JPH01126659A - Two-component developer and image forming method using said developer - Google Patents

Abstract

PURPOSE:To obtain an image which is identifiable only under specific UV rays by incorporating a binder resin and brightening agent into a toner and cleaning the surface of a magnetic carrier. CONSTITUTION:At least the binder resin and brightening agent are incorporated into the toner and the surface of the magnetic carrier is cleaned. The image formed by using this toner is colorless or white under natural light and general illumination mainly consisting of a visible light region and is illegible. Recopying of the image is not possible. However, the brightening agent incorporated into the toner receives the excitation by the UV rays and emits light at the wavelength intrinsic to the brightening agent when the UV rays existing in the absorption wavelength region of the brightening agent are projected to the image. The image information is thereby visualized and turned legible.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a developer used in electrophotography and electrophotographic-like copying machines and printers.

[Conventional technology]

2. Description of the Related Art Electrophotography and methods similar to electrophotography are widely used as methods for forming images based on certain image information. In this method, an electrostatic latent image is formed on a photoreceptor made of a photoconductive material, this is developed with a developer, and the resulting toner image is usually transferred to transfer paper and heated. , an image is formed by fixing with pressure or the like. As a developer for developing an electrostatic latent image in such an image forming method, a powder developer is often used because of its ease of handling. Powder developers include one-component systems that use only magnetic toner or non-magnetic toner, and two-component systems that use a mixture of toner and carrier, but powder toners generally have a colorant dispersed in a binder resin. , made into fine powder.

Carpump 2, various dyes, pigments, etc. are usually used as coloring agents, and images formed on paper or sheets with such toners become permanent as so-called hard copies. In particular, although electrophotographic images have a higher shelf life than thermal images, they cannot be recopied using a copying machine or camera, and there is a problem in that there is an extremely high risk of leaking important confidential information.

[Problem that the invention seeks to solve]

For this purpose, conventionally, paper for creating confidential documents in a specific color was used to make the contents illegible when recopying, or as described in Japanese Patent Application Laid-Open No. 14163/1983, the paper was colored by heat. I'm wondering if there is a way to use a toner that does that. However, the former method has a less-than-expected effect in that the document becomes extremely difficult to read or becomes illegible when recopied, and cannot be used as a practical means for preventing leakage of confidential information. In addition, the latter method has the problem that only a pressure fixing method can be used, which limits the pure whiteness to which it can be applied.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the aforementioned problems and provide a developer capable of producing images that are legible only under specific ultraviolet light.

Another object of the present invention is to maintain the confidentiality of the text having image information and prevent it from being re-copied by forming an image using toner that is readable only under the above-mentioned specific conditions. There is a particular thing.

Another object of the present invention is to provide a developer that allows confidential documents to be created without using special paper or sheets or a special camera photographic device.

[Means for solving problems]

In order to solve the above problems, the present invention provides a two-component developer consisting of a toner for developing electrostatic images and a magnetic carrier, the toner containing at least a binding resin and a fluorescent whitening agent, and a magnetic carrier. The carrier has adopted technical measures to ensure that its surface is clean.

That is, while a normal toner contains a binder resin and a colorant, the toner according to the present invention does not contain a colorant and contains at least a binder resin and a fluorescent whitening agent. Images produced using the toner according to the invention are colorless or white and cannot be read under natural light or general illumination consisting mainly of visible light. 1 again! I can't even do ¥#. This image can be visualized by irradiating it with ultraviolet light in the absorption wavelength range of the fluorescent brightener. The fluorescent whitening agent contained in the toner on the image is excited by ultraviolet light and emits light at a wavelength unique to the fluorescent whitening agent, thereby making the image information visible and readable. In this way, the contents of the oath can be confirmed only at a specific location and only when exposed to ultraviolet light, which is effective in preventing leakage of confidential information.

Here, the compounds that produce fluorescence used in the present invention are mainly 4
It has an absorption wavelength in the ultraviolet region of ~400 nm, and although the compound alone may have a slight color, it is at least necessary that when it is made into a toner, it is colorless or white under visible light.

Compounds that meet these conditions include certain fluorescent dyes and fluorescent brighteners. Examples of fluorescent brighteners include:
4.4-bis(4-phenyl-1°2.3-)riazol-2-yl)stilbene-7-(4-methyl-5-phenyl-1,2,3-triazol-2-yl)coumarin, 3-7enyl7-(2H-naphtho(1,2-d)
-) lyazol-2-yl)coumarin (trade name Barcol PSR), 1-(4-acidsulfonylphenyl)-
Coumarin type, stilbene type, benzothiazole type, benzimidazole type, benzoxazole type, pendidi type, etc. such as 3-(4-chloroaphenyl)-2-pizzoline are suitable. The amount of fluorescent brightener to be added is preferably 0.005 to 5 wt per toner.

As the binding resin used in the toner of the present invention, commonly used styrene resins, polyester resins, epoxy resins, and the like can be used.

For example, polystyrene, poly-p-tetrastyrene.

