CH620776A5 - Electrophotographic element for image generation, process for its production and use of the element - Google Patents

Description

The invention relates to an electrophotographic element for the generation of static charge images, consisting of an electrically conductive substrate, a charge-generating layer and a charge-transport layer. The invention also relates to a process for its production and the use of the electrophotographic element in an electrophotographic process for image formation.

In electrophotography, the surface of an electrophotographic element, which contains a photoconductive layer, is first uniformly charged electrostatically and then exposed imagewise with actinic radiation. The radiation releases holes and electrons in the photoconductor, making it conductive where it was irradiated and derives the charge in these areas, leaving a charge in the non-irradiated areas and

Obtaining a latent electrostatic image. The latent electrostatic image is then developed into a visible image by depositing finely divided electroscopic particles on the surface of the electrophotographic element, 5 which are attracted to the charged areas thereof.

For practical implementation, the electrophotographic element can consist of a homogeneous layer on a base or it can be made up of several layers, for example a layer of a charge-generating photoconductive material and layers of other materials. A substantial number of electrophotographic elements made up of multiple layers have already been described in the patent literature. For example, in US Pat. No. 3 041166 15 a layer structure is described which consists of a photoconductive layer made of glassy selenium and a layer of photoconductive polymeric insulating material arranged thereon. US Pat. No. 3,165,405 describes a layer structure for a reflex copying method, which consists of a zinc oxide layer and a binder layer. US Pat. No. 3,394,001 describes an electrophotographic element in which a photoconductive material is arranged on a conductive substrate and layers made of an electron donor dye are located between and on the support and photoconductive layer.

US Pat. No. 3,573,906 describes an electrophotographic element which contains photoconductive double layers, a layer of organic possible photoconductive insulating material being arranged between the base and the photoconductive selenium layer deposited from the vapor phase. US Pat. No. 3 598 582 describes a photosensitive composite structure for a reflex copying process in which a layer of organic photoconductive particles is arranged in a directional arrangement on a base and a layer of organic charge transport material is arranged thereon

Recently, the patent literature describes composite structures which consist of a conductive substrate, a charge-generating layer and an organic charge transport layer. Structures of this type are described in U.S. Patent Nos. 3,598,582.3,713,820.3,725,058.3,824,099, 3,837,851.3 839,034.3,850,630 and 3,898,084. The last-mentioned patents can be divided into at least two categories, depending on whether the charge-generating photoconductive material is inorganic or organic in nature. If inorganic material is used, it can be arranged either in the form of particles in a binder matrix or in the form of a continuous film which is applied, for example, by vapor deposition or vacuum deposition. No exemplary embodiments are known in which inorganic materials are dissolved in a solvent and the resulting solution is applied to a base and to obtain a charge-generating photoconductive layer. With a few exceptions, when using charge-generating, photoconductive material of an organic nature, it is dispersed in the form of pigment particles in a matrix binder and applied in particle form to a base. An exception are those organic photoconductors which are themselves thermoplastic polymers and can be dissolved in a wide range of customary hydrocarbon or halogenated solvents, which is the case, for example, with polyvinylcarbazole compounds and the like. So far it is not known to dissolve organic coloring material and to produce a photoconductive layer from this solution. A variety of electrophotographic elements containing organic charge generating materials and which

are described in the literature, the organic photoconductive material is present in a layer which is composed of individual photoconductive particles, dispersed in a binder matrix. This is particularly true in those cases in which the electrophotographic elements described in the literature contain monoazo, disazo and squaric acid dye derivatives as coloring materials.

The use of monoazo, disazo and squaric acid dye derivatives in electrophotographic elements has only been described to a limited extent in the previous patent literature. An example is given in U.S. Patent 3,775,105 (Swiss Patent 588,722). This patent describes a method for increasing the sensitivity of a photoconductor by incorporating sub-micron sized diazo particles. Although the disazo compounds in this patent are ground in a solvent, it is stated that they are not dissolved but remain in particle form. A specific disazo compound for use in this method is chlordian blue. In the above-mentioned US Pat. No. 3,824,099, an electrophotographic element is described which contains a conductive base, a layer of ground particles of a square acid methine dye dispersed in a binder matrix and a charge transport layer made of triarylpyrazoline which is dispersed thereon. In this patent, although the binder dispersion is prepared in a solvent, the square acid methine particles, contrary to the fact that they are called dyes, are not in dissolved form. The use of a binder indicates that the charge generating photoconductive material of this patent could not be adhered to the base.

Another multi-layered electrophotographic element is described in U.S. Patent No. 3,873,851, which contains a conductive base, a photoconductive charge generating layer and a charge transport layer made of triarylpyrazoline. However, while in most exemplary embodiments inorganic compounds are vapor-deposited as charge-generating materials, the use of organic charge-generating layers including disazo compounds, phthalocyanine compounds and squaric acid derivatives is also described. In no embodiment is it stated that the organic charge-generating materials mentioned are dissolved and applied from solution. Finally, US Pat. No. 3,898,084 describes an electrophotographic element in which very small disazo pigment particles, dispersed in a binder matrix, are used as the charge-generating layer. In this case too, the charge-generating layer which is applied to a conductive base consists of photoconductive particles in a binder. A charge transport layer can be arranged on the charge generating layer. Many solvents are described in this patent for use in the milling and coating process of the disazo compounds, but are not stated to dissolve the disazo compounds. A binder matrix is therefore also required to fix the particles on the base.

While it is known to use disazo dyes and squaric acid dye derivatives in electrophotographic elements, it is not known from any of the aforementioned patents how these materials can be dissolved and used in this form to produce an electrophotographic element for image formation. It is also not known that the dyes, once dissolved, can be applied to a substrate without using a binder matrix.

Other solvents for these monoazo and disazo

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Dyes are known, or have been discovered and used previously, for example for dye recrystallization. Reference is made to the publication by H.E. Hunziker and R.B. Larrabee in the IBM Technical Disclosure Bulletin, Vol. 18, No. 3, August 1975, page 908. These solvents include sulfuric acid, liquid ammonia and nitrobenzene. However, these solvents have a corrosive effect, are difficult to handle or have such a low solubility for the dyes that they are practically unusable for dissolving the dyes and for applying the photoconductive charge-generating layer from solution. Because of the corrosive nature of these solvents, both the coating device and the bases on which the dyes are to be applied can be destroyed.

