JPWO2016010134A1 - Uniaxially oriented polyester film, hard coat film, sensor film for touch panel, anti-scattering film, antireflection film, touch panel and method for producing uniaxially oriented polyester film - Google Patents

Abstract

A uniaxially oriented polyester film satisfying the following formula can suppress the occurrence of rainbow unevenness, can eliminate wrinkles and breakage in the processing step, and has a thickness suitable for a touch panel substrate; 20 μm ≦ t ≦ 60 μm; 2000 nm ≦ Re ≦ 6500 nm; 0.7 ≦ Re / Rth ≦ 1.4; 2000 MPa ≦ EMD; 2 ≦ ETD / EMD ≦ 3; 5 g · cm / cm ≦ TRTD; 50 MPa ≦ TBMD; t is the film thickness; Rth is the retardation in the film thickness direction; EMD is the elastic modulus in the film longitudinal direction; ETD is the elastic modulus in the film width direction; TRTD is the tear strength in the film width direction; TBMD is the breaking strength in the film longitudinal direction; , Sensor film for touch panel, anti-scattering film, anti-reflection film, touch panel And uniaxially oriented polyester film.

Description

  The present invention relates to a uniaxially oriented polyester film, a hard coat film, a sensor film for a touch panel, an anti-scattering film, an antireflection film, a touch panel, and a method for producing a uniaxially oriented polyester film. More specifically, the generation of rainbow unevenness can be suppressed, problems such as wrinkles and breakage in the processing steps of various films used for touch panels can be eliminated, and particularly suitable for use as a base material for various films for touch panels. The present invention relates to a method for producing a uniaxially oriented polyester film, a hard coat film, a sensor film for a touch panel, an anti-scattering film, an antireflection film, a touch panel, and a uniaxially oriented polyester film.

  In recent years, in touch panels, there has been a demand for suppression of rainbow unevenness when wearing polarized sunglasses and thinning of various film substrates used for touch panels. As a result, thin uniaxially oriented polyester films have begun to be used as substrates for various films (such as anti-scattering films, antireflection films, and transparent conductive films) used for touch panels.

  Patent Document 1 suppresses rainbow unevenness by using a polymer film with Re of 3000 nm or more and pasting it on a liquid crystal panel so that the slow axis of the polymer film is 45 ° oblique to the absorption axis of the polarizing plate. Is disclosed.

JP 2012-230390 A JP 2012-094699 A

Various films used for touch panels are often exposed to high temperature and high tension environments in processes such as coating, drying, and sputtering. As a result of studies by the present inventors, when a thin uniaxially oriented polyester film is used as a base material for a touch panel, the film is wrinkled as a result of being exposed to a high temperature or high tension environment in processes such as coating, drying, and sputtering. Or have been found to break often.
Patent Document 1 has no description regarding wrinkles or breakage of a thin uniaxially oriented polyester film. Thus, the present inventors have examined that the uniaxially oriented polyester film of Patent Document 1 is effective in suppressing rainbow unevenness, but is not effective in suppressing film breakage in subsequent processes such as a polarizing plate processing step and a coating step. It was sufficient, and it turned out that the use as a film for touch panels was difficult.

  On the other hand, in Patent Document 2, the heat fixing temperature of the polyester film is heat fixed at Tm-35 to 65 ° C., and heat relaxation treatment is performed at 140 to 175 ° C. It is disclosed to improve failures such as wrinkles in the process. Patent Document 2 shows that low heat shrinkage and uniformization of a film are effective for improving wrinkles and the like. However, Patent Document 2 only examines a biaxially oriented polyester film that has been biaxially stretched, and the uniaxially oriented polyester film has completely different physical properties from the biaxially oriented polyester film. The knowledge about the method of achieving suppression of the film fracture | rupture in post processes, such as an application | coating process, was not acquired.

  The problem to be solved by the present invention is that the occurrence of rainbow unevenness can be suppressed, problems such as wrinkles and breakage in the processing steps of various films used for touch panels can be solved, and particularly as a base material for various films for touch panels. It is to provide a method for producing a uniaxially oriented polyester film, a hard coat film, a sensor film for a touch panel, an anti-scattering film, an antireflection film, a touch panel and a uniaxially oriented polyester film having a thickness particularly suitable for use.

As a result of intensive studies to solve the above problems, the present inventors have found that the film thickness, the birefringence in the film in-plane direction, the ratio of the birefringence in the film in-plane direction and the film thickness direction, the MD direction The inventors have found that the above problems can be solved by controlling the elastic modulus, the ratio of the elastic modulus in the MD direction and the TD direction, the tear strength in the film width direction, and the breaking strength in the film longitudinal direction, and have completed the present invention.
The present invention, which is a specific means for achieving the above object, is as follows.

[1] A uniaxially oriented polyester film satisfying the following formulas 1 to 7;
20 μm ≦ t ≦ 60 μm Formula 1
2000 nm ≦ Re ≦ 6500 nm Formula 2
0.7 ≦ Re / Rth ≦ 1.4 Formula 3
2000 MPa ≦ EMD Formula 4
2 ≦ ETD / EMD ≦ 3 Formula 5
5 g · cm / cm ≦ TRTD Formula 6
50 MPa ≦ TBMD Formula 7
In formulas 1 to 7, t represents the film thickness, the unit is μm,
Re represents retardation in the film plane, the unit is nm,
Rth represents retardation in the film thickness direction, the unit is nm,
EMD represents the elastic modulus in the longitudinal direction of the film, the unit is MPa,
ETD represents the elastic modulus in the film width direction, the unit is MPa,
TRTD represents the tear strength in the film width direction, the unit is g · cm / cm,
TBMD represents the breaking strength in the longitudinal direction of the film, and its unit is MPa.
[2] The uniaxially oriented polyester film according to [1] has a thermal shrinkage rate of 0.8% or less in the MD direction after standing at 150 ° C. for 30 minutes of the uniaxially oriented polyester film described above.
The thermal shrinkage rate in the TD direction after standing at 150 ° C. for 30 minutes of the uniaxially oriented polyester film is 0.8% or less,
The absolute value of the difference between the thermal shrinkage rate in the MD direction and the thermal shrinkage rate in the TD direction is preferably 0.6% or less.
[3] The uniaxially oriented polyester film according to [1] or [2] preferably has an easy-adhesion layer laminated on at least one side of the uniaxially oriented polyester film described above.
[4] In the uniaxially oriented polyester film according to [3], the easy-adhesion layer includes particles,
The height at which the particles protrude from the surface of the easy-adhesion layer is preferably equal to or greater than the film thickness of the easy-adhesion layer;
The height at which the above-mentioned particles protrude from the surface of the above-mentioned easy adhesion layer is an average value at 5 points in the 1 mm square easy-adhesion layer.
[5] A hard coat film in which a hard coat layer is laminated on at least one surface of the uniaxially oriented polyester film according to any one of [1] to [4].
[6] A scattering prevention film in which an adhesive layer is laminated on at least one surface of the uniaxially oriented polyester film according to any one of [1] to [4].
[7] An antireflection film in which an antiglare layer is laminated on at least one surface of the uniaxially oriented polyester film according to any one of [1] to [4].
[8] A sensor film for a touch panel, comprising the uniaxially oriented polyester film according to any one of [1] to [4].
[9] The uniaxially oriented polyester film according to any one of [1] to [4], the hard coat film according to [5], the anti-scattering film according to [6], and the reflection according to [7]. A touch panel provided with at least one of a prevention film and the sensor film for touch panels as described in [8].
[10] The touch panel according to [9] includes a liquid crystal panel,
A polarizing plate disposed on the exit surface of the liquid crystal panel,
At least one slow axis of the uniaxially oriented polyester film, the hard coat film, the anti-scattering film, the anti-reflection film, and the sensor film for touch panel described above is relative to the absorption axis of the polarizing plate. , Preferably in the range of 45 ± 25 °.
[11] Manufacture of a uniaxially oriented polyester film according to any one of [1] to [4] using a tenter-type stretching device having a clip that travels along a pair of rails installed on both sides of a film conveyance path. A method,
A step of transversely stretching while holding a substantially unstretched polyester film with the above-mentioned clip;
A heat setting step of heating the polyester film after transverse stretching to the maximum temperature in the tenter,
The transverse stretching ratio in the transverse stretching step described above is controlled within the range of 3.3 times to 4.8 times,
In the above-mentioned transverse stretching step, the film surface temperature at the start of stretching is kept in the range of 80 ° C. or more and 95 ° C. or less, and the film surface temperature at the end of stretching is kept at 90 ° C. or more and 105 ° C. or less,
From the start of the stretching to the end of the stretching, gradually increase the film surface temperature,
The manufacturing method of the uniaxially-oriented polyester film whose thickness of the above-mentioned uniaxially-oriented polyester film is 20 micrometers or more and 60 micrometers or less.
[12] The method for producing a uniaxially oriented polyester film according to [11], in the above-described transverse stretching step,
The film surface temperature in the range of draw ratio of 1 to 2 times is 80 ° C. or more and 92 ° C. or less,
The film surface temperature in the range of draw ratio of 2 to 3 times is 85 ° C or higher and 97 ° C or lower,
It is preferable to maintain the film surface temperature in the range where the draw ratio is 3 times or more at 90 ° C. or more and 102 ° C. or less;
However, the film surface temperature in the range where the draw ratio is 2 to 3 times is not lower than the film surface temperature in the range where the draw ratio is 1 to 2 times, and the film surface temperature in the range where the draw ratio is 3 times or more is stretched. The magnification never falls below the film surface temperature in the range of 2 to 3 times.
[13] The method for producing a uniaxially oriented polyester film described in [11] or [12] is a method of heating the above-mentioned heat-fixed polyester film and reducing the length of at least the MD direction of the above-mentioned polyester film. Including a relaxation process,
In the above-mentioned heat relaxation step, the relaxation rate in the MD direction, which is the ratio of reducing the length in the MD direction of the heat-fixed polyester film, is set to 1-7%, and the heat-fixed polyester film in the TD direction It is preferable to set the relaxation rate in the TD direction, which is the ratio of shortening the length, to 0 to 6%.
[14] In the method for producing a uniaxially oriented polyester film described in [13], it is preferable to keep the maximum film surface temperature in the above-described heat setting and the above-described heat relaxation step in a range of 130 ° C. or more and 190 ° C. or less.

  According to the configuration of the present invention, the occurrence of rainbow unevenness can be suppressed, and problems such as wrinkles and breakage in the processing steps of various films used for touch panels can be eliminated, especially for use as a base material for various films for touch panels. A particularly suitable thickness of the uniaxially oriented polyester film, hard coat film, sensor film for touch panel, anti-scattering film, antireflection film, touch panel and uniaxially oriented polyester film can be provided.

  Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be made based on representative embodiments and specific examples, but the present invention is not limited to such embodiments. In the present specification, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

  Moreover, although the manufacturing method of a polyester film is explained in full detail behind, a polyester film is normally obtained by conveying using a roll etc. and extending | stretching. At this time, the film conveyance direction is also referred to as MD (Machine Direction) direction. The MD direction of the film is also referred to as the longitudinal direction of the film. The film width direction is a direction orthogonal to the longitudinal direction. The film width direction is also called a TD (Transverse Direction) direction in a film manufactured while transporting the film.

[Uniaxially oriented polyester film]
The uniaxially oriented polyester film of the present invention (hereinafter also simply referred to as “film”) satisfies the following formulas 1-7.
20 μm ≦ t ≦ 60 μm Formula 1
2000 nm ≦ Re ≦ 6500 nm Formula 2
0.7 ≦ Re / Rth ≦ 1.4 Formula 3
2000 MPa ≦ EMD Formula 4
2 ≦ ETD / EMD ≦ 3 Formula 5
5 g · cm / cm ≦ TRTD Formula 6
50 MPa ≦ TBMD Formula 7
In formulas 1 to 7, t represents the film thickness, the unit is μm,
Re represents retardation in the film plane, the unit is nm,
Rth represents retardation in the film thickness direction, the unit is nm,
EMD represents the elastic modulus in the longitudinal direction of the film, the unit is MPa,
ETD represents the elastic modulus in the film width direction, the unit is MPa,
TRTD represents the tear strength in the film width direction, the unit is g · cm / cm,
TBMD represents the breaking strength in the longitudinal direction of the film, and its unit is MPa.

