WO2020059813A1 - Foldable display - Google Patents

Abstract

The present invention is a foldable display with a display film which contains a polyester resin (A) as a primary component and which has a glass transition temperature of 85 to 150°C and a yield point strain of 8.0% or greater in at least one direction when tensile testing is performed at 23°C. The present invention can provide a foldable display with a display film that has excellent folding endurance and heat resistance.

Description

Foldable display

(4) The present invention relates to a folderable display provided with a display film having excellent heat resistance and folding resistance.

Polyester is excellent in properties such as heat resistance, weather resistance, mechanical strength, transparency, chemical resistance, and gas barrier properties, and is easily available in terms of price. It is a resin widely used in food containers, packaging materials, molded products, films and the like.

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

For example, Patent Literature 1 discusses a film that is made of a cyclic olefin resin and has a resistance to repeated bending.

特許 Also, Patent Documents 2 and 3 propose a film made of polyimide as a film having excellent heat resistance and bending resistance.

JP 2014-104687 A WO 2017/150377 pamphlet WO 2016/060213 pamphlet

However, the film disclosed in Patent Literature 1 has a low level of repeated bending resistance and does not satisfy the requirements of the market.
Further, since the cyclic olefin-based resin has poor coating properties and adhesiveness, it is considered that lamination with other members as a flexible display member is difficult.

ポ リ イ ミ ド Although the polyimide film described in Patent Document 2 has high heat resistance, the molding temperature is 350 ° C. and the molding time is long, so that the productivity is difficult.

ポ リ イ ミ ド Although the polyimide film described in Patent Literature 3 has bending resistance, its manufacturing process is a molding method by application using a solvent, so that productivity is poor and costs are high.

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

The present invention includes the following aspects.

[1] The folderable 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 yields in at least one direction when subjected to a tensile test at 23 ° C. It has a display film having a point strain of 8.0% or more.
[2] In the folderable display according to a preferred embodiment, the polyester resin (A) is a terephthalic acid unit as the dicarboxylic acid component (a-1) and 1,4-cyclohexanedimethanol as the diol component (a-2). Polycyclohexylene dimethylene terephthalate containing units.
[3] In the folderable display according to a preferred embodiment, the polycyclohexylene dimethylene terephthalate has a crystal melting temperature of 255 ° C. or more and 310 ° C. or less.
[4] The folderable display according to a preferred embodiment, wherein the display film is a polyarylate having a higher glass transition temperature than the polyester-based resin (A) with respect to 100 parts by mass of the polyester-based resin (A). B) in an amount of 1 part by mass to 50 parts by mass.
[5] In the folderable display according to a preferred embodiment, the crystal melting temperature of the display film is 255 ° C. or more and 300 ° C. or less.
[6] In a folderable display according to a preferred embodiment, the display film has a thickness of 1 to 250 μm.
[7] In the foldable display according to a preferred embodiment, when the bending test is performed 1000 times at 23 ° C. under the condition of a bending radius (R) = 1.5 mm, the display film has no change in appearance.
[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 has at least one direction when subjected to a tensile test at 23 ° C. , A display film having a yield point strain of 8.0% or more, and an adhesive layer provided on at least one surface of the display film.
[9] The foldable display of the present invention has a configuration in which another member is bonded via an adhesive layer of the display film laminate.

デ ィ ス プ レ イ The display film proposed by the present invention is excellent in folding resistance and heat resistance. By laminating this film with other members, a folderable display excellent in folding 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 embodiment 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 of at least one direction of 8.0% when subjected to a tensile test at 23 ° C. A foldable display including the display film described above.
In addition, the yield point strain in at least one direction when the tensile test is performed at 23 ° C. is also simply referred to as yield point strain.
Hereinafter, the display film included in the folderable display of the present invention will be described in detail.

<Display Film>
A display film according to an example of the embodiment of the present invention (hereinafter, may be referred to as “the present film”) contains a polyester resin (A) as a main component, and has a glass transition temperature of 85 ° C. or more and 150 ° C. or less. And a display film having a yield point strain of at least 8.0% in at least one direction when subjected to a tensile test at 23 ° C.

In the present invention, the “main component” refers to a component occupying the largest mass ratio, specifically, 50% by mass or more, more preferably 55% by mass or more, and more preferably 60% by mass or more. Is more preferred.

