KR100244693B1 - A void-containing polyester-type film - Google Patents

Abstract

The present invention consists mainly of a thermoplastic resin and a polyester base layer (A) containing fine cavities formed by orienting a mixture of at least one polyester and at least one thermoplastic resin that is non-compatible with the polyester in at least one direction. At least one outer surface layer (B) formed on at least one side of the polyester base layer (A), wherein the void ratio of the surface portion having a thickness of 3 μm from the surface of the polyester base layer (A) is 8% by volume or Less than or equal to 10 to 50% by volume of the composite film of the composite-containing polyester composite film is disclosed. In addition, it comprises at least one outer surface layer (B) formed on at least one side of the polyester base layer (A) containing the microcavity, the outer surface layer (B) is 0.1 to 2.0 ㎛ average primary particle size (R ₁) It contains 1 to 30% by weight of inorganic particles including primary particles having and secondary particles having an average secondary particle size (R₂) of 1.05 to 1.60 times R 'value, and 99% R₂ value is 4.0 times R' value. Also disclosed is a cavity-containing polyester composite film having a Rn value of 5.0 times or less of an R 'value.

Description

Co-Containing Polyester Composite Film

1 is a schematic cross-sectional view of the main part of the void-containing composite film of polyester type obtained according to the present invention in the thickness direction thereof;

2 is a graph showing the relationship between the peak number and the peak height at the surface portion of the outer surface layer (b) with respect to the co-containing polyester composite film obtained in Examples 16 to 18 of the present invention, and the equation Y =- Curves corresponding to 1.3 logX +5.2 and Y = -0.77 logX + 2.31 are also shown.

* Explanation of symbols for main parts of the drawings

a: polyester base layer 1: film base material

b: outer surface layer 2: fine particles

3: microcavity

The present invention relates to a polyester film containing a plurality of micropores, having a toughness and excellent printability sufficient for the use of labels, posters, recording paper, packaging paper and the like.

Synthetic copper, mainly composed of synthetic resin as a paper substitute, has excellent properties such as water resistance, dimensional stability against water adsorption, surface stability, glossiness and clarity of print and mechanical strength compared to natural materials. In recent years, the practical use of synthetic paper has been developed using these advantages. As the main raw material of synthetic paper, synthetic resins such as polyethylene, polypropylene and polyester are used. Among these, polyesters such as polyethylene terephthalate have excellent properties such as high heat resistance and high toughness and can be widely used.

The following processes for the production of a polyester film having a function similar to that of paper by using polyester as the main raw material; (1) treating the interior of the polyester film to contain a number of voids, i.e., preparing a polyester film containing the cavity and (2) sandblasting (2-1), chemical etching (2-2) or Treatments that roughen the manifestation of conventional flat polyester films have been proposed by techniques such as the polishing process (2-3) (i.e., laminating a matting agent together with a binder). Among these processes, process (1) can reduce the weight of the film itself. There are some advantages that can give adequate flexibility for distinct printing and transfer.

To date, melt-kneading, in an extruder, a mixture of polyester and a polymer incompatible with the polyether to form a fine cavity inside the polyester film; Extruding the melt-kneaded material into sheets in which particulates of the polymer are dispersed in the polyester film base material; A process consisting of stretching the sheet to form a fine cavity around the fine particles has been proposed (see US Pat. No. 5084334). Polymers that are incompatible with polyester and that can be used to form fine cavities (called incompatible resins) include polyolefin resins (see Japanese Patent Application Publication 134755/1974), polystyrene resins (Japanese Patent Publication 2016 / Several kinds of resins have been proposed, such as 1974 and 29550/1979) and polyacrylate resins (Japanese Patent Publication 28097/1983). Among these resins, these resins are preferred because the use of polypropylene and polystyrene resins can easily form microcavities and can be purchased at low density and low cost.

However, these conventional polyester films are (1) when the adhesive layer is provided on the surface thereof and used as a label or the like to peel off, the microcavity near the film surface acts as a crack so that the film surface portion is cut; (2) the gloss of the surface is so strong that the paper substitute is poor in appearance; (3) There is a disadvantage that the whiteness of the film is lowered by the influence of the polyester by the exposure to ultraviolet rays or by the influence of the by-product of the polyester and the concealment agent used therein. Under these circumstances, the present inventors have made a thorough study of the polyester-based co-containing film and have realized that the disadvantages of the conventional polyester film described above can be solved by adjusting the size and distribution of the microcavity. . Thus, the present invention provides a polyester-based composite film having high sharpness and high durability for printing, typing and copying, high toughness, cushioning properties and particularly high surface strength, high quality appearance and excellent UV resistance; Such composite films are suitable as substrates for labels, posters, recording paper, ordinary slips, delivery slips for use in home delivery systems, pressure-sensitive adhesives, copy papers, printing papers for printers, and the like.

The co-containing polyester-based composite film according to the present invention is characterized in that the microcavity obtained by orienting a polymer mixture of at least one polyester and at least one thermoplastic resin incompatible with the flowseter in at least one direction. It consists mainly of a polyester base layer (A) containing and at least one thermoplastic resin and consists of at least one outer surface layer (B) formed on at least one side of the polyester base layer (A), wherein the polyester base layer (A) 8% by volume of the surface portion having a thickness of 3 탆 from the surface of the C) is less than 8%, and the average void of the composite film is 10 to 50% by volume.

Another co-containing polyester composite film according to the present invention is mainly composed of a polyester base layer (A) containing microcavities and at least one thermoplastic resin and formed on at least one side of the polyester base layer (A). It consists of at least one outer surface layer (B), wherein the outer surface layer (B) contains 1 to 30% by weight of inorganic particles consisting of secondary particles having an average primary particle size (R₁) of 0.1 to 2.0㎛ ; In the normal distribution for the presence of secondary particles smaller than the individual particle size, the individual particle size of the secondary particles with a 99% probability is not more than 4.0 times the R₁ value; The average value of the shortest center-to-center distances of the inorganic particles is 5.0 times or less of the R 'value.

DETAILED DESCRIPTION OF THE INVENTION The present invention will be better understood by those skilled in the art with reference to the accompanying drawings, and various objects and advantages of the present invention will become apparent. Figure 1 discloses a co-containing polyester composite film according to the present invention. Co-containing composite films have been disclosed in polyester based composite films. The co-containing composite film consists of a polyester base layer (A) and an outer surface layer (B) formed on both sides thereof. The outer surface layer (B) may be formed only on one side of the polyester base layer (A). As shown in FIG. 1, the polyester base layer (A) comprises a film base material (1) mainly composed of polyester, dispersed fine particles (2) and fine particles (2) composed mainly of thermoplastic resins incompatible with polyester. ) Has a microcavity (3) formed around. The polyester base layer (A) can be formed by orienting a polymer mixture of at least one polyester and at least one thermoplastic resin incompatible with the polyester in at least one direction. The outer surface layer (B) is mainly composed of at least one thermoplastic resin.

Polyesters which can be used in the present invention include aromatic dicarboxylic acids or esters thereof such as terephthalic acid, isophthalic acid or naphthalene dicarboxylic acid, and glycols such as ethylene glycol, diethylene glycol, 1,4-butanediol or neopentylglycol; It is polyester obtained by polycondensation of. Polyesters may be prepared by direct reaction of aromatic dicarboxylic acids with glycols or by polycondensation after transesterification of alkyl esters of glycols with aromatic dicarboxylic acids or by polycondensation of diglycol esters of aromatic dicarboxylic acids. Can be. Typical examples of polyesters are polyethylene terephthalate, polybutylene terephthalate and polyethylene-2, 6-naphthalate.

The raw material polyester may be a homopolymer, a copolymer containing other components, ie a copolyester or a mixture of homopolymers and copolymers.

When the polyester film is given high toughness and high tensile strength, the polyester used as raw material is 70 mol% or more of ethylene terephthalate unit, butylene terephthalate unit or ethylene-2, 6-phthalate unit, It is preferable to contain 80 mol% or more, more preferably 90 mol% or more. If high flexibility or easy adhesion is given to the polyester film, the copolyester is preferably used alone or in combination with a homopolymer. In any case, the type of raw material polyester may be selected depending on the application of the resultant composite film.

Thermoplastic resins that can be used in the present invention are incompatible with the polyester. Representative examples of the thermoplastic resin include polystyrene resins, polyolefin resins, polyacrylic resins, polycarbonate resins, polysulfone resins, cellulose resins, polysiloxane resins, and silicone resins. Particularly preferred are polyolefin resins and polystyrene resins such as polymethylpentene and polypropylene.

Polymer mixtures of polyester and incompatible thermoplastic resins include the steps of mixing these resin chips such that the resin mixture is melt-kneaded in an extruder and then extruded and solidified; The two resins are kneaded in the kneader, and then the mixture kneaded through the extruder is melt-extruded and then solidified; Or a thermoplastic resin which is not compatible with polyester can be prepared by a process of forming a chip which is added to the polyester in the polymerization step of the polyester and is stirred therein and then melt-extruded to solidify. After solidification, the product polymer sheet (ie, the non-stretched sheet) is usually not oriented or left slightly oriented. Thermoplastic resins incompatible with polyester are inherent in various forms dispersed on a polyester film substrate, such as spherical, elliptical, and threaded.

