KR20140002552A - Manufacturing method of polyester film - Google Patents

Abstract

The present invention relates to a method for manufacturing a polyester film; more specifically relating to the polyester film to apply a release film manufacturing a ceramic green sheet when manufacturing a multi layer ceramic condenser; relating to a polyester film having a uniform film thickness not to cause a variation in the green sheet thickness of a thin film and manufacturing method. [Reference numerals] (AA) Left; (BB) Middle; (CC) Right; (DD,EE,FF) Average; (GG) Whole average

Description

Manufacturing Method of Polyester Film {MANUFACTURING METHOD OF POLYESTER FILM}

The present invention relates to a method for producing a polyester film, and more particularly, to a polyester film applied to a release film for producing a ceramic green sheet when manufacturing a multilayer ceramic capacitor, and does not give a variation in the thickness of the green sheet of a thin film. The present invention relates to a polyester film having a uniform film thickness and a manufacturing method.

Polyester film has excellent stability of physical properties over a wide temperature range from low temperature to high temperature, excellent chemical resistance compared to other polymer resins, and good mechanical strength, surface properties and thickness uniformity. It has excellent applicability in process conditions, so it is applied to capacitors, photo films, labels, pressure-sensitive tapes, decorative laminates, transfer tapes, polarizing plates, and green sheets for ceramic releasing. The trend is increasing day by day.

The polyester film corresponding to the present invention is used as a base film for coating a green sheet in a process of coating a ceramic green sheet during the manufacturing process of a multilayer ceramic capacitor (MLCC), and painted by coating a silicone release agent before coating the green sheet. It is used as a base film to easily release the sheet. In order to improve processability, polyester films which play such a role generally disperse organic / inorganic particles, which are anti-blocking agents, on the surface to give irregularities to improve surface scratching and winding / runability. I'm using.

In addition, in order to make the thickness of the green sheet, which greatly affects the performance of the ceramic capacitor, the thickness of the film should be small and the variation should be small, and there should be no film defects causing defects in the green sheet. Should have

The green sheet required for the production of ceramic capacitors has a coating thickness ranging from several tens of micrometers in thickness to the mainstream these days, and in the future, the green sheet of 2 micrometers or less will become the mainstream. To this end, the development of a film with uniform thickness and no wrinkles is urgent. When a thin film is subjected to silicon processing or resist processing at a high temperature, wavy wrinkles occur on the film and a treatment phenomenon in which a part of the film sags occurs. As a result, when the green sheet for ceramic capacitors is manufactured, an uneven thickness or a portion of poor planarity is transferred to the resist layer or green sheet layer after the release, and there is a problem of insulation failure or leakage of current. The peeling failure may cause the green sheet to be broken or the like.

As the demand for high capacity and small size ceramic capacitors increases, the thickness of the ceramic coating layer of the green sheet tends to become thinner. As a result, it was common to have a coating thickness thicker than 3 μm, but recently, coating products having a thickness of 3 μm or less and 2 μm or less have been increasing. It is required to make the surface roughness of the polyester film which is the base film for green sheet release used at this time more uniform, and at the same time make the thickness variation of the film small and uniform.

In order to meet such a demand, Japanese Laid-Open Patent Publication No. 2004-058371 (2004.02.26) has a thickness variation of 1.0 m or less / 30 cm in the width direction orthogonal to the longitudinal direction of the film, and the birefringence of the film is- A biaxially stretched polyester film is described, wherein 0.080 ≦ Δn ≦ −0.020, where Δn = nMD-nTD, where nMD is the longitudinal refractive index and nTD is the widthwise refractive index.

In addition, Japanese Laid-Open Patent Publication No. 2004-291240 (October 21, 2004) has a release layer on one side of a simultaneous biaxially stretched polyester film, and a release film for forming a green sheet having a film thickness variation of 5% or less in both the longitudinal direction and the transverse direction. This is described.

In addition, Korean Patent Publication No. 10-0258571 (2000.03.13) has three stages of stretching in a longitudinal total draw ratio of 3.5 or more, and the crystallization energy is 20J / g or more and 15J / g or more in one and two stages of stretching. However, it is performed by parallel stretching between nip rolls at stretching temperature of 110 ~ 140 ℃ and stretching ratio of 1.5 ~ 2.5 times. This improves thickness uniformity and provides a biaxially oriented film without defects on the film surface.

In order to make the thickness uniform in the above-described conventional techniques, a simultaneous drawing method or a multi-stage longitudinal drawing method as a refractive index control and a drawing temperature, a draw ratio, and a drawing method have been proposed.

However, according to factors such as film thickness, draw ratio, and draw speed of film forming, the stretching temperature must be properly adjusted together to obtain the desired thickness uniformly. The present invention has been completed by setting a specific relationship so that the stretching temperature can be adjusted according to factors such as stretching speed and the like.

