KR102373267B1 - Optical film and film structure - Google Patents

Abstract

The present invention provides an optical film and a film body in which appearance quality defects occurring during storage are resolved by solving thin film interference caused by poor winding of the optical film.

Description

Optical film and film body {Optical film and film structure}

The present invention relates to an optical film and a film body.

Recently, as one of the next-generation displays, flexible electronic devices such as flexible OLED, flexible optoelectronic devices, lightweight displays, flexible encapsulants, Color EPD, Plastic LCD, TSP, OPV, etc. there is. In particular, as devices such as foldable or rollable devices that can be bent or rolled are being developed, a new type of flexible substrate that can realize a flexible type display and protect the underlying device is required. Do.

As a material for such a flexible display substrate, various high-hardness plastic substrates are being considered as candidates, and among them, an optical film containing a polyimide-based resin capable of realizing high hardness in a thin thickness is considered as a particularly important candidate for a cover substrate. there is.

Such an optical film is usually manufactured by casting a varnish containing a polyimide-based polymer and a solvent on a substrate and then drying it, and the prepared film is rolled up in a roll form through a winding treatment for storage (hereinafter also referred to as rolling). box).

At this time, when a winding defect occurs, a thin air layer may be partially included between the thin films, and this causes interference between the thin films, which causes diagonal wrinkles or indentations on the exterior or causes the films to stick together, resulting in shape defects.

Accordingly, it is required to solve the thin film interference caused by the winding defect or to improve the appearance defect caused by this.

Japanese Patent Laid-Open No. 2019-77191

It is an object of the present invention to provide an optical film and a film body in which the appearance quality defects occurring during storage are resolved by solving the thin film interference caused by the winding defect of the optical film.

According to one aspect of the present invention,

An optical film comprising a transparent polyimide-based resin, comprising:

The optical film was subjected to measurement of the initial static electricity value (kV) at 10 randomly selected sites, and the peeling electrostatic value (kV) was measured at 10 randomly selected sites on the surface within 1 minute, and calculated by Equation 1 below. Provided is an optical film having an applied charging parameter value of 0.0005 to 0.0035.

[Equation 1]

(In Equation 1, Sr and Sp are the average values of the initial static electricity measurement value (kV) and the peeling static electricity measurement value (kV) measured at room temperature and 25% relative humidity, respectively, and D is the thickness (mm) of the optical film, L is the width (mm) of the optical film, T is the curing step shrinkage (%) of the gel film formed during the production of the optical film is calculated by the following formula (2).

[Equation 2]

{(length before measurement - length after measurement)/length before measurement} x 100

(In Equation 2, the length before measurement is the length (mm) of the gel film measured by TMA (room temperature), and the length after the measurement is the length (mm) of the gel film measured by TMA (280 degrees).)

In addition, the optical film was cut to 400mm x 400mm x Dmm so that the inner diameter from the center to the end of the optical film was 1 inch and stored in a roll form for 120 hours, and then the charging parameter value calculated by Equation 1 was 0.0005~ It may be 0.0035.

In addition, the peeling static electricity value and the initial static electricity value may be measured on the surface after loosening the roll shape by turning it twice.

Here, the Sr may be 4.5 or less.

In addition, the Sp may be 11.5 or less.

In addition, the shrinkage ratio calculated by Equation 2 may be 5% or less.

In addition, it is possible to provide an optical film having a total light transmittance of 88% or more.

Here, the transparent polyimide-based resin may be a polymer having a fluorine group.

In addition, the transparent polyimide-based resin may include a repeating unit derived from a bis(trifluoromethyl)benzidine derivative.

According to another aspect of the present invention,

A film forming step of casting a varnish containing a transparent polyimide-based resin into a film to provide a gel film of a first size; and

a tenter step of stretching the gel film to a second size by performing a tenter process;

As a method of manufacturing an optical film comprising a curing step of curing after performing the tenter step,

The tenter step provides a method of manufacturing an optical film for compensating for shrinkage of the gel film in the curing step by making the gel film of the second size larger than the first size.

In addition, the tenter step may be to perform stretching by calculating the shrinkage rate of the gel film in advance in the curing step to determine the second size.

In addition, after the curing step, the optical film is wound and then the quality determination step of inspecting the appearance of the film; further comprising,

The quality determination step is performed by measuring the initial static electricity value (kV) at 10 randomly selected portions of the optical film and measuring the peeling static electricity value (kV) at 10 randomly selected portions of the surface within 1 minute. It may be to determine whether the value calculated by Equation 1 is 0.0005 to 0.0035.

[Equation 1]

(In Equation 1, Sr and Sp are the average values of the initial static electricity measurement value (kV) and the peeling static electricity measurement value (kV) measured at room temperature and 25% relative humidity, respectively, and D is the thickness (mm) of the optical film, L is the width (mm) of the optical film, T is the curing step shrinkage (%) of the gel film formed during the production of the optical film is calculated by the following formula (2).

[Equation 2]

{(length before measurement - length after measurement)/length before measurement} x 100

(In Equation 2, the length before measurement is the length (mm) of the gel film measured by TMA (room temperature), and the length after the measurement is the length (mm) of the gel film measured by TMA (280 degrees).)

According to another aspect of the present invention,

As a film body comprising the above-described optical film,

On one side or both sides of the optical film, a primer film, a hardness reinforcement film, a flexible film, a fold-back film, a flexural strength reinforcement film, a visibility improvement film, a barrier film, an antibacterial film, a water-repellent film, an anti-fingerprint film, an anti-reflection film And it provides a film body comprising at least one selected from the film providing a smooth touch feeling.

The optical film according to embodiments of the present invention can compensate for shrinkage in a subsequent curing process as a stretched film is prepared by reflecting the shrinkage rate during the production of the film, and thin film interference to occur in the winding process can be removed in advance.

Therefore, the manufactured film can be manufactured to have a peeling static electricity value and an electrification parameter that does not cause diagonal wrinkles and indentations, so that it is possible to provide an optical film in which appearance quality defects are resolved.

Furthermore, it is possible to effectively determine the shape or condition of the optical film appearance by using the corresponding parameter.

The optical film manufactured according to an embodiment of the present invention and having excellent inter-thin interference suppression ability is excellent in resolving quality defects in appearance even when the thickness of the film is relatively thick.

