Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/124—Duplicating or marking methods; Sheet materials for use therein using pressure to make a masked colour visible, e.g. to make a coloured support visible, to create an opaque or transparent pattern, or to form colour by uniting colour-forming components
  • B41M5/132—Chemical colour-forming components; Additives or binders therefor
  • B41M5/136—Organic colour formers, e.g. leuco dyes
  • B41M5/145—Organic colour formers, e.g. leuco dyes with a lactone or lactam ring
• • 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
  • Y10T428/25—Web or sheet containing structurally defined element or component and including a second component containing structurally defined particles
  • Y10T428/254—Polymeric or resinous material
• • 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]
  • Y10T428/31844—Of natural gum, rosin, natural oil or lac

Definitions

• a pressure-sensitive transferring sheet adapted for use with another sheet having an electron accepting layer, comprising a support having thereon a pressure-rupturable microcapsule layer, said microcapsule containing an oil having dissolved therein as a color former at least one phthalide compound represented by the following general formula wherein X X X X R R R and R are described hereinafter, is disclosed.
• the present invention relates generally to a pressuresensitive copying paper and more particularly it relates to a pressure-sensitive copying paper having a microcapsule layer containing a phthalide compound as a color former.
• Pressure-sensitive copying papers are usually composed of a transferring sheet having thereon a layer of fine capsules containing therein a solution of an electron donating colorless organic compound (hereinafter the organic compound is called the color former) in an oil, and a receiving sheet, having thereon a layer of an electron-accepting solid and a suitable binder.
• the electron accepting solid acid there are known acid clay, attapulgite, zeolite, bentonite, kaolin, and the like.
• an organic solvent for dissolving the color former there are illustrated ethylene glycol, chlorobenzene, and chlorodiphenyl.
• Crystal Violet Lactone has widely been used as a purple-color former.
• Crystal Violet Lactone is immediately colored purple-blue when it is brought into contact with an electron-accepting solid acid, there are such disadvantages that the color is weak in light fastness and also the purple-blue vanishes by the action of water.
• Benzoyl Leuco Methylene Blue has been used as a blue-color former.
• the color former When the color former is brought into contact with an electron accepting solid acid, a blue color having good light fastness is formed but the color former has such a disadvantage that it takes a long period of time until it colors.
• An object of the present invention is therefore, to provide pressure-sensitive copying papers containing as a color former the phthalide compound represented by the aforesaid general formula which is immediately colored when it is brought into contact with a solid acid to pro vide a stable purple or blue color having excellent light fastness and water resistance.
• Another object of this invention is to provide pressuresensitive copying papers which can be colored black by using the phthalide compound represented by the aforesaid general formula together with other known color formers.
• R and R each represents a hydrogen atom, a methyl group, or an ethyl group, R represents a phenyl group, with the possibility that said phenyl group may have a methyl group as a substituent, and R represents a methyl group or an ethyl group;
• R and R each represents a hydrogen atom, a methyl group or an ethyl group
• R represents a phenyl group, with the possibility that said phenyl group may have a methyl group or an ethoxy group as a substituent, and R represents a methyl group, an ethyl group or a phenyl group
• X X X and X each represents a chlorine atom
• R and R each represents a hydrogen atom, a methyl group or an ethyl group
• R represents a methyl group, an ethyl group, or a phenyl group, with the possibility that said phenyl group may have a methyl group or an ethoxy group as a substituent, and R represents a methyl group
• the phthalide compound used in this invention represented by the general formula described above may be prepared by reacting the corresponding benzophenonecarboxylic acid and indole or the corresponding benzoyl indole and an aromatic amine for 10-120 minutes at a reaction temperature of 50-140 C., in the presence of a condensing agent such as acetic anhydride or phosphorus oxychloride using, if necessary, a volatile organic inert solvent such as chloroform, benzene, or chlorobenzene, pouring the reaction product in ice-cooled water to hydrolyze the condensing agent, adding the volatile organic inert solvent described above, alkalizing the reaction prod-- uct with an aqueous solution of sodium hydroxide, recovering the solvent layer, and distilling away the solvent therefrom under a reduced pressure.
