DE2062900A1 - Method of making the photoconductive layer of an electrophotographic plate - Google Patents

Description

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Xerox Corporation 17 ...._ ,,. *., _. _ "", Z.577 * ■, DJpI. mg. H. WtiokjRiRD, Dipt. Pfiys. Dr. K. jerk ^w "

Rochester, NY 14603 (USA) Dl ^ Ia ₁ .FAWiJeI ₀ IiMi ₁ DIpLChW.aHubw W2B91

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Method of making the photoconductive layer of an electrophotographic plate

The invention relates to and relates to electrophotography in particular on the production of a binder plate that can be used for xerography.

In xerography, as originally described in U.S. Patent No. 2,297,691 (Carlson) is on a photo-conductive Insulating layer formed a latent electrostatic image and formed by finely divided electroscopic developer materials developed on it. The developed image can then be fixed in place or transferred to a copy sheet, where it is permanently fixed. In general, the photoconductive Load the insulating layer first to sensitize it; then it is exposed to an image of light or other pattern of activated electromagnetic rays, causing the Charge is distributed in the exposed areas. In this way the generated charge pattern corresponds to the pattern of the electromagnetic one Radiation acting on the plate. The charge pattern can then - as already mentioned - be developed or made visible by using an electroscopic or electrostatic touchable, finely divided colored material (usually referred to as "toner") ever. after the charge is reflected on the plate.

According to the above-mentioned US patent, suitable inorganic and organic materials can be used to produce / the photoconductive insulating layer on which the latent electrostatic image is formed. In the United States Patent Nos. 2,357,809, 2,891,001 and 3,079,342 further photoleütendo substances are described which elektrophotogröpnisohen at similar process can be trwendet * '', such as vitreous selenium, polymers such as "lyvinyl-carbazole, resin suspensions of inorganic photo- ,, iting pigments, eg zinc oxide and cadmium sulfide, most of them

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these materials have proven to be technically useful, however, each of the proposed compositions adhere to certain Disadvantages' in technical use.

The discovery of the photoconductive insulating properties of the highly-purified vitreous selenium has led to this Material became the standard in technical xerography. However, vitreous selenium is only effective at wavelengths below approx. 5,800 angstroms sensitive. Also are xerographic plates Selenium is expensive to manufacture because this material is produced by vacuum evaporation under carefully controlled conditions must be applied to the carrier substrate. Vitreous selenium layers are also only metastable and can at temperatures which are only slightly above the temperatures prevailing in conventional xerographic copiers, crystallize and in ün ° skip usable crystalline forms.

Other known xerographic plates _s organic from certain aromatic Photoleitera. are made, have a relatively low sensitivity to light, whereby most of this sensitivity is in the ultraviolet range ₉ which is not entirely sufficient for use in conventional electrophotographic copiers. Even the most sensitive organic photoconductive polymers leave a lot to be desired for technical purposes »The selection the fabric © _s .the are useful for aromatic polymers plates _f is naturally limited since. one has to choose an already photoconductive material. In addition, all of the above-mentioned xerographic plates lack abrasion resistance and stability, especially when working at elevated temperatures.

Binder plates, which contain zinc oxide pigments, are black relatively cheap, but less sensitive than the glass-like selenium plates; nor can they be used again *. As mentioned earlier, their sensitivity is in the gouty In addition, one must have such large quantities of photo «· '-

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Use conductive pigments to achieve sufficient sensitivity that zinc oxide plates are very difficult to use Smooth surfaces are given, which allow for an effective transfer the "toner" and the cleaning required before reuse are suitable. E ^ Ln another disadvantage in the use of the commercially available zinc oxide binder plates is the fact that they are better sensitized by negative Gorona discharge are considered by positive, resulting in poor Druak> quality leads. As a result of these properties, they are undesirable in the trade, because the negative corona discharge generates a lot of ozone generally harder to control than the positive urfl is.

In British Patent Kr. 1,175,451 are electrophotographic Plates and processes described in which a phthalocyanine pigment is dispersed in a binder material is. These plates may or may not be re-used j they are sensitive across the spectrum. In the parallel application Serial No. 866 926 of October 16, 1969 preferred phthalocyanine binder compositions are claimed,

In general, phthaloeyanine pigment binder boards are used produced by the Phthalooyanin-Pigroent by means of a Ball mill incorporated into the dissolved or melted binder. This marriage usually has to be carried out for days, if one wants to obtain acceptable dispersions. When using a ball mill, the recrystallization is the starting material used alpha form of phthalocyanine in da «¥ $.« 1 more light-sensitive beta polymorphs either extremely longea * or does not take place at all. · "

The aim of the present invention is therefore a method Manufacture of phthalocyanine pigment binder dispersions is free from the above disadvantages and, in particular, is faster expires. The rapid process for making the photosensitive beta form of phthalocyanine pigment binder dispersions

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starts with the less sensitive alpha polymorph as the starting material the end? the phthalocyanine is in the dispersions obtained present in a wide range of concentrations. The inventive method for producing an electrophotographic Plate with a phthalocyanine pigment dispersed in a binder material is more economical.

