JPH06202383A - Liquid developer for electrostatic recording - Google Patents

Abstract

PURPOSE:To obtain images of high quality with good fixing property and to improve dispersion stability and charge stability by using a modified resin having a specified structure. CONSTITUTION:This developer consists of dispersion of toner particles essentially consisting of a pigment and resin in a carrier liquid. The resin is a modified resin obtd. by graft polymn. of a component G to a copolymer of a component A and a component B so as to introduce side chains having affinity with the carrier liquid. The modified resin has 30-60% grafting rate defined as formula. The component A is polymerizable monomers having adsorptive functional groups to the pigment, the component B is polymerizable monomers having a part to produce polymer radicals by an initiator after copolymerization, and the component G is polymerizable monomers or oligomers which change into a homopolymer soluble with the carrier liquid by single polymn. To prepare the developer, at least these pigment and modified resin are kneaded and dispersed in a carrier liquid by using a dispersing machine to obtain a concentrated toner, which is, as necessary, diluted with the carrier liquid.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive charging type toner used in a process of electrostatically adhering toner particles to an electrostatic latent image formed on an electrophotographic photoreceptor or an electrostatic recording body to form a visible image. The present invention relates to a liquid developer for electrostatic recording, and particularly to a liquid developer for electrostatic recording which is preferably used in a drawing process in which a fixing step after development is not performed.

[0002]

2. Description of the Related Art In order to obtain an image by wet development in electrophotography or electrostatic recording, an electrostatic latent image is formed on an electrophotographic photosensitive member or electrostatic recording paper by a conventional method such as corona discharge or ion flow. A general process is to electrostatically attach toner particles in a liquid developer to form a visible image. The liquid developer used in this method generally contains pigments such as rosin, linseed oil, soybean oil, modified alkyd resin, styrene-butadiene resin, acrylic resin, and other resins or fats together with high insulating and low dielectric constants such as aliphatic hydrocarbons. It is obtained by pulverizing and dispersing in a carrier liquid having a specific ratio. Further, various kinds of organometallic salts represented by metal soap are usually added during or after the dispersion for the purpose of giving a higher charge amount to the toner particles.

Usually, the above-mentioned drawing is carried out by using the liquid developer prepared as described above. However, at this time, the toner particles finally attached to the recording medium are
Fixing is not always performed by pressure or heat. That is, after wet development with a liquid developer, the carrier liquid remaining on the recording medium may be volatilized by natural drying or blast drying to form a final image. Electrostatic plotters are a typical example of this process, and few have fixing mechanisms. The image in the process where the fixing process is not performed is because the adhesion force of the toner particles to the recording medium such as paper or film and the adhesion force between the toner particles are weaker than the image subjected to the fixing process. When handling the recording medium showing the image, there was a case where the image and surroundings were stained or the image itself disappeared due to friction with hands and clothes.

Therefore, in order to improve this fixing property,
Various methods have been taken since before. For example, a pigment obtained by graft-polymerizing a vinyl monomer or a polymerized dye is used (Japanese Patent Publication No. 47-33778).
No. 47-18035), a toner in which a pigment is coated with a resin insoluble in a carrier liquid (Japanese Patent Publication No. 48-24905).
Etc. have been proposed. However, in the graft polymerization on the pigment, since the grafting rate is low, the vinyl monomer remains or homopolymerizes, and the effect is small. On the other hand, in the case of a polymer dye, the dispersion stability is still insufficient, and when a monomer such that the polymer is solvated with the carrier liquid is copolymerized with the dye,
It will dissolve in the carrier liquid. Further, a toner in which a pigment is coated with a resin insoluble in a carrier liquid has a problem that the particle size is large and the dispersion stability is deteriorated.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is suitable for an electrostatic photography system and an electrostatic recording system which have a stable charging property while improving the fixing property without impairing the dispersibility of toner particles. Another object is to provide a liquid developer for electrostatic recording.