With such a configuration, the uniaxially oriented polyester film of the present invention can suppress the occurrence of rainbow unevenness, and can solve problems such as wrinkles and breakage in the processing steps of various films used for touch panels, especially various films for touch panels. The thickness is particularly suitable for use as a substrate.
About uniaxially oriented polyester film, generation of rainbow unevenness can be suppressed, problems such as wrinkles and breakage in the processing process of various films used for touch panels can be solved, and particularly suitable for use as a base material for various films for touch panels Such a thickness could not be achieved by the conventional manufacturing method. On the other hand, in the present invention, the uniaxially oriented polyester with physical properties specified in the present invention is increased by increasing the stretching temperature as the stretching ratio increases while keeping the film surface temperature at the start and end of the transverse stretching step within a specific range. It came to discover that a film could be manufactured. Such a method for producing a uniaxially oriented polyester film of the present invention is completely different from a conventionally known production method. In the first place, in the transverse stretching step, there has been little known a method for increasing the stretching temperature as the stretching ratio increases. In addition, the uniaxially oriented polyester film having physical properties defined in the present invention is based on the assumption that fine polyester crystals (sometimes called spherulites) are generated when heated in an unstretched state. As a result of paying attention to the suppression of the occurrence of the polyester, in the lateral stretching step, it is a fine polyester that the stretching temperature is increased as the stretching ratio is increased while the film surface temperature at the start to the end of the lateral stretching step is within a specific range The present inventors have noticed that it is effective in suppressing the generation of crystals, and have found a new production method, which makes it possible to produce the crystal. Therefore, the uniaxially oriented polyester film having the physical properties specified in the present invention can be obtained by referring to, combining, or further changing the usual design changes described in JP2012-230390A, JP2012-094699A, and the like. Even if it is examined, it is difficult to manufacture.
Hereinafter, the preferable aspect of the uniaxially-oriented polyester film of this invention is demonstrated.

<Characteristics of uniaxially oriented polyester film>
(Thickness)
The thickness of the uniaxially oriented polyester film of the present invention satisfies the following formula 1.
20 μm ≦ t ≦ 60 μm Formula 1
In formulas 1 to 7, t represents the film thickness, and the unit is μm.
The film thickness t is more preferably 25 μm or more and 55 μm or less, and further preferably 30 μm or more and 50 μm or less. If the thickness is less than 20 μm, rainbow unevenness occurs. If the thickness is more than 60 μm, the thickness is too thick to be suitable as a film substrate for a touch panel.
The thickness t of the uniaxially oriented polyester film is obtained by, for example, sampling 50 points at equal intervals over 0.5 m in the longitudinally stretched direction (longitudinal direction) using a contact-type film thickness meter, and further in the film width direction (longitudinal direction). After sampling 50 points at equal intervals (50 equal parts in the width direction) over the entire width of the film in the direction perpendicular to each other, the thicknesses of these 100 points were measured. The average thickness of these 100 points was determined and used as the thickness of the uniaxially oriented polyester film.

(Phase difference)
The in-plane retardation Re of the uniaxially oriented polyester film of the present invention satisfies the following formula 2.
2000 nm ≦ Re ≦ 6500 nm Formula 2
Re represents retardation in the film plane, and its unit is nm.
The retardation Re in the in-plane direction is more preferably 2500 nm to 5500 nm, and still more preferably 3000 nm to 5000 nm. If it is less than 2000 nm, rainbow unevenness occurs, and if it exceeds 6500 nm, the thickness becomes too thick to be suitable as a film substrate for a touch panel.

  The uniaxially oriented polyester film of the present invention has a thickness direction retardation Rth of preferably 3000 to 30000 nm, more preferably 3500 to 25000 nm, and still more preferably 4000 to 20000 nm. In principle, it is difficult to make a film with Rth below 3000 nm. When it is 30000 nm or less, color unevenness on the screen hardly occurs when a panel is used, which is preferable.

In the uniaxially oriented polyester film of the present invention, the ratio (Re / Rth) between the in-plane retardation Re and the thickness direction retardation Rth satisfies the following formula 3.
0.7 ≦ Re / Rth ≦ 1.4 Formula 3
Re represents retardation in the film plane, the unit is nm,
Rth represents retardation in the film thickness direction, and its unit is nm.
Re / Rth is more preferably from 0.8 to 1.2, and even more preferably from 0.85 to 1.1. If it is less than 0.7, rainbow unevenness occurs, and if it exceeds 1.4, there is a trade-off with higher Re, and conversely, rainbow unevenness tends to occur.

Nijimura can also be reduced by setting the Nz value representing the relationship between Re and Rth to an appropriate value, and the absolute value of the Nz value is 2.0 or less due to the effect of reducing rainbow unevenness and manufacturing suitability. Is preferably 0.5 to 2.0, and more preferably 0.5 to 1.5.
Since rainbow unevenness is generated by incident light, it is usually observed during white display.
The in-plane retardation value Re of the uniaxially oriented polyester film of the present invention is represented by the following formula (14).

Re = (nx−ny) × y ₁ (14)
Here, nx is the refractive index in the in-plane slow axis direction of the polyester film, ny is the refractive index in the in-plane fast axis direction (direction perpendicular to the in-plane slow axis direction) of the polyester film, and y ₁ is the thickness of the polyester film.

  The retardation Rth in the thickness direction of the uniaxially oriented polyester film of the present invention is represented by the following formula (15).

Rth = {(nx + ny) / 2−nz} × y ₁ (15)
Here, nz is the refractive index in the thickness direction of the polyester film.

  In addition, Nz value of a polyester film is represented by following formula (16).

Nz = (nx−nz) / (nx−ny) (16)

In this specification, Re, Rth, and Nz at a wavelength λnm can be measured as follows.
Using two polarizing plates, the orientation axis direction of the polyester film was determined, and a 4 cm × 2 cm rectangle was cut out so that the orientation axis directions were perpendicular to each other, and used as a measurement sample. For this sample, the biaxial refractive index (Nx, Ny) perpendicular to each other and the refractive index (Nz) in the thickness direction were determined by an Abbe refractometer (Atago Co., Ltd., NAR-4T, measurement wavelength 589 nm). The absolute value (| Nx−Ny |) of the biaxial refractive index difference was defined as the refractive index anisotropy (ΔNxy). The thickness y ₁ (nm) of the polyester film was measured using an electric micrometer (manufactured by Fine Reef, Millitron 1245D), and the unit was converted to nm. Measured Nx, Ny, Nz, Re from the value of _{y 1,} Rth, Nz was calculated.

The above Re and Rth should be adjusted according to the type of polyester resin used in the film, the amount of the polyester resin and additives described above, the addition of a retardation developer, the film thickness, the film stretching direction and the stretching ratio, etc. Can do.
The method for controlling the uniaxially oriented polyester film of the present invention within the above ranges of Re and Rth is not particularly limited, but can be achieved by, for example, a stretching method.

(Elastic modulus)
In the uniaxially oriented polyester film of the present invention, the elastic modulus EMD in the film longitudinal direction satisfies the following formula 4.
2000 MPa ≦ EMD Formula 4
EMD represents the elastic modulus in the longitudinal direction of the film, and its unit is MPa.
The elastic modulus EMD in the film longitudinal direction is more preferably 2200 MPa or more, and further preferably 2400 MPa or more. If the elastic modulus EMD in the longitudinal direction of the film is less than 2000 MPa, wrinkles and breakage are likely to occur. There is no particular upper limit to the elastic modulus EMD in the longitudinal direction of the film, but in order to produce a uniaxially oriented polyester film compatible with Re and Re / Rth, it is considered that the upper limit is substantially about 3500 MPa.

In the uniaxially oriented polyester film of the present invention, the ratio ETD / EMD of the elastic modulus in the TD direction to the elastic modulus in the MD direction satisfies the following formula 5.
2 ≦ ETD / EMD ≦ 3 Formula 5
EMD represents the elastic modulus in the longitudinal direction of the film, the unit is MPa,
ETD represents the elastic modulus in the film width direction, and its unit is MPa.
The ratio ETD / EMD of the elastic modulus in the TD direction to the elastic modulus in the MD direction is more preferably 2.1 or more and 2.9 or less, and further preferably 2.2 or more and 2.8 or less. If the ratio ETD / EMD of the elastic modulus in the TD direction to the elastic modulus in the MD direction exceeds 3, wrinkles in the vertical direction are likely to occur. When the ratio ETD / EMD of the elastic modulus in the TD direction to the elastic modulus in the MD direction is less than 2, it becomes difficult to achieve both Re and Re / Rth.

(Tear strength)
In the uniaxially oriented polyester film of the present invention, the tear strength TRTD in the film width direction satisfies the following formula 6.
5 g · cm / cm ≦ TRTD Formula 6
TRTD represents the tear strength in the film width direction, and its unit is g · cm / cm.
The tear strength TRTD in the film width direction is more preferably 6 g · cm / cm or more, and still more preferably 7 g · cm / cm or more. When the tear strength TRTD in the film width direction is less than 5 g · cm / cm, breakage is likely to occur during conveyance. There is no particular upper limit to the tear strength TRTD in the film width direction, but it is difficult to achieve both thickness, Re and Re / Rth to exceed 25 g · cm / cm.

(Breaking strength)
In the uniaxially oriented polyester film of the present invention, the breaking strength TBMD in the film longitudinal direction satisfies the following formula 7.
50 MPa ≦ TBMD Formula 7
TBMD represents the breaking strength in the longitudinal direction of the film, and its unit is MPa.
The breaking strength TBMD in the longitudinal direction of the film is more preferably 60 MPa or more, and further preferably 65 MPa or more. When the breaking strength TBMD in the longitudinal direction of the film is less than 50 MPa, breakage is likely to occur during conveyance. There is no particular upper limit to the breaking strength TBMD in the longitudinal direction of the film, but it is difficult to achieve both Re and Re / Rth if it exceeds 100 MPa.

(Heat shrinkage)
In the uniaxially oriented polyester film of the present invention, the thermal shrinkage in the MD direction after standing at 150 ° C. for 30 minutes is preferably 0.8% or less, more preferably 0.6% or less, and 0.4% or less. Is more preferable. If it is 0.8% or less, wrinkles are hardly generated on the film.
In the uniaxially oriented polyester film of the present invention, the thermal shrinkage in the TD direction after standing at 150 ° C. for 30 minutes is preferably 0.8% or less, more preferably 0.6% or less, and 0.4% or less. Is more preferable. If it is 0.8% or less, wrinkles are hardly generated on the film.

  In the uniaxially oriented polyester film of the present invention, the absolute value of the difference between the thermal shrinkage rate in the MD direction and the thermal shrinkage rate in the TD direction is preferably 0.6% or less. The absolute value of the difference between the thermal shrinkage rate in the MD direction and the thermal shrinkage rate in the TD direction is more preferably 0.4% or less, and still more preferably 0.3% or less. If the absolute value of the difference between the thermal shrinkage rate in the MD direction and the thermal shrinkage rate in the TD direction is 0.6% or less, the film is less likely to be wrinkled.

In the present invention, the heat shrinkage rate in the MD direction after standing at 150 ° C. for 30 minutes (the heat shrinkage rate in the longitudinal direction of the film after heating at 150 ° C. for 30 minutes (150 ° C., 30 minutes)) is as follows: Defined in
Two reference lines are put in advance in a sample piece M of a polyester film cut in 30 mm in the TD direction and 120 mm in the MD direction so as to have an interval of 100 mm in the MD direction in advance. After the sample piece M is left in a heating oven at 150 ° C. for 30 minutes under no tension, the sample piece M is cooled to room temperature, and the interval between the two reference lines is measured. The interval after processing measured at this time is A [mm]. The numerical value [%] calculated by using the formula “100 × (100−A) / 100” from the interval 100 mm before the treatment and the interval Amm after the treatment is used as the MD thermal contraction rate (S ).
The heat shrinkage in the MD direction is also called MD heat shrinkage, and the ratio is called MD heat shrinkage rate. Therefore, the thermal contraction rate in the direction orthogonal to the film width direction is also expressed as MD thermal contraction rate.

