KR20210062011A - Foldable display - Google Patents

Abstract

The present invention has a polyester resin (A) as a main component, a glass transition temperature of 85°C or more and 150°C or less, and a yield point strain in at least one direction of 8.0% or more when a tensile test at 23°C is performed. It is a foldable display with a display film. According to the present invention, it is possible to provide a foldable display including a display film excellent in cutting resistance and heat resistance.

Description

Foldable display

The present invention relates to a foldable display provided with a display film excellent in heat resistance and cutting resistance.

Polyester is excellent in properties such as heat resistance, weather resistance, mechanical strength, transparency, chemical resistance, and gas barrier properties, and is highly versatile because it is easy to obtain at a price point. Currently, containers and packaging materials for beverages and foods , It is a resin that is widely used in molded products and films.

On the other hand, in recent years, while the need for a flexible display is increasing, a film having high heat resistance and excellent repetitive bending resistance is strongly demanded.

For example, in Patent Literature 1, a film having repeated bending resistance by a film made of a cyclic olefin resin is examined.

In addition, as a film excellent in heat resistance and bending resistance in Patent Documents 2 and 3, a film made of polyimide is proposed.

Japanese Unexamined Patent Application Publication No. 2014-104687 International Publication No. 2017/150377 pamphlet International Publication No. 2016/060213 pamphlet

However, the film disclosed in Patent Document 1 was low as the level of repeated bending resistance, and did not satisfy the market demand.

Moreover, since the cyclic olefin resin is poor in coatability and adhesiveness, it may be considered that lamination with other members as a member for a flexible display is difficult.

In addition, while the polyimide film described in Patent Document 2 has high heat resistance, the molding temperature is 350°C, and the molding time is also long, so there is difficulty in productivity.

Although the polyimide film described in Patent Document 3 has bending resistance, in the manufacturing process, since it is a molding method by coating using a solvent, the productivity is poor and the cost is also high.

The problem to be solved in the present invention is to solve the above problems and provide a foldable display including a display film having excellent cutting resistance and heat resistance.

The present invention includes the following aspects.

[1] The foldable display of the present invention contains a polyester resin (A) as a main component, has a glass transition temperature of 85°C or more and 150°C or less, and in at least one direction when a tensile test at 23°C is performed. It is provided with a display film having a yield point deformation of 8.0% or more.

[2] In a foldable display according to a preferred aspect, the polyester resin (A) is a terephthalic acid unit as a dicarboxylic acid component (a-1), and a 1,4-cyclone as a diol component (a-2). It is a polycyclohexylene dimethylene terephthalate containing a hexane dimethanol unit.

[3] In a foldable display according to a preferred aspect, the crystal melting temperature of the polycyclohexylenedimethylene terephthalate is 255°C or more and 310°C or less.

[4] In a foldable display according to a preferred aspect, the display film is a polyaryl ray having a higher glass transition temperature than the polyester resin (A) with respect to 100 parts by mass of the polyester resin (A). 1 part by mass or more and 50 parts by mass or less are included.

[5] In a foldable display according to a preferred aspect, the crystal melting temperature of the display film is 255°C or more and 300°C or less.

[6] In a foldable display according to a preferred aspect, the thickness of the display film is 1 to 250 µm.

[7] In a foldable display according to a preferred aspect, when a bending test of 1000 times at 23° C. is performed under the condition of a bending radius R = 1.5 mm, there is no change in appearance in the display film.

[8] The film laminate for a display of the present invention contains a polyester resin (A) as a main component, has a glass transition temperature of 85°C or more and 150°C or less, and at least one direction when a tensile test at 23°C is performed. A display film having a yield point deformation of 8.0% or more, and an adhesive layer provided on at least one side of the display film.

[9] The foldable display of the present invention has a configuration formed by bonding other members through an adhesive layer of the film laminate for a display.

The display film proposed by the present invention is excellent in cutting resistance and heat resistance, and by laminating this film with other members, a foldable display having excellent cutting resistance and heat resistance can be obtained.

Hereinafter, the present invention will be described in detail. However, the content of the present invention is not limited to the embodiments described below.

The present invention has a polyester resin (A) as a main component, a glass transition temperature of 85°C or more and 150°C or less, and a yield point strain in at least one direction of 8.0% or more when a tensile test at 23°C is performed. It is a foldable display with a display film.

In addition, the yield point deformation in at least one direction when the tensile test at 23°C is performed is also simply referred to as the yield point deformation.

Hereinafter, a display film provided in the foldable display of the present invention will be described in detail.

<Display film>

A display film (hereinafter, sometimes referred to as “this film”) according to an example of the embodiment of the present invention has a polyester resin (A) as a main component, and a glass transition temperature of 85°C or more and 150°C or less It is a film for a display having a yield point strain of 8.0% or more in at least one direction when a tensile test at 23°C is performed.

In the present invention, the "main component" refers to a component that occupies the largest mass proportion, specifically, it is 50 mass% or more, more preferably 55 mass% or more, and still more preferably 60 mass% or more.

The inventors of the present invention discovered that a polyester-based resin film having a glass transition temperature of 85°C or more and 150°C or less and a yield point deformation of a specific value or more has excellent cut resistance and heat resistance as a display film, and is particularly suitable for foldable applications. , Completed the present invention.

The inventors of the present invention believe that the present film has a relatively large amount of deformation until the start of plastic deformation, so that the cutting resistance is exhibited.

