KR20220108412A - Polyester film structure - Google Patents

Abstract

A polyester film structure according to exemplary embodiments comprises: a polyester resin layer comprising a first surface and a second surface facing each other; and organic particles dispersed in the polyester resin layer. The second surface corresponds to a release coating surface and an indentation modulus measured by a nanoindenter on the second surface is less than 4 GPa. The polyester film structure can be used as a release film substrate for a green sheet molding process to improve process stability and reliability.

Description

Polyester film structure {POLYESTER FILM STRUCTURE}

The present invention relates to a polyester film structure. More specifically, it relates to a polyester film structure comprising a resin layer and particles dispersed in the resin layer.

In a manufacturing process of an electric device such as a multi-layered ceramic capacitor (MLCC), a release film may be used as a carrier film for an intermediate process such as a thermal process. For example, a firing process and/or a molding process may be performed while a laminate including a ceramic layer is moved on the release film in a green sheet state before firing.

For example, a release film including a polyester substrate may be used as the carrier film. It is preferable that the release film is designed so as not to cause physical and mechanical deformation to the green sheet during the process while being easily peeled off from the green sheet on which the molding process has been performed.

Meanwhile, as the size of the MLCC has recently decreased, the thickness of the green sheet is also getting thinner. Accordingly, the surface roughness of the polyester substrate may be easily transferred to the green sheet to cause deformation. However, when the surface roughness is excessively reduced, process easiness may be deteriorated such as blocking phenomenon.

Therefore, it is necessary to design a release film capable of improving the reliability of a process target such as a green sheet while reducing process defects.

For example, Korean Patent No. 10-1976118, etc. discloses a release film for manufacturing a green sheet.

Korean Patent Publication No. 10-1976118

One object of the present invention is to provide a polyester release film structure that provides improved mechanical reliability and process stability.

The polyester film structure according to exemplary embodiments includes a polyester resin layer including a first surface and a second surface facing each other and organic particles dispersed in the polyester resin layer. The second surface corresponds to the release coating surface, and the indentation modulus measured by the nano-indenter on the second surface is less than 4 GPa.

In some embodiments, the polyester resin layer may include a first resin layer including the first surface and a second resin layer including the second surface. The organic particles may include first organic particles dispersed in the first resin layer and second organic particles dispersed in the second resin layer.

In some embodiments, the thickness of the second resin layer may be 10 μm or more.

In some embodiments, the first organic particle may have a larger particle size than the second organic particle.

In some embodiments, a content of the first organic particles in the first resin layer may be greater than a content of the second organic particles in the second resin layer.

In some embodiments, the content of the first organic particles in the first resin layer may be 0.4 to 1% by weight, and the content of the second organic particles in the second resin layer may be 0.1 to 0.3% by weight. .

In some embodiments, a difference between the centerline average roughness Ra on the first surface and the second surface may be 5 nm or more.

In some embodiments, a difference between the centerline average roughness Ra on the first surface and the second surface may be 5 to 20 nm.

In some embodiments, a difference between the maximum peak height surface roughness (Rp) of the first surface and the second surface may be 70 nm or more.

In some embodiments, the indentation modulus measured by the nano-indenter on the second surface may be greater than or equal to 2 GPa and less than 4 GPa.

According to the above-described exemplary embodiments, it is possible to suppress the deformation due to the pressing to the green sheet by adjusting the indentation modulus of the release surface of the polyester film structure. The polyester film structure may use organic particles including, for example, a crosslinked polystyrene resin as particles for forming surface roughness. Accordingly, compared to the case of using inorganic particles, it is possible to more easily implement low surface roughness. In addition, the surface roughness can be relatively increased as a process running surface. Therefore, winding stability and process stability can be improved together.

According to exemplary embodiments, the above-described low surface roughness/process stability can be implemented together by adjusting the difference in surface roughness between the release coating surface and the process running surface to a predetermined range using the organic particles.

