JPS5919329B2 - Electrophotographic materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improving the electrophotographic properties of an electrophotographic material containing titanium dioxide as a main photosensitive agent, and particularly to suppressing pre-exposure fatigue.

In electrophotography, the surface of a photosensitive material is uniformly charged by corona discharge, imagewise exposed to attenuate the charge in the exposed area to form an electrostatic latent image, and then an electroscopic colored toner is applied to the electrostatic charge. It is attached onto a latent image to create a visible image.

It is also known that titanium dioxide can be used as the main photosensitive agent, but titanium dioxide, which generally has relatively excellent electrophotographic properties, often suffers from large pre-exposure fatigue. This is one of the factors that hinders its practical use. Pre-exposure fatigue is a change in electrophotographic properties that occurs when an electrophotographic photosensitive material is exposed to light before being charged and developed, and is usually caused by a delay in the charging start time, a decrease in the rate of increase in charging potential, or a decrease in the saturation charging potential. Undesirable changes occur, such as a decrease in the light decay rate.

When creating multicolor prints or color images that involve repeated charging, exposure, and development, the effects of pre-exposure fatigue cannot be avoided.
If fatigue cannot be controlled within a certain limit, the color of the image will become cloudy,
This results in deterioration of color image development, deterioration of continuous gradation, and increased contrast of images. After many attempts to suppress pre-exposure fatigue of titanium dioxide, it was found that by adding catechol and its derivatives, changes in charging characteristics and photosensitivity caused by pre-exposure can be significantly reduced. Ta.

The present invention is an electrophotographic photosensitive material having a photosensitive layer mainly composed of titanium dioxide and a resin binder on a conductive substrate, the photosensitive layer having the general formula xn.

OH (wherein, The present invention is an electrophotographic light-sensitive material containing at least one compound represented by amino-substituted alkyl or unsaturated alkyl, where n is an integer of 0 to 2) and a salt thereof.

The manufacturing history of titanium dioxide as a main photosensitive agent contained in the photosensitive layer does not matter as long as it is suitable for electrophotography, but as has been conventionally recognized, it may contain colored impurities, raw materials, or It is better to have fewer impurities derived from additives.

However, Zn, Ca, Mg, Li, Ba or Sr etc.
．． It is known that the presence of 01 to 5 mol% in the crystal structure of titanium oxide improves the electrophotographic properties. It can be added during the production of titanium dioxide to produce titanium dioxide with excellent electrophotographic properties, which can be used in the present invention. It is also possible to replace a part of titanium dioxide with zinc oxide and use the mixture. In the photosensitive material of the present invention, at least one kind of catechol and its derivatives is present in the photosensitive layer together with the titanium dioxide.

Here, a catechol derivative is one in which catechol further has 1 to 2 nuclear substituent atoms or groups, these substituents are halogen atoms, and the substituents include hydroxyl group, nitro group, amino group, formyl group, It is a carboxyl group, an alkoxy group, an alkylcarbonyl group, an alkoxycarbonyl group or a carboxyalkyl group. Further, the alkyl moiety in the group may be a halogen- or amino-substituted alkyl, or an unsaturated alkyl, and the carboxylic acid or amino group moiety may form a salt. The amount of the catechols added may be 1 mol % or less based on titanium dioxide, but no substantial effect will be seen if it is 0.001 mol % or less.

Preferably it is added in an amount ranging from 0.005 to 0.5 mol%. Catechols may be present on the surface of titanium dioxide particles by dissolving them in water or a solvent, adding them to titanium dioxide in advance, and then evaporating the solvent. It may be added when preparing the coating liquid. Although the mechanism of action of catechols is still not clear, the effect of suppressing pre-exposure fatigue is extremely remarkable, and almost eliminates the influence of pre-exposure on both charging characteristics and photosensitivity. Further, this effect is not substantially affected by other additives present in the photosensitive layer, such as sensitizing dyes, metal soaps, amines, etc., and does not substantially change depending on the type of binder resin. Furthermore, catechols have the effect of suppressing pre-exposure fatigue, as well as dye sensitizing aids,
A side effect is also seen as a chargeability improving aid. In addition to the above, the electrophotographic material of the present invention can be prepared by conventional methods.

That is, a photosensitizer is dispersed in a resin binder at a ratio of 35 to 65% by volume, and this is deposited on a conductive substrate in a generally 10μ
It is coated to a thickness of ~30 μm and dried to form a photosensitive material, at which time the above-mentioned catechols are added to the coating solution. Usually, when kneading titanium oxide and a resin binder, one type or a combination of two or more types of various processing agents for improving electrophotographic properties are used. For example, dyes such as anthraquinones, ptalenes, xanthines, methines, triphenylmethanes, azos, azines, and oxazines are used as spectral sensitivity improvers, and amines, organic Acids, silane coupling agents, resins, metal soaps,
Alcohols having 6 or more carbon atoms can be used, and metal soaps, organic acids, phenols, amines, silane coupling agents, resins, alcohols having 6 or more carbon atoms, etc. can be used as charging property improvers. Such a processing agent may be simply added and kneaded when titanium oxide and the resin binder are kneaded, but due to the characteristics of electrophotography, it is preferable to first strongly adsorb the processing agent on the surface of the pigment particles and then knead with the resin binder. It will be done. That is, before kneading the treatment agent and titanium dioxide ~
After kneading, the temperature is usually 90°C or higher, preferably 120 to 25°C.
If the treatment agent is heated at 0°C for 1 to 4 hours, preferably 2 to 3 hours, then kneaded with a resin binder, coated, and dried at a temperature lower than the heating temperature, the treatment agent will be tightly adsorbed and retained on the surface of the pigment particles. In addition to providing improved effects beyond those of conventional processing agents, the effects of improving other photographic properties may also be improved. As the resin binder, a resin having film-forming properties and high electrical insulation properties can be appropriately selected and used. For example, acrylic resin, alkyd resin, polyester resin, vinyl resin, polyurethane resin, various natural resins, synthetic rubber, amino resin, polyolefin resin, etc. can be used. The conductive base material may be anything that has higher conductivity than the photoconductive layer, such as paper or cloth coated with a conductive substance commonly used in electrophotography, a metal sheet, or a plastic sheet coated with metal. , use paper laminated with metal foil, etc. The light-sensitive material of the present invention has a high degree of whiteness due to the excellent pigment properties of titanium dioxide, and can produce good images with fine grains.

