Films containing liquid crystalline polymers

Description: TECHNICAL FIELD [Detailed description of the invention]

Technical field The present invention relates to a film having a required surface roughness and, if desired, a low coefficient of friction. More specifically, the present invention relates to a film in which the above results can be obtained without using a known slip agent. Background technology Films with a required surface roughness and / or low coefficient of friction have long been sought. Such films are useful in a wide range of applications such as packaging, electrical insulation, adhesive tapes, magnetic recording tapes and discs, consumer tapes and the like. A low coefficient of friction is desirable for improved handleability of the film during manufacture and use and for preventing sticking during storage. A required surface roughness is desirable to give the film a suitable surface structure. For example, a support used in a magnetic recording medium must have a relatively smooth surface to which magnetic coating is applied. On the other hand, the running, or opposite side, of the magnetic support must have the characteristic of being resistant to wear due to contact with the surface, such as a tape drive mechanism. Several methods have been used to obtain films with surface roughness and low coefficient of friction. Generally, these are so-called slip agents (eg, parent polymer (host)). Includes the use of inorganic particles and organic substances that are insoluble in polymers), coatings with a low coefficient of friction, and surface textures. Each of these methods has one or more disadvantages. For example, with inorganic slip agents (eg silica, talc, mica, glass, calcium carbonate, titanium dioxide, etc.), previously used insoluble organic slip agents (eg, crosslinked polymers, fluorocarbon polymers and fatty acid amides, polycarbonate, polyolephine, etc.) The combination of) clogs the filtration device used in the manufacture of the film. In addition to this, these slip agents are present in the film as large, unwanted aggregates, which have a negative impact on certain applications such as magnetic recording media. The use of these slip agents suffers from another disadvantage. Inorganic particles usually need to be ground to appropriate dimensions. This adds to the additional and cost of steps where it is difficult to control the formation of particles with a very wide range of dimensions (resulting in difficulty in predicting the surface roughness in the film). The use of insoluble organic substances usually requires the addition of large amounts, making film recirculation difficult. Applying a low coefficient of friction coating (eg, silicone coating) to the surface of the film also encounters various disadvantages. For example, such coatings are generally not durable, complicate the manufacturing process, and many such coatings adversely affect the adhesion of the material applied thereafter to the film. The surface texture of the film is usually carried out by an external means such as a surface etching treatment. Such a method also complicates the manufacturing process and adds cost. A film has been found that overcomes these disadvantages of prior art. The film not only has unique characteristics that meet the requirements for its surface roughness to be suitable for the end application, but also preferably has a low coefficient of friction. In addition, film production does not rapidly clog the filtration equipment used during such production, thus extending service life. These results are achieved by blending the host polymer with a thermotropic liquid crystalline polymer (hereinafter sometimes referred to as LCP). The use of LCP with other polymeric substances has been previously suggested. See, for example, USP No. 4,442,057 in which a combination of a fiber-forming polymer and a small amount of a (LCP) polymer capable of forming an anisotropic melt is melt-spun at a minimum take-up rate of 1,000 m / min. In this patent, LCP is solely intended to provide winding speed control (ie, the properties of the spun fiber are obtained at a relatively low winding speed). Other patents disclosing the use of LCP with other polymeric substances disclose the use of 25-95% by weight LCP with other polymers UKP No. 2,078,240; with one or more additional polymers. USP No. 4,408,022 disclosed to use 25-50% by weight LCP; USP No. 4,451,611; disclosed using 85-95% by weight LCP and 20-80% by weight in combination with other polymers Includes EPO Patent No. 169,947, which discloses the use of LCP. Each of these patents is directed to a polymer blend useful as an injection molding resin. Although some patents state that such blends can be used to form fibers and films, low coefficient of friction films with a required surface roughness, this type of oriented films. ) Or the formation of discontinuities in the LCP in the matrix of the parent polymer. Still other applications