Japanese Patent Application Laid-Open No. 2004-058371 (2004.02.26) Japanese Patent Laid-Open No. 2004-291240 (2004.10.21) Korea Patent Publication No. 10-0258571 (2000.03.13)

In the present invention, both the width and length thickness variations are 3% or less, more preferably, the thickness variation is 2% or less, the surface roughness is uniform, the defects are reduced, and the workability is 10 to 50 μm thick poly. It is intended to provide a method for preparing an ester film.

In addition, the present invention is intended to provide a correlation between the thickness of the film, the stretching ratio, the stretching speed, the stretching temperature in order to reduce the variation in the width direction and longitudinal thickness.

As a result of the research to achieve the above object, the present invention was found to be able to produce a film having a uniform film thickness and a uniform film surface by using the following techniques to complete the present invention.

The present invention relates to a method for producing a polyester film,

a) A polyester chip was prepared by adding an antiblocking agent in which the weight ratio of particles (particle A) having an average particle diameter of 0.01 μm to 0.3 μm and particles (particle B) having an average particle diameter of 0.4 μm to 1.0 μm satisfy the following formula (1). Manufacturing;

2/1 ≤ A / B ≤ 5/1 [Equation 1]

(A is the weight of particle A, B is the weight of particle B.)

b) manufacturing a sheet by melt extruding the polyester chip and then biaxially stretching the sheet in a longitudinal direction and a transverse direction in a range satisfying the following Equations 2 to 5 to produce a polyester film;

[Formula 2]

T _g + [Vmd / 100 x Thmd]-5 ≤ Tmd ≤ Tg + [Vmd / 100 x Thmd] + 5

(Tmd is the film temperature at longitudinal stretching (℃), T _g is the glass transition temperature (℃) of the raw material resin measured by DSC, Vmd is the longitudinal stretching speed (% / min), and Thmd is the sheet thickness before longitudinal stretching ( cm).)

[Equation 3]

Tmd + [(Vtd / 100 x Thtd) x 30]-5 ≤ Ttd ≤ Tmd + [(Vtd / 100 x Thtd) x 30] + 5

(Ttd is the film temperature in transverse stretching (° C), Vtd is the transverse stretching speed in% / min, Thtd is the sheet thickness before transverse stretching (cm), and Tmd is the film temperature in longitudinal stretching (° C).)

[Formula 4]

Vmd = [(Xmd-1) / Lmd] x [(Vh-Vl) / 2] x 100

(Vmd is the longitudinal draw speed (% / min), Xmd is the longitudinal draw ratio, Lmd is the distance between draw rolls (m), Vh is the high roll speed (m / min), Vl is the low roll speed (m / min )to be.)

[Formula 5]

Vtd = (Xtd-1) x [(Vt) / Ltd] x 100

(Vtd is the transverse stretching speed (% / min), Xtd is the transverse stretching ratio, Ltd is the tenter stretching section distance (m), and Vt is the tenter clip speed (m / min).)

.

In the method for producing a polyester film of the present invention, the antiblocking agent in step a) may be used in 0.003 to 0.5% by weight of the polyester resin composition.

In the method for producing a polyester film of the present invention, the anti-blocking agent may be that the difference in refractive index with the polyester satisfy the following formula 6.

[Formula 6]

ΔN ≤ 0.3

(ΔN = | N ₁ N ₂ |, N ₁ is the refractive index of the biaxially stretched polyester, and N ₂ is the particle intrinsic refractive index.)

In the method for producing a polyester film of the present invention, the antiblocking agent is any one or two or more inorganic particles selected from silica, kaolin, barium sulfate, alumina silicate, calcium carbonate; Or any one selected from silicone resins, crosslinked divinylbenzene polymethacrylates, crosslinked polymethacrylates, crosslinked polystyrene resins, benzoguanamine-formaldehyde resins, benzoguanamine-melamine-formaldehyde resins and melamine-formaldehyde resins. One or two or more organic particles; may be selected from.

In the method for producing a polyester film of the present invention, the polyester film has a surface roughness of 20 nm or less, haze of 4% or less, and satisfies physical properties of an average number of fisheyes of 10 μm or more per area of 0.7 × 0.5 mm 2. Can be.

In the method for producing a polyester film of the present invention, the biaxially stretched polyester film in step b) may have a thickness of 10 to 50㎛.

In the manufacturing method of the polyester film of the present invention, the thickness deviation of the biaxially stretched polyester film in the step b) may be 3% or less.

The optical film according to the present invention can satisfy the haze characteristics basically provided by the optical film by effectively controlling the particle size and ratio.

In addition, it is possible to effectively control the pinhole and the scar of the adherend by controlling the appropriate surface roughness to secure the winding and workability, and to reduce the fish eye.

In addition, by adjusting the stretching temperature according to the film thickness and the draw ratio stretching speed, etc., it is possible to obtain a film having a uniform thickness in which the thickness variation is reduced compared to the existing.