1 is a schematic cross-sectional view showing a polyester film structure according to exemplary embodiments.

Exemplary embodiments disclosed in the present application provide a polyester release film structure including a polyester resin layer and organic particles. However, since the present invention can have various changes and can have various forms, specific embodiments are illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to the specific disclosed form, it should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having meanings consistent with the context of the related art, and unless explicitly defined in the present application, they are not to be interpreted in an ideal or excessively formal meaning. .

1 is a schematic cross-sectional view showing a polyester release film structure according to exemplary embodiments.

Referring to FIG. 1 , a polyester film structure 100 (hereinafter, may be abbreviated as a film structure) according to exemplary embodiments may include a resin layer and organic particles dispersed in the resin layer.

In some embodiments, the film structure 100 may have a multilayer structure including two or more layers. For example, as shown in FIG. 1 , the film structure 100 may include a first layer 110 and a second layer 120 stacked on the first layer 110 .

The first layer 110 may include a first resin layer 112 and first organic particles 114 dispersed in the first resin layer 112 . The second layer 120 may include a second resin layer 122 and second organic particles 124 dispersed in the second resin layer 122 .

The film structure 100 may include a first surface 100a and a second surface 100b. For example, the first surface 100a and the second surface 100b may correspond to the lower surface and the upper surface of the film structure 100 , respectively.

According to exemplary embodiments, the second surface 100b may correspond to a release coating surface. For example, a release coating layer such as a silicon release layer may be formed on the second surface 100b and a multilayer ceramic capacitor (MLCC) green sheet may be laminated. The second surface 100b may be provided by the top surface of the second layer 120 .

The first surface 100a may be a process running surface that is moved in contact with the transfer equipment of the green sheet firing/forming equipment. The first surface 100a may be provided by the bottom surface of the first layer 110 .

The first and second resin layers 112 and 122 may include a polyester resin. The polyester resin may be prepared through polycondensation of an aromatic dicarboxylic acid-based compound and a diol-based compound.

Examples of the aromatic dicarboxylic acid-based compound include dimethyl terephthalate, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, cyclobutanedicarboxylic acid, cyclohexanedicarboxylic acid, 5-sulfoisophthalic acid, 5-sulfof lopoxyisophthalic acid, diphenyldicarboxylic acid, diphenoxyalkanedicarboxylic acid, adipic acid, sebacic acid, and the like. Preferably, dimethyl terephthalate or terephthalic acid may be used.

Examples of the diol-based compound include an alkylene glycol-based compound such as ethylene glycol, 1,3-propanediol, and 1,4-butanediol, 2,2-dimethyl-1,3-propanediol, and 1,4-cyclohexanediol. methanol and the like. Preferably, ethylene glycol may be used.

According to exemplary embodiments, the first and second organic particles 114 and 124 may include crosslinked organic resin particles, for example, silicone resin, crosslinked divinylbenzene polymethacrylate, and crosslinked polymethacrylate. Acrylate, crosslinked polystyrene resin, benzoguanamine-formaldehyde resin, benzoguanamine-melamine-formaldehyde resin, melamine-formaldehyde resin, etc. can be used.

In a preferred embodiment, the first and second organic particles 114 and 124 may include cross-linked polystyrene (PS) resin. For example, the first and second organic particles 114 and 124 may include spherical polystyrene resin particles.

The first and second organic particles 114 and 124 may be added in the form of a slurry dispersed in a diol-based compound such as ethylene glycol, for example, when the polyester resin is synthesized.

In some embodiments, the indentation modulus measured using the nano-indenter on the release coated side or the second side 100b may be less than 4 GPa. In the above range, the strength of pressing through the second surface 100b is relieved, so that stress on the green sheet and occurrence of pressing can be effectively suppressed.

Preferably, the indentation modulus measured using the nano-indenter on the release coated surface or the second surface 100b may be 2 GPa or more and less than 4 GPa, and more preferably 3 GPa or more and less than 4 GPa. Within the above range, it is possible to prevent deformation due to pressing of the green sheet without degrading process stability and mechanical stability through the film structure 100 .