The inventor has reported that a polyester resin film having a glass transition temperature of 85 ° C. or more and 150 ° C. or less and a yield point strain of a specific value or more has excellent folding resistance and heat resistance as a display film. The present invention has been found to be particularly suitable for foldable applications, and the present invention has been completed.
The present inventor believes that the present film has a relatively large amount of strain before plastic deformation starts, so that the film exhibits folding resistance.

This film is preferably a biaxially stretched film from the viewpoint of providing a thin film and folding resistance.

(1) Glass transition temperature The glass transition temperature (Tg) of the present film is from 85 ° C to 150 ° C, preferably from 86 ° C to 140 ° C, more preferably from 87 ° C to 130 ° C.
When the Tg of the present film is 85 ° C. or higher, the film is not deformed even when the present film is used for display use, and thus is excellent in heat resistance.
On the other hand, when the Tg of the film is 150 ° C. or lower, the film is suitable for workability.
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).
When a plurality of glass transition temperatures are confirmed by DSC measurement, the glass transition temperature (Tg) in the present invention indicates the glass transition temperature on the high temperature side.

(2) Yield point strain When a tensile test at 23 ° C. is performed on the film, the yield point strain in at least one direction is 8.0% or more.
The yield point strain of the present film is preferably 8.5% or more, more preferably 9.0% or more. Although the upper limit of the yield point strain is not particularly limited, it 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 kept within a practical range.
The yield point strain can be adjusted by the stretching conditions and the like when producing the present film.

In the present film, the yield point strain in one direction is within the above range, and the yield point strain in a direction orthogonal to the one direction is preferably 8.0% or more, more preferably 8.5% or more. It is more preferably at least 9.0%, and further preferably at most 50%.
The “one direction” is not particularly limited, but means, for example, 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. I do. Here, MD means "Machine Direction", and TD means "Transverse Direction".
The yield point strain of the film means a strain (%) at a 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 film when subjected to a tensile test at 23 ° C is preferably 50 MPa or more, more preferably 55% or more, and further preferably 60 MPa or more.
Although the upper limit is not particularly limited, it is usually 300 MPa or less in the case of a film made of a polyester resin.
By setting the yield stress of the present film to 50 MPa or more, the film strength is kept within a practical range, and the bending resistance of the film is kept within a practical range. Yield stress can be adjusted by stretching conditions.
The yield stress of the film can be measured by a method according to JIS K 7127: 1999.

(4) Crystal melting temperature The crystal melting temperature (Tm) of the film is preferably from 255 ° C to 300 ° C.
In particular, it is more preferably from 256 ° C to 295 ° C, further preferably from 257 ° C to 290 ° C, particularly preferably from 258 ° C to 285 ° C.
When the crystal melting temperature (Tm) of the present film is in such a range, the present film is excellent in balance between heat resistance and melt moldability.
Here, the crystal melting temperature (Tm) is a value measured at a heating rate of 10 ° C./min using a differential scanning calorimeter (DSC) for the film according to JIS K7121 (2012).
The crystal melting temperature (Tm) means a crystal melting peak temperature.
When a plurality of crystal melting temperatures are confirmed in the DSC measurement, the crystal melting temperature (Tm) in the present invention indicates the highest crystal melting temperature.
The crystal melting temperature (Tm) of the present film is selected by selecting a resin material constituting the present film, adding a crystal nucleating agent, and in producing the present film, a cooling temperature from a molten state, a stretching ratio, a stretching temperature, It can be optimized by adjusting the heat treatment conditions after stretching.

(5) Thickness The thickness of the present film is preferably from 1 to 250 μm, more preferably from 5 to 200 μm. When the thickness is 1 μm or more, the film strength is kept within a practical range.
When the thickness is 250 μm or less, folding resistance is easily developed.
The thickness can be adjusted by stretching conditions.

(6) Folding resistance This film was subjected to 1000 bending tests at 23 ° C. using a bending test apparatus (DLDMLH-FS-C) manufactured by YUASA at a bending radius (R) of 1.5 mm. It is preferable that there is no change in appearance.
By satisfying this, it can be said that the present film is excellent in folding resistance.

The present invention, the present inventors have found that, in general, a film containing a polyester-based resin as a main component showing a relatively high yield stress than polyethylene-based resin and polypropylene-based resin is excellent in bending resistance, the present inventors have made. Things.
Even in the case of a polyester resin having a high yield stress, when the stress applied by the deformation is large, there is a problem that the deformation occurs and unresolved strain remains in the material.
However, the present inventor has found that in the present invention, if the yield point strain is equal to or more than a specific value, the strain hardly occurs.
It is considered that when the material is distorted beyond the elastic deformation region (yield point), deformation marks such as break marks and wrinkles remain, which may affect the appearance and the material properties itself.
In other words, it is considered that the larger the yield point strain amount is, the larger the strain amount until the plastic deformation starts is. Therefore, even when a large strain is applied, it is considered that a deformation mark is hardly formed and the deformation resistance is excellent.