1 shows a fisheye evaluation according to the present invention.
2 is a graph showing the mode of the antiblocking agent of the present invention.

Hereinafter, the present invention will be described more specifically.

One aspect of the present invention is

a) Particles (particle A) having an average particle diameter of 0.01 μm to 0.3 μm and an average particle diameter of 0.4 μm to 1.0 μm

Preparing an polyester chip by adding an antiblocking agent having a weight ratio of the factor (particle B) satisfying the following Formula 1;

[Formula 1]

2/1 ≤ A / B ≤ 5/1

(A is the weight of particle A, B is the weight of particle B.)

b) manufacturing a sheet by melt extruding the polyester chip and then biaxially stretching the sheet in a longitudinal direction and a transverse direction in a range satisfying the following Equations 2 to 5 to produce a polyester film;

[Formula 2]

Tg + [Vmd / 100 x Thmd]-5 ≤ Tmd ≤ Tg + [Vmd / 100 x Thmd] + 5

(Tmd is the film temperature (° C) during longitudinal stretching, Tg is the glass transition temperature (° C) of the raw resin measured by DSC, Vmd is the longitudinal stretching rate (% / min), and Thmd is the sheet thickness before longitudinal stretching (cm) )to be.)

[Equation 3]

Tmd + [(Vtd / 100 x Thtd) x 30]-5 ≤ Ttd ≤ Tmd + [(Vtd / 100 x Thtd) x 30] + 5

(Ttd is the film temperature in transverse stretching (° C.), Vtd is the transverse stretching speed (% / min), Thtd is the sheet thickness before transverse stretching (cm). Tmd is the film temperature in longitudinal stretching (° C.). This film temperature is measured with a non-contact IR thermometer.)

 [Formula 4]

Vmd = [(Xmd-1) / Lmd] x [(Vh-Vl) / 2] x 100 (% / min)

(Vmd is the longitudinal draw speed (% / min), Xmd is the longitudinal draw ratio, Lmd is the distance between draw rolls (m), Vh is the high roll speed (m / min), Vl is the low roll speed (m / min )to be.)

[Formula 5]

Vtd = (Xtd-1) x [(Vt) / Ltd] x 100 (% / min)

(Vtd is the transverse stretching speed (% / min), Xtd is the transverse stretching ratio, Ltd is the tenter stretching section distance (m), and Vt is the tenter clip speed (m / min).)

.

In an aspect of the present invention, a method of manufacturing the polyester chip of step a) will be described in more detail.

In one aspect of the present invention, in order to reduce the occurrence of fish eye as a defect on the surface of the film, when the particles used as an anti-blocking agent (film) in the film surface is limited to the following kinds, It is possible to produce very reduced films.

The antiblocking agent has particles (particle A) having an average particle diameter of 0.01 μm to 0.3 μm for increasing scratch resistance, and particles having an average particle size of 0.4 μm to 1.0 μm for giving antiblocking property and winding (winding) characteristics. ), It is preferable to use a mixture, and when using them mixed in the range of the following formula (1) it can minimize the fish eye by the particles. Specifically, when the particles having two sizes of the present invention are used in a specific weight ratio, the surface roughness is 20 nm or less, the haze is 4% or less, and the average number of fish eyes having an average size of 10 μm or more per 0.7 × 0.5 mm 2 area. It satisfies all the physical properties of 2 or less, and in addition to this, it is possible to produce a film excellent in workability. More specifically, the surface roughness is 16 to 20nm, the haze is 1.0% to 3.5%, the average number of fisheye satisfies 0 to 2 can be produced at the same time excellent polyester film.

Since the film presented in the present invention performs a factory inspection through the optical inspection of the adherend after bonding the adherend, it is preferable to have a low haze, and when the haze is usually 4% or less, more preferably 3.5% or less, the inspection is performed. Not only can the inspection be carried out without compromising the visibility of the film, but also the processing / runability of the film can be maintained.

In addition, in the present invention, when the surface roughness of the film is more than 20 nm, the winding runability and workability of the film is excellent, but it is a major cause of pinholes and scars on the adherend due to over-protrusion of the particles. The high surface roughness also increases the size of the particles used, thereby increasing the number of fish eyes, which is a major cause of the above-mentioned pinholes and other marks. When the surface roughness is less than 16 nm, the average number of fisheyes may satisfy the above-mentioned two because the inherent size of the particles decreases, but the antiblocking property, which is the purpose of particle injection, is lowered, resulting in deterioration of the runability and processability of the film. When winding up, surface projection may occur due to poor discharge after inflow of air and cause unevenness of the winding form. Therefore, it is necessary to limit the number of fish eye according to the above range while ensuring antiblocking property through appropriate selection of particle size.

The anti-blocking agent for satisfying such physical properties has a weight ratio of particles (particle A) having an average particle diameter of 0.01 μm to 0.3 μm and particles having an average particle diameter of 0.4 μm to 1.0 μm. It is desirable to satisfy.