Furthermore, titanium dioxide has extremely excellent continuous tone reproducibility and can produce images comparable to silver halide photography, and although it has the great advantage of being applicable to color prints, it is not put into practical use due to the effects of pre-exposure fatigue. However, this problem has been solved by the present invention, and as a result, the photosensitive material of the present invention can be said to be especially suitable for color printing. Example Titanium tetrachloride was hydrolyzed, and the resulting hydrated titanium oxide precipitate was washed, dried, calcined, and ground to obtain titanium dioxide.

This titanium dioxide was placed in a zinc naphthenate solution (containing 0.3% zinc based on titanium dioxide) of Isopa G (manufactured by Etsuo Chemical Co., Ltd., isoparaffinic hydrocarbon).
After stirring at 1700C for 30 minutes, titanium dioxide was filtered off and dried at 140C to obtain titanium dioxide for electrophotography.The additive for suppressing pre-exposure fatigue of the present invention was added to the titanium dioxide in advance. Alternatively, it can be added when preparing a photosensitizer coating solution.

Titanium dioxide was treated as follows. (1
) For the control and boiled samples 1, 6, 7, 8, 11 and 16, only the sensitizing dye was added according to a conventional method.

That is, an ethanol solution containing 0.0024 g of each of the dyes dipromfunoleorescein and NK-1194 (manufactured by Nippon Kanko Shiki Kenkyusho; cyanine dye) was added to 8 g of the titanium dioxide to form a paste, and the solvent was evaporated. I let it happen. (2) Other than the above, in addition to the ethanol solvent of the sensitizing dye, 8 g of titanium dioxide is added with an ethanol solution or an aqueous solution containing 0401 mol% of TiO2 as an additive to form a paste, and then the solvent and The water was evaporated.

Using the thus treated titanium dioxide, a photosensitizer coating solution was prepared and applied to a substrate in the following manner to produce an electrophotographic photosensitive material.

(1) Control, f). 2 to 5, 9, 10, 12 to 15, and 17 to 20, 8 g of the treated titanium dioxide was mixed with 40 g of glass beads, 6.4 g of binder resin solution (Arocet 5804XC, manufactured by Nippon Aroichi Chemical Co., Ltd.), and 8 ml of xylene. The paste was placed in a container and shaken for 5 minutes using a quick mill, and the resulting paste was applied to aluminum foil using a No. 40 wire applicator, left to stand for 15 minutes, and then dried at 100° C. for 10 minutes.

(2) Other than the above, xylene 7.5ml and additive 0.0
Same as above except that 0.5 ml of xylene solution containing 1 mol % was used.

The thus obtained photosensitive material was left in a dark place for 48 hours or more, and then its electrophotographic properties were measured.

Charging curves and dark decay curves were drawn by the turntable method (dynamic method) using a paper analyzer manufactured by Gekiguru Denki SP-428, and the number of seconds until the saturation potential was reached (rise seconds), Potential reached by charging. (
Charging property) and potential 20 (dark retention property) after being left in the dark for 20 seconds after charging were measured. Separately, after charging to 300V with a scorotron charger, light irradiation was performed while measuring the potential with a surface electrometer (Kawaguchi Electric Co., Ltd. SS-30), and the potential was 5 minutes from the potential (300) immediately before exposure. 1
The time required to attenuate to (60) t1/5 (light attenuation =
photosensitivity) was measured.

For exposure, white light from a tungsten bulb with an illumination intensity of 1,000 lux was separated into blue, green, and red by a dichroic filter. The results are shown in the table below. In the charging characteristics column, the upper row shows the value when charged as is, and the lower row shows the value when pre-exposure was given for 4 seconds at 30,000 lux using a tungsten bulb. In the photosensitivity column, the upper row shows the values when blue, green, and red were tested individually, and the lower row shows the values when blue, green, and red were tested sequentially on the same sample.

Claims (1)

[Scope of Claims] 1. An electrophotographic photosensitive material having a photosensitive layer mainly composed of titanium dioxide and a resin binder on a conductive substrate, the photosensitive layer having a general formula ▲ mathematical formula, chemical formula, table, etc. ▼ (wherein, or amino-substituted alkyl, unsaturated alkyl, n is an integer of 0 to 2), and at least one salt thereof.