Photoconductive composite structures that contain both polymer or charge transport materials and charge-generating materials in the same layer are described in US Pat. Nos. 3,121,006 and 3,121,007.

It is highly desirable to be able to apply charge generating photoconductive materials from solution. When applying from solution, the grinding and grinding of the photoconductive pigment and the use of additional expensive binders and larger amounts of solvent for the binder are no longer necessary in order to apply the pigment firmly to the substrate. Further disadvantages of crushing and grinding are given below. As a rule, comminution or grinding takes a great deal of time and can only be partially started at the same time. For this reason, processes for producing photoconductive layers using ground particles in a binder matrix are only carried out batchwise, or increased expenditure is required to set up a number of milling devices in order to be able to produce the coating material continuously.

Experience with disazo particles in a binder matrix, which is applied to a base and dried, has shown that only relatively thick coatings with limited photosensitivity can be produced. To improve photosensitivity, it is necessary to polish the surface of the binder disazo dye coating. This additional step is not only expensive in terms of cost and time, but was also found

that by polishing, the reproducibility of photosensitivity varies from element to element and even in different areas of the same element. In contrast to this, a coating process from solution with or without a binder permits rapid continuous preparation of the dye solution and application thereof, and makes a batch process unnecessary. The continuous mode of operation is simpler and less economical, allows greater reproducibility of the concentrations of the coating solution and the thickness of the coatings and therefore also greater reproducibility of the photosensitivity. Furthermore, the approach to coating from solution can easily be multiplied, and the method allows the production of extremely thin coatings which, after being applied to a substrate, require no further treatment, for example a polishing process.

The object of the invention is to provide an electrophotographic element for image formation which contains a continuous thin layer of a charge-generating dye applied from solution, with which the disadvantages of the thick binder-containing layers with pigment particles can be avoided. The object of the invention is also a method for producing an electrophotographic element, in which the charge-generating photoconductive dye is dissolved in a solvent or from a solvent mixture and applied to a layer support from this solution

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b5

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The object of the invention is achieved by an electrophotographic element of the type mentioned at the outset, which is characterized in that the charge-generating layer contains monoazo dyes, disazo dyes or dye derivatives of squaric acid which are soluble in a solvent containing a primary organic amine.

The invention also relates to a process for producing this electrophotographic element, which is characterized in that monoazo dyes, disazo dyes or dye derivatives of square acid of the general formulas in B are selected from

(a)

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(b)

in which the radical W is selected from the group of NO2, CN, Cl, Br, H, CHs, OCHa, OC2H5, OH and N (C2H5) 2;

n— N

in which A is selected from and Z in formula a) is H, OH or CH3;

be dissolved in a primary organic amine-containing solvent 20 and the resulting solution is applied to an electrically conductive support.

Advantageous embodiments of the invention are laid down in the dependent claims.

According to the present invention, electrophoto-25 graphic layer arrangements are produced which consist of a layer support, a specific charge-generating photoconductive material which is applied from a solution containing a primary organic amine and a coating of charge transport material. As indicated above, the charge generating photoconductive materials are selected from a group of dyes that include certain monoazo compounds, disazo compounds, and squaric acid derivatives that are soluble in primary organic amines.

35 The monoazo compounds that can be used in the present invention are compounds of the following structural formula

OH

(a)

H

C.

/

(b)

N C—

V

yc

O

H

ch.

c = 0

(c) —M C —CH

and X and Y are selected from the group of NO2, CN, H, CHs, OCH3, O & H5, OH, Cl, Br and N (C2Hs) 2; and R in formula a) is a nitrogenous alkyl or an ester group; and in which W is selected from the group of NO2, CN, Cl, Br, H, CHs, OCHs, OC2H5, OH and N (C2H5) 2.

The disazo compounds that can be used in the present invention 55 include compounds of the structural formula

B

one in which A is selected from the group of

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OH

(a)

n - c

I II

h c-

V

(c)

R in (a) is a lower alkyl or an ester group and X and

Y are selected from the group of:

NO2, CN, H, OL, OCH3, OC2H5, OH, Cl, Br and N (C2H5) 2.

This family of disazo compounds includes essentially the same compounds described in U.S. Patent 3,898,084.

Derivatives of squaric acid include compounds of the formula q

B

one in which B is selected from the group of

(a)

(b)

and Z is selected from the group of H, OH and CHî.

It has now been found that the groups of dyes mentioned above contain dyes which can generate charges and are soluble in solvents containing one or more primary organic amines.

Compounds of the structural formulas given above can be prepared by known processes, in each case by selecting the correspondingly substituted starting materials and carrying out the synthesis by known processes.

It must be emphasized that in the practice of the present invention, the dye components, when applied to the support, are dissolved and are not in the form of particles.

The use of the word "dye" to describe these materials is consistent with this fact because the word "dye" is generally used to describe a colored material which is in solution as opposed to the word "pigment" which is used to describe colored particles that are not in solution.

The dye solution is used according to the present invention to form a thin layer applied from solution on a conductive base. The dye layer is covered with a charge transport layer. Multilayer systems of this type are described in U.S. Patent No. 3,598,582. Specific embodiments of such a system, which include triarylpyrazoline compounds which are dispersed as organic charge transport materials in the matrix of a binder, are described in US Pat. No. 3,837,851.

Since the dyes are now dissolved without a matrix binder, which can take over the charge transport function, a separate charge transport layer is required. However, changing amounts of binders and other materials compatible with the solution, including solution-compatible charge transport materials, can also be introduced into the solution. Charge transport binders of this type and composite systems are described, for example, in U.S. Patents 3,121,006,3121007,3,406,063 and 3,484,237.

Some of the dyes used in the present invention are in the Color Index, co-owned by the Society of Dyers and Colorists in 35 England and the American Association of Textile Chemists and Colorists, Lowell, Massachusetts, USA, in the second Edition, 1956, was published. In these cases, the color index number C.I. is given for the individual dyes.

