JPH0237364A - Photoconductive toner - Google Patents

Abstract

PURPOSE:To improve electric chargeability and photoconductivity and to enhance photosensitivity to infrared rays by dispersing zinc oxide, a colorant, and a specified pigment into a binder resin. CONSTITUTION:The binder resin contains, preferably, 100-300pts.wt. of zinc oxide as the photoconductive material per 100pts.wt. of the binder resin and as the sensitizing pigment a cyanine pigment represented by formula I, prefer ably, in an amount of 0.05-0.15wt.% of the zinc oxide, both dispersed into the binder resin. If the zinc oxide is added more than 300pts.wt., the produced toner deteriorates in chargeability, and if the zinc oxide is added less than 300pts.wt., the photoconductivity decreases, and if the cyanine pigment is added more than 0.15wt.% of the zinc oxide, chargeability of the toner is impaired, and if below 0.05wt.%, a sufficient sensitizing effect cannot be obtained, thus permitting the obtained toner to have superior photosensitivity to light in the near infrared region and the other infrared region, and to form a good image free from fog and sharp in contrast. In formula I, R is CH3, C2H5, CH2COOH, C2H4COOH, or CH2=CHCH2; X is I, Br, Cl, or ClO4; a group of formula II is a group of formula III or IV; and a group of formula V is a group of formula VI or VII.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a photoconductive toner, and more particularly to a photoconductive toner capable of forming images with high contrast.

(Prior Art and its Problems) In recent years, the use of photoconductive toner has attracted attention as a method of forming copied images without using a photoreceptor drum or the like. This photoconductive toner is a toner made by dispersing or dissolving a photoconductive material, a sensitizer, etc. in a binder resin and granulating it by a pulverization method or a spraying method, and the toner itself is It is said to have photoconductivity.

An example of an image forming method using this photoconductive toner is as follows.

That is, (i) a charged photoconductive toner is uniformly adhered and retained on a conductive substrate to form a toner layer, and (ii) imagewise exposure is performed.

(ij)) Copy paper or the like is superimposed on the toner layer, and corona discharge is applied from the back side of the copy paper to transfer the toner image.

(iv) Fixing the transferred toner image.

This is a method that sequentially performs these steps.

However, even in the above-described process, the difference in the amount of charge between the exposed and non-exposed areas in the latent image formed after exposure is small due to the fact that the photosensitivity of the photoconductive toner is generally low. Therefore, attempts have been made to improve the photosensitivity by corona charging the toner layer after it has been formed to improve the surface potential of the toner layer, but this has not necessarily been a solution.

Therefore, it is possible to increase the photoconductivity by increasing the amount of photoconductive substance in the toner, but the toner becomes difficult to charge and the photosensitivity decreases, making it impossible to obtain satisfactory results. Studies have been conducted on photoconductive toners that have good properties and photoconductivity and excellent photosensitivity.

On the other hand, image forming systems using photoconductive toner are not limited to analog image forming apparatuses, but have recently been considered for use in laser printers because the apparatus can be extremely miniaturized.

Conventionally, a gas laser was used as the laser light source for exposing the laser blink.
Semiconductor lasers are increasingly being used because they have many advantages, including excellent laser light intensity and stability, direct modulation, and low cost. Therefore,
The wavelength of this semiconductor laser light is 780 nm to 850 nm.
Since it is in the near-infrared to infrared region, research on photoconductive materials that show good sensitivity to this infrared light and research on dyes as aggravating agents to shift the angry light range to infrared light. is in progress.

For example, in JP-A No. 59-78358, zinc oxide is used as a photoconductive material, and as an aggravating dye, a linear alkyl group having a sulfonic acid or sulfonate as a functional group at the end is bonded to a nitrogen atom. It has been proposed to use a cyanine dye as a photoconductive layer of an electrophotographic photosensitive drum that exhibits good sensitivity to laser light.

However, the cyanine dye in the above-mentioned publication has sulfonic acid or a metal salt of sulfonic acid as a functional group, thereby increasing its adsorption to zinc oxide and efficiently aggravating it, thereby increasing the efficiency of photocarrier generation. However, although the photoconductive composition for photoconductor drums, in which the photoconductive layer is charged by corona charging, is effective to a certain extent, in the image forming process using photo IIa toner, it is difficult to uniformly charge the photoconductive layer on the conductive substrate. A photoconductive layer is formed from the adhered toner layer, and the electric charge of the photoconductive layer is caused by the electric charge of each toner forming the photoconductive layer. When a dye is used, the toner's chargeability and charge uniformity are inhibited, and the photosensitivity is reduced, resulting in a decrease in the contrast of the resulting image.

