Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G5/00—Recording-members for original recording by exposure, e.g. to light, to heat or to electrons; Manufacture thereof; Selection of materials therefor
  • G03G5/005—Materials for treating the recording members, e.g. for cleaning, reactivating, polishing

Definitions

• ABSTRACT A process for bleaching an electrophotographic photosensitive layer having an image thereon, the image containing a lake pigment soluble in an acid to obtain an improved color print which comprises treating at room temperature the colored electrophotographic photosensitive layer composed of a dispersion comprising zinc oxide, resinous binder and a dye selected from the group consisting of triphenylmethane and xanthene dyes and pdimethylaminobenzylidene rhodanine with a bleaching solution containing (1) 30 to 80% by weight of a solvent for the day, (II) 0.01 to 20% by weight of an alkali hydroxide and at least one of (III) less than 10% by weight of an organic solvent capable of dissolving or slightly swelling the resinous binder and (IV) a cationic active agent thereby changing the photosensitive layer substantially white, and then washing the thus treated layer with a washing liquid comprising at least one of the components (I) and (III) or with the washing liquid added with acid.
• a washing liquid comprising at least
• the photosensitive layer usually comprises a dispersion of zinc oxide in a resinous binder, such as a polyvinyl resin, e.g., polystyrene, polyvinylacetate, polyvinyl chloride, etc., and copolymers of these, the silicone resins, cellulose esters and cellulose ethers, and the acrylic resins, e.g., the poly (methacrylates), the poly(methyl methacrylates), etc. These resins are hydrophobic and must have good electrical insulating properties.
• Various optical sensitizers are used to extend the optical sensitivity of the zinc oxide. These include triphenylmethane dyes, such as Rose Bengal, Fluorescein, Crystal Violet, etc., ketoimine dyes, such as Auramine B, etc., xanthene dyes, such as Rhodamine B, etc.
• the coloration of photosensitive layer can be decreased by exposing said layer in a lighted place for a prolonged period because of relatively inferior light fastncss of sensitizing dye usually employed in the photosensitivelayer.
• the fairly dense coloration in highly sensitive layer requires, however, extremely long period for realizing appropriate bleaching.
• the layer thus bleached has a drawback of retaining yellowish hue due to decomposition product resulting from sensitizing dye. Besides, apart from the drawbacks connected directly with dye, the prolonged exposure to light is impractical since this will lead to deterioration of mechanical properties of photosensitive layer itself and to fading of obtained image.
• the purpose of this invention is to provide a novel process for bleaching electrophotographic photosensitive layer containing dye.
• Another purpose of this invention is to provide a bleaching process particularly effective for electrophotographic process utilizing developer containing toner composed of lake pigment susceptible to acid.
• Still another purpose of this invention is to provide a process enabling bleaching of electrophotographic photosensitive layer within a short period and without heating.
• the purpose of this invention is to provide a process for bleaching electrophotographic photosensitive layer suitable for use in obtaining color print of high quality by means of highly sensitive electrophotographic photosensitive layer.
• the process of this invention comprises treating colored electrophotographic photosensitive layer composed of a dispersion consisting of zinc oxide, resinous binder and sensitizing dye with a solution containing (I) solvent for said dye, (II) alkali hydroxide and, if necessary, further at least one of (III) organic solvent capable of dissolving or slightly swelling said resinous binder and (IV) cationic surface active agent thereby changing said layer substantially white, and then washing thus treated layer with at least one of the above-mentioned solvents (I) and (III) or said solvents added with acid.
• the bleaching bath according to this invention is essentially composed of the above-mentioned components (I) and (II), whereas the components (Ill) and/or (IV) are suitably incorporated according to the pur-v pose.
• the component (I) of the above-mentioned bleaching bath can be, for example, water, methyl alcohol, ethyl alcohol, isopropyl alcohol, acetone, ethyleneglycol monomethylether, etc.
• the component (II) can be, for example, potassium hydroxide, sodium hydroxide, lithium hydroxide, etc.
• the component (Ill) can be, for example, aromatic solvents such as toluene or xylene, esters such as butyl acetate or ethyl acetate, and ketones such as methylethylketone or methylisobutyl ketone.
• An example of the component (IV) is Nissan Cation MZ-IOO (Nissan Chemical).
• the bleaching bath of this invention is used as follows.
• Binder is always necessary when zinc oxide is used as photoconductive material, but the state of dispersion depends greatly upon the dispersing method as well as affinity between binder and zinc oxide. Thus, in order to remove dye absorbed on the surface of zinc oxide or present in the binder, it is necessary to take the final state of dispersion with resinous binder into consideration.
• the difference of resin used or that of dispersion will be covered by at least one of the components (III) and (IV).
• the component (I) is added in order to dissolve the dye contained in the sensitive layer, and should preferably contain a small amount of acetone, presumably because acetone not only dissolves dyes but also per forms the function of component (III), namely of accelerating bleaching.
