Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H19/00—Coated paper; Coating material
  • D21H19/80—Paper comprising more than one coating
  • D21H19/82—Paper comprising more than one coating superposed
  • D21H19/822—Paper comprising more than one coating superposed two superposed coatings, both being pigmented
• • 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, to electrons; Manufacture thereof; Selection of materials therefor
  • G03G5/10—Bases for charge-receiving or other layers
  • G03G5/101—Paper bases
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31855—Of addition polymer from unsaturated monomers
  • Y10T428/3188—Next to cellulosic
  • Y10T428/31895—Paper or wood

Definitions

• the surface-coating material substantially completely prevents mass penetration of liquid into the porous material, but since the surface-coating material is not entirely cohesive or entirely film-forming, tiny pinholes are formed in the surface of the surface-coating material. This causes problems when a liquid is later applied to the porous material coated with the surface-coating material because the liquid penetrates into the porous material.
• a pinhole-filling dispersion which comprises a liquid and a finely dispersed substance therein whereby the liquid easily penetrates through the pinholes in the surface-coating material carrying the finely dispersed Substance, wherealter, the finely dispersed substance coagulates" in the pinholes and blocks them completely, whereby the combined surface-coating material/pinhole-clogging material forms a substantially impermeable film 16 Claims, N0 Drawings METHOD OF PROCESSING POROUS MATERIALS BACKGROUND OF THE INVENTION 1.
• the present invention relates to a method for processing a porous material, and, more particularly, to a method for removing pinholes through which a liquid penetrates into the porous material.
• Electrophotographic light-sensitive materials comprising a support, such as paper, having provided thereon a zinc oxide/resin dispersion type photoconductive insulating layer or an organic photoeonductive layer mainly comprising polyvinyl carbazole, are widely used in the copying field.
• the back surface or surface free of light-sensitive layer of such a material is also provided with a resin layer, and fine pinholes unavoidably lie scattered throughout the layer. A liquid developer is liable to penetrate through these pinholes into the interior of the paper support, resulting in the formation of undesirable spot-like stains on the back side of a finished print, as well as increasing the drying load and consumption of developer.
• the former method is economically disadvantageous since the film must be thick.
• resins such as polyvinyl alcohol must be applied in an amount of about 5 g/m to the back side of the lightsensitive material. This seriously affects the mechanical properties of the resulting paper and imposes additional restrictions on the processing of the opposite surface from the point of curling balance or the like, as well as lowering the flexibility and feel which is characteristic of paper.
• the application of a resin film in such an amount is not preferred.
• resins capable of constituting a closed layer are restricted as to kind, which seriously narrows the degree of freedom in setting up production conditions.
• the latter method involves the defects that it requires complicated apparatus since the processing is conducted in two steps and that non-dryable spots remain as in the first method, though no stains are left after drying since the penetrating liquid contains no toner. These non-dryable spots cause problems in the case of, e.g., obtaining color images and the like by a superposition development.
• the present invention relates to a method for providing a coating film containing extremely few pinholes and, expressed in connection with the above-described use, it provides a base paper for use in electrophotography where liquid penetration is prevented.
• the method of the invention comprises: (a) subject ing the surface of a base material, where penetration of liquid is to be prevented, to processing to prevent a liquid from penetrating therethrough over the almost the whole surface (say, for instance. on the order of 98% and (b) applying to the surface subjected to processing (a) a pinhole-filling dispersion prepared by dispersing fine particles in a liquid which easily penetrates into the interior of the base material through the pinholes, the particles having a diameter less than or approximately the same as that of the pinholes and being capable of stopping up the pinholes.
• step (b) the pinhole-filling dispersion penetrates into the interior of the base material through the pinholes, and the finely dispersed particles agglomerate at the pinholes to prevent the further penetration of the liquid.
• step (a) The first step of the invention (hereinafter referred to as step (a) can be accomplished by various techniques so far known.