[0006]

According to the present invention, in a liquid developer in which at least a toner particle containing a pigment and a resin as a main component is dispersed in a carrier liquid, the resin has the following components A and B. The graft ratio of the resin represented by the following formula 1 (Equation 1) in which the side chain having the affinity for the carrier liquid is introduced by graft-polymerizing the component G to the copolymer P consisting of Provided is a liquid developer for electrostatic recording, which is a resin (hereinafter, this resin is abbreviated as "modified resin"), and a component A: a functional group adsorbing to the pigment. Polymerizable Monomer Having Component B: A Polymerizable Monomer Having a Part Which Becomes a Polymer Radical by an Initiator After Copolymerization Component G: A Polymerizable Monomer or Oligomer Which Becomes a Homopolymer Soluble in the Carrier Liquid by Homopolymerization

[Equation 1] In particular, the molar fraction of the component A in the copolymer P is 10
To 60 mol%, the graft component G is at least one monomer represented by the following general formula (I) (Chemical formula 1) or a polymerizable oligomer thereof, or the pigment-adsorptive functional group of the component A is There is provided the liquid developer for electrostatic recording, each of which has a ring surface electron.

[Chemical 1]

That is, by using the modified resin having the above-mentioned constitution of the present invention as the resin used in the liquid developer for electrostatic recording, the fixing rate and the like can be improved. Hereinafter, the present invention will be described in more detail. Graft ratio of the modified resin is 30%
When it is less than 60% or more than 60%, the fixing rate becomes lower than that of the constitution of the present invention, and the dispersion stability is also impaired in the range where the grafting rate is low. On the other hand, when the mole fraction of the component A in the copolymer P is less than 10 mol%, the modified resin is not sufficiently strongly adsorbed on the pigment surface, and the modified resin floats alone in the carrier liquid. , Adversely affect the charging of the toner particles. Conversely, the mole fraction is 6
When it exceeds 0 mol%, a large amount of the homopolymer of the component G is formed during the grafting reaction, and it becomes difficult to perform sufficient modification.

[0008] In general, as the carrier liquid, an aliphatic saturated hydrocarbon is often used from the viewpoint of cost and safety. Therefore, the graft component G is a solvent that is well compatible with these carrier liquids. It is more preferable to select from a monomer represented by the following general formula (I) (Chemical formula 1) or a polymerizable oligomer thereof that can be added to improve the dispersibility.

[Chemical 1] Further, in order to suppress the adverse effect on the charging property of the toner particles, it is preferable that the pigment-adsorptive functional group of the component A has a ring surface electron. That is, in order to achieve strong adsorption between the pigment-modified resins without causing a side effect on the chargeability of the toner particles due to the transfer of charges from the modified resin,
It is preferable that the modified resin and the pigment are adsorbed by the interaction between the ring surface electrons and the adsorption site on the surface of the pigment.

To prepare the liquid developer for electrostatic recording of the present invention, at least the above-mentioned pigment and modifying resin are kneaded and dispersed together with a carrier liquid by a known disperser such as an attritor, a ball mill and a sand mill. To obtain a concentrated toner, which may be diluted with a similar carrier liquid if necessary. Further, in order to control the charge amount to be preferable, a generally used charge control agent such as metal soap or metal naphthenate may be added as an additive during dispersion and / or dilution, if necessary.

Next, specific examples of the components A, B, and G, which are the raw materials of the modified resin used in the present invention, will be described. However, each component that can be used in the present invention is not limited to the following specific examples as long as it has the above-mentioned constitutional range. Component A is a polymerizable monomer having a functional group that is adsorptive to the pigment, and specifically, acrylic acid, methacrylic acid,
Examples thereof include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, hydroxymethyl acrylate, hydroxymethyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, styrene, vinyltoluene and vinylnaphthalene. Among these, those containing an aromatic ring having a ring surface electron such as styrene, vinyltoluene and vinylnaphthalene are preferable.

The component B is a polymerizable monomer having a portion which becomes a polymer radical by the initiator after copolymerization with the component A, and the portion which becomes a polymer radical is hydrogen or halogen attached to a tertiary carbon or an allyl carbon. Is the part that is pulled out. Therefore, specific examples of the component B include butadiene, isoprene, 1,3-pentadiene, vinyl acetate, halogen substitution products thereof, and the like.

Component G is a polymerizable monomer or oligomer capable of becoming a homopolymer soluble in a carrier liquid (specifically described later) by homopolymerization, and specifically, lauryl methacrylate, lauryl acrylate, stearyl methacrylate, Stearyl acrylate, 2-ethylhexyl methacrylate, 2-ethylhexyl acrylate, dodecyl methacrylate, dodecyl acrylate, hexyl methacrylate, hexyl acrylate,
Monomers such as octyl methacrylate, octyl acrylate, cetyl methacrylate, cetyl acrylate, vinyl laurate, vinyl stearate, nonyl methacrylate, nonyl acrylate, decyl methacrylate, decyl acrylate, cyclohexyl methacrylate, cyclohexyl acrylate, vinyl isoamyl ether, vinyl 2-ethylhexyl ether, etc. Alternatively, an oligomer, a derivative thereof, a halogen-substituted product, or the like can be given.