• a condensing agent such as acetic anhydride or phosphorus oxychloride
• a volatile organic inert solvent such as chloroform, benz
• PRODUCTION EXAMPLE 1 A mixture of 5.0 g. of 4'-(N-methyl-N-pethoxyphenylamino)-5(or 4) dimethylamino-benzophenone-Z-carboxylic acid, 2.0 g. of 1,2-dimethyl indole, and 25 g. of acetic anhydride was heated to 9095 C. for 60 minutes with stirring to cause the reaction. The reaction product thus produced was poured in 750 g. of ice-water to hydrolize the acetic anhydride, and after adding thereto 200 g. of benzene, thepH of the mixture was adjusted to 12 by adding an aqueous solution of sodium hydroxide.
• the benzene layer formed was recovered by decantation and after treating the benzene layer with activated carbon, benzene was distilled away under a reduced pressure. Then, by recrystallizing the residue from an alcohol, 5.0 g. of 3-(4-N-methyl-N-p-ethoxyphenylaminophenyl)-3-( 1, 2-dimethylindole-3-il)-5 (or 6) dimethylaminophthalide represented by the following formula Ha CH3 N AH.
• PRODUCTION EXAMPLE 2 5 (or 6)-dimethylaminophthalide represented by the 01 lowing formula (EH: i
• PRODUCTION EXAMPLE 3 A mixture of 3.0 g. of 4'-(N-methyl-N-p-ethoxypheny1- amino)-5 (or 4) dimethylamino-benzophenone-2-carboxylic acid, 1.8 g. of l-ethyl-Z-phenylindole, and 15 g. of acetic anhydride was heated to 95 C. for 60 minutes with stirring. Then, the reaction product thus obtained was treated as in Production Example 1 to provide 2.7 g.
• PRODUCTION EXAMPLE 4 To 30 g. of monochlorobenzene were added 3.8 g. of 1- methyl-2phenyl-3- [2-carboxy 5(or 4) dimethylaminobenzoyl]-indole and 1.9 g. of p-methyldiphenylamine and thereafter, 3.1 g. of phosphorus oxychloride was added to the mixture. The resultant mixture was heated to 85-90 C.
• PRODUCTION EXAMPLE 6 To 30 g. of monochlorobenzene were added 3.3 g. of 4-(o-toluidino)-benzophenone-Z-carboxylic acid and 1.5 g. of 1,2-dimethylindole and then 3.1 g. of phosphorus oxychloride was further added to the mixture. The resultant mixture was heated to 75-80 C. for 120 minutes with stirring and the reaction product was treated as in Production Example 1 to provide 3.4 g.
• PRODUCTION EXAMPLE 7 M mi-(a as a light-brown color former having a melting point of 103-109 C. When a toluene solution of the color former was brought into contact with an acid clay layer formed on a paper, the color former was immediately colored purple.
• PRODUCTION EXAMPLE 8 A mixture of 2.9 g. of 2-ethyl-3-(2-carboxybenzoyl)- indole, 2.1 g. of N-ethyldiphenylamine, and 2.9 g. of zinc chloride was heated to 120-130 C. for 180 minutes with stirring to cause the reaction. The reaction product was 6 treated as in Production Example 1 to provide 3.1 g. of 3 (4 N ethyl-N-phenyl-amino-phenyl)-3-(2-ethylindole-3-il)-phthalide represented by the following formula Q- -Q-l-Q as a light-brown color former having a melting point of 97 C. When a toluene solution of the color former thus obtained was brought into contact with an acid clay layer formed on a paper, the color former was immediately colored purple.