[Formula 1]

2/1 ≤ A / B ≤ 5/1

(A is the weight of particle A, B is the weight of particle B.)

In the present invention, the mode means the maximum peak value on the particle size distribution of the particles, as indicated by arrows in FIG. 2.

When the weight ratio of A / B is less than 2/1 (that is, when there are a large number of large particles B relative to small particles A), film surface scattering is increased to increase Haze, and the number of fish eyes is two or more. It can increase the damage and pinhole of the adherend, and if the weight ratio of A / B is more than 5/1 (that is, when the large particle B is small compared to the small particle A), the surface blockability is increased. Workability may deteriorate and it may become a winding fault.

Moreover, it is more preferable to use what the difference of refractive index between a polyester base material and particle | grains satisfy | fills following formula (6).

[Formula 6]

ΔN ≤ 0.3

(ΔN = | N ₁ N ₂ |, N ₁ is the refractive index of the biaxially stretched polyester, and N ₂ is the particle intrinsic refractive index.)

Inorganic particles or organic particles may be used as the particles satisfying the above characteristics, and silica, kaolin, barium sulfate, alumina silicate, calcium carbonate, and the like may be used as the inorganic particles, but the present invention is not limited thereto. Can be used

Especially in the case of silica, it covers all the production methods polymerized by sedimentation method, sintering method and organically by TEOS (tetraethoxysilane) method. Examples of the organic particles include silicone resins, crosslinked divinylbenzene polymethacrylates, crosslinked polymethacrylates, crosslinked polystyrene resins, benzoguanamine-formaldehyde resins, benzoguanamine-melamine-formaldehyde resins, and melamine-formaldehyde resins. Organic particles such as but may be used, but are not limited thereto.

In the present invention, the particles are preferably used in 0.003 to 0.5% by weight in the film, when used in the above range can maintain the intrinsic winding property and releasability of the film. More preferably, the use of 0.006 to 0.2% by weight of the particles contained in the film further improves the winding property and releasability.

Within this range, the haze should satisfy 4.0% or less, more preferably 3.5% or less so that the present invention can accomplish the purpose.

If the above conditions are satisfied, it is possible to produce a film having 25% or more transparency and 80% or more fish eye properties compared to the general-purpose film currently used in the same particle content.

Although the base material which comprises the said polyester chip in this invention is not specifically limited, It is good to use normal polyester. Polyester is obtained by condensation-polymerizing the acid component which has dicarboxylic acid as a main component, and the glycol component which has alkyl glycol as a main component. Terephthalic acid or its alkyl ester or phenyl ester is mainly used as the main component of the dicarboxylic acid, but a part thereof is, for example, isophthalic acid, oxyethoxy benzoic acid, adipic acid, sebacic acid, and 5-sodium sulfoisophthalic acid. It may be used by substituting with difunctional carboxylic acid or ester forming derivative thereof. As the glycol component, ethylene glycol is mainly used, but for example, propylene glycol, neopentyl glycol, trimethylene glycol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, and 1,4-bisoxy It may be used in admixture with oxybenzene, bisphenol, polyoxyethylene glycol, or the like, and may be used in combination with a monofunctional or trifunctional compound if the content is small.

The polyester resin can be produced by a conventional polymerization method, that is, a method such as DMT polymerization method, but is not limited thereto. In addition, it may include any one or more components selected from additives commonly used in the film field, that is, a pinning agent, an antistatic agent, an ultraviolet stabilizer, a waterproofing agent, a slipping agent, and a thermal stabilizer.

In one embodiment of the present invention, the anti-blocking agent is preferably added at the time of polymerization of the polyester resin to prevent agglomeration of particles and to prevent defects by removing foreign substances, but is not limited thereto.

In one aspect of the present invention, the step of preparing the polyester film of step b) will be described in more detail.

The step b) is a process of manufacturing a polyester film by melt extruding and stretching the polyester chip prepared in step a), the temperature during melt extrusion is preferably 260 ~ 300 ℃. The melt extruded by melt extrusion is rapidly cooled to 30 ° C. or less with a large roll. A biaxially stretched polyester film is prepared by longitudinal stretching of the unstretched sheet quenched from above between the high speed roll and the low speed roll, and then stretching in the transverse direction.

If the thickness of the resist layer or the green sheet layer after releasing is uneven during the manufacture of the green sheet for the ceramic capacitor, problems may occur such as poor insulation or leakage of current. In addition, when the green sheet is thinned, problems such as cracking of the green sheet due to poor peeling may occur.

In order to improve this problem, in the present invention, both the longitudinal and widthwise thickness deviations are 3% or less, more specifically, the longitudinal and widthwise thickness deviations are all 1 to 3%, and when the film is wound, the thickness is 10 to 10%. It is preferable to manufacture the polyester film which is 50 micrometers.