disclosing the use of LCPs with other polymers include anisotropic thermoplastics and oligomeric thermotropic materials (thermally remutable oligomers) (liquid crystals in melt additives). EPO patent application 0 071 968; and biaxially stretched films containing 1-60% by weight and 1-15% by weight of liquid crystal material in a matrix polymer are disclosed. There are JP61-78862 and JP61-78863 published in Japan. The above EPO gazette does not mention the discontinuity of LCP and the parent polymer. Moreover, neither of these publications describes a film having a low coefficient of friction or a required surface roughness. In addition, the films disclosed in the two Japanese publications have improved modulus, impact resistance and dimensional stability due to the formation of LCP needle-like bodies (ie, needle-like or rod-like regions) in polyester. It is stated to have such improved internal properties. The LCP range is 3 to 30 times the draw ratio (draft ratio, draft) at the time of film production. It has a high aspect ratio by using ratio) (ie, the degree of melt stretching). Disclosure of the present invention The present invention relates to a novel film containing a heat tautomerized liquid crystal polymer and a parent polymer. This film further includes a rough surface with a plurality of protrusions or protrusions. In a preferred sense, this film has a low coefficient of friction. These results can be achieved without conventional or known slipping agents, added surface coating or surface texture formation. As used herein, the term "coefficient of friction" includes both the coefficient of static friction and the coefficient of dynamic friction. These coefficients are measured by the method described in ASTM D-1892-78. Each coefficient identifies different properties of the film, but in the present invention each is a low value. The film preferably has a coefficient of friction of less than about 0.8, more preferably less than about 0.4. Surprisingly, the surface roughness of this film can be increased without negatively affecting its coefficient of friction. In the present invention, in an oriented single-layer film having a surface including a plurality of protrusions, the protrusions are randomly distributed on the surface and have a square average square root average peak height in the range of 1 to 80 nm. And it arises from the spherical region of the thermotropic liquid crystal polymer in the host polymer; the spherical region is stretched sufficiently small to create a spherical region of the liquid crystal polymer in the host polymer as the stretch ratio of the melt of the liquid crystal polymer to the host polymer. It is formed by adopting a ratio (except for a stretch ratio of 3 to 30 times); the liquid crystal polymer can form an optically anisotropic melt when heated to a specific temperature range. Alternatively, a shearing force can be applied to the polymer to induce the formation of such an optically anisotropic melt; the melting point of the liquid crystal polymer is lower than the decomposition temperature of the host polymer; The layer film contains 0.01 to 80% by weight of the liquid crystal polymer; the single layer film. The present invention can be the single-layer film containing 0.04 to 3% by weight of a thermotropic liquid crystal polymer. The present invention is further an oriented multilayer film, one of the surface layers of the film having an exposed surface including a plurality of protrusions, the protrusions being randomly distributed on the exposed surface 1 ~. It has a square mean square root mean peak height in the 80 nm range and arises from the spherical region of the thermotropic liquid crystal polymer in the host polymer; the spherical region is the host as the draw ratio of the melt between the liquid crystal polymer and the host polymer. Formed by adopting a draw ratio small enough to create a spherical region of the liquid crystal polymer in the polymer (except for a draw ratio of 3 to 30 times); the liquid crystal polymer was heated to a specific temperature range. When an optically anisotropic melt can be formed, or by applying a shearing force to the polymer, it can be induced to form such an optically anisotropic melt; The melting point is lower than the decomposition temperature of the host polymer; and one of the surface layers of the multilayer film contains 0.01 to 80% by weight of the liquid crystal polymer; the multilayer film. Detailed explanation The present invention relates to a film having a structure whose thickness is substantially smaller than either its length or width and which has essentially parallel facing surfaces. The term "film" as used herein includes sheets, ribbons, tapes, disks and the like. FIG. 1 is a 400 × optical micrograph of the surface of the film of the present invention. This film, containing 0.24% LCP in poly (ethylene terephthalate), was 37μ thick. As can be seen from the figure, the surface contains a