• PRODUCTION EXAMPLE 9 A mixture of 2.8 g. of 4'-dimethylamino-3,4,5,6-tetrachlorobenzophenone-Z-carboxylic acid, 1.0 g. of 1,2-dimethylindole, and 15 g. of acetic anhydride was heated to 90-98 C. for minutes with stirring to cause the reaction. The reaction product thus obtained was treated as in Production Example 1 to provide 3.0 g. of 3-(4-dimethylaminophenyl) 3-(1,2-dimethylindole-3-il)-4,5,6,7- tetrachlorophthalide represented by the following formula as a light-yellow-white color former having a melting point of 223226 C. When a benzene solution of the color former thus obtained was brought into contact with an acid clay layer formed on a paper, the color former was immediately colored blue.
• PRODUCTION EXAMPLE 10 A mixture of 2.8 g. of 4-dimethylamino-3,4,5,6-tetrachlorobenzophenone-Z-carboxylic acid, 1.6g. of 1-methyl- Z-phenylindole, and 15 g. of acetic anhydride was heated to l35l36 C. for 30 minutes with stirring to cause the reaction. Then the reaction product was treated as in Production Example 1 to provide 2.8 g. of 3-(4-dimethylaminophenyl) 3-(1-methyl-2-phenylindole-3-il)-4,5,6,7- tetrachlorophthalide represented by the. following formula CHa as a light-yellow color former having a melting point of 239243 C. When a benzene solution of the color former thus obtained was brought into contact with an acid clay layer formed on a paper, the color former was immediately color green-blue.
• PRODUCTION EXAMPLE 11 A mixture of 2.5 g. of l-ethyl-2-phenyl-3-(2-carboxy- 3,4,5,6tetrachlorobenzoyl)-indole, 0.6 g. of dimethylaniline, and g. of acetic anhydride was heated with stirring to 135-136 C. for 30 minutes to cause the reaction. Then the reaction product obtained was treated as in Production Example 1 to provide 2.1 g.
• PRODUCTION EXAMPLE 12 C-CHa i CH3 as a light-yellow color former having a melting point of 162-168 C.
• the color former was immediately colored blue.
• PRODUCTION EXAMPLE 13 A mixture of 1.0 g. of 4'-(N-methyLN-p-ethoxyphenylamino)-3,4,5,6 tetrachlorobenzophenone 2 carboxylic acid, 0.3 g. of 1,2-dimethylindole, and 5.0 g. of acetic anhydride was heated with stirring to 135-136" C. for 30 minutes to cause the reaction and the reaction product obtained was treated as in Production Example 1 to provide 1.0 g.
• the process described in the specifications of US. Pats. 2,548,366, 2,800,457, or 2,800,458, that is, the process of producing microcapsules by utilizing the phenomenon of forming composite coacervations may be employed.
• the amount of the color former to be used is generally 0.55.0% by weight based on the weight of the organic solvent described above, such as ethylene glycol, chlorobenzene, and chlorodiphenyl.
• the pressure-sensitive copying paper of this invention in which the phthalide compound represented by the afore- Said general formula is used as a color former is colorless or has a very faint yellow character before use, but when the pressure-sensitive copying paper is pressed locally by handwriting or typewriting, purple or blue coloring occurs instantly. Moreover, the color density of the color thus formed is high and the light and water resistance thereof are excellent.
• a pressure-sensitive copying paper capable of providing deep-black copying can be obtained unaccompanied with any adverse influences, such as, desensitization.
• EXAMPLE 1 In 100 g. of trichlorodiphenyl was dissolved 1.5 g. of 3-(4-N-methyl-N-p-ethoxyphenylamino-phenyl)-3 (1,2- dimethylindole-3-il)-5 (or 6)-dirnethylaminophthalide and then 20 g. of gum arabic and g. of water were added to the solution at 50 C. followed by emulsification. To the emulsion were added 20 g. of acid-treated gelatin and 160 g. of water and thereafter the pH of the emulsion was adjusted to 5 by adding acetic acid with stirring. Then, 500 g.