In the present invention, the thermal contraction rate in the TD direction after standing at 150 ° C. for 30 minutes (the thermal contraction rate in the film width direction after heating at 150 ° C. for 30 minutes (150 ° C., 30 minutes)) is as follows: Defined in
Two reference lines are put in advance in a sample piece M of a polyester resin film cut in 30 mm in the MD direction and 120 mm in the TD direction so as to have an interval of 100 mm in the TD direction. The sample piece M is allowed to stand for 30 minutes in a heating oven at 150 ° C. under no tension, and then the sample piece M is cooled to room temperature, and the interval between the two reference lines is measured. The interval after processing measured at this time is A [mm]. The numerical value [%] calculated by using the formula “100 × (100−A) / 100” from the interval 100 mm before the processing and the interval Amm after the processing is calculated as the TD heat shrinkage rate (S ).
The thermal contraction in the TD direction is also referred to as TD thermal contraction, and the ratio is referred to as the TD thermal contraction rate. Therefore, the thermal contraction rate in the direction orthogonal to the film width direction is also expressed as TD thermal contraction rate.

(Film length)
The uniaxially oriented polyester film of the present invention preferably has a film length of 100 m or more and is wound in a roll form.
The film length is preferably 100 m or more, more preferably 300 m or more, and even more preferably 500 m or more. Even if the uniaxially oriented polyester film of the present invention has such a length and is wound in the form of a roll, it is also possible to suppress wrapping and wrinkling in the form of a roll.

(Refractive index, crystallinity)
The uniaxially oriented polyester film of the present invention is preferably uniaxially oriented. Specifically, the uniaxially oriented polyester film of the present invention preferably has a refractive index in the longitudinal direction of 1.590 or less and a crystallinity of more than 5%.
The preferred range of the refractive index in the longitudinal direction of the uniaxially oriented polyester film of the present invention is the same as the preferred range of the refractive index in the longitudinal direction of the unstretched polyester film.
The degree of crystallinity of the uniaxially oriented polyester film of the present invention is preferably 5% or more, more preferably 20% or more, and still more preferably 30% or more.

<Uniaxially oriented polyester film material, layer structure, surface treatment>
The uniaxially oriented polyester film of the present invention contains a polyester resin.
The uniaxially oriented polyester film of the present invention may be a single-layer film having a polyester resin as a main component or a multilayer film having at least one layer having a polyester resin as a main component. Moreover, the surface treatment may be performed on both surfaces or one surface of these single layer films or multilayer films, and this surface treatment is performed by corona treatment, saponification treatment, heat treatment, ultraviolet irradiation, electron beam irradiation, or the like. Modification may be sufficient, and thin film formation by application | coating, vapor deposition, etc. of a polymer, a metal, etc. may be sufficient. The mass ratio of the polyester resin in the entire film is usually 50% by mass or more, preferably 70% by mass or more, more preferably 90% by mass or more.
The uniaxially oriented polyester film of the present invention preferably has an easy adhesion layer laminated on at least one side of the uniaxially oriented polyester film described above. More preferably, the easy-adhesion layer contains particles, and the height at which the particles protrude from the surface of the easy-adhesion layer is equal to or greater than the film thickness of the easy-adhesion layer;
The height at which the above-mentioned particles protrude from the surface of the above-mentioned easy adhesion layer is an average value at 5 points in the 1 mm square easy-adhesion layer.
When the height of the particles contained in the easy-adhesive layer is less than the film thickness of the easy-adhesive layer (preferably the coating layer), the slipperiness decreases and wrinkles occur. Is likely to occur.
The type of particle is not particularly limited as long as it satisfies the object of the present invention. Specific examples include, for example, silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, magnesium phosphate, Examples of the particles include kaolin, aluminum oxide, titanium oxide, and zirconium oxide, and silica, aluminum oxide, titanium oxide, and zirconium oxide are preferable. Further, the heat-resistant organic particles described in JP-B-59-5216, JP-A-59-217755 and the like may be used. Examples of other heat-resistant organic particles include thermosetting urea resins, thermosetting phenol resins, thermosetting epoxy resins, benzoguanamine resins, and the like.
Regarding the particle size, the above-mentioned easy-adhesion layer preferably has a particle diameter such that the height at which the above-mentioned particles protrude from the surface of the above-mentioned easy-adhesion layer is equal to or greater than the film thickness of the above-mentioned easy-adhesion layer. Although it is preferable to use particles whose primary average particle diameter is adjusted, as a result, the height at which the above-mentioned particles protrude from the surface of the above-mentioned easy-adhesion layer is aggregated so as to be equal to or greater than the film thickness of the above-mentioned easy-adhesion layer. It may be a particle. In the case of agglomerated particles, the height at which the aforementioned particles protrude from the surface of the aforementioned easy-adhesion layer can be confirmed by measuring the secondary average particle diameter.

(1-1) Polyester resin As the above-mentioned polyester resin, one having the composition of [0042] of WO2012 / 157762 is preferably used.
As the polyester, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), polycyclohexanedimethylene terephthalate (PCT), etc. can be used, but PET and PEN are more preferable because of cost and heat resistance. More preferably, it is PET (PEN tends to have a small Re / Rth).
Polyester is most preferably polyethylene terephthalate, but polyethylene naphthalate can also be preferably used. For example, those described in JP-A-2008-39803 can be preferably used.

  Polyethylene terephthalate is a polyester having a structural unit derived from terephthalic acid as a dicarboxylic acid component and a structural unit derived from ethylene glycol as a diol component, and 80 mol% or more of all repeating units are preferably ethylene terephthalate. The structural unit derived from other copolymerization components may be included. Other copolymer components include isophthalic acid, para-β-oxyethoxybenzoic acid, 4,4′-dicarboxydiphenyl, 4,4′-dicarboxybenzophenone, bis (4-carboxyphenyl) ethane, adipic acid , Dicarboxylic acid components such as sebacic acid, 5-sodium sulfoisophthalic acid, 1,4-dicarboxycyclohexane, propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanediol, ethylene oxide adduct of bisphenol A, polyethylene glycol And diol components such as polypropylene glycol and polytetramethylene glycol. These dicarboxylic acid components and diol components can be used in combination of two or more if necessary. It is also possible to use an oxycarboxylic acid such as para-oxybenzoic acid together with the carboxylic acid component or diol component. As another copolymer component, a dicarboxylic acid component and / or a diol component containing a small amount of an amide bond, a urethane bond, an ether bond, a carbonate bond, or the like may be used. Polyethylene terephthalate can be produced by a direct polymerization method in which terephthalic acid and ethylene glycol and, if necessary, other dicarboxylic acid and / or other diol are directly reacted, dimethyl ester of terephthalic acid and ethylene glycol, and necessary Depending on the above, any production method such as a so-called transesterification method in which a dimethyl ester of another dicarboxylic acid and / or another diol is transesterified can be applied.

(1-2) Physical properties of polyester resin (1-2-1) Intrinsic viscosity The intrinsic viscosity IV (Intrinsic Viscosity) of the polyester resin is preferably 0.5 or more and 0.9 or less, more preferably 0.52 or more and 0.8. Hereinafter, it is more preferably 0.54 or more and 0.7 or less. In order to obtain such an IV, solid phase polymerization may be used in combination with the melt polymerization described later when the polyester resin is synthesized.

(1-2-2) Acetaldehyde content The polyester resin preferably has an acetaldehyde content of 50 ppm or less. More preferably, it is 40 ppm or less, Most preferably, it is 30 ppm or less. Acetaldehyde easily causes a condensation reaction between acetaldehydes, and water is generated as a side reaction product, which may cause hydrolysis of the polyester. The lower limit of the acetaldehyde content is practically about 1 ppm. In order to keep the acetaldehyde content in the above range, keep the oxygen concentration in each step such as melt polymerization and solid phase polymerization at the time of resin production, keep the oxygen concentration at the time of resin storage and drying, at the time of film production Methods such as lowering the heat history applied to the resin by an extruder, melt piping, die, etc., or preventing local strong shearing by the screw configuration of the extruder during melting, etc. can be employed.

(1-3) Catalyst For the polymerization of the polyester resin, Sb, Ge, Ti, Al-based catalysts are used, preferably Sb, Ti, Al-based catalysts, and more preferably Al-based catalysts.
That is, it is preferable that the polyester resin used as the raw material resin is polymerized using an aluminum catalyst.
By using an Al-based catalyst, it becomes easier for Re to be expressed than when other catalysts (for example, Sb, Ti) are used, and PET can be thinned. That is, it means that the Al-based catalyst is more easily oriented. This is presumed to be due to the following reasons.
Since the Al-based catalyst has a lower reactivity (polymerization activity) than Sb and Ti, the reaction is mild, and a by-product (diethylene glycol unit: DEG) is hardly generated.
As a result, the regularity of PET increases, and it is easy to align and to express Re.
(1-3-1) Al-based catalyst As the above-mentioned Al-based catalyst, those described in [0013] to [0148] of WO2011 / 040161 ([0021] to [0123] of US2012 / 0183761) The contents described in these publications are incorporated in the present specification.
Although there is no restriction | limiting in particular as a method of superposing | polymerizing a polyester resin using the above-mentioned Al type catalyst, Specifically, [0091]-[0094] of WO2012 / 008488 ([0144] of US2013 / 0112271) To [0153]) can be polymerized according to these publications, and the contents described in these publications are incorporated herein.
Such Al-based catalysts include, for example, [0052] to [0054], [0099] to [0104] of JP2012-122051 ([0045] to [0047], [0091] of WO2012 / 029725. To [0096]) can be prepared according to these publications, and the contents described in these publications are incorporated herein. The amount of the Al-based catalyst is preferably 3 to 80 ppm, more preferably 5 to 60 ppm, and still more preferably 5 to 40 ppm as the amount of Al element with respect to the mass of the polyester resin.

(1-3-2) Sb-based catalyst:
As the aforementioned Sb-based catalyst, those described in JP-A-2012-41519, [0050], [0052] to [0054] can be used.
Although there is no restriction | limiting in particular as a method of superposing | polymerizing a polyester resin using the above-mentioned Sb type catalyst, Specifically, it can superpose | polymerize according to [0086]-[0087] of WO2012 / 157762.

(1-4) Additive:
It is also preferable to add a known additive to the uniaxially oriented polyester film of the present invention. Examples thereof include ultraviolet absorbers, particles, lubricants, antiblocking agents, heat stabilizers, antioxidants, antistatic agents, light resistance agents, impact resistance improvers, lubricants, dyes, pigments and the like. However, since the polyester film generally requires transparency, it is preferable to keep the additive amount to a minimum.

(1-4-1) Ultraviolet (UV) absorber:
The uniaxially oriented polyester film of the present invention may contain an ultraviolet absorber in order to prevent the liquid crystal of the liquid crystal display from being deteriorated by ultraviolet rays. The ultraviolet absorber is not particularly limited as long as it is a compound having ultraviolet absorbing ability and can withstand the heat applied in the production process of the polyester film.
As the ultraviolet absorber, there are an organic ultraviolet absorber and an inorganic ultraviolet absorber. From the viewpoint of transparency, an organic ultraviolet absorber is preferable. Those described in [0057] of WO2012 / 157762 and cyclic iminoester-based ultraviolet absorbers described later can be used.