In particular, the polyester base layer (A) has a few voids in its surface portion but actually obtains a cavity-containing polyester composite film having no cavity at the interface between the polyester base layer (A) and the outer surface layer (B). For this reason, since the dispersed state of the non-compatible resin particles has a constant distribution in the thickness direction of the film, it is preferable that the particle size of the non-compatible resin particles is smaller at the surface portion than at the center portion of the polyester base layer (A). It is also preferable that the non-compatible resin particles have a long shape (ie, a flat shape) in the machine direction of the film at the interface between the layers (A) and (B). In this case, the stretching of the non-compatible resin particles should only occur in close proximity to the interface between layers (A) and (B). If the non-compatible resin particles are not elongated at the interface between layers (A) and (B), small cavities are formed at the interface even though the non-compatible resin particles have small particle sizes. The cavity causes surface peeling.

The conditions for melt extrusion of the resin for the polyester base layer (A) must be appropriately selected in order to obtain a non-stretched sheet containing non-compatible resin particles dispersed therein as described above.

For example, the increase in shear stresses acting on the tube wall of the melt line extending from the slits of the extruder die or from the extruder to the extruder die in comparison with the conventional case is small in flat shape only at the surface portion of the polyester base layer (A). Dispersion of non-compatible resin particles having a particle size can be obtained. In addition to these states, a reduction in the melt viscosity difference between the polyester and the non-compatible resin is adjacent to the interface between the layers (A) and (B) compared to the difference in the central portion of the polyester base layer (A). The increased flatness can be obtained so that the shape of the non-compatible resin particles becomes more flat near the interface.

In general, polyolefm resins and polystyrene resins have a low dependence of viscosity on temperature when compared to polyester resins. When this phenomenon is used to adjust the resin temperature to be lower near the interface between layers (A) and (B) than at the central portion of the polyester base layer (A), the adjustment of the difference in relative viscosity is described above. As can be achieved.

In order to control the distribution of the resin temperature in the manner described above, for example, while temperature is passed through an extruder die or melt line extending from the extruder to the extruder die, the control over temperature drop can be applied during the process, while the temperature increase Control in accordance with the usual applies to conventional melt extrusion.

Independent control of the resin temperature in layers (A) and (B) in the process where the composite film is obtained by co-extrusion may be an effective means to obtain flat particles of non-compatible resin. In particular, the outer surface layer (B) preferably has a lower temperature than that of the polyester base layer (A) and more preferably has a temperature difference between them in the range of 5 to 15 ° C.

The polymer mixture as described above may contain inorganic particles in order to improve concealability and drawability as necessary. Examples of the inorganic particles include, but are not limited to, titanium dioxide, silicon dioxide, calcium carbonate, barium sulfate, aluminum oxide, kaolin, zeolite, talc, and the like. Instead of the inorganic particles, suitable organic particles may also be used. The inorganic particles may be contained in either or both of layers (A) and (B). The amount of inorganic particles in the polyester base layer (A) is preferably in the range of 1 to 20% by weight, and the amount of inorganic particles in the outer surface layer (B) is preferably in the range of 0.5 to 30% by weight. When the inorganic particles are contained in both the layers (A) and (B), the average particle size of the inorganic particles in the outer surface layer (B) is larger than the average particle size of the inorganic particles in the polyester base layer (A). It is possible to obtain a cavity-containing polyester composite film having concealability and drawing properties, and having a poor gloss and a matt appearance. In this case, when the inorganic particles having an average particle size of 0.3 μm or more are used only in the outer surface layer B, the content of the inorganic particles can be reduced, thereby improving the stretchability. Therefore, the stretching state can be selected and the cavity formation can be easily achieved.

It is preferable that at least one kind of particles having an irregular spherical or cubic shape or an intermediate shape thereof are contained in the cavity-containing polyester composite film outer surface layer (B) of the present invention. With the addition of particles having such a shape, the polyester composite film has excellent surface quenching and excellent surface strength against peeling while maintaining the flexibility of the composite film. When irregular particles are used because there are no notches on the surface, the surface strength of the composite film against peeling is poor even though the particles have spherical or cubic or intermediate forms thereof. On the other hand, when particles having no spherical or cubic shape or intermediate forms thereof are used, the surface of the particles is notched and an excellent quenched appearance cannot be obtained even if irregular. In any case, when particles of a shape that do not meet the above requirements are used, the thickness of the outer surface layer (B) must be increased to obtain sufficient matt appearance and surface strength for peeling, thereby decreasing the flexibility of the composite film.

The thickness of the layers (A) and (B) is not particularly limited and may be any value. In order to impart proper flexibility to the composite film, it is preferable that the outer surface layer (B) formed on at least one side of the polyester base layer (A) has a thickness of 1/5 times or less than the total thickness of the composite film. In order to impart sufficient surface strength to the peeling on the composite film, the outer surface layer (B) preferably has a thickness of 0.5 µm or more.

In the composite film of the present invention, the outer surface layer (B) is thinner due to the action of particles having a spherical or cubic shape of irregular surface or an intermediate shape thereof being notched by the surface applied to the outer surface layer (B). Even thick, sufficient surface strength for peeling can be obtained. Therefore, the thickness of the outer surface layer (B) is preferably 10 µm or less and more preferably 6 µm or less.

There are irregular surfaces notched on the surface and particles having an average particle size of 0.3 µm or more are contained in the outer surface layer (B) in a proportion of 1% by weight or more in total. If the average particle size is 0.3 탆 or less, sufficient quenched external light cannot be obtained. Although the average particle size does not have an upper limit in particular, 6 micrometers or less are preferable because larger average particle size gives surface roughness to a composite film easily. Furthermore, when the total amount of particles added to the outer surface layer B having the above-described shape is 1% by weight or less based on the weight of the outer surface layer B, a sufficiently quenched appearance cannot be obtained. The amount of the particles added to the outer surface layer (B) is not particularly limited and is preferably 50% by weight, particularly 30% by weight, in order not to reduce the surface strength and flexibility of the composite film.

The particles added to the outer surface layer (B) having notches on the surface and having an irregular surface, or having an intermediate shape thereof, are not particularly limited to any composition. Examples of materials constituting these particles include, but are not limited to, silica, kaolinite, talc, calcium carbonate, zeolite, alumina, barium sulfate, carbon black, zinc oxide, titanium oxide, and the like. As the particle | grains of the above-mentioned shape, a synthetic aggregate is preferable, a secondary aggregate of a silica microbead, a secondary aggregate of a calcium carbonate fine particle, and a secondary aggregate of a titanium oxide fine particle are preferable, among which a synthetic zeolite particle is more preferable.

Synthetic zeolite particles can be either heat-treated or non-heat treated articles, but preference is given to using synthetic zeolite particles once heat treated at temperatures above 200 ° C. Among them, sintered is most preferred. In the case of secondary agglomerates of silica microbeads, it is preferable to use secondary agglomerates obtained by agglomerating silica microbeads having a primary particle size of 10 to 50 nm in a spherical form and then sintering the spherical agglomerates under appropriate conditions.

These particles may be used after at least one additional component such as a colorant, a photo-inhibitor, a phosphor, an antistatic agent and any component having good or poor affinity for the matrix resin and the like is adsorbed thereon. If necessary, additional particles other than the particles having the above-described shape may be applied to the outer surface layer (B) in order to improve the smoothness and the drawability.

Peak height (μm) based on the peak height giving the maximum number of peaks in the surface portion of the outer surface layer B with respect to the surface of the outer surface layer B and the number of peaks X in this portion (mm) ²), the relationship should satisfy the following inequality:

-1.3 log X + 5.2 ≥ Y ≥ -0.77 log X +2.31 (1)

(Where X ≥ 50 and Y ≥ 0)

This relationship can provide a polyester-based composite film having excellent quenched surface extraneous light and surface strength against peeling while maintaining the flexibility of the composite film. If the peak height (Y) is greater than -1.3 log X + 5.2, the surface strength for peeling is poor. If the peak height (Y) is -0.77 log X +2.31 or less, a good matt appearance cannot be obtained or the surface is rough. In any case, if the peak height (Y) is out of the range given by the inequality (1), the thickness of the outer surface layer (B) must be increased to obtain a sufficiently quenched appearance and surface strength for peeling, thereby reducing the flexibility of the composite film. .

In addition, the present invention is composed of a polyester base layer (A) containing a fine cavity and at least one surface layer (B) mainly formed of at least one thermoplastic resin and formed on at least one side of the polyester base layer (A), Inorganic particles 1 to 1, wherein the outer surface layer (B) consists of primary particles having an average primary particle size (R₁) of 0.1 to 2.0 μm and secondary particles having an average secondary particle size (R₂) of 1.05 to 1.60 times the R₁ value. 30 weight percent; The individual particle size of the secondary particles (hereinafter referred to as 99% R2), which gives a 99% probability in the normal distribution of the presence of secondary particles smaller than the individual particle size, is 4.0 times or less of the R 'value; It provides a co-containing polyester composite film having an average value of the shortest center of gravity distance to the inorganic particles is 5.0 times or less of the R 'value. When the R 'value is 0.1 µm or less, sufficient concealability and whiteness cannot be obtained. If the R ₁ value is more than 2.0 μm, the surface strength of the composite film is reduced due to the cavity formation from the inorganic particles. Moreover, if other conditions do not meet the above requirements, i.e., if the secondary particles have an average secondary particle size (R₂) over the range, the value of 99% R₂ is at least 4.0 times the R₁ value and the value of Rn Since it is 5.0 times or more of R 'value and the dispersion state of inorganic particles is low, it becomes uneven even in a concealment effect and whiteness. It is preferable that the dispersant of hiding power (light transmittance) is 10% or less of the average value, and the composite film exhibiting such disintegrating agent in whiteness has a high commercial advantage.