The copolymer P used in the present invention comprises the component A,
The specified amount of the component B may be prepared by a usual method such as radical polymerization, or a copolymer which is commercially available and which meets the conditions may be selected and used. For example, a versatile copolymer such as styrene-butadiene rubber is
Many chemical companies such as Sumitomo Chemical, Asahi Kasei, Nippon Synthetic Rubber, Mitsubishi Kasei, etc. have various copolymerization ratios on the market, so even if a more suitable one is used as a raw material for the modified resin, I don't care.

To prepare the modified resin by grafting the component G on the copolymer P, for example, the copolymer P is dissolved in a non-aqueous solvent, then the component G is added dropwise, and azobisisobutyronitrile ( AIBN), benzoyl peroxide (BP
The polymerization reaction may be performed at a temperature of about 60 to 120 ° C. in the presence of a polymerization initiator such as O) which initiates the polymerization at a relatively low temperature. Examples of the polymerization initiator used for the resin modification of the present invention include phenylazotriphenylmethane, t-butyl peroxide and the like in addition to the above AIBN and BPO.

The pigment used in the present invention is not particularly limited, and black pigments such as carbon black and organic and inorganic pigments having various colors can be used. In particular, in order to obtain better dispersion stability, it is advantageous to use an organic pigment having a relatively small pigment specific gravity and a large resin adsorption ability.

The carrier liquid used in the developing solution of the present invention is preferably an aliphatic hydrocarbon or its derivative. Specific examples thereof include paraffinic or isoparaffinic hydrocarbons (Isopar H, Isopar G, Isopar L, Isopar K, No. 6 Solvesso 100, etc.), ligroin, n-hexane, n-heptane, Iso-octane, n-octane, cyclohexane and the like are used alone or in combination of two or more.

[0017]

EXAMPLES The present invention will be described in more detail based on the production examples of modified resins and the examples using the obtained modified resins, but the present invention is not limited to the following examples. Absent. In addition, as the modified resin in the examples, in order to confirm the exact part by weight of the modified resin of the present invention, the resin dispersion liquid obtained in Modified Resin Production Example 1, 2, 3 or 4 was purified. , Only the modified resin is Isopar H (manufactured by Esso)
A dispersion liquid was used in which the solid content was 30% by weight, but in the actual use, it is not necessary to purify the modified resin. Incidentally, all "parts" in the formulations in Examples and Comparative Examples are parts by weight,
In the comparative examples, the weight of the modified resin also includes the weight of the dispersion medium.

Production Example of Modified Resin Production Example of Modified Resin (1) In a 2.0-liter flask equipped with a stirrer, a thermometer, a cooling tube, and a dropping funnel, 400 g of toluene and styrene-butadiene copolymer resin (styrene Ingredient = 50 mol
%) (250%), and after purging with nitrogen, a monomer solution consisting of 300 g of 2-ethylhexyl methacrylate and 10 g of benzoyl peroxide was added dropwise thereto over 1 hour while stirring with heating at 80 ° C. Then, polymerization was carried out at this temperature for 9 hours. As a result, a resin dispersion liquid in which 95% of 2-ethylhexyl methacrylate was polymerized was obtained. When the amount of 2-ethylhexyl methacrylate homopolymer in this resin dispersion was measured, it was 20% by weight of the charged amount of 2-ethylhexyl methacrylate monomer. That is, graft rate = 47% (= [300-300 ×
0.05-300 × 0.2] / [250+ (300-3
00 × 0.05-300 × 0.2)] × 100%), and a modified resin conforming to the constitution of the present invention was obtained.