40 The electrophotographic elements for image formation, the charge-generating layer of which is produced according to the invention from the solution, contain a base which can be produced from any suitable conductive material. Typical conductive materials include aluminum, steel, brass, and the like. The pad can be rigid or flexible and can be of any suitable thickness or width. Typical arrangements include flexible tapes or cuffs, sheets, a nonwoven or rigid plate, cylinders and drums. The pad may also be constructed from a composite structure, such as a thin conductive coating on a paper pad; a plastic pad covered with a thin conductive layer of aluminum or copper; or made of glass covered with a thin conductive coating of chrome or tin oxide 55.

If the structure contains a charge transport material in the form of a coating, any suitable transparent material can be used which is capable of supporting the injection of the light-excited carriers in the form of bo holes or electrons from the charge-generating photoconductive layer, and that allows the transport of these charge carriers through the charge transport layer, which selectively discharge a charge on the surface of the imaging element. The first requirement is that the transport material, which is a coating, be essentially transparent in the wavelength range in which the electrophotographic element for imaging is exposed. The active transport material can either be an electric one

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Depending on the characteristic peculiarity and mode of action of the charge-generating photoconductive material and the corona charge on the surface of the image-forming element. Typical known hole-conducting materials are: carbazole, N-ethyl-carbazole, N-isopropyl-carbazole, N-phenylcarbazole, tetraphenylpyrene, 1-methylpyrene, perylene, chrysene, anthracene, tetracene, 2-phenylnaphthalene, azapyrene, fluorene, Fluorenone, 1-ethylpyrene, acetylpyrene, 2,3-benzrysene, 3,4-benzopyrene, 1,4-dibromopyrene, phenylindole, polyvinyl carbazole, polyvinyl pyrene, polyvinyl tetracene, polyvinyl perylene, and tri-aryl pyrazoline. Suitable electron-conducting materials are 2,4,7-trinitro-9-fluorenone (TNF), 3,4,5,7-tetranitro-9-fluorenone, dinitroanthracene, dinitroacridine, tetracyanopyrene and dinitroanthraquinone. Most of these charge transport materials are dispersed in a suitable polymeric binder prior to application.

In addition, any polymer which contains a part which permits the corresponding aromatic or heterocyclic charge carrier transport, for example carbazole, tetracene, pyrene or 2,4,7-trinitro-9-fluorenone, can act as active transport material. Polyesters, polysiloxanes, polyamides, polyurethanes and epoxies, as well as block random or graft copolymers which contain the aromatic part, are examples of the different types of polymers which can be used as solution-compatible charge transport material.

The thickness of the charge transport layer is generally not critical to the function of the electrophotographic element. However, the thickness of the charge transport layer can be dictated by practical requirements, for example the size of the electrostatic charge required to induce a field that can cause hole or electron injection and charge transport. Layer thicknesses of the charge transport layer of about 5 to 100 μm are generally usable, layer thicknesses outside this range can also be used. The ratio of the layer thickness of the charge transport layer to that of the photoconductive layer does not appear to be critical.

When the charge transport layer is between the light source and the charge generating layer,

the transparency of the charge transport layer must be so great that a sufficient amount of radiation passes through the charge transport layer so that the photoconductive layer can function as a charge-generating layer.

If, for example, a layer structure with a transparent substrate is used, the exposure can also be carried out through the substrate without requiring that light pass through the charge transport layer. In this case, it is not necessary for the charge transport layer to be non-absorbent (transparent) in the used wavelength range. Other applications where full transparency of the charge transport layer is not required include the use of an electrophotographic element for the selective recording of narrow bandwidth radiation such as that emitted by lasers. The charge transport layer can consist entirely of charge transport material, but it can also consist of charge transport material dispersed in a suitable binder which, together with the charge transport material, allows holes or electrons from the charge-generating dyes to be effectively conducted through the charge transport layer. Typical resinous binders for the charge transport layer. which can be used in the context of the invention are polystyrene, silicone resin, polycarbonate, acrylic acid and methacrylic acid ester polymers, polymerized ester derivatives of acrylic and alpha-acrylic acid, polymeric

ized butyl methacrylates, chlorinated rubber, vinyl polymers and copolymers such as polyvinyl chloride and polyvinyl acetate, cellulose esters and ethers such as ethyl cellulose, nitrocellulose and alkyd resin. Mixtures of these resins may also be used with one another or with plasticizers to improve the adhesion, flexibility and application of the coatings. Particularly advantageous mixtures of a binder contain an acrylic resin and a polycarbonate for use in connection with tri-arylpyrazolines in a charge transport layer of a multilayer photoconductor.

In most cases, where the charge transport layer is a separate cover layer, it not only serves to transport the charge, but also protects the photoconductive layer from abrasion and chemical attack and therefore extends the life of the electrophotographic element for image formation.

In the embodiments according to the present invention, the thickness of the photoconductive charge-generating layer is approximately 0.025 to 0.05 n, and layer thicknesses outside this range can also be used. As already mentioned, a prescribed ratio of the layer thicknesses of the charge-generating layer and the charge-transport layer is not necessary, although the charge-transport layer is normally much thicker than the charge-generating layer because of its binder matrix

In another embodiment of the electrophotographic element according to the invention, the base is coated with an adhesive or a polymeric layer before the charge-generating photoconductive material is applied from solution. While this layer of adhesive or polymer is not normally required to bind the dye to the backing, it is useful in some cases to improve both the adhesion and the uniformity of the dye coating on the backing. If the pad is precoated with an adhesive or polymer coating, it must be of such a nature and thickness that it does not hinder the flow of charge between the charge generating layer and the conductive pad

In general, the solubility of the charge generating photoconductive dyes used in the present invention decreases as the number of carbon atoms in the R group of the amine increases. The term “primary organic amine-containing solvent” includes individual amines, mixtures of amines and solutions which, in addition to one or more of the primary organic amines, can also contain other organic solvents. The content of other organic solvents has been found to reduce the overall solubility of the dyes in the solution, but the content of other solvents is sometimes advantageous. For example, solvent additives are advantageous for checking the drying time and the smoothness of the coating.

