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Publication numberUS3632298 A
Publication typeGrant
Publication dateJan 4, 1972
Filing dateNov 14, 1968
Priority dateNov 14, 1968
Publication numberUS 3632298 A, US 3632298A, US-A-3632298, US3632298 A, US3632298A
InventorsFranklin William E, Mack Charles H, Rowland Stanley P
Original AssigneeUs Agriculture
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Cellulose dicyclopentadienemonocarboxylates and a process of durably creasing said by delayed cure
US 3632298 A
Abstract
A cellulosic material is reacted with a monofunctional dicyclopentadiene wherein the functional group is any cellulose-reactive group to produce a material which is self-crosslinking when exposed to elevated temperatures.
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United States Patent William E. Franklin;

Charles R. Mack; Stanley P. Rowland, all of New Orleans, La.

Nov. 14, 1968 Jan. 4, 1972 The United States of America as represented by the Secretary of Agriculture Inventors Appl. No. Filed Patented Assignee CELLULOSE DlCYCLOPENTADIENEMONOCARBOXYLATES AND A PROCESS OF DURABLY CREASING SAID BY DELAYED CURE References Cited OTHER REFERENCES Tedder, Chemical Reviews, Vol. 55, No. 5, pp. 787- 794 (1955) Hamalainen, Textile Research Journal, Vol. 27, pg. 168 (1957) Cruz-Lagrange et al., American Dyestufi Reporter, pp. 428- 430 (1962) Franklin et al., Journal of Organic Chemistry, Vol. 33, pp. 626-632(1968) Primary Examiner-George F. Lesmes Assistant Examiner.l. Cannon Attorneys-R. Hoffman and W. Bier tures.

CELLULOSE DECYCLORENTADIENEMONOCARBOXYLATES AND A PROCESS OF DURABLY CREASHNG SAID BY DELAYED CURE A nonexclusive, irrevocable, royaltyfree license in the invention herein described, throughout the world for all purposes of the US. Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to a process for imparting durable configurations to cellulose textile products. Specifically, this invention relates to the chemical modification of cellulosic textile products to give a stable, modified textile product which can be stored for extended periods and later constrained in a desired configuration and heated to durably set that configuration. More specifically, this invention relates to the attachment of chemical groups which are stable to laundering and to heat at ordinary temperatures, to cellulose. The said chemical groups although stable to heat at ordinary temperatures do dissociate by a retro- Diels- Alder reaction to give a molecule which is lost and reactive groups which remain attached to the cellulose and react with other like groups to introduce crosslinks into the cellulose structure.

By the process of the instant invention cellulosic textiles, garments, and other products can be impregnated with the preferred chemical substances of the invention and stored, then retrieved to be crosslinked by a heating step, thereby imparting creases, pleats, or other desired configurations. This delayed cure process provides a durable treatment.

The main object of this invention is to provide textiletreating compositions, methods, and treated textiles which can be manufactured into garments or other products and sub-' sequently heated to set durable creases, pleats, or other selected configurations in the finished product.

Another object of this invention is to provide treated cellulosic fabrics which are capable of extended storage without special precautions, and which retain their ability to accept heatset creases or other configurations when the garments or other products are manufactured from the stored fabrics and the finished products are heatset. A third object of this invention is to provide treated cellulosic fabrics which have the advantages usually associated with covalent crosslinking after they are heated to set durable creases or other configurations.

It is well known that washandwear and wrinkleresistant 45 finishes for use on cellulosic fabrics are based on covalently bonded cross-links joining the cellulose molecules within the fibers. The establishment of crosslinks binds the fibers, and therefore the fabric, into the configuration present at the time of crosslinking. Because of the covalent character of the crosslinks, the conventional crosslinking processes permanently set the cellulosic fabric in one configuration. The permanently set configuration of crosslinked cellulosic fabrics, despite its desired effects, imparts certain undesirable properties to the treated fabrics. The most important of these undesirable effects is the fact that it is impossible to impart durable creases, pleats or other configurations to the fabric after the finishing process is completed. It is therefore impossible to impart sharp, durable creases or flat seams to garments manufactured from crosslinked cellulose fabrics.

