JPH026966A - Developer for electrostatic latent image - Google Patents

Abstract

PURPOSE:To allow formation of a stable image by dispersing a coloring agent into an electrical insulating org. compd. which is solid at ordinary temp. and has <=2,000 average mol. wt. CONSTITUTION:This developer is formed by dispersing the coloring agent 6 into the electrical insulating org. compd. 5 which is solid at ordinary temp. and has <=2,000 average mol. wt. The m. p. of this electrical insulating org. compd. 5 is >=30 deg.C, more preferably >=40 deg.C and <=80 deg.C by taking ordinary use environment and ease of handling into consideration. The materials which meet such requirements are exemplified by paraffins, waxes and the mixtures composed thereof which are the dielectrics having about 1.9-2.3 dielectric constant epsilon. The ratio of the coloring agent 6 is usually 0.01-100g, more preferably 0.1-10g per 1l molten state of the electrical insulating org. compd. The stable image is formed in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an electrostatic latent image developer used when wet-developing an electrostatic latent image in an electrophotographic process or the like.

[Prior Art] In the field of image forming technology, a photoconductor charged in a negative manner is selectively irradiated with light in response to an image signal to develop an electrostatic latent image formed. This method is generally called an electrostatic photographic process.The electrostatic photographic process is broadly divided into a dry developing method and a wet developing method.

The dry development method, in principle, simply scatters and adheres coloring agent powder to the electrostatic latent image, so it has the advantage of being excellent in handling and the storage stability of the developed toner. However, in order to meet the increasing demand for high-quality images that has been increasing in recent years, as seen in video printers that print electronic still photographs, the reality is that we have no choice but to give way to wet developing methods.

On the other hand, the wet development method uses a liquid developer in which a dye or pigment as a coloring agent is dispersed in an insulating medium. According to the wet development method, it is possible to obtain resolution and gradation comparable to silver halide photography, and the weather resistance of the formed image is excellent, especially when pigments are used as colorants. Development is underway in this area.

The principle of this wet development method is explained with reference to FIG. For convenience, this figure is shown assuming that each step is sequentially applied to a long photosensitive substrate (1). In the charging step, the photosensitive substrate (1) is uniformly charged, for example, negatively, using a suitable charging means such as a corona discharger (2). In the next exposure process, a semiconductor infrared laser light source (3
) or the like is used to selectively irradiate light corresponding to the image information, and the negative charge on the exposed area disappears. In the next developing step, the photosensitive substrate (1) on which the electrostatic latent image has been formed as described above passes through the developing tank (4). In the developing tank (4), positively charged colorant particles (
6) is dispersed therein, and when this comes into contact with the photosensitive substrate (1), the colorant particles (6) are dispersed in the colorant particles (6).
It migrates toward a negatively charged site and attaches to it. During the final fixing process, colorant particles (
6) is removed, and an image is formed on the photosensitive substrate (1) through a static elimination process.

[Problem to be solved by the invention]

By the way, the conventional n! The insulating medium used in the electrostatic latent image developer in the formula development method is a substance that is liquid at room temperature, such as saturated hydrocarbon-based Isopar G (manufactured by Esso). However, in such electrostatic latent image developers, colorant particles that should originally be uniformly dispersed aggregate and
It has the disadvantage of being prone to precipitation. Furthermore, if the concentration of the colorant decreases due to repeated development steps, there is also the problem that storage stability decreases. Furthermore, the above-mentioned insulating medium is a high-molecular organic compound, and replacing it frequently in order to always achieve stable image formation is not only complicated in maintenance, but also undesirable from the perspective of waste liquid treatment. do not have.

SUMMARY OF THE INVENTION Therefore, the present invention aims to provide an electrostatic latent image developer which does not cause the above-mentioned inconveniences, is easy to handle, and enables stable image formation at all times.

[Means for Solving the Problems] As a result of intensive studies to achieve the above-mentioned object, the present inventors have developed a method that replaces the conventional liquid electrically insulating medium.
The inventors have discovered that it is effective to disperse a colorant in an electrically insulating organic compound that is solid at room temperature and has an average molecular weight of 2000 or less, leading to the present invention.