It was also surprisingly discovered that when a charge-generating layer was applied from a solution of the disazo dye chlorodian blue in a mixed solvent of tetrahydrofuran, ethylenediamine and n-butylamine, a particularly advantageous uniform and dense layer was obtained which was essentially free of voids and irregularities. It was further found that the solution containing tetrahydrofuran, ethylenediamine, n-butylamine and chlordian blue remained stable for a long period of time without the chlordian blue pigment failing, so that there was a considerable improvement in the practical application of this charge-generating material, which was dissolved in solvent mixtures , in terms of shelf life and durability.

Chlorodian blue disazo dye and tetrahydrofuran, ethylenediamine, n-butylamine can be used in any relative

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Ratio are mixed together to obtain charge-generating coatings. However, it has been found that good charge-generating properties of the photoconductive coatings are obtained when the solvent mixture is about 30 to 60% by weight of tetrahydrofuran, 10 to 40% by weight of ethylenediamine and 10 to 40% by weight of n-butylamine contains. The solvent components are preferably present in the relative amounts of about 2 parts by weight of tetrahydrofuran, one part by volume of ethylene diamine and one part by volume of n-butylamine, which preferred relative amounts of about 55% by weight of tetrahydrofuran, 25% by weight of ethylene diamine and 20% by weight correspond to n-butylamine, mixed.

It was also found that when mixing chlorodian blue disazo dye with the tetrahydrofuran / ethylenediamin and n-butyl solvent mixture according to the present invention, it is advantageous to first mix the chlorodian blue disazo pigment with ethylenediamine until the Dye is completely dissolved. Then n-butylamine should be added and finally tetrahydrofuran.

The amount of chlorodian blue relative to the tetrahydrofuran / ethylenediamine / n-butylamine solvent mixture is not critical. However, it has been found that it is advantageous if the final solution contains about 0.5% by weight of chlorodian blue for optimal utilization of the components of the solution and taking into account the relative solubility of the dye. 25th

If desired, a wetting agent can also be incorporated into the solution. The known and suitable wetting agents, for example silicone oils, can be added. Although the wetting agent can be added in any amount that is easy to determine, it has been found that it is advantageous to add the wetting agent in an amount of about 0.5% by weight based on the weight of the chlorodian blue disazo dye to add.

Unless expressly stated otherwise, this description describes the ratios in volume ratios 35. For the sake of convenience, the use of amines which are liquid at ambient temperatures is preferred in the present invention.

Example 1 "o

The dye used in this example is "Chlordian Blue". The synthesis of chlordian blue, hereinafter referred to as "CDB", is given, for example, in US Pat. No. 3,898,084. The structure of CDB is given below under this sample number. 45

A 0.5 weight percent solution of CDB is made in a mixed solvent with a volume ratio of 1: 1 methylamine / n-butylamine. The resulting solution is applied to the surface of an aluminized polyethylene terephthalate nonwoven using a meniscus coater. The resulting coating showed excellent adhesion to the backing. It is coated with a charge transport layer made of DEASPin Vitel PE-200, a linear saturated polyester from Goodyear Tire and Rubber Comp., Without further treatment. DEASP is the abbreviation for a charge transport material that is fully referred to as l-phenyl-3- (p-diethylaminostyryl) -5- (p-diethylaminophenyl) pyrazoline. The resulting electrophotographic element for image formation showed good photosensitivity and was suitable as an electrophotographic element for image formation. When the element was charged to -700 V in the dark, 1.1 nJoules / cm2 was required to discharge it to a charge of -200 V.

Chlordian blue has excellent properties as a charge generating photoconductive material and is the preferred dye for use in the invention. Attempts have therefore been made to determine the solubility of CDB in various primary organic amines, diamines, amine mixtures and mixtures of amines with other solvents. The results of these experiments are shown in Table I. The utility of liquid ammonia, which is not a primary organic amine as defined by the present invention, as a solvent has been determined and is included in the table for information. The use of ammonia as a solvent in the practice of this invention is not specifically claimed.

Table I Solvent systems for CDB

solvent

Solubility of CDB

Liquid ammonia 1.5 g / 1

Methylamine 50 g / 1

4: 1 dimethylformamide / methylamine 80 g / 1

Ethylamine> 10g / <20g / l

1: 1 methylamine / butylamine 75 g / 1

1: ethylamine / tetrahydrofuran 5 g / 1

Ethylene diamine 180 g / 1

n-butylamine

Diethylene triamine

Isopropylamine t-butylamine

1 = soluble, but maximum solubility not determined Example 2

CDB was dissolved in ethylenediamine to a 1.5 weight percent solution. The resulting solution was applied to the surface of an aluminized polyethylene terephthalate nonwoven with a meniscus coater and dried to form a continuous coating of CDB. The dry weight of the dye was determined to be about 0.0155 mg / cm2 (0.1 mg / in2). The dye applied from solution was then coated with DEASP as indicated in Example 1. The resulting element was suitable for use as an electrophotographic element for imaging. It had a sensitivity that when charged in the dark to -700 V by a corona discharge and then exposed to a green photocopy lamp, 0.65 nJoules / cm2 was required to discharge it to a charge of -200 V.

Examples 3-7

As indicated in Table II below, a number of related disazo dyes were dissolved in primary amine solvents. In each case, the resulting solution was applied to a base of conductive aluminized polyethylene terephthalate and coated with a charge transport layer. The sensitivity of each resulting electrophotographic imaging member, expressed as a discharge from -700 V to -200 V, or "EJ88", when measured, is also reported in Table II. The element was found to be suitable for electrophotographic imaging in each case.

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Table!!

Example disazo dye

solvent

sensitivity

Disazo dye from naphthol-AS-SR and dichlorobenzidine Disazo dye from naphthol-AS-SR and benzidine

Disazo dye from naphthoI-AS-SG and benzidine

Disazo dye from Naphthol-AS-SG and dichlorobenzidine Electra-Red

3: 1 ethylamine / ethylenediamine

3: 1 ethylamine / ethylenediamine

3: 1 ethylamine / ethylenediamine

3: 1 ethylamine / ethylenediamine 3: 1 ethylamine / ethylenediamine

3.93 (ijoules / cm2 2.44 (xjoules / cm2

The structures and, if available, the C.I. numbers for 20 working examples are given below: each disazo dye in correlation with the numbers of the

Examples 1 and 2

N = N-

Chlordian blue, disazo dye from Naphthol AS (Eq. 37 505) and dichlorobenzidine

Example 3

Disazo dye from Naphthol-AS-SR (C.1.37 590) and dichlorobenzidine

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Example 4

Disazo dye from naphthol AS-SR (C.1.37 590) and benzidine.