• Step (a) does not constitute an essential concept of the invention.
• a resin solution or a resin dispersion to a base material such as paper.
• Resins possess a film-forming property and form an approximately continuous film on the surface of the base material. Of course, there remain microscopically discontinuous portions on the surface, which portions form pinholes.
• Pinholes or penetration points
• a great number of pinholes is more than 20 penetration points/cm?
• An intermediate level is from 5 to l9 penetration points/em.
• a very low level of penetration points is less than 5, preferably less the 4, per cm".
• coated porous materials which have more than 20 penetration points per cm are particularlly amenable to the penetration problem discussed.
• the pinhole/filling dispersion of this invention the number of penetration points can be lowered to less than 4 penetration points/cm?
• the pinhold filling dispersion of the present invention can reduce the number of penetration points per cm to less than 4, and offers excellent affects when the number of pinholes prior to treatment is from 5 to 25 per cm.
• pinhole refers to any small hole through which a solution can penetrate.
• layers which are subject to pinholing and yet which are commercially used in the industry, have pinholes of a size less than about microns.
• the pinhole filling dispersion (or the penetration of the dispersion which is to be prevented) rapidly penetrates initially, for instance, at an penetration rate of about 2 X l0 mm to about 60 X l0mm per second, more commonly from 4 X 10 to 32 X l0"mm"'/sec. After treatment, the rate of penetration is less than one-fifth such a penetration ratev It will he understood from the above that the surfacecoating material of the present invention is not limited in any special manner.
• the surface-coating materials which are subject to the pinholing problem solved by the present invention are resins, and most common of such surface-coating mate rial used to surface coat porous materials are (c) polyalkyl acrylates, methacrylates, alkylacrylates, alkyl methacrylates, copolymers thereof with compatible materials (where any alkyl group in the proceeding materials preferably has 14 carbon atoms), polystyrene, polyvinyl acetate, linear polyesters unsaturated polyesters, alkyd epoxy resins, polyvinyl alcohol, polyvinyl benzyl trimethyl ammonium chloride, copolymers of styrene and butadiene, and the like. It will be apparent to one skilled in the art that it is completely impossible to list every conceivable resin which could be used as a surface coating material, and the above listing shall only be taken as representative.
• step (b) constitutes the basis of the invention.
• processing dispersion those which meet the following requirements suffice:
• the dispersion medium of the processing dispersion is volatile.
• the carrier liquid for the finally dispersed pinholetilling particles is best an easily volatilized petroleum hydrocarbon solvent, an ester, ketone, alcohol, halogenated hydrocarbon or the like. As will be appreciated by one skilled in the art, it is important that the carrier liquid not attack the coating layer since, essentially, one would then be enlarging the pinholes. High volatility is useful because this can be used as one procedure for the coagulation of the finally dispersed pinholefilling material.
• Such materials are petroleum hydrocarbons such as kerosene, hexane, heptane, cyclohcxane, benzene, toluene, xylene, isoparaffins and groin; esters such as carboxilic acid alkyl esters where the carboxylic acid and alkyl group having from I to 4 carbon atoms such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate and butyl lactate; ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; alcohols having from 1 to 3 carbon atoms, such as methanol, ethanol and propanol', halogenated hydrocarbons such as methylene chloride, ethylene chloride, trichloroethylene, tetrachloroethane, carbon tetrachloride and chloroform; mixture thereof and the like.
• esters such as carb
• the material which is finally dispersed in the carrier liquid to serve as a pinhole-fitting or clogging material is not especially limited.
• useful materials will comprise colorless pigments, plastic particles, and plastic coated pigment particles, which are able to coagulate in the pinholes and fill the same.
• Preferred plastic particles are thermoplastic resins having a molecular weight of from about [0,000 to about 200,000 such as polyvinyl chloride, vinyl chloride-vinyl acetate copolymers, styrene butadiene copolymers, polyacrylic acid-alkyl esters (ester moiety having from 1 to 4 carbon atoms), polymethacrylic acid alkyl esters (ester moiety having from 1 to 4 carbon atoms), copolymers of such esters and vinyl chlo ride, styrene, acrylic acid or crotonic acid, or mixtures thereof and the like.