Polyester films used as release substrates for ceramic capacitor green sheets are continuously becoming thinner, but if they are over 50㎛, they can be too expensive in terms of environmental load and cost too much when destroyed after use. . In addition, the thinning of less than 10㎛ the film must maintain the stiffness as a substrate in the coating and releasing operation, this property is too weak can increase the defective rate of processing. More preferably, a polyester film having a thickness of 20 to 40 µm is preferable.

In addition, the thickness variation of the polyester film to be produced is preferably 3% or less deviation between the maximum value and the minimum value of the thickness when measured in both the longitudinal direction and the transverse direction of the film. If the thickness variation is greater than 3%, the ceramic layer thickness of the green sheet coated with the thin thickness of 3 μm or less fluctuates due to the film thickness variation, and as a result, the capacity change of the manufactured ceramic capacitor is increased, resulting in higher defect rate. Can cause problems. More preferably, the thickness variation is 2% or less.

Therefore, in step b) according to an aspect of the present invention, in order to satisfy the thickness deviation, the longitudinal and transverse stretching conditions preferably satisfy the following Equations 2 to 5.

[Formula 2]

Tg + [Vmd / 100 x Thmd]-5 ≤ Tmd ≤ Tg + [Vmd / 100 x Thmd] + 5

(Tmd is the film temperature (° C) during longitudinal stretching, Tg is the glass transition temperature (° C) of the raw resin measured by DSC, Vmd is the longitudinal stretching rate (% / min), and Thmd is the sheet thickness before longitudinal stretching (cm) )to be.)

[Equation 3]

Tmd + [(Vtd / 100 x Thtd) x 30]-5 ≤ Ttd ≤ Tmd + [(Vtd / 100 x Thtd) x 30] + 5

(Ttd is the film temperature in transverse stretching (° C.), Vtd is the transverse stretching speed (% / min), Thtd is the sheet thickness before transverse stretching (cm). Tmd is the film temperature in longitudinal stretching (° C.). )

The film temperature may be measured by a non-contact IR thermometer.

[Formula 4]

Vmd = [(Xmd-1) / Lmd] x [(Vh-Vl) / 2] x 100 (% / min)

(Vmd is the longitudinal draw speed (% / min), Xmd is the longitudinal draw ratio, Lmd is the distance between draw rolls (m), Vh is the high roll speed (m / min), Vl is the low roll speed (m / min )to be.)

[Formula 5]

Vtd = (Xtd-1) x [(Vt) / Ltd] x 100 (% / min)

(Vtd is the transverse stretching speed (% / min), Xtd is the transverse stretching ratio, Ltd is the tenter stretching section distance (m), and Vt is the tenter clip speed (m / min).)

The longitudinal stretching refers to stretching through two rolls having different winding speeds, that is, a high speed roll and a low speed roll, and the lateral stretching refers to tenter stretching. In addition, longitudinal stretching and transverse stretching may be performed in one or more sections controlled by temperature and draw ratio.

In the above formula, Tg means the glass transition temperature (° C.) of the raw material resin measured by DSC, and the raw material resin means the polyester resin used in the production of the polyester chip.

In addition, Vmd means the longitudinal stretching speed (% / min), it is calculated by the stretching ratio in the longitudinal stretching and the speed of the roll participating in the stretching.

Thmd also refers to sheet thickness (cm) before longitudinal stretching.

In addition, Thtd means the sheet thickness (cm) before lateral stretch.

In addition, Vt means tenter clip speed (m / min), the tenter clip speed means the moving speed of the clip to enter the tenter holding the film to be stretched.

In the production of polyester film, the stretching temperature is a very important factor that affects the surface roughness and defect state of the film by changing the thickness variation of the film depending on the uniformity of the stretching and also changing the stretching situation around the antiblocking agent.

When the low temperature drawing of the film is too low, voids are generated, which causes the surface damage to the adherend on the surface regardless of the type of anti-blocking agent, and during high temperature drawing, the protrusion of the anti-blocking agent is maximized or the crystallization is uneven. According to the so-called butterfly-type defects may occur.

Accordingly, the present invention provides crystallinity by providing a high stretching temperature in the main stretching section between the stretching ratio conditions near the stretching crystallization point in the machine direction (MD) and a temperature range of 80 to 150 ° C, more preferably 90 to 130 ° C. This longitudinal stretch sheet which is low and is excellent in the adhesive force between resin and particle | grains can be obtained.

The reason for the application of the above temperature conditions is to select the particles having a high affinity with the substrate in order to prevent the generation of voids between the particles on the surface of the film, as well as the problem that the interface breakage between the particles and the substrate due to the stretching stress may occur. To block. In particular, the temperature of the main drawing section is characterized by setting a high temperature, when the drawing temperature is less than 79 ℃ cold drawing occurs in the sheet may cause the sheet to become cloudy, when the stretching temperature is above 150 ℃, yellowing by pyrolysis And property degradation may occur. Therefore, transparency can be improved by extending | stretching a film in high temperature conditions in which the physical property fall of resin does not occur.