large number of individual protrusions of different heights and shapes. The protrusions are randomly distributed on the surface and are caused by the presence of identifiable regions of the LCP in the film. At relatively low concentrations of LCP (eg 25% by weight or less), it can be said that the surface of the film is substantially composed of the parent polymer and the LCP region is dispersed in the parent polymer. At these concentrations, the LCP region is sometimes exposed but generally covered by a thin layer of parent polymer. At high concentrations of LCP (eg, about 25% or more), more areas are exposed to the surface. The number of exposed areas continues to increase up to about 50% by weight or more, and the LCP area constitutes the main material on the surface. At these concentrations, it can be said that the parent polymer is dispersed in the LCP region. The LCP region is a three-dimensional structure that is generally characterized as spherical. As it stands, they have a symmetric (eg spherical, oval, etc.) or asymmetric cross section. Usually, they are asymmetric and have a low aspect ratio. As a result, most of the LCP region is neither needle-shaped nor rod-shaped. The LCP region is typically easily discernible under a light microscope using orthogonal polarizers. They are usually 0.2-20 μm in diameter or spindle and give rise to protrusions of at least 1 nm (preferably at least 5 nm) from the surface (discussed in detail below). Useful films are obtained in both smaller and larger regions, but the effectiveness of LCP is diminished when the regions are outside this range. The amount of LCP used in the present invention can vary over a fairly wide range. For example, a small LCP such as 0.01% by weight can also be used. Surprisingly, changing the amount of LCP used changes the surface roughness of the film. For example, LCP preferably constitutes 0.04-80% by weight of the film weight. More preferably, when a relatively smooth film is desired, the LCP comprises 0.04 to 3% by weight (most preferably 0.04 to 1% by weight). If a film with a relatively rough surface is desired, the LCP typically comprises 1% by weight or more of the film. The surface roughness values reported herein are referred to as the root mean square average peak height (RQ). The method of measuring the RQ value will be described later. A relatively high RQ value indicates a relatively rough surface. Due to the ability of the film of the present invention to have the desired roughness, the same components can be used to design special films for specific applications. For example, magnetic recording media such as videotapes, audio tapes, floppy desks, and computer tapes require a smooth surface for the application of magnetic recording materials. These devices can be manufactured by applying either a layer of a magnetic recording medium or a layer of free metal in a binder to a film of the present invention containing 0.04 to 0.5% by weight of LCP. By this method, a film having a maximum surface roughness of about 60 nm can be obtained. A relatively smooth surface (surface roughness less than 25 nm) is obtained by using 0.04 to 0.2 wt% LCP. As mentioned above, this film preferably has a low coefficient of friction. Surprisingly, a low coefficient of friction is obtained in very low amounts (eg 0.04% by weight). Even more surprisingly, the amount of LCP used can be varied as described above without significantly affecting the coefficient of friction. For example, at an LCP concentration of 0.04 to 3% by weight, the coefficient of friction is less than 0.8 (preferably 0.2 to 0.5). The coefficient of friction remains within this range even at amounts higher than 3% by weight. The exact nature of the relationship between the LCP and the parent polymer in the present invention is not fully understood. The LCP can also interact with the parent polymer by physically entwining with the parent polymer, or by partially reacting with the parent polymer in the form of a transesterified blend with the parent polymer. possible. However, the film obtained if the LCP completely reacted with the parent polymer was found to lose its ability to impart a reduced coefficient of friction and controlled surface roughness, so it reacted in any partial manner. It is important that the LCP and parent polymer regions remain discernible in the product as well. The thermally reciprocally modified liquid crystal polymers useful in the present invention can form optically anisotropic melts when heated to a specific temperature range, or by applying shear forces to the polymers. Either can be induced to form a good melt. In general, any heat tautomerized liquid crystal polymer can be used in the present invention. It has been found that LCPs with melting points below, equal to or higher than the melting point of the parent polymer can be successfully used in the present invention. However, it has also been found that in the case of LCPs with a melting