Example 5

OCH.

Disazo dye from naphthol AS-SG (C.1.37 595) and benzidine.

Example 6

OCH

Disazo dye from naphthol AS-SG (C.1.37 595) and dichlorobenzidine.

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Example 7

CH3 CH3

Electra red (C.I. No. 21 200).

Examples 8-16 15 of Corning Corporation to the dye solution as a leveling

A number of related monoazo dyes have been added or wetting agents added. The resulting, from solution sets up as shown in detail below. Each dye-borne dye layer, when dried, was coated with one to form an electrophotographic image-transport layer from a 9: 1 mixture of Mobay-generating element according to the teachings of the present Erfin Chemical Comp. M-60 polycarbonate and Vitel PE-200 poly-dung used. In each case the monoazo dye was coated in 20 esters and DEASP. The ratio of polymer mi-n-butylamine to a solution with the DEASP given in Table III was 1.5: 1, and the resulting solution was dissolved in weight percent concentrations and onto one of the charge transport material was added to a dry-aluminized polyethylene terephthalate pad a dry weight of about 3.1 mg / cm2 (20 mg / in2). The elements produced according to the weight, which is also given in Table III, of Examples 8 to 16 were elec- tric. In each example, 0.25%, by weight 25 trophotographic elements suitable for imaging, of the monoazo dye, DC-200 polydimethylsiloxane from Dow

Table III

example

Monoazo dye

% By weight of dye in the solution

Coating weight in mg / cm2

A V in volts

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1 - (p-nitrophenylazo) -2-hydroxy-

3-naphthanilide

3.0

0.068

155

9

l- (p-Cyanphenylazo) -2-hydroxy-

3-naphthanilide

10.0

0.067

63

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l- (p-chlorophenylazo) -2-hydroxy-

3-naphthanilide

7.5

0.03

45

11

l-phenylazo-2-hydroxy-3-

naphthanilide

3.3

0.020

56

12

1 - {p-methylphenylazo) -2-hydroxy-

3-naphthanilide

7.5

0.040

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13

l- (p-methoxyphenylazo) -2-hydroxy-

3-naphthanilide

7.5

0.043

5

14

l- (p-hydroxyphenylazo) -2-hydroxy-

3-naphthanilide

1.0

0.0124

45

15

Hp-diethylaminophenylazo) -

2-hydroxy-3-naphthanilide

10.0

0.0310

Obis 1

16

1 - (o-chlorophenylazo> 2-hydroxy-

3-naphthanilide

7.5

0.0341

-

АV, which is listed in Table III, is a measure of the. Each resulting solution was then analyzed using a meniscus

Sensitivity. To determine AV, the electro-coating method was weighted onto the conductive surface of an aluminum photographic element on approximately 2.3 × 105 V / cm of polyethylene terephthalate fleece laminated to dryness and with light with a wavelength of 5500 Â in the form of 55 kw that is given in Table IV. Discharge any given pulses of approximately 4.0 n, joules / cm2. Dye layer applied from solution was measured after drying. The resulting voltage change after exposure was dried with an approximately 8 ji thick layer of DEASP and coated taking into account the dark discharge vacuum. Corrected the electrophotographic element. The values are listed in Table III of each example was then adjusted to approximately 2.3 x 105 V / cm.

Load 60 and discharge with light of a wavelength of 5500 Â and pre-examples 17-24 given pulses of about 8.0 pjoules / cm2. The

In these examples, most of the mono azo color voltage change AV was normalized after applying a correction to the substances that were already used in Examples 8 to 16, taking into account the dark discharge. The monoazo dyes turn again in the form of the formula n-butylamine into a solution with a predetermined amount in 65

Weight percent dissolved with the addition of 0.25 wt .-%, bezo-. "_ ^ V / V x 100

to the monoazo dye, standardized by DC-200 dimethyl silicone oil v - .2

from Dow Corning Corporation as a leveling or wetting agent. "» 0 flJoules / cm

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"The values determined are listed in Table IV, values for the dark discharge are also given in the table.

Table IV

Example monoazo dye wt .-% coating AV normalized dark in the solution wt. in mg / cm2 discharge in in V / s

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1 - {p-nitrophenylazo) -2-

hydroxy-3-naphthanilide

3.0

0.068

2.6

0.8

18th

Hp-cyanphenylazo) -2-

hydroxy-3-naphthanilide

10.0

0.067

5.0

0.8

19th

l-phenylazo-2-hydroxy

-3-naphthaniIid

3.3

0.020

10.4

1.0

20th

1 - (p-chlorophenylazp> 2-

hydroxy-3-naphthanilide

7.5

0.034

7.0

0.8

21st

Hp-methylphenylazo) -2-

hydroxy-3-naphthanilide

7.5

0.040

5.7

0.8

22

1 - (p-hydroxyphenylazo) -2-

hydroxy-3-naphthanilide

1.0

0.0124

4.8

3.5

23

Hp-methoxyphenylazo) -2-

hydroxy-3-naphthanilide

7.5

0.043

3.2

0.8

24th

Hp-diethylaminophenylazo) -

2-hydroxy-3-naphthanilide

10.0

0.031

3.5

3.0

The structure of each monoazo dye of Examples 11 and 19

8-24 in correlation with the exemplary embodiments is given below:

30th

Hp-nitrophenylazo) -2-hydroxy-3-naphthanilide Examples 9 and 18 0

Hp-cyanphenylazo) -2-hydroxy-3-naphthanilide

Examples 10 and 20 O

II

C.

/

, NH

45

l-phenylazo-2-hydroxy-3-naphthanilide

Examples 12 and 21 0

I!