• thermoplastic resins having a molecular weight of from about [0,000 to about 200,000 such as polyvinyl chloride, vinyl chloride-vinyl acetate copolymers, styrene butadiene copolymers, polyacrylic acid-alkyl esters (ester moiety having from 1 to 4 carbon atoms), polymethacrylic acid alkyl esters
• Preferred colorless pigments are pigments such as titanium oxide, zinc oxide, magnesium oxide, aluminum oxide, silicon dioxide, aluminum hydroxide, calcium hydroxide, calcium silicate, potassium silicate, mixtures thereof and the like.
• Preferred plastic coated pigments are the above pigments coated with the above plastics.
• the finally dispersed material should comprise from about 1 to about 20% by volume of the carrier liquid, more preferably 1 to 5% of the carrier liquid. This permits a good transportation rate of the finally dispersed material into the pinholes.
• the size of the finally dispersed particles in the carrier liquid can vary greatly but, however, cannot be greater than the pinhole diameter.
• the pinhole-filling ef fect tends to fall off, with the same tendency being seen with particles below about 0.] micron.
• the present invention will now be explained taking, for instance, the processing of the back surface of a support for use in electrophotography.
• a resin layer is provided on the other surface or back side thereof.
• a processing dispersion As a processing dispersion. a dispersion prepared by dispersing fine particles of a thermoplastic resin in 21 petroleum solvent is utilized. This dispersion is brought into contact with the back side surface for a sufficient period of time, for instance, on the order of 2 seconds to 40 seconds, more generally contact for about 5 to 20 seconds being sufficient. Thereafter, the liquid is completely squeezed out by means of squeezing rollers, followed by drying. Prior to drying, the liquid penetrates into the squeezed surface through the pinholes. The projected area of the penetrated liquid is from about l0 to 20 times to about times that of the pinholes. It has been found that once the thus processed support is dried, the liquid does not penetrate thereinto any more.
• the time of drying and the temperature of drying are, of course important, since if one drys too fast the particles do not have an opportunity to fill up the pinholes. On the other hand, if one drys for too long of a period, the process time is increased which leads to lower process efficiency.
• the time and temperature of drying must be decided on a case by case basis, but the acceptability of any drying procedure is generally easily determined. For instance, drying will, of course, be sufficient to drive off the solvent but at a temperature insufficicnt to actually degrade any of the porous material, coating material or pinhole-filling material.
• an appropriate temperature is selected which ensures carrier liquid drive-off and no harm to the other components and then, after cutting a sample into several strips, different drying times are used until one which provides optimum results is reached. If a desired pinhole filling effect cannot be achieved, then the temperature is either raised or lowered, depending on whether the trend of the results indicate the temperature initially selected was too high or too low. Commonly used temperatures are about 60 to about lC. 1n the present invention, the pressure of treatment is unimportant and, for practical purposes, will always be atmospheric pressure. The temperature of treatment is also unimportant, so long as, of course, the particulate nature of the finally dispersed particles is not altered prior to the coagulating effect desired.
• the pinhole-filling dispersion one resembling the processing solution to be applied to the material during use i.e., one which is similar in composition and viscosity to the processing solution to be applied to the material during practical use.
• the liquid applied to the light-sensitive material at use is a liquid developer which is prepared by dispersing fine carbon black particles or the like of not more than 1 u in particle size in a non-polar carrier liquid having a low viscosity and a low surface tension. Therefore, it is desirable to utilize as the pinhole-filling liquid a liquid having a similar surface tension to that of the liquid developer.
• the dispersed particles are preferably about l p. or less in particle size, and are preferably particles of colorless pigment or resin.