In some embodiments, the thickness of the second layer 120 may be about 10 μm or more. In this case, while the second layer 120 is provided as a release layer, for example, it may be sufficiently provided as an elastic layer. For example, the thickness of the second layer 120 may range from about 10 to 40 μm.

According to example embodiments, the particle size (eg, D50) of the first organic particles 114 may be greater than or equal to the particle size (eg, D50) of the second organic particles 124 . Preferably, the particle size of the first organic particles 114 may be greater than that of the second organic particles 124 .

In some embodiments, the particle size of the first organic particles 114 may be about 0.3 to 1.5 μm. Preferably, the particle size of the first organic particles 114 may be about 0.3 to 1 μm, more preferably about 0.3 to 0.6 μm.

In some embodiments, the particle size of the second organic particles 124 may be about 0.05 to 0.3 μm. Preferably, the particle size of the second organic particles 124 may be about 0.1 to 0.3 μm.

According to example embodiments, the content of the first organic particles 114 in the first layer 110 may be greater than or equal to the content of the second organic particles 124 in the second layer 120 . Preferably, the content of the first organic particles 114 may be greater than the content of the second organic particles 124 .

For example, the content of the organic particles 114 and 124 in the film structure 100 may be about 0.1 to 1% by weight. In an embodiment, the content of the first organic particles 114 in the first layer 110 may be about 0.4 to 1% by weight, and the content of the second organic particles 124 in the second layer 120 is It may be about 0.1 to 0.3% by weight.

According to exemplary embodiments, the first organic particle 114 has a larger particle size than the second organic particle 124 , or the content in the first layer 110 of the first organic particle 114 is the second organic particle size. It may be greater than the content in the second layer 120 of the particles 124 . Accordingly, by relatively increasing the surface roughness on the first surface 100a, winding stability and anti-blocking properties can be improved.

Surface roughness may be implemented on the surface (the first surface 100a and the second surface 100b) of the film structure 100 by the organic particles 114 and 124 included in the resin layers 112 and 122. have. As described above, according to exemplary embodiments, organic particles 114 and 124 including, for example, cross-linked polystyrene resin may be used as particles for forming surface roughness.

Accordingly, for example, compared to the case of using inorganic particles such as silica (SiO ₂ ), titania (TiO ₂ ), zeolite, barium sulfate, calcium carbonate, etc., it is possible to more easily implement or maintain a low surface roughness. Therefore, for example, even when the thickness of the MLCC green sheet laminated on the second surface 100b, which is the release coating surface, becomes thinner, it is possible to suppress process defects due to transfer of surface roughness.

In addition, since the organic particles 114 and 124 having relatively low surface hardness and elastic properties are used, stress transmission to the green sheet can be suppressed even with the same surface roughness. Accordingly, for example, it may be possible to secure a margin for relatively increasing the surface roughness of the first surface 100a corresponding to the process running surface.

Accordingly, process drivability and process control characteristics through the first surface 100a may be secured. In addition, when the film structure 100 is supplied in a wound state, winding stability and anti-blocking properties may be improved through the first surface 100a having relatively high roughness.

In addition, the first and second organic particles 114 and 124 such as polystyrene resin particles may have higher affinity with the organic compound for forming the resin layers 112 and 122 than the inorganic particles. Accordingly, the organic particles 114 and 124 are more evenly dispersed in the resin layers 112 and 122 , so that the uniformity of the surface roughness can also be improved.

In some embodiments, the second organic particles 124 included in the second layer 120 may include a plurality of particles having different particle sizes. The first organic particles 114 included in the first layer 110 may include a plurality of particles having different particle sizes. Accordingly, it is possible to further improve the dispersibility of the organic particles in each layer, thereby further improving the uniformity of the surface roughness.