C /

.NH

55 l- (p-methylphenylazo) -2-hydroxy-3-naphthanilide Examples 13 and 23

—N = N - ((V-OCH

Hp-chlorophenylazo) -2-hydroxy-3-naphthanilide

Hp-methoxyphenylazo> 2-hydroxy-3-naphthanilide

620776

Examples 14 and 22

14

1- (p-Hydroxyphenylazo) -2-hydroxy-3-naphthanilide Examples 15 and 24

Hp-diethylaminophenylazo) -2-hydroxy-3-naphthanilide Example 16

30th

Example 26

2,4-bis- (2-hydroxy-4-dimethyilino-phenyl) -l, 3-cyclobutadienediylium-1,3-diolate, a derivative of squaric acid, was prepared. This dye derivative of squaric acid was prepared in a 1: 5: 24-Mixture of ethylenediamine / n-propylamine / tetrahydrofuran dissolved in a 3.3 weight percent dye solution. As in the previous example, the dye solution was applied to an aluminized polyethylene terephthalate pad using a meniscus coating process to give a coating with a dry weight of about 0.0093 mg / cm2. The dried coating was then coated with a charge transport layer made from a 1: 1 mixture of DEASP and Mobay M-60 polycarbonate, the charge transport layer having a dry weight of about 2.326 mg / cm 2. The resulting element was charged to -800 V in the dark and 0.43 (ijoules / cm2 was required to discharge the element to -190 V. As such, the element was very useful as an electrophotographic element for imaging

The square derivative dye derivative used in this example had the following structure:

50

55

1- (o-chlorophenylazo) -2-hydroxy-3-naphthanilide CI. No. 12300

Example 25

2,4-bis- (2-methyl! 4-dimethylamino-phenyl> 1,3-cycIobutadienediylium-1,3-diolate, a derivative of squaric acid, was prepared. This dye derivative of squaric acid was then prepared in a 1: 1 "Solution of ethylamine / n-butylamine was dissolved in a 0.5% by weight dye solution. The resulting solution was applied to the conductive surface of an aluminized polyethylene terephthalate fleece by means of a meniscus coating process at a speed of 1.525 m / min. After drying, the was applied solution layer coated with a 2: 1 mixture 60 of a Vitel PE-200 polyester and DEASP in a layer thickness of about 20 p. The resulting element was charged to -700 V in the dark and was about 1.1 pjou -Ies / cm2 of a green copying lamp required for a discharge to -200 V. The element was suitable for use as a 65 electrophotographic element. The structure of the dye derivative of squaric acid, which is described in This example was used as follows:

Examples 27 and 28

Two further dye derivatives of squaric acid were prepared and their solubility in solvents containing primary organic amines was determined. The first compound was 2,4-bis (2,3,3-trimethyl-2-indolinylidemethyl> 1,3-cyclobutadiene-diylium-1,3-diolate with the following structural formula:

The second compound was 2,4-bis- (p-dimethylaminophenyl) -1,3-cyclobutadiene-diylium-1,3-diolate with the structural formula given below:

15

620776

Both dye derivatives of squaric acid were dissolved in ethylenediamine and applied to an aluminized polyethylene terephthalate fleece. They have been used advantageously for the production of electrophotographic elements for image formation.

Example 29

In a preferred embodiment of the invention, an electrophotographic imaging member was made using the disazo dye chlorodian blue (CDB). The electrophotographic element was produced as a layered structure by successively applying coatings on a support. A 0.076 mm thick polyethylene terephthalate film which was coated on one side with aluminum in order to impart conductivity to the base was used as the base. A polyester adhesive was applied to the aluminized surface of the conductive pad. A charge-generating layer of chlorodian blue dye was arranged on the adhesive layer, which layer was applied with a 0.5 percent by weight dye solution in two parts by weight of tetrahydrofuran, one part by volume of ethylene diamine and one part by volume of n-butylamine. The composition of the solvent mixture corresponds to a solvent ratio of about 55% by weight of tetrahydrofuran, 25% by weight of ethylene diamine and 20% by weight of n-butylamine, based on a specific weight of 0.90 for ethylene diamine and 0.739 for n-butylamine . The solution of chlorodian blue to make the charge generating layer was prepared and applied as follows. In a four-liter plastic kettle equipped with a stainless steel stirrer, 15.0 g of chlordian blue (CDB) and 756 ml p.a. Ethylene diamine (93%) given. The solution was stirred until the chlorodian blue was completely dissolved. Then 750 ml p.a. n-Butylamine added with stirring. Then 42 g of a 1% solution of DC-200 polydimethylsiloxane in tetrahydrofuran (THF) and 1458 g of THF were also added with stirring.

The resulting solution was placed in a slitter nozzle coater and applied to the adhesive-coated base, and then dried in an oven. On the exposed surface of the

30th

35

45

Chlorodian blue layer was applied an approximately 20 jx thick layer of DEASP and M-60 polycarbonate in a weight mixing ratio of 1: 1.

In the layer structure, the aluminized substrate serves as a base and electrically conductive base plate, which allows the charges that are fed to it from the rest of the layer structure to flow away. The adhesive layer causes the adhesion between the aluminum surface and the charge-generating layer made of chlorordian blue. When the chlorine blue layer is struck by the photons of light, holes and electrons are created in this layer. The holes are injected into the DEASP charge transport layer and the electrons tunnel through the adhesive layer to the aluminum layer and are derived therefrom to the earth. In the layer structure of this embodiment, the DEASP charge transport layer is suitable for the transport of holes to the surface of the electrophotographic element.

In use, a charge generated by a corona discharge is applied to the outer surface of the electrophotographic element. In this embodiment the corona charge is negative, i.e. in the form of electrons. Holes and electrons are created in chlorodian blue by the action of photons on the dye. The holes are transported through the charge transport layer to the surface of the imaging element, where they recombine with electrons, neutralize each other and eliminate parts of the charge on the surface. DEASP is naturally very well suited for hole transport and hardly conducts electrons. The DEASP charge transport layer is essentially transparent to light in the visible spectral range. Therefore, almost all of the light that strikes the surface of the photoconductive element is transmitted through the charge transport layer, so that holes and electrons are sufficiently generated in the CDB charge transport layer as a result of the exposure.