• the surface tension of aqueous pinhole-filling liquids is relatively high, and they will tend to fail to adequately penetrate into very small pinholes. Accordingly, the general rule is that aqueous pinhole-filling systems are to be avoided.
• the main point of the present invention lies in utilizing the phenomenon that when a filling liquid flows through pinholes fine particles contained therein are caught at the pinholes and agglomerate to plug or stop up the pinholes, Such a phenomenon is experienced in the familiar case of. e.g., filtrating a precipitate in a chemical experiment in which case a filter paper he comes impassable in the course of filtration, though the precipitate passes through the filter paper during the first stage.
• polyvinyl alcohol is applied in an amount of about 2 g/m as an aqueous solution to one surface ofa fine quality paper of about 100 g/m in weight.
• the thus formed layer contains a number of pinholes and, when a liquid developer for electrophotography is applied thereto without the processing of the invention, there are observed 20 to 30 pinholes per 1 cm In order to reduce the number of pinholes to several pinholes per 1 cm, it is necessary to again apply thereto polyvinyl alcohol in an amount of 2-3 g/m".
• the method of the invention when the method of the invention is applied to the surface containing 20 30 pinholes per 1 cm there can be obtained an almost completely pinhole-free surface, almost without an increase in the coating amount, as confirmed by measurement. That is, the method of the invention enables one to greatly re cute materials cost and coating amount.
• the pinhole-filling liquid used in the method of the invention may be optionally selected, depending upon the kind of porous material used.
• EXAMPLE 1 A 100 g/m paper of fine quality was used as a base material, and a 15% aqueous solution of polyvinyl alcohol (degree of polymerization ca.7()()) was applied to the wire-coated surface thereof in a dry amount of 2 g/m After drying, it was cut into two pieces.
• a commercially available electrophotographic liquid developer (prepared by dispersing carbon black in a carrier liquid of isoparaffinic hydrocarbons, the particle size of the carbon black being considered to be about 0.1 micron of less) was poured onto the resin-coated surface of one piece, it was left for 10 seconds and then washed well with an isoparaffinic solvent. The whole wirecoated surface was found to be dotted with black spots.
• the frequency of the spots was 22 to 25 per 1 cm Thereafter, a dispersion was prepared by dispersing a vinyl chloride/vinyl acetate copolymer (copolymer ization ratio: :35; polymerization degree; about 260) as fine particles in kerosene based solvent in the following manner.
• the second piece of the processed paper surface was brought into contact with the resulting dispersion for seconds and washed with pure kerosene. Spots were seen as in the case of the aforesaid developer due to the penetration of the liquid.
• the thus processed paper was dried at 70C and passed between calender rolls. When the above-described developer was then poured thereon, it did not penetrate.
• EXAMPLE 2 A 50 g/m office paper was used as a base material, and an aqueous coating solution prepared by mixing parts of an electroconductive resin [ECR-34, made by Dow Chemical C03, poly-vinylbenzyltrimethyl ammo nium chloride in water, containing about 30% nonvolatile components and 50 parts of a 10% aqueous solution of polyvinyl alcohol (degree of polymerization ca. 600) was applied to the felted surface thereof in a dry amount of 1.5 g/m The sample was cut into two pieces.
• ECR-34 electroconductive resin
• polyvinylbenzyltrimethyl ammo nium chloride in water, containing about 30% nonvolatile components
• 50 parts of a 10% aqueous solution of polyvinyl alcohol degree of polymerization ca. 600
• Example 2 When the same developer as in Example 1 was poured onto one piece, there were observed 50 to 60 black spots per 1 cm*.
• a first solution was prepared by dissolving 10 g of polyvinyl acetate (degree of polymerization ca. 550) in 100 cc of acetone.
• a second solution was prepared by adding to 200 ml of cyclohexane 20 ml of a 20% toluene solution of varnish obtained by thermally condensing a rosin-modified phenolformaldehyde resin and linseed oil. 10 cc of the first solution and 200 cc of the second solution were mixed with each other to prepare a processing dispersion.