• EXAMPLE 2 An upper sheet was prepared by following the same procedure as in Example 1 except that 1.5 g. of 3-(4-N- methyl-N-p-ethoxyphenylaminophenyl)-3-(1 methyl 2- phenylindole--il)-5(or 6)-dimethylaminophthalide was used as the color former and when the upper sheet was placed on the under sheet so that the microcapsule layer was closely brought into contact with the acid clay layer of the under sheet and a localized pressure was applied onto them by handwriting, the areas of the acid clay layer thus pressed were immediately colored blue. By testing the color former thus colored blue with respect to light fastness, it was confirmed that the color former thus colored had sufiicient stability for practical use. The colored color formed also was excellent in water resistance.
• EXAMPLE 3 A colorless upper sheet was prepared by following the same procedure as in Example 1 except that 1.5 g. of 3-(4- N methyl-N-p-ethoxyphen'ylamino-phenyl)-3-( 1-ethyl-2- phenylindole-3-il)-5 (or 6 dimethylaminophthalide was used as the color former and when the upper sheet was placed on the under sheet so that the capsule layer was closely brought into contact with the acid clay layer of the under sheet and a localized pressure was applied onto them by handwriting, the areas of the acid clay layer thus pressed were immediately colored blue. By testing the color former thus colored blue with respect to light fastness, it was confirmed that the color former thus colored had sufiicient stability for practical use. The color former colored also has excellent water resistance.
• EXAMiPLE 4 A colorless upper sheet was prepared by follovn'ng the same procedure as in Example 1 except that 1.5 g. of 3- (4-N-p-methylphenylaminophenyl)-3 (1 methyl 2- phenylindole-3-il)-5(or 6)-dimethylaminophthalide was used as the color former and when the upper sheet was placed on the under sheet so that the capsule layer of the upper sheet was closely brought into contact with the acid clay layer of the under sheet and a localized pressure was applied onto them by handwriting, the areas of the acid clay layer thus pressed were immediately colored blue. -By testing the color former thus colored blue, it was confirmed that the color former thus colored had sufiicient stability for practical use. The colored color former also was excellent in water resistance.
• a colorless upper sheet was prepared by following the same procedure as in Example 1 except that 1.5 g. of 3-(4- N-methyl-N-phenylarninophenyl)-3-(l-methyl-Z phenylindole-3-il)-5(or 6)-diethylaminophthalide was used as the color former and when the upper sheet was placed on the under sheet so that the capsule layer of the upper sheet was closely brought into contact with the acid clay layer of the under sheet and a localized pressure was applied onto them by handwriting, the areas of the acid clay layer thus pressed were immediately colored blue. By testing the color former thus colored in blue with respect to light fastness, it was confirmed that the colored color former had sufficient stability for practical use. The colored color former also was excellent in water resistance.
• a colorless upper sheet was prepared by following the same procedure as in Example 1 except that 1.5 g. 3-(4'N- o methylphenylaminoph'enyl) 3-(1,2-dimethylindole-3-il) phthalide was used as the color former and when the upper sheet was placed on the under sheet so that the capsule layer of the upper sheet was closely brought into contact with the acid clay layer of the under sheet and a localized pressure was applied onto them by handwriting, the areas of the acid clay layer thus pressed were immediately colored purple. By testing the color former thus colored purple with respect to light fastness, it was con firmed that the colored color former had sufficient stability for practical use. The colored color former also was excellent in water resistance.
• EXAMPLE 7 A colorless upper sheet was prepared by following the same procedure as in Example 1 except that 1.5 g. of 3 (4-N-methyl-N-phenylaminophenyl)-3-(2-ethylind0le- 3-il)-5 (or 6)-diethylaminophthalide was used on the under sheet so that the capsule layer of the upper sheet was closely brought into contact with the acid clay layer of the under sheet and a localized pressure was applied onto them by handwriting, the areas of the acid clay layer thus pressed were immediately colored purple. -By testing the color former thus colored purple with respect to light fastness, it was confirmed that the color former thus colored purple had sufficient stability for practical use. The colored color former also was excellent in water resistance.