In addition, it is important to select a draw ratio that can minimize stretching at the same time as the temperature range and at the same time to minimize the interface breakage and deformation of the resin surrounding the particles. As the draw ratio increases, the thickness of the film decreases with the poison ratio, thereby increasing the possibility of antiblocking agent protruding. Therefore, the draw ratio should be drawn in a range in which the mechanical strength of the polyester film does not decrease. Usually, the longitudinal / lateral stretching ratio is 25 times or more at maximum, but in the present invention, stretching is preferably 18 times or less. More specifically, it is preferable to stretch 2 to 5 times in the machine direction (longitudinal) stretching process, and most preferably, 2 to 4 times longitudinal stretching process can effectively block interfacial breakage and void generation with the resin.

In order to increase the thickness uniformity of the film by controlling the stretching temperature more precisely in these conditions, an appropriate stretching temperature should be set according to the change of the thickness, the stretching ratio, and the stretching speed of the film to make the stretching as uniform as possible to reduce the thickness variation. Good films of up to 3% in longitudinal and transverse thickness can be produced.

The longitudinal stretching temperature Tmd, which is carried out between the low and high rolls, depends on the sheet thickness change before stretching along with the draw rate determined by the draw ratio and draw roll difference, which is generally higher than 79 ° C. As shown in Equation 2, it is preferable to draw at a high or low temperature range of 5 ° C based on the calculated temperature. If it is higher than this temperature, it cannot be free from extending | stretching nonuniformity, and if lower than this temperature, longitudinal stretch orientation will become excessive and extending | stretching neck-in (width shrinkage) will increase and it will become a cause which becomes thickness nonuniform by generating nonuniform stretching in subsequent lateral stretching.

[Formula 2]

Tg + [Vmd / 100 x Thmd]-5 ≤ Tmd ≤ Tg + [Vmd / 100 x Thmd] + 5

(Tmd is the film temperature (° C) during longitudinal stretching, Tg is the glass transition temperature (° C) of the raw resin measured by DSC, Vmd is the longitudinal stretching rate (% / min), and Thmd is the sheet thickness before longitudinal stretching (cm) )to be.)

Thus, when longitudinal stretching is completed, the transverse stretching temperature Ttd is higher than the longitudinal longitudinal stretching temperature, and the transverse stretching speed and the transverse stretching sheet determined by the transverse ratio, the distance between the tenter stretching section, and the line speed as shown in Equation 3 below. It is preferable to draw in a high or low temperature range of 5 ° C based on the temperature calculated depending on the thickness of. If the temperature is higher than this temperature, it may not be free from stretching unevenness as in the case of longitudinal stretching. If it is lower than this temperature, breakage or cloudiness may occur due to excessive stretching of the film.

[Equation 3]

Tmd + [(Vtd / 100 x Thtd) x 30]-5 ≤ Ttd ≤ Tmd + [(Vtd / 100 x Thtd) x 30] + 5

(Ttd is the film temperature in transverse stretching (° C.), Vtd is the transverse stretching speed (% / min), Thtd is the sheet thickness before transverse stretching (cm). Tmd is the film temperature in longitudinal stretching (° C.). This film temperature is measured with a non-contact IR thermometer.)

The stretched film is heat-treated at 220-250 ° C. in a subsequent tenter oven, and then wound to obtain a film.

Hereinafter, the present invention will be described with reference to Examples for specific description of the present invention, but the present invention is not limited to the following Examples.

The measuring method used in the present Example is as follows.

1) Average particle size measurement of particles:

The average particle diameter was measured using a particle size distribution analyzer (Beckman-Coulter, LS13 320). The weight ratio A / B was calculated by the weight ratio of the A and B particles.

2) Haze measurement:

The measuring method was measured based on ASTM D-1003, and the polyester film was randomly extracted from 7 parts at 2 sides and 1 center, and then sliced into 5cm x 5cm sized haze measuring instruments (Nihonden Shoku NDH 300A). It was added to the light of 555nm wavelength and calculated by the following equation to calculate the average value except the maximum / minimum value.

Haze (%) = (total scattered light / total transmitted light) × 100

3) Surface roughness measurement:

Based on JIS B0601, the polyester film is sectioned into three places: left, middle, and right, and then cut into 3cm X 3cm size pieces and placed in a surface roughness measuring instrument (CAS is SE-3300 surface roughness meter). Ra (nm) was measured 5 times each and the average was computed.

(L: measuring length)

Speed: 0.05mm / s

Cut off: 0.08mm

Measuring Length (L): 1.50mm

4) Workability Evaluation:

The workability evaluation is performed by applying pellets prepared according to the above composition to a film forming facility to visually determine the winding shape and the running performance of the film in the winding step, and have the same quality and appearance as those of current products. ○ When the level is lower than the current product, the quality is poor compared to the current product, but when it is applicable due to a change of condition, △, X is not available.