1 is a photograph of visually observing the surface of a roll after winding treatment of a commercially available film product.
2 is a photograph of visually observing defects on the surface of a roll after winding each of the film products manufactured according to Examples and Comparative Examples, the left drawing is an optical film according to an embodiment of the present invention, and the right drawing is a comparison An optical film according to an example.
3 is a photograph confirming surface defects by using a three-wavelength fluorescent lamp after the film roll of the comparative example on the right of FIG. 2 was left for 120 hours and then unscrewed by turning twice.
4 is a photograph confirming surface defects using a three-wavelength fluorescent lamp after the film roll of the example on the left of FIG. 2 was left for 120 hours and then unscrewed by turning twice.

Before describing the present invention in detail, it is to be understood that the terminology used herein is for the purpose of describing specific embodiments only, and does not limit the scope of the present invention, which is limited only by the appended claims.

All technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art, unless otherwise stated.

Throughout this specification and claims, unless otherwise stated, the term comprise, comprises, comprising means including the referenced object or step or set of objects or groups of steps, and any It is not used in the sense of excluding other objects or steps, groups of objects or groups of steps.

On the other hand, various embodiments of the present invention may be combined with any other embodiments unless clearly indicated to the contrary. In particular, any feature indicated as preferred or advantageous may be combined with any other feature indicated as preferred or advantageous.

In this specification, the term "film" generally refers to a thin plate-like member, but also includes the concept of a film formed by liquid coating.

In the present specification, the term "film body" is intended to include a structure including one or more layers of the above-described film or a laminated structure, and furthermore, a device having such a structure.

In the present specification, the term "polyimide-based" is intended to collectively include polyimide, polyamide, and polyimide-based.

In addition, the concept of “positioning on” in the present specification should be understood as being located “on” not only directly located thereon, but also other members intervening therebetween.

In addition, in this specification, "to" or "to" is used in the meaning including the numerical value described before and after it as a lower limit value and an upper limit value.

(optical film)

The optical film according to an embodiment of the present invention includes a transparent polyimide-based resin that is a copolymer of a diamine compound, a dianhydride compound, and a dicarbonyl compound. The optical film of the present invention may be an optical film obtained without ever being wound into a roll, or may be an optical film cut out to a predetermined size after unwinding the roll-shaped optical film.

The optical film was subjected to measurement of the initial static electricity value (kV) at 10 randomly selected sites, and the peeling electrostatic value (kV) was measured at 10 randomly selected sites on the surface within 1 minute, and calculated by Equation 1 below. The value (hereinafter referred to as the charging parameter) is in the range of 0.0005 to 0.0035.

As a specific example, after preparing the optical film in the size of 500mm x 500mm x Dmm, and then rolling it so that the inner diameter from the center to the end of the optical film cut to 400mm x 400mm x Dmm becomes 1 inch, it is stored in a roll form for 120 hours and then stored in the following The charging parameter value calculated by Equation 1 is 0.0005 to 0.0035, preferably 0.0005 to 0.0035, and more preferably 0.0010 to 0.0035.

Since the above charging parameter values are satisfied, the optical film of the present invention is not observed in shape defects such as oblique wrinkles or indentations even if the optical film of the present invention is stored in a roll state and then unwrapped.

[Battle Parameters]

The charging parameter may be calculated by Equation 1 below.

[Equation 1]

In Equation 1, Sr and Sp are the average values of the initial static electricity measurement value (kV) and the peeling static electricity measurement value (kV) measured at room temperature and 25% relative humidity, respectively, D is the thickness of the optical film (mm), L is the width (mm) of the optical film.

As described above, the optical film was cut to 400mm x 400mm x Dmm so that the inner diameter from the center to the end of the optical film was 1 inch and stored in a roll form for 120 hours, and then the charging parameter value calculated by Equation 1 was It may be 0.0005 to 0.0035.

When the charging parameter is 0.0005 to 0.0035, the friction coefficient between thin films of the optical film is lowered, so that the slip property of the optical film is improved, and the interference suppression ability between thin films of the palm is increased, thereby preventing appearance defects that may occur when stored in a roll form. Since products produced from transparent polyimide-based resins are stored in roll form, if they tend to generate less static electricity during storage or peeling, it is thought to provide the effect of improving poor appearance and facilitating storage.

The charging parameter is preferably 0.0010 to 0.0035, more preferably 0.0015 to 0.0035, from the viewpoint of further improving the inter-thin interference suppression ability, slip property (friction coefficient) and poor appearance of the optical film.

As means for adjusting the charging parameter, for example, means for adjusting the degree of polymerization of the transparent polyimide-based resin, means for inhibiting the progress of the oxidation reaction of the terminal amino group by an oxidizing agent such as peroxide, means for adjusting additives, or film production During the curing step, the shrinkage rate of the gel film may be mentioned.

Here, the means for adjusting the polymerization degree includes, for example, polymerization conditions (specifically, polymerization time, polymerization temperature, use of catalyst, type of solvent, concentration of monomer, etc.).

Further, as the means for inhibiting the progress of the oxidation reaction, for example, means for reducing the concentration of peroxide in the varnish for producing an optical film (specifically, means for inhibiting the production of peroxide in the varnish, etc.) there is.

The varnish includes a transparent polyimide-based resin and a solvent. It is inferred that the peroxide in the varnish is mainly generated by the reaction between the solvent molecules in the varnish and the dissolved oxygen (oxidation reaction of the solvent molecules). For this reason, as a means for suppressing the formation of a peroxide in a varnish, for example, a means for reducing the dissolved oxygen concentration in a varnish, and a means for selecting the kind of solvent which reacts with oxygen to generate|occur|produce a peroxide easily are mentioned.

Means for reducing the dissolved oxygen concentration in the varnish include, for example, a means for bubbling the solvent in an inert atmosphere such as argon or nitrogen gas to replace the dissolved oxygen in the solvent with an inert gas; Means for reducing the oxygen concentration of gaseous phase, etc. are mentioned. At this time, it is preferable that the bubbling treatment time is, for example, 10 minutes or more and 1 hour or less in terms of providing sufficient replacement of dissolved oxygen and reducing cost. Further, after preparing the varnish, a bubbling treatment may be performed on the varnish.

In addition, as a means for controlling the additive, for example, a means for controlling the content in consideration of the degree of dispersion for each type of additive may be mentioned. A specific example may be a means for controlling the content of the filler.