It is preferable that this film is a thin film and a biaxially stretched film from the viewpoint of imparting cutting resistance.

(1) glass transition temperature

The glass transition temperature (Tg) of this film is 85°C or more and 150°C or less, more preferably 86°C or more and 140°C or less, and still more preferably 87°C or more and 130°C or less.

When the Tg of the present film is 85° C. or higher, the film is not deformed even when the film is used for a display application, so that the heat resistance is excellent.

On the other hand, when Tg of this film is 150 degrees C or less, workability will also be suitable.

The glass transition temperature (Tg) of this film is measured at a heating rate of 10°C/min using a differential scanning calorimeter (DSC) according to JIS K7121 (2012).

In addition, when a plurality of glass transition temperatures are confirmed in DSC measurement, the glass transition temperature (Tg) in the present invention shall indicate the glass transition temperature on the high-temperature side.

(2) Yield point deformation

When the tensile test at 23°C of the present film was performed, the yield point strain in at least one direction was 8.0% or more.

The yield point deformation of the present film is preferably 8.5% or more, and more preferably 9.0% or more. The upper limit of the yield point strain is not particularly limited, but is 50% or less. When the yield point strain in at least one direction is 8.0% or more, the bending resistance of the film is maintained within the practical range.

Yield point deformation can be adjusted according to stretching conditions and the like when producing the present film.

In this film, while the yield point deformation in one direction is within the above range, the yield point deformation in a direction orthogonal to one direction is preferably 8.0% or more, more preferably 8.5% or more, and still more preferably 9.0% or more. And it is preferably 50% or less.

In addition, the said ``one direction'' is not particularly limited, but, for example, means the MD (or TD) of the present film, and the ``direction orthogonal to one direction'' means, for example, the TD (or MD) of the present film. do. Here, MD means "Machine Direction", and TD means "Transverse Direction".

The yield point strain of this film means the strain (%) at the yield point of a stress-strain curve obtained in a tensile test, and can be measured by a method according to JIS K 7127:1999.

(3) yield stress

The yield stress of the present film when the tensile test at 23°C is performed is preferably 50 MPa or more, more preferably 55% or more, and still more preferably 60 MPa or more.

Although the upper limit is not particularly limited, in the case of a film made of a polyester resin, it is usually 300 MPa or less.

By setting the yield stress of this film to 50 MPa or more, the film strength is maintained within the practical range, and the bending resistance of the film is maintained within the practical range. The yield stress can be adjusted according to the stretching conditions.

The yield stress of this film can be measured by a method according to JIS K 7127:1999.

(4) crystal melting temperature

It is preferable that the crystal melting temperature (Tm) of the present film is 255°C or more and 300°C or less.

In particular, it is more preferably 256°C or more and 295°C or less, more preferably 257°C or more and 290°C or less, and particularly preferably 258°C or more and 285°C or less.

When the crystal melting temperature (Tm) of the present film is within such a range, the present film is excellent in balance between heat resistance and melt moldability.

Here, the crystal melting temperature (Tm) is measured at a heating rate of 10°C/min using a differential scanning calorimeter (DSC) for this film according to JIS K7121 (2012).

In addition, the crystal melting temperature (Tm) means the crystal melting peak temperature.

In DSC measurement, when a plurality of crystal melting temperatures are confirmed, the crystal melting temperature (Tm) in the present invention shall indicate the highest crystal melting temperature.

The crystal melting temperature (Tm) of the present film is determined by selecting a resin material constituting the present film, adding a crystal nucleating agent, or in the production of the present film, the cooling temperature from the molten state, the stretching ratio, the stretching temperature, and after stretching. It can be optimized by adjusting the heat treatment conditions.

(5) thickness

It is preferable that it is 1 to 250 micrometers, and, as for the thickness of this film, it is more preferable that it is 5 to 200 micrometers. By setting it as 1 micrometer or more, the film strength is maintained within a practical range.

When it is 250 micrometers or less, it becomes easy to express the cutting resistance.

The thickness can be adjusted according to the stretching conditions.

(6) heat resistance

This film has no change in appearance when performing 1000 bending tests at 23°C under conditions of a bending radius (R) = 1.5 mm using a YUASA bending test apparatus (DLDMLH-FS-C). It is preferable to be.

By satisfying this, it can be said that this film is excellent in cutting resistance.

The present invention has been achieved by the inventors of the present invention, finding that a film mainly composed of a polyester-based resin exhibiting a relatively higher yield stress than a polyethylene-based resin or a polypropylene-based resin has excellent bending resistance.

Even with a polyester resin having a high yield stress, when the stress applied by the deformation is large, there is a problem that deformation occurs, and deformation that is not resolved in the material remains.

However, in the present invention, the inventors have found that deformation is less likely to occur if the yield point deformation is more than a specific value.

It is considered that in the case of being distorted beyond the elastic deformation region (yield point), deformation traces such as bent traces and wrinkles remain, resulting in an influence on appearance defects and material properties themselves.

That is, the larger the amount of deformation at the yield point is, the greater the amount of deformation until the start of plastic deformation is increased. Therefore, even when a large amount of deformation is applied, deformation marks are less likely to occur, and deformation resistance is considered to be excellent.

In the present invention, the present film may contain a resin other than the polyester resin (A) within a range that does not impair the effect of the present invention.

Other resins include, for example, polystyrene resins, polyvinyl chloride resins, polyvinylidene chloride resins, chlorinated polyethylene resins, polycarbonate resins, polyamide resins (including aramid resins), and polyacetal resins. Resin, acrylic resin, ethylene-vinyl acetate copolymer, polymethylpentene resin, polyvinyl alcohol resin, cyclic olefin resin, polyacrylonitrile resin, polyethylene oxide resin, cellulose resin, polyimide resin, Polyurethane resin, polyphenylene sulfide resin, polyphenylene ether resin, polyvinyl acetal resin, polybutadiene resin, polybutene resin, polyamideimide resin, polyamide bismaleimide resin, polyether Mid-based resins, polyetheretherketone-based resins, polyetherketone-based resins, polyethersulfone-based resins, polyketone-based resins, polysulfone-based resins, and fluorine-based resins.

In addition, the present film may appropriately contain additives generally blended within a range that does not significantly impair the effects of the present invention in addition to the above-described components.

Examples of the additives include recycling resins generated from trimming losses such as edges, etc., added for the purpose of improving and adjusting molding processability, productivity, and film properties, and silica, talc, kaolin, calcium carbonate, etc. Inorganic particles, pigments such as titanium oxide, carbon black, coloring agents such as dyes, flame retardants, weather-resistant stabilizers, heat-resistant stabilizers, antistatic agents, melt viscosity improvers, crosslinking agents, lubricants, nucleating agents, plasticizers, anti-aging agents, antioxidants, Light stabilizers, ultraviolet absorbers, neutralizing agents, antifogging agents, anti-blocking agents, and slip agents.

In addition, the present film may have a coating layer within a range not significantly impairing the effects of the present invention in addition to the additives described above.

Examples of the function of the coating layer include hard coat properties, antistatic properties, peel properties, easy adhesion properties, printability, UV cut properties, infrared barrier properties, gas barrier properties, and the like.

Regarding the formation of the coating layer, it may be provided by in-line coating that treats the film surface during the stretching process, or off-line coating applied outside the system on the once produced film, or both may be used in combination. do.

Hereinafter, the polyester resin (A) constituting the present film will be described.

<Polyester resin (A)>

The polyester resin (A) constituting this film may be homopolyester or copolyester.

In the case of homopolyester, it is preferably obtained by polycondensing an aromatic dicarboxylic acid and an aliphatic glycol.

Examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of the aliphatic glycol include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol.

As a typical polyester, polyethylene terephthalate (PET), etc. are illustrated.

On the other hand, as the dicarboxylic acid component of the copolymerized polyester, one or two or more of isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, sebacic acid, and oxycarboxylic acid can be mentioned, and as a glycol component , Ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, and the like, one or two or more.

Further, as the copolymerization component, oxycarboxylic acids such as P-oxybenzoic acid may be used.

In the present invention, from the viewpoint of glass transition temperature and yield point modification, the polyester resin (A) is a terephthalic acid unit as the dicarboxylic acid component (a-1) and 1,4-cyclo as the diol component (a-2). It is preferably a polycyclohexylenedimethylene terephthalate containing a hexanedimethanol unit.

The amount of heat of crystal melting (ΔHm(A)) of the polyester resin (A) is preferably 35 J/g or more and 70 J/g or less, and more preferably 36 J/g or more or 65 J/g or less. When ΔHm(A) is in such a range, the polyester resin (A) has suitable crystallinity, which is also excellent in heat resistance, moist heat resistance, melt moldability and stretch processability.

The heat of crystal melting (ΔHm(A)) of the polyester resin (A) can be measured at a heating rate of 10°C/min using a differential scanning calorimeter (DSC) according to JIS K7122 (2012).

In addition, the amount of heat of crystal melting (ΔHm(A)) of the polyester resin (A) is an acid component other than terephthalic acid and/ Alternatively, it can be adjusted within the above range by adjusting the type or compounding ratio of the diol component other than the 1,4-cyclohexanedimethanol unit.

The crystal melting temperature (Tm(A)) of the polyester resin (A) is preferably 255°C or more and 310°C or less, more preferably 280°C or more and 310°C or less, and more preferably 260°C or more or 340°C or less. And, it is more preferably 270°C or more or 330°C or less, and particularly preferably 280°C or more or 310°C or less.

When the crystal melting temperature (Tm(A)) of the polyester resin (A) is within such a range, the polyester resin (A) is excellent in balance between heat resistance and melt moldability.

The crystal melting temperature (Tm(A)) of the polyester resin (A) can be measured at a heating rate of 10°C/min using a differential scanning calorimeter (DSC) according to JIS K7121 (2012).

The crystal melting temperature (Tm(A)) of the polyester resin (A) is an acid other than terephthalic acid if it is a constituent unit of the (A), for example, polycyclohexylenedimethylene terephthalate, as in the above ΔHm. It can be adjusted within the above range by adjusting the type or compounding ratio of the component and/or the diol component other than the 1,4-cyclohexanedimethanol unit.

The glass transition temperature (Tg(A)) of the polyester resin (A) is more preferably 60°C or more and 150°C or less, and still more preferably 70°C or more or 120°C or less.

When the glass transition temperature (Tg(A)) of the polyester resin (A) is in such a range, the balance of heat resistance and melt moldability is excellent.

The glass transition temperature (Tg) is measured at a heating rate of 10°C/min using a differential scanning calorimeter (DSC) according to JIS K7121 (2012).