  Examples of the cyclic imino ester-based ultraviolet absorber include, but are not limited to, 2-methyl-3,1-benzoxazin-4-one, 2-butyl-3,1-benzoxazine-4, for example. -One, 2-phenyl-3,1-benzoxazin-4-one, 2- (1- or 2-naphthyl) -3,1-benzoxazin-4-one, 2- (4-biphenyl) -3, 1-benzoxazin-4-one, 2-para-nitrophenyl-3,1-benzoxazin-4-one, 2-meta-nitrophenyl-3,1-benzoxazin-4-one, 2-para-benzoyl Phenyl-3,1-benzoxazin-4-one, 2-para-methoxyphenyl-3,1-benzoxazin-4-one, 2-ortho-methoxyphenyl-3,1-benzoxazine 4-one, 2-cyclohexyl-3,1-benzoxazin-4-one, 2-para- (or meta-) phthalimidophenyl-3,1-benzoxazin-4-one, N-phenyl-4- (3 , 1-Benzoxazin-4-on-2-yl) phthalimide, N-benzoyl-4- (3,1-benzoxazin-4-on-2-yl) aniline, N-benzoyl-N-methyl-4- (3,1-benzoxazin-4-one-2-yl) aniline, 2- (para- (N-methylcarbonyl) phenyl) -3,1-benzoxazin-4-one, 2,2′-bis ( 3,1-benzoxazin-4-one), 2,2′-ethylenebis (3,1-benzoxazin-4-one), 2,2′-tetramethylenebis (3,1-benzoxazine-4-one) on) 2,2′-Decamethylenebis (3,1-benzoxazin-4-one, 2,2 ′-(1,4-phenylene) bis (4H-3,1-benzoxazin-4-one) [ 2,2′-para-phenylenebis (3,1-benzoxazin-4-one)], 2,2′-meta-phenylenebis (3,1-benzoxazin-4-one), 2,2 '-(4,4'-diphenylene) bis (3,1-benzoxazin-4-one), 2,2'-(2,6- or 1,5-naphthylene) bis (3,1-benzoxazine- 4-one), 2,2 ′-(2-methyl-para-phenylene) bis (3,1-benzoxazin-4-one), 2,2 ′-(2-nitro-para-phenylene) bis (3 , 1-Benzoxazin-4-one), 2,2 ′-(2-chloro -Para-phenylene) bis (3,1-benzoxazin-4-one), 2,2 '-(1,4-cyclohexylene) bis (3,1-benzoxazin-4-one), 1,3, 5-tri (3,1-benzoxazin-4-on-2-yl) benzene, 1,3,5-tri (3,1-benzoxazin-4-on-2-yl) naphthalene, 2,4, 6-tri (3,1-benzoxazin-4-on-2-yl) naphthalene, 2,8-dimethyl-4H, 6H-benzo (1,2-d; 5,4-d ′) bis (1, 3) -Oxazine-4,6-dione, 2,7-dimethyl-4H, 9H-benzo (1,2-d; 4,5-d ′) bis (1,3) -oxazine-4,9-dione 2,8-diphenyl-4H, 8H-benzo (1,2-d; 5,4-d ′) bis (1,3 -Oxazine-4,6-dione, 2,7-diphenyl-4H, 9H-benzo (1,2-d; 4,5-d ') bis (1,3) -oxazine-4,6-dione, 6 , 6′-bis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,6′-bis (2-ethyl-4H, 3,1-benzoxazin-4-one), 6 , 6′-bis (2-phenyl-4H, 3,1-benzoxazin-4-one), 6,6′-methylenebis (2-methyl-4H, 3,1-benzoxazin-4-one), 6 , 6′-methylenebis (2-phenyl-4H, 3,1-benzoxazin-4-one), 6,6′-ethylenebis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,6′-ethylenebis (2-phenyl-4H, 3,1-benzoxa -4-one), 6,6′-butylenebis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,6′-butylenebis (2-phenyl-4H, 3,1-benzo) Oxazin-4-one), 6,6′-oxybis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,6′-oxybis (2-phenyl-4H, 3,1-benzo) Oxazin-4-one), 6,6′-sulfonylbis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,6′-sulfonylbis (2-phenyl-4H, 3,1) -Benzoxazin-4-one), 6,6'-carbonylbis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,6'-carbonylbis (2-phenyl-4H, 3 , 1-Benzoxazin-4-one) 7,7′-methylenebis (2-methyl-4H, 3,1-benzoxazin-4-one), 7,7′-methylenebis (2-phenyl-4H, 3,1-benzoxazin-4-one) 7,7′-bis (2-methyl-4H, 3,1-benzoxazin-4-one), 7,7′-ethylenebis (2-methyl-4H, 3,1-benzoxazin-4-one) ), 7,7′-oxybis (2-methyl-4H, 3,1-benzoxazin-4-one), 7,7′-sulfonylbis (2-methyl-4H, 3,1-benzoxazine-4-one) ON), 7,7′-carbonylbis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,7′-bis (2-methyl-4H, 3,1-benzoxazine-4) -One), 6,7'-bis (2-phenyl-4H, , 1-Benzoxazin-4-one, 6,7′-methylenebis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,7′-methylenebis (2-phenyl-4H, 3, 1-benzoxazin-4-one) and the like.

  Among the above compounds, when considering the color tone, a benzoxazinone-based compound which is difficult to be yellowed is preferably used. As an example thereof, a compound represented by the following general formula (1) is more preferably used. It is done.

In the general formula (1), R represents a divalent aromatic hydrocarbon group, and X ¹ and X ² are each independently selected from hydrogen or the following functional group group, but are not necessarily limited thereto. Absent.

  Functional group: alkyl group, aryl group, heteroaryl group, halogen, alkoxyl group, aryloxy group, hydroxyl group, carboxyl group, ester group, nitro group.

  Among the compounds represented by the general formula (1), 2,2 ′-(1,4-phenylene) bis (4H-3,1-benzoxazin-4-one) is particularly preferable in the present invention.

  The amount of the ultraviolet absorber to be contained in the uniaxially oriented polyester film of the present invention is usually 10.0% by mass or less, preferably 0.3 to 3.0% by mass. When an ultraviolet absorber in an amount exceeding 10.0% by mass is contained, the ultraviolet absorber may bleed out on the surface, which may cause deterioration of surface functionality such as adhesion deterioration.

In addition, in the case of the uniaxially oriented polyester film of the present invention having a multilayer structure, a film having at least a three-layer structure is preferable, and the ultraviolet absorber is preferably blended in the intermediate layer. By blending an ultraviolet absorber in the intermediate layer, this compound can be prevented from bleeding out to the film surface, and as a result, characteristics such as film adhesion can be maintained.
For these formulations, the master batch method described in [0050] to [0051] of WO2011 / 162198 can be used.

(1-4-2) Other additives In the uniaxially oriented polyester film of the present invention, other additives may be used, for example, those described in [0058] of WO2012 / 157762 can be used, The contents described in these publications are incorporated herein.

[Method for producing uniaxially oriented polyester film]
The method for producing a uniaxially oriented polyester film of the present invention is a method for producing a uniaxially oriented polyester film of the present invention using a tenter type stretching apparatus having clips that run along a pair of rails installed on both sides of a film conveyance path. A step of transversely stretching while gripping the substantially unstretched polyester film with the clip, and a heat setting step of heating the polyester film after the transverse stretch to the maximum temperature in the tenter, The transverse stretch ratio in the transverse stretching step is controlled in the range of 3.3 times to 4.8 times, and the film surface temperature at the start of stretching in the transverse stretching step is in the range of 80 ° C. to 95 ° C. The film surface temperature at the end of stretching is maintained at 90 ° C. or more and 105 ° C. or less, and the film surface temperature is gradually increased from the start of the stretching to the end of the stretching. So, the thickness of the uniaxially oriented polyester film described above is 20μm or more 60μm or less.
Here, “substantially unstretched polyester film” means a polyester film having a refractive index in the MD direction and TD direction of 1.590 or less. For example, it is slightly stretched in the MD direction. However, a polyester film having a refractive index in the MD direction and TD direction of 1.590 or less is also included in the substantially unstretched polyester film.
Hereinafter, the preferable aspect of the manufacturing method of the uniaxially-oriented polyester film of this invention is demonstrated.

<Melting and kneading>
The substantially unstretched polyester film is preferably formed into a film by melt-extruding a polyester resin.
It is preferable to dry the polyester resin or the master batch of the polyester resin and additive produced by the above-described master batch method to a moisture content of 200 ppm or less, and then introduce the melt into a single or twin screw extruder and melt it. At this time, in order to suppress degradation of the polyester, it is also preferable to melt in nitrogen or vacuum. Detailed conditions can be carried out according to these publications with the aid of Patent Nos. 4926661 [0051] to [0052] (US2013 / 0100378 [0085] to [0086]), and are described in these publications. The contents are incorporated herein. Furthermore, it is also preferable to use a gear pump in order to increase the delivery accuracy of the molten resin (melt). It is also preferable to use a 3 μm to 20 μm filter for removing foreign substances.

<Extrusion, coextrusion>
Although it is preferable to extrude the melt containing the polyester resin melt-kneaded from the die, it may be extruded as a single layer or as a multilayer. When extruding in multiple layers, for example, a layer containing an ultraviolet grade agent (UV agent) and a layer not containing it may be laminated. In addition to suppressing deterioration, it is preferable to suppress bleeding out of the UV agent.
The bleed-out UV agent is undesirably easily transferred to a pass roll in the film-forming process, increasing the coefficient of friction between the film and the roll, and causing scratches.
When the polyester film is produced by being extruded in multiple layers, the preferred inner layer thickness (ratio to the total layer) of the resulting polyester film is preferably 50% or more and 95% or less, more preferably 60% or more and 90% or less, Preferably they are 70% or more and 85% or less. Such lamination can be performed by using a feed block die or a multi-manifold die.

<Cast>
According to [0059] of JP-A-2009-269301, it is preferable to extrude the melt extruded from the die onto a casting drum and solidify by cooling to obtain the aforementioned substantially unstretched polyester film (raw fabric).
In the production method of the present invention, the refractive index in the longitudinal direction of the aforementioned substantially unstretched polyester film is preferably 1.590 or less, more preferably 1.585 or less, and further preferably 1.580 or less.
In the production method of the present invention, the crystallinity of the substantially unstretched polyester film is preferably 5% or less, more preferably 3% or less, and further preferably 1% or less. In addition, the crystallinity degree of the above-mentioned substantially unstretched polyester film here means the crystallinity degree of the center part of a film width direction.
When adjusting the degree of crystallinity, the temperature of the end of the casting drum may be lowered, or air may be blown onto the cast drum.
The crystallinity can be calculated from the density of the film. That is, the density X (g / ^cm 3) of the film density at a crystallinity of ^{0% Y = 1.335g / cm 3} , using density Z = 1.501g / cm ³ at 100% crystalline below The crystallinity (%) can be derived from the calculation formula.
Crystallinity = {Z × (XY)} / {X × (ZY)} × 100
The density was measured according to JIS K7112.

<Formation of polymer layer (adhesive layer)>
A polymer layer (preferably an easy-adhesion layer) may be formed by coating on the substantially unstretched polyester film that has been melt-extruded before or after stretching described below.
Examples of the polymer layer include functional layers that the polarizing plate may generally have, and among them, it is preferable to form an easy adhesion layer as the polymer layer. The easy-adhesion layer can be applied by the method described in [0062] to [0070] of WO2012 / 157762.
In the present invention, the above-mentioned composition for forming an easy-adhesion layer (preferably a coating solution) contains particles, and the height at which the above-mentioned particles protrude from the surface of the above-mentioned easy-adhesion layer is as described above. It is preferable to form the easy-adhesion layer by controlling the thickness of the easy-adhesion layer and the average particle diameter of the particles so as to be equal to or greater than the thickness of the film.

<Horizontal stretching>
The production method of the present invention uses a tenter-type stretching device having a clip that travels along a pair of rails installed on both sides of a film conveyance path, and grips a substantially unstretched polyester film with the aforementioned clip. A step of transverse stretching.

There is no restriction | limiting in particular as a tenter type extending | stretching apparatus which has a clip which drive | works along a pair of rail installed in the both sides of a film conveyance path. A pair of endless rails is usually used as the pair of rails.
In addition, a clip is synonymous with a holding member.

The method for producing a uniaxially oriented polyester film of the present invention transversely stretches a substantially unstretched polyester film. The lateral stretching is performed in a direction orthogonal to the film transport direction while transporting a substantially unstretched polyester film along the film transport path.
By stretching in the transverse direction, the retardation Re in the in-plane direction can be greatly expressed. In particular, in order to achieve a polyester film satisfying the aforementioned Re and Re / Rth ranges, at least transverse stretching is performed.