As used herein, the term " average primary particle size " refers to an average value of diameters corresponding to the circles forming the inorganic particles (i.e., each having the same area as the cross-sectional area of the inorganic particle). Average value of the diameters of the circle).

As used herein, the term " average secondary particle size " means that the inorganic particles or at least two inorganic particles form aggregates when these inorganic particles are embedded in individual forms (i.e. as primary particles). Refers to an average value of diameters corresponding to a circle forming aggregates of inorganic particles.

In addition, " primary particle " in the specification refers to a particle composed of a single crystal or crystals observed as a sphere or ellipsoid by an electron microscope.

In the specification, " secondary particles " refer to pseudo-particles which are clearly observed as aggregates of respective spheres or ellipsoids with an electron microscope.

The term " shortest center distance " in the specification refers to the distance between the center of one particle and the center of the immediately neighboring particle.

The co-containing polyester composite film according to the present invention preferably has a surface roughness of 0.1 μm or less, and more preferably 0.3 μm or less. If the surface roughness is 1.0 μm or more, failure occurs in printing when the composite film is used for printing a printer or the like.

Titanium dioxide used as a masking agent or white pigment for the cavity-containing polyester composite film according to the present invention is preferably in the form of a rutile type. The particles of rutile titanium dioxide include aluminium oxide, silica, zinc, silicon-counter paper, polysiloxane-based resin, fluorocarbon-based resin, silane coupling agent or titanate coupling agent, polyol resin, polyvinylpyridine resin, and the like. More preferably those surface-treated. Of these, particles of rutile titanium dioxide surface-treated with aluminum oxide are most preferred.

Adding titanium dioxide particles can provide sufficient concealment effect and whiteness. In particular, the addition of rutile titanium dioxide particles can achieve a high degree of stability to the polyester and the formation of by-products, because rutile titanium dioxide has excellent hiding power and low activity compared to the anetase-type titanium dioxide It is preferable because it can suppress.

Surface treatment of the rutile titanium dioxide particles with aluminum oxide enlarges the surface area of the particles by this treatment; It is inappropriate for the interface between the polyester base layer (A) and the outer surface layer (B), but it suppresses the formation of the cavity and the aluminum oxide adheres well to any polyester. Utilizing the fact that they do not separate improves the surface strength of the composite film against peeling; By coating the surface of the active titanium dioxide with aluminum oxide so that the titanium dioxide particles can be embedded in polyester in a more stable form, the formation of by-products that accelerate the reduction in whiteness is suppressed.

Therefore, the inventors of the present invention provide a white polyester composite film containing rutile type titanium dioxide particles, especially a surface treatment with aluminum oxide as a hiding agent, which contains a cavity having excellent hiding power and excellent surface strength and weather resistance against peeling. It was found that it can be manufactured.

Other components, such as colorants, light agents, fluorescent agents, and antistatic agents, may be added to the polymer mixture depending on the application of the composite film.

The resulting polymer sheet is oriented in at least one direction, for example by any of the following process procedures.

(i) passing the sheet between two or more rolls having different rotational speeds to draw the sheet (roll stretching method);

(ii) securing the end of the sheet with two or more grips and then extending the sheet (ie, tenter stretching method); And

(iii) drawing the sheet under atmospheric pressure (i.e., inflation drawing method), wherein the thermoplastic particles that are incompatible with the polyester dispersed in the polyester film base material are deformed and between the particulates of the thermoplastic resin and the polyester base material Separation occurs at the interface, forming a cavity around the particulate.

Thus, the amount of non-compatible resin mixed with the polyester may vary depending on the predetermined number of cavities but is preferably in the range of 3 to 40% by weight, preferably 8 to 35% by weight, based on the total weight of the polymer mixture. An amount of 3% or less by weight is difficult to increase the number of cavities so that the desired flexibility, light weight and drawability cannot be achieved. On the other hand, the amount of 40% by weight or more is unsuitable because the heat resistance and strength inherent in the polyester film, particularly toughness, are greatly damaged.

In addition, the coating layer may be formed on the surface of the cavity-containing polyester composite film according to the present invention, and improves adhesion and wettability to the ink and the coating agent. The coating layer is preferably composed mainly of polyester resins such as polyurethane resins, polyester urethane resins and acrylic resins, although conventional resins may be used to improve the favorability of the polyester film.

Conventional process stops such as a grabber coating method, a key coating method, a dip method, a spray coating method, a curtain coating method, an air knife coating method, a blade coating method and a reverse rolling method may be used for forming the coating layer.

The coating layer comprises (i) at the surface of the polymer sheet before the orientation step; (ii) on the surface of the cavity-containing composite film oriented in one direction before being oriented at right angles in the other direction; Or (iii) formed on the surface of the cavity-containing composite film after orientation completion.

In the present invention, the polyester base layer (A) and the outer surface layer (B) should be laminated with a composite film. The lamination process is not particularly limited, and a conventional process, that is, a method in which two individual films oriented biaxially corresponding to the polyester base layer (A) and the outer surface layer (B) are in close contact with each other; And a method in which the unstretched sheet component corresponding to the outer surface layer (B) is in close contact with the surface of the film oriented in one direction corresponding to the polyester base layer (A), and is also oriented perpendicularly and in another direction. From a manufacturing point of view, the respective materials for the polyester base layer (A) and the outer surface layer (B) are extruded independently from the individual extruders so that the extrudate proceeds to a single die to form an unstretched sheet and at least in one direction. Most preferably, they are laminated by coextrusion techniques that are oriented.

The condition for the orientation of the unstretched sheet is important in terms of producing a hollow polyester-based composite film having excellent toughness. For example, when the continuous biaxial stretching process commonly used in the art is applied, the following conditions are proposed. When the continuous sheet of the polymer mixture is drawn in its longitudinal direction (ie, machine direction (MD)) by the bowl drawing method and then in its width direction (ie, transverse direction TD) by the tenter drawing method, roll drawing The temperature and draw ratio in the process (or MD draw) are preferably at or below the glass transition temperature of + 30 ° C. and 2.0 to 5.0 for forming a plurality of cavities, and the temperature and draw ratio in the tenter draw process (or TD draw) are It is preferably 100 to 150 ° C. and 2.8 to 5 for stable production of the composite film without cutting.

In addition, the stretched cavity-containing film is preferably heat-treated at a temperature of 200 ° C or higher, preferably 220 ° C or higher, more preferably 230 ° C or higher. At this time, the heat treatment should involve relaxation of the ratio of 3% to 8%. When the heat treatment is treated with a temperature of 200 ° C. or lower or a 3% ratio relaxation, it is not possible to obtain a cavity-containing composite film having a heat shrinkage of 2%, preferably 1.7% or less, and more preferably 1.5%, at 150 ° C. .

With respect to the resultant cavity-containing polyester composite film, the void ratio of the surface portion having a thickness of 3 µm from the surface of the polyester base layer (A) was 8 vol% or less, and the average void ratio of the composite film was 10 to 50 vol%. It is preferably 10 to 40% by volume and more preferably 10 to 35% by volume.

If the void ratio of the surface portion having a thickness of 3 µm from the surface of the polyester base layer (A) is 8 vol% or more, a cavity-containing composite film having satisfactory surface strength cannot be obtained. In addition, if the surface portion having a void ratio of 8% by volume or less has a thickness of 3 m or less from the surface of the polyester base layer (A), the resulting composite film does not have sufficient surface strength to withstand peeling. Thus, in the present invention, the surface portion of the polyester base layer (A) containing a slight requirement, i.e., a small amount of cavity compared with the central portion thereof, has a thickness of 3 mu m or more; The void ratio of the surface portion having a thickness of 3 μm from the surface of the polyester base layer (A) is 8% by volume or less; There is a requirement that the uniformity ratio of the composite film should be 10 to 50% by volume. If the average void ratio is 10 vol% or less, the resultant cavity-containing polyester composite film does not have sufficient flexibility, drawability and curability, while the average void ratio of 50 vol% or more is because the composite film is sometimes cut during the stretching process. It is difficult to manufacture a cavity-containing polyester composite film having a. The resulting composite film obtained is inadequate because of its insufficient surface and tensile strengths.

The co-containing polyester composite film according to the present invention has excellent toughness and preferably has an initial modulus of 300 kg / mm 2 or more. The resulting composite film has low toughness when the initial modulus is 300 kg / mm 2 or less.

The co-containing polyester composite film according to the present invention is particularly excellent in surface strength compared to the conventional co-containing polyester composite film produced by using polystyrene or polypropylene as a co-generating agent, so that the polyester base layer (A) Layer separation at the interface between the outer surface layer and the outer surface layer B does not occur.

Joint-containing polyester composite film according to the present invention is a label, sticker, poster, card, recording paper, packaging material, printing paper for video image printer, bar code label, printing paper for bar code printer, thermal recording paper, pre-sublimation record Paper, ink-jet recording paper, offset printing paper, foamed printing paper, maps, dust-free paper, display boards, white tubes for calligraphic paintings, white plates for calligraphy equipped with electronic copying systems, photo printing Paper, decorative paper, wallpaper, construction materials, banknotes, release paper, envelopes, calendars, magnetic cards, tresing papers, slips, delivery slips, pressure-sensitive recording papers, copy papers, clinical examination papers, reflector plates for antennas, display reflectors, etc. It can be used as a substrate for.

