DE3821628A1 - Photosensitive element containing a purified organic pigment - Google Patents

Abstract

Photosensitive elements having a photosensitive layer, which comprises an organic pigment as charge-generating material on an electrically conductive substrate, the organic pigment containing 2.5 % by weight or less of volatile substances, 0.2 % by weight or less of ash and 150 ppm or less of sodium, the charge-generating material being obtainable by repeated washing with water and organic solvents, show outstanding, especially electrophotographic, properties.

Description

Technological background

The invention relates to a photosensitive element which as charge generating material is a purified organic Contains pigment.

As photosensitive materials for education Photosensitive elements are inorganic photoconductive Materials known as selenium, cadmium sulfide or zinc oxide become.

These photosensitive materials are numerous share on; the charge loss in the dark is low, the electrical charge can be quickly removed on exposure be, and the like. On the other hand, however, there are after parts; so z. B. in photosensitive selenium elements Manufacturing and handling difficult, because of their low resistance to heat and mechanical Bumps as well as because of their high production costs. A Photosensitive element based on cadmium sulfide  or zinc oxide also has disadvantages, e.g. B. its unstable sensitivity when used in an environment with high humidity and less stability depending from the time due to the deterioration of as dyes added sensitizers by corona discharge and "Fa thing "on exposure.

On the other hand, numerous types of organic photoconductors capable materials such as polyvinyl carbazole are proposed been. These are organic photoconductive materials superior with regard to their film-forming properties, their light weight and the like, but inferior in in terms of sensitivity, durability and durability compared to organic photoconductive materials.

There have been various studies and developments made to the above drawbacks and problems to solve. So was a functionally divided laminate type or dispersion type photosensitive member Type proposed in which the charge generating and the Charge transport function on different layers or different dispersed materials were shared. The functionally divided photosensitive Element can be extremely efficient regarding its electrophotographic properties such as chargeability, Sensitivity, residual potential, fatigue resistance to Copies and repetitions should be given the appropriate materials can be selected from different fabrics. Farther can the functionally split photosensitive member in an easy and economical way by means of simple Processes are made, e.g. B. by coating, and with no restrictions on a range of light temp sensitive wavelengths can be controlled as appropriate charge generating materials can be selected. Typical examples of such charge generating materials are organic pigments or dyes like  Phthalocyanine pigments, cyanine pigments, polycyclic Quinone pigments, perylene pigments, perinone pigments, indigo color substances, thioindigo dyes, squarain compounds and the same, still inorganic materials like selenium, Selenium arsenic, selenium tellurium, cadmium sulfide, zinc oxide, amorphous Silicon and the like.

There are different types of photosensitive elements the organic pigments or dyes as charge-generating Contain materials known. Charge generating materials have a big impact on everyone electrophotographic properties of photosensitive Elements.

Brief description of the invention

The invention is directed to a photosensitive member tet, the highly sensitive charge generating material contains.

The invention is further based on photosensitive elements directed to all electrostatic properties properties, especially sensitivity and charge retention have excellent characteristics.

The invention relates to a photosensitive element a photosensitive layer containing an organic pigment as a charge-generating material on an electrically conductive capable substrate, wherein the organic pigment 2.5% by weight or less of volatile substances, 0.2% by weight or less of ash and 150 ppm or less of sodium contains.  

Detailed description of the invention

It was found that the volatile content, Ashes and sodium in organic pigments, which as charge-generating materials are used, a large Influence on the entire electrostatic properties of has photosensitive elements.

The invention is based on this knowledge and is based on a photosensitive element with a photosensitive Layer that contains an organic pigment as a charge-generating Comprises material on an electrically conductive substrate, directed, the organic pigment 2.5 wt .-% or less volatile substances, 0.2% by weight or less Contains ashes and 150 ppm or less of sodium.

The invention is in particular by an organic pigment, that is preserved in a charge transport layer draws.