Examples 30-38

Example 29 is repeated depending on the mixing ratios of tetrahydrofuran, ethylenediamine and n-butylamine and using different amounts of CDB dye as charge-generating material and different amounts of DC-20 wetting agent. When using the solutions for forming a charge-generating layer analogous to Example 29, a defect-free coating with good electrical sensitivity and essentially without voids and irregularities which would adversely affect the photocopy was obtained in each case. The relative amounts of tetrahydrofuran (THF), ethylenediamine (ÄDA), n-butylamine (BA), DC-200 and CDB, given in% by weight, as well as the nature of the resulting charge-generating coating are given in Table V.

Table V

Example THF

ADA

BA

DC-200

CDB

formed coating

30th

55.56

23.81

19.55

0.0026

1.05

Good

31

54.36

24.46

20.08

-

1.08

Good

32

54.60

24.59

20.19

-

0.54

Good

33

29.25

26.00

43.24

-

1.17

Good

34

54.64

24.59

20.19

0.013

0.5

Good

35

49.45

14.40

35.60

0.013

0.48

Good

36

30.94

25.80

42.37

0.022

0.86

Good

37

38.93

33.06

27.93

0.022

0.82

Good

38

54.63

24.50

20.19

0.021

0.55

Good

620776 16

Examples 39-52 obtained from Monsanto under the trade name Formvar 795-E-

Example 29 was repeated as in Examples 30 to 22 and methyl methacrylate resins such as B-76, B-82 and WR-97 38, only that now additional polymeric binders from Rohm & Haas. The relative amounts of tetrahydrofuran-generating layer were incorporated. Similar (THF), ethylenediamine (ÄDA), n-butylamine (BA), DC-200, CDB;

received good coatings. The binders used were 5 the percentages and the binders specifically used, saturated polyesters such as Vitel PE-200 and Medium and the nature of the resulting charge generator Vitel PE-207 from Goodyear Comp., A polyvinyl formal, the layer below are in Table VI specified.

Table VI

example

THF

ÄDA

BA

DC-200

CDB

Binder formed cover

39

54.45

24.51

20.12

0.02

0.54

0.32 PE-200

Good

40

54.45

24.51

20.12

0.02

0.32

0.54 PE-200

Good

41

54.45

24.51

20.12

0.02

0.54

0.32 795-E

Good

42

54.45

24.51

20.12

0.02

0.32

0.54 795-E

Good

43

54.45

24.51

20.12

0.02

0.54

0.32 PE-207

Good

44

54.45

24.51

20.12

0.02

0.32

0.54 PE-207

Good

45

54.45

24.51

20.12

0.02

0.54

0.32 B-76

Good

46

54.45

24.51

20.12

0.02

0.32

0.54 B-76

Good

47

54.62

24.62

20.21

0.02

0.43

0.11 PE-200

Good

48

54.62

24.62

20.21

0.02

0.32

0.21 PE-200

Good

49

54.62

24.62

20.21

0.02

0.43

0.11 WR-97

Good

50

54.62

24.62

20.21

0.02

0.32

0.21 WR-97

Good

51

54.62

24.62

20.21

0.02

0.43

0.11 B-82

Good

52

54.62

24.62

20.21

0.02

0.32

0.21 B-82

Good

Examples 53-57

For comparison, several solutions of the charge generating material were prepared and applied as indicated in Example 29, except that the solvent consisted of a mixture of only two solvents or of a single solvent, i. H. either ethylenediamine together with toluene or ethylenediamine alone. In each case, it was found that the resulting charge 30

35

generating layer was much less satisfactory when CDB was applied from solution. The relative amounts of tetrahydrofuran (THF), ethylenediamine (ÄDA), n-butylamine (BA), toluene (TOL) and CDB, given in percent by weight, as well as the nature of the resulting charge-generating coating are given in Table VII below.

Table VII

Example THF

ADA

BA

TOL

CDB-formed top layer

53

54

55

56

57

22.57 66.00

76.70

76.32 33.50 84.50 98.90

22.14 1.11 particularly poor CDB coating 1.10 poor adhesion 0.48 poor coating 14.3 1.15 poor coating 1.09 poor coating

Example 58

Attempts have been made to improve the physical nature of the electrophotographic imaging elements described in the previous examples and the polymeric binder has been incorporated into the charge generating layer by dissolving it in the solution of the charge generating material. The following electrophotographic element was produced for this purpose. To a mixture of 1 ml of ethylenediamine and 5 ml of n-propylamine, 700 mg of the dye derivative of squaric acid used in Example 26 and 300 mg of the dye derivative of squaric acid used in Example 25 were added. After the dye mixture had dissolved, a polymer solution of 222 mg of Elvacit 2010 methyl methacrylate resin from E.I. duPont de Nemours & Co., dissolved in 24 ml THF, added. Both solutions were compatible with each other.

The dye-polymer solution was then applied to a conductive pad on a conductive pad using a meniscus coating process to a dry weight of about 0.0078 mg / cm 2. The resulting continuous homogeneous coating of dyes and polymer was coated with the solution of a charge transport material consisting of a 2: 3 mixture of DEASP / M-60 polycarbonate in a 9: 1 mixture of THF / toluene 60

To discharge the resulting electrophotographic element from -870 to -150 V, 1.17 pjoules / cm2 was required.

As described in the numerous examples, the invention represents an improvement on the previously known methods for producing electrophotographic elements for image generation. The method is considerably simpler and avoids the batch production of the charge-generating element

17 620 776

Material in particle form in which the material is comminuted or ground in long perio process steps, methods, compositions or electrodes. It also allows the elements described above. Other Advantages and Methods According to the Invention The manufacture and uses of this invention can be accomplished by using extremely thin charge generating layers, which are determined in multiple experiments, and it can also be an opti-general less than 1.0 µm in thickness and up to 50 À thin may be necessary without the need of a given system. To deviate the charge generation layer once made from the principles of the invention. In any case, no additional treatment is required. In general, it can be seen that the use of solvents with the process according to the invention produces charge-generating materials containing primary organic amines for dissolution which have good to high photosensitivity on the charge-generating photoconductive monoazo, disazo will. No expensive binders 10 or squaric acid dye derivatives are required in manufacturing processes to produce the charge generating layer. Treatment of electrophotographic elements for image production Finally, the method can be easily multiplied because it is advantageous. While the invention has not been specifically described with reference to specific grinding or grinding dyes and solvents, it may be necessary. As indicated, the charge generating other photoconductive charge generating material will dissolve in a solvent containing a 15 and solvent systems the dyes according to the primary organic amine and replace with known prior art and these will drive the monoazo applied to a conductive substrate. A charge disazo and squaric acid dye derivatives and the solution transport layer are then carried in any manner containing primary organic amines. according to the present invention as completely equivalent

The advantages and principles of the invention are broadly considered.