In the present invention, polyester is used as the film substrate because the resultant cavity-containing polyester composite film is satisfactory in heat resistance and mechanical strength. The polyester is then mixed with a thermoplastic resin that is incompatible with the polyester to produce a polymer mixture. By this process procedure, the fine particles of the thermoplastic resin are dispersed in the polyester film base material. The dispersed particulates cause separation from the polyester film substrate during the orientation or stretching process to form cavities around the particulates.

The unstretched sheet of the polymer mixture is oriented in at least one direction, forming a large number of fine cavities in the final composite film. Therefore, the composite film can be reduced in weight with the formed microcavity and the workability is good and the price per area is low. The resultant cavity-containing composite film has increased flexibility, which enables clear printing or transfer. Moreover, the cavity-containing composite film has satisfactory light concealment and whiteness. In addition, since a plurality of peaks derived from the thermoplastic resin are formed on the outer surface layer B, writing by a pencil or a ballpoint pen is possible.

The porosity of the surface portion having a thickness of 3 μm from the surface of the polyester base layer (A) becomes 8 vol% or less because the surface strength is particularly increased, while the average co-periodity of the composite film is appropriate drawing and curability. Since it is obtained, it becomes 10 to 50 volume%.

Substantial absence of cavities that may form from the cavitation system at the interface between the polyester base layer (A) and the outer surface layer (B) prevents the occurrence of surface peeling that may be caused by such cavities. The co-containing polyester composite film thus obtained has sufficient heat resistance and mechanical strength for use in posters, labels, trade slips, delivery slips, bar code labels and various recording media such as pressure-sensitive recording media.

EXAMPLE

The present invention will be described in more detail with reference to the following examples and comparative examples, but the scope of the present invention is not limited thereto.

The measurements and evaluations used in this and comparative examples are described below:

(1) intrinsic viscosity of polyester

Polyester was dissolved in the mixed solvent of phenol (6 weight part) and tetrachloroethane (4 weight part). The intrinsic viscosity of this polyester solution was measured at 30 degreeC.

(2) Melt Flow Index of Polystyrene Resin

The melt flow index of the polystyrene resin was measured under a load of 200 ° C. and 5 kg according to the process procedure of JIS K-7210.

(3) the apparent specific gravity of the film

The film was cut into 5.00 cm x 5.00 cm square samples. The thickness of the sample was measured at 50 places to obtain an average thickness t (µm) of the sample. Therefore, the weight W (g) of the sample was measured to 0.1 mg, and the apparent specific gravity of the film was calculated by the following equation.

Apparent specific gravity = W / (5 × 5 × t × 10000)

(4) the average void ratio of the film

The average void ratio of the composite film was calculated by the following equation.

Average void rate (% by volume) = 100 × (1- true / apparent cost)

In the formula: Cost = x₁ / d₁ + x₂ / d₂ + x₃ / d₃ + ... + xi / di + ... and apparent cost = 1 / the apparent specific gravity of the film, where xi is the weight fraction of component i And di are true weights of component i. The true specific gravity value used in the system in the examples is 1.40 for polyethylene terephthalate, 1.05 for general-purpose polystyrene resin, 3.90 for enanthate type titanium dioxide, 4.20 for rutile type titanium dioxide, 2.70 for calcium carbonate, and 2.20 for zeolite.

(5) the void ratio of the surface portion of the polyester base layer

The composite film was embedded in an epoxy resin which was subsequently cured, and the embedded film was cut with a microtome to form a cut surface perpendicular to the film surface parallel to the longitudinal direction of the film. At this time, the direction cut into the microtome is parallel to the longitudinal direction of the film. After curing, the cut surface was magnified 2000 times with an electron microscope. A cross-sectional photograph of a film close to the surface was obtained with a scanning electron microscope (model S-510, Hitachi). Then, a drawing obtained by projecting and painting all of the cavities inherent in the surface portion having a thickness of 3 μm from the surface of the polyester base layer (A) with a tracing film was analyzed by an image analyzer (Luzec IID, Nireco). The void ratio (volume%) was calculated.

(6) Cavity of the central portion of the polyester base layer

The porosity of the central portion having a thickness of about 20 μm at the center of the polyester base layer was measured by the same procedure as described in (5) above.

(7) Definition of the interface between the polyester base layer (A) and the outer surface layer (B) and the thickness of the outer surface layer (B)

Sampling was carried out in the same manner as described in (5) above. The cut surface was observed from the surface of the outer surface layer (B) towards the polyester base layer (A), and the interface between the polyester base layer (A) and the outer surface layer (B) at the point where the dispersed particles were first found in the non-compatible resin. As prescribed. The thickness of the outer surface layer B was defined as the distance from the surface to this interface.

(8) cavity size and presence of cavity at the interface between polyester base layer (A) and outer surface layer (B)

Longer diameter observed on the opposite side of the non-compatible resin particle in the direction of movement of the blades of the microtome with respect to the interface as defined in (7) above and the limit of the non-compatible resin particle on the polyester film substrate. The cavity of was measured in units of 1 μm. Longer diameter measurements up to 1 μm or less have little significance in terms of deformation of the film during cutting. Although there are a number of cavities that cannot be measured in this way, these cavities are so fine that they do not affect the surface strength of the composite film against peeling. Therefore, if no cavity is observed in this way, it is specified that no cavity exists.

(9) initial modulus

Initial modulus was measured according to the procedure of ASTM D-882-81 (Method A).

(10) heat shrinkage

The film was cut into 10 mm wide, 250 mm long samples. A pair of marks were given to the sample at a distance of 200 mm. The sample was then fixed under constant tension 5 g to measure the distance A between the marks. The sample was then placed in an oven under tension for 30 minutes at 150 ° C. to determine the distance (B) between the marks. Heat shrinkage was calculated by the following equation.

Heat Shrinkage (%) = (A-B) / A × 100

(11) light transmittance

The light transmittance of the film was determined in accordance with JIS-K6714 by a pore integrating sphere type H.T.R. It measured with the meter (made by Nippon Precision Co., Ltd.). The smaller the value of the light transmittance, the higher the hiding power.

(12) the surface strength of the film against peeling

The surface strength of the film was evaluated by peel test with two kinds of adhesive cellophane tape (18 mm, 9 mm width; Nichiban, respectively). The use of smaller width adhesive cellophane tape results in greater force per unit area, resulting in easier peeling. The adhesive cellophane tape sticks to the film and then peels in a direction of about 150 ° angle and the film remains flat. The surface strength of the film was classified as follows according to the area of the peeled surface portion of the composite-containing composite film.

Class 5: The entire surface portion was peeled off.

Class 4: Almost the surface portion was peeled off.

Class 3: Half of the surface portion was peeled off.

Class 2: Almost no surface portion was peeled off.

Class 1: The surface part did not peel at all.

(13) Stack-writing Property

Ten films were laid out in layers and applied with a ballpoint pen to write a letter on the top film. When a mark of letters was seen on the lowermost film, the lamination-writing performance of the film was evaluated as " good ", and when there was no indication, the lamination-writing performance was evaluated as " bad ".

(14) whiteness

According to the method B of JIS-L1015-1981, the whiteness was measured using the color difference meter (model N1001, the Nippon Denki Kogyo Co., Ltd. make).

(15) Surface roughness

According to the JIS-B0601-1982 procedure, the average roughness was measured using a surface roughness measuring instrument (Surfcom model 300A: Tokyo Precision Co., Ltd.) with a needle diameter of 2 µm, a contact pressure of 30 mg, and a cutting length of 0.8 mm. The surface roughness of the film was evaluated by this average roughness.

(16) Average particle size of inorganic particles

From the particle size of 100 arbitrary particles obtained by observing the cross section of the film at a magnification of 10000 times using a scanning electron microscope (Model S-510, manufactured by Hitachi, Inc.) for particles having spherical or cubic or intermediate forms thereof. The average particle size was calculated. Penetration type device to measure the particle size distribution by centrifugal sedimentation method (model SA-CP3, Shimatsu) by dispersing the powder in EG slurry at high speed for the particles having other shapes. It was measured by the 50% integration method.

(17) Surface Gloss

The gloss at 60 ° C., namely, the appearance state (hereinafter referred to as G1 60) was measured using a gloss measuring instrument (model VGS-1001DP, manufactured by Nippon Denki Kogyo Co., Ltd.) to evaluate glossiness as follows.

G1 60, 100-70 ... bad

69-45 ... good

44-20 ... Excellent

19-10 ... very good

Light transmittance, surface glossiness, and whiteness are shown using the average of the measured values in any 30 places while dispersing these values, which are the maximum or minimum with a greater difference from the absolute to the average.

(18) yellowing rate

The film was treated with a Q-UV UV exposure apparatus (manufactured by Q-Panel Company) for 100 hours to evaluate the yellowing factor by the difference (Δb) between the color values (b) of the white film before and after UV exposure. It was. The moisture condensation cycle and exposure cycle in the Q-UV device were both four periods. The color value (b) was measured by the colorimeter (model Z-1001, the Nippon Denshoku Industries Co., Ltd.) according to the method B of JIS-L1015-1981 (two-wavelength method). The smaller the color value (b) of the film, the stronger the flutine and excellent whiteness. The larger the color value (b) of the film, the stronger the yellow tint and the poorer the whiteness. Therefore, the larger the difference Δb between the color values b of the film before and after ultraviolet exposure, the greater the decrease in the whiteness of the film.