In the present invention, the film may contain other resins other than the polyester resin (A) as long as the effects of the present invention are not impaired.
As other resins, for example, polystyrene resin, polyvinyl chloride resin, polyvinylidene chloride resin, chlorinated polyethylene resin, polycarbonate resin, polyamide resin (including aramid resin), polyacetal resin, acrylic resin 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, polyamidebismaleimide resin, polyetherimide resin, polyether Teruketon resins, polyether ketone resins, polyether sulfone resins, polyketone resins, polysulfone resins, and include fluorine-based resins and the like.

In addition to the components described above, the present film may appropriately contain additives generally compounded within a range that does not significantly impair the effects of the present invention.
Examples of the additives include recycled resins generated from trimming loss of ears and the like, silica, talc, kaolin, calcium carbonate, and the like, which are added for the purpose of improving and adjusting molding processability, productivity, and various physical properties of the film. Inorganic particles, coloring agents such as pigments and dyes such as titanium oxide and carbon black, flame retardants, weather resistance stabilizers, heat stabilizers, antistatic agents, melt viscosity improvers, crosslinking agents, lubricants, nucleating agents, and plasticizers Antioxidants, antioxidants, light stabilizers, ultraviolet absorbers, neutralizers, antifogging agents, antiblocking agents, slip agents and the like.

In addition to the above-mentioned additives, the present film may have a coating layer as long as the effect of the present invention is not significantly impaired.
Examples of the function of the coating layer include a hard coat property, an antistatic property, a peeling property, an easy adhesive property, a printing suitability, a UV cut property, an infrared shielding property, a gas barrier property 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 may be applied outside the system once on the manufactured film, and may employ off-line coating. Is also good.

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

<Polyester resin (A)>
The polyester resin (A) constituting the film may be a homopolyester or a copolyester.
In the case of a homopolyester, those obtained by polycondensing an aromatic dicarboxylic acid and an aliphatic glycol are preferred.
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.
Typical polyesters include polyethylene terephthalate (PET) and the like.
On the other hand, examples of the dicarboxylic acid component of the copolymerized polyester include one or more of isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, sebacic acid, and oxycarboxylic acid. One or more of ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol and the like can be mentioned.
Further, an oxycarboxylic acid such as P-oxybenzoic acid may be used as a copolymer component.
In the present invention, from the viewpoint of the glass transition temperature and the yield point strain, the polyester resin (A) contains terephthalic acid units as the dicarboxylic acid component (a-1) and 1,4-cyclohexane as the diol component (a-2). Preference is given to polycyclohexylene dimethylene terephthalate containing dimethanol units.

The heat of crystal fusion (ΔHm (A)) of the polyester resin (A) is preferably 35 J / g or more and 70 J / g or less, more preferably 36 J / g or more or 65 J / g or less. When ΔHm (A) is within such a range, the polyester resin (A) has appropriate crystallinity that is excellent in heat resistance, wet heat resistance, melt moldability and stretch processability.
The heat of crystal fusion Δ (Hm (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). it can.
The heat of crystal fusion (ΔHm (A)) of the polyester-based resin (A) is, if it is a constituent unit of the (A), for example, polycyclohexylene dimethylene terephthalate, an acid component other than terephthalic acid and / or By adjusting the type and mixing ratio of the diol component other than the 1,4-cyclohexanedimethanol unit, the content can be adjusted within the above range.

The crystal melting temperature (Tm (A)) of the polyester resin (A) is preferably from 255 to 310 ° C, more preferably from 280 to 310 ° C, and from 260 to 340 ° C. 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 in such a range, the polyester resin (A) has an excellent 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-based resin (A) is the same as the ΔHm described above, and in the case of the structural unit of (A), for example, polycyclohexylene dimethylene terephthalate, other acid components other than terephthalic acid By adjusting the type and blending ratio of other diol components other than the 1,4-cyclohexanedimethanol unit, and / or the ratio can be adjusted within the above range.