In addition, curing conditions (specifically, curing temperature, etc.) may be mentioned as a means of affecting the shrinkage rate of the gel film in the curing step during film production.

The shrinkage and expansion behavior of the gel film according to the curing temperature can be measured through TMA. For example, TMA can be measured in a nitrogen atmosphere while raising the temperature from room temperature to 350°C by 10°C/min using a TMAQ400 of TA Instrument.

[Shrinkage]

In Equation 1, T is a shrinkage rate (%) calculated to compensate for the shrinkage of the gel film formed during the manufacture of the optical film during the curing step, and may be calculated by Equation 2 below.

[Equation 2]

{(length before measurement - length after measurement)/length before measurement} x 100

Here, the length before measurement is the length (mm) of the gel film measured by TMA (room temperature), and the length after the measurement is the length (mm) of the gel film measured by TMA (280 degrees).

The shrinkage rate according to Equation 2 may be 5% or less, 3% or less, or 2% or less at 280°C, which is the highest curing temperature condition.

According to an embodiment of the present invention, when a film having a first size is formed and then stretched to a second size in a tenter process by reflecting the shrinkage result according to Equation 2 above, the thin film interference ability of the product surface is reduced in advance to reduce the appearance Quality defects can be eliminated.

As a result, in the optical film according to an embodiment of the present invention, when the electrification parameter calculated by Equation 1 including the above-mentioned shrinkage rate as a variable is 0.004 or less, the thin film interference ability and the slip property (coefficient of friction) of the film can be secured. there is.

For reference, the effect of stretching as much as the shrinkage rate occurs even if the tenter width length is not adjusted during curing of the film. In the case of stretching to the second size with a shrinkage ratio of % or less, it is preferable to obtain a film having reduced thin-film interference reduction ability and charging parameters without breakage in the tenter.

[Initial static electricity]

When the average of the initial static electricity measurement values corresponding to the variable Sr in Equation 1 is 4.5 or less, the surface friction coefficient of the optical film is lowered and the interference suppression ability between thin films is increased. It is thought that this is because the additive on the film surface in the transparent polyimide-based resin weakens the attractive force between the polymer chains, so that static electricity tends to be less generated during contact or peeling between thin films. It is more preferable because it is possible to more effectively weaken the attraction between the polymer chains described above.

The initial static electricity is 4.5 or less, preferably 1 to 4.5, more preferably 2 to 4.5 or less, from the viewpoint of further improving the interference suppression ability (or coefficient of friction) between thin films of the optical film. The measurement method is described in detail in the Examples.

At this time, the initial static electricity value may be a value measured on the surface of the roll-shaped optical film by rotating it twice.

[Peeling Static Electricity]

If the average of the measured peeling static electricity corresponding to the variable Sp in Equation 1 is 11.5 or less, the surface friction coefficient of the optical film is lowered and the inter-thin film interference suppression ability is increased. It is thought that this is because the additive on the film surface in the transparent polyimide-based resin weakens the attractive force between the polymer chains, so that static electricity tends to be less generated during contact or peeling between thin films. It is preferable because it is possible to more effectively weaken the attraction between the polymer chains described above.

The peeling static electricity is 11.5 or less, preferably 5 to 11.5, more preferably 7 to 10.5, from the viewpoint of further improving the inter-thin interference suppression ability (or coefficient of friction) of the optical film. The measurement method is described in detail in the Examples.

At this time, the peeling static electricity value may be a value measured on the surface after the roll-shaped optical film is unwound by turning it twice, and it is preferable that it is a value measured within 1 minute after the initial static electricity measurement at the 10 sites where the initial static electricity value is measured.

[thickness]

The thickness of the optical film corresponds to the variable D in Equation 1, preferably 10 to 100 μm (D-converted value 0.01 to 0.1 mm), more preferably 10-90 μm (D-converted value 0.01 to 0.09 mm), further preferably Usually, it is 20~85um (D-converted value 0.02~0.85mm). If the thickness is 10 μm or more, it is advantageous in terms of internal protection when an optical film is used as a device, and if the thickness is 100 μm or less, it is advantageous in terms of stretching of the film considering shrinkage, interference suppression ability between thin films, friction coefficient and productivity.

[Transmittance]

The total light transmittance of the optical film is preferably 88% or more.

[Transparent polyimide resin]

(Transparent polyimide resin obtained by polymerization and imidization)

The transparent polyimide-based resin includes, for example, polyimideamide, polyimide, polyamide, and derivatives thereof comprehensively. For example, the term polyimide as used herein refers to a polymer containing a repeating structural unit including an imide group.

The transparent polyimide-based resin is preferably a polymer having a fluorine group from the viewpoint of simultaneously considering the interference suppression ability (coefficient of friction) and transparency between the thin films of the transparent polyimide-based resin film.

The transparent polyimide-based resin preferably contains a repeating unit derived from a 2,2'-bis(trifluoromethyl)benzidine derivative. In addition, the 2,2'-bis(trifluoromethyl)benzidine derivative in the present specification includes 2,2'-bis(trifluoromethyl)benzidine.

Specifically, in the present invention, the transparent polyimide-based resin comprises (i) diamine and dianhydride (ii) diamine, dianhydride and aromatic dicarbonyl compound, (iii) diamine, dianhydride and dianhydride or (iv) ) formed by copolymerization and imidization with any one of a combination of diamine, dianhydride, dianhydride, and aromatic dicarbonyl compound, in which case the sum of the remaining monomers with respect to diamine is diamine and an equivalent ratio of 1:1 will achieve Among the above combinations, it is preferable to add dianhydride to cap the ends of the polyimide molecular chain, but the present invention is not necessarily limited thereto.

The dianhydride that can be used in the present invention is 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA), 4- (2,5-dioxotetrahydrofuran-3- yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic dianhydride (TDA), pyromellitic acid dianhydride (1,2,4,5-benzene tetracarboxylic dianhydride, PMDA), benzophenone tetracarboxylic dianhydride (BTDA), biphenyl tetracarboxylic dianhydride (BPDA), biscarboxyphenyl dimethyl silane dianhydride (SiDA), oxydiphthalic dianhydride Ride (ODPA), bis dicarboxyphenoxy diphenyl sulfide dianhydride (BDSDA), sulfonyl diphthalic dianhydride (SO ₂ DPA), cyclobutane tetracarboxylic dianhydride (CBDA), isopropylidene It may include alone or two or more selected from phenoxy bis phthalic dianhydride (6HDBA). It is not limited thereto.