Example 1

As a raw material for the polyester base layer (A), a polymer mixture of 75 wt% polyethylene terephthalate having an intrinsic viscosity of 0.62 and 25 wt% of general-purpose polystyrene having a melt flow index of 2.0 g / 10 min was used. As a raw material for the outer surface layer (B), a polymer mixture of 95% by weight polyethylene terephthalate having an intrinsic viscosity of 0.62 and 5% by weight of rutile titanium dioxide having a mean particle size of 0.3 µm was used. These mixtures were melted independently in another twin screw extruder at a maximum temperature of 295 ° C. and melt-extruded at 290 ° C. from a T-die with 1.0 mm slits with an average flow rate of 8.8 m / sec.

An unstretched sheet composed of a polyester base layer (A) having a thickness of 440 μm inserted into a pair of outer surface layers (B) each having a thickness of 30 μm by solidifying the extrudate by contact with the surface of the cooling roll by electrostatic force. Got it.

The unstretched sheet is then drawn at 83 ° C. by a roll stretching machine at a 4.0 draw ratio in its longitudinal direction (ie MD direction) and then at 130 ° C. by tenter at a draw ratio 3.5 in its width direction (ie TD direction). Cavity containing a polyester base layer (A) having a thickness of 44 μm inserted between a pair of outer surface layers (B) each having a thickness of 3 μm by heat treatment at 235 ° C. while stretching to relax the sheet at 4%. Polyester-based composite film was prepared. Therefore, the physical properties of the formed cavity-containing composite film is shown in Table 1 and Table 2. In particular, the void ratio of the surface portion of the polyester base layer (A) of the composite film was 7% by volume, and the average void ratio of the composite film was 37% by volume. The thickness of the surface portion containing a few cavities was about 3 μm. In addition, the co-containing polyester composite film obtained in this Example was excellent in surface strength and good lamination-writing.

When the unstretched sheet of this example was measured by a scanning electron microscope, the average particle size of the fine particles of polystyrene was 6.5 탆 in the center portion and 1.2 탆 in the surface portion of the polyester base layer (A).

Example 2

80 wt% of polyethylene terephthalate having an intrinsic viscosity of 0.62, 15 wt% of general-purpose polystyrene having a melt-flop index of 2.0 g / 10 minutes, and 5 wt% of an energetic titanium dioxide as a raw material for the polyester base layer (A) A polymer mixture of was used. As a raw material for the outer surface layer (B), a polymer mixture of 95 wt% polyethylene terephthalate having an intrinsic viscosity of 0.62 and 5 wt% of rutile titanium dioxide having an average particle size of 0.3 μm was used. These mixtures were melted independently in another twin screw extruder at a maximum temperature of 295 ° C. and then melt-extruded from a T-die with 1.0 mm slits at 290 ° C. with an average flow rate of 8.8 m / sec. The extrudate was adhered to the surface of the cooling roll by the electrostatic force and solidified to obtain an unstretched sheet composed of a polyester base layer (A) having a thickness of 440 μm sandwiched between a pair of outer surface layers (B) each having a thickness of 30 μm. .

The unstretched sheet is then drawn at 83 ° C. with a drawer at a draw ratio of 3.5 in its longitudinal direction (ie MD direction) and then at 130 ° C. with a tenter at a draw ratio of 3.5 in its width direction (ie, TD direction). In addition, the joint-containing polyester system composed of a polyester base layer (A) having a 44 μm thickness inserted between a pair of outer surface layers each having a thickness of 3 μm by heat treatment at 235 ° C. while stretching the sheet at 4%. A composite film was obtained.

The physical properties of the resultant cavity-containing composite film are shown in Tables 1 and 2. In particular, the void ratio of the surface portion of the polyester base layer (A) of the composite film was 2% by volume, and the average void ratio of the composite film was 21% by volume. The thickness of the surface portion containing a few cavities was about 3 mu m.

When the unstretched sheet of this example was observed with a scanning electron microscope, the average particle size of the fine particles of polystyrene was 5.0 µm at the center portion and 0.7 µm at the surface portion of the polyester base layer (A).

Example 3

An unstretched sheet having a thickness of 500 μm was prepared in the same manner as described in Example 2 except that the polymer mixture as a raw material for the polyester base layer (B) was melted in a twin screw extruder at a maximum temperature of 292 ° C. Got by devaluation.

Then, the unstretched sheet was stretched and heat treated by the same procedure as described in Example 2, and the polyester base layer (A) having a thickness of 44 μm was inserted between the pair of outer surface layers (B) each having a thickness of 3 μm. A hollow polyester composite film was obtained. The physical properties of the resultant cavity-containing composite film are shown in Tables 1 and 2. In particular, the void ratio of the surface portion of the polyester base layer (A) of the composite film was 1% by volume, and the average void ratio of the composite film was 21% by volume. The thickness of the surface portion containing a few cavities was about 3 mu m. The unstretched sheet of this example was observed with a scanning electron microscope, and the average particle size of the fine particles of polystyrene was 5.0 µm in the center portion and 0.7 µm in the surface portion of the polyester base layer (A).

Example 4

Example of an unstretched sheet having a thickness of 500 μm except that the polymer mixture as a raw material for the polyester base layer (A) and the outer surface layer (B) was independently melted in different twin screw extruders at a maximum temperature of 290 ° C. A joint-containing polyester-based composite film composed of a polyester base layer (A) having a thickness of 44 µm inserted and annealed by a pair of outer surface layers (B) having a thickness of 3 µm, respectively, by the same procedure as described in (2). Got it. The physical properties of the resultant cavity-containing composite film are shown in Tables 1 and 2. In particular, the void ratio of the surface portion of the polyester base layer (A) of the composite film was 2% by volume, and the average void ratio of the composite film was 21% by volume. The thickness of the surface portion containing a few cavities was about 3 mu m.

When the unstretched sheet of this example was observed with a scanning electron microscope, the average particle size of the fine particles of polystyrene was 5.0 µm at the center portion and 0.7 µm at the surface portion of the polyester base layer (A).

Example 5

As a raw material for the polyester base layer (A), a polymer mixture of 75% by weight polyethylene terephthalate having an intrinsic viscosity of 0.62 and 25% by weight of general-purpose polystyrene having a melt flow index of 2.0 g / 10 minutes was used. As a raw material for the outer surface layer (B), a polymer mixture of 95% by weight polyethylene terephthalate having an intrinsic viscosity of 0.62 and 5% by weight of rutile titanium dioxide having an average particle size of 0.3 µm was used. An unstretched sheet composed of a polyester base layer (A) having a thickness of 440 μm inserted between a pair of outer surface layers (B) each having a thickness of 30 μm by solidifying the extrudate by contact with the surface of the cooling roll by electrostatic force. Got it.

The temperature of the twin screw-extruder for the melt extrusion of the sheet component corresponding to the polyester base layer (A) was 250 ° C. in the closest part to the raw material feed zone and gradually increased to the maximum temperature of 295 ° C. in the melting zone. . The polymer mixture was kneaded for about 10 minutes in the melting zone and the screw tip temperature was 290 ° C. Thereafter, the temperature of the melting line gradually lowered so that the final temperature of the T-die was 280 ° C.

The temperature of the twin screw-screw extruder for the melt extrusion of the sheet component corresponding to the pair of outer surface layers (B) was 250 ° C. at the portion closest to the raw material supply zone, and gradually increased to a maximum temperature of 285 ° C. The polymer mixture was kneaded for about 1 minute in the melting zone and the temperature at the screw tip was 280 ° C. Thereafter, the raw materials were supplied to the melting line while maintaining the temperature, and the sheet component corresponding to the outer surface layer (B) was attached to each side of the sheet component corresponding to the polyester base layer (A). The laminated sheet component was fed by itself into the T-die.

Then, the unstretched sheet is stretched at 83 ° C. by a drawer at a draw ratio of 4.0 in its longitudinal direction (ie MD direction) and then drawn at 130 ° C. by tenter at a draw ratio of 3.5 in its width direction (ie, TD direction). And the sheet-containing polyester composite composed of a 44-micrometer-thick polyester base layer (A) sandwiched between a pair of outer surface layers (B) each having a 3-micrometer thickness by heat-treating at 235 ° C while relaxing the sheet at a 4% ratio. A film was obtained. The physical properties of the resultant cavity-containing composite film are shown in Tables 1 and 2. In particular, the void ratio of the surface portion of the polyester base layer (A) of the composite film was 7% by volume, and the average void ratio of the composite film was 37% by volume. The thickness of the surface portion containing a few cavities was about 3 mu m.

When the unstretched sheet of this example was observed with a scanning electron microscope, the average particle size of the fine particles of polystyrene was 6.5 mu m in the central portion thereof and 1.0 mu m in the surface portion of the polyester base layer (A).

In the cavity-containing polyester composite film obtained in Examples 1 to 5, the ratio of the length to the thickness of the polystyrene particles present at the interface between the polyester base layer (A) and the outer surface layer (B) was 10 or more. When observed under an electron microscope at 2000 times magnification, no cavity was formed from the polystyrene particles at the interface. Therefore, these cavity-containing composite films had excellent surface strength, no layer separation, and good lamination-writing performance.