The present invention generally relates to a process for producing an electrophotographic Plate with phthalocyanine pigment particles as a binder material combined in a liquid medium and then ground in a sand mill.

This method is much faster than the method using a ball mill; the dispersions can received within hours (instead of days). Also, unlike the method using a ball mill the less sensitive when using a sand mill alpha-phthalocyanine starting material in a surprisingly short time recrystallized to the much more sensitive beta form. In some cases, sand-grinding is the only method with which the conversion from alpha- to beta-phthalo «· cyanine can be carried out. Technically useful dispersions can have a pigment content of up to 15-20% by weight. Whichever pigment concentration is used, however, are those produced by short-term ball milling Dispersions are not electrophotographically usable coatings.

The method according to the invention runs particularly well, to produce beta-metal-free phthalocyanine binder dispersions wants, and the starting product is the alpha form, in the Gemisoh used with beta and or X-iOrm. Except. The transforming " alpha form, all suitable phthalocyanines can be used » e.g. metal phthalocyanines and metal-free phthalocyanines such as' the alpha, beta and X forms.

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All suitable resins can be used for the process according to the invention, e.g. petroleum hydrocarbons, copolymers made of styrene-acrylonitrile, epoxies, polycarbonates, polysulfones, Styrene-butadiene, polyester, phenols, alkyd resins, silicone-alkyd resins, Coumarone-indene, phenoxy resins, polyvinylcarbazole, Polyurethanes. It is preferred to use a combination of a phthalocyanine pigment and a mixture of alkyÄ acrylate resins, a silicone and a chlorinated hydrocarbon, as stated in the parallel application Serial No. 866 926 of 10/16/69 is described in more detail.

The sand grinding can be carried out for any length of time. It is preferable to work within about 0.2-2 hours. You will get the best results if you grind for about 0.75 hours and about 50 vol-? 4 grinding medium at temperatures of about 50 - S5 ° C used.

Once the materials are combined and a photoconductive one Form a layer, they can be applied to a suitable carrier, e.g. on paper, aluminum, brass or plastic.

The mixture of pigment, binder and solvent can be applied to the carrier substrate by one of the customary methods, for example by spraying, coating with liquid, coating with a knife, electro-coating. Coating with the Mayer rod, dipping, with the roller surfaces etc. For the glattesten one turns preferably da3 then spray in the electric field at _t while in laboratory convenient working with the process to reach easily ·

The process according to the invention is explained in more detail in the following examples, without wishing to restrict the invention thereto. Unless otherwise stated, UJeile and percent-

Parts by weight or year by weight . '_;

Example 1

The following materials are first mixed and then placed in a £ -3-J laboratory sand mill (made by Chicago Boiler Company) previously semi-filled with 20-30 mesh Ottawa sand: 29 s alpha form of the metal-free Phthalocyanine (from ₉

Kolland-Suco Color Co.) »
Arotap 192 g EP8911-7-7, an acrylic Hara the firm Ashland _e

Chemicals j
192 g Chlorowax 70-ΙΓ, a chlorinated unpolyuierized paraffin resin (from Diamond Shamrock Co.),

66 g silicone resin SR-82 (from General Elektric Co *),

250 g of toluene. '■

The Ggmisch is milled for 1 hour at 2400 RPM, the temperature being between 50 and 85 ⁰ C held "While the alpha-phthalocyanine fine and is uniformly dispersed" it is recrystallized in these conditions even in the solid state in the light sensitive beta-form * The pigment dispersion is is. -fi solid Bgstandteile diluted with toluene to about 35 percent and then mit.dem Mayer bar onto a substrate from a leitfähiges- about 10.13 cm thick aluminum foil coated Di * © obtained pigment-binder layer Dyed embarrassing green. The substrate is provided with a coating which, when dry, is about 0.8.10 "cm thick. The photo-discharge properties of the pigment binder coating are determined by applying a layer with a corona discharge device with approximately positive loaded (measured with a Keithley Model 610 electrometer with DC probe) and then exposed to a Wolfraa lamp (quartz iodine at 2850 ° color temperature ne illuminance of about to reduce the potential to approx. 60 volts , using a usual xerographic equipment _f , a # B «-'Xerox model D copier _f , the Plithalocfeaift * binder coating is loaded similarly, with lolfram-borne a positive -Test chart exposed and then with the usual

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Cascade process using a dry "toner" developed. The developed image is then printed onto normal sized paper transferred, with a good image quality obtained

Example 2

About 500 g of the mixture described in Example 1 are in a ball mill filled, which was previously filled to 1/3 with flint stones of 1.2 cm diameter; one grinds for about 1 hour at ce » 140 RPM. The dispersion is applied as a coating as described in Example 1. The pigment-binder layer obtained is colored deep blue. If you check their sensitivity to light as in Example 1 described, it is found that the coating only draws approx. 120 volts and needs about 6 light intensity units so that a remainder of 60 volts remains. When using the model D device does not give an image.