The conventional delayed cure processes overcome some of the disadvantages in the use of crosslinked cellulosic fabrics, but several important disadvantages remain. The pretreated fabrics used in present delayedcure processes are perishable and require special handling during the storage and manufacturing time before the final crosslinking step is completed. The evolution of formaldehyde from the pretreated fabrics creates health problems for employees engaged in handling and manufacturing garments from fabrics treated by delayed cure processes of the prior art. These prior art delayed cure processes require special equipment and critical conditions for successful application.

A more detailed summary of the current state of the art of delayed-cure crosslinking of cellulosic textiles can be found in an article by Edward N. Alexander entitled Deferred- Cure 75 Processes for Durable Press," which appeared in American Dyestuff Reporter, Volume 55, Aug. 1, 1966, pages 28 to 31 (P602 to P605).

Those skilled in the art know that cellulose in the form of fibers can be reacted with compounds containing several types of functional groups to produce cellulose derivatives having these groups attached to the cellulose chain by covalent bonds. Among the types of groups which can react with cellulose are the following: carboxylic acids and derivatives of carboxylic acids, such as acyl halides and anhydrides; alkyl halides, sulfates, and other alkylating agents; organic epoxides; N- methylol amides, N- methylol amines, N- methylol carbamates, and other like N- methylol compounds; compounds containing reactive double bonds, such as vinyl sulfones and acrylic acid derivatives; and other compounds containing functional groups capable of reacting with organic hydroxyl groups. It is also well known that compounds containing two such functional groups, which may be the same or different, and which are both capable of reacting with cellulose, can develop covalent crosslinks in cellulose.

The esterification of cellulose with carboxylic acids or with derivatives of carboxylic acids is a well known and convenient method of attaching various types of organic groups to cellulose. The reaction of cellulose with a solution of a carboxylic acid and trifluoroacetie anhydride in an inert solvent is a particularly convenient method of esterification for fibrous cellulose. An article entitled Preparation and Evaluation of Selected Aliphatic Acid Esters by Cruz- Lagrange, et al., in the American Dyestuff Reporter, Volume 51, No. 12, pages 40-42 (June ll, 1962) describes the esterification of cellulose fabrics with carboxylic acids and trifiuoroacetic anhydride in benzene. This article, however, describes only the reactions with aliphatic monofunctional carboxylic acids and does not mention the use of carboxylic acids having cyclic carbon skeletons. An article entitled The Crosslinking of Cotton Cellulose by Aliphatic Dicarboxylic Acids" by Campbell and Thomas in Textile Research Journal, Volume 35, pages 260-270 (1965) describes the formation of diester crosslinks 40 in cotton fabrics by the use of reactions of cellulose with aliphatic dicarboxylic acids and trifluoroacetic anhydride. The reactions and reagents described in this article, however, cannot be used as the basis for a delayedcure process for crosslinking cellulose.

We now have discovered that cellulose may be reacted with monofunctional reagents containing the dicyclopentadiene carbon skeleton, and that the monofunctionally attached dicyclopentadienyl groups of the resulting modified cellulose dissociate when heated to high temperatures, evolving cyclopentadiene or substituted cyclopentadiene derivatives, leaving cyclopentadienyl or substituted cyclopentadienyl groups attached to the cellulose, and that the cyclopentadienyl or substituted cyclopentadienyl groups remaining attached to the cellulose react with other such cyclopentadienyl groups also remaining attached to the cellulose to produce dicyclopentadienyl or substituted dicyclopentadienyl groups which are difunctionally attached to the cellulose and constitute covalent crosslinks in the cellulose structure. The cellulose derivatives are stable to extended storage under ordinary conditions to temperature, humidity, light, etc. without loss of ability to complete the dissociation and crosslinking steps of the reaction sequence. This sequence of reactions therefore constitutes a delayedcure process for cellulosic textiles. In this process the textile is reacted with reagents which attach monofunctional substituents containing the dicyclopentadiene carbon skeleton to the cellulosic chain. The reacted textile is then manufactured into garments or other products and the garments or other products are constrained in the creased, pleated, or other desired configurations, and then heated. The heating causes the dicyclopentadienyl groups to dissociate and the cyclopentadienyl groups remaining on the cellulose combine with each other to produce dicyclopentadienyl groups which are difunctionally attached to the cellulose and constitute covalent crosslinkages. The creases or other configucyanoethylated cellulose and the like, and partial esters of cel- 1 lulose such as partially acetylated cellulose and the like. In general, the cellulosic textile fibers, in the form of free fibers, slivers, yarns, threads, or fabrics, including natural fibers and partial ethers or partial esters thereof which are produced by reactions in which the fibers retain their cellulosic textile properties, are preferred starting materials. The cellulosic textile fibers in the form of spun textiles, i.e., yarns, threads or cloths are particularly suitable starting materials.

