KR20220125177A - Method for preparing a film having a surface pattern and a film preprared therefrom - Google Patents

Abstract

The present application relates to a preparation method of a film having a surface pattern and a film prepared therefrom. According to one example of the present application, provided is the film having a processing surface with low surface roughness and high surface uniformity. At the same time, the present application can provide appropriate roll processability (for example, slip property, winding property, running property, and the like).

Description

Method for preparing a film having a surface pattern and a film prepared therefrom

Cross Citation with Related Applications

This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0028663 dated March 04, 2021, and all contents disclosed in the documents of the Korean patent application are incorporated as a part of this specification.

technical field

The present application relates to a method for manufacturing a film having a surface pattern and a film prepared therefrom.

Polyester films are being used in various industries based on advantages such as excellent mechanical properties, chemical resistance, flexibility, transparency, and low manufacturing cost. For example, the scope of application for polyester film is for capacitors, packaging, photo film, label, decorative laminate, release film (eg, ceramic green sheet), solar white film, etc., and recently foldable display ( It is expanding to the field of foldable display).

On the other hand, in the field of electronic materials and electronic devices, high integration, weight reduction, and compactness of materials and products are required. For example, in accordance with the trend toward compactness of electronic devices, multi-layer ceramic capacitors (MLCCs) need to be highly integrated in a smaller volume. is required The refinement and thinning of the green sheet is related to the uniformity of its thickness and surface shape.

The ceramic green sheet is manufactured by applying a ceramic slurry on the silicone release layer formed on the surface of the polyester release film, and then removing the release film in the process of manufacturing the ceramic capacitor. After all, in order to manufacture a green sheet having a uniform thickness and surface shape, surface uniformity and low illuminance characteristics must be imparted to the used release polyester film.

However, in the case of the polyester film, it is being handled by the roll process in most processes for subsequent storage and use as well as in the manufacturing process including film forming and post-processing. Therefore, it is essential to ensure fairness at the time of film running or winding. In general, when the surface roughness of the film is low below a certain level, the film's running properties and slip properties are not good, and quality deterioration problems such as foam loss during winding occur. That is, in terms of materials or products for which the release film is used, the polyester film is required to have high smoothness and low illuminance characteristics. ), a high surface roughness is required (compared to the high smoothness and low illuminance characteristics required for the above-mentioned materials or products).

Therefore, there is a need for a film forming technology that allows the film processing surface to have low surface roughness and high surface uniformity, while at the same time ensuring proper roll processability.

An object of the present application is to provide a method of manufacturing a film capable of suppressing the reflow phenomenon.

Another object of the present application is to provide a film excellent in fairness (eg, running property, winding property, slip property, etc.) while having a low surface roughness.

Another object of the present application is to provide a film having a uniform surface pattern.

Another object of the present application is to provide a single-layer film having different surface roughness on both sides.

Another object of the present application is to provide a release film that can be used in various applications.

The above and other objects of the present application can all be solved by the present application described below.

In an example related to the present application, the present application relates to a method of manufacturing a film having a surface pattern. The method forms a pattern on the film surface using an imprinting method. Accordingly, a film having a surface pattern on at least one surface may be manufactured.

The so-called imprinting technology, in which a pattern is transferred using a pattern-formed device (such as a roll), induces flow and deformation of the polymer (resin) through heat, and transfers the pattern to the surface of the polymer (resin) through pressure. It is a filmmaking technique. In such an imprinting method, it is essential to provide a predetermined amount of heat. If the time for which heat is applied to the polymer (resin) film precursor continues, that is, the exposure time to heat (or residence time for the pattern formation point) is long. In the case of loss, a so-called reflow phenomenon in which the surface molding state deteriorates or loses it may occur, such as returning the resin surface to the state before the pattern was formed. The inventor of the present application carefully studies these problems, and can appropriately adjust the exposure (or residence) time to the temperature gradient and heat related to pattern formation, and as a result, the present invention that can ensure the moldability of the resin and the uniformity of the pattern Invented a manufacturing method for application.

Specifically, the manufacturing method of the present application includes a step of manufacturing a film by passing a film precursor between a casting roll and a nip roll.

The casting roll and the nip roll may be rotated in different directions from each other, and may be spaced apart from each other at regular intervals. For example, the casting roll and the nip roll are mechanisms of a shape (eg, cylindrical) capable of rotational movement about a central axis, and when the nip roll rotates in a first direction, the casting roll is formed in the first direction and It can rotate in a different second direction. Since the two rolls are spaced apart from each other by a certain distance, when the film precursor is supplied between the rolls, the film precursor is pressed between the two rolls rotating in different directions and the thickness is equal to or less than the spaced distance. It can be molded into a surface pattern film having.