Monopolymers of styrene and its substituted products such as polyvinyltoluene; styrene-p-chlorostyrene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene - Ethyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer.

Styrene-butyl methacrylate copolymer, styrene-acrylic-aminoacrylic copolymer, styrene-aminoacrylic copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether Copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acryonitrile-indene copolymer, styrene-maleic acid copolymer, styrene-maleic acid Styrenic copolymers such as ester copolymers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester,
Polyurethane, polyamide, epoxy resin, polyvinyl butyral.

Polyacrylic acid resin, rosin, modified rosin, terpene resin, phenolic resin, aliphatic or alicyclic hydrocarbon resin,
Aromatic petroleum resins, chlorinated paraffins, paraffin waxes, etc. can be used alone or in combination.

In addition, the toner may contain materials other than those mentioned above, such as a colorless or white charge control agent, a white pigment, and a water-soluble inorganic compound. Also,
Flow control agents, anti-filming agents, and lubricants such as silicon dioxide, alumina, zirconia, silicon carbide, calcium carbonate, clay, talc, and zinc stearate may also be added to the outside of the toner, if necessary. . Any method can be used, such as a toner manufacturing method, a kneading-pulverization method, a spray drying method, a polymerization method, and a phase separation method.

Examples of the magnetic carrier according to the present invention include surface oxidized or unoxidized iron, nickel, and cobalt.

Examples include metals such as manganese, chromium, copper, barium, and rare earths, and ferrites that are alloys or oxides thereof. Alternatively, a composite carrier consisting of magnetic particles and a binder resin may be used. However, the surface of any magnetic carrier must be clean. Here, a clean surface means that there are no minute colored particles on the surface.

Micro colored particles are small pieces of magnetic carrier with a particle diameter of 10 μm or less, and are magnetic to magnetic carriers.

It is electrostatically attached and often occurs during the manufacture of magnetic carriers.

When a two-component toner according to the present invention is prepared by using a magnetic carrier with these minute colored particles attached to the surface, the formed iiiiiigI becomes a visible light legible image due to the minute non-colored particles attached to the toner. , the purpose of the present invention cannot be achieved.

In order to form a film on a different surface of the carrier, a known method such as coating with a resin or the like using a fluidized bed coating device is used. Resins used for coating the carrier surface include polymers and copolymers of vinyl and aromatic vinyl compounds, polyester resins, polyurethane resins, epoxy resins, silicone resins, fluorine resins,
Urea resins, polyamide resins, and the like can be used alone or in combination. Furthermore, these coating resins contain inorganic salts, charge control agents, and fillers.

A lubricant or the like may be added, but it is necessary that no visible fine particles be formed on the surface of the coating carrier.

As a manufacturing method in which the entire surface undergoes a melting process, there is a method in which the magnetic carrier is passed through a high temperature atmosphere higher than the melting temperature of the magnetic carrier.

Such magnetic carriers include reduced iron powder, atomized iron powder, and high-temperature sintered ferrite carriers.

Here, such a carrier that does not contain minute colored particles and has a clean surface can be obtained by coating the surface with a resin or by adopting an inexpensive manufacturing method that involves a melting process.

〔Example〕

The present invention will be explained in more detail with reference to Examples below.
The invention is not limited to these examples.

Example 1 Styrene acrylic resin (Bryolye manufactured by Gutdeyer)
AC) 100 parts by weight, a fluorescent brightener (Hakol PSR manufactured by Halakol Chemical Co., Ltd.) 0.01] The mixture was melted and kneaded in a double-arm kneader at a temperature of 150°C. After cooling and solidifying, it was crushed in a hammer mill and then a jet mill to obtain particles of 20 μm or less. Next, this crushed powder was passed through an air force M& The toner was classified to obtain a toner having a particle size distribution of 5 to 20 μm.Additionally, the toner was added with 0.5% hydrophobic colloidal silica (R972 manufactured by Nippon Aerosil Co., Ltd.).
Parts by weight were added and mixed using a Henschel mixer to prepare toner 1. The resulting toner was white under visible light.

Ferrite carrier (KBN-120° made by Hitachi Metals)
Zn-based) 74-149μ71 1,000 parts by weight was maintained at 100°C in a fluidized bed coating device (Flow Coater manufactured by Freund Sangyo), and 5 parts by weight of silicone resin (5R2410 manufactured by Toshi Silicone) was dissolved in chloroform. After drying, a carrier was obtained.

Mix the above carrier and toner 1 to create a toner concentration of 4% O.
I created the current great agent 1.

Using developer 1, a uniform magnetic brush was formed on a 4-pole magnetized magnet roll including an 800G 32φ development pole with an Alci sleeve through a doctor gap of 0.8 snow, and a development gap of 1.0 was formed. The mu-grain pattern was exposed facing a Se--Te photoreceptor (800φ) having a surface potential of 700 V through a peripheral speed ratio of 1:2.5.
Quiz development was performed at a development bias of 150V. The obtained toner image was transferred onto plain paper using a 5" cotroton, and then transferred to a heat roll fixing machine equipped with a Teflon roll and a silicone rubber roll at a linear pressure of 1,000 yen.
A toner image was formed by fixing at a speed of 160-sec and 190°C. The resulting image was colorless and unreadable under visible light. When this image was irradiated with ultraviolet light using an ultraviolet AT pump, light emission was observed and it was sufficiently legible.