Furthermore, JP-A No. 58-59453 discloses that zinc oxide is used as a leading material, a specific cyanine dye is used as an aggravating dye, and an electron-affinity compound such as penduquinone or chloranil is dispersed as an aggravating agent. Photoreceptors having conductive layers have been proposed. However, 1. In the above publication, an electron-affinity substance is added to improve the adsorption of cyanine dye to zinc oxide, but similarly to the prior art, when the above-mentioned aggravation technique is applied to a photoconductive toner, the toner becomes Since the charging properties and charging uniformity are impaired, photosensitivity decreases, and images lacking in contrast can only be obtained.

In addition, conventionally, photoconductive toners must have both coloring properties and photoconductivity, so the amount of light irradiated to the photoconductive material is reduced by absorbing the irradiated light into the colorant contained therein. The selection of the colorant is also an important factor in the production of photoconductive toners, as this may reduce the photosensitivity or, conversely, the color of the photoconductive material may impede the sharpness of the hue of the toner itself.

Therefore, the present invention has been made in view of the above points, and an object of the present invention is to provide a photoconductive toner for use with laser light, which has good chargeability and photoconductivity, and has excellent photosensitivity to infrared light. Our goal is to provide the following.

Still another object of the present invention is to provide a photoconductive toner for use with laser light that does not cause fogging, has a clear hue, and is capable of forming images with good contrast.

(Means for solving the problem) According to the present invention, zinc oxide is used as a photoconductive material,
As aggravating pigments, the following - at the bottom of the ship (where R is CH3, C
xHs, CHiCOOtl, CJjCOQt (or, CHz-CHCHz, X is I,
Br, CI again I! CIO,.

A photoconductive toner in which the represented cyanine dye is dispersed in a binder resin makes it possible to achieve the objects of the present invention.

(Function) The present inventors have repeatedly conducted experiments on photoconductive compositions that act suitably on photoconductive toners, impart good photosensitivity to infrared light, and provide clear images with good contrast. Study was carried out. As a result, when the above-mentioned specific cyanine dye is dispersed together with zinc oxide in a toner, electron-affinity compounds are dispersed together, and highly polar functional groups are bonded, forcing the adsorption of the dye to zinc oxide. Even if you don't do it,
It generates photocarriers well and shows good photoconductivity, and the toner band t! They discovered that photosensitivity was significantly improved and images with excellent contrast could be formed without impeding charging uniformity.

In other words, the charging step in the image forming process using photoconductive toner involves charging individual toner particles and uniformly depositing the charged toner onto a conductive substrate.
The photoconductive layer formed by the charged photoconductive toner particles is different from the photoreceptor for electrophotography, which is composed of a general film-like photoconductive layer, in that the photoconductive layer is layered. Because the photocarrier is made up of a layer of particles, laser light can penetrate inside the layer, the particles can receive scattered light from all directions, and the electric field strength is large in the entire layer and in each particle. The cyanine dye and zinc oxide can be easily dispersed in the toner to provide good chargeability and photoconductivity without increasing the adsorption of the dye to zinc oxide. It is thought that this results in a marked improvement in photosensitivity and a fog-free, high-contrast image.

Note that the photosensitivity of the photoconductive toner in this specification is
It shows how efficiently the charge on the toner layer is erased by exposure (light irradiation) from the surface potential of the charged toner layer.
The amount of charge that disappears after seconds is expressed as the attenuation rate of the surface potential of the toner layer.

(Hereafter, margin) The present invention will be explained in detail below.

The cyanine dye used in the present invention either has a donor group bonded to it, or has a naphthalene structure in which the heterocycle is constituted by a sulfur atom and is adjacent to the heterocycle. As a result, the heterocycle is greatly polarized by the stacking structure of the methyl group as an electron-donating group or the sulfur atom with a large atomic radius and the benzene ring, making it possible to effectively spectral sensitize to infrared light. .

As the zinc oxide used in the present invention, commercially available zinc oxide can be used. The amount of zinc oxide added is 50 to 500, particularly 100 parts by weight, per 100 parts by weight of the binder resin.
The amount is preferably from about 300 parts by weight; if the amount of zinc oxide added exceeds this range, the resulting toner will have a decreased chargeability, and if it is less than the above range, the photoN and chargeability will decrease.

In addition, the above cyanine dye has a ratio of 0.01 to zinc oxide.
It is preferably from 0.5% by weight to 0.05% to 0.151% by weight; if it exceeds the above range, the charging properties of the toner will be inhibited, and if it is less than the above range, a sufficient sensitizing effect will not be obtained.