That is, the method comprises the steps of supplying a film precursor onto a casting roll; By moving the film precursor along the rotational direction of the casting roll so that the film precursor can pass through the gap between the nip roll and the casting roll having a pattern on the surface, a pattern corresponding to the pattern of the nip roll is formed on the surface of the film precursor It may include the step of forming in

In relation to the film forming as described above, the nip roll used in the manufacturing method of the present application has a surface pattern, and the surface temperature of the nip roll may be greater than or greater than the surface temperature of the casting roll. The film precursor is pressed between the nip roll and the casting roll while being conveyed in the rotational direction of the casting roll, and in the process, a pattern formed on the surface of the nip roll may be engraved on the surface of the film precursor. At this time, since the surface temperature of the casting roll is maintained at the same or lower temperature compared to the surface temperature of the nip roll having a pattern, it is adjusted to be suitable for pattern molding only at the pattern engraving point (refer to the dotted line box in FIG. 1 ) A high temperature temperature is applied to the film precursor, and after the film precursor moving along the rotational direction of the casting roll passes the pattern engraving point, the film precursor on which the pattern is formed is exposed only to the relatively low temperature of the casting roll and the ambient temperature. can be Therefore, the film precursor on which the pattern is formed can be cooled naturally, side reactions that may occur due to high temperature and crystallization or adhesion problems resulting therefrom can be suppressed, and reflow of the molded resin can also be prevented. .

In an example related to the present application, the surface temperature of the nip roll may be higher than the casting roll surface temperature. Specifically, as in the experiment to be described later, when the surface temperature of the nip roll is higher than the surface temperature of the casting roll, the pattern transfer effect may be better (see Examples 2 and 5).

In the present application, the film precursor on which the surface pattern is formed (or engraved) through the above process may be referred to as an unstretched film, an unstretched pattern film, or a casting pattern sheet.

In one example, the diameter of the nip roll may be less than or equal to the diameter of the casting roll. Specifically, the diameter of the nip roll may be smaller than the diameter of the casting roll. Through this configuration, the pattern-formed film precursor can be cooled naturally.

the surface of the nip roll The temperature may be determined in consideration of the melting point or glass transition temperature of the resin component used, or fairness. For example, the surface temperature of the nip roll may be in the range of 25 to 150 ℃. Specifically, the surface temperature of the nip roll is, for example, 30 ℃ or more, 35 ℃ or more, 40 ℃ or more, 45 ℃ or more, 50 ℃ or more, 55 ℃ or more, 60 ℃ or more, 65 ℃ or more, 70 ℃ or more, 75 ° C or higher, 80 ° C or higher, 85 ° C or higher, 90 ° C or higher, 95 ° C or higher, 100 ° C or higher, 105 ° C or higher, 110 ° C or higher, 115 ° C or higher, or 120 ° C or higher, the upper limit of which is, for example, 140 ℃ or lower, 135 °C or lower, 130 °C or lower, 125 °C or lower, 120 °C or lower, 115 °C or lower, 110 °C or lower, 105 °C or lower, 100 °C or lower, 95 °C or lower, or 90 °C or lower. If the surface temperature of the nip roll is lower than the above range, the pattern may not be sufficiently formed. In addition, the resin component, for example, the polyester resin has a higher degree of crystallinity as it is heated. If the degree of crystallinity is excessively high, breakage may occur in the stretching process, so it is advantageous to maintain a temperature not exceeding the above range. .

In one example, the difference between the surface temperature of the casting roll and the surface temperature of the nip roll may be in the range of 5 to 50 ℃. Specifically, the lower limit of the temperature difference may be, for example, 10 °C or higher, 15 °C or higher, 20 °C or higher, or 25 °C or higher, and the upper limit of the temperature difference is, for example, 45 °C or lower, 40 °C or lower, 35 °C or higher. ℃ or less, 30 ℃ or less, or 25 ℃ or less.

The surface temperature of the casting roll may be appropriately adjusted in consideration of the surface temperature of the above-described nip roll or the difference between the surface temperature of the casting roll surface and the surface temperature of the nip roll. For example, the surface temperature of the casting roll may be 20 ℃ or more. Specifically, the surface temperature of the casting roll is, for example, 25 ℃ or more, 30 ℃ or more, 35 ℃ or more, 40 ℃ or more, 45 ℃ or more, 50 ℃ or more, 55 ℃ or more, 60 ℃ or more, 65 ℃ or more, 70 °C or higher, 75 °C or higher, 80 °C or higher, 85 °C or higher, 90 °C or higher, 95 °C or higher, or 100 °C or higher. And, the upper limit of the surface temperature of the casting roll is, for example, 105 ℃ or less, 100 ℃ or less, 95 ℃ or less, 90 ℃ or less, 85 ℃ or less, 80 ℃ or less, 75 ℃ or less, 70 ℃ or less, 65 ℃ or less, or It may be below 60 °C.

The interval between the nip roll and the casting roll is not particularly limited, and may be appropriately adjusted in consideration of the thickness of the film to be manufactured. For example, the gap (gap) between the two rolls may be 10 μm or more, 50 μm or more, 100 μm or more, 150 μm or more, or 200 μm or more, and the upper limit thereof is, for example, 2,500 μm or less, It may be 2,000 μm or less, 1,500 μm or less, or 1,000 μm or less.

The material (or material) of the nip roll and the casting roll is not particularly limited. For example, each of the nip roll and the casting roll may include or be formed from a metal or a polymer.

With respect to pattern formation, the pressure applied to the imprint roll by the nip roll is such that the film precursor (which may be a melt, for example, as described below) can sufficiently penetrate into the concave-convex pattern on the surface of the nip roll. and it can be adjusted at a level that can give an appropriate level of thickness to the film on which the pattern is formed. For example, the pressure applied to the casting roll by the nip roll may be adjusted in the range of 1 to 100 kgf/cm ² . When the pressure is less than the above range, it may be difficult for the film precursor to penetrate into the pattern. And, when the pressure exceeds the above range, it may be an obstacle to uniformly control the thickness of the film precursor passing through the pattern engraving point. Specifically, the lower limit of the pressure is, for example, 5 kgf/cm ² or more, 10 kgf/cm ² or more, 15 kgf/cm ² or more, 20 kgf/cm ² or more, 25 kgf/cm ² or more, 30 kgf/ cm ² or more, 35 kgf/cm ² or more, 40 kgf/cm ² or more, 45 kgf/cm ² or more, or 50 kgf/cm ² or more, and the upper limit thereof is, for example, 95 kgf/cm ² or less, 90 kgf or more. /cm ² or less, 85 kgf/cm ² or less, 80 kgf/cm ² or less, 75 kgf/cm ² or less, 70 kgf/cm ² or less, 65 kgf/cm ² or less, 60 kgf/cm ² or less, 55 kgf/ cm ² or less or 50 kgf/cm ² or less.

The shape of the pattern formed on the surface of the nip roll is not particularly limited.

In one example, the nip roll may have a regular or irregular pattern. Accordingly, a film having a surface pattern corresponding to the surface pattern of the nip roll can be obtained.

In one example, the nip roll may have a concave-convex pattern on its surface. Specifically, the nip roll may have a pattern in which a concave portion and a convex portion are repeatedly formed on an outer peripheral surface thereof.

Although not particularly limited, the concave-convex pattern of the nip roll may have a recessed depth of 5 to 100 μm and a recessed period of 10 to 100 μm. In this case, the depth of the recess may mean a vertical distance from the outer peripheral surface of the nip roll to the deepest point of the recess. And, the period of the recess means a distance between any one point of an arbitrary recess and a corresponding point of another recess that is immediately adjacent thereto.

According to an embodiment of the present application, the outer circumferential concave-convex pattern of the nip roll has a lower limit of 10 μm or more, 15 μm or more, 20 μm or more, 25 μm or more, or 30 μm or more, and an upper limit of 50 μm or less, 45 μm or less. , 40 μm or less, 35 μm or less, 30 μm or less, 25 μm or less, or 20 μm or less. And, the outer peripheral surface uneven pattern of the nip roll has a lower limit of 10 μm or more, 15 μm or more, 20 μm or more, 25 μm or more, 30 μm or more, 35 μm or more, 40 μm or more, 45 μm or more, or 50 μm or more, The upper limit is 70 µm or less, 65 µm or less, 60 µm or less, 55 µm or less, 50 µm or less, 45 µm or less, 40 µm or less, 35 µm or less, 30 µm or less, 25 µm or less, or 20 µm or less. It can have sub-cycles.

In one example, the ratio (T:D) between the period of the recess (T) and the depth of the recess (D) is 1:0.1 to 1:2, or 1:0.1 to 1:1.5, or 1:0.15 to 1 :1, or 1:0.15 to 1:0.5. In the concave-convex pattern, when the depth (D) of the concave portion is excessively large based on the concave-convex period (T), it is difficult to obtain a uniform surface asperity because it is difficult for the melt of the resin composition to penetrate into the concave-convex pattern. Therefore, the ratio (T:D) is preferably adjusted to 1:2 or less. However, when the depth (D) of the recessed portion is too small based on the period (T), the height of the surface unevenness formed on the unstretched film is low, and the height of the surface unevenness is further increased through the stretching process for the unstretched film. It may be difficult to have an appropriate surface roughness as it is lowered. Therefore, the ratio (T:D) is preferably 1:0.1 or more.

In one example, the surface pattern of the nip roll may include an arc (arc) shape. Accordingly, on the film, a pattern having a circular cross section such as an arc can be formed.

In one example, the pattern on the surface of the nip roll may have a cross-sectional shape including one or more interior angles. Here, the inner angle means an angle formed in the cross section of the concave-convex pattern by connecting two or more straight lines. For example, when the interior angle is one, it means a triangular cross section, and when the interior angle is two, it means a rectangular cross section. Although not particularly limited, in consideration of fairness related to the roll, the concave-convex pattern may have a cross-sectional shape including 1 to 5 interior angles.

In one example, the concave-convex pattern formed on the outer peripheral surface of the imprint roll may have a concave portion in the form of a cone, a triangular pyramid, or a quadrangular pyramid.

In one example, the film precursor may be a melt or melt extrudate of the resin composition. At this time, the extruded shape is not particularly limited.

Depending on the viscosity of the melt of the resin composition, the density of the pattern, the process speed, etc., the degree to which the melt of the resin composition fills the outer peripheral surface pattern of the nip roll may vary. Considering this point, for example, the height of the convex portion among the irregularities of the pattern formed on the film may be equal to or smaller than the height of the convex portion among the irregularities of the nip roll surface pattern.

The type of the resin component contained in the resin composition is not particularly limited. For example, resins known to have moldability, such as an acrylic resin, a urethane resin, or a polyester resin, may be used as a component of the resin composition without limitation.

In one example, the resin component may be or include a polyester resin. The specific type of the polyester resin component is not particularly limited, but, for example, the resin component may be polyethylene terephthalate or polyethylene naphthalate, or a component including at least one of them.

In one example, the polyester resin may be obtained by polycondensation of an acid component containing dicarboxylic acid as a main component and a glycol component containing alkylene glycol as a main component. The dicarboxylic acid component is not particularly limited, but, for example, terephthalic acid or its alkyl ester or phenyl ester may be used as the dicarboxylic acid component. In addition, difunctional carboxylic acids or ester-forming derivatives thereof such as isophthalic acid, ethylparaben, adipic acid, sebacic acid, and 5-sodium sulfoisophthalic acid may be used as an additional acid component. The glycol component is also not particularly limited, but ethylene glycol may be used as the main glycol component. In addition, propylene glycol, neopentyl glycol, trimethylene glycol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,4-bisoxyethoxybenzene, bisphenol, polyoxyethylene glycol, etc. are ethylene glycol. Can be used with glycols.

In one example, the polyester resin is 50 mol% of a glycol component containing diethylene glycol and ethylene glycol in a molar ratio of 5: 5; and 50 mol% of an acid component containing terephthalic acid and sulfoterephthalic acid in a molar ratio of 8.5:1.5.

In one example, the polyester resin may have a weight average molecular weight within the range of 40,000 to 70,000 g/mol. When it has a weight average molecular weight in the above range, it may be advantageous for the prepared polyester film to have appropriate solvent resistance and mechanical properties. Specifically, the weight average molecular weight of the polyester resin may be 40,000 to 70,000 g/mol, or 45,000 to 65,000 g/mol, or 50,000 to 60,000 g/mol.

The weight average molecular weight means a weight average molecular weight in terms of polystyrene measured by the GPC method. In this regard, in the process of measuring the weight average molecular weight, a commonly known analyzer and a detector such as a differential refractive index detector and an analytical column may be used, and commonly applied temperature conditions, solvents, and flow rates may be used. can be applied.

For example, when measuring the molecular weight, the polymer resin is dissolved in tetrahydrofuran (THF) so as to have a concentration of 1.0 (w/w)% in THF (about 0.5 (w/w)% based on the solid content) to form 0.45 μm pores After filtration using a syringe filter of size size, 20 μl was injected into GPC, tetrahydrofuran (THF) was used for the mobile phase of GPC, and was introduced at a flow rate of 1.0 mL/min, and the column was Agilent PLgel 5 μm Guard (7.5 x 50 mm) and Agilent PLgel 5㎛ Mixed D (7.5 x 300 mm) are connected in series. As a detector, the Agilent 1260 Infinity ⅡSystem, RI Detector can be used to measure at 40℃. This is a polystyrene standard sample (STD A, B, C, D) in which polystyrene having various molecular weights is dissolved in tetrahydrofuran at a concentration of 0.1 (w/w)% as follows, filtered with a syringe filter of 0.45 μm pore size and then GPC The weight average molecular weight (Mw) value of the polymer resin can be obtained by using a calibration curve formed by injecting into the polymer resin.

STD A (Mp): 791,000 / 27,810 / 945

STD B (Mp): 282,000 / 10,700 / 580

STD C (Mp): 126,000 / 4,430 / 370

STD D (Mp): 51,200 / 1,920 / 162

In one example, the resin composition may further include an additive. The type of the additive is not particularly limited, but, for example, a known additive such as a pinning agent, an antistatic agent, a UV stabilizer, a waterproofing agent, a slip agent, or a heat stabilizer may be used. The additive may be added during polymerization of the resin, added during preparation of a master batch chip including a polyester resin, or added during preparation of the resin composition.

In one example, the resin composition may include organic and/or inorganic particles.

The type of organic particles is not particularly limited. For example, silicone resin, crosslinked divinylbenzene polymethacrylate, crosslinked polymethacrylate, crosslinked polystyrene resin, benzoguanamine-formaldehyde resin, benzoguanamine-melamine-formaldehyde resin or melamine-formaldehyde resin, etc. Organic particles formed of may be used.

The kind of inorganic particles is also not particularly limited. For example, inorganic particles such as calcium carbonate, titanium oxide, silica, kaolin or barium sulfate can be used. The particles may be added during polymerization of the resin, added during preparation of a master batch chip including a polyester resin, or added during preparation of the resin composition.

In one example, the particles may have a particle diameter in the range of 0.1 to 5 μm. The particle size refers to the particle size (D50) of the 50th size particle when the particle size is classified from 1 to 100. can

In one example, when the composition includes particles, the content may be within the range of 1 to 1,000 ppm based on the entire film finally manufactured. When the above range is satisfied, it is advantageous to secure appropriate fairness.

In one example, when the resin composition includes inorganic and/or organic particles, the film may have a binary surface structure. Specifically, the film has a relatively large size surface pattern structure formed while the pattern of the nip roll is transferred; and a surface uneven structure of a relatively small size formed by the particles at the same time. In this case, the particles may be distributed regularly or irregularly. Such a binary surface structure can further improve roll running properties and winding properties related to the production and handling of the film. Such a binary surface structure may be provided on one surface of the film (eg, the film surface to which the pattern is transferred by a nip roll) (see FIG. 4 ).

In one example, the melt or melt extrudate that is the film precursor may have a temperature in the range of 200 to 350 °C. That is, the resin composition may be heated by a melt extruder to form a melt or melt extrudate having a temperature of 200 to 350 °C. When the temperature of the molten extrudate is less than the above range, the processability is not good, and when the temperature exceeds the above range, the resin is denatured and the cooling efficiency may be poor.

In one example, the melt of the resin composition may be extruded through a T-die provided at one end of the melt extruder. The melt extruded from the T-die is fed onto a casting roll, then moved along the direction of rotation of the casting roll, and fed onto a nip roll having a pattern on its surface. That is, in the present application, since the residual heat when the melt is discharged from the extruder can be used for pattern formation, high energy efficiency can be secured. Furthermore, since the film precursor imprinted by the relatively high temperature nip roll may be cooled by the relatively low temperature of the casting roll and the ambient temperature after passing the pattern engraving point, disadvantages such as reflow after pattern molding is also suppressed.

In one example, the method may be performed in such a way that the melt obtained from one melt extruder is extruded through one T-die. The T-die may have one outlet through which the melt is extruded.

In one example, the method may be a method of providing a single-layer film having different surface roughness on both sides. In the present application, the single-layer film is a film that has not undergone a co-extrusion process, and may mean a film that does not have an interface due to co-extrusion. Specifically, in the prior art, co-extrusion was used to bond two or more films having different surface roughness to each other, but in the present application, the co-extrusion method may not be used. Specifically, in the film manufactured according to the present application, the pattern intended in relation to ensuring fairness is implemented only on the film side that was pressed by the nip roll pattern surface, and the surface opposite to the film pattern surface (contacting with the casting roll and pressing Since the high smoothness and low illuminance characteristics are realized in the surface of the present invention, there is no need to bond two or more films having different surface roughness using co-extrusion as in the prior art.

In one example, the method may further include stretching an unstretched film having a surface asperity. Although not particularly limited, the stretching may be uniaxial stretching or biaxial stretching. The uniaxial stretching direction may be performed, for example, in a machine direction (referred to as MD or longitudinal direction) or transverse direction (referred to as TD or transverse direction). In addition, the biaxial stretching may be, for example, sequential stretching in which stretching is performed in the transverse direction (TD) after stretching in the machine direction (MD) for the unstretched film on which the pattern is formed first, or in the machine direction (MD) It may be simultaneous stretching in which stretching is performed simultaneously in the transverse direction (TD).

In one example, the stretching may be performed by 2.0 times to 6.0 times with respect to the machine direction (MD) and/or the transverse direction (TD). Specifically, the uniaxial stretching may be performed at 2.0 times to 6.0 times in the machine direction (MD) or transverse direction (TD), and the biaxial stretching is performed at 2.0 times to 6.0 times in both the machine direction (MD) and transverse direction (TD). can be

The stretching may be performed at a temperature equal to or higher than the glass transition temperature of the resin component used, and at a temperature that can ensure an appropriate level of crystallinity so that fracture does not occur. For example, when a polyester resin is used, the lower limit of the stretching temperature may be 80 °C or more, 90 °C or more, 100 °C or more, or 110 °C or more, and the upper limit is, for example, 120 °C or less, 110 °C or less. , 100 ℃ or less or 90 ℃ or less.

In the case of stretching, the stretched film may have a reduced thickness and slightly change in the shape of the surface pattern when compared to the unstretched film. Referring to FIG. 2, when the longitudinal stretching as in FIG. 2(b) is performed on the unstretched film (casting sheet) having the surface pattern of FIG. 2(a), the height of the convex part is lowered and the period of the convex part increases, The thickness of the film may be reduced. In addition, when transverse stretching is additionally performed after longitudinal stretching, as shown in FIG. 2(c) , the height of the convex portions of the pattern may be lowered, and the thickness of the film may further decrease while the period of the convex portions is further increased. Fig. 3 schematically shows cross-sections of the unstretched film 100 (Fig. 3(a)) and the stretched film 105 (Fig. 3(b)).

As such, when the unstretched film having a pattern formed on the surface thereof is stretched, the period T of the convex portion among the irregularities forming the pattern may increase and the height H of the convex portion may decrease.

In one example, the method may further include a heat treatment step of heat-treating and relaxing the stretched film. The heat treatment step may be performed at a temperature of 100 to 300 °C. When the temperature of the heat treatment step is less than the above range, the degree of crystallinity of the resin is lowered, the mechanical properties may be lowered, or the residual elongation stress may not be sufficiently resolved, so that the thermal contraction rate may be increased. In addition, when the temperature of the heat treatment step exceeds the above range, the resin is thermally decomposed and mechanical properties are deteriorated, and the film is thermally deformed by high temperature, and thus the quality of the film may be deteriorated. At this time, the relaxation rate may be adjusted to 0.1 to 10% with respect to the machine direction and the transverse direction.

In another example related to the present application, the present application is an invention related to a film having a pattern on its surface. The film may provide excellent processability while having a low surface roughness.

The film may be manufactured by the above manufacturing method. Accordingly, the film has on one side the pattern transferred from the surface pattern of the nip roll. For example, the film may have a pattern on one surface of a shape and size corresponding to the nip roll surface pattern described above.

In one example, the stretched film may have a convex depth of 0.1 to 50 μm, or 0.2 to 20 μm, or 0.4 to 10 μm, on the surface of the stretched film. More specifically, the depth of the convex portion may be, for example, 1.0 μm or more, 1.1 μm or more, 1.2 μm or more, 1.3 μm or more, or 1.4 μm or more, and the upper limit thereof is, for example, 5.0 μm or less, 4 It may be less than or equal to 3 µm, or less than or equal to 2 µm. The depth of the convex portion means a portion formed corresponding to the main portion of the nip roll surface pattern, and may be mixed with the height of the convex portion.

In one example, the stretched film may have a concave-convex pattern having a convex period of 50 to 400 μm, or 50 to 300 μm, or 100 to 300 μm, or 150 to 250 μm. Specifically, the convex period may be 200 μm or more, 210 μm or more, 215 μm or more, or 220 μm or more.

In another example, in the unevenness of the pattern formed on the surface of the stretched film, the ratio (T:H) of the period (T) to the height of the convex portion (H) is 1:0.001 to 1:1, or 1:0.002 to 1 :0.5, or 1:0.002 to 1:0.1, or 1:0.002 to 1:0.05. When the ratio (T:H) is less than 1:0.001, it is difficult to secure sufficient surface roughness in relation to ensuring fairness. And, when the ratio (T:H) exceeds 1:1, since the surface roughness is too large, a problem of processability deterioration or processability deterioration related to any layer laminated on the pattern film prepared in actual use may occur. have.

In one example, the film has a surface pattern on one side, and the patterned surface has a centerline average roughness (Ra) of 1.0 nm or more or 5.0 nm or more, preferably 10 nm or more according to JIS B-0601. It may be a film with In addition, the upper limit of the centerline average roughness Ra may be, for example, 500 nm or less.

In one example, the coefficient of static friction (μS) of the one surface on which the pattern is formed of the film may be 0.40 or less. More specifically, the upper limit of the coefficient of static friction may be 0.35 or less or 0.30 or less, and the lower limit thereof may be, for example, 0.20 or more or 0.25 or more. The coefficient of static friction may be measured according to ASTM-D-1894.

In one example, the coefficient of kinetic friction (μD) of the one surface on which the pattern is formed of the film may be 0.40 or less. More specifically, the upper limit of the coefficient of kinetic friction may be 0.35 or less or 0.30 or less, and the lower limit thereof may be, for example, 0.20 or more or 0.25 or more. The coefficient of kinetic friction may be measured according to ASTM-D-1894.

In one example, the film may have a binary surface structure. Specifically, the film has a relatively large size surface pattern structure formed while the pattern of the nip roll is transferred; and a surface uneven structure of a relatively small size formed by the particles at the same time. In this case, the particles may be distributed regularly or irregularly. Such a binary surface structure can further improve the roll runability and winding property related to film production and handling thereof. Such a binary surface structure, for example, may be provided on one side of the film (eg, the film side to which the pattern is transferred by a nip roll).

In one example, the film may have a thickness of 10 to 250 μm, or 10 to 200 μm, or 20 to 150 μm, or 30 to 100 μm. Here, the thickness means a thickness measured including a convex portion in the surface unevenness formed on one surface of the polyester film.

In one example, the film may have a haze of 1.0% or less, or 0.1 to 1.0%, or 0.3 to 0.6%, and a total light transmittance of 90.0% or more, or 90.0 to 92.0%, or 90.0 to 91.0%. . In this case, haze and total light transmittance may be measured according to ASTM D-1003.

According to an embodiment of the present invention, a resin film capable of improving processability related to a roll while having a low surface roughness and a manufacturing method thereof are provided.

1 schematically shows a method for producing a film according to the present invention. In FIG. 1 , the dotted line box is a pattern engraving point.
Figure 2 shows the surface unevenness and the change of the cross-sectional shape according to the stretching during the manufacture of the film. Specifically, Fig. 2 (a) refers to an unstretched film (casting sheet) having a surface pattern, and Fig. 2 (b) shows that when the unstretched film is stretched in the longitudinal direction, the height of the convex part is lowered and the period of the convex part is It is schematically shown that the thickness of the film decreases with increasing. And, Fig. 2(c) schematically represents the cross-sectional shape of the surface asperity changed by the stretching in the case where the transverse stretching is additionally made after the longitudinal stretching.
4 is a cross-sectional view showing a surface structure of a film prepared according to an example of the present application. Specifically, Figure 4 (a) is a cross-section of the film produced by transferring the pattern of the nip roll, Figure 4 (b) is a cross-section of the film having a surface structure formed by particles together with the pattern transferred from the nip roll.

Hereinafter, the operation and effect of the invention will be described in more detail through specific examples of the invention. However, the embodiment is merely an example of the invention, and thereby the scope of the invention is not limited in any sense.

How to evaluate film properties

1. Crystallinity of unstretched film

The degree of crystallinity was calculated by the following formula using the measured density of the sample (measured at 25°C using a gradient tube). The values are shown in Table 1 above.

*Crystallinity

=

(100% amorphous density: 1.335, theoretical PET density of 100% crystals: 1.455)

2. Film thickness

Using an electric micrometer measuring device (Mahr, Millimar-1240, Germany), the thickness of five points (based on the convexity and convexity of the surface unevenness) was measured at intervals of 1 cm in the width direction of the film, and the average value of the values was calculated. . The values are shown in Table 2 above.

3. Roughness of the film (Ra)

Ra (center line average roughness) was measured according to the JIS B-0601 measurement method using a two-dimensional contact surface roughness meter (KOSAKA, SE-3300, Japan). The values are shown in Table 2 above.

4. Shape of surface irregularities

After cutting the film using a microtome device (LEICA, EM-UC7, Germany), the cross section was observed with an optical microscope (Olympus, BX51, Japan), and the line width of the surface irregularities and the depth of the recesses was measured. The values are shown in Table 2 above.

5. Haze and total light transmittance

Haze (Haze, %) and total light transmittance (T.t, %) of the film were measured using a Haze Meter (NIPPON DENSHOKU, NDH-5000, Japan) according to the measurement method of ASTM D-1003. The values are shown in Table 2 above.

6. Friction coefficient

Using a friction coefficient measuring device (Toyoseiki, TR-2, Japan), the static friction coefficient (μS) and the dynamic friction coefficient (μD) of the film surface in contact with the nip roll were measured according to the measurement method of ASTM-D1894. The values are shown in Table 2 above.

7. Driving

The drivability was evaluated according to the following criteria with the value of the dynamic friction coefficient. The values are shown in Table 2 above.

*Very good (◎) - Dynamic friction coefficient less than 0.35

*Good (○) - Dynamic friction coefficient 0.35~0.40

*Bad (X) - Dynamic friction coefficient greater than 0.40

8. Stretching Fairness

Stretching fairness was evaluated based on whether fracture occurred in the stretching process of the film. The values are shown in Table 2 above.

* No breakage: X

* Fracture occurs: O

Examples and Comparative Examples

Example 1

A polyester resin was obtained by polycondensing 50 mol% of a glycol component containing diethylene glycol and ethylene glycol in a molar ratio of 5: 5, and an acid component containing 50 mol% of an acid component containing terephthalic acid and sulfoterephthalic acid in a molar ratio of 8.5: 1.5. .

The obtained polyester resin was put into a melt extruder to form a melt (intrinsic viscosity IV of about 0.63) at about 300°C. A pattern was formed on one surface of the unstretched film while transferring the prepared melt in the same process as in FIG. 1 .

Specifically, the melt feeds the melt onto a casting roll while continuously extruding through a T-die, and the melt passes through a gap between the casting roll (without a surface pattern) and a nip roll (with a surface pattern) While doing so, a pattern corresponding to the concave-convex pattern of the nip roll was prepared on one surface of the unstretched film (see FIG. 1).

At this time, the surface temperature of the nip roll was maintained at about 80 ℃, the surface temperature of the casting roll was maintained at about 60 ℃, and the pressure applied to the casting roll by the nip roll was set to about 50 kgf/cm ² did. In this case, as the nip roll, a concave-convex pattern having a concave portion period T of 50 μm and a recess depth D of 20 μm was used on the surface thereof. The concave portion has a conical shape in which a vertex is directed toward the center of the imprint roll.

Thereafter, the unstretched film is transferred to a stretching process under conditions having a temperature of 90° C. or higher than the glass transition temperature (Tg) of the polyester resin, and is stretched 3.5 times in the machine direction (MD) at 95° C. and in the transverse direction (TD) was stretched 4.0 times.

Finally, after the stretching process, the stretched film was heat-treated at 230° C. for 10 seconds to obtain a polyester film.

Examples 2 to 4, and Comparative Examples 1 to 3

A polyester film having a pattern was obtained in the same manner as in Example 1, except that the pattern formation conditions and stretching conditions were changed as shown in Table 1 below.

Table 1 shows the comparison of the process conditions of Examples and Comparative Examples. In Table 1, the crystallinity of the unstretched film is as follows.

nip roll (imprint roll) casting roll stretch waist
depth
(μm) Cycle
(μm) temperature
(℃) temperature
(℃) MD direction
(stretch
magnification) TD
direction
(stretch
magnification) total draw ratio
(MD x TD) unstretched
film
crystallinity
(%) Example 1 20 50 80 60 3.5 4 14 4.2 Example 2 10 50 80 50 3.5 4 14 4.1 Example 3 10 50 70 50 3.5 4 14 4.1 Example 4 20 50 60 50 3.5 4 14 4.2 Example 5 10 50 80 80 3.5 4 14 4.6 Comparative Example 1 0 0 20 20 3.5 4 14 4.0 Comparative Example 2 0 0 80 60 3.5 4 14 4.1 Comparative Example 3 0 0 80 60 3.5 4 14 4.0

Ra (nm) * surface unevenness coefficient of friction thickness
(μm) Out In iron height
(μm) Cycle
(μm) Haze
(%) Tt
(%) μS μD drivability stretch
fairness
(break) Example 1 30.2 19.4 0.5 1.3 215.7 0.5 90.2 0.34 0.32 ◎ X Example 2 31.4 15.6 0.6 1.2 227.1 0.6 90.4 0.35 0.33 ◎ X Example 3 29.9 14.8 0.5 1.1 228.6 0.4 90.2 0.34 0.33 ◎ X Example 4 32.2 10.7 0.5 0.8 225.3 0.3 90.3 0.35 0.34 ◎ X Example 5 30.1 9.8 0.5 0.7 212.3 0.3 90.2 0.35 0.34 ◎ X Comparative Example 1 30.5 0.5 0.5 0 0 0.6 90.3 0.45 0.42 X X Comparative Example 2 31.8 0.5 0.5 0 0 0.5 90.5 0.44 0.41 X X Comparative Example 3 29.7 0.5 0.5 0 0 0.6 90.2 0.44 0.42 X X With respect to *Ra, out means the Ra value of the surface of the film on which the pattern is formed in contact with the nip roll surface, and In means the Ra value of the film surface not in contact with the nip roll surface.

Referring to Table 2, the films of Examples exhibited higher surface roughness values compared to the films of Comparative Examples 1 to 3 that do not have surface irregularities, and exhibited excellent running properties without breakage in the stretching process. Specifically, it was confirmed that the films of Comparative Examples 1 to 3, which do not have surface irregularities, have low surface roughness compared to the films of Examples and thus have poor running properties.

And, comparing Example 2 and Example 5, it can be confirmed that it is more preferable to control the surface temperature of the nip roll to be higher than the surface temperature of the casting roll. Specifically, Example 2 is a case where the surface temperature of the nip roll is set higher than the surface temperature of the casting roll, and Example 5 is a case where the surface temperature of the nip roll is the same as the surface temperature of the casting roll, Example 5, it was confirmed that Ra and the height of the surface convex part were relatively low. The difference in Ra (reduced by about 37% from 15.6 nm to 9.8 nm) and the difference in the height of the surface convex portion (reduced by about 42% from 1.2 µm to 0.7 µm) between Examples 2 and 5 shows the reduction ratio as %. Considering this, it can be seen as a significant level. This is because, in Example 5, the reflow phenomenon occurs more strongly in Example 5 compared to Example 2 because the temperature of the casting roll having a large contact area is at the same level as that of the nip roll providing the surface pattern.

10: T-die
20: casting roll
30: nip roll
40: film precursor (eg extrudate)
100: unstretched film
105: stretched film

Claims (15)

Rotating in different directions and passing a film precursor between a casting roll and a nip roll spaced apart at regular intervals to prepare an unstretched film,
The nip roll has a surface pattern,
The surface temperature of the nip roll is greater than or equal to the surface temperature of the casting roll,
A method for producing a film having a surface pattern.
The method of claim 1,
The surface temperature of the nip roll is in the range of 25 to 150 ℃,
A method for producing a film having a surface pattern.
3. The method of claim 2,
The difference between the surface temperature of the casting roll and the surface temperature of the nip roll is in the range of 5 to 50 ℃,
A method for producing a film having a surface pattern.
The method of claim 1,
The diameter of the nip roll is less than or equal to the diameter of the casting roll,
A method for producing a film having a surface pattern.
The method of claim 1,
The film precursor supplied on the casting roll is a melt or melt extrudate of a resin composition having a temperature of 200 to 350 °C,
A method for producing a film having a surface pattern.
The method of claim 1,
The nip roll has a regular or irregular irregular pattern,
A method for producing a film having a surface pattern.
The method of claim 1,
The concave-convex pattern of the nip roll has a recessed portion depth of 5 to 100 μm and a recessed period of 10 to 100 μm,
A method for producing a film having a surface pattern.
7. The method of claim 6,
The concave-convex pattern has a cross-sectional shape including an arc or a cross-sectional shape including one or more interior angles,
A method for producing a film having a surface pattern.
The method of claim 1,
Further comprising the step of stretching the unstretched film,
A method for producing a film having a surface pattern.
10. The method of claim 9,
performing uniaxial or biaxial stretching at a ratio of 2.0 to 6.0 times,
A method for producing a film having a surface pattern.
6. The method of claim 5,
The resin composition comprises at least one of organic particles and inorganic particles,
A method for producing a film having a surface pattern.
12. The method of claim 11,
The method includes a surface pattern structure formed while the pattern of the nip roll is transferred; And to prepare a film having a surface uneven structure formed by the particles,
A method for producing a film having a surface pattern.
prepared by the method according to claim 1,
Having a pattern transferred from the surface pattern of the nip roll on one surface,
The surface on which the pattern is formed has a centerline average roughness (Ra) of 1.0 to 500 nm according to JIS B-0601,
film.
14. The method of claim 13,
The surface on which the pattern is formed has a coefficient of static friction (μS) and a coefficient of kinetic friction (μD) according to ASTM-D1894 of 0.40 or less, respectively,
film.
14. The method of claim 13,
The surface on which the pattern is formed is a surface pattern structure formed while the pattern of the nip roll is transferred; And having a surface uneven structure formed by the particles,
film.

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