Different types of organic pigments known per se can be used for the subject of the invention. The Organic pigments can be those that can be synthesized or are commercially available, e.g. B. bisazo pigments, Triarylmethane pigments, thiazine dyes, oxazine dyes, Xanthene dyes, cyanine dyes, styryl dyes, Pyrylium dyes, azo pigments, quinacridone pigments, indigo pigments, perylene pigments, polycyclic quinone pigments, Bisbenzimidazole pigments, indanthrone pigments, Squalylium pigments, phthalocyanine pigments and the like.

To a photosensitive element with an improved Sensitivity and retention, and the like obtained, the organic pigment is preferably by means of a appropriate process such as washing, recrystallization or the like cleaned. Washing is special  preferred because it is simple and economical to carry out. In the washing process, the pigments are, for example, in an amount of 1 part by weight with sufficient z. B. 100 to 5000 parts by weight, preferably 300 to 2000 parts by weight and particularly preferably with 500 to 1000 parts by weight deionized or distilled water three to twenty times washed at a temperature of 40 ° C or more; then 1 part by weight of the pigments washed with water is in sufficient with 100 to 5000 parts by weight, preferred 300 to 2000 parts by weight and particularly preferably 500 to 1000 parts by weight of organic solvents such as tetrahydrofuran or washed with dimethylformamide. If you use the pigments a smaller amount of solvent, you should wash them wash more often. If the pigments are washed less often they should be used with larger amounts of solvent getting washed. The preferred relationship between the crowd of the solvent and the number of washing stages is as follows: the total amount of solvent for washing (the amount of for the single wash, multiplied by the number of Washing steps) is at least 1500 times the amount of Pigment in parts by weight; the amount of solvent used The one-time wash is 100 to 5000 times the amount of pigment in parts by weight, and the number of Washing steps are at least 3. After washing the pigments in a vacuum at a temperature of 80 ° C or more dried to the level of impurities in the form of volatile substances to 2.5% by weight or less Ash content to 0.2% by weight or less and the sodium content down to 150 ppm or less.

The content of volatile substances is due to the JIS K 0067 2.3, which is described below; a sample is weighed and placed on a flat plate set size whose weight is known. The plate is placed in an oven, if necessary, the Surface of the sample is placed flat. Then will heated to a temperature of 105 to 110 ° C if the  Temperature is not specifically prescribed in one Desiccator dried and then weighed.

Unless otherwise noted, there is silica gel as a desiccant in the desiccator. The cooling time is 20 up to 40 min unless otherwise stated.

The content (V) of volatile substances (%) is calculated according to the following formula:

V = 100 - C ,

where C = 100 (W ₂ / W ₁),
where C is the non-volatilized fraction (%), W ₁ the weight of the sample (g) and W ₂ the weight of the sample (g) after the volatilization.

The ashes are determined on the basis of JIS K 0067 2.4, the is described below; a sample is weighed and in a crucible of sufficient size, for example heated on a hot plate. After almost complete decomposition the sample with volatilization and almost complete Charring will gradually increase the temperature to the specified Temperature range increased to incinerate the sample. The Sample is cooled in a desiccator and then weighed.

The ashing is preferably done in an electric furnace performed without a lid on the crucible; however one can use a gas flame if the heating method is not particularly is prescribed. If the sample is strong with a gas flame is heated, it is advantageous to loose one on the crucible Put on the lid. If it is difficult to get a sample ash, the sample is first ashed, then The ashes are extracted with hot water ash that is not dissolved in hot water is ashed again;  then the solution with the extract is evaporated and dried, followed by vigorous heating at the on given temperature together with that from the undissolved Residue obtained ash.

The ash content (D) (%) is calculated according to the following formula:

D = 100 (W ₂ / W ₁)

where D is the ash content (%), W ₁ the weight of a sample (g) and W ₂ the weight of the sample (g) after ashing or strong heating.