point lower than that of the parent polymer, a relatively high concentration of LCPs is required to obtain consistent results. The melting point of LCP must be lower than the decomposition temperature of the parent polymer. The chemical structure of the LCP has been found to have some effect on the coefficient of friction and surface roughness of the film. In general, if the LCP has the same chemical moiety as the chemical moiety of the parent polymer, or if the LCP is thermodynamically mixed with the parent polymer, the coefficient of friction is relatively high and the surface roughness is high. Will be relatively low. Preferably the LCP is entirely aromatic polyester or polyester amide. Such materials include two or more repeating moieties that form an optically anisotropic fused phase when combined. Fully aromatic polyesters have at least one aromatic ring for each moiety present in the polyester to the polymer backbone, and each moiety has little or no non-aromatic components in the backbone. It is a substance that does not contain. It is preferred that the total aromatic polyester is substantially free of non-aromatic components in the main chain. LCPs can contain non-aromatic components in the backbone chain, but such components have been found to reduce the effects of LCPs. Such polyesters are known. For example, 4-hydroxybenzoic acid copolymers and 6-hydroxy-2-naphthoic acid copolymers can be used as LCPs. All aromatic polyesters are described in numerous print publications. For example, USP Nos. 4,067,852; 4,083,829; 4,130,545; 4,161,470; 4,184,996; 4,219,461; 4,224,433; 4,130,817; 4,238,598; 4,238,599; 4,245,084; 4,256,624; See 4,265,802 and 4,279,803. Generally, the above LCP is formed by various ester forming methods in which an organic monomer compound having a functional moiety is reacted. For example, the functional group of the organic monomer may be a carboxylic acid group, a hydroxyl group, an ester group, an acyloxy group, an acid halide or the like. The monomer can be reacted by the molten acidrins method. Typically, the monomer is heated to form a melt that produces volatiles. A vacuum is usually applied at a later stage to facilitate the removal of volatiles formed during the condensation. Examples of LCP substances useful in the present invention are "Vectra" A900 (believed to be a copolymer of 4-hydroxybenzoic acid and 6-hydroxynaphthoic acid) available from Hoechst Celanese: LCC10108 (60 mol%). Includes oxybenzoate and 40 mol% ethylene terephthalate copolyester) and LCC10109 (80 mol% oxybenzoate and 20 mol% ethylene terephthalate copolyester), the latter two from Eastman Kodak's Eastman Chemical Available from Division. Other LCP materials useful in the present invention include "Xydar" LCP (p-oxybenzoate, p, p'-biphenyl and terephthalate copolyesters) and p-oxybenzoate and hydroquinone and aliphatic didi, available from Dartco. Includes copolyesters as disclosed in USP 4,377,681, including copolyesters with either carboxylate or 2,2-bis (4-hydroxyphenyl) propane and isophthalates. The parent polymer useful in the present invention is a material that can be extruded or cast, coagulated and dried to form a preferably self-supporting film. These include, for example, polyesters (including aromatic polyesters), polyamides, polyimides, polycarbonates, polyolephine, acrylic polymers, vinyl chlorides and vinylidene chlorides, fluoride-based polymers, polystyrenes, polyphenylene oxide polymers, polysulfones and polyethersulfones, polyketones. In addition, it can be selected from various substances including polyether ketone, polyoxymethylene, thermoplastic cellulose-based polymer and the like. These materials can be used alone, as a mixture of two or more polymers, and as a copolymer. A particularly useful class of parent polymers are polyalkylene terephthalates and their copolyesters. These polymers, many of which are commercially available, are either alcoholicized with alkylene glycols of terephthalic acid esters and subsequently polymerized, or heated with glycols and free acids or halide derivatives thereof, followed by polymerization and similar methods. It can be produced by a known method such as. The alkylene unit of polyalkylene terephthalate generally contains 2 to 10 (preferably 2 to 4) carbon atoms. Most preferably, they contain two carbon atoms. Specific examples of useful polyalkylene terephthalates include poly (ethylene terephthalate), poly (butylene terephthalate), poly (isobutylene terephthalate), poly (pentyl terephthalate), poly (isopentyl terephthalate), and poly (neopentyl terephthalate). Is included. The alkylene unit may be a straight chain unit or a branched chain unit. Other specific examples of useful parent polymers include polyhexamethylene adipamide, polycarbonate, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, polyvinylidene chloride, polyvinylidene fluoride, polyvinylidene, polymethylene. Includes methacrylate and the like. Various other