Modified Resin Production Example (2) In a 2.0 liter flask equipped with a stirrer, thermometer, cooling tube, and dropping funnel, 400 g of toluene, methylmethacrylate / butadiene copolymer resin (methylmethacrylate component = 30 mol) %) (200%), and after purging with nitrogen, a monomer solution consisting of 200 g of 2-ethylhexyl methacrylate and 12 g of benzoyl peroxide was added dropwise thereto over 1 hour while stirring with heating at 80 ° C. Then, polymerization was carried out at this temperature for 9 hours. As a result 2-
A resin dispersion having 95% of ethylhexyl methacrylate polymerized was obtained. When the amount of 2-ethylhexyl methacrylate homopolymer in this resin dispersion was measured, it was 10% by weight of the charged amount of 2-ethylhexyl methacrylate monomer. That is, graft rate = 46
%, And a modified resin conforming to the constitution of the present invention was obtained.

Modified Resin Production Example (3) 400 g of toluene and styrene-butadiene copolymer resin (styrene component = 50 mol) were added to a 2.0 liter flask equipped with a stirrer, thermometer, cooling tube, and dropping funnel.
%) (250%), and after purging with nitrogen, a monomer solution containing 250 g of vinyl 2-ethylhexyl ether and 10 g of benzoyl peroxide was added dropwise thereto over 1 hour while stirring with heating at 80 ° C. Then, polymerization was carried out at this temperature for 9 hours. As a result, a resin dispersion liquid in which 93% of vinyl 2-ethylhexyl ether was polymerized was obtained. When the amount of vinyl 2-ethylhexyl ether homopolymer in this resin dispersion was measured, it was 10% by weight of the charged amount of vinyl 2-ethylhexyl ether monomer. That is, the graft ratio was 45%, and a modified resin conforming to the constitution of the present invention was obtained.

Modified Resin Production Example (4) To a 2.0 liter flask equipped with a stirrer, a thermometer, a cooling tube, and a dropping funnel, 400 g of toluene and methylmethacrylate / butadiene copolymer resin (methylmethacrylate component = 30 mol) %) (200%), and after purging with nitrogen, a monomer solution containing 200 g of vinyl 2-ethylhexyl ether and 12 g of benzoyl peroxide was added dropwise thereto over 1 hour while stirring with heating at 80 ° C. Then, polymerization was carried out at this temperature for 9 hours. As a result, a resin dispersion liquid in which 95% of vinyl 2-ethylhexyl ether was polymerized was obtained. Vinyl 2 in this resin dispersion
When the amount of -ethylhexyl ether homopolymer was measured, it was 8% by weight of the charged amount of vinyl 2-ethylhexyl ether monomer. That is, graft rate = 47%
Thus, a modified resin that matches the constitution of the present invention was obtained.

Example 1 Carbon black 5 parts Resin according to modified resin production example (1) 50 parts Calcium alkylsalicylate 1 part Isopar H 44 parts Mixture of the above composition was pulverized and dispersed by a ball mill for 24 hours to obtain a concentrated toner. 50 parts for Isopar H75
When diluted with 0 part, a liquid developer for electrostatic recording having positive chargeability and good dispersibility was obtained. Using this liquid developer for electrostatic recording, an electrostatic plotter C manufactured by Versatec
When a drawing was performed using E-3436, a high-quality image with high image density and high contrast was obtained. Then, after leaving this image for 24 hours, the image was peeled off using a Scotch mending tape (manufactured by Sumitomo 3M Ltd.), and the image density of the remaining image was divided by the original image density to display the percentage. The fixing rate was used. Furthermore, this electrostatic recording liquid developer was allowed to stand for 90 days to confirm the dispersion stability of the toner particles. To check the stability of the toner charge amount, the toner specific charge amount was measured one day after the adjustment of the liquid developer for electrostatic recording and 90 days after the adjustment. The results of the above tests are shown in Table 1.

Example 2 The pigment was used as C.I. I. A liquid developer for electrostatic recording was prepared in the same manner as in Example 1 except that PIGMENT BLUE 25 (phthalocyanine blue) was used. As a result, positive chargeability was exhibited and the dispersibility was good. Each test was performed on this electrostatic recording liquid developer in the same manner as in Example 1. The test results are shown in Table 1.

Example 3 Carbon black 5 parts Resin according to modified resin production example (2) 60 parts Calcium alkyl salicylate 1 part Isopar H 34 parts Example 1 except that the composition of the concentrated toner was the above mixture.
When the liquid developer for electrostatic recording was adjusted in the same manner as
It showed positive chargeability and good dispersibility. Each test was performed on this electrostatic recording liquid developer in the same manner as in Example 1. The test results are shown in Table 1.