The monofunctional reagent may be any compound containing the dicyclopentadienyl (tricyclo[5,2,l,0 ]deca- 3,8- dienyl) carbon skeleton and having one functional group capable of reacting with cellulosic hydroxyl groups and having the formula.....

CH R CH l cHCH ll z I OH E H wherein R is a functional group capable of reacting with cellulosic hydroxyl groups. The group R is substituted for any one of the hydrogen atoms in the formula above. NOMENCLATURE: For the nomenclature applicable to the compounds of this invention refer to Definitive Rules for Nomenclature of Organic Chemistry in the Journal of American Chemical Society, 82, 5545 (1960).

The functional group may be any group capable of reacting with cellulosic hydroxyl groups and forming a covalent bond with the cellulose molecule. Examples of such groups include the carboxylic acid group and its derivatives such as the ester group, the acyl halide group, and the carboxylic anhydride group; reactive methylol groups such as the N- methylol amide group and the N-methylol carbamate group; groups containing reactive double bonds, such as the vinyl ketone group and the vinyl sulfonyl groups; epoxy groups such as the glycidyl group and the epoxyethyl group; alkyl halide groups such as the chloromethyl and the like organic halides; and other groups capable of reacting with cellulose to form ether, ester, or other covalent bonds with the cellulose molecule. The dicyclopentadienyl carbon skeleton may also be substituted with one or more nonreactive groups, such as methyl or other alkyl or aryl groups.

The monofunctional group attached to the cellulose must be capable of thermal dissociation to leave a reactive cyclopentadienyl or substituted cyclopentadienyl group attached to the cellulose. This cy clopentadienyl group must be capable of reacting with other such groups also attached to cellulose, and formed by the same dissociation reaction. The molecule which separates from the monofunctional substituent upon thermal dissociation must be readily removable by volatilization or other such means. An example of such dissociation and crosslinking reactions is given in the following equation:

Our preferred monofunctional reagents are dicylopentadienemonocarboxylic acids and their derivatives. These reagents may be any of the isomeric dicyclopentadienemonocarboxylic acids having the carboxyl group attached to any one of the carbon atoms of the dicyclopentadienyl carbon skeleton. An example of such a carboxylic acid is 4-carboxytricyclo[5,2,l,0 -]deca- 3,8-diene, the formula of which is given below:

/CH OH I \CH-CH 0 CO OH 51/ Nonfunctional derivatives of these acids having methyl, alkyl, aryl, or other nonreactive groups substituted for one or more of the hydrogen atoms bonded to the dicyclopentadienyl carbon skeleton are also suitable monofunctional reagents for this invention.

These carboxylic acids may be reacted with cellulose as the free acids, or they may be converted to suitable functional derivatives, such as acyl halides or mixed anhydrides before they are reacted with cellulose. Any of the reactions usually employed in the preparation of cellulose esters may be used to react these acids with cellulose. Examples of such reactions include the reaction of carboxylic acids with cellulose in the presence of an impeller such as trifluoroacetic anhydride, trichloroacetic anhydride, dichloroacetic anhydride, or chloroacetic anhydride; the reaction of an acyl halide with cellulose in the presence of a solvent and acid acceptor such as pyridine and/or dimethylformamide; the reaction of a solution of an acyl halide in an inert solvent such as carbon tetrachloride with the sodium or other metal salt of cellulose; and other like esterification methods. Substantially any apparatus usually employed in the esterification of cellulose can be used.