The sodium content is determined using analytical methods such as Atomic absorption spectrometry, the spectrochemical emissi analysis or the like.

If the volatile content exceeds 2.5% by weight it can lead to poor dispersion properties, poor coating properties, the formation of holes in the photosensitive layer, an uneven one Formation of the photosensitive layer and poor Stand properties of the coating solution due to aggregation of the pigments.

If the amount of ash is more than 0.2 wt%, under Exclusion of halogen atoms and the like, which the chemical Form structure of an organic pigment, it can too poor sensitivity, worsened charge retenti on properties, an increase in the decay of the surface potential in the dark and significantly deteriorated Repeat properties result.

If the sodium content is more than 150 ppm, it can increase a deterioration in the charge retention properties, an increase in the decay of the surface potential in the  Dark and significantly deteriorated repetitiveness lead.

Organic pigments must therefore have a volatile content Substances of 2.5% by weight or less, on ashes of 0.2% by weight or less and a sodium content of 150 ppm or less to have a good photosensitive Element received. The organic pigments of the invention cause Excellent sensitivity, such as dispersion and Coating properties.

The photosensitive member of the invention can be manufactured be by using a coating solution that the pre called organic pigments and binder resins in one Contains solvent, dispersed by various methods and dries e.g. B. by means of dip coating, Spray coating, spinner coating, spatula coating, Roll coating, wirebar coating and the like an electrically conductive substrate.

The photosensitive element of the invention can in particular be made by using a photosensitive Coating solution containing the aforementioned organic pigments and binder resins spread and dry; suitable bandage medium resins are e.g. B. thermoplastic binders as sown polyester resins, polyamide resins, acrylic resins, ethylene Vinyl acetate copolymers, ionic cross-linked Olefin copolymers (ionomers), styrene-butadiene block copolymers, Polyallylates, polycarbonates, vinyl chloride-vinyl acetate Copolymers, cellulose esters, polyimide and styrene resins; thermosetting binders such as epoxy resins, urethane resins, Silicone resins, phenolic resins, melamine resins, xylene resins, Alkyd resins and thermosetting acrylic resins; light curing resins; photoconductive resins such as poly-N-vinylcarbazole, polyvinylpyrene and polyvinylanthracene, mixtures thereof, and the like in a solvent for dispersion or dissolution, e.g. B. Alcohols such as methanol, ethanol, isopropanol and the like;  Ketones such as acetone, methyl ethyl ketone, cycle hexanone or same; Amides such as N, N-dimethylformamide, N, N-dimethylacetamide or similar; Sulfoxides such as dimethyl sulfoxide and the like chen; Ethers such as tetrahydrofuran, dioxane, Monomethyl ethylene glycol ether and the like; Esters like Methyl acetate, ethyl acetate or the like; aliphatic Halogenated hydrocarbons such as chloroform, methylene chloride, Dichlorethylene, carbon tetrachloride, trichlorethylene and the like; aromatic hydrocarbons such as benzene, Toluene, xylene, ligroin, monochlorobenzene, dichlorobenzene and the like, which applied to electrically conductive substrates will wear.

For the production of a functionally divided Photosensitive element with a charge-generating Layer and a charge transporting layer on one electrically conductive substrate is first the charge generating layer in a thickness of 0.01 to 2 μm, preferably 0.01 to 1 µm on an electrically conductive Substrate by spreading and drying one Generated coating solution; the coating solution will manufactured by using an organic charge generator Pigment distributed in a solution of a binder resin, so that the ratio of the charge generating pigment to that Binder resin in particular 5: 1 to 1: 5 (in parts by weight) is. Then on the charge generating layer the charge transport layer is formed by a solution of a charge transport material and one Binder resin, dissolved in a suitable solvent, spreads and dries. The thickness of the charge transport layer is 3 to 40 µm, preferably 5 to 25 µm. It is before that the content of the charge transport material in the charge-transporting layer 0.02 to 2 parts by weight, preferably 0.5 to 1.2 parts by weight per 1 part by weight of the Binder resin is.  