Example 6

A raw material for the polyester base layer (A) is a polymer mixture of 80% by weight of polyethylene terephthalate having an intrinsic viscosity of 0.62% and 15% by weight of general-purpose polystyrene having a melt flow index of 2.0 g / 10 minutes, and 5% by weight of enetaceous type titanium dioxide. A non-stretched sheet having a thickness of 500 mu m was obtained according to the same procedure as described in Example 5 except that it was used as. Then, the unstretched sheet was stretched at 83 ° C by a roll stretching machine at 3.5 draw ratio in its longitudinal direction (ie, MD direction) and then stretched at 130 ° C by tenter at 3.5 draw ratio in its width direction (ie, TD direction). Thus, a cavity-containing polyester composite film composed of a polyester base layer (A) having a thickness of 44 μm was inserted between a pair of outer surface layers each having a thickness of 3 μm. The physical properties of the resultant cavity-containing composite film are shown in Tables 1 and 2. In particular, the void ratio of the surface portion of the polyester base layer (A) of the composite film was 2% by volume, and the average void ratio of the composite film was 21% by volume. The thickness of the surface portion containing a few cavities was about 3 mu m.

When the unstretched sheet of this example was observed with a scanning electron microscope, the average particle size of the fine particles of polystyrene was 5.0 µm at the center portion and 0.7 µm at the surface portion of the polyester base layer (A).

Example 7

Polymer mixture of 80% by weight polyethylene terephthalate with an intrinsic viscosity of 0.62, 15% by weight of general-purpose polystyrene having a melt flow index of 2.0 g / 10 minutes, and 5% by weight of enetaceous titanium dioxide as a raw material for the polyester base layer (A). Was used. As a raw material for the outer surface layer (B), a polymer mixture of 95% by weight polyethylene terephthalate having an intrinsic viscosity of 0.62 and 5% by weight of rutile titanium dioxide having an average particle size of 0.3 µm was used.

A biaxial screw extruder was connected in series for melt extrusion of the sheet component corresponding to the outer surface layer (B). The raw material was kneaded from the raw material feed zone of one twin screw extruder to the outlet of the other twin screw extruder for about 15 minutes. The kneaded raw material was filtered through a membrane having a 10 μm hole, melted at a maximum temperature of 290 ° C., and melt-extruded from a T-die to correspond to the sheet component corresponding to the polyester base layer (A) as the outer surface layer (B). It was inserted between a pair of sheet components. The extrudate was solidified on the surface of the cooling roll by electrostatic force to obtain an unstretched sheet having a thickness of about 500 μm. Thereafter, the unstretched sheet was stretched at 90 ° C by a roll stretching machine at 3.4 draw ratio in its longitudinal direction (ie, MD direction) and then stretched at 135 ° C by tenter at 3.4 draw ratio in its width direction (ie, TD direction). By releasing the sheet at a rate of 3%, and performing a heat treatment at 235 ° C., a joint-containing polyester-based composite composed of a polyester base layer (A) having a thickness of 42 μm inserted between a pair of outer surface layers (B) having a thickness of 4 μm, respectively. A film was obtained. The physical properties of the resultant cavity-containing composite film are shown in Tables 3 and 4. The cavity-containing polyester composite film obtained in this example had a uniform whiteness and hiding effect.

Example 8

The polymer mixtures as raw materials for the polyester base layer (A) and the outer surface layer (B) were respectively connected in a twin screw extruder at a maximum temperature of 310 ° C. and in two twin screw extruders connected in series at a maximum temperature of 285 ° C. A non-stretched sheet having a thickness of about 500 μm was obtained by the same procedure as described in Example 7, except that it was independently melted. Thereafter, the unstretched sheet was stretched and heat-treated according to the same procedure as in Example 7 to consist of a 42 탆 thick polyester base layer 2 sandwiched between a pair of outer surface layers B each having a thickness of 4 탆. A joint-containing polyester composite film was obtained.

The physical properties of the resultant cavity-containing composite film are shown in Tables 3 and 4. The co-containing polyester composite film obtained in this example was uniform in whiteness and hiding effect.

Example 9

The polymer mixtures as raw materials for the polyester base layer (A) and the outer surface layer (B) are independently of each other in a twin screw extruder connected in series at a maximum temperature of 295 ° C. and a twin screw extruder at a maximum temperature of 285 ° C. Except for melting, an unstretched sheet having a thickness of about 500 μm was obtained by the same procedure as described in Example 7. Thereafter, the unstretched sheet was drawn and heat treated by the same procedure as described in Example 7, and the cavity composed of a polyester base layer (A) having a thickness of 42 탆 inserted between a pair of outer surface layers each having a thickness of 4 탆. The containing polyester composite film was obtained. The physical properties of the resultant cavity-containing composite film are shown in Tables 3 and 4.

The co-containing polyester composite film obtained in this example was uniform in whiteness and hiding effect.

Example 10

As a raw material for the polyester base layer (A), a polymer mixture of 75% by weight polyethylene terephthalate having an intrinsic viscosity of 0.62 and 25% by weight of general-purpose polystyrene having a melt-floated index of 2.0 g / 10 minutes was used. As a raw material for the outer surface layer (B), a polymer mixture of 95% by weight polyethylene terephthalate having an intrinsic viscosity of 0.62 and 5% by weight of rutile titanium dioxide having an average particle size of 0.3 µm was used. These mixtures were melted independently in another two-screw extruder and melt-extruded from a T-die with 1.0 mm slits at an average flow rate of 8.8 m / sec. The ejected material was solidified on the surface of the cooling roll by electrostatic force to obtain an unstretched sheet composed of a 440 µm thick polyester base layer (A) inserted between a pair of outer surface layers (B) each having a thickness of 30 µm. .

For melt extrusion of the sheet component corresponding to the polyester base layer (A), the temperature of the twin screw-extruder was 250 ° C. in the closest part to the raw material supply zone and gradually increased to a maximum temperature of 295 ° C. in the melting zone. The polymer mixture was kneaded for about 10 minutes in the melting zone and the screw tip temperature was 290 ° C. The temperature of the melting line was then lowered gradually and the final temperature at the T-die was 280 ° C.

In order to melt-extrude the sheet components corresponding to the pair of outer surface layers (B), the temperature of the twin screw extruder was 250 ° C. at the portion closest to the raw material supply zone of one twin screw extruder, and gradually the maximum temperature was 295. Raised to ℃. The raw material was kneaded from the raw material feed zone of one twin screw extruder to the outlet of another twin screw extruder for 15 minutes and filtered through a membrane having a 10 μm hole. The temperature at the screw top of the other twin screw extruder was 280 ° C. Thereafter, the raw material was supplied to the melting line while maintaining the temperature thereof, and the sheet component corresponding to the outer surface layer (B) was immediately transferred to the polyester base layer (A) before being introduced into the T-die. It adhered to the side. The laminated sheet component was fed into its own T-die.

The unstretched sheet was then drawn at 83 ° C. with a drawer at a draw ratio of 4.0 in its longitudinal direction (ie MD direction) and then at 140 ° C. by tenter at a draw ratio 3.5 in its width direction (ie TD direction). Commonly containing polyester consisting of a polyester base layer (A) having a thickness of 44 μm inserted between a pair of outer surface layers (B) each having a thickness of 3 μm by stretching and heat-treating at 235 ° C. while relaxing the sheet at a 3% ratio. A system composite film was obtained. The physical properties of the resultant cavity-containing composite film are shown in Tables 5 and 6. In particular, the void ratio of the surface portion of the polyester base layer (A) of the composite film was 7% by volume, and the average void ratio of the composite film was 37% by volume. The sphere of the surface portion containing a few cavities was about 3 mu m.

In the cavity-containing polyester composite film obtained in this example, the ratio of the length to the thickness of the polystyrene particles inherent in the interface between the polyester base layer (A) and the outer surface layer (B) was 10 or more. When observed at 2000 times magnification with an electron microscope, no cavity was formed from polystyrene particles inherent in the interface. Therefore, these cavity-containing composite films had excellent surface strength, no delamination and excellent lamination-writing performance.

When the unstretched sheet of this example was observed with a scanning electron microscope, the average particle size of the fine particles of polystyrene was 6.5 mu m in the center portion and 1.2 mu m in the surface portion of the polyester base layer (A).

Example 11

A polymer mixture of 80% by weight of polyethylene terephthalate having an intrinsic viscosity of 0.62, 15% by weight of general-purpose polystyrene having a melt flow index of 2.0 g / 10 minutes, and 5% by weight of enanthate titanium dioxide was used as a raw material for the polyester base layer (A). Except for the use, the unstretched sheet having a thickness of about 500 μm was obtained by the same procedure as described in Example 10. Thereafter, the film was drawn at 83 ° C. with a drawer at a draw ratio of 3.5 in its longitudinal direction (ie, in the MD direction) and then drawn at 140 ° C. by a tenter at a draw ratio of 3.5% in its width direction (ie, in the TD direction). Heat treatment was performed at 235 ° C. while relaxing to obtain a cavity-containing polyester composite film composed of a polyester base layer (A) having a 44 μm thickness interposed between a pair of outer surface layers each having a 3 μm thickness. The physical properties of the resultant cavity-containing composite film are shown in Tables 5 and 6. In particular, the void ratio of the surface portion of the polyester base layer (A) of the composite film was 2% by volume, and the average void ratio of the composite film was 21% by volume.

The thickness of the surface portion containing a few cavities was about 3 mu m.

The undrawn sites of this example were observed with a scanning electron microscope to find that the average particle size of the fine particles of polystyrene was 5.0 µm in the center portion and 0.7 µm in the surface portion of the polyester base layer (A).