The glass transition temperature (Tg (A)) of the polyester resin (A) is more preferably from 60 ° C to 150 ° C, and even more preferably from 70 ° C to 120 ° C.
When the glass transition temperature (Tg (A)) of the polyester resin (A) is in such a range, the balance between 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).

The heat of crystal melting (ΔHm (A)), the crystal melting temperature (Tm (A)), and the glass transition temperature (Tg (A)) of the polyester-based resin (A) are all used to produce this film. Of the polyester resin (A) constituting the film of the present invention.

The polycyclohexylene dimethylene terephthalate is a polymer containing terephthalic acid units as the dicarboxylic acid component (a-1) and 1,4-cyclohexanedimethanol units as the diol component (a-2).
In particular, when used in the present invention, polycyclohexylene dimethylene terephthalate contains 90 mol% or more of terephthalic acid units as the dicarboxylic acid component (a-1) and 1,4-cyclohexanedimethanol unit as the diol component (a-2). Is preferably a polymer containing 90 mol% or more of

The dicarboxylic acid component (a-1) constituting the polycyclohexylene dimethylene terephthalate preferably contains at least 90 mol% of terephthalic acid.
Of the dicarboxylic acid component (a-1), terephthalic acid is more preferably at least 92 mol%, even more preferably at least 94 mol%, particularly preferably at least 96 mol%, particularly preferably 98 mol%. It is particularly preferable that the amount is at least as described above, and it is most preferable that all (100 mol%) of the dicarboxylic acid component (a-1) be terephthalic acid.
By setting terephthalic acid to 90 mol% or more as the dicarboxylic acid component (a-1), the glass transition temperature, melting point and crystallinity of polycyclohexylene dimethylene terephthalate are improved, and the heat resistance of the present film is improved.

The polycyclohexylene dimethylene 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.
Specific examples of the acid component other than terephthalic acid include isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 2,5-furandicarboxylic acid. Acid, 2,4-furandicarboxylic acid, 3,4-furandicarboxylic acid, benzophenonedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, 3,3′-diphenyldicarboxylic acid, 4,4′-diphenyletherdicarboxylic acid, etc. Aromatic dicarboxylic acids; cyclohexanedicarboxylic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, aliphatic dicarboxylic acids such as sebacic acid, and the like. From the viewpoint of moldability, isophthalic acid, 2,5-furandicarboxylic acid, 2,4-furandic acid Bon acid, 3,4-furan dicarboxylic acid.

The diol component (a-2) constituting the polycyclohexylene dimethylene terephthalate preferably contains 90 mol% or more of 1,4-cyclohexanedimethanol.
Of the diol component (a-2), 1,4-cyclohexanedimethanol is more preferably at least 92 mol%, even more preferably at least 94 mol%, particularly preferably at least 96 mol%. , 98 mol% or more, and most preferably, all (100 mol%) of the diol component (a-2) is 1,4-cyclohexanedimethanol.
By making 1,4-cyclohexanedimethanol 90 mol% or more as the diol component (a-2), the melting point and crystallinity of polycyclohexylene dimethylene terephthalate are improved, and the heat resistance of the present film is improved.

The polycyclohexylene dimethylene terephthalate may be copolymerized with less than 10 mol% of a diol component other than 1,4-cyclohexanedimethanol for the purpose of improving moldability and heat resistance.
As the diol component other than 1,4-cyclohexanedimethanol, specifically, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6 Hexanediol, neopentyl glycol, ethylene glycol, diethylene glycol, triethylene glycol, polyalkylene glycol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, hydroquinone, bisphenol, spiroglycol, 2,2,4, Examples thereof include 4, -tetramethylcyclobutane-1,3-diol and isosorbide. Of these, ethylene glycol, diethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,3 -Shiku Hexane dimethanol are preferred.

<Production method of this film>
The method for producing the display film of the present invention will be described, but the following description is an example of the method for producing the present film, and the present film is not limited to the film produced by such a production method.

製造 The method for producing 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-based resin (A) as a main component is formed into a film and biaxially stretched.

The method of kneading the polyester resin (A), other resins and additives to obtain a resin composition is not particularly limited. However, in order to obtain the resin composition as simply as possible, melt kneading using an extruder is performed. It is preferably manufactured.
In order to uniformly mix the raw materials constituting the resin composition, it is preferable to perform melt kneading using a co-directional twin screw extruder.
The kneading temperature must be equal to or higher than the glass transition temperature of all the resins used, and must be equal to or higher than the crystal melting temperature of a crystalline resin.
With respect to the glass transition temperature and the crystal melting temperature of the resin used, the higher the kneading temperature is, the easier the transesterification reaction of a part of the resin occurs, and the better the compatibility is, but the kneading temperature is higher than necessary. If it does, the decomposition of the resin occurs, which is not preferable.
For this reason, 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, particularly preferably from 290 ° C to 320 ° C.
When the kneading temperature is within the above range, the compatibility and the melt moldability can be improved without decomposing the resin.
The resin composition may be once cooled and solidified to form a pellet or the like, and then heated and melted again for 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, for example, extrusion molding, injection molding, blow molding, vacuum molding, pressure molding, press molding, etc., to produce a biaxially stretched film. In each molding method, the apparatus and processing conditions are not particularly limited.
This film is preferably produced, for example, by the following method.

From the resin composition obtained by mixing, a substantially amorphous and non-oriented film (hereinafter sometimes referred to as “unstretched film”) is produced by an extrusion method.
The production of this unstretched film includes, for example, an extrusion method in which 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.
At this time, depending on the case, a laminated structure using a plurality of extruders may be used.

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

As the biaxial stretching method, any conventionally known stretching methods such as tenter-type sequential biaxial stretching, tenter-type simultaneous biaxial stretching, and tubular simultaneous biaxial stretching can be used.
For example, in the case of a tenter-type sequential biaxial stretching method, an unstretched film is heated to a temperature range of Tg to Tg + 50 ° C., with the glass transition temperature of the resin composition being Tg, and is vertically stretched by a roll-type longitudinal stretching machine. The film can be produced by stretching the film to 1.1 to 5.0 times, and subsequently stretching the film to 1.1 to 5.0 times in the transverse direction in a temperature range of Tg to Tg + 50 ° C. by 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., stretching is performed 1.1 to 5.0 times in each axial direction simultaneously in the vertical and horizontal directions. Can be manufactured.

The biaxially stretched film stretched by the above method is subsequently heat-set.
By heat setting, dimensional stability at normal temperature can be imparted.
The treatment temperature in this case is preferably selected from the range of Tm-50 to Tm-1 ° C., where Tm is the crystal melting temperature of the resin composition.
When the heat setting temperature is within the above range, the heat setting is sufficiently performed, the stress during stretching is relaxed, sufficient heat resistance and mechanical properties are obtained, and there is no trouble such as breakage or whitening of the film surface. The resulting film is obtained.

In the present invention, in order to relax the stress of crystallization shrinkage due to heat setting, relaxation is performed in the width direction in the range of 0 to 15%, preferably 3 to 10% during heat setting, so that the relaxation is sufficiently achieved. Then, the film is uniformly relaxed in the width direction of the film, the shrinkage in the width direction becomes uniform, and a film having excellent dimensional stability at room temperature is obtained.
Further, since the film is relaxed following the shrinkage of the film, there is no loosening of the film, no flapping in the tenter, and no breakage of the film.

<Polyarylate (B)>
An example of another embodiment of the present film is that, based on 100 parts by mass of the polyester-based resin (A), 1 part by mass or more of polyarylate (B) having a higher glass transition temperature than that of the polyester-based resin (A) is used. This is a display film containing not more than parts by mass.

The difference between the glass transition temperatures of the polyester resin (A) and the polyarylate (B) is preferably 60 ° C. or more, more preferably 70 ° C. or more, even more preferably 80 ° C. or more, and 90 ° C. The temperature is particularly preferably at least 100 ° C.
The glass transition temperature of the polyarylate (B) is preferably from 150 ° C to 350 ° C, more preferably from 160 ° C to 340 ° C, even more preferably from 170 ° C to 330 ° C, It is particularly preferably at least 180 ° C or at most 320 ° C, particularly preferably at least 190 ° C or at most 300 ° C.
When the difference between the glass transition temperatures of the polyester resin (A) and the polyarylate (B) satisfies the above, the glass transition temperature of the film is improved, and the film having excellent melt moldability can be 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, preferably 5 parts by mass with respect to 100 parts by mass of the polyester resin (A). It is more preferably at least 10 parts by mass or at most 47 parts by mass, and even more preferably at least 10 parts by mass or at most 45 parts by mass.
When the proportion of the polyarylate (B) is at least 1 part by mass, the crystallization rate can be reduced, so that the stretchability at the time of stretching the film can be improved.
On the other hand, if the proportion of the polyarylate (B) is at most 50 parts by mass, the crystallinity of the film will be maintained, and the resulting film will have sufficient shrinkage resistance upon heating.

Generally, improvement in heat resistance of a 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-based resin (A), a resin composition having a higher glass transition temperature than that of the polyester-based resin (A) alone can be obtained. An excellent film can be obtained.
On the other hand, when crystallization during stretching occurs remarkably, there is a problem that breakage from a crystal portion is likely to occur during stretching.
Therefore, as will be described later, by adding an amorphous polyarylate (B), the crystallinity of the polyester resin (A) itself is relaxed, the breakage during stretching is suppressed, and the handleability during processing is improved. Can be.

As described above, the present film can include polyarylate (B) having a higher glass transition temperature measured according to JIS K7198A than the polyester resin (A).
The 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). It is preferable to select.

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 is preferably a mixture of a terephthalic acid component and an isophthalic acid component. preferable.
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 more preferably 80/20 to 20 /. 80 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 be obtained by copolymerizing 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, benzophenonedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, 3,3′- Aromatic dicarboxylic acids such as diphenyldicarboxylic acid and 4,4'-diphenyletherdicarboxylic acid, and cyclohexanedicarboxylic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid And the like. The copolymerization ratio of an acid component other than terephthalic acid and isophthalic acid is preferably less than 10 mol% so as not to impair the heat resistance of the polyarylate resin (B).

The dihydric phenol component (b-2) that constitutes the polyarylate (B) is not particularly limited as long as it is a dihydric phenol, but the bisphenol A component and the bisphenol TMC (1,1-bis (4- (Hydroxyphenyl) -3,3,5-trimethylcyclohexane), or both bisphenol A and bisphenol TMC.
In general, a polyarylate having excellent melt moldability (flowability) is obtained by including a bisphenol A component.
On the other hand, by including the bisphenol TMC component, a polyarylate (B) having an improved glass transition temperature and excellent heat resistance can be obtained.
When it is desired to balance the melt moldability and the 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 more preferably 80/20 to 20/20. / 80 is more preferable, 70/30 to 30/70 is particularly preferable, and 60/40 to 40/60 is particularly preferable.
By setting the ratio of the bisphenol A component to the bisphenol TMC component in such a range, a polyarylate (B) having an excellent balance between heat resistance and melt moldability can be obtained.

The polyarylate (B) comprises bisphenol A (2,2-bis (4-hydroxyphenyl) propane) and bisphenol TMC (1,1-bis (4-hydroxyphenyl)-as the dihydric phenol component (b-2). Bisphenol components other than (3,3,5-trimethylcyclohexane) may be copolymerized.
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 ′-(bisphenyl) -2-ol] propane), bisphenol Z (1,1-bis (4-hydroxyphenyl) cyclohexane) and the like.
The copolymerization ratio of the above compound is preferably less than 10 mol% so as not to impair the heat resistance of the polyarylate (B).

The polyarylate (B) contains a mixture of a terephthalic acid component and an isophthalic acid component as a dicarboxylic acid component (b-1) and a dihydric phenol component (b-2) in order to increase the compatibility with polycyclohexylene dimethylene terephthalate. It is preferable to select either bisphenol A component or bisphenol TMC component or a mixture of bisphenol A and bisphenol TMC.

As the polyarylate (B), a mixture of polycarbonate for improving melt moldability may be used.
Since polyarylate (B) and polycarbonate are compatible, mixing polycarbonate with polyarylate (B) can lower the glass transition temperature of polyarylate (B) while maintaining transparency and mechanical properties. As a result, the melt moldability can be improved.
When the polyarylate (B) and the polycarbonate are mixed, the mixing ratio (% by mass) of the polyarylate (B) / polycarbonate is preferably 99/1 to 50/50, more preferably 98/2 = 60/40, It is more preferably from 97/3 to 70/30, particularly preferably from 96/5 to 80/20.
When the mixing ratio of the polyarylate (B) and the polycarbonate is within the above range, the melt moldability can be improved while maintaining the heat resistance of the polyarylate (B).
In addition, the mixing of the polyarylate (B) and the polycarbonate is preferably performed using a mixture of these two components in advance, but is not limited to this method alone. The above structure may be adopted by selecting and using as an independent raw material.

中 で も Among the above-mentioned combinations of the polyester resin (A) and the polyarylate (B), from the viewpoint of compatibility, a combination of polycyclohexylene dimethylene terephthalate and polyarylate is particularly preferable.

When the polycyclohexylene dimethylene terephthalate (A) and the polyarylate (B) are melted and mixed, a part of each of the polycyclohexylene dimethylene terephthalate (A) and the polyarylate (B) undergoes a transesterification reaction. It is considered that the interfacial tension between the polymers is greatly reduced, so that they are compatible with each other and become a resin composition having extremely excellent transparency and heat resistance.

Therefore, the polycyclohexylene dimethylene terephthalate also includes a transesterified product obtained by subjecting a part or all of the polycyclohexylene dimethylene terephthalate to a transesterification reaction. The transesterified product obtained by the exchange is also included.

程度 The degree of transesterification (reaction rate) can be adjusted by melt-mixing conditions such as mixing temperature, shear rate, residence time, etc., whereby the heat of crystal fusion (ΔHm) of the film can also be adjusted.

<Foldable display>
Since the display film according to the present invention is excellent in folding resistance and heat resistance and also excellent in transparency, a folderable display provided with this film is excellent in folding resistance and heat resistance.

The above-described display film (the present film) in the present invention is used as a constituent member for a display, for example, a front plate, a base film for a touch sensor, a lower protective film, and the like, and is connected to another member via an adhesive layer. It is preferable that they are laminated.
More specifically, the display film is preferably a display film laminate including the display film and an adhesive layer provided on at least one surface of the display film, and further, the adhesive layer of the display film laminate is preferably used. It is preferable to provide a foldable display having a configuration in which other members are bonded together through the above.

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 vinylalkyl ether-based pressure-sensitive adhesive, an epoxy pressure-sensitive adhesive, or the like can be used. .
The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is used alone or in combination of two or more.
Examples of the other members include various electronic devices having a display such as a mobile phone, a smartphone, a digital camera, and a personal computer.
Specifically, the display film laminate is used by being attached to a display of these electronic devices via an adhesive layer.
The type of display is not particularly limited, and may be any of a liquid crystal display, a plasma display, an organic EL display, and the like, and may be a touch panel type display.

Examples are shown below, but the present invention is not limited by these.

(1) Glass transition temperature The obtained film was heated once to the melting temperature at a heating rate of 10 ° C./min using Diamond DSC (manufactured by PerkinElmer Japan) in accordance with JIS K7121 (2012). Thereafter, the temperature was lowered at a temperature lowering rate of 10 ° C./min, and the glass transition temperature during the heating process at a heating rate of 10 ° C./min was measured.

(2) Crystal melting temperature For the obtained film, the crystal melting temperature in the heating process at a heating rate of 10 ° C./min according to JIS K7121 (2012) was determined using Diamond DSC (manufactured by PerkinElmer Japan). It was measured.

(3) Formability
Regarding the cast film, when the film was biaxially stretched, the film that could be stretched without breaking was passed (合格), and the film that broke was failed (×).

(4) Yield point strain measuring device used was a tensile tester (a tensile tester AG-1kNXplus manufactured by Shimadzu Corporation). The test piece used was cut out from the present film into a rectangle having a length of 100 mm and a width of 15 mm in the measurement direction. Both ends in the longitudinal direction of the test piece were chucked at 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 the yield strain, and the average value was obtained. In the tensile test, both the MD tensile test and the TD tensile test of the film were performed.

(5) Folding resistance (bending evaluation)
The obtained film was subjected to 1000 bending tests at 23 ° C. using a bending test apparatus (DLDMLH-FS-C) manufactured by YUASA under the conditions of a bending radius (R) of 2 mm, 1.5 mm and 1 mm.が な い indicates no change in appearance, △ indicates slight bending marks, and × indicates clear bending marks.
(Comprehensive evaluation)
The results of the bending test were evaluated as follows.
：: R = 2 mm, no change in appearance in 1.5 mm evaluation, practicality ×: R = 2 mm, change in appearance in at least one evaluation of 1.5 mm, low practicality

[Polyester resin (A)]
(A) -1: SKYPURA0502HC
(Manufactured by SK Chemical Company, dicarboxylic acid component: terephthalic acid = 100 mol%, diol component: 1,4-cyclohexanedimethanol = 100 mol%, Tm = 293 ° C., ΔHm = 48 J / g, Tg = 110 ° C.)

(A) -2: SKYPURA0502
(Manufactured by SK Chemical Company, dicarboxylic acid component: terephthalic acid = 100 mol%, diol component: 1,4-cyclohexanedimethanol = 100 mol%, Tm = 286 ° C., ΔHm = 42 J / g, Tg = 104 ° C.)