In some embodiments, the second layer 120 may not include substantially the aforementioned inorganic particles. Also, the first layer 110 may not substantially include the aforementioned inorganic particles.

In an embodiment, the second layer 120 and/or the first layer 110 further include a trace amount of inorganic particles within a range that does not impair the effect through the use of the organic particles 114 and 124 described above. It may also be used (for example, the content of 0.05% by weight or less).

According to exemplary embodiments, the difference between the centerline average roughness Ra of the first surface 100a and the second surface 100b of the film structure 100 may be 5 nm or more. In the above range, it is possible to secure sufficient process stability and anti-blocking properties through the process running surface while maintaining low surface roughness on the release coating surface.

In one embodiment, the difference between the centerline average roughness Ra of the first surface 100a and the second surface 100b of the film structure 100 may be in the range of 5 to 20 nm, preferably 5 to 15 nm.

For example, the average roughness Ra of the center line of the second surface 100b may be in a range of about 4 to 10 nm. The centerline average roughness Ra of the first surface 100a may be in a range of about 10 to 25 nm, preferably about 10 to 20 nm.

In some embodiments, the maximum peak height surface roughness Rp of the first surface 100a may be greater than the maximum peak height surface roughness Rp of the second surface 100b. In some embodiments, the difference between the maximum peak height surface roughness Rp of the first surface 100a and the second surface 100b may be about 70 nm or more. Preferably, the difference between the maximum peak height surface roughness (Rp) of the first surface 100a and the second surface 100b may be in the range of about 70 to 180 nm.

For example, it is possible to secure sufficient process stability and anti-blocking properties through the process running surface while maintaining a low surface roughness on the release coating surface within the surface roughness range.

For example, the maximum peak height surface roughness Rp of the first surface 100a may be in the range of about 130 to 250 nm. The maximum peak height surface roughness Rp of the second surface 100b may be in the range of about 40 to 70 nm.

For example, the film structure 100 may be manufactured through co-extrusion. For example, the polyester resin in which organic particles are dispersed for forming the first layer 110 and the second layer 120 is dried, melted, and extruded, respectively, and then passed through a die such as a multi-manifold die and a feed block die. Polyester resins can be joined. Thereafter, a sheet may be formed through a casting process, and the film structure 100 may be obtained through a stretching process.

As described above, the film structure 100 according to the exemplary embodiments may be provided as a release film substrate for the green sheet forming process. For example, a release film may be formed through thermal drying by coating a solvent-type silicone resin on the second surface 100b of the film structure 100 .

Hereinafter, preferred embodiments are presented to help the understanding of the present invention, but these examples are merely illustrative of the present invention and do not limit the appended claims, and are within the scope and spirit of the present invention. It is obvious to those skilled in the art that various changes and modifications are possible, and it is natural that such variations and modifications fall within the scope of the appended claims.

Examples and Comparative Examples

Example 1

A polystyrene/ethylene glycol first slurry having a concentration of 20 wt% was prepared by dispersing polystyrene (PS) particles having an average particle diameter of 0.1 μm in ethylene glycol. In addition, polystyrene particles having an average particle diameter of 0.5 μm were dispersed, respectively, to prepare a polystyrene/ethylene glycol second slurry having a concentration of 20 wt%.

Dimethyl terephthalate and the slurry were mixed in an equivalent ratio of 1:2, respectively, and then a conventional transesterification catalyst was added to carry out the transesterification reaction. A polycondensation reaction was completed by adding a conventional polycondensation catalyst to prepare a polyester mixed resin having an intrinsic viscosity of 0.62 dl/gr. As a result, a first polyester mixed resin and a second polyester mixed resin each containing polystyrene particles having particle sizes of 0.1 μm and 0.5 μm were prepared.

The polyester mixed resins prepared above were passed through each drying, melting, and extrusion process according to the coextrusion polyester film manufacturing method, and then joined through a feed block die, cast at room temperature on an abrasive drum, and molded into a sheet.