Example 12

An unstretched sheet having a thickness of about 500 μm was obtained by the same procedure as described in Example 11 except that the polymer mixture was melted at a maximum temperature of 285 ° C. as a raw material for the outer surface layer (B).

Thereafter, the non-stretched sheet was stretched and heat treated by the same procedure as described in Example 11, and the cavity-containing poly consisting of a 44 µm thick polyester base layer (A) interposed between a pair of outer surface layers each having a thickness of 3 µm. An ester composite film was obtained.

The physical properties of the resultant cavity-containing composite film are shown in Tables 5 and 6.

In particular, the void ratio of the surface portion of the polyester base layer (A) of the composite film was 2% by volume, and the average void ratio of the composite film was 21% by volume.

The thickness of the surface portion containing a few cavities was about 3 mu m.

The unstretched sheet of this example was observed with a scanning electron microscope, and the average particle size of the polystyrene fine particles was 5.0 µm at the center portion and 0.7 µm at the surface portion of the polyester base layer (A).

Example 13

A polymer mixture of 90% by weight polyethylene terephthalate having an intrinsic viscosity of 0.62 and 10% by weight of rutile titanium dioxide having an average particle size of 0.3 µm was used as a raw material for the outer surface layer (B), as described in Example 12. By the procedure, an undrawn sheet of about 500 mu m thickness was obtained.

Thereafter, the unstretched sheet was drawn and heat treated by the same procedure as described in Example 12 to contain a cavity composed of a polyester base layer (A) having a thickness of 44 μm sandwiched between a pair of outer surface layers each having a thickness of 3 μm. A polyester composite film was obtained.

The physical properties of the resultant cavity-containing composite film are shown in Tables 5 and 6.

In particular, the void ratio of the surface portion of the polyester base layer (A) of the composite film was 2% by volume, and the average void ratio of the composite film was 21% by volume.

The thickness of the surface portion containing a few cavities was about 3 mu m.

The unstretched sheet of this example was observed with a scanning electron microscope. The average particle size of the polystyrene fine particles was 5.0 µm at the center portion and 0.7 µm at the surface portion of the polyester base layer (A).

Comparative Example 1

An unstretched sheet having a thickness of about 500 μm was obtained by the same procedure as described in Example 12 except that the sheet component corresponding to the outer surface layer (B) was not contained in the sheet.

Thereafter, the unstretched sheet was stretched and heat treated by the same procedure as described in Example 12 to obtain a co-containing polyester composite film composed of only the polyester base layer (A) having a thickness of 50 µm.

The coolness of the resultant cavity-containing composite film is shown in Tables 5 and 6.

In particular, the void ratio of the surface portion of the polyester base layer (A) of the composite film was 2% by volume, and the average void ratio of the composite film was 21% by volume.

The thickness of the surface portion containing a few cavities was about 3 mu m.

The unstretched sheet of this example was observed with a scanning electron microscope, and the average particle size of the fine particles of polystyrene was 5.0 µm at the center portion and 0.7 µm at the surface portion of the polyester base layer (A).

Comparative Example 2

As a raw material for the polyester base layer (A) and the outer surface layer (B), the polymer mixture was melted independently in another twin screw-screw extruder with a T-die with 1.0 mm slits at an average flow rate of 4.4 m / sec. A non-stretched sheet having a thickness of about 500 μm was obtained by the same procedure as described in Example 12 except that the melt-extrusion was performed.

The raw material was kneaded from the raw material feed zone of one twin screw extruder to the outlet of the other twin screw extruder for about 2 minutes.

Thereafter, the unstretched sheet was stretched and heat-treated by the same procedure as described in Example 11, consisting of a 44-micrometer-thick polyester base layer (A) sandwiched between a pair of outer surface layers (B) each having a 3-micrometer thickness. A joint-containing polyester composite film was obtained.

The physical properties of the resultant cavity-containing composite film are shown in Tables 5 and 6.

In particular, the void ratio of the surface portion of the polyester base layer (A) of the composite film was 17% by volume, and the average void ratio of the composite film was 21% by volume.

The surface portion containing a few cavities was about 3 mu m thick.

The unstretched sheet of this example was observed with a scanning electron microscope, and the average particle size of the fine particles of polystyrene was 5.9 mu m in the center portion and 5.3 mu m in the surface portion of the polyester base layer (A).

Comparative Example 3

By the same procedure as described in Example 12, except that a polymer mixture of 95% by weight polyethylene terephthalate having an intrinsic viscosity of 0.62 and 5% by weight of an enetaceous type titanium dioxide was used as a raw material for the polyester base layer (A). An unstretched sheet having a thickness of 500 μm was obtained.

Thereafter, the unstretched sheet was drawn and subjected to heat treatment by the same procedure as described in Example 12, and consisted of a 44 탆 thick polyester base layer A interposed between a pair of outer surface layers B each having a thickness of 3 탆. A joint-containing polyester composite film was obtained.

The physical properties of the resultant cavity-containing composite film are shown in Tables 5 and 6.

In this example no co-generating agent (ie, thermoplastic resin incompatible with polyester) was used. Therefore, the resultant cavity-containing composite film had no fine voids in the polyester base layer (A) and was unsuitable in terms of light weight due to the increase in apparent specific gravity.

Example 14

By the same procedure as described in Example 12, except that a polymer mixture of 95% by weight polyethylene terephthalate having an intrinsic viscosity of 0.62 and 5% by weight of calcium carbonate having an average particle size of 0.6 µm was used as a raw material for the outer surface layer (B). An unstretched sheet having a thickness of about 500 μm was obtained.

Thereafter, the non-stretched sheet was drawn and heat-treated by the same procedure as described in Example 12 to form a cavity-containing poly consisting of a 44 µm thick polyester base layer (A) sandwiched between a pair of outer surface layers each having a thickness of 3 µm. An ester composite film was obtained.

The physical properties of the resultant cavity-containing composite film are shown in Tables 5 and 6.

In particular, the void ratio of the surface portion of the polyester base layer (A) of the composite film was 2% by volume, and the average void ratio of the composite film was 21% by volume.

The thickness of the surface portion containing a few cavities was about 3 mu m.

The unstretched sheet of this example was observed with a scanning electron microscope, and the average particle size of the fine particles of polystyrene was 5.7 mu m in the center portion and 0.7 mu m in the surface portion of the polyester base layer (A).

Example 15

A polymer mixture of 95% by weight polyethylene terephthalate having an intrinsic viscosity of 0.62 and 5% by weight of calcium carbonate having an average particle size of 1 μm was used as the raw material for the outer surface layer (B), and was subjected to the same procedure as described in Example 12. To give an unoriented sheet having a thickness of about 500 µm.

Thereafter, the unstretched sheet was drawn and heat treated by the same procedure as described in Example 12 to form a cavity-containing poly consisting of a 44 µm thick polyester base layer (A) interposed between a pair of outer surface layers each having a thickness of 3 µm. An ester composite film was obtained.

The physical properties of the resultant cavity-containing composite film are shown in Tables 5 and 6.

In particular, the void ratio of the surface portion of the polyester base layer (A) of the composite film was 2% by volume, and the average void ratio of the composite film was 21% by volume.

The thickness of the surface portion containing a few cavities was about 3 mu m.

The unstretched sheet of this example was observed with a scanning electron microscope, and the average particle size of the fine particles of polystyrene was 5.7 µm at the center portion and 0.7 µm at the surface portion of the polyester base layer (A).

Example 16

98% by weight of polyethylene terephthalate with an intrinsic viscosity of 0.62 and an average particle size of 1.5 µm, the surface of which is notched, and a polymer mixture of 2% by weight of irregular spherical zeolite is used as a raw material for the outer surface layer (B) having a two-layer structure. Except for the unstretched sheet having a thickness of about 500 μm by the same procedure as described in Example 12.

Thereafter, the unstretched sheet was drawn and heat treated by the same procedure as described in Example 12 to form a cavity-containing poly consisting of a 32 µm thick polyester base layer (A) inserted between a pair of outer surface layers each having a thickness of 3 µm. An ester composite film was obtained.

The physical properties of the resultant cavity-containing composite film are shown in Tables 7 and 8.

In particular, the co-flow of the surface portion of the polyester base layer (A) of the composite film was 2% by volume, and the average void ratio of the composite film was 22% by volume.

Moreover, the relationship between the peak number and peak height in the surface part of the outer surface layer B of a composite film is shown in FIG.

As can be seen from this figure, the composite-containing composite film of this embodiment satisfied the inequality (1).

Example 17

Except that the polymer mixture of 93% by weight polyethylene terephthalate having an intrinsic viscosity of 0.62 and an average particle size of 3.3 µm, and the surface thereof was notched to use an irregular spherical zeolite 7% by weight as a raw material for the outer surface layer (B), was used. An unstretched sheet having a thickness of about 500 μm was obtained by the same procedure as described in 12.

Thereafter, the unstretched sheet was drawn and heat treated by the same procedure as in Example 12 to form a cavity composed of a 42 탆 thick polyester base layer A inserted between a pair of outer surface layers B each having a thickness of 4 탆. The containing polyester composite film was obtained.

The physical properties of the resultant cavity-containing composite film are shown in Tables 7 and 8.

In particular, the void ratio of the surface portion of the polyester base layer (A) of the composite film was 2% by volume, and the average void ratio of the composite film was 21% by volume.

Moreover, the relationship between the peak number and peak height in the surface part of the outer surface layer B of a composite film is shown in FIG. As can be seen from this figure, the composite-containing composite film of this embodiment satisfied the inequality (1).