The esterification may be allowed to proceed to any convenient degree of substitution of ester groups on the cellulose anhydroglucose units which gives desirable textile properties to the cellulosic fabric. in general, degrees of substitution from 0.01 to 0.70 are satisfactory for the esterification of this invention. The concentration of the carboxylic acid or acyl halide in the esterification solution may be any convenient value, but concentrations between 0.05 molar and 0.50 molar are preferred for acceptable time of reaction and extent of reaction. The ratio of moles of carboxylic acid or acyl chloride per mole of anhydroglucose units during the esterification may vary from 0.05 to 3.0, but the preferred ratio is 0.20 to 0.80 mole of carboxylic acid or acyl chloride per mole of anhydroglucose unit. The reaction may be allowed to proceed for any convenient time, and the temperature may vary from room temperature to the reflux temperature of this solvent. in general, it is preferred to allow the reaction to proceed for 12 to 72 hours and to carry out the reaction at room temperature (20%0 30C.).

The preferred reaction for esterification of cellulose with the dicyclopentadienemonocarboxylic acids of this invention is the reaction of the free carboxylic acid with cellulose in the presence of an impeller such as trifluoroacetic anhydride. The reaction may be carried out in any inert, nonaqueous, nonhydroxylic solvent which does not react with trifluoroacetic anhydride, but which does dissolve the mixed anhydride between the carboxylic acid and trifluoroacetic acid and which allows intimate contact of the esterification solution with cellulose fibers. Suitable solvents include benzene, toluene, and similar aromatic solvents; hydrocarbon solvents such as hexane and heptane; chlorinated solvents such as carbon tetrachloride and chloroform; and the like solvents. If the solvent does not dissolve the carboxylic acid, the carboxylic acid and the trifluoroacetic anhydride impeller should be mixed with the solvent and the mixture should be agitated until the carboxylic acid has been converted to the mixed anhydride and gone into solution. it is preferred to employ at least one mole of trifluoroacetic anhydride for each mole of carboxylic acid. An excess of trifluoroacetic anhydride is particularly preferred. It is inefficient and uneconomical to use a large excess of trifluoroacetic anhydride. The cellulosic material used in this process must be free of water, and best results are obtained if the cellulosic textile is in the swollen condition. Our preferred method is to swell the cellulosic textile in warm or hot water, then to remove the water by several solvent exchanges with anhydrous methanol, followed by several solvent exchanges with anhydrous benzene or other anhydrous solvent used in the esterification.

The preferred esterification reaction is conducted in such a manner that the solvent of the esterifying agent has free access to all parts of the fabric. Our preferred method of conducting the reaction is to roll the swelled and solvent exchanged fabric with loosely woven glass cloth and place it in the previously prepared solution of the dicyclopentadienemonocarboxylic acid and trifluoroacetic anhydride. The container is tightly closed and the reaction is allowed to proceed with occasional agitation for the desired time.

After the desired time of reaction, the esterification solution is removed from the fabric and the fabric is thoroughly washed with the same solvent as employed for the reaction, with warm water, and with boiling methanol. The thorough washing is necessary to remove traces of trifluoroacetic acid which would otherwise remain on the cellulosic fabric and cause slow degradation of the cellulose.

The treated fabric may then be manufactured into garments or stored for any desired period of time up to at least 2 years. During the storage or handling of the fabric, it is not necessary to use any special conditions beyond those normally used in storing or handling untreated cotton fabrics.

The crosslinking is achieved, and durable creases, pleats, or other deformations are set in the fabric prepared according to this invention by heating the fabric while it is constrained in the desired configuration. The fabric may be heated at temperatures varying from 100 to 200C. The fabric may be heated for periods of from 2 minutes to hours, depending on the temperature used. The preferred temperature is l40to 160C, and the preferred times are 30 minutes to 4 hours. Lower temperatures and shorter times may not allow complete cross-linking, while higher temperatures and longer times may cause excessive weakness or brittleness in the fabric.

The fabric may be heated by any convenient method which allows the fabric to be constrained in the desired configuration during the heating period, and allows the cyclopentadiene or cyclopentadiene derivative to be removed from the fabric as it is evolved. Examples of such methods include immersing the fabric in a solvent held at the desired temperature and heating the fabric in an oven in air or in vacuum. The fabric may be constrained in the desired configuration by any convenient method which allows the fabric to be heated at the desired temperature for the desired time. An example of such a method is to press the fabric between glass or metal plates which are held together by spring clamps. High temperature pressing machines may also be suitable for this heating and cross linking process.

Yarns of cellulosic fibers, treated according to this invention, may be cross-linked and durably coiled or otherwise deformed by heating them while they are in the coiled or other desired configuration. For example, yarns may be crosslinked and durably coiled by esterifying them according to this invention, wrapping them around a rigid rod, and heating them. The temperatures and times of heating are the same as those described for fabrics.

