KR20150077746A - Polyester multi-layer film and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a polyester multilayer film and a manufacturing method thereof, wherein the polyester multilayer film has excellent process efficiency and a property thereof when used for manufacturing a BLU for a touch screen or an LCD with a low heat deformation rate and high dimensional stability. The polyester multilayer film is treated for 5 minutes by heat at 120°C under 200 N tension when the width of a film is 1 m, and treated for 5 minutes at 140°C. Then, a length change, measured with a thermal machine analyzer (TMA), satisfies inequality 1 and inequality 2.

Description

[0001] POLYESTER MULTI-LAYER FILM AND MANUFACTURING METHOD THEREOF [0002]

The present invention relates to a polyester multilayer film and a method of manufacturing the same, and is intended to provide a polyester multilayer film excellent in processability and physical properties when used for manufacturing touch screens or BLUs for LCDs with low dimensional strain and high dimensional stability, .

Optical films for ITO are films used for touch screens. ITO (Indium Tin Oxide) is coated on polyester films.

The touch screen panel is a panel that does not use an input device such as a keyboard or a mouse but detects a character or a specific position of a human hand or object when the touch is detected and processes a specific function. Such a touch screen, a base film for ITO, and a film for an ITO process are subjected to a high temperature heat treatment in a post-processing process, which causes heat distortion of the polyester film in the high temperature process, which causes problems such as curling and wrinkling.

In order to solve the above problems, the present invention provides a film having a low thermal strain and high dimensional stability and having excellent processability and physical properties when used in the manufacture of a touch screen or LCD BLU.

The inventors of the present invention have studied to produce a film having a lower thermal strain. As a result, they have found that a multilayer film having three or more layers is produced by coextrusion, and the diethylene glycol content of the polyester resin used in the production of the film, The present inventors have completed the present invention.

More specifically, the present invention relates to a multilayer film in which three or more polyester films are laminated. The film is heat treated at 120 DEG C for 5 minutes under a tension of 200 N when the film width is 1 m, heat-treated at 140 DEG C for 5 minutes, ) Satisfy the following formulas (1) and (2): " (1) "

[Formula 1]

Length at 80 ℃ - Initial length ≤ 20㎛

[Formula 2]

Length at 90 ℃ - initial length ≤ 25㎛

(Equations (1) and (2) are obtained by heating a specimen having a size of 16 mm x 5 mm at a heating rate of 5 deg. C / min from a temperature of 40 deg. C to a temperature of 180 deg. C while applying a load of 5 g using a thermomechanical analyzer 80 < 0 > C and 90 < 0 > C).

Also,

a) a step of pneumatically delivering a first polyester resin composition for a core layer and a second polyester resin composition for a skin layer by melt-extrusion and stacking three or more layers;

b) biaxially stretching the coextruded sheet to produce a film;

c) opening and fixing the stretched film; And

d) performing relaxation in a range in which the relaxation ratio in the width direction according to the following formula 3 satisfies 0 to 10%;

[Formula 3]

Relaxation rate (%) = (maximum width of stretching process - minimum width of stretching process) / maximum width of stretching process x 100

The present invention relates to a process for producing a polyester multi-layer film.

The polyester multi-layer film according to the present invention has an excellent heat resistance, so that it has less thermal deformation, less heat shrinkage, excellent surface properties, and excellent post-processability.

In addition, the polyester film according to the present invention has optical properties suitable for use in a heat-resistant film for ITO protection in a touch panel film, and the heat shrinkage ratio with respect to the full width of the film is controlled, It is easy to secure the processability in the lamination process of three or more films such as an interference fringe polyester film.

Hereinafter, the configuration of the present invention will be described in more detail.

An embodiment of the present invention is a multilayer film comprising three or more layers of a polyester film, wherein the film is heat-treated at 120 DEG C for 5 minutes under a tension of 200N when the film width is 1 m, heat-treated at 140 DEG C for 5 minutes, ) Satisfy the following formulas (1) and (2): " (1) "

[Formula 1]

Length at 80 ℃ - Initial length ≤ 20㎛

[Formula 2]

Length at 90 ℃ - initial length ≤ 25㎛

(Equations (1) and (2) are obtained by heating a specimen having a size of 16 mm x 5 mm at a heating rate of 5 deg. C / min from a temperature of 40 deg. C to a temperature of 180 deg. C while applying a load of 5 g using a thermomechanical analyzer 80 < 0 > C and 90 < 0 > C).