• EXAMPLE 8 A colorless upper sheet was prepared by following the same procedure as in Example 1 except that 2.0 g. of 3- (4 N ethyl-N-phenylaminophenyl)-3-(2-ethylindole-3- il)-phthalide was used as the color former and when the upper sheet was placed on the under sheet so that the capsule layer of the upper sheet was closely brought into contact with the acid clay layer of the under sheet and a localized pressure was applied onto them by handwriting, the areas of the acid clay layer thus pressed were immediately colored purple. By testing the color former thus colored purple with respect to light fastness, it was confirmed that the color former thus colored purple had suflicient stability for practical use. The colored color former also was excellent in water resistance.
• EXAMPLE 9 A colorless upper sheet was prepared by following the same procedure as in Example 1 except that 1.5 g. of 3 (4-dimethyla'minophenyl)-3-(1,2-dimethylindole-3-il)- 4,5,6,7-tetrachlorophthalide was used as the color former and when the upper sheet was placed on the under sheet so that the capsule layer of the upper sheet was closely brought into contact with the acid clay layer of the under sheet and a localized pressure was applied onto them by handwriting, the areas of the acid clay layer thus pressed were immediately colored blue.
• 3 (4-dimethyla'minophenyl)-3-(1,2-dimethylindole-3-il)- 4,5,6,7-tetrachlorophthalide was used as the color former and when the upper sheet was placed on the under sheet so that the capsule layer of the upper sheet was closely brought into contact with the acid clay layer of the under sheet and a localized pressure was applied onto them by handwriting, the areas of the acid clay layer thus pressed were
• EXAMPLE A colorless upper sheet was prepared by following the same procedure as in Example 1 except that 1.5 g. of 3- (4 dimethylaminophenyl) -3- 1-methyl-2-phenylindole-3- il) 4,5,6,7-tetrachlorophthalide was used as the color former and when the upper sheet was placed on the under sheet so that the capsule layer of the upper sheet was closely brought into contact with the acid clay layer of the under sheet and a localized pressure was applied onto them by handwriting, the areas of the acid clay layer thus pressed were immediately colored green-blue. By testing the color former thus colored green-blue with respect to light fastness, it was confirmed that the colored color former had suflicient stability for practical use. The colored color former was also excellent in water resistance.
• EXAMPLE 11 A colorless upper sheet was prepared by following the same procedure as in Example 1 except that 1.5 g. of 3- (4 dimethylaminophenyl) 3-(l-ethyl-2-phenylindole-3- il) 4,5,6,7 tetrachlorophthalide was used as the color former and when the upper sheet was placed on the under sheet so that the capsule layer of the upper sheet was closely brought into contact with the acid clay layer of the under sheet and a localized pressure was applied to them by handwriting, the areas of the acid clay layer thus pressed were immediately colored greenish blue. By testing the color former thus colored with respect to light fastness, it was confirmed that the colored color former had sufficient stability for practical use. The colored color former was also excellent in water resistance.
• EXAMPLE 12 A colorless upper sheet was prepared by following the same procedure as in Example 1 except that 2.0 g. of 3 (4 o toluidinophenyl)-3-( 1,2-dimethylindole-3-il)- 4,5,6,7-tetrachlorophthalide was used as the color former and when the upper sheet was placed on the under sheet so that the capsule layer was closely brought into contact with the acid clay layer of the under sheet and a localized pressure was applied onto them by handwriting, the areas of the acid clay layer thus pressed were immediately colored blue. By testing the color former thus colored blue with respect to light fastness, it was confirmed that the colored color former had sufiicient stability for practical use.
• EXAMPLE 13 A colorless upper sheet was prepared by following the same procedure as in Example 1 except that 2.0 g. of 3- (4 N-methyl-N-p-ethoxyphenylaminophenyl)-3-(1,2-dimethylindole 3-il)-4,5,6,7-tetrachlorophthalide was used as the color former and when the upper sheet was placed on the under sheet so that the capsule layer was closely brought into contact with the acid clay layer of the under layer and a localized pressure was applied onto them by handwriting, the areas of the acid clay layer thus pressed were immediately colored blue. By testing the color former thus colored blue with respect to light fastness, it was confirmed that the colored color former had sufficient stability for practical use. The colored color former also was excellent in water resistance.