components can be blended in the film of the present invention. For example, conventional slipping agents can be added if desired, but these combinations are not necessary. Ultraviolet absorbers, antioxidants, colorants and the like can also be added if desired. These other ingredients are generally less than 5% by weight of the film. The film of the present invention can consist of either a single layer film of LCP and a parent polymer or a multi-layer structure in which the LCP / parent polymer combination constitutes a single layer. When the film is supplied as a multilayer structure, the LCP-containing layer generally constitutes one layer of the exposed surface of the film. The film of the present invention can be easily produced by a number of methods. For example, the individual ingredients are prepared in the form of particles or pellets, each appropriate amount is weighed and added into a mixing vessel, then the ingredients under ambient conditions to produce a substantially uniform dry blend of ingredients. To mix. The dry blend is then placed in a suitable mixing vessel, such as a single screw extruder, with a mixing element of appropriate length (eg, a mixing screw or static mixer), or with a mixing element. It is loaded into the twin screw extruder. The blend must be melted at a temperature above the melting point of the LAP and the parent polymer and mixed tightly to disperse the LCP in the parent polymer and confer a distinguishable region of the liquid crystal polymer in the parent polymer. The extruder can be equipped with a filter (eg, with a pore size of 1 to 200 μ) to help disperse the LCP and remove unwanted foreign matter and gel. After mixing as above, the dispersion blend of LCP and parent polymer is extruded from the extruder through a filter (eg 1-200 μ dimension) and a suitable die, quenched or cast on a chilled roll, and an amorphous case (eg, 1-200 μ dimension). case) Form a web. Surprisingly, the melt mixture of LCP and parent polymer does not clog the filter. As a result, the filter life is extended and the product quality is improved. The web is then stretched longitudinally at a temperature of, for example, 80 ° to 95 ° C, then laterally at 190 ° to 210 ° C, and then 200 ° to 250 ° C [poly (ethylene terephthalate)). Is oriented by heat-setting at the temperature of]. The exact temperature used depends on the main components of the film and is known to those of skill in the art. If desired, longitudinal and transverse stretching can be performed simultaneously. Typically, during orientation, it is stretched to a length of 1-5 times the original dimensions of the web. In this state, the length: width stretching ratio can be changed from 1: 1 to 1: 5 and 5: 1 to 1: 1. The oriented film can be rolled up and stored for later processing, or it can be further processed without storage in the middle. Other methods can be used to make the combination of LCP and parent polymer. For example, a master hatch of LCP at a higher concentration finally desired can be produced with the parent polymer. The master hatch is then combined with an additional parent polymer to the desired LCP concentration. Generally, the amount of LCP used in the master batch method is 3 to 15 times higher than the final desired LCP concentration. Further, in any of the above-mentioned methods, several kinds of modified manufacturing methods are possible. For example, LCP may be introduced into the polymerization mixture of the parent polymer at the beginning, middle or end of the polymerization step. The LCP is then mixed with stirring during the process and uniformly dispersed in the parent polymer. If the mixing is appropriate, it is more preferred to introduce the LCP into the polymerization mixture at the end of the polymerization step to minimize the chemical reaction between the LCP and the parent material. Whatever master-batch method is used, the molten master-batch is introduced directly into a suitable mixing vessel and combined with an additional parent polymer to form a film, or, as an alternative, coagulate it, followed by It can also be crushed or polymerized for later use. Preferably, the particles of the master butch blend have dimensions approximately equal to the particle size of the additional parent material to be mixed with it. The present invention is useful in various methods. For example, this may be a magnetic recording medium (eg, granular magnetic material in a binder and metallized magnetic tape), a polishing material (eg, a granular polishing material in a binder), reinforced polymer backing, a radiation sensitive composition (eg, diazo-based). , Photoactive polymers, etc.), useful as a support for adhesives, etc. The present invention will be further described with reference to the following examples, where all percentages in the examples are weight% unless otherwise stated. These examples are intended to further illustrate this without limiting the invention. Examples 1 ~ 11 A