In addition, the crystal melting heat amount (ΔHm(A)), crystal melting temperature (Tm(A)), and glass transition temperature (Tg(A)) of the polyester resin (A) are all It is applied not only as a characteristic of a raw material, but also as a characteristic of the polyester-based resin (A) component constituting the present film.

The polycyclohexylenedimethylene terephthalate is a polymer containing a terephthalic acid unit as a dicarboxylic acid component (a-1) and a 1,4-cyclohexanedimethanol unit as a diol component (a-2).

In particular, when used in the present invention, polycyclohexylenedimethylene terephthalate contains 90 mol% or more of terephthalic acid units as the dicarboxylic acid component (a-1), and 1,4-cyclohexane as the diol component (a-2). It is preferable that it is a polymer containing 90 mol% or more of dimethanol units.

It is preferable that the dicarboxylic acid component (a-1) constituting the polycyclohexylenedimethylene terephthalate contains 90 mol% or more of terephthalic acid.

Of the dicarboxylic acid component (a-1), terephthalic acid is more preferably 92 mol% or more, more preferably 94 mol% or more, particularly preferably 96 mol% or more, particularly preferably 98 mol% or more, and It is most preferable that all (100 mol%) of the rbonic acid component (a-1) is terephthalic acid.

When terephthalic acid is 90 mol% or more as the dicarboxylic acid component (a-1), the glass transition temperature, melting point and crystallinity of polycyclohexylenedimethylene terephthalate are improved, and further, the heat resistance of the present film is improved.

The polycyclohexylenedimethylene terephthalate may be copolymerized with less than 10 mol% of an acid component other than terephthalic acid for the purpose of improving moldability and heat resistance.

As an acid component other than terephthalic acid, specifically, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,5-furandicar This acid, 2,4-furandicarboxylic acid, 3,4-furandicarboxylic acid, benzophenone dicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 3,3'-diphenyldicarboxylic acid, 4, Aromatic dicarboxylic acids such as 4'-diphenyl ether dicarboxylic acid; Aliphatic dicarboxylic acids such as cyclohexanedicarboxylic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid. Isophthalic acid, 2,5-furandicarboxylic acid, 2,4-furandicarboxylic acid, and 3,4-furandicarboxylic acid are preferable.

The diol component (a-2) constituting the polycyclohexylenedimethylene terephthalate preferably contains 90 mol% or more of 1,4-cyclohexanedimethanol.

In the diol component (a-2), 1,4-cyclohexanedimethanol is more preferably 92 mol% or more, more preferably 94 mol% or more, particularly preferably 96 mol% or more, and 98 mol% or more It is particularly preferred, and it is most preferred that all (100 mol%) of the diol component (a-2) is 1,4-cyclohexanedimethanol.

By using 90 mol% or more of 1,4-cyclohexanedimethanol as the diol component (a-2), the melting point and crystallinity of polycyclohexylenedimethylene terephthalate are improved, and the heat resistance of the film is further improved .

The polycyclohexylenedimethylene terephthalate may be copolymerized with less than 10 mol% of diol components other than 1,4-cyclohexanedimethanol for the purpose of improving moldability and heat resistance.

As a diol component other than 1,4-cyclohexanedimethanol, specifically, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexane Diol, neopentyl glycol, ethylene glycol, diethylene glycol, triethylene glycol, polyalkylene glycol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, hydroquinone, bisphenol, spiroglycol, 2,2 ,4,4,-tetramethylcyclobutane-1,3-diol, isosorbide, etc. are mentioned. Among these, from the viewpoint of moldability, ethylene glycol, diethylene glycol, 1,3-propanediol, 1,4- Butanediol and 1,3-cyclohexanedimethanol are preferred.

<Production method of this film>

Although a method of manufacturing a display film of the present invention is described, the following description is an example of a method of manufacturing the present film, and the present film is not limited to a film manufactured by such a manufacturing method.

The production method of the present film according to an example of the embodiment of the present invention is a production method in which a resin composition containing the polyester resin (A) as a main component is molded into a film shape and biaxially stretched.

The method of obtaining the resin composition by kneading the polyester resin (A), other resins and additives is not particularly limited, but in order to obtain the resin composition as easily as possible, it is preferably produced by melt-kneading using an extruder.

In order to uniformly mix the raw materials constituting the resin composition, it is preferable to melt kneading using a co-directional twin screw extruder.

The kneading temperature is required to be equal to or higher than the glass transition temperature of all the resins to be used, and to be equal to or higher than the crystal melting temperature of the crystalline resin.

With respect to the glass transition temperature or crystal melting temperature of the resin to be used, the higher the kneading temperature is, the easier the transesterification reaction of a part of the resin occurs, and the compatibility tends to be improved, but the kneading temperature is higher than necessary. It is not preferable because the decomposition of the ground resin occurs.

From this point of view, the kneading temperature is from 260°C to 350°C, preferably from 270°C to 340°C, more preferably from 280°C to 330°C, and particularly preferably from 290°C to 320°C.

When the kneading temperature is in such a range, the compatibility and melt moldability can be improved without causing decomposition of the resin.

The resin composition may be cooled and solidified once to obtain a shape such as a pellet shape, and then heated and melted again to be subjected to molding, or the resin composition obtained in a molten state may be molded as it is.

The resin composition obtained as described above can be molded by a general molding method such as extrusion molding, injection molding, blow molding, vacuum molding, pressure hole molding, press molding, or the like, to produce a biaxially stretched film. In each molding method, the apparatus and processing conditions are not particularly limited.

It is preferable to manufacture this film by the following method, for example.

From the resin composition obtained by mixing, a film that is substantially amorphous and not oriented (hereinafter sometimes referred to as "unstretched film") is produced by an extrusion method.

In the production of this unstretched film, for example, the raw material is melted by an extruder, extruded from a flat die or an annular die, and then rapidly cooled to obtain a flat or annular (cylindrical) unstretched film. Can be adopted.

In this case, depending on the case, it may be a laminated configuration using a plurality of extruders.

Next, from the viewpoint of stretching effect, film strength, etc., the unstretched film is usually 1.1 to 5.0 times, preferably, in at least one direction of the flow direction (longitudinal direction) of the film and a direction perpendicular thereto (transverse direction). It is stretched in the range of 1.1 to 5.0 times each in the longitudinal and horizontal biaxial directions.

As a method of biaxial stretching, any of conventionally known stretching methods such as tenter-type sequential biaxial stretching, tenter-type simultaneous biaxial stretching, and tubular simultaneous biaxial stretching can be employed.

For example, in the case of the tenter-type sequential biaxial stretching method, the glass transition temperature of the resin composition is Tg, the unstretched film is heated to a temperature range of Tg to Tg+50°C, It can be produced by stretching 1.1 to 5.0 times in the direction, and then stretching 1.1 to 5.0 times in the transverse direction within a temperature range of Tg to Tg + 50°C with a tenter type transverse stretching machine.

In the case of a tenter-type simultaneous biaxial stretching or a tubular simultaneous biaxial stretching method, for example, in a temperature range of Tg to Tg+50°C, it can be produced by stretching 1.1 to 5.0 times in each axis direction at the same time vertically and horizontally. I can.

The biaxially stretched film stretched by the said method is heat-set continuously.

By performing heat setting, dimensional stability at room temperature can be imparted.

The treatment temperature in this case is preferably a range of Tm-50 to Tm-1°C when the crystal melting temperature of the resin composition is Tm.

When the heat setting temperature is within the above range, heat setting is sufficiently performed, stress at the time of stretching is relieved, sufficient heat resistance and mechanical properties are obtained, and an excellent film without troubles such as fracture or whitening of the film surface can be obtained.

In the present invention, in order to relieve the stress of crystallization shrinkage due to heat fixation, by performing relaxation in the width direction in the range of 0 to 15%, preferably 3 to 10% during heat fixation, relaxation is sufficiently performed, and the film It relaxes uniformly in the width direction of, and the shrinkage ratio in the width direction becomes uniform, and a film excellent in room temperature dimensional stability is obtained.

Moreover, since relaxation following the shrinkage of the film is performed, there is no sagging of the film, no fluttering in the tenter, and no breakage of the film.

<Polyarylate (B)>

An example of another embodiment of this film is 1 part by mass or more of polyarylate (B) having a higher glass transition temperature than that of the polyester-based resin (A) per 100 parts by mass of the polyester-based resin (A). It is a film for display containing less than a mass part.

The difference in the glass transition temperature between the polyester resin (A) and the polyarylate (B) is preferably 60°C or higher, more preferably 70°C or higher, more preferably 80°C or higher, and particularly preferably 90°C or higher. , It is particularly preferably 100°C or higher.

The glass transition temperature of the polyarylate (B) is preferably 150°C or more and 350°C or less, more preferably 160°C or more or 340°C or less, more preferably 170°C or more or 330°C or less, and 180°C or more or 320 It is particularly preferable that it is equal to or lower than C, and particularly preferably equal to or higher than 190°C or equal to or lower than 300°C.

When the difference in the glass transition temperature between the polyester resin (A) and the polyarylate (B) satisfies the above, the glass transition temperature of the present film is improved, and the present film having excellent melt moldability is obtained.

The content ratio of the polyarylate (B) is 1 part by mass or more and 50 parts by mass or less, preferably 3 parts by mass or more or 49 parts by mass or less, and 5 parts by mass or more, based on 100 parts by mass of the polyester resin (A). Or it is more preferable that it is 47 mass parts or less, and it is more preferable that it is 10 mass parts or more or 45 mass parts or less.

When the ratio of the polyarylate (B) is 1 part by mass or more, since the crystallization rate can be slowed, the stretching processability when stretching the film can be improved.

On the other hand, when the ratio of the polyarylate (B) is 50 parts by mass or less, the crystallinity of the film is maintained, and further, the resulting film is sufficiently resistant to shrinkage during heating.

In general, improvement of the heat resistance of the resin composition can be achieved by improving the glass transition temperature (Tg).

Here, by mixing the polyarylate (B) having a higher Tg than the polyester resin (A), a resin composition having a higher glass transition temperature than that of the polyester resin (A) alone is obtained, and heat resistance and moisture resistance A film having excellent heat properties can be obtained.

On the other hand, when crystallization occurs remarkably during stretching, there is a problem that fracture from the crystal part during stretching is liable to occur.

Therefore, as described later, by adding amorphous polyarylate (B), the crystallinity of the polyester resin (A) itself is relaxed, fracture during stretching is suppressed, and handling properties during processing can be improved. .

As described above, the present film may contain a polyarylate (B) having a higher glass transition temperature measured according to JIS K7198A than the polyester resin (A).

Polyarylate (B) is a polycondensate of a dicarboxylic acid component (b-1) and a dihydric phenol component (b-2).

The glass transition temperature of the polyarylate (B) can be adjusted by appropriately selecting the dicarboxylic acid component (b-1) and the dihydric phenol component (b-2), and in particular, the dihydric phenol component is appropriately selected. It is desirable.

The dicarboxylic acid component (b-1) constituting the polyarylate (B) is not particularly limited as long as it is a divalent aromatic carboxylic acid, but among them, it is preferably a mixture of a terephthalic acid component and an isophthalic acid component.

The mixing ratio (mol%) of the terephthalic acid component and the isophthalic acid component is preferably terephthalic acid/isophthalic acid = 99/1 to 1/99, more preferably 90/10 to 10/90, and 80/20 to 20/80 This is more preferable, 70/30 to 30/70 is particularly preferable, and 60/40 to 40/60 is particularly preferable.

When the mixing ratio of terephthalic acid and isophthalic acid as the dicarboxylic acid component (b-1) is within the above range, the polyarylate (B) is excellent in heat resistance and melt moldability.

The polyarylate (B) may copolymerize an acid component other than terephthalic acid and isophthalic acid as a dicarboxylic acid component.

Specifically, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, benzophenone dicarboxylic acid, 4,4'-diphenyldicarboxylic acid, Aromatic dicarboxylic acids such as 3,3'-diphenyldicarboxylic acid and 4,4'-diphenyletherdicarboxylic acid, cyclohexanedicarboxylic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid And aliphatic dicarboxylic acids such as pimelic acid, suberic acid, azelaic acid, and sebacic acid. In order not to impair the heat resistance of the polyarylate resin (B), the copolymerization ratio of terephthalic acid and acid components other than isophthalic acid is preferably less than 10 mol%.

The dihydric phenol component (b-2) constituting the polyarylate (B) is not particularly limited as long as it is a divalent phenol, but bisphenol A component and bisphenol TMC (1,1-bis(4-hydroxyphenyl)- 3,3,5-trimethylcyclohexane) component, or it is preferable to contain both bisphenol A and bisphenol TMC.

In general, it becomes a polyarylate excellent in melt moldability (flowability) by including the bisphenol A component.

On the other hand, by including the bisphenol TMC component, the glass transition temperature is improved to obtain a polyarylate (B) excellent in heat resistance.

When it is desired to balance melt moldability and heat resistance, both the bisphenol A component and the bisphenol TMC component are used.

In this case, the ratio (mol%) of the bisphenol A component and the bisphenol TMC component is preferably bisphenol A/bisphenol TMC=99/1 to 1/99, more preferably 90/10 to 10/90, and 80/20 -20/80 are more preferable, 70/30-30/70 are especially preferable, and 60/40-40/60 are especially preferable.

When the ratio of the bisphenol A component and the bisphenol TMC component is in such a range, a polyarylate (B) excellent in balance of heat resistance and melt moldability is obtained.

The polyarylate (B) is a dihydric phenol component (b-2), bisphenol A (2,2-bis (4-hydroxyphenyl) propane) and bisphenol TMC (1,1-bis (4-hydroxy You may copolymerize bisphenol components other than phenyl)-3,3,5-trimethylcyclohexane).

Specifically, bisphenol AP (1,1-bis (4-hydroxyphenyl) -1-phenylethane), bisphenol AF (2,2-bis (4-hydroxyphenyl) hexafluoropropane), bisphenol B ( 2,2-bis(4-hydroxyphenyl)butane), bisphenol BP (bis(4-hydroxyphenyl)diphenylmethane), bisphenol C(2,2-bis(3-methyl-4-hydroxyphenyl)) Propane), bisphenol E (1,1-bis (4-hydroxyphenyl) ethane), bisphenol F (bis (4-hydroxyphenyl) methane), bisphenol G (2,2-bis (4-hydroxy-3) -Isopropylphenyl)propane), bisphenol M(1,3-bis(2-(4-hydroxyphenyl)-2-propyl)benzene), bisphenol S(bis(4-hydroxyphenyl)sulfone), bisphenol P (1,4-bis(2-(4-hydroxyphenyl)-2-propyl)benzene), bisphenol PH(5,5'-(1-methylethylidene)-bis[1,1'-(bis Phenyl)-2-ol]propane), bisphenol Z(1,1-bis(4-hydroxyphenyl)cyclohexane), and the like.

In order not to impair the heat resistance of the polyarylate (B), the copolymerization ratio of the compound is preferably less than 10 mol%.

Polyarylate (B) is a mixture of a terephthalic acid component and an isophthalic acid component as a dicarboxylic acid component (b-1) in order to increase compatibility with polycyclohexylenedimethylene terephthalate, and a dihydric phenol component (b). As -2), it is preferable to select any of the bisphenol A component and the bisphenol TMC component, or a mixture of bisphenol A and bisphenol TMC.

As the polyarylate (B), a mixture of polycarbonate may be used in order to improve melt moldability.

Since polyarylate (B) and polycarbonate are compatible, by mixing polycarbonate with polyarylate (B), the glass transition temperature of polyarylate (B) can be lowered while maintaining transparency and mechanical properties. As a result, it is possible to improve the melt moldability.

When mixing polyarylate (B) and polycarbonate, the mixing ratio (mass%) is preferably polyarylate (B)/polycarbonate = 99/1 to 50/50, and 98/2 = 60/ 40 is more preferable, 97/3 to 70/30 are more preferable, and 96/5 to 80/20 are particularly preferable.

If the mixing ratio of the polyarylate (B) and the polycarbonate is within such a range, the melt moldability can be improved while maintaining the heat resistance of the polyarylate (B).

In addition, in the mixing of polyarylate (B) and polycarbonate, it is preferable to use a mixture of these two components as a raw material, but is not limited to this method, and polycarbonate is selected as the ``other resin'', By using it as an independent raw material, it is good also as the said structure.

Among the combinations of the polyester resin (A) and the polyarylate (B) described above, a combination of polycyclohexylenedimethylene terephthalate and polyarylate is particularly preferred from the viewpoint of compatibility.

In addition, when polycyclohexylenedimethylene terephthalate (A) and polyarylate (B) are melt-mixed, a part of each of polycyclohexylenedimethylene terephthalate (A) and polyarylate (B) is transesterified. By doing so, since the interfacial tension between the two polymers is significantly lowered, it can be considered to be compatible with each other and to obtain a resin composition having very excellent transparency and heat resistance.

Therefore, polycyclohexylenedimethylene terephthalate also includes a transesterification product obtained by transesterification reaction of part or all of the polycyclohexylenedimethylene terephthalate, and in the polyarylate, part or all of the polyarylate is ester It also includes a transesterification product obtained by exchange.

The degree of transesterification (reaction rate) can be adjusted according to melt-mixing conditions such as mixing temperature, shear rate, and residence time, and thereby the amount of heat of crystal melting (ΔHm) of the present film can be adjusted.

<Foldable display>

Since the film for displays in the present invention is excellent in cutting resistance and heat resistance, and also excellent in transparency, a foldable display provided with this film is excellent in cutting resistance and heat resistance.

The above-described display film (this film) in the present invention is used as a constituent member for a display, such as a front plate, a base film for a touch sensor, a lower protective film, etc., and other members via an adhesive layer. It is preferable to be laminated with.

More specifically, it is preferable to use the display film and a display film laminate having an adhesive layer provided on at least one side of the display film, and other It is preferable to use a foldable display having a configuration formed by bonding members.

As the pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer, an acrylic pressure-sensitive adhesive, a rubber-based pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, a polyester-based pressure-sensitive adhesive, a vinyl alkyl ether-based pressure-sensitive adhesive, and an epoxy pressure-sensitive adhesive may be used.

The pressure-sensitive adhesives forming the pressure-sensitive adhesive layer are used alone or in combination of two or more.

Examples of the other member include various electronic devices having a display such as a mobile phone, a smart phone, a digital camera, and a personal computer.

Specifically, the film laminate for displays is used by bonding to a display of such an electronic device via an adhesive layer.

The type of display is not particularly limited, and may be a liquid crystal display, a plasma display, an organic EL display, or the like, or a touch panel type display.

[Example]

Although examples are shown below, the present invention is not limited at all by these.

(1) glass transition temperature

With respect to the obtained film, using Diamond DSC (manufactured by Perkin Elmer Japan), in accordance with JIS K7121 (2012), the temperature was raised to the melting temperature once at a heating rate of 10°C/min, and then the temperature was lowered at a temperature decrease rate of 10°C/min, The glass transition temperature in the process of increasing the temperature at a heating rate of 10°C/min was measured.

(2) crystal melting temperature

About the obtained film, using Diamond DSC (manufactured by Perkin Elmer Japan), in accordance with JIS K7121 (2012), the crystal melting temperature in the heating process at a heating rate of 10°C/min was measured.

(3) Formability

Regarding the cast film, when biaxially stretching was performed, what was stretched without breaking was set as pass ((circle)), and the one in which breakage occurred was set as reject (x).

(4) Yield point deformation

As the measuring device, a tensile tester (tensile tester AG-1kNXplus manufactured by Shimadzu Corporation) was used. The test piece was cut out from this film into a rectangle having a length of 100 mm and a width of 15 mm in the measurement direction. Both ends of the test piece in the longitudinal direction were chucked with a chuck distance of 40 mm, pulled at a crosshead speed of 200 mm/min, and the strain at the yield point was measured three times as yield strain, and the average value was calculated. The tensile test performed both the MD tensile test and the TD tensile test of the film.

(5) heat resistance

(Bending evaluation)

About the obtained film, the bending test of 1000 times at 23 degreeC was performed using the bending test apparatus (DLDMLH-FS-C) made by YUASA under the conditions of bending radius (R) = 2 mm, 1.5 mm, and 1 mm. . It was indicated as ○ for no change in appearance, △ for a slightly bending trace, and × for a clear bending trace.

(Comprehensive evaluation)

It evaluated as follows from the result of a bending test.