• EXAMPLE 14 A colorless upper sheet was prepared by following the same procedure as in Example 1 except that 1.5 g. of 3- (4 diethylaminophenyl) 3-(Z-ethylindole-B-il)-4,5,6,7- tetrachlorophthalide was used as the color former and when the upper sheet was placed on the under sheet so that the capsule layer of the upper sheet was closely brought into contact with the acid clay layer of the under sheet and a localized pressure was applied onto them by handwriting, the areas of the acid clay layer thus pressed were immediately colored blue. By testing the color former thus colored blue with respect to light fastness, it was confirmed that the colored color former had sufficient stability for practical use.
• EXAMPLE 15 An upper sheet was prepared by following the same procedure as in Example 1 except that 0.5 g. of 3-(4-N- methyl-N-p-ethoxyphenylaminophenyl) 3 (l-methyl-Z- phenylindole 3 il)-5 (or 6)-dimethylaminophthalide, 0.8 g. of o-hydroxybenzalacetophenone, 0.8 g. of Rhodamine Banilinolactam, 0.2 g. of Crystal Violet Lactone, and 0.2 g. of Malachite Green Lactone were used as the color formers.
• EXAMPLE 16 An upper sheet was prepared by following the same procedure as in Example 1 except that 0.5 g. of 3-(4-dimethylaminophenyl)-3-(1,2-dimethylindole-3-il) 4,5,6,7- tetrachlorophthalide, 0.8 g. of o-hydroxybenzalacetophenone, 0.2 g. of Crystal Violet Lactone, 0.8 g. of Rhodamine Bam'linolactam, and 0.2 g. of Malachite Green Lactone were used as the color formers.
• a localized pressure was applied onto them by handwriting the areas of the acid clay layer thus pressed were immediately colored black. The color thus formed black was very stable and also excellent in water resistance.
• a pressure-sensitive transferring sheet adapted for use with another sheet having an electron-accepting layer, comprising a support and, coated on said support, a layer containing pressure rupturable microcapsules, said microcapsules containing an oil and dissolved therein a color former comprising at least one phthalidc compound represented by the general formula phenyl group or a methyl substituted phenyl group, and R represents a methyl group or an ethyl group;
• R and R each represents a hydrogen atom, a methyl group or an ethyl group, R represents a phenyl group or a methyl-substituted or ethoxy-substituted phenyl group, and R represents a methyl group, an ethyl group or a phenyl group;
• R and R each represents a hydrogen atom, 'a methyl group or an ethyl group, R represents a methyl group, an ethyl group, a phenyl group or a methyl-substituted or an ethoxy-substituted phenyl group, and R represents a methyl group, and ethyl group, or a phenyl group.
• phthalide compound is selected from the group consisting of 3-(4- N-methyl-N-p-ethoxyphenylamino-phenyl) 3 (1,2 dimethylindole-3-il)-5- (or 6)-dimethylaminophthalide,

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Color Printing (AREA)
• Indole Compounds (AREA)
• Furan Compounds (AREA)
• Plural Heterocyclic Compounds (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=26380461

Family Applications (1)

Country Status (7)

Cited By (3)

Families Citing this family (6)

• 1971
  • 1971-05-11 IE IE588/71A patent/IE35853B1/xx unknown
  • 1971-05-14 GB GB1506771A patent/GB1310322A/en not_active Expired
  • 1971-05-14 FR FR7117619A patent/FR2090067B1/fr not_active Expired
  • 1971-05-14 DE DE2124084A patent/DE2124084B2/de active Pending
  • 1971-05-14 CA CA112990A patent/CA933356A/en not_active Expired
  • 1971-05-14 ES ES391549A patent/ES391549A1/es not_active Expired
  • 1971-05-17 US US3736168D patent/US3736168A/en not_active Expired - Lifetime

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