• the selection of components (l) and (III) should be cautiously carried out so as that they do not deteriorate the sensitive layer nor the image formed thereon.
• the amount of solvent for the resinous binder should preferably be less than wt.% in bleaching bath when the resinous binder is not cross linked, although the photosensitive layer itself is not attacked in the course of bleaching even if the components (I) and (III) are composed of abundant amount of highly capable solvents such as ketones, esters, cellosolve, aromatic hydrocarbons or chlorinated hydrocarbons, if the resinous binder in the photosensitive layer is crosslinked and thus is hardly soluble against most solvents.
• Resinous binder in cured state facilitates bleaching procedure and enables the use of simple mechanical operation in removing bleaching solution from the surface of photosensitive layer, such as mechanical squeezing.
• an effective method consists of adding a substance which is insoluble in the bleaching bath and which absorbs water, such as Molecular sieve (Linde Corp., U.S.A.), Silica gel or alumina gel. In this way, the incorporation of water vapor into the bleaching bath caused by the evaporation of volatile components in said bath cannot result in any undesirable effect.
• a substance which is insoluble in the bleaching bath and which absorbs water such as Molecular sieve (Linde Corp., U.S.A.), Silica gel or alumina gel.
• the concentration of water in bleaching bath should preferably be less than 10 wt.% when lake pigment is contained in toner.
• the component (I) which at the same time works as the solvent for alkali hydroxide, is generally employed in an amount of 80 wt.% in the bleaching bath.
• methanol and ethanol do not show the function of swelling the resinous binder, whereas acetone performs a function as the component (III).
• the resinous binder is composed of polyvinyl acetate which is relatively soluble in methanol, the concentration thereof should be decreased since, in this case, methanol works also as the component (III).
• the component (III) can be employed in an elevated concentration when the binder is crosslinked. Otherwise, the solvent for binder should be removed or should be less than 10 wt.%.
• the bleaching treatment can be accelerated at an elevated temperaturc, but in this case sufficient caution is required since the influ ence of the component (Ill) becomes stronger.
• the component (II) in the bleaching bath of this in vention is thus selected according to the preceding discussion.
• potassium hydroxide and then sodium hydroxide are most desirable because of the solubility in said organic solvents.
• the concentration of alkali hydroxide in the bleaching bath is generally between 0.01 and 20 wt.%, preferably between 0.1 and 2 wt.%.
• the bleaching bath with elevated concentration of alkali hydroxide is employed for realizing accelerated treatment.
• (IV) cationic surface active agent is also suitable for treating electrophotographic photosensitive layer containing certain species of dyes.
• the bleaching operation can be carried out at a temperature as low as possible since the majority of the solvents belonging to the categories (I) and (III) in the bleaching bath has elevated volatility and may be hazardous to human body when inhaled in a large amount.
• the bleaching bath according to this invention is particularly effective for the use at the room temperature or therearound, and proves to be far stronger than bleaching solutions using organic acids. Naturally the activity of the bath is increased when higher temperature is employed, but suitable measure against danger should be taken in this case.
• EXAMPLE 1 100 g of zinc oxide. 20 g of vinyl chloridevinylacetate copolymer and 60 g n-butyl acetate are blended for hours in a porcelain ball mill to obtain white dispersion, which is successively added with 3 mg of fluorescein, 3 mg of rose bengale and 3 mg of brilliant blue FCF dissolved in 10 ml of methyl alcohol. After sufficient agitation, the obtained colored dispersion is appropriately diluted with n-butyl acetate and applied onto aluminum foil to obtain a layer of 10 microns thick after drying. Thus obtained electrophotographic photosensitive layer is colored in pale purple. This layer is subjected to electrostatic charging, imagewise exposure and cascade development with toner containing carbon black followed by heat fixing.
• the photosensitive layer having formed image thereon is dipped in said solution for 30 seconds. After this period, the layer showed black clear image on white background.
• the layer is successively washed with methyl alcoholacetone 1:1 mixture and dried.
• EXAMPLE 2 The white dispersion is prepared in a same manner as in Example 1, which is then added with 3 mg of p-dimetbyl-aminobenzylidene rhodanine, 3 mg of erythrosin and 3 mg of patent blue dissolved in 10 ml of ethyleneglycol monomcthyl ether. After sufficient agitation, the prepared colored dispersion is appropriately diluted with n-butyl acetate and applied onto an aluminum foil to obtain a coating of 10 microns thick after drying.
• Methyl alcohol 40 ml Ethyl alcohol 40 ml Acetone ml nhutyl acetate 5 ml Potassium hydroxide 0.5 g
• EXAMPLE 3 100 g of zinc oxide, 12 g of styrenized alkyd resin (Japan Reichhold, Styresol No. 4400), 8 g of polyisocyanate compound as hardener (Bayer; Desmodule L) and g of n-butyl acetate are blended to obtain white dispersion, which is added then with each 10 mg of fluorescein, rose bengale and brilliant blue FCF dissolved in 5 ml of methanol. After sufficient agitation, the obtained dispersion is applied onto a paper sheet provided previously with subcoating so as to obtain a coating of 10 microns thick after drying. After drying, the binder is hardened by keeping the sheet in a thermostat box of 50C for 12 hours.