The durability of fabric deformations produced by this invention is established by a creaseretention test. Samples of fabric l.5 by 2.0 cm. are out such that a 1.0 by 1.5 cm. area of fabric is on each side of the crease to be tested. The fabric sample is washed in running water at 60C. for 2 hours. The fabric sample is spread with the crease open and allowed to dry as flat as possible. The dried fabric sample is spread open with the inside of the crease on a slat smooth surface and covered with a 500 g. weight for 60 seconds to press it flat under standard conditions. The fabric sample is turned over and one side of the sample is placed on a flat, horizontal surface with a 5 g. weight arranged to keep that side of the fabric sample flat and horizontal, while the other side of the sample extends upward. After the fabric sample has been allowed to relax for 60 seconds, the angle between the two sides of the sample is measured and reported as the creaseretention angle (CRA). An uncreased fabric sample thus has a CRA of 180 and a creased sample has a lower CRA. In general, a CRA of to in 3.5 oz. per sq. yd. printcloth indicates a sharp crease. The durability of the crease is further tested by ironing the creased fabric sample flat for 30 seconds with the iron on the cotton setting. The CRA is again measured as before.

The formation of crosslinks in the fabric during heating is established by the increase of .wrinklerecovery angle as the fabric is heated.

The following list of examples is presented to illustrate the invention and is not meant to limit its scope in any manner whatever.

EXAMPLE 1 A sample (8.5 inches by 11 inches, 6.7 g.) of 80 80 cotton printcloth (desized, scoured, and bleached) was swelled by heating it in boiling water for 1 hour. The water was removed and the cloth was soaked three times (15 minutes each) in fresh portions of anhydrous methanol and four times (15 minutes each) in anhydrous benzene. The cloth sample was then laid on a piece of loosely woven glass cloth of the same size and the two were rolled into a cylinder. The rolled cloth sample was immersed in a previously prepared solution of 3.65 g. (0.02 mole) of dicyclopentadienemonocarboxylic acid (4-carboxytricyclodq5,2,l,0 deca- 3,8- diene) and 6.0 ml. (8.40 g., 0.04 mole) of trifluoroacetic anhydride in 50 ml. of benzene, which was contained in a cylindrical tube fitted with a ground glass stopper. The tube was securely closed, shaken for 10 minutes, and allowed to stand with occasional agitation. After 24 hours of standing, an additional 1.0 ml. of trifluoroacetic anhydride was added to replace the small amount which had seeped out around the stopper. After the esterification had been allowed to proceed for a total of 72 hours, the solution was removed and the cloth sample was thoroughly washed in several portions each of benzene, acetone, methanol, and finally for 2 hours in hot water. The fabric was ironed dry. The addon of dicyclopentadienemonocarboxylic acid (on a dry basis) was 36 percent. A modified Eberstadt titration showed that the cellulose had a degree of substitution of 0.42 ester groups per anhydroglucose unit. The fabric had wrinklerecovery angles of 94 (warp only, conditioned) and 82 (warp only, wet).

EXAMPLE 2 A piece of cotton fabric prepared according to example l was held flat between glass plates and heated in an oven at C. for minutes. After the heating, the fabric had a wrinkle recovery angle of 124 (warp only, conditioned), compared with a wrinklerecovery angle of 92 before heating.

The fabric was further heated at 150C. for an additional 150 minutes. After the second heating, the fabric had a wrinklerecovery angle of 120 (warp only, conditioned) and was very tender for excessive heating.

EXAMPLE 3 Samples of cotton fabric prepared according to example I were folded such that the warp yarns were creased. The folded fabric samples were placed between glass plates held together by spring clamps in order to constrain the fabric in the folded configuration. These assemblies were heated in an oven at l50to 155 C. for periods of 45 to 170 minutes, as shown in table 1. After the heating periods, the fabric samples were removed from the glass plates and washed with agitation for 2 hours in water at 60C., then spread open and allowed to dry. The crease retention angles were measured and the fabric samples were ironed as flat as possible. The crease retention angles were then again measured. Table I shows the times of heating, the crease retention angles before ironing, and the crease retention angles after ironing.