In addition, the image was free from blemishes and had good resolution and sharpness.

Example 2 Styrene acrylic resin (Sanyo Kasei 1118BM73) 1
00 parts by weight, 4,4-bis(4-phenyl-1#2e3
-) riazol-2-”yl)stilbene titanium oxide (
approximately 0.3 μm) 0.5 parts by weight, and 1 part by weight of a charge control agent (Nippon Kayaku Kayacharge N-3).

The above product was treated in the same manner as Toner 1 of Example 1 to obtain Toner 2.

Ferrite carrier (Hitachi Metals KBN-200゜Li
-Mn type) 74 to 149 μm, when its surface was observed using a scanning electron microscope (SEM), there were no irregularities on the surface and no colored fine particles were observed. Therefore, developer 2 with a toner concentration of 4 was prepared by mixing this material and toner 2.

Example 6 Ephoxy resin (Yuka Shell Epoxy Ebiko) 10
07) 100 parts by weight, 2 parts by weight of polypropylene (Viscol 550P manufactured by Sanyo Chemical Co., Ltd.), 0.5 parts by weight of N-2-butyl-4-7 minona 7 arimide, 2 parts by weight of conductive zinc oxide (Hakusui Chemical 23-K) , Charge control agent (Hodogaya Chemical T)
P-302) 3 parts by weight.

The above product was treated in the same manner as Toner 1 of Example 1 to obtain Toner 3. However, instead of R972 as an external additive, 0.2 parts by weight of Aerosil@13 (treated with [7 nylinosilane) was added.

As a carrier, an iron powder carrier of 37 to 74 μm coated with a fluororesin was used. By using this iron powder carrier and toner 3, 9) a developer 6 having a toner concentration of 3% was obtained.

[Comparative example]

Developers 4 to 6 were prepared under the same conditions as the developer and toner described above except for the following.

(Developer 4) Instead of the coated magnetic carrier of Developer 1, a ferrite carrier (Ni-Zn type) 74 to 149μ is used as it is,
It was mixed with Toner 1 to form Developer 4 with a toner concentration of 4%.

(Developer 5) Developer 5 was prepared by using Solvent Yellow 210.5 parts by weight in place of the titanium oxide in Developer 2.

(Developer 6) N-2-butyl-4-amituna 7 arimide of developer 3 0
．． A developer not containing 5 parts by weight was designated as developer 6.

Image evaluation was also performed on the above-mentioned developers 2 and 4.5 using the same method as in Example 1. When ordinary copy paper was used, with developer 1.2, the image was not legible under visible light even after it was formed.

Developer 4 produced a sepia-colored image due to minute colored particles on the carrier surface, which was legible under visible light. With developer 5, a yellow image was obtained due to the dye and was readable under visible light. However, when yellow paper was used, it became somewhat difficult to read.

When the images obtained for Developers 1, 2, and 4.5 were observed under a mercury lamp and a black light, all were clear images without fogging.

・Furthermore, even after making 20,000 copies using Developers 1 and 2, I was still unable to get clear images with no fogging.

Regarding developer 6.6, similar evaluations were conducted using a commercially available copying machine (Sharp 5F7200) using an OPc photoreceptor. Developer 3 gave the same results as developer 1.2, but developer 6, which did not contain a fluorescent brightener, made the image unreadable even under ultraviolet light.

〔Effect of the invention〕

The present invention has the structure and operation as described above, and also provides a two-component developer consisting of a toner containing no colorant and a fluorescent whitening agent, and a carrier having a clean surface, and such a developer. An image forming method using an agent, and an image obtained by the present invention can be obtained using natural light, general J! ! Under iBA, it is mostly colorless and illegible, becoming legible only under ultraviolet irradiation. Therefore, the document having image information can be kept confidential and can be prevented from being copied again.

Claims (1)

[Scope of Claims] 1) A two-component developer comprising a toner for developing an electrostatic image and a magnetic carrier, wherein the toner contains at least a binding resin and a fluorescent brightener, and the magnetic carrier has a clean surface. A two-component developer characterized by: 2) The two-component developer according to claim 1, wherein the surface of the magnetic carrier is coated with a resin. 3) The two-component developer according to claim 1, wherein the surface of the magnetic carrier has undergone a melting process. 4) A step of forming a magnetic brush with a two-component developer consisting of a toner containing at least a binding resin and a fluorescent whitening agent and a magnetic carrier with a clean surface to develop an electrostatic image, and the obtained toner. transferring the image to a fixing medium;
It consists of the process of fixing the toner image transferred to the fixing medium by heat and/or pressure, and the formed image is colorless or white under visible light and has a color developing effect only when irradiated with ultraviolet light. An image forming method characterized by: