KR20200057682A - Resin film and method for producing the same - Google Patents

Abstract

An object of the present invention is to provide a resin film which has optical properties required for a front panel while being suppressed in defects such as damage due to rattling of the film during production and a manufacturing method thereof. According to the present invention, the resin film comprises at least one of a polymer resin or a polyamide resin, and the center point in the width direction of the film is set as TD_c; the in-plane phase difference value R (TD_c) of TD_c and the in-plane phase difference value R (TD_80) of TD_80, which are measured at a wavelength of 590 nm, satisfy formula (1), where TD_80 is the point of 80% of the length from the center point in the width direction to the end portion with the center point being 0%. R (TD_c) / R (TD_80) >= 0.35 (1).

Description

RESIN FILM AND METHOD FOR PRODUCING THE SAME

The present invention relates to a resin film containing at least one of a polyimide-based resin or a polyamide-based resin and a method for manufacturing the same.

In recent years, thinning, lightening, and flexible of image display devices have been demanded, but conventionally used glass substrates or glass front plates do not have sufficient material properties to meet the above requirements. For this reason, the development of materials or substrates in place of glass is progressing. One of them is a resin film containing a polyimide resin. The resin film containing a polyimide resin is used for various uses from a viewpoint of flexibility, transparency, and heat resistance (Patent Document 1).

Japanese Patent Application Publication No. 2009-286826

When a film containing a polyimide-based resin is used as a front plate of an image display device, a process of heating the film under high temperature conditions is performed for the purpose of increasing the surface hardness. However, there has been a problem that, by heating under high temperature conditions, the film turns yellow and the quality of the film is impaired. Moreover, since the front plate is disposed on the viewing side of the image display device, there are no defects such as scratches that may affect visibility, and it is required to have the optical and physical properties required for the front plate.

The present invention has been made in view of the above problems, and provides defects such as scratches due to flapping of the film in the manufacturing process, and provides a resin film having the optical properties required for the front plate and a method for manufacturing the same . That is, this invention provides the manufacturing method of the resin film of the following aspects.

[1] A resin film comprising at least either a polyimide resin or a polyamide resin,

When the center point in the width direction of the film is TD _c and the length from the center point in the width direction to the end is 0% and the length of 80% is TD ₈₀ , the measurement is performed at a wavelength of 590 nm. a TD of _c-plane retardation value R (TD _c) and the in-plane retardation value R of the TD ₈₀ to the resin film (TD ₈₀₎ meet the formula (1).

R (TD _c ) / R (TD ₈₀ ) ≥0.35 (1)

[2] The resin film, in the center of the film width direction in the length of the end portion from the center point of a TD _c, and the width direction, when the length of that of the 66% to the center point of 0% by TD _66, a wavelength _c-plane retardation value of the TD measured at 590nm R (TD _c) and the in-plane retardation value R of the TD ₆₆ (TD ₆₆₎ resin film as defined in [1] which satisfies the expression (2).

R (TD _c ) / R (TD ₆₆ ) ≥0.40 (2)

[3] The resin film according to [1] or [2], in which the resin film satisfies Expression (3).

R (TD _c ) / R (TD ₆₆ ) -R (TD _c ) / R (TD ₈₀ ) <0.15 (3)

[4] The resin film according to any one of [1] to [3], wherein the weight reduction ratio is 3% or less.

[5] The resin film according to any one of [1] to [4], wherein the overall width in the resin film width direction is 300 to 2,200 mm.

[6] A flexible display device comprising the resin film according to any one of [1] to [5].

[7] The flexible display device according to [6], further comprising a touch sensor.

[8] The flexible display device according to [6] or [7], further comprising a polarizing plate.

[9] A method for producing a resin film comprising at least either a polyimide resin or a polyamide resin,

Has a heating process for heating the raw material film in a tenter furnace that is divided into a plurality of spaces inside,

In the tenter furnace, a heating process is performed in a hot air treatment system in at least one space, and a heating process is performed in a radiation treatment system in at least one space.

[10] The method for producing the resin film according to [9], wherein the heating step is performed in both the hot air treatment method and the radiation treatment method in the same space as the tenter.

[11] The method according to [9] or [10], wherein the heating process of the radiation treatment method is performed by shooting a radiation film at a temperature of 30 ° C or higher higher than the temperature of the space where the heating process is performed by the radiation treatment method. Manufacturing method of resin film.

[12] The method for producing a resin film according to any one of [9] to [11], wherein the raw material film contains a solvent and the weight reduction rate of the raw material film is 40% or less.

According to the present invention, defects such as scratches are suppressed, and a resin film having excellent optical properties required for the front plate, such as uniform in-plane retardation and low yellowness, is provided.

The resin film obtained by the present invention can be used as an optical film such as a front plate of a flexible display.

1 is a process sectional view schematically showing a suitable embodiment of a method for producing a resin film of the present invention.
2 is a process cross-sectional view schematically showing a preferred embodiment of a heating process in the method for producing a resin film of the present invention.
3 is a process cross-sectional view schematically showing a suitable embodiment in a tenter furnace in the method for producing a resin film of the present invention.

Hereinafter, embodiments of the present invention will be described in detail. In addition, the scope of the present invention is not limited to the embodiments described herein, and various changes can be made without departing from the spirit of the present invention.

<Resin film>

The resin film of the present invention is a resin film containing at least one of a polyimide-based resin or a polyamide-based resin, wherein the center point in the film width direction is TD _c , and the length from the center point in the width direction to the end is the center point of time when the 80% of the length point to 0% in TD _80, a one TD _c of the in-plane retardation value R (TD _c) and TD _80-plane retardation value R (TD ₈₀₎ of measurement at a wavelength of 590nm formula ( 1) is satisfied.

R (TD _c ) / R (TD ₈₀ ) ≥0.35 (1)

The resin film satisfying the above formula (1) is in a direction perpendicular to the film transport direction (also referred to as MD direction) when the resin film according to the present invention is continuously produced (also referred to as film width direction and TD direction). , In the range of both ends of the film from the center in the TD direction, the variation in the in-plane retardation value is small. When such a resin film is used for a front plate of an image display device such as a flexible display device, it is excellent in visibility because the occurrence of variations in the clarity of the visually recognized image is suppressed.

R (TD _c ) / R (TD ₈₀ ) in the formula (1) is preferably 0.36 or more, more preferably 0.37 or more, still more preferably 0.38 or more, even more preferably 0.42 or more, particularly preferably 0.44 or more. R (TD _c ) / R (TD ₈₀ ) in the formula (1) is preferable because the closer to 1, the smaller the deviation in the in-plane retardation value between the center portion of the film and both ends of the film in the TD direction.

The resin film is a resin film containing at least one of a polyimide-based resin or a polyamide-based resin, the center point in the film width direction is TD _c , and the center point is 0 in the length from the center point to the end in the width direction. when the% by the longitudinal point of 66% of the TD _66, the in-plane retardation value of a TD _c measured at a wavelength of 590nm R (TD _c) and the in-plane retardation value of the TD ₆₆ R (TD ₆₆₎ for the equation (2) It is desirable to meet.

R (TD _c ) / R (TD ₆₆ ) ≥0.40 (2)

R (TD _c ) / R (TD ₆₆ ) of the formula (2) is more preferably 0.45 or more, further preferably 0.50 or more, even more preferably 0.52 or more, particularly preferably 0.58 or more. R (TD _c ) / R (TD ₆₆ ) is preferable because the closer to 1, the smaller the deviation of the in-plane retardation value between the film center portion and the film end portion in the TD direction.

When the value of the formula (1) or the formula (2) is within the above range, when the resin film is used as a front plate, it can be used in the product even if it is a part close to both ends of the film, and is preferable because it has a higher yield.

It is preferable that the difference between the ratio R (TD _c ) / R (TD ₆₆ ) and the ratio R (TD _c ) / R (TD ₈₀ ) of the resin film satisfies Expression (3). The difference in the ratio is more preferably 0.13 or less, more preferably 0.12 or less, even more preferably 0.11 or less, particularly preferably 0.10 or less. When the difference in the ratio is within this range, the variation in the phase difference in the plane of the resin film is small.

R (TD _c ) / R (TD ₆₆ ) -R (TD _c ) / R (TD ₈₀ ) <0.15 (3)

It is preferable that a resin film satisfies Formula (1) and Formula (2), and also satisfies Formula (3), and it is a formula (4)-Formula (6) which is a subordinate of Formula (1)-Formula (3). It is more preferable to satisfy all. Such a resin film is preferable because the deviation of the phase difference in the in-plane of the resin film is smaller, and when the resin film is used as a front plate, it can be used for a product even if it is a part close to both ends of the film, resulting in a higher yield.

R (TD _c ) / R (TD ₈₀ ) ≥0.37 (4)

R (TD _c ) / R (TD ₆₆ ) ≥0.45 (5)

R (TD _c ) / R (TD ₆₆ ) -R (TD _c ) / R (TD ₈₀ ) ≤0.13 (6)

In the resin film, the overall width in the width direction is preferably 300 to 2,200 mm. In the present specification, the "total width" refers to the entirety of the direction perpendicular to the transport direction of the film (which is also referred to as the width direction and the TD direction) in the resin film according to the present invention. The overall width in the film width direction is more preferably 400 to 2,100 mm, and more preferably 500 to 2,000 mm.

The thickness of the resin film is preferably 10 μm or more, more preferably 20 μm or more, and even more preferably 30 μm or more. Moreover, the said thickness is preferably 120 micrometers or less, More preferably, it is 100 micrometers or less, More preferably, it is 80 micrometers or less. When the thickness is 30 µm or more, it is advantageous from the viewpoint of internal protection when the resin film is introduced into the display device, and when the thickness is 120 µm or less, it is advantageous from the viewpoints of corrosion resistance, cost, and transparency. The measurement method will be described in detail in Examples.

It is preferable that the weight reduction rate M over 120 degreeC to 250 degreeC calculated | required by TG-DTA measurement of the resin film which passed the heating process is 3% or less. The weight loss ratio M is more preferably 2% or less, more preferably 1.5% or less, and even more preferably 1% or less. Moreover, although the lower limit of the weight loss rate M is not specifically limited, it can be made into 0.1%, for example.

When the weight reduction rate M of the resin film is within the above range, a film having both sufficient hardness and flexibility required for the front plate of the flexible display device tends to be obtained. When the residual solvent amount is more than the above upper limit, the film surface is likely to be soft and scratched, so that handling of the film may be difficult in a subsequent step.

The haze of the resin film is preferably 1% or less, more preferably 0.8% or less, still more preferably 0.5% or less, particularly preferably 0.3% or less from the viewpoint of visibility. The haze of the resin film can be measured according to JIS K 7136: 2000. The measurement method will be described in detail in Examples.

The total light transmittance of the resin film is preferably 85% or more, more preferably 87% or more, and even more preferably 89% or more. The total light transmittance of the resin film can be measured according to JIS K 7361-1: 1997. The measurement method will be described in detail in Examples. When the total light transmittance of the resin film is within the above numerical range, sufficient film appearance can be ensured when introduced into the image display device.

The yellowness of the resin film is preferably 3.0 or less, more preferably 2.7 or less, and even more preferably 2.5 or less. The yellowness of the resin film can be measured according to JIS K 7373: 2006. The measurement method will be described in detail in Examples. It is excellent in visibility within this range, and can be suitably used as a display member such as a front panel.

<Method for manufacturing resin film>

The manufacturing method of the resin film of this embodiment has a heating process of heating a raw material film in a tenter furnace which is divided into a plurality of spaces inside, and in the tenter furnace, a heating process is performed in a hot air treatment system in at least one space In addition, a heating process is performed in a radiation treatment method in at least one space. The tenter furnace refers to a furnace in which both ends of the film width direction are fixed and heated.

The manufacturing method of the resin film of this embodiment is demonstrated, referring drawings. 1 is a process sectional view schematically showing a preferred embodiment of a method for producing a resin film according to the present invention. Referring to FIG. 1, a raw material film 20 containing at least either a polyimide-based resin or a polyamide-based resin is brought into the tenter furnace 100 and heated in a heating zone in the tenter furnace 100. , It is then taken out from the tenter 100. In this specification, the film that is conveyed during the heating process or in the oven, although there is a change over time such as the amount of the solvent and before the heating process, is referred to as a raw material film, and the film taken out from the oven through the heating process is referred to as a resin film. .

The raw material film 20 may be taken out from the roll on which the raw material film is wound and taken into the tenter furnace 100, or may be continuously carried into the tenter furnace from the immediately preceding process. 2 is a process cross-sectional view schematically showing a preferred embodiment of a heating step in the method for producing a resin film according to the present invention. Referring to FIG. 2, in the tenter furnace, the raw film 20 is fixed at both ends of a film in a direction perpendicular to the transport direction of the film (also referred to as MD direction and longitudinal direction) (also referred to as TD direction and width direction). It is preferable to be conveyed.

Fixing of both ends can be performed using a gripping apparatus generally used for a film production apparatus such as a pin sheet, a clip, and a film chuck. Both ends to be fixed can be appropriately adjusted by a gripping device to be used, but are preferably fixed at a distance within 50 cm from the end of the film. Referring to FIG. 2, both ends of the film can be conveyed while being gripped by a plurality of gripping devices 18. It is preferable that the plurality of gripping devices 18 provided at one end of the film have a distance between adjacent gripping devices to suppress defects such as flaking due to flapping of the film or dimensional changes due to heating. Do. The distance between adjacent gripping devices 18 is preferably 1 to 50 mm, more preferably 3 to 25 mm, and further preferably 5 to 10 mm. In addition, when the gripping device aligns a straight line orthogonal to the film conveying axis with the center of the gripping portion of any gripping device at one end of the film, the intersection of the straight line with the other end of the film and the grip closest to the intersection point It is preferable that the distance of the center of the gripping portion of the device is preferably 3 mm or less, more preferably 2 mm or less, and more preferably 1 mm or less. Thereby, since the difference in stress with respect to each of both ends of the opposing film can be made small, the resulting resin film can suppress the occurrence of variations in optical properties.

As an example of the operation of fixing both ends of the film with the gripping device, both ends of the width direction of the film with a plurality of film chucks arranged to face each other in the width direction of the film before or after being carried into the tenter furnace. How to fix it. By such an operation, the flapping of the film is suppressed, and a resin film in which defects such as thickness unevenness and scratches are sufficiently suppressed can be obtained. The fixing of both ends of the film may be released in a timely manner after the heating step is performed, or may be performed in a tenter furnace or after being taken out from the tenter furnace.

The total length of the film conveying direction to the tenter used in the heating step is usually 10 to 100 m, preferably 15 to 80 m, more preferably 15 to 60 m. As the tenter, the inside may be a single space or may be divided into a plurality of spaces, but in the embodiment of the present invention, the inside of the tenter performing the heating process is divided into a plurality of spaces. The space may be a space in which temperature conditions, wind speed conditions, or the like can be controlled, and may not have physical boundaries such as partition plates. When the inside of the tenter is divided into a plurality of spaces, the spaces may be divided into a plurality of spaces vertically or parallel to the transport direction of the film. The number of spaces is usually 2 to 20, preferably 3 to 18, more preferably 4 to 15, and more preferably 5 to 10. Regardless of the internal structure of the tenter, the entire tenter furnace may be a heating zone, or a part of the interior may be a heating zone. Referring to FIG. 1, all three of zones 10, 12, and 14 may be heating zones, or one of them, for example, zone 14 may be a heating zone.

Multiple tenters may be used. The number of tenters in this case is not particularly limited, but can be, for example, 2 to 12 pieces. The interior of each tenter may have the structure described above. With a plurality of tenters, the film can be continuously installed so as to be conveyed without contact with the outside air. When using multiple tenter furnaces, all the tenter furnaces may be heating zones, or some tenter furnaces may be heating zones. Moreover, you may use an oven as another apparatus in addition to a tenter furnace. In the present specification, the oven means an apparatus capable of heating a film, and includes a heating furnace and a drying furnace. As the heating furnace, either a hot air treatment or a radiation treatment may be used, or a heating furnace using these in combination. When the oven is used in combination, the internal structure of the oven, the number to be used, and the conditions for heating may be appropriately adjusted within the range in which the resin film according to the present invention is obtained, but it is preferable to do the same as the tenter furnace described in this specification.

Circulation and exhaust of the air inside the tenter is preferably performed in each space when the interior of the tenter is divided into a plurality of spaces, and preferably in each tenter furnace when there are multiple tenter furnaces. It is preferable that the temperature inside the tenter furnace (the temperature of the atmosphere in the tenter furnace) can be adjusted for each tenter, and when the interior of the tenter is divided into a plurality of spaces, the temperature can be independently adjusted in each space. It is preferred. The temperature setting of each space may be the same or different. However, it is preferable that the temperature of each tenter or space satisfies the temperature range described later.

In the tenter furnace 100 in which the heating process is performed, a heating process is performed in a hot air treatment system in at least one space, and a heating process is performed in a radiation treatment system in at least one space. As for the heating process, it is preferable that all spaces in which this process is performed are performed by a hot air treatment system. Although the heating process of the radiation treatment method may be performed in a space different from the hot air treatment method, it is preferable that the heating process is performed in combination with the hot air treatment method.

The heating process of the hot air treatment method can be performed by installing a nozzle that blows out hot air in a tenter furnace. The heating process of the radiation treatment method can be performed by installing an IR heater or the like in a tenter furnace and radiating radiation onto the film.

As an example of the embodiment of the present invention, the hot air treatment method using a nozzle and the radiation treatment method using an IR heater will be described below in order from the hot air treatment method using a nozzle.

Referring to FIG. 1, the tenter furnace 100 in which the heating process is performed is provided with a plurality of upper nozzles 30 on the inner upper surface 100a and a plurality of lower sides on the inner lower surface 100b. The nozzle 32 is provided. The upper nozzle 30 and the lower nozzle 32 are provided to face in the vertical direction. For example, four pairs of nozzles (eight total) may be provided as in the zone 14 of FIG. 1, or ten pairs of nozzles (20 total) may be provided as in the zone 12 of FIG. And can be properly installed according to the structure of the oven. The interval between adjacent nozzles is preferably 0.1 to 1 m, more preferably 0.1 to 0.5 m, and even more preferably 0.1 to 0.3 m from the viewpoint of uniformly heating the raw material film while simplifying the structure of the tenter.

When the interior of the tenter is divided into a plurality of sections, the number of hot air blowing nozzles provided in each space may be usually 5 to 30. From the viewpoint of obtaining a resin film having better optical uniformity, the number of nozzles is preferably 8-20. When the number of nozzles is within the above range, the curvature of the film being floated tends to be too large, and the film tends to float between nozzles, that is, it is easy to float.

The upper nozzle 30 provided on the upper surface 100a of the tenter furnace 100 has a blow-out port at the bottom, so that hot air can be blown out in the downward direction (arrow B direction). On the other hand, the lower nozzles 32 respectively provided on the lower surface of the tenter furnace 100 have a blowout port at the top, and can blow out hot air in an upward direction (arrow C direction). In addition, although not shown in FIG. 1, the upper nozzle 30 and the lower nozzle 32 have a predetermined size in the vertical direction with respect to the ground surface of FIG. 1 so that the raw material film can be uniformly heated in the width direction. Have it.

In the manufacturing method of the resin film of this embodiment, the blowing wind speed of the hot air in the blowing ports from all the upper nozzles 30 and all the lower nozzles 32 provided in the heating zone is preferably 2 to 25 m / sec. From the viewpoint of obtaining a resin film having better optical uniformity, the blowing wind speed is more preferably 2 to 23 m / sec, and more preferably 8 to 20 m / sec. Moreover, the blow-out air volume from the blow-out opening per 1 m of nozzle 30 or 32 per length of the nozzle along the width direction of a raw material film is preferably 0.1 to ³ m ³ / sec. In addition, the blown air amount is per 1 m of the length of the nozzle along the width direction of the film from the viewpoint of obtaining a resin film with better optical uniformity, more preferably 0.1 to 2.5 m ³ / sec, more preferably 0.2 to 2 m ³ / sec.

If the wind speed and the air volume taken out from the nozzle are within the above range, the raw film is uniformly heated, and therefore, a film having optical and physically uniform physical properties tends to be easily obtained. Specifically, when the heating step is performed under the above conditions, the variation in the in-plane retardation value in the film width direction becomes small, and a resin film having a more uniform in-plane retardation value in the entire film is likely to be obtained. Therefore, when applied to a display device, variations in contrast are suppressed, and a front plate having better visibility is obtained.

In addition, when the heating step is performed under the above conditions, since it is uniformly heated, the variation in the amount of solvent remaining in the film becomes small, and a resin film having a more uniform elastic modulus is easily obtained on the entire surface of the film. Therefore, it is difficult to cause variations in flexibility in the entire film surface, and it is possible to suppress occurrence of damage caused by a difference in flexibility in the film surface.

In the tenter furnace, the raw material film 20 is heated from room temperature to a temperature at which the solvent contained in the raw material film evaporates, but is held by the gripping device 18 so that the length in the width direction of the raw material film hardly changes. Therefore, it tends to be liable to sag due to thermal expansion. When the blowing air velocity and the blowing air volume are within the above range, the raw material film 20 can be sufficiently heated, and sagging and flapping of the raw material film 20 can be suppressed.

The blowing wind speed of the hot air can be measured by using a commercially available thermal anemometer at the hot air blowing ports of the nozzles 30 and 32. In addition, the blow-off air volume from the blow-out port can be obtained by multiplying the blow-off wind speed by the area of the blow-out port. In addition, it is preferable to measure the wind speed of the hot air from the viewpoint of measurement accuracy at about 10 points at the outlet of each nozzle, and set the average value.

The blowing wind speed and the blowing air amount of the hot air may be appropriately adjusted depending on the physical properties (optical properties, mechanical properties, etc.) of the resin film to be produced, but it is preferable that they are within the above ranges in any form. Thereby, a resin film in which the phase difference is more sufficiently uniform and has a sufficiently high axial precision can be obtained. In the heating zone, in all the heating zones, it is more preferable that the blowing wind speed is taken out at 25 m / sec or less, and the air volume is 2 m ³ / sec or less.

In the present embodiment, in a state in which the raw film 20 is not introduced into the tenter furnace 100, the wind speed of the hot air at the position where the raw film 20 should be held is preferably 5 m / sec or less. , It is more preferable that these wind speeds are at least in the heating zone. By heating the raw material film 20 using such hot air, a resin film having more excellent optical uniformity can be obtained.

In the heating zone, the difference between the maximum value and the minimum value in the width direction (direction perpendicular to the ground surface in FIG. 1) of the blowing wind velocity of the hot air at the outlet of each nozzle 30, 32 is preferably 4 m / Seconds or less. As described above, by using hot air having a small variation in wind speed in the width direction, a resin film with higher optical uniformity in the width direction can be obtained. By using hot air with a small variation in wind speed in this way, a resin film with higher optical uniformity can be obtained.

In the present embodiment, it is preferable that the wind speed of the hot air sprayed on the film is greater than the wind speed of another conveyance path in the oven, immediately after being brought into the oven. Immediately after being brought into the oven (hereinafter referred to as conveyance route 1) means that when the inside of the oven is not divided into a plurality, it is 1 / of the oven length from the oven inlet to the oven (the length from the oven inlet to the outlet). Refers to a distance less than 10. The conveyance path 1 refers to a space through which the film first passes when the inside of the oven is divided into a plurality of spaces. In the case where a plurality of ovens are used, it may be the same as the previous description depending on the internal structure of the first used oven, or the first passing oven may be set larger than the wind speed in the second or later oven.

The other conveyance path means a conveyance path portion 1/10 after the oven length from the oven inlet when the inside of the oven is not divided into a plurality. When the inside of the oven is divided into a plurality of spaces, it refers to any space after the second through which the film passes. When a plurality of ovens are used, the same may be the same as the previous description depending on the internal structure of the first used oven, or even if the wind speed in any oven is initially set to be smaller than the first oven in the second and subsequent ovens. do.

The difference between the wind speed of conveyance route 1 and the wind speed of other conveyance routes in the oven is preferably in the range of 0.1 to 15 m / sec. The difference in wind speed is more preferably 0.2 m / sec or more, more preferably 12 m / sec or less, more preferably 8 m / sec or less, even more preferably 5 m / sec or less, particularly preferably 3 m / Sec or less. When the wind speed immediately after entering the oven is made larger than the wind speed of other conveyance paths in the oven so that the difference in wind speed is within the above range, the solvent in the film tends to be more efficiently removed. If the difference in wind speed is too large, flapping of the film due to the wind speed difference may occur, and there is a possibility that it may cause a defect in the surface shape of the resulting resin film or an optical property variation such as a phase difference.

The difference between the wind speed of the conveyance path 1 and the wind speed of the other conveyance paths in the oven can be obtained as the difference between the wind speed of the hot air blowout from the nozzle installed in the conveyance path 1 and the wind speed of the hot air blowout from the nozzle installed in the other conveyance path. have. When there is a difference of 2 m / sec or more between the wind speed of the hot air sprayed onto the film and the wind speed of the hot air blown out from the nozzle, it may be determined as the difference between the wind speed of the hot air around the film in each of the transport path 1 and the other transport path.

It is preferable that another conveyance path is a conveyance path (referred to as conveyance path 2) located next to conveyance path 1. The conveyance path 2 means a conveyance path part positioned 2/10 of the oven length from the oven inlet when the inside of the oven is not divided into a plurality. The conveyance path 2 refers to a second space through which the film passes when the inside of the oven is divided into a plurality of spaces. In the case where a plurality of ovens are used, it may be the same as the above description depending on the internal structure of the first used oven, or the wind speed of the second oven may be set smaller than the first passing oven.

When the difference between the wind speeds of the conveyance path 1 and the conveyance path 2 is set as described above, the wind speed of the conveyance path after the conveyance path 2 may be within the range of the blowing wind speed of the hot air. The wind speed of the transport path after the transport path 2 is preferably the difference between the wind speed of each of the transport path 1 or the transport path 2 and the wind speed of 0.1 to 12 m / sec, and more preferably the difference between the wind speed of 0.2 to 8 m / sec. If the difference in wind speed in this range, the flutter of the film due to the wind speed difference can be suppressed, and the weight reduction rate of the resulting resin film tends to be easily adjusted to a desired range.

The difference in wind speed may be adjusted by adjusting the position at which the nozzle is provided, the speed and amount of air blown out of the nozzle, and the flow of airflow in the oven when the inside of the oven is not divided into a plurality of spaces. In the case where the inside of the oven is divided into a plurality of spaces, adjustment may be made by adjusting the position at which the nozzle is provided, the speed and amount of air blown out of the nozzle, and the flow of airflow in the oven in the first and subsequent spaces. . When using a plurality of ovens, depending on the structure of the first oven, it may be carried out in the same manner as described above, and the position at which the nozzle is provided so that the wind speed is different in the first oven and the second and subsequent ovens, the hot air of the nozzle It is sufficient to set the take-out speed, air volume, and airflow in the oven.

In the heating zone in the tenter furnace 100, the interval L (shortest distance) between the upper nozzle 30 and the lower nozzle 32 facing each other is preferably 150 mm or more, more preferably 150 to 600 mm, more preferably 150 to 400 mm. By arranging the upper nozzle and the lower nozzle at such intervals L, the flutter of the film in each step can be suppressed more reliably.

Moreover, the difference (ΔT) between the highest temperature and the lowest temperature in the width direction (vertical direction to the ground in FIG. 1) of the hot air at the outlet of each nozzle 30 and 32 provided in the heating zone is preferably All are 2 degrees C or less, More preferably, all are 1 degree C or less. As described above, by heating the film using hot air having a sufficiently small temperature difference in the width direction, it is possible to further suppress variation in orientation in the width direction. Further, the temperature of the hot air is preferably 150 to 400 ° C, more preferably 150 to 300 ° C, and even more preferably 150 to 250 ° C.

As a nozzle that can be used in a method for producing a resin film, a nozzle that is generally used in a film production apparatus can be used, and as an example, a nozzle having a slit-shaped ejection port extending in the width direction of a raw film can be used as a jet nozzle ( And a slit nozzle) and a punching nozzle (also referred to as a porous nozzle) with a nozzle having a plurality of openings each having a plurality of openings arranged in the transport direction of the raw film and the width direction of the raw film.

The nozzle is provided on the upper surface 100a in the tenter furnace 100, and a structure for taking out hot air against the film downward, and is provided on the lower surface 100b in the tenter furnace 100, and provides hot air against the film upward It is structured to be taken out.

The jet nozzle has a slit extending in the width direction of the film as a hot air outlet. The slit width of the slit is preferably 5 mm or more, and more preferably 5 to 20 mm. By making the slit width 5 mm or more, the optical uniformity of the obtained resin film can be further improved. In addition, the area of the ejection opening per jet nozzle can be obtained by multiplying the slit width by the length in the width direction of the nozzle of the jet nozzle. The product of the area of the blow-out port per nozzle and the blow-off wind speed becomes the blow-out air volume of hot air per nozzle. By dividing the blowing air volume of the hot air by the length of the slit along the width direction of the film, the blowing air volume of hot air per 1 m of the nozzle along the width direction of the film can be obtained.

The punching nozzle may have a trapezoidal shape in which a cross section perpendicular to the longitudinal direction has a rectangular shape or extends toward a surface facing the raw film 20. The punching nozzle has a plurality of openings (for example, circular openings) on the lower surface which is the surface facing the film. The hot air blowing port of the punching nozzle is constituted by a plurality of openings provided on the blowing surface. The plurality of openings are hot air outlets, and hot air is blown out at the predetermined wind speed from the openings. A plurality of openings are arranged in the longitudinal direction of the film, and a plurality of openings are also arranged in the width direction. The opening can be arranged in a zigzag form, for example.

The area of the ejection opening per punching nozzle can be determined by the sum of the areas of all openings provided in one punching nozzle. The product of the area of the blow-out port per nozzle and the blow-off wind speed becomes the blow-out air volume of hot air per nozzle. By dividing the blowing air volume of the hot air by the length of the slit along the width direction of the film, the blowing air volume of hot air per 1 m of the nozzle along the width direction of the film can be obtained.

In the case of using a punching nozzle, the difference between the maximum blowing wind speed and the minimum blowing wind speed in the width direction of the hot air at the nozzle outlet is the maximum blowing speed and minimum blowing speed of the hot air blown out from a plurality of openings provided on the same nozzle. It can be calculated as the difference in speed. The difference between the highest temperature and the lowest temperature in the width direction of the hot air at the outlet of the nozzle can also be obtained.

If all of the nozzles provided in the tenter furnace 100 are punching nozzles, the sum of the areas of the hot air blowout ports in the entire tenter furnace 100 can be increased. For this reason, the wind pressure of the hot air coming into contact with the film can be made small, and the flutter of the film can be made smaller. Thereby, the optical uniformity of the obtained resin film can be improved more. In the tenter furnace or in the heating zone, the raw film 20 is heated from room temperature to the temperature at which the solvent contained in the raw film evaporates, but is held by the gripping device 18 so that the length in the width direction of the raw film hardly changes. Therefore, it tends to be liable to sag due to thermal expansion. By using a punching nozzle for the heating zone, sagging and flapping of the raw material film 20 can be further suppressed.

The size and number of each of the openings provided on the surface of the punching nozzles are the lengths of nozzles in which the blowing wind speed of the hot air in each opening is 2 to 25 m / sec, and the blowing air volume from each nozzle follows the film width direction. It can be appropriately adjusted within a range of 0.1 to ³ m ³ / sec per 1 m.

It is preferable that the shape of the opening is circular from the viewpoint of making the wind speed taken out from each opening of the punching nozzle more uniform. In this case, the diameter of the opening is preferably 2 to 10 mm, more preferably 3 to 8 mm.

When using a punching nozzle, the length of the film conveying direction of the surface per nozzle is preferably 50 to 300 mm. Further, the distance from adjacent punching nozzles is preferably 0.3 m or less. Further, the ratio of the total area of the opening of the punching nozzle (the area of the outlet) to the length in the film width direction of the punching nozzle (the total area of the opening area of the punching nozzle (m ² ) / the length in the film width direction of the punching nozzle ( m)) is preferably 0.008 m or more.

By using such a punching nozzle, the area of the hot air blow-out port can be increased. Thereby, it is possible to sufficiently lower the wind speed of the hot air and take out the hot air with a sufficient amount of air, so that the film can be heated more uniformly. Thus, a film having a more uniform phase difference and higher axial precision can be produced.

In the tenter furnace 100 in which the heating process is performed, an IR heater may be provided on the upper surface 100a or the lower surface 100b therein, like the nozzle, and may be provided to face in the vertical direction. Further, a plurality of IR heaters may be provided. As the IR heater, an IR heater generally used in a film production apparatus may be used.

It is preferable that the wavelength is 3 to 7 µm as a radiation ray radiated on the film. In addition, in the radiation treatment method, when the temperature of the space in which the heating step is performed is within the above-mentioned temperature range, radiation of a temperature higher than the temperature of the space by 30 ° C. or higher may be shot on the raw film.

In the embodiment of the present invention, in the tenter furnace 100 in which the heating step is performed, it is preferable that the nozzle (hot air treatment method) and IR heater (radiation treatment method) are used in combination. In that case, an IR heater may be provided between adjacent nozzles or between an inner wall of the nozzle and the tenter (including a wall defining a space).

In this case, the temperature of the space in which the heating step is performed may be within the above temperature range, and in the radiation treatment method, radiation of a temperature higher than the temperature of the space may be shot on the film. The temperature of the radiation may be, for example, a temperature of 30 ° C or higher higher than the temperature of the space, or a temperature higher than 150 ° C. Here, the temperature of the radiation refers to a temperature set by a device that emits radiant heat, such as a set temperature of an IR heater. The difference between the temperature of the radiation and the temperature of the radiation irradiated on the film is preferably 5 ° C. or less, more preferably 3 ° C. or less, and more preferably 1 ° C. or less.

In the tenter furnace 100, when a nozzle (hot air treatment method) and an IR heater (radiation treatment method) are used in combination, the radiation in a temperature higher than the temperature in the heating zone or tenter furnace (atmosphere temperature) is shot on the raw film. , The heating step can be performed while suppressing the temperature in the heating zone or the tenter from becoming too high. Thereby, the weight reduction rate can be adjusted to a predetermined range more quickly while maintaining the yellowness (YI) of the obtained resin film at a small value as compared to a case where only one treatment method is employed to perform the heating process. In addition, since the resin in the raw material film tends to be oriented or reorientated by radiating radiation at a temperature higher than the temperature in the heating zone or tenter to the raw film, the resulting resin film has a small variation in the in-plane retardation value at the center and both ends of the film. Tend to lose. Therefore, as described above, the obtained resin film becomes more excellent in visibility of an image when applied to a display device.

In the heating process using the hot air treatment method and the radiation treatment method, the space between the space through which the raw material film first passes and the space located in the middle of the entire length of the tenter among the plurality of spaces where the heating process in the tenter furnace is performed. It is preferably done on. Thereby, not only the time required for a heating process can be shortened, but also the resin film which is excellent in uniformity of in-plane retardation can be manufactured.

The heating step is preferably performed in the range of 150 to 350 ° C. In the embodiment of the present invention, when the heating step is within this temperature range, it tends to be easy to adjust the raw material film so that the weight reduction rate M will be described later. The temperature range is more preferably 170 ° C. or higher, more preferably 180 ° C. or higher, even more preferably 300 ° C. or lower, further preferably 250 ° C. or lower, particularly preferably 230 ° C. or lower. When the temperature of the heating step is within the above range, the yellowness of the obtained resin film tends to exceed 3, which is a preferable range. Moreover, the temperature of the space in which the heating step is performed is more preferably 170 ° C or higher, and even more preferably 180 ° C or higher. As for the temperature in a tenter furnace in which a heating process is performed, the heating zone should just be the said range. When there are a plurality of tenter furnaces and when the tenter furnace is divided into a plurality of spaces, it can be appropriately adjusted, but it is preferable that all tenter furnaces or spaces are within the above range.

The moving speed of the raw material film 20 in the tenter furnace 100 can be appropriately adjusted within a range of usually 0.1 to 50 m / min. The upper limit of the moving speed is preferably 20 m / min, more preferably 15 m / min. The lower limit of the moving speed is preferably 0.2 m / min, more preferably 0.5 m / min, more preferably 0.7 m / min, particularly preferably 0.8 m / min. When the moving speed is fast, the length of the tenter becomes longer in order to secure a desired drying time, and the equipment tends to become large. In the embodiment of the present invention, when the moving speed of the raw material film 20 in the tenter furnace 100 is within the above range, the raw material film tends to be easily adjusted to a weight reduction rate M, which will be described later. Moreover, the flapping of a film is suppressed and there exists a tendency which can suppress that a flaw is generated in a film surface.

The treatment time of the heating step is usually 60 seconds to 2 hours, preferably 10 minutes to 1 hour. The treatment time may be appropriately adjusted in consideration of conditions such as temperature, movement speed, hot air wind speed, and air volume of the tenter.

The manufacturing method of the resin film of this embodiment may perform the operation of changing the width of a film during the heating process, or the operation of holding and conveying the film width. An example of an operation for changing the width of the film is an operation for stretching the width direction of the film. The draw ratio is preferably 0.7 to 1.3 times, more preferably 0.8 to 1.2 times, further preferably 0.8 to 1.1 times. As an example of the operation of holding and conveying the film width, an operation of holding the film so that the length in the width direction of the film hardly changes is mentioned. The resin film subjected to such an operation can be about 0.7 to 1.3 times as long as the length in the width direction of the raw film, and may be a length that is stretched, equally stretched or contracted from the length in the width direction of the raw film. The stretching magnification is determined as the ratio of the width of the film after stretching (excluding the gripping portion) to the width of the film excluding the gripping portion.

Moreover, in FIG. 2, in the operation of extending | stretching the width direction of a film, the case where the draw ratio is more than 1 time is represented by the solid line, and the case where the draw ratio is equal to or less than 1 time is indicated by the dotted line.

After being taken out of the tenter furnace, the resin film that has undergone the heating step may be continuously supplied to the next step, or may be wound into a roll shape to be supplied to the next step. When winding a resin film on a roll, you may wind up by laminating | stacking other films, such as a surface protection film and another optical film. As a surface protection film laminated on a resin film, the thing similar to the surface protection film laminated on a raw material film mentioned later can be used. The thickness of the surface protective film laminated on the resin film is usually 10 to 100 μm, preferably 10 to 80 μm.

<Raw film>

The raw material film supplied to a heating process contains at least either polyimide resin or polyamide resin. It is preferable that the raw material film contains the same components as those contained in the varnish used for the formation of the raw material film to be described later, but it is not necessary that the raw material film is the same, since structural changes of components and evaporation of a part of the solvent may occur. The raw material film may be a freestanding film, or a gel film.

The raw material film preferably has a weight reduction rate M ranging from 120 ° C to 250 ° C determined by thermogravimetric-differential thermal measurement (hereinafter sometimes referred to as "TG-DTA measurement") regardless of whether the inorganic material is contained. It is preferable that a portion of the solvent is removed from the varnish so that it is about 1 to 40%, more preferably 3 to 20%, more preferably 5 to 15%, and particularly preferably 5 to 12%. The weight reduction ratio M of the raw film can be measured by the following method using a commercially available TG-DTA measuring device. As a measuring device for TG-DTA, TG / DTA6300 manufactured by Hitachi High-Tech Science Corporation can be used.

First, a sample of about 20 mg is obtained from the raw film, and the sample is heated from room temperature to 120 ° C. at a heating rate of 10 ° C./min, held at 120 ° C. for 5 minutes, and then to 400 ° C. at a heating rate of 10 ° C./min. While heating under heating conditions, the weight change of the sample is measured. Next, from the results of the TG-DTA measurement, the weight loss rate M (%) ranging from 120 ° C to 250 ° C can be calculated by the following equation. In the following formula, W ₀ represents the weight of the sample after holding at 120 ° C for 5 minutes, and W ₁ represents the weight of the sample at 250 ° C.

M (%) = 100- (W ₁ / W ₀ ) × 100

When the weight reduction rate M of the raw material film is large to some extent, when the raw material film is wound as a laminate with a base material or a surface protection film, deformation such as bending of the laminate is suppressed, and the winding property of the laminate is improved. Tend to be.

When the weight reduction rate M of the raw material film is somewhat small, when the raw material film is wound as a laminate with a base material or a surface protective film, the raw material film tends to become difficult to stick to the base material or the surface protective film. For this reason, the laminated body can be easily unwound from the roll while maintaining uniform transparency of the raw film.

(Polyimide resin and polyamide resin)

The polyimide-based resin contained in the raw film and the resin film is a polymer containing a repeating structural unit containing an imide group (hereinafter, sometimes referred to as polyimide), and a repeating structure containing both an imide group and an amide group. At least one polymer selected from the group consisting of a polymer containing a unit (hereinafter sometimes referred to as polyamideimide) is shown. Moreover, a polyamide resin represents a polymer containing a repeating structural unit containing an amide group.

It is preferable that a polyimide resin has a repeating structural unit represented by Formula (10). Here, G is a tetravalent organic group, and A is a divalent organic group. The polyimide-based resin may contain repeating structural units represented by two or more kinds of formulas (10) in which G and / or A are different.

The polyimide-based resin may contain one or more selected from the group consisting of repeating structural units represented by formulas (11), (12), and (13) in a range that does not impair various physical properties of the resin film.

In formulas (10) and (11), G and G ¹ are each independently a tetravalent organic group, and preferably an organic group which may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. As G and G ¹ , formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) Or a group represented by Formula (29) and a tetravalent C 6 or less chain hydrocarbon group are exemplified. Since the yellowness (YI value) of the resin film is easily suppressed, among them, formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula The group represented by (26) or formula (27) is preferable.

In equation (20) to equation (29),

* Represents a bonding hand,

Z is a single bond, -O-, -CH _2- , -CH ₂ -CH _2- , -CH (CH ₃ )-, -C (CH ₃ ) _2- , -C (CF ₃ ) ₂ -,- Ar-, -SO _2- , -CO-, -O-Ar-O-, -Ar-O-Ar-, -Ar-CH ₂ -Ar-, -Ar-C (CH ₃ ) ₂ -Ar- or -Ar-SO ₂ -Ar-. Ar represents an arylene group having 6 to 20 carbon atoms which may be substituted with a fluorine atom, and specific examples thereof include a phenylene group.

In Formula (12), G ² is a trivalent organic group, preferably an organic group which may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. As G ² , formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) or formula A group in which any one of the bonds of the group represented by (29) is substituted with a hydrogen atom, and a trivalent carbon group having 6 or less carbon atoms are exemplified.

In Formula (13), G ³ is a divalent organic group, preferably an organic group which may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. As G ³ , equation (20), equation (21), equation (22), equation (23), equation (24), equation (25), equation (26), equation (27), equation (28) or equation Among the bonding hands of the group represented by (29), a group in which two nonadjacent groups are replaced by hydrogen atoms and a chain hydrocarbon group having 6 or less carbon atoms are exemplified.

In Formulas (10) to (13), A, A ¹ , A ² and A ³ are each independently a divalent organic group, and may be preferably substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. It is an organic group. As A, A ¹ , A ² and A ³ , equation (30), equation (31), equation (32), equation (33), equation (34), equation (35), equation (36), equation (37) ) Or a group represented by formula (38); Groups in which they are substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; And a chain hydrocarbon group having 6 or less carbon atoms is exemplified.

In equation (30) to equation (38),

* Represents a bonding hand,

Z ¹ , Z ² and Z ³ are each independently a single bond, -O-, -CH _2- , -CH ₂ -CH _2- , -CH (CH ₃ )-, -C (CH ₃ ) _2- , -C (CF ₃ ) _2- , -SO ₂ -or -CO-.

In one example, Z ¹ and Z ³ are -O-, and Z ² is -CH _2- , -C (CH ₃ ) _2- , -C (CF ₃ ) ₂ -or -SO _2- . The bonding position of each ring of Z ¹ and Z ² and the bonding position of each ring of Z ² and Z ³ are preferably a meta position or a para position for each ring.

It is preferable that the polyimide resin is a polyamideimide having at least a repeating structural unit represented by formula (10) and a repeating structural unit represented by formula (13) from the viewpoint of easy to improve visibility. Moreover, it is preferable that a polyamide resin has at least the repeating structural unit represented by Formula (13).

In one embodiment of the present invention, the polyimide-based resin includes diamines and tetracarboxylic acid compounds (tetracarboxylic acid compound analogs such as acid chloride compounds and tetracarboxylic dianhydrides), If necessary, dicarboxylic acid compounds (dicarboxylic acid compound analogs such as acid chloride compounds), tricarboxylic acid compounds (trichloric acid compound analogs of acid chloride compounds, tricarboxylic acid anhydrides, etc.), etc. It is a condensation type polymer obtained by reacting (polycondensation). The repeating structural unit represented by formula (10) or formula (11) is usually derived from diamine and tetracarboxylic acid compounds. The repeating structural unit represented by formula (12) is usually derived from diamine and tricarboxylic acid compounds. The repeating structural unit represented by formula (13) is usually derived from diamine and dicarboxylic acid compounds.

In one embodiment of the present invention, the polyamide-based resin is a condensation-type polymer obtained by reacting (polycondensing) a diamine and a dicarboxylic acid compound. That is, the repeating structural unit represented by formula (13) is usually derived from diamine and dicarboxylic acid compounds.

Examples of the tetracarboxylic acid compound include aromatic tetracarboxylic acid compounds such as aromatic tetracarboxylic dianhydride; And aliphatic tetracarboxylic acid compounds such as aliphatic tetracarboxylic dianhydride. The tetracarboxylic acid compounds may be used alone or in combination of two or more. In addition to the dianhydride, the tetracarboxylic acid compound may be a tetracarboxylic acid compound analog such as an acid chloride compound.

As a specific example of aromatic tetracarboxylic dianhydride, 4,4'-oxydiphthalic dianhydride, 3,3 ', 4,4'-benzophenone tetracarboxylic dianhydride, 2,2', 3,3'- Benzophenonetetracarboxylic dianhydride, 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride, 2,2', 3,3'-biphenyltetracarboxylic dianhydride, 3,3 ', 4,4'-diphenylsulfonetetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane Dihydrate, 2,2-bis (3,4-dicarboxyphenoxyphenyl) propane dianhydride, 4,4 '-(hexafluoroisopropylidene) diphthalic acid dianhydride (6FDA), 1,2-bis ( 2,3-dicarboxyphenyl) ethane dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,2-bis (3,4-dicarboxyphenyl) ethane dianhydride, 1, 1-bis (3,4-dicarboxyphenyl) ethane dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride and 4,4 '-( and p-phenylenedioxy) diphthalic dianhydride and 4,4 '-(m-phenylenedioxy) diphthalic dianhydride. These can be used alone or in combination of two or more.

Examples of the aliphatic tetracarboxylic dianhydride include a cyclic or acyclic aliphatic tetracarboxylic dianhydride. The cyclic aliphatic tetracarboxylic dianhydride is a tetracarboxylic dianhydride having an alicyclic hydrocarbon structure, and specific examples thereof include 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2, Cycloalkanetetracarboxylic dianhydride, such as 3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, bicyclo [2.2.2] oct-7 -Ene-2,3,5,6-tetracarboxylic dianhydride, dicyclohexyl-3,3 ', 4,4'-tetracarboxylic dianhydride, and positional isomers thereof. These can be used alone or in combination of two or more. Specific examples of the acyclic aliphatic tetracarboxylic dianhydride include 1,2,3,4-butanetetracarboxylic dianhydride, 1,2,3,4-pentanetetracarboxylic dianhydride, and the like. Silver may be used alone or in combination of two or more. Moreover, you may use combining a cyclic aliphatic tetracarboxylic dianhydride and a non-cyclic aliphatic tetracarboxylic dianhydride.

Among the above tetracarboxylic dianhydrides, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, bicyclo [2.2.2] oct-7-ene-2,3 from the viewpoint of high transparency and low colorability Preference is given to, 5,6-tetracarboxylic dianhydride and 4,4 '-(hexafluoroisopropylidene) diphthalic dianhydride, and mixtures thereof. Moreover, as a tetracarboxylic acid, you may use the water addition body of the anhydride of the said tetracarboxylic-acid compound.

Examples of the tricarboxylic acid compound include aromatic tricarboxylic acids, aliphatic tricarboxylic acids, and their flexible acid chloride compounds, acid anhydrides, and the like, and may be used in combination of two or more. Specific examples include anhydrides of 1,2,4-benzenetricarboxylic acid; 2,3,6-naphthalenetricarboxylic acid-2,3-anhydride; And a compound in which phthalic anhydride and benzoic acid are single-linked, -CH _2- , -C (CH ₃ ) _2- , -C (CF ₃ ) _2- , -SO _2- , or a phenylene group.

Examples of the dicarboxylic acid compound include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, their flexible acid chloride compounds, and acid anhydrides, and two or more of them may be used in combination. Specific examples of these include terephthalic acid dichloride (terephthaloyl chloride (TPC)); Isophthalic acid dichloride; Naphthalenedicarboxylic acid dichloride; 4,4'-biphenyldicarboxylic acid dichloride; 3,3'-biphenyldicarboxylic acid dichloride; 4,4'-oxybis (benzoylchloride) (OBBC); A dicarboxylic acid compound of a chain hydrocarbon having 8 or less carbon atoms and two benzoic acid single bonds, -CH _2- , -C (CH ₃ ) _2- , -C (CF ₃ ) _2- , -SO ₂ -or phenylene And compounds linked by groups.

Examples of diamines include aliphatic diamines, aromatic diamines, and mixtures thereof. In addition, in this embodiment, "aromatic diamine" refers to the diamine in which the amino group is directly bonded to the aromatic ring, and may contain an aliphatic group or other substituents in a part of the structure. The aromatic ring may be a monocyclic ring or a condensed ring, and examples thereof include a benzene ring, a naphthalene ring, an anthracene ring and a fluorene ring, but are not limited thereto. Among these, it is preferable that the aromatic ring is a benzene ring. Moreover, "aliphatic diamine" refers to the diamine in which the amino group is directly bonded to the aliphatic group, and may include an aromatic ring or other substituents in a part of the structure.

Examples of the aliphatic diamine include acyclic aliphatic diamines such as hexamethylenediamine and 1,3-bis (aminomethyl) cyclohexane, 1,4-bis (aminomethyl) cyclohexane, norbornanediamine, and 4,4'- And cyclic aliphatic diamines such as diaminodicyclohexylmethane. These can be used alone or in combination of two or more.

Examples of aromatic diamines include p-phenylenediamine, m-phenylenediamine, 2,4-toluenediamine, m-xylylenediamine, p-xylylenediamine, 1,5-diaminonaphthalene, 2,6- Aromatic diamines having one aromatic ring, such as diaminonaphthalene; 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'-dia Minodiphenyl ether, 4,4'-diaminodiphenylsulfone, 3,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, 1,4-bis (4-aminophenoxy) Benzene, 1,3-bis (4-aminophenoxy) benzene, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] sulfone, 2,2- Bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2'-dimethylbenzidine, 2,2'-bis (tri Fluoromethyl) benzidine (2,2'-bis (trifluoromethyl) -4,4'-diaminodiphenyl (TFMB)), 4,4'-bis (4-aminophenoxy) biphenyl, 9 , 9-bis (4-aminophenyl) fluorene, 9,9-bis (4-amino-3-methylphenyl) fluorene, 9,9-bis (4-amino-3-chlorophenyl) fluorene, 9, And aromatic diamines having two or more aromatic rings, such as 9-bis (4-amino-3-fluorophenyl) fluorene. These can be used alone or in combination of two or more.

Among the above diamines, from the viewpoint of high transparency and low coloration, it is preferable to use at least one selected from the group consisting of aromatic diamines having a biphenyl structure, and 2,2'-dimethylbenzidine, 2,2'-bis ( It is more preferable to use at least one member selected from the group consisting of trifluoromethyl) benzidine, 4,4'-bis (4-aminophenoxy) biphenyl and 4,4'-diaminodiphenyl ether, 2 It is even more preferable to use, 2'-bis (trifluoromethyl) benzidine.

The polyimide-based resin is an intermediate obtained after mixing each raw material such as the diamine, tetracarboxylic acid compound, tricarboxylic acid compound, and dicarboxylic acid compound by a conventional method such as stirring. Is obtained by imidizing in the presence of an imidization catalyst and, if necessary, a dehydrating agent. The polyamide-based resin is obtained by mixing each of the raw materials such as the diamine and the dicarboxylic acid compound by a conventional method such as stirring.

The imidization catalyst used in the imidization step is not particularly limited, and examples thereof include aliphatic amines such as tripropylamine, dibutylpropylamine and ethyldibutylamine; Alicyclic amines (monocyclic) such as N-ethylpiperidine, N-propylpiperidine, N-butylpyrrolidine, N-butylpiperidine, and N-propylhexahydroazepine; Alicyclic amines (polycyclic) such as azabicyclo [2.2.1] heptane, azabicyclo [3.2.1] octane, azabicyclo [2.2.2] octane, and azabicyclo [3.2.2] nonane; And 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, 2-ethylpyridine, 3-ethylpyridine, 4-ethylpyridine, 2,4-dimethylpyridine, 2,4,6-trimethylpyridine, 3,4 And aromatic amines such as cyclopentenopyridine, 5,6,7,8-tetrahydroisoquinoline, and isoquinoline.

The dehydrating agent used in the imidization step is not particularly limited, and examples thereof include acetic anhydride, propionic anhydride, isobutyric anhydride, pivalic anhydride, butyric anhydride, and isovaleric anhydride.

In the mixing and imidization step of each raw material, the reaction temperature is not particularly limited, but is, for example, 15 to 350 ° C, preferably 20 to 100 ° C. The reaction time is not particularly limited, but is, for example, about 10 minutes to 10 hours. If necessary, the reaction may be performed under an inert atmosphere or a reduced pressure condition. Moreover, reaction may be performed in a solvent, and what was illustrated as a solvent used for preparation of a varnish is mentioned as a solvent, for example. After the reaction, the polyimide resin or polyamide resin is purified. As a purification method, for example, a poor solvent is added to the reaction solution to precipitate a resin by reprecipitation, dried to extract the precipitate, and if necessary, the precipitate is washed with a solvent such as methanol and dried. have.

Moreover, you may refer the manufacturing method described in Unexamined-Japanese-Patent No. 2006-199945 or Unexamined-Japanese-Patent No. 2008-163107, for example for manufacture of a polyimide type resin. In addition, commercially available products may be used for the polyimide-based resin, and specific examples thereof include Mitsubishi Gas Chemical Company, Inc., Neoprem (registered trademark), and Kawamura Sangyo Co., Ltd. (Kawamura Sangyo Co., Ltd.) ., Ltd) KPI-MX300F.

The weight average molecular weight of the polyimide-based resin or polyamide-based resin is preferably 200,000 or more, more preferably 250,000 or more, more preferably 300,000 or more, preferably 600,000 or less, and more preferably 500,000 or less. The larger the weight-average molecular weight of the polyimide-based resin or polyamide-based resin, the higher the tendency to exhibit high flex resistance when filmed. For this reason, it is preferable that the weight average molecular weight is more than the said lower limit from a viewpoint of raising the bending resistance of a resin film. On the other hand, the smaller the weight-average molecular weight of the polyimide-based resin or polyamide-based resin, the lower the viscosity of the varnish tends to be, and tends to be easy to improve the processability. Moreover, the stretchability of a polyimide-type resin or a polyamide-type resin tends to improve easily. For this reason, from the viewpoint of processability and stretchability, it is preferable that the weight average molecular weight is equal to or less than the above upper limit. In addition, in this application, the weight average molecular weight can be calculated | required by gel permeation chromatography (GPC) measurement and calculated | required by standard polystyrene conversion, for example, can be calculated by the method described in the Example.

The imidation ratio of the polyimide-based resin is preferably 95 to 100%, more preferably 97 to 100%, further preferably 98 to 100%, particularly preferably 100%. From the viewpoint of the stability of the varnish and the mechanical properties of the obtained resin film, it is preferable that the imidation ratio is equal to or greater than the above lower limit. Moreover, the imidation rate can be calculated | required by IR method, NMR method, etc. From the above viewpoint, it is preferable that the imidation ratio of the polyimide resin contained in the varnish is within the above range. The imidation rate can be obtained, for example, by the method described in Japanese Patent Application No. 2018-007523.

In a preferred embodiment of the present invention, the polyimide-based resin or polyamide-based resin contained in the resin film of the present invention can be introduced by, for example, the above fluorine-containing substituents, halogen atoms such as fluorine atoms. You may include. When the polyimide-based resin or the polyamide-based resin contains a halogen atom, it is easy to improve the elastic modulus of the resin film and reduce the yellowness (YI value). When the elastic modulus of the resin film is high, it is easy to suppress the occurrence of scratches and wrinkles in the film, and when the yellowness of the resin film is low, it is easy to improve the transparency of the film. The halogen atom is preferably a fluorine atom. As a preferable fluorine-containing substituent in order to contain a fluorine atom in a polyimide resin or a polyamide resin, a fluoro group and a trifluoromethyl group are mentioned, for example.

The content of the halogen atom in the polyimide-based resin or polyamide-based resin is preferably 1 to 40% by mass, more preferably 5 to 40% by mass, based on the mass of the polyimide-based resin or polyamide-based resin. %, More preferably 5 to 30% by mass. When the content of the halogen atom is 1% by mass or more, the elastic modulus at the time of film formation is further improved, the absorption rate is lowered, the yellowness (YI value) is further reduced, and the transparency is more easily improved. When the content of the halogen atom is 40% by mass or less, synthesis may be easy.

In one embodiment of the present invention, the content of the polyimide-based resin and / or polyamide-based resin in the resin film is preferably 40% by mass or more, more preferably based on the total mass of the resin film. 50 mass% or more, More preferably, it is 70 mass% or more. The content of the polyimide-based resin and / or the polyamide-based resin is more than the above lower limit, and it is preferable from the viewpoint of easy to increase bending resistance and the like. The content of the polyimide-based resin and / or polyamide-based resin in the resin film is usually 100% by mass or less based on the total mass of the resin film.

(additive)

The resin film of the present invention may further contain an additive. Examples of such additives include silica particles, ultraviolet absorbers, brighteners, silica dispersants, antioxidants, pH adjusters, and leveling agents.

(Silica particles)

The resin film of the present invention may further contain silica particles as an additive. The content of the silica particles is preferably 1% by mass or more, more preferably 3% by mass or more, more preferably 5% by mass or more, and preferably 60% by mass or less, based on the total mass of the resin film. , More preferably, it is 50 mass% or less, More preferably, it is 45 mass% or less. Moreover, content of a silica particle can select and combine arbitrary lower limit and an upper limit among these upper limit and a lower limit. If the content of the silica particles is in the numerical range of the upper and / or lower limits, the resin film of the present invention is difficult to aggregate, and the particles tend to be uniformly dispersed in the primary particle state. The decrease in visibility can be suppressed.

The particle size of the silica particles is preferably 1 nm or more, more preferably 3 nm or more, more preferably 5 nm or more, particularly preferably 8 nm or more, preferably 30 nm or less, more preferably 28 nm or less, and more preferably Is 25 nm or less, particularly preferably 20 nm or less. The particle diameter of the silica particles can be combined by selecting an arbitrary lower limit and an upper limit from these upper and lower limits. When the content of the silica particles is in the numerical range of the upper limit and / or lower limit, the resin film of the present invention is difficult to interact with light of a specific wavelength in white light, and thus the visibility of the resin film of the present invention is lowered. Can be suppressed. In this specification, the particle diameter of the silica particles represents the average primary particle diameter. The particle diameter of the silica particles in the resin film can be measured by imaging using a transmission electron microscope (TEM). The particle diameter of the silica particles before producing the resin film (for example, before adding to the varnish) can be measured by a laser diffraction particle size distribution system. The method for measuring the particle diameter of the silica particles is described in detail in Examples.

Examples of the form of the silica particles include silica sol in which the silica particles are dispersed in an organic solvent and the like, and silica powder prepared by a gas phase method. Among these, silica sol is preferable from the viewpoint of workability.

The silica particles may be subjected to a surface treatment or may be, for example, silica particles substituted with a solvent (more specifically, γ-butyrolactone) from a water-soluble alcohol-dispersed silica sol. The water-soluble alcohol is an alcohol having 3 or less carbon atoms per hydroxy group in one water-soluble alcohol molecule, and examples thereof include methanol, ethanol, 1-propanol, and 2-propanol. According to the reciprocity of the type of the silica particles and the polyimide resin or polyamide resin, usually, when the silica particles are surface treated, the compatibility between the polyimide resin contained in the resin film is improved, and the silica particles Since the dispersibility tends to be improved, the decrease in visibility of the present invention can be suppressed.

(Ultraviolet absorbent)

The resin film of the present invention may further include an ultraviolet absorber. Examples thereof include triazine-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, benzoate-based ultraviolet absorbers, and cyanoacrylate-based ultraviolet absorbers. These may be used alone or in combination of two or more. Suitable commercially available ultraviolet absorbers include, for example, Sumisorb (registered trademark) 340 manufactured by Sumika Chemtex Company, Limited, Adekastab (registered trademark) LA-31 manufactured by ADEKA Corporation, and And Tinuvin (registered trademark) 1577 manufactured by BASF Japan Corporation. The content of the ultraviolet absorber is preferably 1 phr or more and 10 phr or less, more preferably 3 phr or more and 6 phr or less, based on the mass of the resin film of the present invention.

(Whitening agent)

The resin film of the present invention may further contain a brightener. The brightener can be added, for example, in order to adjust the color sense when additives other than the brightener are added. Examples of the brightener include monoazo dyes, triarylmethane dyes, phthalocyanine dyes, and anthraquinone dyes. Among these, anthraquinone-based dyes are preferred. Suitable commercially available brighteners include, for example, Macrolex (registered trademark) Violet B manufactured by LANXESS, Sumiplast (registered trademark) Violet B manufactured by Sumika Chemtex, and Mitsubishi Chemical Co., Ltd. And Diaresin (registered trademark) Blue G manufactured by (Mitsubishi Chemical Corporation). These may be used alone or in combination of two or more. The content of the brightener is preferably 0 to 50 ppm, more preferably 1 to 45 ppm, further preferably 3 to 40 ppm, particularly preferably 5 to 35 ppm, based on the mass of the resin film of the present invention.

(Manufacturing method of raw film)

Although the raw material film is not particularly limited, for example, it can be produced by a method including the following steps.

(a) a varnish preparation step of preparing a liquid (hereinafter sometimes referred to as varnish) containing the resin and the filler,

(b) a coating step of applying a varnish to the substrate to form a coating film, and

(c) A forming step of drying the coating film to form a raw film.

In the varnish preparation step, the varnish is prepared by dissolving the resin in a solvent and adding and stirring the above filler and other additives as necessary. Moreover, when using silica as a filler, you may add the silica sol which substituted the dispersion of the silica sol containing silica with the solvent which the said resin is soluble, for example, the solvent used for preparation of the following varnish to resin.

The solvent used for the preparation of the varnish is not particularly limited as long as the resin can be dissolved. Examples of such a solvent include amide solvents such as N, N-dimethylacetamide (DMAc) and N, N-dimethylformamide; lactone-based solvents such as γ-butyrolactone (GBL) and γ-valerolactone; Sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide and sulfolane; Carbonate-based solvents such as ethylene carbonate and propylene carbonate; And combinations thereof. Among these, an amide-based solvent or a lactone-based solvent is preferable. These solvents may be used alone or in combination of two or more. Moreover, the varnish may contain water, an alcohol solvent, a ketone solvent, an acyclic ester solvent, an ether solvent, and the like. The solid content concentration of the varnish is preferably 1 to 25% by mass, more preferably 5 to 20% by mass.

In the coating step, a varnish is coated on the substrate by a known coating method to form a coating film. As a known coating method, for example, a wire bar coating method, a reverse coating method, a roll coating method such as gravure coating, a die coating method, a comma coating method, a lip coating method, a spin coating method, a screen coating method, a fountain coating method, a di And a ping method, a spraying method, and a flexible molding method.

In a forming process, a raw film can be formed by drying and peeling a coating film from a base material. Drying of the coating film can be usually performed at a temperature of 50 to 350 ° C. If necessary, the coating film may be dried under an inert atmosphere or under reduced pressure. Although the obtained raw material film is supplied to the said heating process, it may be conveyed continuously and supplied to a heating process, or may be supplied after it is once wound up.

Examples of the base material include endless SUS belts for metals, PET films for resins, PEN films, other polyimide resins or polyamide resin films, cycloolefin polymer (COP) films, and acrylic films. Especially, a PET film, a COP film, etc. are preferable from a viewpoint of excellent smoothness and heat resistance, and a PET film is more preferable from a viewpoint of adhesiveness with a resin film and cost.

The raw material film may be a laminate by laminating a surface protection film on its surface, and the laminated surface protection film may be peeled off before the heating step is performed. The surface protection film is laminated on a surface opposite to the base material of the raw film. When winding up a laminated body in roll form, when there is a problem with winding property, such as blocking, further, a raw material film of a base material may laminate a surface protection film on the surface on the opposite side. The surface protection film bonded to the raw material film is a film for temporarily protecting the surface of the raw material film, and is not particularly limited as long as it is a peelable film capable of protecting the surface of the raw material film. For example, polyester resin films, such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; And polyolefin-based resin films such as polyethylene and polypropylene films, and acrylic-based resin films, and are preferably selected from the group consisting of polyolefin-based resin films, polyethylene terephthalate-based resin films, and acrylic-based resin films. When the surface protection film is stuck on both surfaces of a laminated body, the surface protection film of each surface may be mutually same or different.

Although the thickness of a surface protection film is not specifically limited, Usually, it is 10-100 micrometers, Preferably it is 10-80 micrometers. When the surface protection film is pasted on both surfaces of the laminate, the thickness of the surface protection film on each surface may be the same or different.

The above-mentioned layered product (base material, raw material film and surface protection film if necessary) is wound in a roll form to a core, and is referred to as a layered film roll. In the case of continuous production, the laminate film roll is often stored in the form of a film roll once from space or other constraints, and the laminate film roll is one of them.

As a material constituting the core of the laminated film roll, for example, polyethylene resin, polypropylene resin, polyvinyl chloride resin, polyester resin, epoxy resin, phenol resin, melamine resin, silicon resin, polyurethane resin, polycarbonate resin , ABS resin and other synthetic resins; Metals such as aluminum; And fiber-reinforced plastics (FRP: composite materials containing fibers such as glass fibers in plastics to improve strength) and the like. The winding core has a shape such as a cylindrical shape or a cylindrical shape, and its diameter is, for example, 80 to 170 mm. Moreover, although the diameter (diameter after winding) of a film roll is not specifically limited, Usually, it is 200-800 mm.

<Use of resin film>

The resin film of the present invention may be used as a single layer of a resin film or may be used as a laminate in which other layers are laminated. Since this resin film or a laminate containing the same has excellent surface quality, it is useful as an optical film in an image display device or the like, especially as a front panel (window film) of a flexible display.

Examples of other layers that can be laminated on the resin film include a layer (functional layer) having various functions such as a hard coat layer, an ultraviolet absorbing layer, an adhesive layer, a refractive index adjusting layer, and a primer layer. The resin film may be provided with a single or multiple functional layers. Moreover, one functional layer may have a plurality of functions.

Further, examples of layers other than the functional layer include a polarizing film, a polarizing plate, a touch sensor, an optical member provided by a display device, such as a colored light-shielding pattern printed around a border having a single layer or multiple layers.

It is preferable that the hard coat layer is disposed on the viewer-side surface of the film. The hard coat layer may have a single layer structure or a multilayer structure. The hard coat layer can be formed by curing a composition for a hard coat containing a reactive material that forms a crosslinked structure by irradiating light or thermal energy.

As a reactive material, light or a thermosetting resin is mentioned. Examples thereof include ultraviolet curing type, electron beam curing type or heat curing type such as acrylic resins such as (meth) acrylate monomers and oligomers, epoxy resins, urethane resins, benzyl chloride resins, vinyl resins, silicone resins or mixed resins thereof. And resin. From the viewpoints of mechanical properties such as surface hardness and industrial viewpoint, it is preferable that the composition for a hard coat contains an acrylic resin.

The composition for a hard coat may contain a solvent and a photopolymerization initiator as needed in addition to the resin. Alternatively, the composition for the hard coat may contain additives such as inorganic fillers, leveling agents, stabilizers, antioxidants, UV absorbers, surfactants, lubricants, antifouling agents, and the like within a range not impairing the effects of the invention.

The hard coat layer can be formed by applying a hard coat composition to at least one surface of the resin film obtained by the present invention and curing it. The thickness of the hard coat layer is not particularly limited, and may be, for example, 5 to 100 μm. When the thickness of the hard coat layer is within the above range, it is possible to ensure sufficient surface hardness, and also, the flexural resistance is less likely to decrease, and there is a tendency that the problem of curling due to curing shrinkage is less likely to occur.

The ultraviolet absorbing layer is a layer having a function of absorbing ultraviolet rays. For example, a main material selected from an ultraviolet curable transparent resin, an electron beam curable transparent resin, and a heat curable transparent resin, and dispersed in the main material It is composed of ultraviolet absorbers. By providing an ultraviolet absorbing layer as a functional layer, a change in yellowness due to light irradiation can be easily suppressed.

The adhesive layer is a layer having an adhesive function, and has a function of adhering the film of the present invention to another member. As a material for forming the adhesive layer, a commonly known one can be used. For example, a thermosetting resin composition or a photocurable resin composition can be used.

The adhesive layer may be composed of a resin composition containing a component having a polymerizable functional group. In this case, strong adhesion can be realized by further polymerizing the resin composition constituting the adhesive layer after the film is brought into close contact with the other member. The adhesive strength of the film of the present invention and the adhesive layer may be 0.1 N / cm or more, or 0.5 N / cm or more.

The adhesive layer may contain a thermosetting resin composition or a photocurable resin composition as a material. In this case, the resin composition can be polymerized and cured by supplying energy afterwards.

The adhesive layer may be a layer composed of an adhesive that is adhered to an object by pressing under pressure, called a pressure sensitive adhesive (PSA). The pressure-sensitive adhesive may be a pressure-sensitive adhesive that is `` a substance having tackiness at room temperature and adheres to an adherend at light pressure '' (JIS K 6800), and `` contains a specific component in a protective film (microcapsule), pressure, heat, etc. It may be a capsule adhesive, which is an adhesive capable of maintaining stability until the film is destroyed by suitable means of (JIS K 6800).

The color adjustment layer is a layer having a function of color adjustment, and is a layer that can be adjusted to the color targeting the film of the present invention. The color adjustment layer is, for example, a layer containing a resin and a colorant. Examples of the colorant include inorganic pigments such as titanium oxide, zinc oxide, bengala, titanium oxide-based fired pigments, ultramarine, cobalt aluminate, and carbon black; Organic pigments such as azo-based compounds, quinacridone-based compounds, anthraquinone-based compounds, perylene-based compounds, isoindolinone-based compounds, phthalocyanine-based compounds, quinophthalone-based compounds, styrene-based compounds, and diketopyrrolopyrrole-based compounds; Extender pigments such as barium sulfate and calcium carbonate; And dyes such as basic dyes, acid dyes and mordant dyes.

The refractive index adjusting layer is a layer having a function of adjusting the refractive index, and has a different refractive index from the layer containing the polyamideimide resin A in the film of the present invention, and can give a predetermined refractive index to the film of the present invention. It is a layer. The refractive index adjusting layer may be, for example, an appropriately selected resin, and a resin layer containing a pigment even more in some cases, or a thin metal film.

Examples of the pigment for adjusting the refractive index include silicon oxide, aluminum oxide, antimony oxide, tin oxide, titanium oxide, zirconium oxide, and tantalum oxide. The average primary particle size of the pigment may be 0.1 μm or less. By setting the average primary particle size of the pigment to 0.1 μm or less, diffuse reflection of light passing through the refractive index adjusting layer can be prevented, and a decrease in transparency can be prevented.

Examples of the metal used in the refractive index adjusting layer include metals such as titanium oxide, tantalum oxide, zirconium oxide, zinc oxide, tin oxide, silicon oxide, indium oxide, titanium oxynitride, titanium nitride, silicon oxynitride and silicon nitride. Oxides or metal nitrides.

The optical member laminated on the resin film may be laminated on the resin film via an adhesive layer or an adhesive layer, or may be laminated without an adhesive layer or an adhesive layer.

<Flexible image display device>

The present invention includes a flexible display device provided with the optical film. The optical film of the present invention is preferably used as a front plate in a flexible image display device, and the front plate may be called a window film. The flexible image display device is composed of a laminate for a flexible image display device and an organic EL display panel, and a laminate for a flexible image display device is disposed on the viewer side with respect to the organic EL display panel, and is configured to be bendable. As a laminate for a flexible image display device, a polarizing plate and a touch sensor may be further included, and the lamination order thereof is arbitrary, but in the order of a window film, a polarizing plate, a touch sensor or a window film, a touch sensor and a polarizing plate from the viewing side. It is preferable that they are laminated. When the polarizing plate is present on the viewing side than the touch sensor, it is preferable because the pattern of the touch sensor is difficult to visualize and the visibility of the display image is improved. Each member can be laminated using an adhesive, an adhesive, or the like. In addition, a light blocking pattern formed on at least one surface of any one of the window film, the polarizing plate, and the touch sensor may be provided.

[Polarizing plate]

As described above, the flexible display device of the present invention includes a polarizing plate, preferably a circular polarizing plate. The circular polarizing plate is a functional layer having a function of transmitting only the right or left circularly polarized components by laminating a λ / 4 phase difference plate on the linear polarizing plate. For example, it is used to convert external light into right-circular polarization, block external light reflected from the organic EL panel and become left-circular polarization, and transmit only the light-emitting component of the organic EL to suppress the influence of reflected light and make the image easier to see. In order to achieve the circular polarization function, the absorption axis of the linear polarizing plate and the slow axis of the λ / 4 retardation plate need to be theoretically 45 °, but practically 45 ± 10 °. The linear polarizing plate and the λ / 4 retardation plate do not necessarily need to be stacked adjacently, and the relationship between the absorption axis and the slow axis may satisfy the above-described range. Although it is desirable to achieve full circular polarization for the entire wavelength, the circular polarizing plate in the present invention also includes an elliptical polarizing plate because it is not necessary in practice. It is also desirable to further improve the visibility in a state in which polarized sunglasses are put on by further stacking a λ / 4 phase difference film on the viewing side of the linear polarizing plate and making the emitted light circularly polarized.

The linear polarizing plate is a functional layer having a function of passing light oscillating in the direction of the transmission axis, but blocking polarization of a vibration component perpendicular to it. The linear polarizer may be configured with a linear polarizer alone or a linear polarizer and a protective film attached to at least one surface thereof. The thickness of the linear polarizing plate may be 200 μm or less, and preferably 0.5 to 100 μm. When the thickness of the linear polarizing plate is within the above range, the flexibility of the linear polarizing plate tends to be difficult to deteriorate.

The linear polarizer may be a film-type polarizer produced by dyeing and stretching a polyvinyl alcohol (hereinafter sometimes abbreviated as PVA) -based film. A dichroic dye such as iodine is adsorbed to a PVA-based film oriented by stretching, or stretched in a state adsorbed to PVA to orient the dichroic dye to exhibit polarization performance. In the production of the above-mentioned film type polarizer, other processes such as swelling, crosslinking with boric acid, washing with an aqueous solution, and drying may be performed. The stretching or dyeing process may be performed alone with a PVA-based film, or may be carried out in a state of being laminated with another film such as polyethylene terephthalate. The thickness of the PVA-based film used is preferably 10 to 100 μm, and the stretching ratio is preferably 2 to 10 times.

Moreover, as another example of the said polarizer, the liquid crystal coating type polarizer formed by apply | coating a liquid crystal polarizing composition is mentioned. The liquid crystal polarizing composition may include a liquid crystal compound and a dichroic dye compound. The above-mentioned liquid crystal compound should have the property of showing a liquid crystal state, and it is preferable because it can exhibit high polarization performance especially if it has a high degree of alignment state, such as a smectic phase. Moreover, it is preferable that a liquid crystal compound has a polymerizable functional group.

The dichroic dye compound may be oriented with the liquid crystal compound to exhibit dichroism, and may have a polymerizable functional group, or the dichroic dye itself may have liquid crystallinity.

Any of the compounds included in the liquid crystal polarizing composition has a polymerizable functional group. The liquid crystal polarizing composition may further include an initiator, a solvent, a dispersant, a leveling agent, a stabilizer, a surfactant, a crosslinking agent, and a silane coupling agent.

The said liquid crystal polarizing layer is manufactured by apply | coating a liquid crystal polarizing composition on an alignment film, and forming a liquid crystal polarizing layer. The liquid crystal polarizing layer can have a thickness thinner than that of the film-type polarizer, and the thickness is preferably 0.5 to 10 μm, more preferably 1 to 5 μm.

The alignment film is produced, for example, by applying an alignment film-forming composition on a substrate and imparting alignment property by rubbing, polarization irradiation, or the like. The alignment film forming composition contains an alignment agent, and may further include a solvent, a crosslinking agent, an initiator, a dispersing agent, a leveling agent, a silane coupling agent, and the like. Examples of the alignment agent include polyvinyl alcohols, polyacrylates, polyamic acids, and polyimides. When using the alignment agent which gives orientation by polarization irradiation, it is preferable to use the alignment agent containing a cinnamate group. The weight average molecular weight of the polymer used as the alignment agent is, for example, about 10,000 to 1,000,000. The thickness of the alignment film is preferably 5 to 10,000 nm, and more preferably 10 to 500 nm from the viewpoint of sufficiently expressing the orientation regulating force.

The liquid crystal polarizing layer may be peeled off from the substrate and transferred and laminated, or the substrate may be laminated as it is. It is also preferable that the substrate serves as a transparent substrate for the protective film, retardation plate, and window film.

As the protective film, a transparent polymer film may be used, and materials such as materials and additives used in the transparent base material of the window film can be used. Moreover, the coating type protective film obtained by apply | coating and curing a cationic ion curing composition, such as an epoxy resin, or a radical curing composition, such as an acrylate, may be sufficient. The protective film may contain a plasticizer, an ultraviolet absorber, an infrared absorber, a colorant such as a pigment or dye, a fluorescent brightener, a dispersant, a heat stabilizer, a light stabilizer, an antistatic agent, an antioxidant, a lubricant, a solvent, and the like, if necessary. . The thickness of the protective film is preferably 200 μm or less, and more preferably 1 to 100 μm. When the thickness of the protective film is in the above range, the flexibility of the film tends to be difficult to deteriorate.

The lambda / 4 phase difference plate is a film that gives a lambda / 4 phase difference in a direction orthogonal to the traveling direction of the incident light (in-plane direction of the film). The λ / 4 retardation plate may be a stretched retardation plate produced by stretching a polymer film such as a cellulose-based film, an olefin-based film, or a polycarbonate-based film. The λ / 4 retardation plate is a retardation regulator, a plasticizer, an ultraviolet absorber, an infrared absorber, a colorant such as a pigment or dye, a fluorescent brightener, a dispersant, a heat stabilizer, a light stabilizer, an antistatic agent, an antioxidant, a lubricant, and a solvent, if necessary. Etc. may be included.

The thickness of the stretched retardation plate is preferably 200 μm or less, and more preferably 1 to 100 μm. When the thickness of the stretched retardation plate is within the above range, the flexibility of the stretched retardation plate tends to be difficult to deteriorate.

Moreover, as another example of the (lambda) / 4 retardation plate, the liquid crystal coating type retardation plate formed by apply | coating a liquid crystal composition is mentioned.

The liquid crystal composition contains a liquid crystal compound that exhibits liquid crystal states such as nematic, cholesteric, and smectic. The liquid crystal compound has a polymerizable functional group.

The liquid crystal composition may further include an initiator, a solvent, a dispersant, a leveling agent, a stabilizer, a surfactant, a crosslinking agent, and a silane coupling agent.

The liquid crystal coating-type retardation plate can be produced by coating and curing a liquid crystal composition on a base, as in the liquid crystal polarizing layer, to form a liquid crystal retardation layer. The liquid crystal-coated retardation plate can be formed to have a thinner thickness than the stretched retardation plate. The thickness of the liquid crystal polarizing layer is preferably 0.5 to 10 μm, more preferably 1 to 5 μm.

The liquid crystal coating type retardation plate may be peeled off from a substrate, transferred, and laminated, or the substrate may be laminated as it is. It is also preferable that the substrate serves as a transparent substrate for the protective film, retardation plate, and window film.

In general, the shorter the wavelength, the greater the birefringence, and the longer the longer the wavelength, the smaller the material exhibiting the birefringence. In this case, since the phase difference of λ / 4 cannot be achieved in the entire visible light region, the in-plane retardation is preferably 100 to 180 nm, more preferably 130 to 150 nm, so that it becomes λ / 4 in the vicinity of 560 nm with high visibility. It is designed to be. The reverse dispersion λ / 4 retardation plate using a material having a birefringence wavelength dispersion characteristic as opposed to normal is preferable in view of good visibility. As such a material, for example, those described in Japanese Unexamined Patent Publication No. 2007-232873 and the like, as described in Japanese Unexamined Patent Publication No. 2010-30979, can be used.

As another method, a technique of obtaining a broadband λ / 4 phase difference plate by combining with a λ / 2 phase difference plate is also known (for example, JP-A-10-90521). The λ / 2 phase difference plate is also manufactured by the same material method as the λ / 4 phase difference plate. The combination of the stretched retardation plate and the liquid crystal coating retardation plate is arbitrary, but both can be made thinner by using the liquid crystal coating retardation plate.

In order to increase visibility in the oblique direction, a method of laminating a positive C plate is known to the original polarizing plate (for example, JP 2014-224837 A). The definition C plate may be a liquid crystal coated retardation plate or a stretched retardation plate. The phase difference in the thickness direction of the retardation plate is preferably -200 to -20 nm, more preferably -140 to -40 nm.

[Touch sensor]

It is preferable that the flexible display device of the present invention has a touch sensor as described above. The touch sensor is used as an input means. As a touch sensor, various forms, such as a resistive film method, a surface acoustic wave method, an infrared method, an electromagnetic induction method, and a capacitive method, are mentioned, Preferably, a capacitive method is mentioned.

The capacitive touch sensor is divided into an active area and an inactive area located on an outer portion of the active area. The active area is an area corresponding to an area (display area) where a screen is displayed on the display panel, and an area where a user's touch is detected, and an inactive area is an area corresponding to an area (non-display area) where a screen is not displayed on the display device. . The touch sensor includes a substrate having flexible characteristics, a sensing pattern formed in an active region of the substrate, and a sensing pattern formed in an inactive region of the substrate and connected to an external driving circuit through the sensing pattern and the pad portion. can do. As a substrate having flexible properties, a material similar to the transparent substrate of the window film can be used.

The sensing pattern may include a first pattern formed in a first direction and a second pattern formed in a second direction. The first pattern and the second pattern are arranged in different directions. The first pattern and the second pattern are formed on the same layer, and in order to sense a touched point, each pattern must be electrically connected. The first pattern is a form in which a plurality of unit patterns are connected to each other through a seam, but the second pattern is a structure in which a plurality of unit patterns are separated from each other in an island form, so a separate bridge is used to electrically connect the second pattern. Electrodes are required. A well-known transparent electrode can be applied to the electrode for connecting the second pattern. As a material of the transparent electrode, for example, indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), indium zinc tin oxide (IZTO), indium gallium zinc oxide (IGZO), cadmium tin oxide ( CTO), PEDOT (poly (3,4-ethylenedioxythiophene)), carbon nanotubes (CNT), graphene, metal wires, and the like, and preferably ITO. These can be used alone or in combination of two or more. The metal used for the metal wire is not particularly limited, and examples thereof include silver, gold, aluminum, copper, iron, nickel, titanium, selenium, and chromium. These may be used alone or in combination of two or more. .

The bridge electrode may be formed on the insulating layer over the sensing pattern, and the bridge electrode may be formed on the substrate, and an insulating layer and the sensing pattern may be formed thereon. The bridge electrode may be formed of a material such as a sensing pattern, or may be formed of molybdenum, silver, aluminum, copper, palladium, gold, platinum, zinc, tin, titanium, or an alloy of two or more of them.

Since the first pattern and the second pattern must be electrically insulated, an insulating layer is formed between the sensing pattern and the bridge electrode. The insulating layer may be formed only between the seam of the first pattern and the bridge electrode, or may be formed as a layer covering the entire sensing pattern. In the case of the layer covering the entire sensing pattern, the bridge electrode may connect the second pattern through the contact hole formed in the insulating layer.

The touch sensor may be configured to detect a difference in transmittance between a pattern area where a sensing pattern is formed and a non-pattern area where no sensing pattern is formed, specifically, a difference in light transmittance caused by a difference in refractive index in these areas. As a means for properly compensating, an optical control layer may be further included between the substrate and the electrode. The optical control layer may include an inorganic insulating material or an organic insulating material. The optical control layer may be formed by coating a photocurable composition comprising a photocurable organic binder and a solvent on a substrate. The photocurable composition may further include inorganic particles. The refractive index of the optical control layer can be increased by the inorganic particles.

The photocurable organic binder may include, for example, copolymers of monomers such as acrylate-based monomers, styrene-based monomers, and carboxylic acid-based monomers, in a range that does not impair the effects of the present invention. The photocurable organic binder may be, for example, a copolymer containing different repeating units such as an epoxy group-containing repeating unit, an acrylate repeating unit, and a carboxylic acid repeating unit.

Examples of the inorganic particles include zirconia particles, titania particles, and alumina particles.

The photocurable composition may further include additives such as a photopolymerization initiator, a polymerizable monomer, and a curing aid.

[Adhesive layer]

Each layer (window film, circular polarizing plate, touch sensor) forming the laminate for the flexible image display device, and the film member (linear polarizing plate, λ / 4 retardation plate, etc.) constituting each layer can be bonded by an adhesive. Examples of the adhesive include water-based adhesives, water-based solvent-based adhesives, organic solvent-based, solvent-free adhesives, solid adhesives, solvent-volatile adhesives, moisture-curable adhesives, heat-curable adhesives, anaerobic curing type, active energy ray-curable adhesives, and curing agent mixed adhesives. Hot melt adhesives, pressure sensitive adhesives (adhesives), rewet adhesives, and other commonly used adhesives can be used. Preferably, a water-based solvent volatilization adhesive, an active energy ray-curable adhesive, or an adhesive can be used. The thickness of the adhesive layer can be appropriately adjusted according to the required adhesive strength, and is preferably 0.01 to 500 μm, more preferably 0.1 to 300 μm. Although the plurality of adhesive layers exist in the laminate for the flexible image display device, the thickness and type of each may be the same or different.

As the aqueous solvent-based adhesive, a water-dispersible polymer such as a polyvinyl alcohol-based polymer, a water-soluble polymer such as starch, an ethylene-vinyl acetate-based emulsion, or a styrene-butadiene-based emulsion can be used as the main polymer. In addition to the above main polymer and water, a crosslinking agent, a silane compound, an ionic compound, a crosslinking catalyst, an antioxidant, a dye, a pigment, an inorganic filler, an organic solvent, etc. may be blended. In the case of bonding with the water-based solvent volatilization-type adhesive, the water-based solvent volatilization-type adhesive is injected between the adhesive layers to bond the adhesive layers, followed by drying to impart adhesiveness. In the case of using the water-based solvent-based adhesive, the thickness of the adhesive layer is preferably 0.01 to 10 μm, more preferably 0.1 to 1 μm. When the above-mentioned water-based solvent volatilization type adhesive is used for a plurality of layers, the thickness or type of each layer may be the same or different.

The active energy ray-curable adhesive may be formed by curing an active energy ray-curing composition comprising a reactive material that irradiates active energy rays to form an adhesive layer. The active energy ray-curable composition may contain at least one polymerizable product of a radically polymerizable compound and a cationic ion polymerizable compound similar to those contained in the hard coat composition. As the radically polymerizable compound, a compound similar to the radically polymerizable compound in the hard coat composition can be used.

As the cationic ion-polymerizable compound, the same compound as the cationic ion-polymerizable compound in the hard coat composition can be used.

As the cation ion polymerizable compound used in the active energy ray curing composition, an epoxy compound is particularly preferred. It is also preferable to include a monofunctional compound as a reactive diluent in order to lower the viscosity as an adhesive composition.

The active energy ray composition may contain a monofunctional compound in order to lower the viscosity. As the monofunctional compound, an acrylate-based monomer having one (meth) acryloyl group in one molecule or a compound having one epoxy group or oxetanyl group in one molecule, for example, glycidyl (meth) acrylic Rate etc. are mentioned.

The active energy ray composition may further include a polymerization initiator. Examples of the polymerization initiator include a radical polymerization initiator, a cationic ion polymerization initiator, a radical and a cationic ion polymerization initiator, and these are suitably selected and used. These polymerization initiators are decomposed by at least one of active energy ray irradiation and heating to generate radical or cation ions to advance radical polymerization and cation ion polymerization. Among the substrates for the hard coat composition, an initiator capable of initiating at least either radical polymerization or cationic ion polymerization by active energy ray irradiation can be used.

The active energy ray curing composition may further include an ion trapping agent, an antioxidant, a chain transfer agent, an adhesion imparting agent, a thermoplastic resin, a filler, a flow viscosity modifier, a plasticizer, a defoamer solvent, an additive, and a solvent. When the two to-be-adhesive layers are adhered by the active energy ray-curable adhesive, the active energy ray-curable composition is applied to one or both of the to-be-adhesive layers and then bonded, and the active energy is applied to either or both of the adhered layers. It can bond by irradiating a line and hardening it. When using the active energy ray-curable adhesive, the thickness of the adhesive layer is preferably 0.01 to 20 μm, more preferably 0.1 to 10 μm. When the active energy ray-curable adhesive is used to form a plurality of adhesive layers, the thickness or type of each layer may be the same or different.

As the above-mentioned pressure-sensitive adhesive, depending on the main polymer, acrylic pressure-sensitive adhesive, urethane-based pressure-sensitive adhesive, rubber-based pressure-sensitive adhesive, silicone pressure-sensitive adhesive, etc. may be used. In addition to the main polymer, a crosslinking agent, a silane compound, an ionic compound, a crosslinking catalyst, an antioxidant, a tackifier, a plasticizer, a dye, a pigment, an inorganic filler, etc. may be added to the adhesive. The adhesive layer is formed by dissolving and dispersing each component constituting the pressure-sensitive adhesive in a solvent to obtain a pressure-sensitive adhesive composition, and then applying the pressure-sensitive adhesive composition to a substrate and drying it. The adhesive layer may be formed directly, or may be transferred to one formed on a separate substrate. It is also preferable to use a release film to cover the adhesive surface before adhesion. When using the active energy ray-curable adhesive, the thickness of the adhesive layer is preferably 0.1 to 500 μm, more preferably 1 to 300 μm. When using multiple layers of the said adhesive, the thickness and kind of each layer may be the same or different.

[Shading pattern]

The light-shielding pattern can be applied as at least a part of the bezel or housing of the flexible image display device. Visibility of the image is improved by shielding the wiring arranged at the edge portion of the flexible image display device by the light-shielding pattern, making it difficult to visually recognize. The light shielding pattern may be in the form of a single layer or multiple layers. The color of the light shielding pattern is not particularly limited, and various colors such as black, white, and metallic may be used. The light-shielding pattern may be formed of a pigment for realizing color, and a polymer such as acrylic resin, ester resin, epoxy resin, polyurethane, and silicone. These may be used alone or as a mixture of two or more. The light-shielding pattern can be formed by various methods such as printing, lithography, and inkjet. The thickness of the light shielding pattern is preferably 1 to 100 μm, more preferably 2 to 50 μm. Moreover, it is also preferable to give a shape, such as a slope, in the thickness direction of a light-shielding pattern.

Example

Hereinafter, the present invention will be described in more detail by examples. In the examples, "%" and "parts" mean mass% and parts by mass unless otherwise specified. Among the examples, the measurement method and evaluation method of each item were performed by the following method.

(Resin film thickness)

Using a micrometer ("ID-C112XBS" manufactured by Mitutoyo Corporation), the thickness of the resin film of 10 points or more was measured, and the average value was calculated.

(Total light transmittance and haze of resin film)

The total light transmittance and haze of the resin film are based on JIS K 7361-1: 1997 and JIS K 7136: 2000, respectively, and are fully automated direct reading haze computers HGM- manufactured by Suga Test Instruments Co., Ltd. It measured using 2DP. The measurement sample was produced by cutting the resin films of Examples and Comparative Examples to a size of 30 mm × 30 mm. In Table 2, the total light transmittance is described as Tt.

(Yellowness of resin film)

The yellowness (Yellow Index: YI value) of the resin film was measured using an ultraviolet visible near-infrared spectrophotometer ("V-670" manufactured by JASCO Corporation) according to JIS K 7373: 2006. did. After performing the background measurement in the absence of a sample, the resin films obtained in Examples and Comparative Examples were set in a sample holder, and the transmittance of 300-800 nm was measured for light to obtain three stimulus values (X, Y, Z). I got it. Based on the standard of ASTM D1925 from the obtained tristimulus value, YI value was computed based on the following formula. In addition, in Table 2, the yellowness of the resin film is described as YI.

YI = 100 × (1.2769X-1.0592Z) / Y

(Measurement of thermal weight-differential heat (TG-DTA))

TG / DTA6300 manufactured by Hitachi High-Tech Science Co., Ltd. was used as the measuring device for the TG-DTA. About 20 mg of sample was obtained from the produced resin film. The sample was heated from room temperature to 120 ° C. at a heating rate of 10 ° C./min, held for 5 minutes at 120 ° C., and then heated under the conditions of heating at 400 ° C. at a heating rate of 10 ° C./min. Measured.

From the TG-DTA measurement results, the weight loss rate M (%) from 120 ° C to 250 ° C was calculated by the following formula.

M (%) = 100- (W ₁ / W ₀ ) × 100

Here, W ₀ represents the weight of the sample after holding at 120 ° C for 5 minutes, and W ₁ represents the weight of the sample at 250 ° C.

(Measurement of in-plane retardation value of resin film)

The in-plane retardation of the resin film is an in-plane retardation value R having a wavelength of 590 nm using a retardation film / optical material inspection apparatus (trade name "RETS-100") manufactured by Otsuka Electronics Co., Ltd. Measured. The measurement took a range of 700 mm in width around the center of the width direction of the resin film, divided the range of the 700 mm width into 20 mm intervals, and performed on 36 points in total, and calculated as the average value of the values measured at these 36 points. .

In Table 2, the ratio of the in-plane retardation value is a value calculated as follows. First, the center point of the film width of the resin film was TD _c , and TD _c was 0%, and the in-plane retardation value of a point (2 points) 80% apart toward both ends of the film was measured. The in-plane retardation value of these two points was taken as TD ₈₀ . R (TD _C ) / R (TD ₈₀ ) represents the ratio of the in-plane retardation value of TD _c to TD ₈₀ .

Similarly, the in-plane retardation value of a point (2 points) 66% apart toward both ends of the film was measured using TD _c as 0%. The average of these two points in-plane retardation was TD ₆₆ . R (TD _C ) / R (TD ₆₆ ) represents the ratio of the in-plane retardation value of TD _c to TD ₆₆ .

(Solid content and viscosity)

The viscosity (cps) of the varnish is measured at 25 ° C using an E-type viscometer according to JIS K 8803: 2011. In addition, the resin concentration of the varnish indicates the concentration (mass%) of the resin contained in the varnish, and is calculated from the mass of the resin contained in the varnish based on the total mass of the varnish.

(Particle diameter of silica particles)

The particle size of the silica particles was calculated according to the specific surface area measured by the BET adsorption method according to JIS Z 8830. The specific surface area of the powder obtained by drying the silica sol at 300 ° C was measured using a specific surface area measuring device ("monosov (registered trademark) MS-16" manufactured by Yuasa Ionics Inc.).

(Weight average molecular weight)

Gel permeation chromatography (GPC) measurements

(1) Pretreatment method

The sample was dissolved in γ-butyrolactone (GBL) to make a 20% by mass solution, diluted 100-fold with DMF eluent, and filtered with a 0.45 μm membrane filter as a measurement solution.

(2) Measurement conditions

Column: TSKgel SuperAWM-H × 2 + SuperAW2500 × 1 (6.0mm I.D. × 150mm × 3 pieces)

Eluent: DMF (addition of 10 mmol / L lithium bromide)

Flow rate: 0.6 mL / min

Detector: RI detector

Column temperature: 40 ° C

Injection volume: 20 μL

Molecular weight standard: standard polystyrene

<Production Example 1: Preparation of polyimide resin 1)

Under a nitrogen gas atmosphere, in a 1L separable flask with a stirring vane, 2,2'-bis (trifluoromethyl) -4,4'-diaminodiphenyl (TFMB) 45 g (140.52 mmol) and N, N -768.55 g of dimethylacetamide (DMAc) was added and stirred at room temperature to dissolve TFMB in DMAc. Next, 18.92 g (42.58 mmol) of 4,4 '-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) was added to the flask and stirred at room temperature for 3 hours. Thereafter, 4.19 g (14.19 mmol) of 4,4'-oxybis (benzoylchloride) (OBBC), and then 17.29 g (85.16 mmol) of terephthaloyl chloride (TPC) were added to the flask and stirred at room temperature for 1 hour. Subsequently, 4.63 g (49.68 mmol) of 4-methylpyridine and 13.04 g (127.75 mmol) of acetic anhydride were added to the flask, stirred at room temperature for 30 minutes, heated to 70 ° C using an oil bath, and further stirred for 3.5 hours. A reaction solution was obtained.

The obtained reaction solution was cooled to room temperature, charged into a large amount of methanol in a thread form, and the precipitated precipitate was taken out, immersed in methanol for 6 hours, and then washed with methanol. Next, the precipitate was dried under reduced pressure at 100 ° C to obtain polyimide resin 1. The weight average molecular weight of the polyimide resin 1 was 455,000. The imidation ratio of the polyimide was 98.9%.

<Production Example 2: Preparation of dispersion 1>

The methanol-dispersed organic-treated silica (particle diameter measured by BET method: 27 nm) was replaced with GBL to obtain GBL-dispersed organic-treated silica (solid content: 30.3% by mass). Let this dispersion liquid be dispersion liquid 1.

<Production Example 3: Preparation of varnish 1>

Varnish 1 is the composition shown in Table 1, and the mixture of the polymer and the filler in a GBL solvent at room temperature is 60:40, Sumisorb 340 (UVA), Sumiplast Violet B (BA), and polymer and silica. With respect to the total mass, respectively, 5.7 phr or 35 ppm was added and stirred until uniform. Varnish 1 having a solid content of 10.3% by mass and a viscosity at 25 ° C of 38,500 cps was obtained.

<Production Example 4: Formation of raw film 1>

Varnish 1 is formed by flexible molding on a PET (polyethylene terephthalate) film ("Toyobo Co., Ltd." "Cosmoshine (registered trademark) A4100", thickness 188 μm, thickness distribution ± 2 μm). The coating film was molded. At this time, the ship speed was 0.3 m / min. Moreover, after heating at 80 degreeC for 10 minutes, it heated at 100 degreeC for 10 minutes, and then heated at 90 degreeC for 10 minutes, and finally, the coating film was dried on condition of heating at 80 degreeC for 10 minutes. Then, the coating film was peeled off from the PET film to obtain a raw film 1 having a thickness of 58 μm and a width of 700 mm. The raw film 1 had a weight reduction rate of 9.2%, total light transmittance of 89.5%, haze of 0.2%, and yellowness of YI of 1.5.

<Example 1>

Using a tenter dryer (1-6 rooms) equipped with a clip as a gripper and equipped with an IR heater as a radiation source, the solvent was removed from the raw film 1 obtained in Production Example 4 to obtain a resin film 1 with a thickness of 49 μm. . In the tenter-type dryer, a nozzle and an IR heater were provided in three rooms and four rooms as shown in FIG. 3. At this time, the temperature of the warm air in the drying furnace of 1 to 6 rooms was set to 200 ° C, and the IR heaters of 3 and 4 rooms were set to 230 ° C, the clip gripping width was 25 mm, the conveyance speed of the film was 1.8 m / min, and the entrance to the drying furnace The ratio of the film width (distance between clips) and the film width at the outlet of the drying furnace was 0.98. In addition, the wind speed of each room was adjusted so that 1 room was 13.5 m / s, 2 rooms were 13 m / s, and 3 to 6 rooms were 11 m / s, and NOK KLUBER (NOK KLUBER) was used as a lubricant for the rails. The heating process was performed using "Varierta J400V" manufactured by CO., LTD.). After the film fell off the clip, the clip portion was slit (cut), a PET-based surface protection film was affixed to the film, and wound into a 6-inch ABS core to obtain a roll film. Table 2 shows the optical properties (phase difference value, total light transmittance, haze, and yellowness YI) and weight loss of the resin film 1 after the tenter drying furnace.

<Example 2>

The resin film 2 was obtained by the method similar to Example 1 except having changed the conveyance speed to 2.7 m / min. Table 2 shows the film optical properties (phase difference value, total light transmittance, haze, yellowness YI) and weight reduction rate after the tenter drying furnace.

18… Gripping device, 20 ... Raw film, 30 ... Upper nozzle (nozzle), 32 ... Lower nozzle (nozzle), 35… Nozzle, 37 ... IR heater, 100… As a tenter, 100a ... Top, 100b… If you do, A ... Film conveying direction.

Claims (12)

A resin film comprising at least either a polyimide resin or a polyamide resin,
When the center point in the width direction of the film is TD _c and the length from the center point in the width direction to the end is 0% with the center point being 0% and TD ₈₀ is the length of the TD _c measured at a wavelength of 590 nm. in-plane retardation value R (TD _c) and the in-plane retardation value R of the TD ₈₀ to the resin film (TD ₈₀₎ meet the formula (1).
R (TD _c ) / R (TD ₈₀ ) ≥0.35 (1) According to claim 1,
The resin film was measured at a wavelength of 590 nm when the center point in the film width direction was TD _c , and in the length from the center point in the width direction to the end, the center point was 0% and a point of length 66% was TD ₆₆ . in-plane retardation value of R _c TD (TD _c) and the in-plane retardation value R of the TD ₆₆ to the resin film (TD ₆₆₎ meet the formula (2).
R (TD _c ) / R (TD ₆₆ ) ≥0.40 (2) According to claim 1,
The resin film is a resin film that satisfies Expression (3).
R (TD _c ) / R (TD ₆₆ ) -R (TD _c ) / R (TD ₈₀ ) <0.15 (3) According to claim 1,
The resin film is a resin film whose weight reduction rate is 3% or less. According to claim 1,
A resin film having a total width of 300 to 2,200 mm in the resin film width direction. A flexible display device comprising the resin film according to any one of claims 1 to 5. The method of claim 6,
A flexible display device further comprising a touch sensor. The method of claim 6,
A flexible display device further comprising a polarizing plate. A method for producing a resin film containing at least either a polyimide resin or a polyamide resin,
Has a heating process for heating the raw material film in a tenter furnace, which is divided into a plurality of spaces inside,
In the tenter furnace, a heating process is performed in a hot air treatment system in at least one space, and a heating process is performed in a radiation treatment system in at least one space. The method of claim 9,
The said heating process is a manufacturing method of the resin film performed by both methods of a hot air treatment system and a radiation treatment system in the same space as a tenter. The method of claim 9,
The method for producing a resin film, wherein the heating process of the radiation treatment method is performed by shooting a radiation film having a temperature of 30 ° C. or higher higher than the temperature of a space in which the heating process is performed by the radiation treatment method. The method of claim 9,
A method for producing a resin film, wherein the raw film contains a solvent, and the weight reduction rate of the raw film is 40% or less.

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