In addition, the diamine that can be used in the present invention is oxydianiline (ODA), p-phenylenediamine (pPDA), m-phenylenediamine (mPDA), p-methylenedianiline (pMDA), m-methylenedianiline ( mMDA), bistrifluoromethyl benzidine (TFDB), cyclohexanediamine (13CHD, 14CHD), bisaminohydroxyphenyl hexafluoropropane (DBOH), bisaminophenoxybenzene (133APB, 134APB, 144APB), bisamino Phenyl hexafluoropropane (33-6F, 44-6F), bisaminophenylsulfone (4DDS, 3DDS), bisaminophenoxyphenylhexafluoropropane (4BDAF), bisaminophenoxyphenylpropane (6HMDA), bisamino It may include alone or two or more selected from phenoxy diphenyl sulfone (DBSDA) and the like, but is not limited thereto.

In addition, the dianhydride that can be used in the present invention is bicyclo heptene dicarboxylic dianhydride (Nadic anhydride), anthracenylethynyl phthalic dianhydride (4-(9-anthracenyl ethynyl)phthalic anhydride), a Damantanecarbonyl chloride (1-Adamatanecarbonyl chloride), adamantanedicarbonyl dichloride (1,3-Adamantanedicarbonyl dichloride), norbornene carbonyl chloride (5-Norbonene-2-carbonyl chloride), norbornene dicarbonyl chloride ( 5-Norbonene-2,3-dicarbonyl chloride) and cyclopentane carbonyl chloride (cyclopentane chloride) may include alone or two or more selected from the like, but is not limited thereto.

In addition, when the polyimide of the present invention is a polyamide-imide having an amide structure, an aromatic dicarbonyl compound may be added as a monomer. In this case, as an aromatic dicarbonyl compound that can be used, terephthaloyl dichloride (p-Terephthaloyl chloride), terephthalic acid (Terephthalic acid), iso-phthaloyl dichloride (Iso-phthaloyl dichloirde), 4,4'-biphenyl dicarbonyl chloride (4,4'-biphenyldicarbonyl chloride), etc. alone or There may be two or more types, but is not limited thereto.

The process of manufacturing the polyimide-based film in a roll-to-roll method by using the above monomers is not particularly limited, but an example of the manufacturing method in the present invention will be described as follows.

A monomer selected from among the above-mentioned monomers is dissolved in a first solvent and then subjected to a polymerization reaction to first prepare a polyamic acid solution (a polyimide or polyimide-amide precursor). At this time, the reaction conditions are not particularly limited, but the reaction temperature is preferably -20 to 80°C, and the reaction time is preferably 2 to 48 hours. In addition, it is more preferable that the reaction is in an inert atmosphere such as argon or nitrogen.

In the case of adding dianhydride among the monomers, the molecular weight is affected according to the amount of dianhydride added during the reaction, and 10 mol% or less based on the total mole of dianhydride and dianhydride so as not to reduce the intrinsic physical properties of the polyimide. , preferably in an amount of 5 mol% or less. When a large amount exceeding 10 mol% is used, the optical properties are reduced as the yellowness increases and the transmittance decreases as the molecular weight is lowered. However, a large amount of crosslinking disturbs the arrangement of the polymer chains, and thus the surface hardness may be reduced.

In addition, if you want to obtain a polyimide-based film having a polyamide-imide structure, the molecular weight may vary depending on the amount of the aromatic dicarbonyl compound in the monomer. It is preferable to add 10 mol% or more, 80 mol% or less, preferably 30 mol% or more, 70 mol% or less to the total moles of the aromatic dicarbonyl compound component. When a large amount exceeding 80 mol% is used, the optical properties are reduced such that yellowness is increased and transmittance is lowered, and a gel is generated in the polyamic acid solution, making it difficult to obtain a film during film formation. In addition, when 10 mol% or less is used, optical properties are increased, but a decrease in thermal properties such as a decrease in the coefficient of thermal expansion may also occur.

The solvent for the polymerization reaction of the monomers is not particularly limited as long as it is a solvent that dissolves the polyamic acid. One selected from m-cresol, N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), acetone, and ethyl acetate as a known reaction solvent Use more polar solvents. In addition, a low-boiling-point solution such as tetrahydrofuran (THF), chloroform, or a low-absorption solvent such as γ-butyrolactone may be used.

The content of the solvent is not particularly limited, but in order to obtain an appropriate molecular weight and viscosity of the polyamic acid solution, the content of the first solvent is preferably 50 to 95% by weight of the total polyamic acid solution, more preferably 70 to 90% by weight % is more preferable.

In this way, a polyimide-based film can be prepared by polymerizing the polyamic acid solution and forming a film by imidization and heat treatment at a high temperature. In this case, the prepared polyimide-based resin preferably has a glass transition temperature of 200 to 400° C. in consideration of thermal stability.

As a method of manufacturing a polyimide-based film from a polyamic acid solution, there is a thermal imidization method, a chemical imidization method, or a method of using a thermal imidization method and a chemical imidization method in combination.

The chemical imidization method is a method in which a dehydrating agent represented by an acid anhydride such as acetic anhydride and an imidization catalyst represented by tertiary amines such as isoquinoline, β-picoline, and pyridine are added to a polyamic acid solution. When the thermal imidization method or the thermal imidization method and the chemical imidization method are used in combination, the heating conditions of the polyamic acid solution may vary depending on the type of the polyamic acid solution and the thickness of the polyimide-based film to be prepared.

If the production example of the polyimide-based film in the case of using the thermal imidization method and the chemical imidization method in combination is described in more detail, a dehydrating agent and an imidization catalyst are added to a polyamic acid solution, and after casting on a support, 80 to 200 ° C. , preferably by heating at 100 to 180° C. to activate a dehydrating agent and imidization catalyst to partially harden and dry the polyamic acid film in a gel state by peeling it from the support, fixing the gel film to the support and heat-treating the polyimide system film can be obtained. The gel film can be fixed using a pin-type frame or a clip-type frame. A glass plate, an aluminum foil, a circulation stainless belt, a stainless drum, etc. may be used as the support body.

Meanwhile, in the present invention, a polyimide-based film may be prepared from the obtained polyamic acid solution as follows. That is, after imidizing the obtained polyamic acid solution, the imidized solution is put into a second solvent, precipitated, filtered, and dried to obtain a polyimide-based resin solid content, and then the obtained polyimide-based resin solid content is reconstituted. It is dissolved in the first solvent, cast on a support, and heated for 1 minute to 8 hours while gradually increasing the temperature in the temperature range of 40 to 400° C. as described above to obtain a gel-like polyimide-based film.

The first solvent may be the same solvent as the solvent used for polymerization of the polyamic acid solution, and the second solvent is less polar than the first solvent in order to obtain a solid content of the polyimide-based resin, and specifically, water , alcohols, ethers, and ketones may be one or more selected from the group consisting of.

At this time, the content of the second solvent is not particularly limited, but is preferably 5 to 20 times by weight compared to the weight of the polyamic acid solution.

The conditions for drying the obtained polyimide-based resin solid content after filtering are preferably 50 to 150° C. and 2 to 30 minutes for the time, in consideration of the boiling point of the second solvent.

In addition, when preparing a polyimide-based film, a filler may be added during the preparation of the polyamic acid solution for the purpose of improving various properties such as fold resistance, sliding property, thermal conductivity, and conductivity of the film.

The filler is not particularly limited, but preferred embodiments include silica, titanium oxide, layered silica, carbon nabotube, alumina, silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, mica, and the like.

The particle diameter of the filler may vary depending on the characteristics of the film to be modified and the type of filler to be added, and is not particularly limited, but in general, the average particle diameter is preferably 0.001 to 50 μm, and 0.005 to 25 μm. More preferably, it is good that it is 0.01-10 micrometers more preferably. In this case, the effect of modifying the polyimide-based film is easy to appear, and good surface properties, conductivity and mechanical properties can be obtained in the polyimide-based film.

In addition, the amount of the filler added may vary depending on the characteristics of the film to be modified and the type of filler to be added, and is not particularly limited. In general, the content of the filler is preferably 0.001 to 20 parts by weight, more preferably 0.01 to 10 parts by weight, based on 100 parts by weight of the polyamic acid solution, in order to exhibit the properties to be modified without interfering with the bonding structure of the polymer resin. It's good to be Mrs.

According to one embodiment of the present invention, the manufacturing method of the optical film may include a varnish preparation step, a film forming step, a tenter step and a curing step.

Here, in the varnish preparation step, a liquid resin composition is prepared using the aforementioned diamine compound, dianhydride compound, and dicarbonyl compound.

Then, in the film forming step, the varnish is cast into a film to provide a gel film of a first size. The varnish preparation step includes a polymerization step of preparing a polymer solution by reacting compound components in the presence of a first solvent, a powder step of adding a second solvent to the polymer solution, filtration and drying to form a polymer solid content, and the polymer solid content It may include a dissolution step of dissolving in a third solvent.

The varnish has a viscosity of 80,000 to 200,000 cPs, or 100,000 to 160,000 cPs.

Since the first solvent and the second solvent use a solvent having a high boiling point, drying by heat treatment after cast film formation may be performed for the purpose of removing them.

In general, the drying efficiency increases as the temperature increases. On the other hand, when the drying temperature increases and the drying temperature approaches the boiling point of the solvent, air bubbles may be generated on the surface of the optical film due to sudden volatilization of the solvent, and curvature may occur, so that the surface uniformity of the optical film this is lowered

Accordingly, in the heat treatment step, drying is performed at a temperature of 50° C. or higher to secure drying efficiency, and drying is performed at a temperature of 150° C. or lower to prevent sudden volatilization of the solvent. In order to improve drying efficiency, drying may be performed in a temperature range of 70 to 150°C.

According to an embodiment of the present invention, after drying, the residual solvent content ratio of the uncured polyimide film may be adjusted to 50% by weight or less. More specifically, after drying, the residual solvent content ratio of the uncured polyimide film may be adjusted to 25 wt% or less.

Then, a tenter process of stretching the gel film is performed to perform a tenter step of stretching to a second size. The tenter step is to perform stretching by determining the second size by calculating the shrinkage rate of the gel film in advance in the curing step to be described later.

As a specific example, the tenter step compensates for the shrinkage of the gel film in the curing step by making the gel film of the second size larger than the first size.

As described above, the tenter process is performed by increasing the gel film by reflecting the shrinkage rate calculated by Equation 2, specifically, the tenter width length in tenter curing is 5% or less, 3% or less, 2% or less, or It is possible to remove the thin film interference ability of the manufactured optical film in advance by adjusting the range of more than 0% to 2% or less to perform the tenter process and compensate for the shrinkage of the film occurring in the curing process to be described later.

After performing the tenter step, a curing step of curing is performed to obtain an optical film. At this time, the curing may be performed, for example, at a temperature of 120 to 320° C. at a wind speed of 1.0 to 3.0 m/s for 1 minute to 2 hours.

When the wind speed of curing is less than 1.0 m/s or the temperature is less than 120° C., the speed of curing may be excessively reduced. When the curing rate is excessively reduced, the efficiency of the process is reduced, and the physical properties of the polyimide-based film may be changed due to an increase in curing time.

The wind speed in the curing step may be performed, for example, in the range of 1.5 to 3.0 m/s for 10 minutes to 2 hours, and preferably the wind speed may be adjusted in the range of 1.5 to 2.0 m/s.

The curing step may be performed on a support, or may be made on a separate heat treatment support. For example, a pin-type frame or a clip-type frame may be used to support the gel film.

According to an embodiment of the present invention, the content of volatile components remaining in the polyimide-based film after curing may be adjusted to be 50 ppm.

According to one embodiment of the present invention, after the curing step, the optical film is wound and then the quality determination step of inspecting the appearance of the film; may include.

At this time, the initial electrostatic value (kV) was measured at 10 randomly selected sites for the film, and the peeling electrostatic value (kV) was measured at 10 randomly selected sites on the surface within 1 minute by the following formula 1 If the calculated value is between 0.0005 and 0.0035, it can be determined as passing.

As an example, the optical film is rolled to have an inner diameter of 1 inch and made into a roll, stored at 25 degrees at 25% relative humidity for 120 hours, and then loosened by rotating twice, and then the initial static electricity value (kV) and peeling static electricity value (kV) can be measured.