In addition, as the binder resin, styrene polymer, acrylic polymer, styrene-acrylic polymer 2, polyvinyl chloride, polyester, polyamide, polyurethane, epoxy resin, diallyl phthalate resin, silicone resin,
Examples include various polymers such as phenol resin, rosin-modified phenol resin, xylene resin, rosin-modified maleic acid resin, rosin ester, and petroleum resin.

These may be used singly or in combination of two or more in consideration of the photoconductive material used and the charging and fixing properties of the produced toner.

Furthermore, wax may be added to the toner of the present invention in order to prevent offset and improve fixing properties. As the wax, various waxes such as polyethylene wax, polypropylene wax, ethylene-propylene wax, and paraffin wax, and low molecular weight olefins such as olefin monomers having 4 or more carbon atoms are used.

As the colorant of the present invention, general pigments and dyes that are conventionally used as colorants for toners can be used, but even if they are added to the toner to develop color, they are resistant to infrared light. It is preferred to use a thermosensitive coloring dye that does not exhibit absorption together with a developer dye. This allows the toner to be colored in a desired color and does not inhibit the photoconductivity of the toner, making it possible to form images with good contrast and clear hue. As the heat-sensitive coloring dye, leuco dyes such as triphenylmethane leuco dyes, fluorane leuco dyes, spiropyran leuco dyes, rhodamine lactam leuco dyes, auramine leuco dyes, phenothiazine leuco dyes, dyes, etc. may be used alone or in combination. Used in combination with the above. A suitable example is:

Enilmen Leuco 3.3°-bis-(P-dimethylaminophenyl)phthalide, 3.3'-bis(P-dimethylaminophenyl)
-6-dimethylaminophthalide, 3.3°-bis(P-
dimethylaminophenyl)-6-dimethylaminophenyl, 3.3゛-bis(P-dimethylaminophenyl-6
-Medoxiphthalide, 4-hydroxy-4-dimethyl-
Aminotriphenylmethane lactone, 4,4'-bisdihydroxy-3,3°-bisaminotriphenylmethane lactone.

Fluone, leuco and 3-dimethylamino-5,7-dimethylfluorane, 3
-diethylamino-5,7-dimethylfluorane, 3-
Dimethylamino-6,7-dimethylfluorane, 3-cyclohexylamino-6-chlorofluorane, 3-dimethylamino-6-methoxyfluorane, 3,6-bis-
β-Methoxyethoxyfluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3.7-
Bisdiethylamine, nofluorane, 3-diethylamino-7-methoxyfluorane.

Spiropein diloico enemy: 8゛-methoxybenzoindolinospiropyran, 3-phenyl-8゛-methoxybenzoindolinospiropyran, 6"-chloro-8"-methoxybenzoindolinospiropyran, 5.6゛-dichloro-8゛-methoxybenzoindolinosbiropyran, 4.7.8''-trimethoxybenzoindolinosviropyran, Hensey β-naphthospiropyran, 1.3.3-) methyl-6゛-chloro8'-methoxyindolinopene Busviropyran-low mini/-mu, lactam of leucoanti-9-(p-nitroanilino)-3,6-bis(diethylamino)-9-xantyl-〇-benzoic acid,
2-(3,6-bis(die, thylamino)-9-(o-
lactam of chloroanilino)xanthylbenzoic acid.

O-sen 10 ico2.5-dichloro-N-phenylleucoauramine, 4
．． 4'-bisdimethylamino-3,4°-chlorophenylleucoauramine, 4,4'-bisdimethylaminopiperazine hydrol.

Fetch Zin-Leuco U Benzoyl leucomethylene blue, P-chlorobenzoyl leucomethylene blue, 3,4-diglolobenzoyl leucomethylene blue, P-methoxybenzoyl leucomethylene blue.

Further, as the color developer, an organic acidic substance that is solid at room temperature and heat-meltable is used. Typical examples of acidic substances include phenols and organic acids.

Specific examples include 4.4'-isopropylidene diphenol, 4.4'-methylene-bis(2,6'-di-tert-butylphenol'), and 4.4'-isopropylidene bis(2-chlorophenol). , 4.4″-isopropylidene bis(2,6-dichlorophenol), 4°4
°-isopropylidene bis(2-tert-butylphenol), 4.4°-cyclohexylidene diphenol, 2
．． 2'-thiobis(4,6-dichlorophenol), P
-Tertiary butylphenol, 3.4-dichlorophenol, 0.0°-dichlorophenol, 4-hydroxydiphenoxide, 2,2"-dihytohydroxybisphenol, 2.2"-methylenebis(4-chlorophenol)
, 2,6-dioxybenzoic acid, 1-oxyso-2-naphthoric acid, etc. can be added.