In one embodiment of the present invention, when applied to an optical film in the range in which the change in length satisfies Equation 1 and Equation 2 at the same time, it can be regarded as an optical film excellent in heat resistance and free from thermal shrinkage in a post-processing step. If the length is longer than 20 탆 from the initial length at 80 캜 or the length exceeds 25 탆 from the initial length at 90 캜, problems such as wrinkling may occur in the post-processing.

In one embodiment of the present invention, the multilayered film has a shrinkage ratio in the longitudinal direction of 0.3% or less, more specifically 0 to 0.3%, and a shrinkage ratio in the width direction of 0.2% or less after the heat treatment at 90 캜 for 60 minutes, more specifically 0 To 0.2%. When the shrinkage ratio in the longitudinal direction is more than 0.3% or the shrinkage ratio in the width direction is more than 0.2%, heat shrinkage occurs severely, and heat shrinkage may occur during the post-processing step.

In one embodiment of the present invention, the multilayered film may have a plane orientation coefficient of 0.158 or more, more specifically 0.158 to 0.160. When the plane orientation coefficient is less than 0.158, the degree of orientation is low, which may cause problems such as wrinkles in the post-processing process.

In one embodiment of the present invention, the polyester multilayer film may be composed of three or more layers including a core layer, a skin layer in which at least two layers are laminated on both sides of the core layer, and may be formed by coextrusion have.

The multi-layer film may have a total thickness of 50 to 300 탆, the core layer may be 70 to 90% of the total film thickness, and the skin layer may be 10 to 30% of the total film thickness. More preferably, the content of the core layer is 70 to 80% by weight, and the content of the skin layer is 20 to 30% by weight, which is effective because of excellent interfacial stability at the time of coextrusion and excellent barrier properties of oligomer.

The polyester resin used for the core layer and the skin layer may be the same or different. More specifically, it is preferable to use a polyethylene terephthalate (PET) resin. The polyethylene terephthalate resin used herein preferably has an intrinsic viscosity of 0.5 to 1.0, more preferably 0.60 to 0.80. If the intrinsic viscosity of the base layer polyethylene terephthalate resin is less than 0.5, the heat resistance may be reduced. If the intrinsic viscosity is more than 1.0, the workability of the raw material may not be easy and the workability may be decreased. The content of diethylene glycol in the polyethylene terephthalate (PET) resin used for the core layer is preferably 0.85% by weight or less, more preferably 0.1 to 0.85% by weight. When the diethylene glycol content is more than 0.85% by weight, the above-mentioned formula 1 and formula 2 can not be satisfied, and the desired physical properties can not be achieved by the heat shrinkage and the plane orientation coefficient. If such physical properties are not achieved, it is difficult to apply it as an optical film because it may cause appearance problems such as wrinkles in the post-process, and it is difficult to apply it as a film for BLU or ITO for LCD.

In addition, the polyester resin can be produced by a synthetic method apparent in the art in order to have an intrinsic viscosity and a diethylene glycol content within the above range, but in particular, those produced by solid phase polymerization have a reduced diethylene glycol content, .

In the present invention, it may further comprise particles to impart slipperiness to the skin layer as required. More specifically, the skin layer may further contain 10 to 50 ppm of inorganic particles having an average particle diameter of 3 탆 or less, more specifically 0.5 to 3 탆. As the inorganic particles, particles used in a film such as silica, zeolite, and kaolin are all possible. These inorganic particles come out to the surface of the film through a stretching process to improve slipperiness and windability of the film. When the particle size is more than 3 탆, transparency drops sharply when used for optics and touch panels, light transmittance decreases much, and it is difficult to judge defects visually in BLU evaluation, making it difficult to use for optical use. In addition, even if the content of the particles is 10 ppm or less, the transparency of the film is greatly decreased, and the smoothness is lowered at an illuminance (Ra) of 10 nm or more. When the particle content is more than 50 ppm, the transparency of the film is lowered even if particles smaller than 0.5 μm are used, which is not suitable for a touch panel.

The production of the polyester multilayer film comprising the core layer and the skin layer of the present invention is not limited, but can be obtained by casting after extrusion melting in at least two melt extruders and by biaxial stretching. More specifically, the polyester is extruded from one extruder, and the additives such as polyester and inorganic particles such as silica, kaolin, and zeolite are melt-extruded at the same time in another extruder, and then the respective melts meet in the feed block, Cast, cooled, sequentially biaxially stretched, and then heat-treated and relaxed.