[Equation 1]

(In Equation 1, Sr and Sp are the average values of the initial static electricity measurement value (kV) and the peeling static electricity measurement value (kV) measured at room temperature and 25% relative humidity, respectively, and D is the thickness (mm) of the optical film, L is the width (mm) of the optical film, T is the curing step shrinkage (%) of the gel film formed during the production of the optical film is calculated by the following formula (2).

[Equation 2]

{(length before measurement - length after measurement)/length before measurement} x 100

(In Equation 2, the length before measurement is the length (mm) of the gel film measured by TMA (room temperature), and the length after the measurement is the length (mm) of the gel film measured by TMA (280 degrees).)

If necessary, visual inspection and additional inspection using a halogen lamp can be performed in parallel.

The film body according to an embodiment of the present invention is on one side or both sides of the optical film, a primer film, a hardness-reinforced film, a flexible film, a retractable film, a flexural strength-reinforced film, a visibility improvement film, a barrier film, an antibacterial film, It may include at least one selected from a water-repellent film, an anti-fingerprint film, an anti-reflection film, and a film providing a smooth touch.

A window member according to another embodiment of the present invention includes a glass cover; and an optical film provided on at least one surface of the glass cover, wherein the optical film is a film including the above-described transparent polyimide-based resin.

A window member according to another embodiment of the present invention includes a glass cover; and a film body provided on at least one surface of the glass cover, wherein the film body is a window member comprising the above-described transparent polyimide-based resin.

Example

Hereinafter, the present invention will be described in more detail through examples. These examples are only for illustrating the present invention in more detail, and the present invention is not limited thereto. The amount of TPC used as a dicarbonyl compound presented as an example may be changed within an error range depending on the viscosity value.

In the following description, "%" and "part" indicating amounts are by weight unless otherwise specified. In addition, the operation described below was performed under the conditions of normal temperature and normal pressure, unless otherwise stated. A "specimen" means what cut out the film which concerns on the Example and the comparative example mentioned below to predetermined size.

<Preparation Example 1. Powder Preparation>

As a reactor, 832 g of N,N-dimethylacetamide (DMAc) was filled in a 1L reactor equipped with a stirrer, nitrogen injection device, dropping funnel, temperature controller and cooler while passing nitrogen, and then the temperature of the reactor was adjusted to 25℃. 64.046 g of bis trifluoromethyl benzidine (TFDB) was dissolved and the solution was maintained at 25°C. Here, 31.09 g of 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) and 8.83 g of biphenyl tetracarboxylic dianhydride (BPDA) were added and stirred for a certain period of time. was dissolved and reacted. At this time, the temperature of the solution was maintained at 25 °C. Then, 20.302 g of terephthaloyl chloride (TPC) was added to obtain a polyamic acid solution having a solid concentration of 13% by weight.

25.6 g of pyridine and 33.1 g of acetic anhydride were added to the polyamic acid solution, stirred for 30 minutes, stirred at 70° C. for 1 hour, cooled to room temperature, precipitated with 20 L of methanol, and the precipitated solid was filtered and pulverized Then, it was dried under vacuum at 100° C. for 6 hours to obtain 111 g of solid powder polyimide-amide.

<Example 1. Preparation of polyimide-based film>

100 g of polyamide-imide of the solid powder obtained in Preparation Example 1 was dissolved in 670 g of N,N-dimethylacetamide (DMAc) to obtain a 13wt% solution. The solution thus obtained was applied to a glass plate, cast to 385 μm, and dried with hot air at 120° C. for 20 minutes to obtain a gel film having a DMAc content of 14%.

To evaluate the product shrinkage, the shrinkage and expansion behavior of the gel film according to the curing temperature was measured under nitrogen at 10°C/min from room temperature to 350°C using a TMAQ400 of TA Instrument. At this time, the shrinkage rate of the gel film was obtained according to Equation 2 below, and the shrinkage rate at 280°C (maximum curing temperature) at room temperature was calculated to be 2%.

[Equation 2]

{(length before measurement - length after measurement)/length before measurement} x 100

The gel film was peeled off the glass plate and fixed to a tenter with adjustable length. At this time, the length of the tenter was 500x500mm (corresponding to the first size of the gel film), and it was stretched to 510x510mm (corresponding to the second size of the gel film) by increasing the length with the aforementioned shrinkage.

After that, it was cured at a rate of 2.7 °C/min from 120 °C to 280 °C for 60 minutes to obtain a film having a thickness of 50 µm. The film was cut to a size of 400 mm x 400 mm and physical properties were measured.

<Example 2>

100 g of polyamide-imide of the solid powder obtained in Preparation Example 1 was dissolved in 670 g of N,N-dimethylacetamide (DMAc) to obtain a 13wt% solution. The solution thus obtained was applied to a glass plate, cast to 615 μm, and dried with hot air at 120° C. for 20 minutes to obtain a gel film having a DMAc content of 14%.

The obtained gel film was peeled off the glass plate and fixed on a tenter with adjustable length. At this time, the length of the tenter was 500x500mm (corresponding to the first size of the gel film), and it was stretched to 510x510mm (corresponding to the second size of the gel film) by increasing the length by 2% as described above.

Thereafter, the film was cured at a rate of 2.7 °C/min from 120 °C to 280 °C for 60 minutes to obtain a film having a thickness of 80 µm. The film was cut to a size of 400 mm x 400 mm and physical properties were measured.

<Example 3>

A polyimide film was prepared in the same manner as in Example 1, but 0.05 g of a 30% silica dispersion having a methyl group bonded to the surface was added to 50 g of N,N-dimethylacetamide (DMAc), and the N,N-dimethylacetamide An amorphous silica particle dispersion (dispersion concentration: 0.1 wt%) was obtained by ultrasonication until thetaamide (DMAc) became transparent.

Then, the amorphous silica particle dispersion obtained above and 100 g of the polyimide solid content of Preparation Example 1 were filled with N,N-dimethylacetamide (DMAc) 620 g in 1L with a stirrer, a nitrogen injection device, a dropping funnel, a temperature controller and a cooler attached. A polyimide film was prepared in the same manner as in Example 1 (thickness of 50 μm) by dissolving the mixture (solid concentration of 13wt%) while passing nitrogen through the reactor and stirring. The film was cut to a size of 400 mm x 400 mm and physical properties were measured.