That is, the electrostatic latent image developer according to the present invention is solid at room temperature and is characterized by being made of an electrically insulating organic compound having an average molecular weight of 12,000 or less and a colorant dispersed therein.

The electrically insulating organic compound used in the present invention is an organic compound that is solid at least at room temperature and has an average molecular weight of less than 2,000. The lower limit of the average molecular species is not particularly defined, but practically it is approximately 200 as long as it does not volatilize in the normal usage environment. The melting point is set to be 30°C or higher, more preferably 40°C or higher, taking into consideration the normal use environment and ease of handling. The upper limit of the melting point is not particularly defined, but practically it is around 100'
The temperature is more preferably 80°C or less than C1. This means that even if the temperature is too high, extra energy will be consumed for heating.
When an electrostatic latent image developer prepared using the above-mentioned insulating organic compound is used, for example, by forming it on a sheet-like base material, the temperature exceeds the heat-resistant temperature of the material generally used as the base material. This is because consideration must be given to things that should not be done.

Materials that meet these requirements include paraffins, waxes, and mixtures thereof. First, as paraffins, there are various normal paraffins having 19 to 60 carbon atoms, ranging from nonadecane to hexaconcune. In addition, waxes include plant waxes such as carnauba wax 1 cotton wax,
Examples include animal waxes such as beetle wax, osichelite, and petroleum waxes such as paraffin wax, microcrystalline wax, and petrolatum. These materials have a dielectric constant ε of 1.9 to 2.3.
It is a dielectric material of about

As the coloring agent dispersed in the electrically insulating organic compound, conventionally known inorganic pigments, Ja-containing pigments, dyes, and mixtures thereof can be used.

For example, non-ms pigments include chromium pigments, cadmium pigments, iron pigments, cobalt pigments, ultramarine blue, navy blue, and the like. In addition, as organic pigments and dyes, Hansa Yellow (C, 1, 11680), Henjijin Yellow G
(C, 1, 21090), Hengejin Orange (C, 1
, 21110), Fast Red (C91, 3708)
5), Brilliant Karmitsu 3 B (C, f, 16
015-Lake), Phthalocyanine Blue (C, 1,
74160), Victoria Blue (C, 1,4259
5-1, ake), Spirit Black (C, 1, 5
0415), Oil Blue (C, 1,74350),
Alkaline Blue (C, 1,42770^), First Scarlet (C, 1, 12315), Rhodamine 6
B (C,1,45160), rhodamine lake (
C, 1,45160-Lake), Fast Sky Blue (C, 1,74200-Lake), Nigrosine (C, 1,50415), Carbon Blur 7, and the like.

These can be used alone or as a mixture of two or more.

In the electrostatic latent image development according to the present invention, in addition to the above-mentioned electrically insulating organic compound and colorant, a resin may be used in combination for the purpose of improving the dispersibility and fixing properties of the colorant. As such resin, known materials can be selected and used as appropriate, examples include butadiene rubber, styrene-butadiene rubber 2
Rubbers such as cyclized rubber and natural rubber, styrene resins, vinyltoluene resins, acrylic resins, and methacrylic resins.

Synthetic resins such as polyester resins, polycarbonate resins, polyvinyl acetate resins, alkyd resins including modified alkyds such as rosin resins, hydrogenated rosin resins, linseed oil modified alkyd resins, and natural resins such as polyterpenes. etc.

In addition, phenolic resins, modified phenolic resins such as phenol-formalin resin, pentaerythritol phthalate, coumaron-indene resins, ester gum resins,
Vegetable oil polyamide resins etc. can also be used, halogenated hydrocarbon polymers such as polyvinyl chloride, chlorinated polypropylene etc., synthetic rubbers such as vinyltoluene-butadiene, butadiene-isoprene etc. #11i, 2-ethyl Polymers of acrylic yarns having long-chain alkyl groups such as xyl methacrylate-1, lauryl methacrylate-1, stearyl methacrylate, lauryl acrylate, and octyl acrylate, or these and other polymerizable monomers Copolymers with (for example, styrene-lauryl methacrylate copolymer, acrylic acid-lauryl methacrylate copolymer, etc.), polyolefins such as polyethylene, polyterpenes, etc. can also be used.

