor (3) Image density by Macbeth densitometer.

(4) Foam JIS K 33B2. 3. According to 15. 30
Foaming power after seconds is O2 h+ ■: 10 m1 or less △: 30 m1 or less X: 50 m1 or less X X: 100 m1 or more Although the sharpness test result for No. 7 is low due to the influence of some foaming, it is at a level that hardly poses a problem in practical use, and what is more important is that the room is odorless even during continuous copying.

[Effects of the Invention] As explained above, the liquid developer of the present invention uses polydimethylsiloxane of a specific viscosity as the carrier liquid, thereby maintaining excellent copy image characteristics and reducing the carrier liquid vapor generated during fixing. It does not generate any odors and can be used for high-speed, large-scale copying.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a wet-type electrophotographic machine used for testing the developer of the present invention, FIG. 2 is a schematic diagram of the fixing device, and FIG. 3 is a diagram of the principle of a reverse squeeze roller. talent

Claims (3)

[Claims] (1) In a liquid developer for electrostatic latent images in which toner particles are dispersed in an insulating carrier liquid, the insulating carrier liquid is
A liquid developer for electrostatic latent images characterized by comprising the following polydimethylsiloxane. (2) The liquid developer for electrostatic latent images according to claim (1), wherein the carrier liquid comprises a blend of polydimethylsiloxane and isoparaffin. (3) Claim (1) wherein the carrier liquid is heated to a temperature of 1 cs or less.
) or the liquid developer for electrostatic latent images according to (2).