<Comparative Example 1>

A Gel Film was prepared in the same manner as in Example 1 to obtain a Gel film having a DMAc content of 14%.

The obtained gel film was peeled off the glass plate and fixed on a tenter with adjustable length. At this time, the length of the tenter was 500x500mm (corresponding to the first size of the gel film), and the above-mentioned additional stretching of the tenter was not reflected. After that, it was cured at a rate of 2.7 °C/min from 120 °C to 280 °C for 60 minutes to obtain a film having a thickness of 50 µm. The film was cut to a size of 400 mm x 400 mm and physical properties were measured.

<Comparative Example 2>

A Gel film having a DMAc content of 14% was obtained by preparing a Gel Film in the same manner as in Example 2.

The obtained gel film was peeled off the glass plate and fixed on a tenter with adjustable length. At this time, the length of the tenter was 500x500mm (corresponding to the first size of the gel film), and the above-mentioned additional stretching of the tenter was not reflected. Thereafter, the film was cured at a rate of 2.7 °C/min from 120 °C to 280 °C for 60 minutes to obtain a film having a thickness of 80 µm. The film was cut to a size of 400 mm x 400 mm and physical properties were measured.

<Comparative Example 3>

A gel film having a DMAc content of 14% was obtained by preparing a gel film in the same manner as in Example 2.

The obtained gel film was peeled off the glass plate and fixed on a tenter with adjustable length. At this time, the length of the tenter was 500x500mm (corresponding to the first size of the gel film), and it was 535x535mm (corresponding to the second size of the gel film) by reflecting 7% of the shrinkage rate exceeding the above-described tenter additional stretching. After that, the film was cured from 120°C to 280°C at a rate of 2.7°C/min for 60 minutes to obtain a film. The film was cut to a size of 400 mm x 400 mm and physical properties were measured.

Experimental Example 1

About the polyimide-based films prepared in Examples and Comparative Examples The physical properties of Table 1 below were measured, and the results are shown in Table 1.

(1) Measuring the thickness of the film

Using a Mitsutoyo Micrometer, the thickness of the polyimide-based film was measured.

(2) optical transmittance

For the polyimide-based films prepared in Examples and Comparative Examples, average optical transmittance was measured in a wavelength range of 380 to 780 nm using a UV spectrometer (Cotica Minolta CM-3700d). The thickness of the polyimide-based film is shown in Table 1.

(3) Yellowness (Yellow Index, Y.I.)

The yellowness of the polyimide-based film was measured according to ASTM E313 standard using a UV spectrometer (Cotica Minolta CM-3700d).

(4) Haze

It was measured three times using a hazemeter (Murakami Color Research Laboratory, HM-150), and the average value was measured.

division Thickness (㎛) excess chromaticity Izu Example 1 50.0±2.0 89.0 2.8 0.3 Example 2 80.0±2.0 88.7 4.4 0.3 Example 3 50.0±2.0 89.1 2.7 0.2 Comparative Example 1 50.0±2.0 89.0 2.8 0.3 Comparative Example 2 80.0±2.0 88.7 4.4 0.4 Comparative Example 3 50.0±4.0 88.6 3.2 0.3

Referring to Table 1, it was confirmed that the transmittance, yellowness, and haze of the films obtained in Examples and Comparative Examples were at similar levels.

Experimental Example 2

For the optical films prepared in Examples and Comparative Examples, the initial static electricity value and the peeling static electricity value were measured on the film surface, and the results are shown in Table 2.

(1) Initial static electricity measurement

The films prepared in Examples and Comparative Examples were rolled up in a roll form and stored for 120 hours, then the roll form was unwound by turning it twice. The static electricity value was measured under the condition of 25% relative humidity in a , and is shown in Table 2 as the initial static electricity measurement value (kV).

(2) Measurement of peeling static electricity

The films prepared in Examples and Comparative Examples were rolled up and stored for 120 hours, rotated twice and unpacked, and after 1 minute, at a location 25cm away from the 10 places where the initial static electricity of the item (2) was measured, the static electricity measuring device was The static electricity value was measured under the condition of 25% relative humidity at 25 °C using a peeling static electricity measurement value (kV), and it is shown in Table 2 below.

Category (10 measurements) Initial static measurement (kV) Peeling Electrostatic Measurement (kV) Example 1 4.5 / 4.5 / 3.8 /2.5 / 3.4 / 3.7 / 4.9 / 4.9 / 4.7 / 4.4 9.4 / 9.1 / 7.5 / 8.8 / 9.8 / 8.3 / 9.1 / 10.1 / 8.8 / 9.3 Example 2 4.8 / 4.1/ 4.6 / 3.5 / 4.1 / 3.6 / 3.9 / 4.2/ 4.4 / 4.9 10.2 / 8.3 / 10.1 / 9.5 / 9.6 / 8.4/ 8.7 / 8.9 / 9.1/ 9.0 Example 3 5.0 / 3.7 / 2.8 / 3.5 / 4.4 / 3.6 / 5.5 / 4.7 / 5.6 / 4.7 9.9 / 7.5 / 7.8 / 8.6 / 8.8 / 9.3 / 9.2 / 9.1 / 9.8 / 8.3 Comparative Example 1 7.3 / 3.3 / 3.9 / 5.2 / 5.7 / 6.0 / 3.0 / 4.2 / 5.4/ 5.4 13.7 / 13.6 / 13.6 / 17.1 / 16.8 / 17.6 / 14.3 / 12.5 / 14.4 / 14.9 Comparative Example 2 5.6 / 6.4 / 5.2 / 5.1 / 5.5 / 3.4 / 4.9 / 4.6/ 5.2 / 5.4 14.2 / 18.3 / 13.5 / 16.9 / 16.6 / 14.2 / 15.6 / 17.4 / 15.9 / 17.2 Comparative Example 3 5.5 / 3.0 / 2.9 / 2.7 / 4.2 / 4.9 / 5.7 / 6.0 / 5.5 / 4.4 10.1 / 8.9 / 7.8 / 8.4 / 9.3 / 7.5 / 7.9 / 9.4/ 9.2 / 9.3

Referring to Table 2, the initial static electricity value and peeling measured on the film surface of Examples 1 to 3 in which the shrinkage rate of the curing process is reflected in the tenter process to compensate for the size change in the curing process and the interference control ability of the thin film is controlled in advance. The static electricity value is the initial static electricity value measured on the film surface of Comparative Examples 1 and 2 in which the interference control ability of the thin film is not previously controlled by not reflecting the shrinkage rate of the curing process in the tenter process, or the film surface of Comparative Example 3 compensated for by excessive shrinkage and it was confirmed that there was a significant difference compared to the peeling static electricity value.