Further, a charge donor is usually added to the electrostatic latent image developer, and the present invention is no exception to this. The charge-donating agents used are, for example, metal salts of fatty acids such as naphthenic acid, octenoic acid, oleic acid, stearic acid, isostearic acid or lauric acid, metal salts of sulfosuccinic acid esters, oil-soluble sulfonic acid metal salts, and phosphoric acid. ester metal salt,
These include metal salts such as abietic acid, metal salts of aromatic carboxylic acids, metal salts of aromatic sulfonic acids, and the like.

Additionally, in order to improve the IF charge of the colorant, Si
oz, AlzO:+, TiOz, ZnO, GazOz.

Inzoz, GeO2, 5nOz, Pbog, MgO
Fine particles of metal oxides such as these or mixtures thereof may be added as a charge enhancer.

Regarding the blending ratio of each component mentioned above, first, the coloring agent is usually 0.01 to 1 to 11 in the melted state of the electrically insulating organic compound.
00 g, preferably 0.1 to log.

Also, the charge donor is usually 0.001 for 1j2.
-log, preferably 0.01-Ig. Furthermore, the charge enhancer is not more than twice the weight ratio of the colorant,
Preferably, it is added in the same amount or less.

Such an electrostatic latent image developer can be used directly by placing it in a suitable container, or by coating or impregnating a suitable support. In order to keep the electrostatic latent image developer in a molten state during use,
It is necessary to provide suitable heating means for the developing tank (4) shown in the figure or for the support described above.

The electrostatic latent image developing process to which the electrostatic latent image developer according to the present invention is applied may be any commonly used process, including the method of forming the electrostatic latent image and the type of photosensitive substrate. No questions asked. For example, with respect to photosensitive substrates, it can be used for photosensitive substrates made of well-known organic or inorganic photoconductors. The applicable organic photoconductors include a wide range of well-known organic photoconductors, and those that have been put into practical use include poly-N-vinylcarbazole and 24.7-h linitrofluoren-9one. Electrophotographic photosensitive substrates, poly-N-vinylcarbazole sensitized with biryllium base dyes, poly-N-vinylcarbazole sensitized with cyanine-based dyes, electrophotographic photosensitive bases containing organic pigments as main components. Examples include electrophotographic photosensitive substrates mainly composed of eutectic complexes consisting of materials, dyes, and resins. Inorganic light! Examples of the 7ilt material include zinc oxide, zinc sulfide, sulfuric acid (mium, selenium, selenium-tellurium base, selenium-arsenic alloy, selenium-tellurium-arsenic alloy, amorphous siliceous material) A material, and the like.

The electrostatic latent image developer of the present invention can also be used when developing an electrostatic latent image generated by photosensitive means, such as charging ↑1-, on a dielectric material. Applicable.

[Effect]

In the electrostatic latent image developer according to the present invention, a colorant is uniformly dispersed in an electrically insulating organic compound that is solid at room temperature. This electrostatic layer image developer is kept in a molten state by an appropriate heating means during use, and when it comes into contact with a photosensitive substrate on which an electrostatic latent image has been formed, it selectively generates an electrostatic charge according to its charge. A latent image developer adheres to form an image. Since this electrostatic latent image developer is solid except when in use, it has excellent handling and storage stability. Therefore, it is possible to provide an electrostatic latent image developer that is easy to maintain and always exhibits stable image forming ability.

〔Example] Hereinafter, preferred embodiments of the present invention will be described.

Example 1 4ζ Example is an example in which a cyan electrostatic latent image developer was prepared.