Scope applicable and not limited to the specific

Claims (20)

620776 2 PATENT CLAIMS contains substances or dye derivatives of squaric acid, which are in 1. Electrophotographic element for the generation of a primary organic amine-containing solvent, static charge images consisting of an electrically loaned. tend layer support, a charge-generating and a second electrophotographic element according to claim 1, Charge transport layer, characterized in that the 5 characterized in that the charge-generating layer contains charge-generating layer monoazo dyes, disazo-color monoazo dyes of the general formula in which the O II Rest W is selected from the group of NO2, CN, Cl, Br, H, 20 characterized in that the charge-generating layer CH3, OCH3, OC2H5, OH and N (C2Hs) 2. Disazo dyes of the general formula 3. Electrophotographic element according to claim 1, contains, in which A is selected from location (a) - N - r ' II V (b) - H -H- fi -C • OH \ O) <0 O {c) - N C ch3 00 1 ch - and X and Y are selected from the group of NO2, CN, H, in which B is selected from CH3, OCHs, OC2H5, OH, Cl, Br and NCCzHs ^; and R in formula a) is a lower alkyl or an ester group. 50 4. Electrophotographic element according to claim 1, characterized in that the charge-generating layer dye derivatives of squaric acid of the general formula (a) 55 (b) % (YV -7 CH / 3 xcn. and Z in formula a) is H, OH or CH3. 5. Electrophotographic element according to claim 1, characterized in that the charge-generating layer contains the dye 3,3'-dichloro-4,4'-diphenyl-bis- (l "-azo-2" -hydroxy-3 "-naphthanilide) . 6. Electrophotographic element according to claim 1, 5 characterized in that the charge-generating layer contains a binder from the group of polyester, polyvinyl formal or acrylic resin. 7. Electrophotographic element according to claim 1, characterized in that a layer of polyester adhesive is arranged between the conductive layer carrier and the charge-generating layer. 8. An electrophotographic element according to claim 1; characterized in that a charge transport layer is arranged on the charge-generating layer from i s a pyrazoline derivative of the general formula OH (a) No I Ii n c V H (b) - N- 0 II -C 620 776 Oh Y)> - ch, \ a - ch c - (c = c) n - a1 I '' I i i: a1 - n n h (c) —N ■ O \\ ch3 C = -0 I. ■ ch - and X and Y are selected from the group of NO2, CN, H, CH3, OCH3, OC2H5, OH, Cl, Br and N (C2Hs) 2; and R in formula a) is a lower alkyl or an ester group; 25th in which A, A1 and A2 are substituted aryl groups and n = 0 or 1. 9. Electrophotographic element according to claim 8, characterized in that the charge transport layer 30 l-PhenyI-3- (p-diethylaminostyryl) -5- (p-diethylaminophenyl) - contains pyrazoline. G 10. Electrophotographic element according to claim 1, characterized in that the charge generating layer is 0.025 to 0.050 µm in thickness. 35 11. A method for producing an electrophotographic element for image formation according to claim 1, characterized in that monoazo dyes, disazo dyes or dye derivatives of squaric acid of the general form meln J (j in which B is selected from -w in which the rest W is selected from the group of NO2, CN, Cl, 55 Br, H, CHs, OCH3, OC2H5, OH and NCG-Hsk U) (b) \ ch > 7 "\ / 3 - \ C) v "" n. nch 3rd -ch A x in which A is selected from N n bo and Z in the formula a) H, OH or CH3 is dissolved in a primary organic amine-containing solvent and the resulting solution is applied to an electrically conductive support. 12. The method according to claim 11, characterized in 65 that the solution of a pyrazoline derivative of the general formula on the charge-generating layer of monoazo dyes-2 fen, disazo dyes or dye derivatives of squaric acid 620 776 ch, / \ CH c: ce = C), • a1 n -— n in which A, A1 and A2 are optionally substituted aryl groups and n = 0 or 1, and a binder is applied in tetrahydrofuran or tetrahydrofuran / toluene, or the pyrazoline derivative is applied alone in vacuo. 13. The method according to claim 11, characterized in that the monoazo dyes, disazo dyes or the dye derivatives of squaric acid are dissolved in a primary organic amine of the general formula R (NH2) n, in which formula n = 1, 2 or 3 and the rest R1 to 4 carbon atoms, or that the dyes are dissolved in a mixture of primary amines, optionally in the presence of an organic solvent. 14. The method according to claim 11, characterized in that a silicone oil wetting agent is added to the coating solution for producing the charge-generating layer. 15. The method according to claim 11, characterized in that 3,3 '-dichloro-4,4'-diphenyl-bis- (1 "-azo-2" -hydroxy-3 "-naphthanilide) is used as the disazo dye. 16. The method according to claim 15, characterized in that said dye dissolved in a solvent mixture of 30 to 60 wt .-% tetrahydrofuran, 10 to 40 wt .-% ethylenediamine and 10 to 40 wt .-% n-butylamine is applied to a substrate. 17. The method according to claims 15 and 16, characterized in that a coating solution containing 0.5% by weight of dye is used. 18. The method according to claim 11, characterized in that a layer of aluminized polyethylene terephthalate is used, which is coated with a polyester adhesive to improve the adhesion. 19. The method according to claim 11, characterized in that the coating solution for producing the landing-generating layer contains, in addition to the dyes, a binder from the group of polyester, polyvinyl formal or acrylic resin. 20. The method according to claim 11, characterized in that a charge transport layer is applied to the charge generating layer. 21. Use of the electrophotographic element according to claim 1 in an electrophotographic process for the generation of a static charge image.