5) Fisheye rating:

After separating the film produced as shown in Figure 1 to the left-middle-right at a constant interval with respect to the width direction, and then divided into 9 equal parts each at a predetermined interval to mark a total of 27 equal parts on the film, It was measured using a microscope (Leitz Orthoplan).

The measurement object was measured in a transmission mode using a microscope with a magnification of 100 to 500 times attached to the eyepiece. At this time, fisheye with a diameter of 10 ㎛ or more was visually detected and counted as follows.

-Sum of 3 evaluations within 9 equal parts of left, middle, and right

-Average of the results of the three evaluation sums

-Overall average of left, middle, and right evaluation results

At this time, the average number of fisheyes of 10 micrometers or more per area of 0.7x0.5mm <2> made it 2 or less.

Although it is possible to manage one member of evaluation in this way, two or more members of evaluation were finally determined by agreement after evaluation in order to ensure fairness of evaluation.

6) Thickness deviation measurement:

Samples were taken at a width of 1 m and a length of 30 m, and the thicknesses were measured using an Anritsu contact thickness gauge micrometer at 20 mm intervals in the width direction and 30 mm intervals in the longitudinal direction. The deviation R (%) was calculated by dividing the difference between the measured maximum value and the minimum value by the average thickness.

Example 1

Manufacture of Polyester Film

1000g of dimethyl terephthalate, 576g of ethylene glycol, and 300ppm of magnesium acetate, 400ppm of trimethyl phosphate were added to the reactor, and transesterification was carried out while methanol was discharged. After the transesterification reaction, silica particles A and silica particles B having average particle diameter values as shown in Table 1 were added to the product in the form of ethylene glycol sludge in an amount of 0.1% by weight relative to the polyester resin, and subjected to condensation polymerization under vacuum. A polyester chip having a viscosity of 0.61 was obtained. At this time, the weight ratio A / B calculated the weight ratio of A and B particle | grains from which an average particle diameter differs as mentioned above. As a result of measuring the prepared polyester chip by DSC, the glass transition temperature was 79 degreeC.

The polyester chip was melt-extruded at 280 ° C. and then rapidly cooled to 24 ° C. using a large roll to obtain a polyester sheet. After the obtained polyester sheet was longitudinally stretched under the conditions shown in Table 1 below, the biaxially stretched film obtained by stretching in the transverse direction was heat-treated at 240 ° C. to obtain a polyester film having a thickness of 25 μm, respectively.

The distance between the stretching rolls was 260 mm, the distance between the tenter stretching sections was 9 m, and the tenter clip speed was 130 mpm.

The haze, surface roughness and fisheye of the obtained polyester film were measured, and longitudinal and transverse thickness deviations were measured.

[Example 2]

As shown in Table 1 below, the average particle diameter values of the silica particles A and the silica particles B were varied, and the weight ratio A / B was adjusted.

In addition, the biaxially stretched film obtained by extending | stretching transversely after longitudinal drawing on the conditions similar to Table 1 was heat-processed at 240 degreeC, and the polyester film of 50 micrometers in thickness was obtained, respectively.

The distance between the stretching rolls was 260 mm, the distance between the tenter stretching sections was 9 m, and the tenter clip speed was 65 mpm.

The haze, surface roughness and fisheye of the obtained polyester film were measured, and longitudinal and transverse thickness deviations were measured.

[Example 3]

It carried out similarly to Example 1 except having set the average particle diameter value of particle | grain A to 0.2 micrometer, the average particle diameter value of particle | grain B to 0.8 micrometer, and changing the weight ratio of particle | grains.

The haze, surface roughness and fisheye of the obtained polyester film were measured, and longitudinal and transverse thickness deviations were measured.

Example 4

As shown in Table 1, it was carried out in the same manner as in Example 1 except for changing the content of the particles.

The haze, surface roughness and fisheye of the obtained polyester film were measured, and longitudinal and transverse thickness deviations were measured.

[Comparative Examples 1 to 5]

As shown in Table 1 below, the average particle diameter values of the silica particles A and the silica particles B were varied, and the weight ratio A / B was adjusted.

In addition, the biaxially stretched film obtained by longitudinal stretching after extending | stretching in the longitudinal direction on the conditions similar to Table 1 was heat-processed at 240 degreeC, and the polyester film which is 25 micrometers, 50 micrometers, and 75 micrometers in thickness, respectively was obtained.

The haze, surface roughness and fisheye of the obtained polyester film were measured, and longitudinal and transverse thickness deviations were measured.

[Table 1]

[Table 2]

[Table 3]

As shown in the above table, the examples satisfying the scope of the present invention showed low surface roughness, excellent haze, good transparency, excellent processability, and excellent fisheye of two or less. That is, it was found that the target surface roughness was 20 nm or less, the haze was 4% or less, and all the physical properties having an average number of fisheyes of 10 μm or more per area of 0.7 × 0.5 mm 2 were 2 or less and excellent in workability.