Example 18

93% by weight of polyethylene terephthalate having an intrinsic viscosity of 0.62 and its surface having an average particle size of 1.5 µm were notched, thereby producing a polymer mixture of 4% by weight of irregular cubic zeolite and 3% by weight of rutile titanium dioxide having an average particle size of 0.3 µm. A non-drawn sheet having a thickness of about 500 μm was obtained by the same procedure as described in Example 12 except that it was used as a raw material for an outer surface layer (B) having a layered structure.

Thereafter, the unstretched sheet was drawn and heat treated by the same procedure as described in Example 12 to a polyester base layer (A) having a thickness of 40 μm sandwiched between a pair of outer surface layers (B) each having a thickness of 5 μm. A cavity-containing polyester composite film was obtained.

The physical properties of the resultant cavity-containing composite film are shown in Tables 7 and 8.

In particular, the void ratio of the surface portion of the polyester base layer (A) of the composite film was 2% by volume, and the average void ratio of the composite film was 23% by volume.

Moreover, the relationship between the peak number and peak height in the surface part of the outer surface layer B of a composite film is shown in FIG. As can be seen from this figure, the composite-containing composite film of this embodiment satisfied the inequality (1).

Example 19

The polymer mixture of 95% by weight of polyethylene terephthalate having an intrinsic viscosity of 0.62 and 5% by weight of an energetic titanium oxide having an average particle size of 0.3 µm was used as a raw material for the outer surface layer (B), as described in Example 12. By the procedure, an unstretched sheet of about 500 mu m thickness was obtained.

Thereafter, the unstretched sheet was stretched and heat treated by the same procedure as described in Example 12, and consisted of a polyester base layer (A) having a thickness of 44 µm sandwiched between a pair of outer surface layers (B) each having a thickness of 3 µm. A joint-containing polyester composite film was obtained.

The physical properties of the resultant cavity-containing composite film are shown in Tables 9 and 10.

In particular, the void ratio of the surface portion of the polyester base layer (A) of the composite film was 2% by volume, and the average void ratio of the composite film was 21% by volume.

Example 20

The same procedure as described in Example 12, except that a polymer mixture of 95% by weight polyethylene terephthalate having an intrinsic viscosity of 0.62 and 5% by weight of rutile titanium oxide having an average particle size of 0.3 µm was used as a raw material for the outer surface layer (B). To obtain an unstretched sheet having a thickness of about 500 μm.

Thereafter, by the same procedure as described in Example 12, the non-stretched sheet was stretched and heat treated to form a cavity-containing poly (44) -thick polyester base layer (A) inserted between the outer surface layers of the one phase each having a thickness of 3 µm. An ester composite film was obtained.

Table 9 and Table 10 _{2 show} the physical properties of the resultant cavity-containing composite film.

In particular, the void ratio of the surface portion of the polyester base layer (A) of the composite film was 2% by volume, and the average void ratio of the composite film was 21% by volume.

Example 21

Example 12 except that a polymer mixture of 95% by weight polyethylene terephthalate having an intrinsic viscosity of 0.62 and 5% by weight of SiO ₂ -treated rutile titanium oxide having an average particle size of 0.3 μm was used as a raw material for the outer surface layer (B). By the same procedure as described in, an undrawn sheet having a thickness of about 500 μm was obtained.

Thereafter, the unstretched sheet was stretched and heat-treated by the same procedure as described in Example 12 to obtain a 44-micrometer-thick polyester base layer sandwiched between a pair of outer surface layers (B) each having a thickness of 3 탆. A cavity-containing polyester composite film comprising A) was obtained.

The physical properties of the resultant cavity-containing composite film are shown in Tables 9 and 10.

In particular, the void ratio of the surface portion of the polyester base layer (A) of the composite film was 2% by volume, and the average void ratio of the composite film was 21% by volume.

Claims (31)

A polyester base layer (A) containing a fine cavity obtained by orienting a polymer mixture of polyester and a thermoplastic resin incompatible with the polyester in at least one direction, and mainly composed of a thermoplastic resin, It consists of at least one outer surface layer (B) formed on at least one side, the void ratio of the surface portion having a thickness of 3㎛ from the surface of the polyester base layer (A) is 8% by volume or less, the average of the composite film Cavity-containing polyester composite film, characterized in that the void ratio is 10 to 50% by volume. The cavity-containing polyester composite film according to claim 1, wherein the composite film has substantially no cavity at the interface between the polyester base layer (A) and the outer surface layer (B). The joint-containing polyester composite film according to claim 1, wherein an average void ratio of the composite film is 10 to 35% by volume. The joint-containing polyester composite film according to claim 1, wherein the outer surface layer (B) mainly consists of polyethylene terephthalate. The joint-containing polyester-based composite film according to claim 1, wherein the outer surface layer (B) mainly consists of phorea esters. The joint-containing polyester composite film according to claim 1, wherein the outer surface layer (B) mainly consists of copolyester. 7. The polyester base layer (A) according to claim 6, wherein the polyester base layer (A) contains an inorganic particle having an average particle size smaller than the average particle size of the inorganic particles contained in the outer surface layer (B) in an amount of 1 to 20% by weight. Co-containing polyester composite film. 2. The height (Y) of the peak and the surface portion of the peak according to the peak height which gives the maximum number of peaks in the surface portion of the outer surface layer B when the peak number is 50 mm ^-2 or more. A co-containing polyester composite film, characterized in that the relationship between the peak number (X) of (mm ^-2 ) satisfies the following inequality. -1.3 log X + 5.2 ≥ Y ≥ -0.77 log X + 2.31 (1) Where X ≥ 50 and Y ≥ 0 The at least one kind of the outer surface layer (B) having an average particle size of 0.3 占 퐉 and the surface notched at a ratio of 1% by weight or more in total to form an irregular spherical or cubic shape or an intermediate shape thereof. A cavity-containing polyester composite film comprising particles. 10. The cavity-containing polyester composite film according to claim 9, wherein the particles are made of heat-treated synthetic zeolite. 10. The cavity-containing polyester composite film according to claim 9, wherein the particles consist of secondary aggregates of silica microbeads. 10. The cavity-containing polyester composite film according to claim 9, wherein the particles consist of secondary aggregates of calcium carbonate fine particles. 10. The cavity-containing polyester composite film according to claim 9, wherein the particles consist of secondary aggregates of titanium oxide fine particles. The joint-containing polyester composite film according to claim 6, wherein the inorganic particles are rutile titanium dioxide particles. 15. The co-containing polyester composite film according to claim 14, wherein the inorganic particles are surface-treated particles of rutile titanium dioxide. The co-containing polyester composite film according to claim 15, wherein the rutile titanium dioxide particles are surface-treated with aluminum oxide. 8. The co-containing polyester composite film according to claim 7, wherein the inorganic particles in the polyester base layer (A) are made of thermoplastic resin which is incompatible with polyester. An information-recording paper for use in a sublimation transfer record, thermal transfer record, thermal transfer record or ink-jet record made of a joint-containing composite film according to claim 1. Photographic printing paper made of a composite-containing composite film according to claim 1. A polyester base layer (A) containing microcavities and at least one outer surface layer (B) mainly composed of thermoplastic resin and formed on at least one side of the polyester base layer (A), the outer surface layer (B) inorganic particles composed of secondary particles having a range of 0.1 to 2.0㎛ average primary particle size (R ₁₎ having a primary particle with (R ₁₎ 1.05 to 1.60 times the average secondary particle size of the value (R ₂₎ of the 1 to 30% by weight; The individual particle size of the secondary particle giving a 99% probability in the normal distribution for the presence of secondary particles smaller than the individual particle size is 4.0 times or less of the (R ₁ ) value; The average content of the shortest center-to-center distance for the inorganic particles is 5.0 times or less of the (R ₁ ) value, characterized in that the hollow polyester-based composite film. 21. The method of claim 20, wherein the outer surface layer (B) has an average particle size of 0.8 μm or more and at least 1% or more of the surface is notched to have an irregular spherical or cubic shape, or an intermediate thereof. A co-containing polyester composite film characterized by containing one kind of particles. 22. The co-containing polyester composite film as claimed in claim 21, wherein the particles consist of heat-treated synthetic zeolites. 22. The co-containing polyester composite film according to claim 21, wherein the particles consist of secondary aggregates of silica microbeads. 22. The cavity-containing polyester composite film according to claim 21, wherein the particles are composed of secondary aggregates of calcium carbonate fine particles. 22. The cavity-containing polyester composite film according to claim 21, wherein the particles consist of secondary aggregates of titanium oxide fine particles. 23. The cavity-containing polyester composite film according to claim 21, wherein the particles are rutile titanium dioxide particles. 21. A co-containing polyester composite film according to claim 20, wherein the particles of rutile titanium dioxide are surface-treated with aluminum oxide. 28. The cavity-containing polyester composite film according to claim 27, wherein the particles of rutile titanium dioxide are surface-treated with aluminum oxide. 21. The method according to claim 20, wherein the inorganic particles in the polyester base layer (A) contain inorganic particles in an amount of 1 to 20% by weight, and these inorganic particles are inherent in the thermoplastic resin which is incompatible with the polyester. Co-containing polyester composite film. An information-recording paper for use in a sublimation transfer record, thermal transfer record, thermal transfer record or ink-jet record made from a joint-containing composite film according to claim 20. Claims 20. Photo printing paper made from a composite-containing composite film according to claim 20.