○: There is no change in appearance in the evaluation of R=2mm and 1.5mm, so there is practicality

×: There is a change in appearance in at least one evaluation among R=2mm and 1.5mm, and practicality is low

[Polyester resin (A)]

(A)-1: SKYPURA0502HC

(Manufactured by SK Chemicals, dicarboxylic acid component: terephthalic acid = 100 mol%, diol component: 1,4-cyclohexanedimethanol = 100 mol%, Tm = 293°C, ΔHm = 48J/g, Tg = 110°C)

(A)-2: SKYPURA0502

(Manufactured by SK Chemicals, dicarboxylic acid component: terephthalic acid = 100 mol%, diol component: 1,4-cyclohexanedimethanol = 100 mol%, Tm = 286°C, ΔHm = 42J/g, Tg = 104°C)

(A)-3: SKYPURA1631

(Manufactured by SK Chemicals, dicarboxylic acid component: terephthalic acid = 91.8 mol%, isophthalic acid = 8.2 mol%, diol component: 1,4-cyclohexanedimethanol = 100 mol%, Tm = 274°C, ΔHm = 32J/g, Tg=101℃)

[Polyarylate (B)]

(B)-1: U polymer (registered trademark) U-100

(Manufactured by Unityca, dicarboxylic acid component: terephthalic acid/isophthalic acid = 50/50 mol%, bisphenol component: bisphenol A = 100 mol%, Tg(B) = 210°C)

[Biaxially oriented PET film (C)]

(C)-1: Biaxially stretched PET film with a thickness of 50 μm

[PEN film (D)]

(D)-1: 50㎛-thick PEN film (Theonex Q51)

(Example 1)

The pellet-shaped (A)-1 was added in a ratio of 30% by mass to 70% by mass, and the pellet-shaped (B)-1 was added in a ratio of 30% by mass ((A)-1 was added to 100 parts by weight, (B)-1 43 parts by mass of this), after dry blending, a co-directional twin-screw extruder set to 310°C (manufactured by Toshiba Machinery Co., Ltd., diameter 40 mm, the ratio of the effective length (L) and outer diameter (D) of the screw (L/D) =32), the obtained strand was cooled and solidified in a water bath, cut with a pelletizer, and a pellet was produced.

The produced pellet was melt-kneaded at 310°C using a single screw extruder (manufactured by Mitsubishi Heavy Industries, Ltd.), and then a molten resin sheet extruded from a T-die with a gap of 1.0 mm and 310°C was taken over with a cast roll at 115°C, and cooled. It solidified to obtain a film-like article having a thickness of about 500 µm.

Subsequently, the obtained cast film was passed through a longitudinal stretching machine, and stretching was performed three times in the longitudinal direction (MD) at 125°C.

Subsequently, the obtained vertically stretched film was passed through a transverse stretching machine (tenter), stretched 3.5 times in the transverse direction (TD) at a preheating temperature of 130°C, a stretching temperature of 130°C, and a heat setting temperature of 260°C, and then in a tenter. A 10% relaxation treatment was performed on the film. About the obtained film, the evaluation of said (1)-(5) was performed. Table 1 shows the results.

(Example 2)

About the polyester resin (A), preparation and evaluation of a sample were performed by the method similar to Example 1 except having used (A)-2 instead of (A)-1. Table 1 shows the results.

(Example 3)

About the polyester resin (A), preparation and evaluation of a sample were performed by the method similar to Example 1 except having used (A)-3 instead of (A)-1. Table 1 shows the results.

(Comparative Example 1)

Table 1 shows the results of evaluation of the biaxially stretched PET film (C)-1.

(Comparative Example 2)

Table 1 shows the results of evaluation of the PEN film (D)-1.

In Examples 1 to 3, a film could be produced without any particular problem at the time of molding. The films of Examples 1 to 3 have high crystal melting temperature and glass transition temperature, and are also excellent in heat resistance. The films of Examples 1 to 3 had a clear difference in superiority and inferiority to Comparative Examples 1 and 2 in the evaluation in R=1 and 1.5. Therefore, the films of Examples 1 to 3 are excellent in cutting resistance.

Claims (9)

A display film having a polyester resin (A) as a main component, a glass transition temperature of 85°C or more and 150°C or less, and a yield point strain of 8.0% or more in at least one direction when a tensile test at 23°C is performed. Equipped foldable display. The method of claim 1,
The polyester resin (A) is a polycyclohexylenedimethylene tere containing a terephthalic acid unit as a dicarboxylic acid component (a-1) and a 1,4-cyclohexanedimethanol unit as a diol component (a-2) Phthalate, foldable display. The method of claim 2,
A foldable display wherein the crystal melting temperature of the polycyclohexylenedimethylene terephthalate is 255°C or more and 310°C or less. The method according to any one of claims 1 to 3,
The display film contains 1 part by mass or more and 50 parts by mass or less of a polyarylate (B) having a higher glass transition temperature than the polyester-based resin (A) per 100 parts by mass of the polyester-based resin (A). That, foldable display. The method according to any one of claims 1 to 4,
The display film is a foldable display having a crystal melting temperature of 255° C. or more and 300° C. or less. The method according to any one of claims 1 to 5,
The display film has a thickness of 1 to 250 μm, a foldable display. The method according to any one of claims 1 to 6,
The display film is a foldable display with no change in appearance when a bending test of 1000 times at 23°C is performed under the condition of a bending radius (R) = 1.5 mm. A display film containing a polyester resin (A) as a main component, a glass transition temperature of 85°C or more and 150°C or less, and a yield point strain of 8.0% or more in at least one direction when a tensile test at 23°C is performed; and , A display film laminate provided with an adhesive layer provided on at least one side of the display film. A foldable display having a configuration formed by bonding other members via an adhesive layer of the display film laminate according to claim 8.