A polyester base film having a thickness of 30 μm was prepared by stretching the molded sheet at a longitudinal stretch ratio of 3.4 times and a transverse stretch ratio of 3.5 times while heating at 80°C. The first layer formed through the first polyester mixed resin and the second layer formed through the second polyester mixed resin had a thickness of 15 μm, respectively.

Examples 2 to 7

A polyester base film was prepared in the same manner as in Example 1, except that the particle composition (particle diameter, content, etc.) was changed as described in Table 1.

Comparative Example 1

A polyester base film was prepared in the same manner as in Example 1, except that silica particles (2 types of particle diameters of 0.3 μm and 0.5 μm, respectively) were used as particles included in the resin layer.

Comparative Example 2

A polyester base film was prepared in the same manner as in Example 1, except that the particle composition (particle diameter, content, etc.) of the polystyrene particles was changed as described in Table 1.

Experimental example

(1) Measurement of surface roughness (Ra, Rp)

The surface roughness of the first side and the second side of the polyester base film was measured using a three-dimensional surface roughness meter. Specifically, the surface roughness meter was measured by the JIS-B0601 measurement method using KOSAKA's SE-3500.

(2) Measurement of coefficient of friction

According to ASTM D 1894 standard, after sampling the polyester base film at 11 cm in width direction and 20 cm in length direction, the coefficient of friction between the first and second surfaces was measured using a TOYOSEIKI A281300803 instrument. The load was 200 g, and the measurement speed was 50 mm/min, which was measured three times per sample and the average value was used.

(3) Indentation modulus measurement

The indentation modulus of the second surface was measured according to the ISO 14577 standard using a diamond-made nano indenter (berkovich tip, angle: 65.3 ^o ) of Probes (Note).

(4) Number of green sheet pinholes/green sheet deformation

5 wt% of a curable silicone resin (manufactured by Dow Corning, SYL-OFF 7920), 2 wt% of a curing agent (manufactured by Dow Corning, SYLOFF7923), and distilled water 93 on the first side of the polyester base film prepared according to Examples and Comparative Examples A release agent composed of wt% was applied and dried at 200° C. for 20 seconds to form a release layer.

After that, the ceramic slurry is applied on the release layer through a slot die coater, and the number of pinholes generated while forming the 100 m length by forming the ceramic slurry on a 200 mm wide film is observed, and 1 point (no pinhole) to 5 points ( A number of pinholes occurred) and a score was given.

In addition, after forming the ceramic slurry, the dried green sheet was peeled off to a size of width X length (100 mm X 100 mm), and when the state of the surface was observed with an optical microscope magnified by 40 times, the occurrence of irregularities was observed to evaluate the deformation of the green sheet. Specifically, a score was given between 1 point (no irregularities) and 5 points (many irregularities observed).

The evaluation results are shown together in Table 1, Table 2, and Table 3 below.

division Example 1 Example 2 Example 3 Example 4 particle
Furtherance 2nd side
(a variant
coated side) ingredient PS PS PS PS Particle size (D50) 0.1㎛ 0.1㎛ 0.3㎛ 0.3㎛ 0.1㎛ Content (wt%) 0.16% 0.08% 0.08% 0.16% 0.50% side 1
(process
running surface) ingredient PS PS PS PS Particle size (D50) 0.5㎛ 0.3㎛ 0.5㎛ 0.3㎛ 0.5㎛ Content (wt%) 0.40% 0.20% 0.20% 0.40% 0.50% surface
illuminance 2nd side
(a variant
coated side) Ra (nm) 4.1 5.1 6 8 Rp (nm) 45 57 60 65 side 1
(process
running surface) Ra (nm) 16 14 11 18 Rp (nm) 220 210 130 230 coefficient of friction Static friction/dynamic friction 0.19/0.25 0.18/0.22 0.17/0.20 0.21/0.27 Second modulus of elasticity (GPa) 3.4 3.3 3.3 3.0 ceramic sheet strain One One One One Frequency of pinhole occurrence One One One 2