The charge transport material can be combined with a further charge-transporting material or more respectively. The use of binders is not required Lich, if the charge transport material is a high poly mer that can itself serve as a binder.

The photosensitive element can be manufactured by the charge on an electrically conductive substrate transport layer and then on the charge transport layer applies the charge generating layer.

Typical examples of charge transport layers are

Hydrazone, pyrazoline, styryl, triphenylmethane, oxadiazole, Carbazole, stilbene, enamine, oxazole, triphenylamine, Tetraphenylbenzidine and azine compounds and the like, in particular carbazole, N-ethylcarbazole, N-vinylcarbazole, N-phenylcarbazole, tetracene, chrysene, pyrene, perylene, 2-phenylnaphthalene, azapyrene, 2,3-benzene chrysene, 3,4-benzopyrene, fluorene, 1,2-benzofluorene, 4- (2-fluorenylazo) resorcinol, 2-p-anisolaminofluorene, p-diethylaminoazobenzene, cadion, N, N-dimethyl-p-fluorenylazoaniline, p- (dimethylamino) stilbene, 1,4-bis (2-methylstyryl) benzene, 9- (4-diethylaminostyryl) anthracene, 2,5-bis (4-diethylaminophenyl) -1,3,5-oxadiazole, 1-phenyl-3- (p-diethylaminostyryl) -5- (p-diethylaminophenyl) -py razolin, 1-phenyl-3-phenyl-5-pyrazolone, 2- (m-naphthyl) -3-phenyloxazole, 2- (p-diethylaminostyryl) -6-diethylaminobenzoxazole, 2- (p-diethylaminostyryl) -6-diethylaminobenzothiazole, bis (4-diethylamino-2-methylphenyl) phenylmethane, 1,1-bis (4-N, N-diethylamino-2-ethylphenyl) heptane, N, N-diphenylhydrazino-3-methylidene-10-ethylphenoxazine, N, N-diphenylhydrazino-3-methylidene-10-ethylphenothiazine, 1,1,2,2-tetrakis (4-N, N-diethylamino-2-ethylphenyl) ethane, p-diethylaminobenzaldehyde-N, N-diphenylhydrazone,  p-diphenylaminobenzaldehyde-N, N-diphenylhydrazone, N-ethylcarbazole-N-methyl-N-phenylhydrazone, p-diethylaminobenzaldehyde-N-alpha-naphthyl-N-phenylhydrazone, p-diethylaminobenzaldehyde-3-methylbenzothiazolinone-2-hydrazone, 2-methyl-4-N, N, -diphenylamino-beta-phenylstilbene, alpha- Phenyl-4-N, N-diphenylaminostilbene

and the same. These Charge transport materials can be used individually or in Mixture can be used.

A photosensitive member thus formed can be an adhesive layer or a barrier layer between the Have substrate and the photosensitive layer. Appropriate Examples of these layers are polyimides, polyamides, Nitrocellulose, polyvinyl butyral, polyvinyl alcohol, aluminum oxide or the like. The thickness is preferably Layer 1 µm or less.

Examples of an electrically conductive substrate of the Photosensitive elements of the invention are sheets or Drums made of foils or plates of metals such as copper, Aluminum, silver, iron, nickel or the like. Electrical Conductive substrates can be deposited or electroless Plating the aforementioned metals on a plastic film lie or the like in a vacuum or by coating or Deposition to form a layer of an electrical conductive material such as a conductive polymer, indium oxide, tin oxide or the like on a paper web or a plastic film.

The photosensitive member of the invention cannot be use only in copiers for electrophotography, but also in the field of laser printers, CRT printers, of systems for the production of plates for the electrical photography, the photoconductive toner and the like.  

The invention is in the following based on preferred management examples explained in more detail.