Moreover, in the Example which applied longitudinal and lateral stretch temperature in the range of the formula defined by this invention, the thickness deviation was favorable in less than 3% in both the longitudinal and the lateral directions.

In the case of Comparative Examples 1 and 3, the haze and fish-eye characteristics are excellent, but the particle size is small, the surface roughness is lowered, so that the anti-blocking property is deteriorated. It was impossible. In addition, when the longitudinal and transverse stretching temperatures were applied at a higher temperature than the range defined by the present invention, it was confirmed that the thickness variation was greater than 3% in both the longitudinal and the transverse directions, which was poorly evaluated by the customer of the ceramic capacitor manufacturing.

Comparative Examples 2 and 4 had good workability but high haze, and the fish eye characteristics were also poor due to the particle size, making it impossible to use the product. In addition, when the longitudinal and transverse stretching temperatures were applied at a lower temperature than the range defined by the present invention, it was confirmed that the thickness variation was greater than 3% in both the longitudinal and transverse directions, and Comparative Example 4 was broken at an excessively low temperature in the thick film.

Comparative Example 5 is a film thicker than that defined in the present invention, which is lower than the definition of the present invention at the time of film formation of 75 μm, resulting in failure due to poor stretching.

Claims (7)

a) A polyester chip was prepared by adding an antiblocking agent in which the weight ratio of particles (particle A) having an average particle diameter of 0.01 μm to 0.3 μm and particles (particle B) having an average particle diameter of 0.4 μm to 1.0 μm satisfy the following formula (1). Manufacturing;
2/1 ≤ A / B ≤ 5/1 [Equation 1]
(A is the weight of particle A, B is the weight of particle B.)
b) manufacturing a sheet by melt extruding the polyester chip and then biaxially stretching the sheet in a longitudinal direction and a transverse direction in a range satisfying the following Equations 2 to 5 to produce a polyester film;
[Formula 2]
T _g + [Vmd / 100 x Thmd]-5 ≤ Tmd ≤ Tg + [Vmd / 100 x Thmd] + 5
(Tmd is the film temperature at longitudinal stretching (℃), T _g is the glass transition temperature (℃) of the raw material resin measured by DSC, Vmd is the longitudinal stretching speed (% / min), and Thmd is the sheet thickness before longitudinal stretching ( cm).)
[Formula 3]
Tmd + [(Vtd / 100 x Thtd) x 30]-5 ≤ Ttd ≤ Tmd + [(Vtd / 100 x Thtd) x 30] + 5
(Ttd is the film temperature in transverse stretching (° C), Vtd is the transverse stretching speed in% / min, Thtd is the sheet thickness before transverse stretching (cm), and Tmd is the film temperature in longitudinal stretching (° C).)
[Formula 4]
Vmd = [(Xmd-1) / Lmd] x [(Vh-Vl) / 2] x 100
(Vmd is the longitudinal draw speed (% / min), Xmd is the longitudinal draw ratio, Lmd is the distance between draw rolls (m), Vh is the high roll speed (m / min), Vl is the low roll speed (m / min )to be.)
[Formula 5]
Vtd = (Xtd-1) x [(Vt) / Ltd] x 100
(Vtd is the transverse stretching speed (% / min), Xtd is the transverse stretching ratio, Ltd is the tenter stretching section distance (m), and Vt is the tenter clip speed (m / min).)
Method for producing a polyester film comprising a. The method of claim 1,
The anti-blocking agent in step a) is a method for producing a polyester film of 0.003 to 0.5% by weight of the polyester resin composition. The method of claim 1,
The anti-blocking agent is a method for producing a polyester film in which the refractive index difference with polyester satisfies the following formula 6.
[Formula 6]
ΔN ≤ 0.3
(ΔN = | N ₁ N ₂ |, N ₁ is the refractive index of the biaxially stretched polyester, and N ₂ is the particle intrinsic refractive index.) The method of claim 1,
The antiblocking agent is any one or two or more inorganic particles selected from silica, kaolin, barium sulfate, alumina silicate, calcium carbonate; Or any one selected from silicone resins, crosslinked divinylbenzene polymethacrylates, crosslinked polymethacrylates, crosslinked polystyrene resins, benzoguanamine-formaldehyde resins, benzoguanamine-melamine-formaldehyde resins and melamine-formaldehyde resins. One or two or more organic particles; Method of producing a polyester film. The method of claim 1,
The polyester film has a surface roughness of 20nm or less, has a haze of 4% or less, and satisfies the physical properties of the average number of fisheye of 10㎛ or more per area of 0.7 × 0.5mm2 2 or less. The method of claim 1,
Method for producing a polyester film having a thickness of the biaxially stretched polyester film in step b) is 10 ~ 50㎛. The method of claim 1,
Method for producing a polyester film having a thickness deviation of the biaxially stretched polyester film in step b) is 3% or less.

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