First, 0.625 g of the coloring agent Lionol Blue l
g was made into small particles by the Zuber-Mercy method to obtain a paste. Next, this paste was mixed with 50 m of another isoparaffinic solvent (manufactured by Enon Co., Ltd., trade name: Isopar II).
p, dispersed in alumina fine particles (
Manufactured by Roki Aerosil Co., Ltd., product name Aluminum Oxide C
) 0.05g was added and a dispersion treatment was performed for 12 hours in a paint shaker together with alumina beads. Furthermore, 0.5 g of a 50% toluene solution of acrylic resin (manufactured by Mitsubishi Rayon Co., Ltd., trade name FRIOI), and 0.025 g of zirconium naphthenate and 0.025 g of calcium naphthenate, which serve as charge-donating agents, are added, and! a Ifl developer was obtained.

Next, 120 ml of paraffin having a melting point of 42 to 44°C was melted in advance at 70°C, and the fA concentrated developer mj2 was dispersed in a bowl to prepare a blue electrostatic latent image developer.

Example 2 In this example, a yellow electrostatic latent image developer was prepared.

First, the colorant Stain 1 Color Fast Yellow 8
GF (manufactured by Daime Doinki Co., Ltd.) 0.5 g and isoparaffin type) container (manufactured by Idemitsu Oil Co., Ltd., trade name I P2825)
0.5 g was made into small particles by the Zuber-Mercy method to obtain Pace 1-. Next, this paste was dispersed in another 50 m2 of isobaratuine-based 7-container (manufactured by Enoso Co., Ltd., trade name: Isobe), and ultrafine particulate anhydrous silica (manufactured by Nippon Aerosil Co., Ltd., trade name: Aerosil 200) was used as a charge enhancer.
) 0.01 g was added and dispersed in a paint shaker with glass beads for 18 hours. below,
Concentrated developer and electrostatic latent image The method for preparing the viewing agent was the same as that described in Example 1.

Example 3 In this example, a magenta electrostatic latent image developer was prepared.

First, the colorant Simular Rhodamine Y1.~j
--F (manufactured by Dainippon Ink Co., Ltd.) 0.8g and linseed oil 0
．． 5 g was made into small particles by the Zuber-Marsey method to obtain a paste. Next, add this paste to another isoparaffin-based container (manufactured by Enon Co., Ltd., trade name: Isopar I!) 5
0m! ! , dispersed inside, along with glass peas, Bain 1
Dispersion treatment was carried out in Noacre for 18 hours. The method for preparing the concentrated developer and electrostatic latent image developer is described in Example 1 below.
- This is the same as the method.

Using the electrostatic latent image developers of each color prepared in Examples 1 to 3, an attempt was made to form a full-color image. The photosensitive substrate used here was C1- (film thickness 50 μm) made of modified vinyl acetate resin, and polyvinyl carbazole 1t3. As the sensitizing side,
/ Ayu 2-color combination (1) Manufactured by Honkokoshiki Co., Ltd., product name N K21
1i92) Photosensitive layer containing 0.2 m g (1 model w-2
00/7 m) was formed. In addition, J-
If the photosensitive substrate and the electrostatic latent image developer solidify immediately after contact, there is a risk of degrading the image quality, so the stage for fixing the photosensitive substrate was heated to 55°C.

As a result, good images with excellent resolution and sharpness were stably obtained.

(Effects of the Invention) As is clear from the explanation below, since the electrostatic latent image developer according to the present invention uses an electrically insulating organic compound that is solid at room temperature, it is easy to handle and store. It has excellent dispersibility of colorants and other additives.Therefore, it is possible to stably obtain high-quality images.Also,
Since it can be disposed of in a solid state after use, it is also preferable from the viewpoint of waste disposal.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram for explaining the principle of the wet development method. 2 ・・ 3 ・ 4 ・ 5 ・ 6 ・ Photosensitive substrate Correct discharge body Semiconductor Infrared laser light source Developing tank Insulating medium Colorant particles Procedure Toichi official book (self-produced) March 1999 31st of the month

Claims (1)

[Claims] An electrostatic latent image developer comprising a colorant dispersed in an electrically insulating organic compound that is solid at room temperature and has an average molecular weight of 2,000 or less.