Example 1

First, a bisazo pigment of the following formula was prepared represents:

The unpurified pigment obtained was washed five times with water and then five times with DMF under the following conditions washed:

• The weight ratio of deionized pigment to water was 500: 1;
• The temperature of the deionized water was 50 ° C;
• The weight ratio of DMF to pigment was 500: 1;
• The temperature of the DMF was 30 ° C.
• The cleaned pigment was at 110 ° C for 5 h under vacuum conditions dried.

The percentage of volatile substances, the ash content and the Sodium levels were determined with the following results were obtained:  

• Volatile content 1.0% by weight
• Ash content 0.05% by weight
• Sodium content 53 ppm.

1 part by weight of the pigment obtained, 1 part by weight of polyester resin (Vylon 200, Toyobo K.K.) and 90 parts by weight Cyclohexanone was placed in a sand mill and trained formation of a photosensitive coating composition dispersed, which are applied to an aluminum substrate and to form a charge generating layer with a Thickness of 0.3 microns was dried.

The charge generating layer was further covered with a solution the hydrazone compound of the formula

and 10 parts by weight of polycarbonate resin (Panlite K-1300, Teÿin K.K.) in 150 parts by weight of tetrahydrofuran to form a Charge transport layer with a thickness of 15 microns after the Dried coated using a photosensitive element received.

Examples 2 to 3

It became a photosensitive element in a similar manner as produced in Example 1, except that Pigments containing volatile substances, one Ash content and a sodium content according to the following  Information obtained according to the following conditions and dried, were used.

Example 2

• The weight ratio of deionized water to pigment was 500: 1;
• The temperature of the deionized water was 50 ° C;
• The weight ratio of DMF to pigment was 500: 1;
• The temperature of the DMF was 30 ° C;
• The temperature when drying in vacuo was 10 ° C;
• The drying time was 5 hours.

Example 3

• The weight ratio of deionized water was 500: 1;
• The temperature of the deionized water was 40 ° C;
• The weight ratio of DMF to pigment was 500: 1;
• The temperature of DMF was 30 ° C;
• The temperature when drying in a vacuum was 80 ° C .;
• The drying time was 3 hours.

The photosensitive element thus obtained was inserted into a commercially available electrophotographic copier (EP-450z, from Minolta Camera KK) and tested by applying a voltage of -6 kV to the direct current source in order to determine the initial surface potential V ₀ (V) required for the Reduce V ₀ to half of V ₀ required exposure amount [ E ^1/2 (lux sec)], and determine the decrease rate of the potential DDR ₅ (%) when the element is left standing in the dark 5 sec after loading.

Comparative Examples 1 to 4

It became a photosensitive element in a similar manner as produced in Example 1, except that Pigments with the following levels of volatile substances, Ash and sodium were used:

Example 4

First, a bisazo pigment of the following formula was prepared represents:

The unpurified pigment obtained was used five times deionized water and then five times with DMF the following conditions:

• The weight ratio of deionized water to pigment was 800: 1;
• The temperature of the deionized water was 40 ° C;
• The weight ratio of DMF to pigment was 500: 1;
• The temperature of the DMF was 30 ° C.
• The purified pigment was at 80 ° C under vacuum conditions Dried for 3 hours.

The content of volatile substances, the ash content and the Sodium levels were determined with the following results were obtained:

• Volatile substances 0.8% by weight,
• Ash 0.03% by weight,  
• Sodium content 80 ppm.

1 part by weight of the pigment obtained, 1 part by weight of polyester resin (Vylon 200, Toyobo K.K.) and 90 parts by weight Cyclohexanone was placed in a sand mill and dispersed, being a photosensitive coating composition received, which applied to an aluminum substrate and ge was dried, a charge generating layer with a Thickness of 0.3 microns was obtained.

The charge generating layer was further covered with a solution of 10 parts by weight of a stilbene compound of the following formula

10 parts by weight of a polyallylate resin (U Polymer, Fa. Yunichika K.K.) in 150 parts by weight of tetrahydrofuran formation of a charge transport layer with a thickness of 15 microns coated after drying, one received photosensitive element.