series of films was produced from two types of heat tautomerized liquid crystal polymers and poly (ethylene terephthalate) (hereinafter referred to as PET). LCP and poly (ethylene terephthalate) master batches were produced. The LCPs, which make up 2-5% by weight of the batch, were dry mixed with PET at ambient temperature, dried at 149 ° C and then inserted into a single screw extruder. The blend was heated to a temperature of 260 ° C to 280 ° C and extruded through a static mixer into the extruder neck and passed through a 60μ filter. The extruded product was solidified by passing it through a water bath and then pelletized. The pelletized master hatch is dried at 149 ° C, then charged into an extruder with additional PET using an Acrison feeder, mixed at a temperature of 260 ° -290 ° C, and then passed through a drop die 65. Extruded onto a chilled roll maintained at a temperature between ° C and 66 ° C. A draw ratio of 1.5 (stretchability of the melt) was used. A 30 μ filter was used to avoid foreign matter and large lumps of non-molten polymer in the film. The quenching film was then stretched 3.2 times the original dimensions in both the length and width directions and heat set at 204 ° C. The resulting biaxially stretched film was then tested for static and dynamic friction coefficients using ASTM D 1894-78. Surface roughness was measured using the method described in Journal of Institution of Electronic and Radio Engineers, Vol55, No.4, pp. 145-150, April 1985. For roughness above 200 nm, Hamilton.DK and Wilson T. 1982, "Surface Profile Measurement Using the Confocal Microscope" Applied Physics. Vol53 No.7 Roughness was measured using the method described on page 5320. In either case, the PQ is an expressionMeasured from. The composition produced and the results obtained are shown in Table 1. The surface of the film of Comparative Example 1 had some undulating ridges (rather than discontinuous peaks or protrusions) that gave the film some roughness. However, as can be seen from the table, this film had an extremely high coefficient of friction. On the contrary, the films of the present invention had a custom surface and a low coefficient of friction. In addition, the surface of these films contained discontinuous protrusions or peaks caused by the presence of discontinuous spheres of LCP in the film. The surface of this film was also essentially composed of poly (ethylene terephthalate). Example 12 A series of films were produced using the above method, except that a 5μ filter was used instead of a 30μ filter. The pressure drop through the 5μ filter was measured as a function of cumulative extrusion. This result is shown in Fig. 2. In Figure 2, curves 10 and 12 are slip-free PET. films. Curve 14 shows PET and 0.3% by weight SiO₂Shows the film; Curve 16 shows PET and 0.2% by weight CaCO₃Shows the film; Curve 18 shows PET and 0.1% by weight Vectra A900 LCP film from Celanese; Curve 20 shows PET and 0.2% by weight Vectra A900 LCP film from Celanese; and Curve 22 shows PET and 0.5% by weight LCC 10108 LCP film from Eastman. As can be seen from the figure, slip-free PET (curves 10 and 12) is well filtered. However, this film is difficult to handle due to the absence of a slip agent and sticks (sticks to itself). Films made with inorganic slip agents (curves 16 and 18) initially show good filtration suitability. However, the fact that the pressure drop passing through the filter increased dramatically with the increase in the cumulative extrusion amount is evidence that the filter was clogged. The films of the present invention (curves 18, 20 and 22) show filtration suitability comparable to slip-free PET. Moreover, the obtained film did not have any problem in handling the film containing no slip agent. Example 13 ~ 16 LCP (Vectra A900, Hoechst) at 1% by weight concentration in polycarbonate (Merlon manufactured by Mobay Chemical) A master batch was produced by dry blending (Chemical) and then extruding through a static mixer and a 40 μ filter to pelletize. After proper drying, the master butch pellet was dry blended with additional polycarbonate and fed to the extruder at 292 ° C to produce cast webs at final concentrations of 0.2, 0.3 and 0.5% LCP. This cast web was then biaxially stretched 1.75 × 1.75 times at 175 ° C to form a film. The coefficient of friction (COF) of the obtained film was as follows: Table 2 Example LCP (%) Static COF Dynamic COF Comparative example 13 0 3.3 4.0 Comparative Example 14 0.2 0.45 0.57 Comparative example 15 0.3 0.48 0.49 Comparative Example 16 0.5 0.32 0.42 All films containing LCP showed better friction coefficient and slip properties than the film of Comparative Example 13 without LCP. The surface of the film of Examples 14-16 contained a series of discontinuous protrusions created by the discontinuous spheres of LCP in the film. The surface was also made of polycarbonate. Examples 17-20 A series of films of the present invention were produced. LCP (Vectra