The amount of the colorant to be added can be appropriately selected depending on the hue and the colorant, but it is generally 5 to 60 parts by weight, particularly 10 to 30 parts by weight per 100 parts by weight of the binder resin. More specifically, the thermosensitive dye is 10 to 30 parts per 100 parts by weight of the binder resin.
In particular, 15 to 20 parts by weight of the color developer is preferably used, and the color developer is preferably used in an amount of 10 to 30 parts, especially 1 part by weight, per 100 parts by weight of the binder resin.
5 to 20 parts by weight are preferably used.

Further, magnetism can be appropriately imparted to the toner. The magnetic material to be added to the binder resin may be any material that exhibits magnetism or can be magnetized, such as metals and alloys that exhibit ferromagnetism such as iron, cobalt, nickel, and manganese, including ferrite and magnetite. used.

These magnetic substances can be used in an amount of 50 to 200 parts by weight per 100 parts by weight of the fixing resin.

In the production of the toner of the present invention, the solvent is directly poured into a solution in which the binder resin, zinc oxide, cyanine dye, colorant, and other additives added as necessary are dispersed or dissolved. After dispersion, it can be produced by a spray drying method, or by melt-kneading the binder resin, zinc oxide, cyanine dye, coloring agent and other additives, cooling and pulverizing it to a particle size of 3 to 20 μm, preferably 7 μm to 10 μm. A photoconductive toner is obtained.

Furthermore, for the purpose of improving various physical properties of the toner, silica, alumina, titanium oxide, etc. are used as fluidity modifiers, and silicone oil is added as a dispersion improver in an amount of 0.0% per 100 parts by weight of the toner composition. It can be used in an amount of 4 to 2 parts by weight.

The present invention will be explained in more detail below using experimental examples.

(Experiment example) 100 parts by weight of 5OX100 (manufactured by Seido Kagaku Co., Ltd., trade name) as zinc oxide, styrene-acrylic P as binder resin
A525 (manufactured by Mitsui Toatsu Chemical Co., Ltd., commercial product En) was mixed with 1000 parts by weight to prepare toners a, b, and c having an average particle size of 7 μm by a spray drying method.

Then, this toner was mixed with a ferrite carrier, triboelectrically charged, and introduced into a magnetic brush developing device for an electrophotographic copying machine, and the toner was uniformly adhered onto an aluminum substrate using this developing device.

Monochromatic light extracted from a monochromator was applied to the formed toner layer at 0. After 5 seconds of irradiation, the initial surface potential and the surface potential 1.5 seconds after irradiation were measured, and the attenuation rate of the surface potential (maximum surface potential attenuation rate) was measured using a co-reviewer connected to a digital oscilloscope. The results are shown in FIG.

As is clear from FIG. 1, when a linear alkyl group having sulfonic acid or sulfonic acid sodium salt is bonded to the nitrogen atom of the heterocycle, the photosensitivity of the toner is significantly reduced, especially in the vicinity of 780 to 800 nm. It can be seen that the attenuation rate for infrared to infrared light is about 20%, indicating that the photosensitivity is extremely low.

In addition, the following measurements were made in the same manner as the toner formulation described above. The results are shown in FIG.

As is clear from Figure 2, photoconductive toners using cyanine dyes that contain a sulfur atom in the heterocycle or a cyanine dye in which methyl as an electron donating group is bonded to the carbon atom of the heterocycle are It can be seen that the photoconductive toner exhibits higher photosensitivity to infrared light of 780 to 800 nm than the photoconductive toner using the cyanine dye.

In addition, a toner was prepared using the following cyanine dye (e) 6Hda 1 11H5 in the same manner as the above-mentioned toner formulation, and its irritability was measured in the same manner. The results are shown in FIG.

As is clear from Figure 3, a photoconductive toner using a cyanine dye in which a naphthalene structure is adjacent to a heterocycle is
It can be seen that this toner exhibits higher photosensitivity to infrared light of 780 to 800 nm than a photosensitive toner using a cyanine dye in which benzene rings are adjacent to each other.

The present invention will be explained in more detail below using Examples.