Table I Sample Time of Crease Retention Angle No. Heating Before Ironing After lroning l 45 min. 87"-94 l08"l20 2 90 min. 85"-88 l03-l16 3 170 min. 7985 l09"-l 14 Samples of untreated cotton printcloth subjected to this creasing process showed crease retention angles of 166-l70 before ironing and 180 after ironing.

Samples of cotton printcloth treated according to example 1 except that adipic acid was substituted for dicyclopentadienecarboxylic acid and subjected to the creasing process of this example showed crease retention angles of l68l69 before ironing and 180 after ironing.

EXAMPLE 4 EXAMPLE 5 tr m (9-3 -Qmt l n th) ,remav di pn jlx. 8.Q cotton printcloth treated according to example 1 was tightly wound on a 2.4 mm. diameter steel rod and heated in an oven at 150 C. for 4 hours. The yarn was then removed from the rod,

soaked in distilled water for 5 hours, and allowed to dry overnight while suspended from one end and stretched by a 3.0 g. weight attached to the other end. The length of the stretched, uncoiled yarn was measured and the weight was removed. After the yarn had relaxed for 4 hours while suspended from one end, the length of the coiled yarn was measured. The stretched, uncoiled length was found to be 350percent of the relaxed, coiled length. The recoverable extension was thus 72.5 percent of the extended length.

The yarn was subjected to repeated cycles of stretching and relaxation in groups of first 50 cycles while the yarn was dry, then 50 cycles while the yarn was immersed in water, then 50 cycles dry, etc. After 200 cycles of stretching and relaxation, the stretched length which had not changed, was found to be 136 of the relaxed, coiled length. The recoverable extension after 200 cycles was thus 27 percent of the extended length.

A yarn from unesterified cotton printcloth was coiled and heated in the same manner. The original recoverable extension of the yarn was 9 percent of the extended length, and after 50 cycles of stretching and relaxation, the recoverable extension was 2 percent of the stretched length.

A yarn from adipate cross-linked cotton printcloth was coiled and heated in the same manner. The original recoverable extension of this was 14 percent of the extended length, and after 50 cycles of stretching and relaxation, the recoverable extension was 4 percent of the extended length.

We claim:

l. Cellulose dicyclopentadienemonocarboxylate.

2. A process of imparting delayedcure characteristics to a cellulosic textile material comprising:

a. reacting said material with a dicyclopentadienemonocarboxylic acid in the presence of trifluoroacetic anhydride in an inert organic solvent, in a corresponding molar ratio of about 2: 1:2, for 72 hours, at room temperatures,

. washing the modified material thus obtained with organic solvents and water and drying the washed material. A delayedcure textile modification comprising:

reacting a cellulosic textile material with dicyclopentadienemonocarboxylic acid to obtain cellulose dicyclopentadienemonocarboxylate having a degree of substitution of about from 0.01 to 0.5, washing the modified material with organic solvents and water, c. drying the washed material,

. storing the dried material for a period up to 24 months,

retrieving the material from storage and constraining it in a desired configuration, and f. heating the constrained material while held in the desired configuration for periods of time of about from 10 to 180 minutes at a temperature of about from l40to C. to

form cellulose crosslinks therein.

Non-Patent Citations
Reference
1 *Cruz Lagrange et al., American Dyestuff Reporter, pp. 428 430 (1962)
2 *Franklin et al., Journal of Organic Chemistry, Vol. 33, pp. 626 632 (1968)
3 *Hamalainen, Textile Research Journal, Vol. 27, pg. 168 (1957)
4 *Tedder, Chemical Reviews, Vol. 55, No. 5, pp. 787 794 (1955)
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US5447778 *Aug 17, 1993Sep 5, 1995Matsushita Electric Industrial Co., Ltd.Information recording medium and methods of manufacturing and using the same
US5591487 *May 30, 1995Jan 7, 1997Matsushita Electric Industrial Co., Ltd.Information recording medium and methods of manufacturing and using the same
US5716674 *Sep 18, 1996Feb 10, 1998Matsushita Electric Industrial Co., Ltd.Information recording medium and methods of manufacturing and using the same
Classifications
U.S. Classification8/120, 536/63, 38/144, 8/182, 536/85, 8/184, 8/129, 536/93, 8/187
International ClassificationD06M13/00, D06M13/12
Cooperative ClassificationD06M13/12
European ClassificationD06M13/12