• EXAMPLE 3 A carbon black-containing original paper of 80 g/m in weight was used as a base material, and an acetone solution of vinyl methyl ether/maleic anhydride copolymer (molecular ratio: 1: 1; degree of polymerization ca. 250) was applied thereto in a dry amount of 1.5 g/m' The sample was cut into two pieces. The thus processed surface contained a number of pinholes. Therefore, upon immersing in an isoparaffinic solvent (lsopar H C Esso Co., Ltd. boiling range 174 1 86C; drying point 1 89C, density 0.757, saturated hydrocarbon 99.3% aromatic hydrocarbons 0.2%, aniline point 83C), random spots were produced due to the penetration of the solvent.
• an isoparaffinic solvent lsopar H C Esso Co., Ltd. boiling range 174 1 86C; drying point 1 89C, density 0.757, saturated hydrocarbon 99.3% aromatic hydrocarbons 0.2%, aniline point 83C
• EXAMPLE 4 5 Grams of gelatin for photographic use (bone gelatin) was weighed and added to ml of distilled water. The gelatin was swollen by allowing it to stand for 30 minutes and then dissolved by heating to 60C while stirring. The thus obtained 5% by weight gelatin aqueous solution was coagulated by placing it in a refrigerator kept at 5C. 10 Grams of the thus coagulated gelatin was charged into a ball mill together with ml of acetone and milled for 10 hours. There was thus obtained a milky white acetone dispersion of gelatin. This acetone dispersion was subjected to centrifuging to collect the gelatin particles.
• a 50 g/m thin paper of fine quality was used as a base material, and an electroconductive resin [Calgon Conductive Polymer 261, made by Calgon Corp; poly (N,N-dimethyl-3,S-methylene piperidinium chloride) having the formula below; 1000 cps viscosity and a 1.085 specific gravity] (wherein n is a positive integer)] was applied as an aqueous solution to the wire-coated surface thereof in an amount of l glm
• the thus processed surface possessed numerous pinholes through which xylol or toluol could pass.
• a method for processing a porous paper coated with a layer of a surface coating of a film-forming resin to reduce or remove pinholes which permit the penetration of a liquid and which exist in the surface coating of a film-forming resin which is capable of nearly preventing penetration of a liquid to the porous material comprises bringing said layer of surfacecoating resin into contact with a pinhole-filling dispersion comprising a liquid and a finely dispersed substance selected from the group consisting of a colorless pigment, a plastic particle or a pigment coated with a plastic therein, said liquid easily penetrating into the interior of the porouspaper through pinholes formed in said surface-coating resin and carrying said finely dispersed substance into said pinholes, whereby said finely dispersed substance fills and seals said pinholes and wherein the rate of penetration of said pinholefilling dispersion is from about 2 X l"mm to about 60 X l0 mm"/sec.
• liquid carrying the finely dispersed substance therein is selected from the group consisting of one or more volatile petroleum hydrocarbons. esters, ketones. alcohols and halogenated hydrocarbons.
• the surface coating resin is a polyalkyl acrylate, polymethacrylate, copolymer of an alkylacrylate, copolymer of an alkylmethacrylate, copolymer of a methacrylate, polystyrene, polyvinyl acetate, linear polyester, unsaturated polyester, alkyd epoxy resin, polyvinyl alcohol, polyvinylbenzyl trimethylammonium chloride or a copolymer of styrene and butadiene.
• pinholes have a diameter of less than about 10 microns and the finely dispersed substance has a size equal to the pinholes.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Photoreceptors In Electrophotography (AREA)

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Cited By (9)

Citations (4)

• 1972
  • 1972-06-09 JP JP5739872A patent/JPS5652304B2/ja not_active Expired
• 1973
  • 1973-06-11 US US05368789 patent/US3911170A/en not_active Expired - Lifetime

Patent Citations (4)

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