  In the method for producing a uniaxially oriented polyester film of the present invention, the transverse stretching ratio in the transverse stretching step described above is controlled in the range of 3.3 times to 4.8 times. The transverse draw ratio is more preferably 3.5 times or more and 4.5 times or less, and further preferably 3.7 times or more and 4.3 times or less. If the transverse draw ratio is less than 3.3 times, Re may be insufficient. If the transverse draw ratio exceeds 4.8 times, EMD will be less than 2000 MPa or ETD / EMD will be more than 3.

  In the method for producing a uniaxially oriented polyester film of the present invention, the film surface temperature at the start of stretching in the transverse stretching step described above is maintained in the range of 80 ° C. or higher and 95 ° C. or lower. The film surface temperature at the start of stretching is more preferably from 82 ° C to 93 ° C, and still more preferably from 84 ° C to 92 ° C. If the film surface temperature at the start of stretching is less than 80 ° C., the orientation and orientation crystallization progress too much in the stretching stage, and Rth increases, and the Re / Rth ratio falls below 0.7, and the EMD falls below 2000 MPa. Or ETD / EMD exceeds 3. If the film surface temperature at the start of stretching exceeds 95 ° C., the orientation will be insufficient and spherulites will not grow, Re will not rise sufficiently, TRTD will be less than 5, and TBMD will be less than 50. .

  In the method for producing a uniaxially oriented polyester film of the present invention, the film surface temperature at the end of stretching in the transverse stretching step described above is maintained at 90 ° C. or higher and 105 ° C. or lower. The film surface temperature at the end of stretching is more preferably 92 ° C. or higher and 102 ° C. or lower, and further preferably 93 ° C. or higher and 100 ° C. or lower. When the film surface temperature at the end of stretching is below 90 ° C., orientation and orientation crystallization progress too much at the stretching stage, and Rth increases, and the Re / Rth ratio falls below 0.7, or EMD falls below 2000 MPa. Or ETD / EMD exceeds 3. When the film surface temperature at the end of stretching exceeds 105 ° C., orientation is insufficient and spherulites grow, Re does not rise sufficiently, TRTD is less than 5, and TBMD is less than 50. .

  The method for producing a uniaxially oriented polyester film of the present invention gradually increases the film surface temperature from the start of stretching to the end of stretching. The difference in film surface temperature between the end of stretching and the start of stretching is more preferably 1 ° C or higher, further preferably 3 ° C or higher, and most preferably 5 ° C or higher. If the film surface temperature is not increased from the start of stretching to the end of stretching, spherulites are more easily formed and the orientation is excessively advanced, making it impossible to achieve both Re, Re / Rth and various mechanical properties.

In the method for producing a uniaxially oriented polyester film of the present invention, in the above-described transverse stretching step, the film surface temperature in the range where the draw ratio is 1 to 2 times is preferably 80 ° C. or more and 92 ° C. or less, more preferably 82 ° C. or more and 91 ° C. or less. It is preferably 84 ° C. or higher and 91 ° C. or lower. When the film surface temperature in the range of the draw ratio of 1 to 2 is 80 ° C. or higher, the orientation and orientation crystallization do not proceed excessively in the drawing stage, Rth is hardly increased, and the Re / Rth ratio is 0.7 or more. Or EMD becomes 2000 MPa or more, or ETD / EMD becomes 3 or less. When the film surface temperature in the range of the draw ratio of 1 to 2 times is 92 ° C. or less, it is difficult to be insufficiently oriented, and it is difficult to grow a fine polyester crystal, Re is sufficiently increased, and TRTD is 5 or more. Or a TBMD of 50 or more.
In the method for producing a uniaxially oriented polyester film of the present invention, the film surface temperature in the range of a stretching ratio of 2 to 3 times is preferably 85 ° C. or higher and 97 ° C. or lower, and 86 ° C. or higher and 97 ° C. or lower is more preferable. Preferably, it is 87 degreeC or more and 96 degrees C or less. When the film surface temperature in the range of the stretching ratio of 2 to 3 is 85 ° C. or higher, the orientation and orientation crystallization do not proceed excessively in the stretching stage, and Rth is hardly increased, and the Re / Rth ratio is 0.7 or higher. Or EMD becomes 2000 MPa or more, or ETD / EMD becomes 3 or less. When the film surface temperature in the range of 2 to 3 times the draw ratio is 97 ° C. or less, it is difficult to be insufficiently oriented, it becomes difficult to grow fine polyester crystals, Re is sufficiently increased, and TRTD is 5 or more. Or a TBMD of 50 or more.
In the method for producing a uniaxially oriented polyester film of the present invention, the film surface temperature in the range of the stretching ratio of 3 times or more is preferably 90 ° C. or more and 102 ° C. or less, more preferably 92 ° C. or more and 101 ° C. or less in the above-described transverse stretching step. 93 ° C. or more and 100 ° C. or less is more preferable. When the film surface temperature in the range where the draw ratio is 3 times or more is 90 ° C. or more, the orientation and orientation crystallization do not proceed excessively in the drawing stage, Rth is hardly increased, and the Re / Rth ratio becomes 0.7 or more. Or an EMD of 2000 MPa or more, or an ETD / EMD of 3 or less. When the film surface temperature in the range where the draw ratio is 3 times or more is 102 ° C. or less, it is difficult for orientation to be insufficient, and it becomes difficult for crystals of fine polyester to grow, Re is sufficiently increased, and TRTD is 5 or more. Or TBMD is 50 or more, which is preferable.
In the production method of the uniaxially oriented polyester film of the present invention, the film surface temperature is gradually increased from the start of stretching to the end of stretching. The film surface temperature in the range where the draw ratio is 2 to 3 times and the film surface temperature in the range where the draw ratio is 3 times or more are not lower than the film surface temperature in the range where the draw ratio is small. That is, the film surface temperature in the range where the draw ratio is 2 to 3 times does not become lower than the film surface temperature in the range where the draw ratio is 1 to 2 times, and the film surface temperature in the range where the draw ratio is 3 times or more is stretched. The magnification never falls below the film surface temperature in the range of 2 to 3 times.

  As temperature control means for heating or cooling the polyester film in preheating, stretching, heat setting, heat relaxation, and cooling in the transverse stretching process, hot or cold air is blown on the polyester film, or the polyester film is temperature controlled. The surface of the possible metal plate can be contacted or the vicinity of the metal plate can be passed.

  That is, it can be achieved by gripping both ends of the film with clips and widening between the clips while heating.

<Heat fixing, thermal relaxation>
The manufacturing method of the uniaxially oriented polyester film of this invention includes the heat setting process which heats the polyester film after the above-mentioned transverse stretching to the highest temperature in the above-mentioned tenter.
After stretching, a heat treatment called “heat setting” is performed to promote crystallization. By performing at a temperature exceeding the stretching temperature, crystallization can be promoted and the strength of the film can be increased.
In heat setting, volume shrinks due to crystallization.
As a heat fixing method, several slits for sending hot air to the extending portion are provided in parallel to the width direction. This can be achieved by making the temperature of the gas blown out from the slit higher than the stretched portion.
Further, a heat source (IR heater, halogen heater, etc.) may be installed near the drawing (part) exit to raise the temperature.

  The maximum film surface temperature in the heat setting and heat relaxation steps described above is preferably 130 ° C. or higher and 190 ° C. or lower, more preferably 140 ° C. or higher and 180 ° C. or lower, and further preferably 150 ° C. or higher and 175 ° C. or lower. It is preferable that the maximum film surface temperature in the above-described heat setting and the above-described heat relaxation step is 130 ° C. or more because the heat shrinkage rate can be reduced. When the maximum film surface temperature in the above-described heat setting and heat relaxation step is 190 ° C. or less, Rth is unlikely to increase, and the Re / Rth ratio is not excessively decreased.

The method for producing a uniaxially oriented polyester film of the present invention preferably includes a heat relaxation step of heating the above-mentioned heat-fixed polyester film and reducing the length of at least the MD direction of the above-mentioned polyester film. In other words, before releasing the polyester film after transverse stretching from the clip, a heat fixing step of heating the polyester film after transverse stretching to the maximum temperature in the tenter, and after the heat fixing step, It is preferable to include a thermal relaxation step of narrowing the distance between the pair of rails while heating the polyester film. The heat relaxation step is not strictly limited to an embodiment performed after the heat setting step, and the heat setting step and the heat relaxation step may be performed simultaneously. In the case where the heat setting step and the heat relaxation step are performed simultaneously, it is preferable that the heat setting step is performed up to the time when the temperature is heated to the maximum temperature in the tenter, and the heat relaxation is continued at a temperature not exceeding the maximum temperature in the tenter.
After the heat setting step described above, it is preferable to relax (shrink the film) simultaneously with the heat treatment, and it is preferable to perform at least one of TD (transverse direction) and MD (vertical direction).
Lateral relaxation can be achieved by reducing the width of the widened click.
Such relaxation can be achieved, for example, by using a pantograph-like chuck for the tenter, reducing the interval between the pantographs, and driving the click on the electromagnet to reduce the speed.
In the thermal relaxation process described above, it is possible to suppress the occurrence of scratches in the uniaxially oriented polyester film by setting the relaxation rate in the MD direction, which is the ratio of reducing the length in the MD direction, of the heat-fixed polyester film to 1 to 7%. It is preferable from a viewpoint to do, 2 to 6% is more preferable, and 3 to 5% is still more preferable. When the relaxation rate in the MD direction is 1% or more, the thermal shrinkage rate in the MD direction can be reduced and wrinkles are less likely to occur. When the relaxation rate in the MD direction is 7% or less, it is preferable that slackness does not easily occur in the MD direction during the relaxation process, and it is difficult to cause a planar failure.
From the viewpoint of suppressing the occurrence of scratches on the uniaxially oriented polyester film, the relaxation rate in the TD direction, which is the ratio of reducing the length in the TD direction of the heat-fixed polyester film, is preferably 0 to 6%. 4% is more preferable, and 1-3% is still more preferable. It is preferable that the relaxation rate in the TD direction is 6% or less because it is difficult for slack to occur in the TD direction during the relaxation process, and it is difficult to cause a planar failure.

  The relaxation temperature in the TD direction (lateral direction) is preferably in the range of the above-mentioned heat setting temperature, and heat setting is possible as long as the heat setting for heating the above-mentioned laterally stretched polyester film to the maximum temperature in the above tenter can be performed. Or the same temperature (ie, even if the maximum temperature in the tenter is reached).

  By the above stretching and heat setting, Re, Rth and Re / Rth of the uniaxially oriented polyester film of the present invention can be easily achieved. That is, it is easy to form the uniaxially oriented polyester film of the present invention that exhibits the effect of reducing rainbow unevenness by stretching and heat setting by these methods.

<Cooling>
The production method of the present invention preferably includes a step of cooling the heat-fixed polyester film before releasing the heat-fixed polyester film from the clip. After stretching, preferably after heat setting, the polyester film is cooled before being released from the clip, and this tends to lower the temperature of the clip when the polyester film after transverse stretching is released from the clip. From the standpoint of
The cooling temperature of the polyester film after heat setting is preferably 80 ° C. or less, more preferably 70 ° C. or less, and particularly preferably 60 ° C. or less.
Specific examples of the method for cooling the polyester film after heat setting described above include a method in which cold air is applied to the polyester film.

<Release film from clip>
In the production method of the present invention, the above-mentioned polyester film after transverse stretching is released from the above-mentioned clip.

  It is preferable to control the temperature of the surface of the polyester film when the polyester film is detached from the gripping member in the range of 40 to 140 ° C. The temperature of the surface of the polyester film when the polyester film is detached from the holding member is more preferably 50 ° C. or higher and 120 ° C. or lower, and further preferably 60 ° C. or higher and 100 ° C. or lower.

  In the method for producing a uniaxially oriented polyester film of the present invention, the thickness of the uniaxially oriented polyester film is 20 μm or more and 60 μm or less, more preferably 25 μm or more and 55 μm or less after completion of film formation (after the transverse stretching and releasing step from the clip). 30 μm or more and 50 μm or less is more preferable. The reason why this range is preferable is the same as the reason why the film thickness of the uniaxially oriented polyester film of the present invention is preferably within this range.