Example 3

About 50 g of the mixture described in Example 1 will be placed in a glass jar and put on a Gardner paint shaker for about 1 hour ground using steel polishing balls 0.3 cm in diameter as a grinding aid. The deep blue Dispersion is then applied as a coating as described in Example 1 and tested. The coating only takes about 140 volts and discharges to approx. 60 volts by means of approx 2 light intensity units. With the model D pre-lighting, nan no picture.

Examples 4 and 5 show cases where sand grinding a phthalocyanine-binder mixture provides a useful photosensitive dispersion, while this is the case with ball meals is not the case. You can see that with the same '. The conversion of phthalocyanine by ball milling is difficult, if at all possible.

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example

A mixture of 196 g Chlorowax, 196 g Arotap SP8911-7-7, 66 g SR-82, 22 g alpha-phthalocyanine (from American Cyanamid) and 150 g of toluene is placed in an L-3-J sand mill and milled as described in Example 1 for about 2 hours. then one brings the Geraisch as described in Example 1 as a coating on. and test it. The blue-green layer absorbs 500 volts and discharges itself to 60 volts by means of 4.8 light intensity units. An electrostatic image can be formed, developed and transferred as described in Example 1

Example 5

The following materials are put into a 4 liter ball mill, about 1/3 of which is filled with flint stones of 1.2 cm diameter is filled, and then ground for about 20 hours at 140 RPM:

144 g alpha form of the metal-free phthalocyanine (from

American Cyanamid),
960 g Arotap EP8911-7-7,
328 g silicone resin SR-82,
144 g Syloid 244, a silicic acid pigment (from WR

Grace and Co,),
• 960 g Chlorowax 70-LP,
3000 g of toluene. ·

The dispersion is described as in Example 1 as ttber «U £ j upset. The coating is colored blue, which is for the alpha form des Phthaiοcyanine is characteristic. The matter never only 240 volts and requires about 3.6 light intensity units for the discharge to approx. 60 volts rest. ' With the Modell-D-Vorrioh- {ung no suitable electrostatic image can be produced * Apparently only part of the pigment was rearranged into the, beta-forra, thereby limiting the photosensitivity of the coating remain.

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Although specific reaction conditions and materials were given in the above examples, other suitable materials can be used and similar results can be obtained. Although sand is the preferred grinding medium, other small bead-like media can also be used for the process according to the invention, for example glass beads, Coors Ceremedia and Minimedia (small ceramic particles in P _e rlen-Forra). Accordingly, the term "sand grinding", as used in the present description and in the claims, also encompasses grinding with small bead-like grinding media other than sand. Meal-. Record procedure that acts as an anti-block agent.

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Claims (10)

Godfather tansp rühe Method for producing the photoconductive layer of a Electrophotographic plate, characterized in that there is a phthalocyanine component and a binder in one - Combined liquid medium, the phthalocyanine either from the pure alpha form or from a mixture of the älpha form with the beta or X form of phthalocyanine and grind the mixture with the sand mill until at least some of the alpha-phthalocyanine is in the "beta" form is converted. 2.) Process according to claim 1, characterized in that _s to use a silicone resin and a chlorinated hydrocarbon as a binder material, a mixture of an alkyd-acrylate resin. " ·. 3.) Method according to claims 1 and 2, characterized in that that sand milling is carried out for about 0.2-2 hours. 4.) Process according to claims 1 - 3, characterized in that » that the layer is applied to a conductive carrier material. ■ 5.) Process according to claim 4, characterized in that one conductive paper used as substrate ». 6.) Process according to claims 1-5 »characterized in that the conversion is carried out at temperatures of about 50 - 05 ⁰ C and that about 50 vol-ji of a» grinding medium is used when grinding. ; ".-""' 7.) The method according to claim 6, characterized in that. that a mixture of an alkyd * acrylate resin, a silicone resin and a chlorinated hydrocarbon is used as the binder material and. that the sand-grinding lasted about 0.75 hours. 109839 / U84 ¹ Γ "! ^Τ ψτττ \,. ";:■■; »ιι» -U- 8.) Process according to claims 1-7, characterized in that that sand is used as the grinding medium. 9.) Process according to Claims 1-7, characterized in that the grinding medium used is glass beads or small ceramic particles used in psyllium form. 10.) Electrophotographic plate with a photoconductive one Layer obtained by the method according to claims 1-9 was produced. 109839/1484