Example 4 Carbon black 5 parts Resin according to modified resin production example (3) 50 parts Calcium alkylsalicylate 0.8 part Isopar H 44.2 parts Example 1 except that the composition of the concentrated toner was the above mixture.
When the liquid developer for electrostatic recording was adjusted in the same manner as
It showed positive chargeability. Each test was performed on this electrostatic recording liquid developer in the same manner as in Example 1. The test results are shown in Table 1.

Example 5 Carbon black 5 parts Resin according to modified resin production example (4) 60 parts Calcium alkylsalicylate 0.8 parts Isopar H 34.2 parts Example 1 except that the composition of the concentrated toner was the above mixture.
When the liquid developer for electrostatic recording was adjusted in the same manner as
It showed positive chargeability. Each test was performed on this electrostatic recording liquid developer in the same manner as in Example 1. The test results are shown in Table 1.

Example 6 As a resin, a styrene component containing 70 mol% of styrene was used.
Modified resin production example (1) for butadiene copolymer resin
Using the same method as above, so that the graft ratio is 55%, 2
A liquid developer for electrostatic recording was prepared in the same manner as in Example 1 except that a resin grafted with -ethylhexyl methacrylate was used, and each test was conducted in the same manner as in Example 1. The test results are shown in Table 1.

Example 7 As a resin, styrene containing 20 mol% of styrene component was used.
Modified resin production example (1) for butadiene copolymer resin
In the same manner as described above, adjust the graft ratio to 35%.
A liquid developer for electrostatic recording was prepared in the same manner as in Example 1 except that a resin grafted with -ethylhexyl methacrylate was used, and each test was conducted in the same manner as in Example 1. The test results are shown in Table 1.

Comparative Example 1 As a resin, styrene containing 80 mol% of styrene component was used.
Modified resin production example (1) for butadiene copolymer resin
In the same manner as described above, 2 so that the graft ratio is 20%.
A liquid developer for electrostatic recording was prepared in the same manner as in Example 1 except that a resin grafted with -ethylhexyl methacrylate was used, and each test was conducted in the same manner as in Example 1. The test results are shown in Table 1.

Comparative Example 2 As a resin, a styrene / butadiene copolymer resin having a styrene content of 5 mol% was prepared in the same manner as in Modified Resin Production Example (1) so that the graft ratio was 70%. −
A liquid developer for electrostatic recording was prepared in the same manner as in Example 1 except that a resin grafted with ethylhexyl methacrylate was used, and each test was conducted in the same manner as in Example 1. The test results are shown in Table 1.

[0031]

[Table 1] The meaning of the symbol of dispersion stability is as follows. ⊚: Sediment is not seen at all or is very small. ◯: A small amount of sediment is seen, but it is redispersed by gentle stirring. Δ: A precipitate is seen, but it is redispersed temporarily by stirring. X: Many sediments are seen and do not redisperse even with stirring.

[0032]

The liquid developer for electrostatic photography according to the constitution of the present invention, as is clear from the comparison between the examples and the comparative examples,
It is effective for forming a high-quality image with good fixability, and is also excellent in dispersion stability and charge stability.

Claims (4)

[Claims] 1. A liquid developer obtained by dispersing toner particles containing a pigment and a resin as a main component in a carrier liquid, wherein the resin is a component P relative to a copolymer P consisting of the following components A and B. A modified resin having a graft ratio of 30 to 60%, represented by the following formula 1 (Equation 1), in which a side chain compatible with the carrier liquid is introduced by graft-polymerizing G. Liquid developer for electrographic recording. Component A: Polymerizable monomer having a functional group adsorbing to the pigment Component B: Polymerizable monomer having a portion which becomes a polymer radical by an initiator after copolymerization Component G: Soluble in the carrier liquid by homopolymerization Polymerizable monomer or oligomer that can be a homopolymer 2. The liquid developer for electrostatic recording according to claim 1, wherein the mole fraction of the component A in the copolymer P is 10 to 60 mol%. 3. The static component according to claim 1, wherein the graft component G is at least one monomer represented by the following general formula (I) (Chemical formula 1) or a polymerizable oligomer thereof. Liquid developer for electrographic recording. [Chemical 1] 4. The liquid developer for electrostatic recording according to claim 1, wherein the pigment-adsorptive functional group of the component A has ring surface electrons.