<Recovery of film, slit, winding>
After the transverse stretching and the step of releasing from the clip, the film is trimmed, slit, and thickened as necessary, and wound for recovery.
In the production method of the present invention, the film width after being released from the clip is preferably 0.8 to 6 m from the viewpoint of efficiently securing the film product width and the apparatus size is not excessive, and is 1 to 5 m. Is more preferable and it is especially preferable that it is 1-4 m. An optical film requiring accuracy is usually formed with a thickness of less than 3 m, but in the present invention, it is preferable to form a film with the above-mentioned width.
In addition, the film formed into a wide film may be slit to preferably 2 or more, 6 or less, more preferably 2 or more and 5 or less, and still more preferably 3 or more and 4 or less, and then wound.

Moreover, after slitting, it is preferable to process the thickness at both ends (providing knurling).
The winding is preferably performed at a diameter of not less than 1000 m and not more than 10,000 m on a core having a diameter of 70 mm or more and 600 mm or less. Winding tension per cross-sectional area of the film is preferably 3~30kgf / cm ^2, more preferably 5~25kgf / cm ^2, more preferably from 7~20kgf / cm ^2. The thickness of the wound film is the same as [0049] of Japanese Patent No. 4926661. It is also preferable to bond a masking film before winding.

[Hard coat film]
The hard coat film of the present invention is a hard coat film in which a hard coat layer is laminated on at least one surface of the uniaxially oriented polyester film of the present invention. The uniaxially oriented polyester film of the present invention can be used for a hard coat film.
The hard coat layer may be formed by either a wet coating method or a dry coating method (vacuum film formation), but is preferably formed by a wet coating method having excellent productivity.
As the hard coat layer, for example, JP 2013-45045 A, JP 2013-43352 A, JP 2012-232459 A, JP 2012-128157 A, JP 2011-131409 A, JP JP2011-131404A, JP2011-126162A, JP2011-75705A, JP2009-286981, JP2009-263567, JP2009-75248, JP2007-. No. 164206, JP-A No. 2006-96811, JP-A No. 2004-75970, JP-A No. 2002-156505, JP-A No. 2001-272503, WO12 / 018087, WO12 / 098967, WO12 / 0886659, WO11 / Described in 105594 The can be used.

[Anti-scattering film]
The scattering prevention film of the present invention is a scattering prevention film in which an adhesive layer is laminated on at least one surface of the uniaxially oriented polyester film of the present invention. The uniaxially oriented polyester film of the present invention can be used for a scattering prevention film. The scattering prevention film is preferably formed by laminating a hard coat layer and an adhesive layer on a uniaxially oriented polyester film.
The adhesive layer may be formed by either a wet coating method or a dry coating method. To form the adhesive layer, an acrylic adhesive composition such as a solvent-based acrylic polymer, a solvent-based acrylic syrup, a solvent-free acrylic syrup, or a solvent-free urethane acrylate can be used.

[Antireflection film]
The antireflection film of the present invention is an antireflection film in which an antiglare layer is laminated on at least one surface of the uniaxially oriented polyester film of the present invention. The uniaxially oriented polyester film of the present invention can be used for an antireflection film.
The antiglare layer may be formed by either a wet coating method or a dry coating method. For the antiglare layer, JP-A-2014-059334, JP-A-2014-026122, JP-A-2014-016602, JP-A-2014-016476, JP-A-2013-246371, JP-A-2014-041206, JP-A-2014-032317, JP-A The anti-glare layer described in 2014-026123 and Unexamined-Japanese-Patent No. 2014-010316 can be used.

[Sensor film for touch panel]
The sensor film for a touch panel of the present invention includes the uniaxially oriented polyester film of the present invention. The uniaxially oriented polyester film of the present invention can be used for a sensor film for a touch panel. The sensor film for a touch panel is preferably formed by laminating a hard coat layer and a transparent conductive layer on a uniaxially oriented polyester film.
As a general method for forming the transparent conductive layer, there are a PVD (Physical Vapor Deposition) method such as a sputtering method, a vacuum deposition method, an ion plating method, a CVD (Chemical Vapor Deposition) method, a coating method, a printing method, and the like. is there. The material for forming the transparent conductive layer is not particularly limited, and examples thereof include indium / tin composite oxide (ITO), tin oxide, copper, silver, aluminum, nickel, chromium, and the like. May be formed in an overlapping manner. In addition, the transparent conductive layer may be provided with an undercoat layer for improving transparency and optical characteristics before forming the transparent conductive layer. In order to further improve the adhesion, a metal layer made of a single metal element or an alloy of two or more metal elements may be provided between the undercoat layer and the uniaxially oriented polyester film. It is desirable to use a metal selected from the group consisting of silicon, titanium, tin and zinc for the metal layer.

[Touch panel]
The touch panel of the present invention comprises at least one of the uniaxially oriented polyester film of the present invention, the hard coat film of the present invention, the anti-scattering film of the present invention, the antireflection film of the present invention, and the sensor film for touch panels of the present invention. The uniaxially oriented polyester film of the present invention can be used in a touch panel.
The touch panel of the present invention has a liquid crystal panel and a polarizing plate disposed on the exit surface of the liquid crystal panel, and includes the uniaxially oriented polyester film, the hard coat film, the anti-scattering film, and the reflection described above. It is preferable that at least one slow axis of the prevention film and the sensor film for a touch panel described above is arranged in a range of 45 ± 25 ° with respect to the absorption axis of the polarizing plate, and more preferably 45 ± 15 ° or less. Preferably, 45 ± 10 ° or less is more preferable. When the angle is within the range of 45 ± 25 °, a blackout phenomenon (a phenomenon in which an object such as a liquid crystal panel viewed through the sunglasses looks dark) hardly occurs when wearing polarized sunglasses.
There is no restriction | limiting in particular about a liquid crystal panel and the polarizing plate arrange | positioned at the output surface of the above-mentioned liquid crystal panel, A well-known liquid crystal panel and a polarizing plate can be used.
There is no restriction | limiting in particular in the touchscreen of this invention, According to the objective, it can select suitably, For example, a surface capacitive touch panel, a projection capacitive touch panel, a resistive touch panel etc. are mentioned. The touch panel includes a so-called touch sensor and a touch pad. The layer structure of the touch panel sensor electrode part in the touch panel is a bonding method in which two transparent electrodes are bonded, a method in which transparent electrodes are provided on both surfaces of a single substrate, a single-sided jumper or a through-hole method, or a single-area layer method. But you can. In addition, the projected capacitive touch panel is preferably AC driven rather than DC driven, and more preferably is a drive system that requires less time to apply voltage to the electrodes.

The features of the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.
Unless otherwise specified, “part” is based on mass.

[Example 1]
<Synthesis of raw material polyester>
(Raw material polyester 1)
As shown below, terephthalic acid and ethylene glycol are directly reacted to distill off water, esterify, and then, using a direct esterification method in which polycondensation is performed under reduced pressure, raw polyester 1 ( Sb catalyst system PET) was obtained.

(1) Esterification reaction In a first esterification reactor, 4.7 tons of high-purity terephthalic acid and 1.8 tons of ethylene glycol are mixed over 90 minutes to form a slurry, and continuously at a flow rate of 3800 kg / h. It supplied to the 1st esterification reaction tank. Further, an ethylene glycol solution of antimony trioxide was continuously supplied, and the reaction was carried out at a reaction vessel temperature of 250 ° C. with stirring and an average residence time of about 4.3 hours. At this time, antimony trioxide was continuously added so that the amount of Sb added was 150 ppm in terms of element.

  This reaction product was transferred to a second esterification reaction vessel, and reacted with stirring at a temperature in the reaction vessel of 250 ° C. and an average residence time of 1.2 hours. To the second esterification reaction tank, an ethylene glycol solution of magnesium acetate and an ethylene glycol solution of trimethyl phosphate are continuously supplied so that the added amount of Mg and the added amount of P are 65 ppm and 35 ppm in terms of element, respectively. did.

(2) the polycondensation reaction above-obtained esterification reaction product supplied to the first polycondensation reaction vessel continuously stirring, the reaction temperature 270 ° C., the reaction vessel pressure 20 torr (2.67 × 10 ^{- 3} MPa) and polycondensation with an average residence time of about 1.8 hours.

Further, it was transferred to the second double condensation reaction tank, and while stirring in this reaction tank, the reaction tank temperature was 276 ° C., the reaction tank pressure was 5 torr (6.67 × 10 ⁻⁴ MPa), and the residence time was about 1.2 hours. The reaction (polycondensation) was performed under the conditions.

Subsequently, it was further transferred to the third triple condensation reaction tank. In this reaction tank, the reaction tank temperature was 278 ° C., the reaction tank internal pressure was 1.5 torr (2.0 × 10 ⁻⁴ MPa), and the residence time was 1.5 hours. The reaction product (polyethylene terephthalate (PET)) was obtained by reaction (polycondensation) under the following conditions.

  Next, the obtained reaction product was discharged into cold water in a strand form and immediately cut to prepare polyester pellets (cross section: major axis: about 4 mm, minor axis: about 2 mm, length: about 3 mm).

  The obtained polymer had IV = 0.63 (hereinafter abbreviated as PET1). This polymer was designated as raw material polyester 1.

<Manufacture of polyester film>
-Film forming process-
The raw material polyester 1 (PET1) was dried to a moisture content of 20 ppm or less and then charged into the hopper 1 of a single-screw kneading extruder 1 having a diameter of 50 mm. The raw material polyester 1 was melted at 300 ° C. and extruded from a die through a gear pump and a filter (pore diameter: 20 μm) under the following extrusion conditions.
The molten resin was extruded from the die under the conditions that the pressure fluctuation was 1% and the temperature distribution of the molten resin was 2%. Specifically, the back pressure was increased by 1% with respect to the average pressure in the barrel of the extruder, and the piping temperature of the extruder was heated at a temperature 2% higher than the average temperature in the barrel of the extruder.
The molten resin extruded from the die was extruded onto a cooling cast drum set at a temperature of 25 ° C., and was brought into close contact with the cooling cast drum using an electrostatic application method. It peeled using the peeling roll arrange | positioned facing the cooling cast drum, and the unstretched polyester film 1 was obtained.

  The obtained unstretched polyester film 1 had an intrinsic viscosity IV = 0.62, a refractive index in the longitudinal direction of 1.573, and a crystallinity of 0.2%.

IV is an unstretched polyester film 1 dissolved in a 1,1,2,2-tetrachloroethane / phenol (= 2/3 [mass ratio]) mixed solvent, and the solution viscosity at 25 ° C. in this mixed solvent. I asked for it.
The refractive index of the unstretched polyester film was measured by the following method.
Using two polarizing plates, the orientation axis direction of the unstretched polyester film was determined, and a 4 cm × 2 cm rectangle was cut out so that the orientation axis directions were perpendicular to each other, and used as a measurement sample. For this sample, the biaxial refractive index (Nx, Ny) perpendicular to each other and the refractive index (Nz) in the thickness direction were determined by an Abbe refractometer (NAR-4T, measurement wavelength 589 nm, manufactured by Atago Co., Ltd.).
The crystallinity of the unstretched polyester film was measured by the following method.
The crystallinity can be calculated from the density of the film. That is, the density X (g / ^cm 3) of the film, density 1.335 g / cm ³ in crystallinity 0%, using density 1.501g / cm ³ at 100% crystalline crystal from the following formula The degree of conversion (%) can be derived.
Crystallinity = {Z × (XY)} / {X × (ZY)} × 100
The density was measured according to JIS K7112.

-Formation of an easy adhesion layer-
The following compounds were mixed in the following ratio to prepare a coating liquid H1 for an easy adhesion layer.