• the same photosensitive layer having multicolor image thereon composed of three toners respectively of benzidine yellow GR, brilliant Carmine 6B and phthalocyanine blue shows greater whiteness without deterioration of image itself by the treatment with the bleaching bath containing potassium hydroxide for 30 seconds at 25C.
• the photosensitive layer of Example 3 is treated with the above-mentioned bleaching bath for 60 seconds at 25C and then washed with methyl alcohol.
• a process for bleaching an electrophotographic photosensitive layer having an image thereon, said image containing a lake pigment soluble in an acid to obtain an improved color print which comprises treating at room temperature the colored electrophotographic photosensitive layer composed of a dispersion comprising zinc oxide, resinous binder and a dye selected from the group consisting of triphenylmethane and xanthene dyes and p-dimethylaminobenzylidene rhodanine with a bleaching solution containing (1) 30 to 80% by weight ofa solvent for said dye and (II) 0.01 to 20% by weight of an alkali hydroxide thereby changing said photosensitive layer substantially white, and then washing the thus treated layer with a washing liquid comprising at least one of said component (I) and (Ill) an organic solvent capable of dissolving or slightly swelling said resinous binder or with said washing liquid added with acid.
• a washing liquid comprising at least one of said component (I) and (Ill) an organic solvent capable of dissolving or slightly swelling said resinous bin
• a process for bleaching an electrophotographic photosensitive layer having an image thereon, said image containing a lake pigment soluble in an acid to obtain an improved color print which comprises treating at room temperature the colored electrophotographic photosensitive layer composed of a dispersion comprising zinc oxide, resinous binder and a dye selected from the group consisting of triphenylmethane and'xanthene dyes and p-dimethylaminobenzylidene rhodanine with a bleaching solution containing (l) 30 to 80% by weight of a solvent for said dye, (II) 0.01 to 20% by weight of an alkali hydroxide and (III) less than 10% by weight of an organic solvent capable of dissolving or slightly swelling said resinous binder thereby changing said photosensitive layer substantially white, and then washing the thus treated layer with a washing liquid comprising at least one of said components (I) and (III) or with said washing liquid added with acid.
• a washing liquid comprising at least one of said components (I) and (III) or with said washing
• a process for bleaching an electrophotographic photosensitive layer having an image thereon, said image containing a lake pigment soluble in an acid to obtain an improved color print which comprises treat ing at room temperature the colored electrophotographic photosensitive layer composed of a dispersion comprising zinc oxide, resinous binder and a dye selected from the group consisting of triphenylmethane and xanthene dyes and p-dimethylaminobenzylidene rhodanine with a bleaching solution containing (I) 30 to 80% by weight ofa solvent for said dye, (II) 0.01 to by weight of an alkali hydroxide and (IV) a cationic surface active agent thereby changing said photosensitive layer substantially white, and then washing the thus treated layer with a washing liquid comprising at least one of said component (I) and (Ill) an organic solvent capable of dissolving or slightly swelling said resinous binder or with said washing liquid added with acid.
• a washing liquid comprising at least one of said component (I) and (Ill)
• a process for bleaching an electrophotographic photosensitive layer having an image thereon, said image containing a lake pigment soluble in an acid to obtain an improved color print which comprises treating at room temperature the colored electrophotographic photosensitive layer composed of a dispersion comprising zinc oxide, resinous binder and a dye selected from the group consisting of triphenylmethane and xanthene dyes and p-dimethylaminobenzylidene rhodanine with a bleaching solution containing (I) 30 to by weight of a solvent for said dye, (II) 0.01 to 20% by weight of an alkali hydroxide and at least one of (III) less than 10% by weight of an organic solvent capable of dissolving or slightly swelling said resinous binder and (IV) a cationic active agent thereby changing said photosensitive layer substantially white, and then washing the thus treated layer with a washing liquid comprising at least one of said components (I) and (III) or with said washing liquid added with acid.
• a washing liquid comprising at least one of
• alkali hydroxide is potassium hydroxide, sodium hydroxide, lithium hydroxide.

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Citations (3)

• 0
  • BE BE754261D patent/BE754261A/fr unknown
• 1969
  • 1969-07-31 JP JP44060617A patent/JPS4835380B1/ja active Pending
• 1970
  • 1970-07-28 FR FR7027730A patent/FR2055694A5/fr not_active Expired
  • 1970-07-29 CA CA089434A patent/CA924163A/en not_active Expired
  • 1970-07-31 NL NL7011353A patent/NL7011353A/xx unknown
  • 1970-07-31 US US060117A patent/US3901694A/en not_active Expired - Lifetime
  • 1970-07-31 GB GB1289009D patent/GB1289009A/en not_active Expired
  • 1970-07-31 DE DE2038207A patent/DE2038207C3/de not_active Expired

Patent Citations (3)

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