(Example 1) Zinc acid value, S○χ100 (manufactured by Seido Kagaku Co., Ltd., trade name) 100 parts by weight Cyanine dye, NK-2014 (manufactured by Nihon Yuko Shokuryo Co., Ltd., trade name) 0.1 part by weight (Mitsui Higashi) Manufactured by Tenkagaku Co., Ltd., trade name) 33 parts by weight black angry dye, TO-
11 (manufactured by Nippon Kayaku Co., Ltd., trade name) 5 parts by weight color developer, T
O-3A (manufactured by Nippon Kayaku Co., Ltd., trade name) 5 parts by weight toluene
After sufficiently dispersing and mixing 1000 parts by weight of the above mixture, spray drying was performed to reduce the average particle size to 1.
A toner of 0 μm was prepared. This toner was mixed with a ferrite carrier, triboelectrically charged, and introduced into a magnetic brush developing device for an electrophotographic copying machine, and the toner was uniformly adhered onto an aluminum substrate using this developing device.

Then, a monochromator is applied to this formed toner layer.
The initial surface potential and the surface potential 1.5 seconds after irradiation were measured by irradiating monochromatic light (800 nm) extracted from the When the surface potential attenuation rate) was measured, it was found to be 42%, indicating good photosensitivity similar to the above-mentioned good experimental example.

Furthermore, after uniformly adhering the toner to the aluminum base in the same manner, image exposure is performed using a semiconductor laser, and then transfer paper is stacked and a positive corona discharge is applied from the back side to transfer the toner, and the toner on the transfer paper is transferred. The image was fixed to form an image.

The resulting image was fog-free and a clear black image with excellent contrast was obtained.

(Example 2) In the above Example 1, NK-1 was used instead of cyanine dye.
A toner was prepared using 887CB (trade name, manufactured by Nippon Kanko Shokuryo Co., Ltd.) in the same manner as above, and the photosensitivity was measured and an image was formed using laser light.

The surface potential attenuation rate for monochromatic light of 800 nm is 41%.
It showed good photosensitivity.

Furthermore, the formed image was fog-free and a clear image with excellent contrast was obtained.

(Example 3) A toner was prepared in the same manner as in Example 1 except that blue swear dye CVL (manufactured by Nihon Tohoku Co., Ltd., trade name) was used instead of the black thermosensitive dye, and the photosensitivity was measured and the laser beam Image formation was performed using

The surface potential attenuation rate for monochromatic light of 800 nm and 800 m was 41%, indicating good photosensitivity.

Further, the formed image had a vivid blue hue, and a clear image with no blur was obtained.

(Example 4) A toner was prepared in the same manner as in Example 1 except that a red heat-sensitive dye TG-RED (manufactured by Nihon Tohoku Co., Ltd., trade name) was used instead of the black heat-sensitive dye, and the photosensitivity was measured. Image formation was performed using laser light, and the surface potential attenuation rate was 42% with respect to monochromatic light of 800 nm, showing good photosensitivity.

Furthermore, the formed image had a vivid red hue, and a clear image without any blurring was obtained.

(Example 5) A toner was prepared in the same manner as in Example 1 except that 5 parts by weight of a black oil-soluble dye Oil Black (manufactured by Orient Chemical Co., Ltd., trade name) was used instead of the black thermosensitive dye and color developer. We created a new model, measured its photosensitivity, and formed an image using laser light.

Surface potential attenuation rate for 800 nm monochromatic light is 38%
Met.

In addition, a clear image with no black blemish was obtained.

(Comparative Example 1) In Example 1, as a cyanine dye, NK-1967 (manufactured by Nippon Kanko Shiki Co., Ltd., trade name: ) A toner was prepared in the same manner as above, and the photosensitivity was measured and an image was formed.

The surface potential attenuation rate for monochromatic light of 800 nm was as low as 19%.

In addition, the obtained image was a defective image that had looseness and lacked sharpness.

(Effects of the Invention) According to the present invention, a photoconductive toner having excellent photosensitivity to near-infrared and infrared light can be obtained, and a good image with good contrast can be formed without fogging. Furthermore, when swear dyes are selected as colorants, toner images with vivid hues can be obtained.

[Brief explanation of the drawing]

FIGS. 1, 2, and 3 are diagrams showing the relationship between the wavelength of light irradiated to the toner and the photosensitivity (surface potential attenuation rate).

Claims (1)

[Claims] (1) In the binder resin, zinc oxide, colorant, and the following general formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (However, R is CH_3, C_2H_5, CH_2COO
H, C_2H_4COOH, or CH_2=CHC
H_2, There are tables, etc. ▼ means ▲ mathematical formulas, chemical formulas,
There are tables, etc. ▼ or ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼) A photoconductive toner in which the expressed pigment is dispersed.