A900, Hoechst) in PET at 1% by weight LCP concentration Celanese) master butts and LCP (LCC 10108, Eastman Kodak) master butts in PET at an LCP concentration of 5% by weight are each dry blended and then extruded and pelletized through a static mixer and 60 μfilter. Manufactured by After proper drying, the master butch pellet was dry blended with additional PET and fed to the extruder using a 5 μ filter to produce a cast web with the final concentration as shown in the table below. .. The cast web was then biaxially stretched 4 × 4 times at 99 ° C and human-set at 237 ° C to form a film. The coefficient of friction (COF) and RQ were then measured. The results are shown in Table 3 below.Example 21 ~ 24 A series of films according to the present invention was produced. Manufactured by dry blending LCP (Vectra A900, manufactured by Hoechst Celanese) master batches in PET at a concentration of 1% by weight, then extruded using a static mixer and a 60 μ filter to pelletize. After proper drying, the master butch pellet was then mixed with additional PET and fed to the extruder using a 5 μ filter to produce cast webs with final concentrations of 0.04, 0.07 and 0.09% LCP. The cast web was then biaxially stretched 4 × 4 times at 99 ° C and heat-set at 237 ° C to form a film. The coefficient of friction (COF) and RQ of the resulting film are then measured and reported in Table 4.Examples 25-28 A master batch of a mixture of LCPs (Vectra A900, Hoechst Celanese and LCC 10109, Eastman Kodak) in PET was dry blended to a concentration of 1% by weight and then extruded using a static mixer and a 60 μfilter. And it was manufactured by making it into a pellet. After proper drying, the master butch pellet was then fed by the Acrison feeder to the running PET of the extruder to a final concentration of cast web as shown in Table 5 below. The cast web was then biaxially stretched 4 × 4 times at 99 ° C and heat set at 237 ° C to produce a film. The coefficient of friction and RQ are then measured and reported in Table 5. Example 26 has a relatively high COF value. However, this film has a better COF value than the film without LCP. Compare Example 26 with Example 21. In addition, this LCP has the same chemical moiety (ethylene terephthalate) as PET. As mentioned above, this makes its COF relatively high. Examples 29 ~ 32 A series of films were produced according to the present invention. The composition of LCP (LCC 10108, 60 mol% oxybenzoate and 40 mol% ethylene terephthalate copolyester, available from Eastman Kodak) is obtained by dry mixing the desired amount of LCP and PET. Manufactured. After proper drying, the resulting dry blend was extruded onto a chilled roll through a drop die. Next, the cast web was biaxially stretched 3.5 × 3.5 times at 99 ° C. and heat-set to produce a film. The coefficient of friction of the resulting film is then measured and reported in Table 6 along with the final concentration of LCP used.Examples 33 to 41 The thin layer (about 20% of the total film thickness) for which a series of double-layer films according to the present invention was produced is composed of a combination of LCP (LCC-10108, manufactured by Eastman Kodak) and PET, and is a main layer (film thickness). About 80%) consisted of pure PET. The LCP-containing material was prepared as described in Example 29 and co-extruded with the PET layer at 260-290 ° C using a 100 μ dimensional filter. The double layer was cast on a chilled roll maintained at 91-94 ° C from the die at 260 ° C. The films of Examples 33-39 were biaxially stretched at the same time, and the films of Examples 40 and 41 were sequentially biaxially stretched. All of these were stretched 3.8 × 3.8 times at 99 ° C and heat set at 237 ° C. The resulting films measured their coefficient of friction by rubbing the LCP-containing sides against each other and by rubbing the LCP-containing sides against the PET side. The results of LCP concentration and friction coefficient are shown in Table 7. The surface of the films of Examples 38-41 contained large regions or spheres of LCP dispersed in the parent polymer. Comparative example 42 ~ 45 A series of rough surface films of the present invention were produced using the methods described in Examples 29-32, except that Vectra A900 from Hoechst Celenese was used as the LCP. Next, the friction coefficient of the obtained film was measured, and the surface roughness was measured by the method shown in Comparative Example 1. The No. 2 pencil was used to test the aptitude for writing with pencils. Written aptitude was graded comparable to regular paper or better when leaving black marks on the film than on regular paper. The results are shown in Table 8 together with the LCP concentration used.

[Simple explanation of drawings]

FIG. 1 is a replica of an optical micrograph of the surface of the film of the present invention. Figure 2 is a graph showing the pressure drop across a 5 μfilter as a function of cumulative extrusion.