Coating liquid H1 for easy adhesion layer
Polyester resin: (IC) 60 parts by mass Acrylic resin: (II) 25 parts by mass Melamine compound: (VIB) 10 parts by mass Particles: (VII) 5 parts by mass Details of the compounds used are shown below.
Polyester resin: (IC)
Polyester resin sulfonic acid aqueous dispersion monomer composition copolymerized with monomers of the following composition: (acid component) terephthalic acid / isophthalic acid / 5-sodium sulfoisophthalic acid // (diol component) ethylene glycol / 1,4- Butanediol / diethylene glycol = 56/40/4 // 70/20/10 (mol%)

Acrylic resin: (II)
Aqueous dispersion of acrylic resin polymerized with monomers of the following composition Ethyl acrylate / n-butyl acrylate / methyl methacrylate / N-methylol acrylamide / acrylic acid = 65/21/10/2/2 (mass%) emulsion polymer ( Emulsifier: Anionic surfactant)
Urethane resin: (IIIB)
400 parts by weight of a polycarbonate polyol composed of 1,6-hexanediol and diethyl carbonate having a number average molecular weight of 2000, 10.4 parts by weight of neopentyl glycol, 58.4 parts by weight of isophorone diisocyanate, 74.3 parts by weight of dimethylol butanoic acid. An aqueous dispersion of urethane resin obtained by neutralizing a prepolymer consisting of parts by mass with triethylamine and extending the chain with isophoronediamine.
Melamine compound: (VIB) Hexamethoxymethyl melamine particles: (VII) Silica sol having an average particle diameter of 150 nm (average particle diameter means primary average particle diameter, that is, average value of primary particle diameter. As described).

-Application of easy adhesion layer to both sides of polyester film-
Applying the coating liquid H1 for the easy adhesion layer on one side of the unstretched polyester film 1 using a wire bar while adjusting the stretched coating film thickness to 50 nm by a bar coating method using a wire bar. did.
The height at which the particles protrude from the surface of the easy-adhesion layer was determined using VHX-5000 manufactured by Keyence Corporation at five points in the 1 mm square easy-adhesion layer, and the average value was calculated. The results are listed in the table below.

-Transverse stretching process-
The unstretched polyester film 1 was guided to a tenter (transverse stretching machine), and was stretched laterally by the following method and conditions while holding the end of the film with a clip.

(Preheating part)
Heating was performed with hot air so that the film surface temperature at the stretching start point was 89 ° C.
The film surface temperature at the starting point of stretching is the position of the central part in the film width direction at the point of starting stretching, a radiation thermometer (manufactured by Hayashi Denko, model number: RT61-2, used at an emissivity of 0.95). It was measured by.

(Extension part)
While preheated unstretched polyester film 1 was heated with hot air, it was stretched in the width direction using a tenter under the following conditions.
In addition, the film surface temperature at each stretching ratio is the position of the central portion in the film width direction at each stretching ratio, using a radiation thermometer (manufactured by Hayashi Denko, model number: RT61-2, emissivity 0.95) ).
<Condition>
-Lateral draw ratio: 4.1 times and film surface temperature at the time of 2 times drawing: 90 ° C
-Film surface temperature at the time of 3 times stretching: 94 ° C
-Film surface temperature at the end of stretching: 95 ° C

(Heat fixing part and heat relaxation part)
Subsequently, hot fixing from the up-down direction was applied to the film from the hot air blowing nozzle to the film, and heat fixation and heat relaxation treatment were performed while controlling the film surface temperature of the polyester film within the following range.
<Condition>
Maximum film surface temperature (heat setting temperature): 168 ° C
-Thermal relaxation rate: MD direction 4%, TD direction 1.5%

(Cooling section)
Next, the film was cooled by applying cold air from above and below to the film from a cold air blowing nozzle. The film was cooled so that the film surface temperature when the film was released from the tenter clip was 40 ° C.
In addition, the film surface temperature measured the position of the center part of a film width direction with the radiation thermometer (The Hayashi Denko make, model number: RT61-2, used by the emissivity 0.95).

(Recovery of film)
After cooling and releasing the film from the clip, both ends of the polyester film were trimmed by 20 cm. The film width after trimming was 2 m. Then, after extruding (knurling) with a width of 10 mm at both ends, a film having a length of 10,000 m was wound up in a roll form with a tension of 18 kg / m.
As described above, a uniaxially oriented polyester film of Example 1 having a thickness of 39 μm wound in a roll form was produced.

[Examples 2 to 8, 10 and Comparative Examples 1 to 5]
In Example 1, as described in the following table, the transverse stretching ratio, the transversely stretched film temperature (film surface temperature), the highest reached film surface temperature during heat setting / relaxation, the MD relaxation rate, the TD relaxation rate, the film thickness, and the particles A uniaxially oriented polyester film of each example and comparative example was produced in the same manner as in Example 1 except that the size (organosilica sol manufactured by Nissan Chemical Industries, Ltd., primary average particle size 60 nm) was changed.

[Example 9, Comparative Example 6]
A uniaxially oriented polyester film of Example 9 was produced in the same manner as Example 1 except that the easy adhesion layer was not provided.
In addition, as described in the following table, the transverse stretch ratio, the transverse stretch film temperature (film surface temperature), the maximum reached film surface temperature during heat setting / relaxation, the MD relaxation rate, the TD relaxation rate, and the film thickness are changed. A uniaxially oriented polyester film of Comparative Example 6 was produced in the same manner as in Example 1 except that the easy adhesion layer was not provided. In Comparative Example 6, a uniaxially oriented polyester film was produced by a similar method based on the description in Example 2 of JP2012-230390A.

[Film measurement results]
<Measurement of film thickness>
The thicknesses of the obtained polyester films of each Example and Comparative Example were determined as follows.
Using a contact-type film thickness meter (manufactured by Anritsu Co., Ltd.) for the polyester film of each example and comparative example, 50 points were sampled at equal intervals over 0.5 m in the longitudinally stretched direction (longitudinal direction). After sampling 50 points at equal intervals (50 equal parts in the width direction) over the entire width of the film in the film width direction (direction perpendicular to the longitudinal direction), the thicknesses of these 100 points were measured. The average thickness of these 100 points was determined and used as the thickness of the polyester film. The results are shown in Table 2 below.

<Re, Rth, Re / Rth ratio>
In-plane retardation Re is the product of the biaxial refractive index anisotropy (ΔNxy = | Nx−Ny |) on the film and the film thickness d (nm) (ΔNxy × d). It is a parameter defined by the above and is a scale showing optical isotropy and anisotropy. The biaxial refractive index anisotropy (ΔNxy) was determined by the following method. Using two polarizing plates, the orientation axis direction of the film was determined, and a 4 cm × 2 cm rectangle was cut out so that the orientation axis directions were perpendicular to each other, and used as a measurement sample. For this sample, the biaxial refractive index (Nx, Ny) perpendicular to each other and the refractive index (Nz) in the thickness direction were determined by an Abbe refractometer (NAGO-4T, measurement wavelength 589 nm, manufactured by Atago Co., Ltd.). The absolute value of the refractive index difference (| Nx−Ny |) was defined as the refractive index anisotropy (ΔNxy). The thickness d (nm) of the film was measured using an electric micrometer (manufactured by Fine Reef, Millitron 1245D), and the unit was converted to nm. Retardation (Re) was determined from the product (ΔNxy × d) of refractive index anisotropy (ΔNxy) and film thickness d (nm).
Thickness direction retardation means film thickness d in two birefringences ΔNxz (= | Nx−Nz |) and ΔNyz (= | Ny−Nz |) when viewed from the cross section in the film thickness direction. It is a parameter indicating the average retardation obtained by multiplying. Thickness direction retardation is obtained by calculating Nx, Ny, Nz and film thickness d (nm) by the same method as the measurement of retardation, and calculating an average value of (ΔNxz × d) and (ΔNyz × d). (Rth) was determined.
From the Re and Rth obtained, the Re / Rth ratio was calculated.
The results are shown in Table 2 below.

<Measurement of MD elastic modulus EMD>
The MD elastic modulus EMD of the film was measured according to the measurement method of JIS K 7127.
At the center position in the film width direction, a test piece E1 was cut out with a size of 150 mm in the MD direction and 10 mm in the TD direction.
The specimen E1 was subjected to a tensile test using a strograph R2 manufactured by Toyo Seiki Seisakusho. The distance between chucks was 100 mm, and the tensile speed was 10 mm / min. This test was repeated 5 times, and the average value of the obtained tensile elastic modulus was defined as MD elastic modulus EMD.
The results are shown in Table 2 below.

<Measurement of TD elastic modulus TMD>
The TD elastic modulus ETD of the film was measured according to the measurement method of JIS K 7127.
At the center position in the film width direction, a test piece E2 was cut out with a size of 150 mm in the TD direction and 10 mm in the MD direction.
The specimen E2 was subjected to a tensile test using a strograph R2 manufactured by Toyo Seiki Seisakusho. The distance between chucks was 100 mm, and the tensile speed was 10 mm / min. This test was repeated 5 times, and the average value of the obtained tensile elastic moduli was defined as TD elastic modulus ETD.
The results are shown in Table 2 below.

<ETD / EMD>
ETD / EMD was calculated from the obtained MD elastic modulus EMD and TD elastic modulus ETD.
The results are shown in Table 2 below.

<Measurement of TD tear strength TRTD>
The TD tear strength TRTD of the film was measured according to the measurement method of JIS P 8116.
At the center position in the film width direction, a test piece TR1 was cut out with a size of 51 mm in the MD direction and 64 mm in the TD direction.
The specimen TR1 was subjected to a tear test parallel to the TD direction by the Elmendorf-type tear tester method using a light load tear tester manufactured by Toyo Seiki Seisakusho. This test was repeated 10 times, and the average value of the obtained tensile strengths was defined as TD tear strength TRTD.
The results are shown in Table 2 below.

<Measurement of MD breaking strength TBMD>
The MD breaking strength TBMD of the film was measured according to the measurement method of JIS K 7127.
At the center position in the film width direction, a test piece TB1 was cut out with a size of 150 mm in the MD direction and 10 mm in the TD direction.
A tensile test was performed on the sample piece TB1 using a strograph R2 manufactured by Toyo Seiki Seisakusho. The distance between chucks was 100 mm, and the tensile speed was 10 mm / min. This test was repeated five times, and the average value of the obtained tensile breaking strengths was defined as MD breaking strength TBMD.
The results are shown in Table 2 below.

<Measurement of MD thermal shrinkage>
At the center position in the film width direction, a test piece M1 was cut out with a size of 30 mm in the TD direction and 120 mm in the MD direction.
Two reference lines were put on the sample piece M1 so as to have an interval of 100 mm in the MD direction. This was left in a heating oven at 150 ° C. for 30 minutes under no tension. After this standing, the sample piece M1 was cooled to room temperature, and the interval between the two reference lines was measured. This value was defined as A1 (unit: mm), and the numerical value calculated from the measured A1 and the formula of “100 × (100−A1) / 100” was defined as the MD thermal contraction rate.
The results are shown in Table 2 below.

<Measurement of TD thermal shrinkage>
At the center position in the film width direction, a test piece M2 was cut out with a size of 30 mm in the MD direction and 120 mm in the TD direction.
Two reference lines were placed on the sample piece M2 so as to have an interval of 100 mm in the TD direction. This was left in a heating oven at 150 ° C. for 30 minutes under no tension. After this standing, the sample piece M2 was cooled to room temperature, and the interval between the two reference lines was measured. This value was defined as A2 (unit: mm), and the numerical value calculated from the measured A2 and the formula of “100 × (100−A2) / 100” was defined as the TD heat shrinkage rate.
The results are shown in Table 2 below.

<Absolute value of difference between MD heat shrinkage rate and TD heat shrinkage rate (absolute value of MD-TD difference)>
From the obtained MD thermal contraction rate and TD thermal contraction rate, the absolute value of the difference between the MD thermal contraction rate and the TD thermal contraction rate (the absolute value of the MD-TD difference) was calculated.
The results are shown in Table 2 below.

[Evaluation]
<The bonding angle and rainbow unevenness with respect to the polarizing plate of the film at the time of evaluation>
A polarizing plate was placed on a continuous light source (white LED), a uniaxially stretched polyester film of each Example and Comparative Example was bonded thereon, and rainbow unevenness generated visually through polarized sunglasses was evaluated according to the following criteria.
In addition, it bonded together so that the angle of the slow axis of a film with respect to the absorption axis of a polarizing plate might turn into the angle as described in an Example.
A: Rainbow unevenness is not visible at all B: Rainbow unevenness is not visible C: Rainbow unevenness is hardly visible D: Rainbow unevenness is visible The evaluation results are shown in Table 2 below.

<Blackout>
A polarizing plate is placed on a continuous light source (white LED), and a uniaxially stretched polyester film of each Example and Comparative Example is laminated thereon, and the blackout generated when observed while rotating polarized sunglasses is as follows. Evaluated by criteria.
In addition, it bonded together so that the angle of the slow axis of a film with respect to the absorption axis of a polarizing plate might turn into the angle as described in an Example.
A: Blackout does not occur at all B: Some darkening occurs C: Some darkening occurs D: Blackout occurs Evaluation results are shown in Table 2 below.

<Wrinkles during processing>
The uniaxially stretched polyester film of each Example and Comparative Example, which was formed into a 10,000 m film and wound into a roll form, was unwound, and a hard coat layer was applied as a post-process by the following method. After the hard coat layer was applied to both sides of the film, the film was dried and conveyed in a drying zone at 150 ° C. with a conveyance tension per film cross-sectional area set to 1500 kN / m ² .
The degree of wrinkling of the film when such processing was performed was evaluated according to the following criteria.
A: No wrinkle generation B: Slight wrinkle generation C: Some wrinkle generation D: Many wrinkles generation Evaluation results are shown in Table 2 below.

<Break during processing>
The uniaxially stretched polyester film of each Example and Comparative Example, which was formed into a 10,000 m film and wound into a roll form, was unwound, and a hard coat layer was applied as a post-process by the following method. After the hard coat layer was applied to both sides of the film, the film was dried and conveyed in a drying zone at 150 ° C. with a conveyance tension per film cross-sectional area set to 1500 kN / m ² .
The number of breaks of the film when such processing was performed was measured.
The term “break” refers to a scratch having a length of 50 mm or more and penetrating in the film thickness direction. Further, the direction of the scratch was not limited, and both the scratch in the TD direction and the scratch in the MD direction were included in the break when penetrating in the film thickness direction.
The results evaluated according to the following criteria are shown in Table 2 below.
A: 10000 m or more without base break B: 10000 m with 1-5 breaks C: 10000 m with 6-10 breaks D: 10000 m with 11 breaks or more

<Touch panel thickness suitability>
The touch panel thickness suitability was evaluated according to the following criteria.
A: Film thickness is 40 μm or less B: Film thickness exceeds 40 μm, 50 μm or less C: Film thickness exceeds 50 μm, 60 μm or less D: Film thickness exceeds 60 μm Evaluation results are shown in Table 2 below.

<Comprehensive evaluation>
The overall evaluation was based on the following criteria.
A: All evaluations are A rank B: All evaluations are B rank or more C: All evaluations are C rank or more D: One or more D rank evaluations The evaluation results are shown in Table 2 below.

From the above Tables 1 and 2, the uniaxially oriented polyester film of each example manufactured while satisfying the manufacturing conditions defined in the present invention satisfies all the above formulas 1 to 7, can suppress the occurrence of rainbow unevenness, and is used for a touch panel. It was found that the thickness was particularly suitable for use as a base material for various films for touch panels.
On the other hand, it was found that the uniaxially oriented polyester of Comparative Example 1 in which the range of the thickness t exceeds the upper limit value defined in the present invention and Re exceeds the upper limit value defined in the present invention is inferior in touch panel thickness suitability.
The uniaxially oriented polyester of Comparative Example 2 in which the range of the thickness t is below the lower limit value specified in the present invention and the TD tear strength is lower than the lower limit value specified in the present invention shows rainbow unevenness and frequent breakage during processing. I understood it.
The transverse stretching ratio exceeds the upper limit defined in the present invention, the film surface temperature at the start of transverse stretching is below the lower limit defined in the present invention, and the film surface temperature at the end of transverse stretching is the lower limit defined by the present invention. The uniaxially oriented polyester film of Comparative Example 3 manufactured under lower manufacturing conditions has a Re / Rth ratio below the lower limit specified in the present invention, and the elastic modulus in the MD direction is lower than the lower limit specified in the present invention. It was found that the ratio ETD / EMD with respect to the MD elastic modulus is a uniaxially oriented polyester film that exceeds the upper limit defined in the present invention, rainbow unevenness is visible, and many wrinkles occur during processing.
The transverse stretching ratio is lower than the lower limit value specified in the present invention, the film surface temperature at the start of the horizontal stretching exceeds the upper limit value specified in the present invention, and the film surface temperature at the end of the horizontal stretching is the upper limit value specified in the present invention. In the uniaxially oriented polyester film of Comparative Example 4 produced under the production conditions exceeding, the Re / Rth ratio exceeds the upper limit defined in the present invention, and the ratio ETD / EMD of the TD elastic modulus to the MD elastic modulus is defined in the present invention. Below the lower limit, TD tear strength is lower than the lower limit specified in the present invention, MD fracture strength is less than the lower limit specified in the present invention, uniaxially oriented polyester film, rainbow unevenness is visible, many wrinkles during processing It occurred, and it was found that breaking during processing was frequent.
The film surface temperature at the start of transverse stretching exceeds the upper limit specified in the present invention, the film surface temperature at the end of transverse stretching is lower than the lower limit defined in the present invention, and the film surface temperature is increased from the start of stretching to the end of stretching. The uniaxially oriented polyester film of Comparative Example 5 produced without gradually increasing the MD modulus of elasticity below the lower limit defined in the present invention, and the ratio ETD / EMD of the TD modulus to the MD modulus of the present invention is Is a uniaxially oriented polyester film with a TD tear strength lower than the lower limit value specified in the present invention, and an MD fracture strength lower than the lower limit value specified in the present invention. It was found that breaking during processing was frequent.
The film surface temperature at the start of transverse stretching exceeds the upper limit defined in the present invention, and the uniaxially oriented polyester film produced in Comparative Example 6 without gradually increasing the film surface temperature from the start of stretching to the end of stretching, It was found that the TD tear strength was lower than the lower limit value defined in the present invention, the MD fracture strength was lower than the lower limit value defined in the present invention, and the fracture during processing was frequent. Therefore, from Comparative Example 6, the uniaxially oriented polyester film of the present invention has a problem of breakage in the processing steps of various films used for the touch panel than the uniaxially oriented polyester film described in the examples of JP2012-230390A. It turned out that it was excellent in the point which can be eliminated.

Claims (14)

A uniaxially oriented polyester film satisfying the following formulas 1 to 7;
20 μm ≦ t ≦ 60 μm Formula 1
2000 nm ≦ Re ≦ 6500 nm Formula 2
0.7 ≦ Re / Rth ≦ 1.4 Formula 3
2000 MPa ≦ EMD Formula 4
2 ≦ ETD / EMD ≦ 3 Formula 5
5 g · cm / cm ≦ TRTD Formula 6
50 MPa ≦ TBMD Formula 7
In formulas 1 to 7, t represents the film thickness, the unit is μm,
Re represents retardation in the film plane, the unit is nm,
Rth represents retardation in the film thickness direction, the unit is nm,
EMD represents the elastic modulus in the longitudinal direction of the film, the unit is MPa,
ETD represents the elastic modulus in the film width direction, the unit is MPa,
TRTD represents the tear strength in the film width direction, the unit is g · cm / cm,
TBMD represents the breaking strength in the longitudinal direction of the film, and its unit is MPa. The thermal shrinkage rate in the MD direction after leaving the uniaxially oriented polyester film at 150 ° C. for 30 minutes is 0.8% or less,
The heat shrinkage rate in the TD direction after leaving the uniaxially oriented polyester film at 150 ° C. for 30 minutes is 0.8% or less,
The uniaxially oriented polyester film according to claim 1, wherein an absolute value of a difference between the thermal shrinkage rate in the MD direction and the thermal shrinkage rate in the TD direction is 0.6% or less.   The uniaxially oriented polyester film according to claim 1 or 2, wherein an easy adhesion layer is laminated on at least one side of the uniaxially oriented polyester film. The easy-adhesion layer contains particles;
The uniaxially oriented polyester film according to claim 3, wherein a height at which the particles protrude from the surface of the easy adhesion layer is equal to or greater than a film thickness of the easy adhesion layer;
The height at which the particles protrude from the surface of the easy adhesion layer is an average value at 5 points in the 1 mm square easy adhesion layer.   The hard coat film by which the hard-coat layer was laminated | stacked on the at least single side | surface of the uniaxially-oriented polyester film as described in any one of Claims 1-4.   The scattering prevention film by which the adhesion layer was laminated | stacked on the at least single side | surface of the uniaxially-oriented polyester film as described in any one of Claims 1-4.   The antireflection film by which the glare-proof layer was laminated | stacked on the at least single side | surface of the uniaxially-oriented polyester film as described in any one of Claims 1-4.   The sensor film for touchscreens containing the uniaxially-oriented polyester film as described in any one of Claims 1-4.   The uniaxially oriented polyester film according to any one of claims 1 to 4, the hard coat film according to claim 5, the scattering prevention film according to claim 6, the antireflection film according to claim 7, and the claim. A touch panel comprising at least one of the sensor films for a touch panel according to claim 8. LCD panel,
A polarizing plate disposed on the exit surface of the liquid crystal panel;
At least one slow axis of the uniaxially oriented polyester film, the hard coat film, the scattering prevention film, the antireflection film, and the touch panel sensor film is 45 ± 25 ° with respect to the absorption axis of the polarizing plate. The touch panel according to claim 9, which is arranged in a range. It is a manufacturing method of the uniaxially oriented polyester film according to any one of claims 1 to 4 using a tenter type stretching device which has a clip which runs along a pair of rails installed on both sides of a film conveyance path,
A step of laterally stretching while gripping a substantially unstretched polyester film with the clip;
A heat setting step of heating the polyester film after the transverse stretching to the maximum temperature in the tenter,
The transverse stretching ratio in the transverse stretching step is controlled in the range of 3.3 times to 4.8 times,
In the transverse stretching step, the film surface temperature at the start of stretching is kept in the range of 80 ° C. or more and 95 ° C. or less, and the film surface temperature at the end of stretching is kept at 90 ° C. or more and 105 ° C. or less,
The film surface temperature is gradually increased from the start of stretching to the end of stretching,
The manufacturing method of the uniaxially-oriented polyester film whose thickness of the said uniaxially-oriented polyester film is 20 micrometers or more and 60 micrometers or less. In the transverse stretching step,
The film surface temperature in the range of draw ratio of 1 to 2 times is 80 ° C. or more and 92 ° C. or less,
The film surface temperature in the range of draw ratio of 2 to 3 times is 85 ° C or higher and 97 ° C or lower,
The method for producing a uniaxially oriented polyester film according to claim 11, wherein the film surface temperature in a range where the draw ratio is 3 times or more is maintained at 90 ° C or higher and 102 ° C or lower;
However, the film surface temperature in the range where the draw ratio is 2 to 3 times is not lower than the film surface temperature in the range where the draw ratio is 1 to 2 times, and the film surface temperature in the range where the draw ratio is 3 times or more is stretched. The magnification never falls below the film surface temperature in the range of 2 to 3 times. Including a heat relaxation step of heating the heat-fixed polyester film and reducing at least the length of the polyester film in the MD direction;
In the heat relaxation step, the relaxation rate in the MD direction, which is the ratio of shrinking the length in the MD direction of the heat-fixed polyester film, is 1 to 7%, and the length in the TD direction of the heat-fixed polyester film is The method for producing a uniaxially oriented polyester film according to claim 11 or 12, wherein a relaxation rate in the TD direction, which is a shrinking ratio, is 0 to 6%.   The manufacturing method of the uniaxially-oriented polyester film of Claim 13 which keeps the highest reach | attainment film surface temperature of the said heat setting and the said heat relaxation process in the range of 130 degreeC or more and 190 degrees C or less.