More specifically, the method for producing a polyester multilayer film of the present invention comprises

a) a step of pneumatically delivering a first polyester resin composition for a core layer and a second polyester resin composition for a skin layer by melt-extrusion and stacking three or more layers;

b) biaxially stretching the coextruded sheet to produce a film;

c) opening and fixing the stretched film; And

d) performing relaxation in a range in which the relaxation ratio in the width direction according to the following formula 3 satisfies 0 to 10%;

[Formula 3]

Relaxation rate (%) = (maximum width of stretching process - minimum width of stretching process) / maximum width of stretching process x 100

.

More specifically, in step a), the core layer may be coextruded so that at least two skin layers are laminated on both sides of the core layer.

In addition, the first polyester resin composition and the second polyester resin composition may include a polyester resin having a diethylene glycol content of 0.85 wt% or less.

The second polyester resin composition may further contain 10 to 50 ppm of inorganic particles having an average particle size of 3 탆 or less.

In the step b), the biaxial stretching may be a stretching in the machine direction and then a stretching in the width direction. In this case, the stretching ratio may be 2 to 4 times in the machine direction and 2 to 5 times in the width direction.

In the step c), the heat setting is preferably performed at 150 to 250 ° C.

In the step d), relaxation is performed in a range in which the relaxation ratio in the width direction satisfies 0 to 10%, whereby a film satisfying the intended physical properties can be produced.

In the present invention, in the formula (3), the maximum width of the stretching process means a length when the film is the widest in the stretching process by stretching, and the minimum width of the stretching process means that the stretched film is the narrowest width Means the length of time.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to the following examples.

The following physical properties were measured by the following measurement methods.

1) Change in length

When the film width was 1 m, the substrate was heat-treated at 120 ° C for 5 minutes under a tension of 200 N, and heat-treated at 140 ° C for 5 minutes. Then, a length change was measured using a thermomechanical analyzer (TMA, TA Instrument, Q400) Respectively. The measurement conditions are as follows.

Specimen size: 16mm x 5mm

Temperature: Up to 40 ~ 180 ℃, Temperature increase rate 5 ℃ / min

Load: 5 g (mass of load-cell applied to specimen)

The length was measured at 80 ° C and the length at 90 ° C, and the change in the initial length was observed.

2) Heat shrinkage

The film was cut into 200 mm x 200 mm and allowed to stand in an oven at 90 deg. C for 60 minutes. Then, the length of the heat shrinkable film and the heat shrinkage in the width direction were determined according to the following formula.

3) Plane orientation coefficient

The film was cut into a size of 40 mm x 8 mm, and the refractive indexes in the length, width, and thickness directions were measured using an ABBE refractometer.

4) Intrinsic viscosity

0.4 g of PET pellet (sample) was added to 100 ml of a reagent in which phenol and 1,1,2,2-tetrachloroethanol were mixed at a weight ratio of 6: 4, and the mixture was transferred to a Ubero's viscometer. For 10 minutes, and the falling seconds of the solution was determined using a viscometer and an aspirator. The number of drops of the solvent was also determined by the same method, and RV and IV values were calculated by the following equations (1) and (2).

In the following equation, C represents the concentration of the sample.

[Equation 1]

&Quot; (2) "

5) DEG (Diethylene glycol) content

The content of diethylene glycol (DEG, Diethylene Glycol) was measured by placing 1 g of the sample in a 50 mL container, adding 3 mL of monoethanolamine and heating by using a hot plate to completely dissolve the sample, , And a solution of 0.005 g of 6-hexanediol dissolved in 20 mL of methanol was added, and 10 g of terephthalic acid was added to neutralize the solution. The resulting neutralized solution was filtered using a funnel and a filter paper, and the filtrate was subjected to gas chromatography to measure the DEG content (wt%). The GC analysis was carried out using a Shimadzu GC analyzer and according to the Shimadzu GC manual.

[Example 1]

Polyethylene terephthalate having an intrinsic viscosity of 0.65 and a diethylene glycol content of 0.85% by weight was extruded through a core layer and melt extruded. The skin layer had an intrinsic viscosity of 0.65 and a diethylene glycol content of 0.85% by weight Using polyethylene terephthalate, silica particles having a particle diameter of 0.7 탆 were melt-extruded using 30 ppm of the total weight of polyethylene terephthalate to perform co-extrusion casting. Thereafter, they were sequentially stretched three times in the machine direction and 3.6 times in the width direction, respectively, and heat treated at 230 DEG C, and then the relaxation rate was 7% in the width direction to produce a 250 mu m thick polyester multilayer film.

 The composition and content of the skin layer are shown in Table 1.

The core layer of the multi-layer film was 80% of the total film weight, and the skin layer was 20% of the total film weight. Physical properties of the film were measured and shown in Table 2.