Comparative Examples 5 to 7

A photosensitive member was made in a similar manner to that in Example 4 prepared, except that Pigments with volatile substances, ashes and Sodium were used according to the following schedule:  

Example 5

TiO phthalocyanine was obtained by hydrolysis of TiCl₂ phthalocyanine produced.

The unpurified pigment obtained was used five times deionized water and then three times with DMF according to washed under the following conditions:

• The weight ratio of deionized water to pigment was 1000: 1;
• The temperature of the deionized water was 60 ° C;
• The weight ratio of DMF to pigment was 500: 1;
• The temperature of the DMF was 40 ° C.
• The purified pigment was dried under vacuum conditions at 110 ° C for 5 hours.

The percentage of volatile substances, the ash content and the Sodium levels were determined with the following results were obtained:

• Volatile substances 0.3% by weight,  
• Ash 0.07% by weight,
• Sodium content 35 ppm.

1 part by weight of the pigment obtained, 1 part by weight of polystyrene resin (Elastyrene, Dainippon Ink K.K.) and 90 parts by weight Cyclohexanone were placed in a sand mill and added to a dispersed photosensitive coating composition, which to form a charge-generating layer a thickness of 0.3 microns applied to an aluminum substrate and was dried.

The charge generating layer was further covered with a solution of 10 parts by weight of the enamine compound represented by the following formula

and 10 parts by weight of polycarbonate resin (Panlite K-1300, Teÿin Kasei K.K.) in 150 parts by weight of tetrahydrofuran for training a charge transport layer with a thickness of 20 microns dry coated, using a photosensitive Element received.

The photosensitive element thus obtained was inserted into a commercially available electrophotographic copier (EP-450z, from Minolta Camera KK) and tested with the application of a voltage of -6 kV to the direct current source, to determine the original surface potential V ₀ (V), the exposure quantity required for the decrease of V ₀ to half of V ₀ [ E _1/2 (lux. sec)] and the decay rate of the potential DDR ₅ (%) when the element is left standing in the dark 5 sec after loading.

The in Examples 1 to 5 and Comparative Examples 1 Results obtained through 7 are shown in Table 1. Wei furthermore, Table 1 shows the dispersion properties of the Dispersions or solutions in the preparations for the photosensitive elements were used.

In Table 1, the symbol "○" means "good", the symbol "*" means "almost good" and the symbol "×" means "not good".  

Table 1

Claims (9)

1. Photosensitive element with a photosensitive layer which contains an organic pigment as a charge-generating material on an electrically conductive substrate, characterized in that the organic pigment contains 2.5% by weight or less of volatile substances, 0.2% by weight. % or less of ash and 150 ppm or less sodium. 2. Photosensitive element according to claim 1, characterized characterized in that the organic pigment Bisazo pigment or a phthalocyanine pigment.   3. Photosensitive element according to claim 1, characterized in that the organic pigment is a bisazo pigment of the formula is. 4. Photosensitive element according to claim 1, characterized in that the organic pigment is a bisazo pigment of the formula is. 5. Photosensitive element according to claim 1, characterized characterized in that the organic pigment Is titanyl phthalocyanine pigment. 6. Process for cleaning an organic pigment for the Electrophotography, characterized by a washing process drive with deionized or distilled water a temperature of at least 40 ° C or more, one Washing process with an organic solvent at a Temperature of at least 30 ° C or more and one Dry process in vacuum at a temperature of at least 80 ° C or more. 7. The method according to claim 6, characterized in that 1 part by weight of the organic pigment with 100 to 5000 parts by weight of deionized or distilled water is washed three to twenty times. 9. The method according to claim 6, characterized in that one tetrahydrofuran is used as the organic solvent. 10. The method according to claim 6, characterized in that one Dimethylformamide is used as the organic solvent.