(A) -3: SKYPURA1631
(Manufactured by SK Chemical Company, dicarboxylic acid component: terephthalic acid = 91.8 mol%, isophthalic acid = 8.2 mol%, diol component: 1,4-cyclohexanedimethanol = 100 mol%, Tm = 274 ° C., ΔHm = 32 J / g, Tg = 101 ° C.)

[Polyarylate (B)]
(B) -1: U polymer (registered trademark) U-100
(Manufactured by Unitika, dicarboxylic acid component: terephthalic acid / isophthalic acid = 50/50 mol%, bisphenol component: bisphenol A = 100 mol%, Tg (B) = 210 ° C.)

[Biaxially stretched PET film (C)]
(C) -1: Biaxially stretched PET film having a thickness of 50 μm

[PEN film (D)]
(D) -1: 50 μm thick PEN film (TEONEX Q51)

(Example 1)
Pellets (B) -1 were added at a ratio of 30% by mass with respect to 70% by mass of (A) -1 in the form of pellets. After the dry blending, a co-axial twin screw extruder (manufactured by Toshiba Machine Co., Ltd., diameter: 40 mm, ratio L / D of the effective length L of the screw to the outer diameter D = 32) was set to 310 ° C. ), The obtained strand was cooled and solidified in a water tank, and cut with a pelletizer to produce a pellet.
The prepared pellets were melt-kneaded at 310 ° C. using a single screw extruder (manufactured by Mitsubishi Heavy Industries, Ltd.), and a molten resin sheet extruded from a T-die having a gap of 1.0 mm and 310 ° C. was cast with a 115 ° C. cast roll. It was taken out, cooled and solidified to obtain a film having a thickness of about 500 μm.
Subsequently, the obtained cast film was passed through a longitudinal stretching machine and stretched three times in the machine direction (MD) at 125 ° C.
Subsequently, the obtained longitudinally stretched film is passed through a transverse stretching machine (tenter) and 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. The film was subjected to a 10% relaxation treatment in a tenter. The obtained films were evaluated in the above (1) to (5). Table 1 shows the results.

(Example 2)
For the polyester resin (A), a sample was prepared and evaluated in the same manner as in Example 1 except that (A) -2 was used instead of (A) -1. Table 1 shows the results.

(Example 3)
For the polyester resin (A), a sample was prepared and evaluated in the same manner as in Example 1 except that (A) -3 was used instead of (A) -1. Table 1 shows the results.

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

(Comparative Example 2)
Table 1 shows the results of the evaluation of the PEN film (D) -1.

フ ィ ル ム In Examples 1 to 3, films could be produced without any particular problems during molding. The films of Examples 1 to 3 have a high crystal melting temperature and a high glass transition temperature, and have excellent heat resistance. The films of Examples 1 to 3 were clearly different from Comparative Examples 1 and 2 in the evaluation at R = 1 and 1.5. Therefore, the films of Examples 1 to 3 are excellent in folding resistance.

Claims (9)

1. A display comprising 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 subjected to a tensile test at 23 ° C. Display with film
2. The polyester resin (A) is a polycyclohexylene dimethylene terephthalate containing a terephthalic acid unit as a dicarboxylic acid component (a-1) and a 1,4-cyclohexanedimethanol unit as a diol component (a-2). Item 4. The folderable display according to Item 1.
3. 3. The foldable display according to claim 2, wherein the polycyclohexylene dimethylene terephthalate has a crystal melting temperature of 255 ° C. or more and 310 ° C. or less.
4. The display film contains 1 part by mass or more and 50 parts by mass or less of polyarylate (B) having a higher glass transition temperature than that of the polyester resin (A) based on 100 parts by mass of the polyester resin (A). The folderable display according to any one of claims 1 to 3.
5. The folderable display according to any one of claims 1 to 4, wherein the display film has a crystal melting temperature of 255 ° C or more and 300 ° C or less.
6. The folderable display according to any one of claims 1 to 5, wherein the display film has a thickness of 1 to 250 μm.
7. The foldable display according to any one of claims 1 to 6, wherein the display film has no change in appearance when subjected to 1000 bending tests at 23 ° C under a condition of a bending radius (R) of 1.5 mm. .
8. A display comprising 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 subjected to a tensile test at 23 ° C. A display film laminate comprising: a film for display; and an adhesive layer provided on at least one surface of the film for display.
9. A fillable display having a configuration in which another member is bonded via an adhesive layer of the display film laminate according to claim 8.