[Example 2-3]

As shown in the following Table 1, the same procedure as in Example 1 was carried out except that the weight of the core layer and the skin layer were different.

Physical properties of the resulting film were measured and are shown in Table 2.

[Example 4-5]

As shown in the following Table 1, the same procedure as in Example 1 was carried out, except that the particle content of the skin layer was varied.

Physical properties of the resulting film were measured and are shown in Table 2.

[Comparative Example 1]

Polyethylene terephthalate having an intrinsic viscosity of 0.65 and a diethylene glycol content of 1.2% by weight was used as the core layer. The skin layer had an intrinsic viscosity of 0.65 and a diethylene glycol content of 1.2 wt% % ≪ / RTI > polyethylene terephthalate was used.

Physical properties of the resulting film were measured and are shown in Table 2.

[Comparative Example 2 - 3]

The same procedure as in Comparative Example 1 was carried out, except that the weight of the skin layer was varied as shown in Table 1. Physical properties of the resulting film were measured and are shown in Table 2.

[Comparative Example 4-5]

Comparative Example 1 was carried out in the same manner as in Table 1, except that the particle content of the skin layer was varied.

Physical properties of the resulting film were measured and are shown in Table 2.

[Comparative Example 6]

As shown in the following Table 1, the same tests as in Comparative Example 5 were conducted except that polyethylene terephthalate having a diethylene glycol content of 0.95 wt% was used for the skin layer and the core layer.

Physical properties of the resulting film were measured and are shown in Table 2.

[Table 1]

* Co-extruded with A / B / A. (Skin layer thickness is the total amount of positive A layer)

[Table 2]

As shown in the table, it was confirmed that the polyester resin had a degree of change of 80% at a temperature of 80 ° C and a small length change at a temperature of 90 ° C in the example in which the DEG content of the polyester resin was 0.85% and the polyester resin was relaxed in the transverse direction. Plane orientation coefficient was high.

Claims (10)

A multilayer film having three layers or more of a polyester film laminated thereon was heat-treated at 120 ° C for 5 minutes under a tension of 200 N at a film width of 1 m, heat-treated at 140 ° C for 5 minutes, and then measured using a thermomechanical analyzer Wherein the polyester film satisfies the following formulas (1) and (2).
[Formula 1]
Length at 80 ℃ - Initial length ≤ 20㎛
[Formula 2]
Length at 90 ℃ - initial length ≤ 25㎛
(Equations (1) and (2) are obtained by heating a specimen having a size of 16 mm x 5 mm at a heating rate of 5 deg. C / min from a temperature of 40 deg. C to a temperature of 180 deg. C while applying a load of 5 g using a thermomechanical analyzer 80 < 0 > C and 90 < 0 > C). The method according to claim 1,
Wherein the multilayered film has a shrinkage ratio in the longitudinal direction of 0.3% or less and a shrinkage ratio in the width direction of 0.2% or less after the heat treatment at 90 캜 for 60 minutes. The method according to claim 1,
Wherein the multilayered film has a plane orientation coefficient of 0.158 or more. The method according to claim 1,
Wherein the multi-layer film has three or more layers including a core layer and a skin layer in which at least two layers are co-extruded and laminated on both sides thereof. 5. The method of claim 4,
Wherein the multilayer film has a total thickness of 50 to 300 占 퐉, the core layer is 70 to 90% of the total film thickness, and the skin layer is 10 to 30% of the total film thickness. 5. The method of claim 4,
Wherein the core layer and the skin layer comprise a polyester resin having a diethylene glycol content of 0.85 wt% or less. 5. The method of claim 4,
Wherein the skin layer further comprises 10 to 50 ppm of inorganic particles having an average particle diameter of 3 mu m or less. a) a step of pneumatically delivering a first polyester resin composition for a core layer and a second polyester resin composition for a skin layer by melt-extrusion and stacking three or more layers;
b) biaxially stretching the coextruded sheet to produce a film;
c) opening and fixing the stretched film; And
d) performing relaxation in a range in which the relaxation ratio in the width direction according to the following formula 3 satisfies 0 to 10%;
[Formula 3]
Relaxation rate (%) = (maximum width of stretching process - minimum width of stretching process) / maximum width of stretching process x 100
≪ / RTI > 9. The method of claim 8,
Wherein the first polyester resin composition and the second polyester resin composition comprise a polyester resin having a diethylene glycol content of 0.85 wt% or less. 9. The method of claim 8,
Wherein the second polyester resin composition further comprises 10 to 50 ppm of inorganic particles having an average particle diameter of 3 m or less.