division Example 5 Example 6 Example 7 particle
Furtherance 2nd side
(a variant
coated side) ingredient PS PS PS Particle size (D50) 0.1㎛ 0.3㎛ 0.5㎛ Content (wt%) 0.60% 0.60% 0.60% side 1
(process
running surface) ingredient PS PS PS Particle size (D50) 0.5㎛ 0.6㎛ 0.5㎛ Content (wt%) 0.60% 0.60% 0.8% surface
illuminance 2nd side
(a variant
coated side) Ra (nm) 9 9.5 9.4 Rp (nm) 68 71 70 side 1
(process
running surface) Ra (nm) 20 23 22 Rp (nm) 250 264 230 coefficient of friction Static friction/dynamic friction 0.20/0.30 0.19/0.25 0.23/0.32 Second modulus of elasticity (GPa) 2.5 2.2 1.8 ceramic sheet strain 2 2 3 Frequency of pinhole occurrence 2 2 2

division Comparative Example 1 Comparative Example 2 particle
Furtherance 2nd side
(a variant
coated side) ingredient PS SiO ₂ SiO ₂ Particle size (D50) 0.1㎛ 0.3㎛ 0.3㎛ Content (wt%) 0.08% 0.08% 0.10% side 1
(process
running surface) ingredient PS SiO ₂ Particle size (D50) 0.3㎛ 0.5㎛ 0.5㎛ Content (wt%) 0.20% 0.20% 0.20% surface
illuminance 2nd side
(a variant
coated side) Ra (nm) 4.8 5.8 Rp (nm) 61 69 side 1
(process
running surface) Ra (nm) 14 10 Rp (nm) 210 180 coefficient of friction Static friction/dynamic friction 0.18/0.23 0.16/0.19 Second modulus of elasticity (GPa) 4.7 4.9 ceramic sheet strain 4 4 Frequency of pinhole occurrence 2 3

Referring to Tables 1 to 3, in the case of the embodiments in which the indentation modulus is less than 4 GPa, preferably 3 GPa or more and less than 4 GPa, stable green sheet molding processability is secured while suppressing or reducing the surface deformation of the green sheet became

100: polyester film structure 110: first layer
112: first resin layer 114: first organic particles
120: second layer 122: second resin layer
124: second organic particle

Claims (10)

A polyester resin layer comprising a first surface and a second surface facing each other; and
Including organic particles dispersed in the polyester resin layer,
The second surface corresponds to a release coating surface, and the indentation modulus measured by a nano-indenter on the second surface is less than 4 GPa, a polyester film structure. The method according to claim 1, wherein the polyester resin layer comprises a first resin layer including the first surface and a second resin layer including the second surface,
The organic particles are a polyester film structure comprising a first organic particle dispersed in the first resin layer and a second organic particle dispersed in the second resin layer. The method according to claim 2, The thickness of the second resin layer is 10㎛ or more, polyester film structure. The polyester film structure of claim 2, wherein the first organic particles have a larger particle size than the second organic particles. The polyester film structure of claim 2, wherein the content of the first organic particles in the first resin layer is greater than the content of the second organic particles in the second resin layer. The method according to claim 5, The content of the first organic particles in the first resin layer is 0.4 to 1% by weight, the content of the second organic particles in the second resin layer is 0.1 to 0.3% by weight, the polyester film struct. The method according to claim 1, The difference between the center line average roughness (Ra) on the first surface and the second surface is 5 nm or more, the polyester film structure. The method according to claim 7, The difference between the centerline average roughness (Ra) on the first surface and the second surface is 5 to 20nm, the polyester film structure. The method according to claim 1, wherein the maximum peak height surface roughness (Rp) difference between the first surface and the second surface is 70nm or more. polyester film structure The method according to claim 1, wherein the indentation modulus measured by the nano-indenter on the second surface is 2 GPa or more and less than 4 GPa, the polyester film structure.

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