Experimental Example 3

The charging parameters were calculated according to Equation 1 below by averaging each measured value in Table 2, and the corresponding values are shown in Table 3 below.

(3) Calculation of charging parameters

[Equation 1]

In Equation 1, Sr and Sp are the average values of the initial static electricity measurement value (kV) and the peeling static electricity measurement value (kV) measured at room temperature and 25% relative humidity, respectively, D is the thickness of the optical film (mm), L is the width (mm) of the optical film.

In addition, T was applied to the value reflected in the above Examples and Comparative Examples as the shrinkage rate during the curing stage of the gel film measured during the manufacture of the optical film.

For reference, 0.05mm or 0.08mm was applied to D in Equation 1, and 400mm was applied to L.

division Sr Sp Charge parameter (calculated value of Equation 1) Example 1 4.13 9.02 0.0020 Example 2 4.21 9.18 0.0032 Example 3 4.35 8.83 0.0016 Comparative Example 1 4.94 14.85 0.0037 Comparative Example 2 5.13 15.98 0.0067 Comparative Example 3 4.48 8.78 0.00038

Referring to Table 3, the initial static electricity value and peeling measured on the film surface of Examples 1 to 3 in which the shrinkage rate of the curing process is reflected in the tenter process to compensate for the size change in the curing process and to control the interference control ability of the thin film in advance The electrification parameter value calculated from Equation 1 with static electricity value, thickness, and film length as variables is calculated on the film surface of Comparative Examples 1 and 2 in which the interference control ability of the thin film is not previously controlled by not reflecting the shrinkage rate of the curing process in the tenter process It was confirmed that there was a significant difference compared to the applied charging parameter values.

However, even in the case of Comparative Example 3, in which the tenter process was performed in excess of the degree of compensation for size change in the curing process, the charging parameter value itself showed an improved result compared to Comparative Examples 1 and 2, but extremely low values compared to Examples 1 to 3 was also confirmed to be inappropriate to control thin-film interference.

Experimental Example 4

The appearance quality of the surface of the optical films prepared in Examples and Comparative Examples was measured, and the results are shown in Table 4.

(4) Appearance quality evaluation

The results of visual observation before rolling the film into a roll form and the results of observation of the surface using a hexagon tube and a three-wavelength fluorescent lamp after rolling it into a roll form so that the inner diameter becomes 3 inches and leaving it to stand for 72 hours, respectively, are shown in Table 4, Fig. 1 to 4 are grouped together. Pressed marks were indicated as 1, dent marks were indicated as 2, and diagonal wrinkles were indicated as 3, and 0 was indicated if there were no defects.

division Appearance defects on the film surface (visual) Roll surface appearance defect (three wavelength fluorescent lamp) Example 1 0 0 Example 2 0 0 Example 3 0 0 Comparative Example 1 3/2/1 2/1 Comparative Example 2 2/1 3/1 Comparative Example 3 3 0

Referring to Table 4, the film appearance quality measured on the film surface of Examples 1 to 3 in which the shrinkage rate of the curing process is reflected in the tenter process to compensate for the size change in the curing process and the interference control ability of the thin film is controlled in advance is cured It was confirmed that the shrinkage rate of the process was not reflected in the tenter process to show a significant difference compared to the film appearance measured on the film surface of Comparative Examples 1 and 2 in which the interference control ability of the thin film was not previously controlled.

From this, it can be seen that the size change compensation of the curing process described above controls the interference control ability of the thin film in advance, and consequently affects the appearance defects of the film surface and the roll surface.

In addition, when the tenter process was performed exceeding the size change compensation degree of the curing process, as shown in Comparative Example 3, the thickness deviation was large and the film surface was wrinkled due to the imbalance of force during film forming, confirming the improper result of poor appearance did

Furthermore, FIG. 1 is a photograph obtained by visually observing the surface of a commercially available film product subjected to a winding treatment, and various defects in appearance quality can be identified.

In addition, FIG. 2 shows a photograph of visually observing defects on the surface of a roll obtained by winding a film product manufactured according to Examples and Comparative Examples, respectively. For reference, the left side view of FIG. 2 is an optical film prepared according to Example 1 of the present invention, and the right side view of FIG. 2 is an optical film prepared according to Comparative Example 1. Defects were identified in various parts in the right drawing compared to the left drawing in FIG. 2 .

In addition, the optical film on the right side of FIG. 2 was left in a roll form for 120 hours and then rotated twice to untie it, and then the appearance of the optical film was confirmed using a three-wavelength fluorescent lamp, as shown in FIG. 3 . According to FIG. 3 , as in FIG. 2 , various types of defects can be identified in various parts.

In addition, the film roll of Example 1 was allowed to stand for 120 hours and then peeled off, and a photograph showing defects using a three-wavelength fluorescent lamp is shown in FIG. 4 . In FIG. 4 , as in FIG. 2 , appearance defects such as indentations, dents, and oblique wrinkles were not confirmed.

From these results, thin film interference due to poor winding can be quantified as a charging parameter that has a correlation with the film shrinkage in the curing step, and the gel film shrinkage in the curing step during film production is reflected in advance in the tenter process and the film is stretched. It can be confirmed that it is possible to provide an optical film in which appearance quality defects such as diagonal wrinkles or indentation marks on the surface are resolved in a way that removes the thin film interference capability that may occur in the subsequent winding process in advance.

Features, structures, effects, etc. illustrated in each of the above-described embodiments may be combined or modified with respect to other embodiments by those of ordinary skill in the art to which the embodiments belong. Accordingly, the contents related to such combinations and modifications should be interpreted as being included in the scope of the present invention.

Claims (12)

As an optical film comprising a transparent polyimide-based resin,
After cutting the optical film to 400mm x 400mm x Dmm, the inner diameter from the center to the end of the optical film is 1 inch and stored in a roll form for 120 hours,
After loosening the roll shape twice, on the surface of the optical film,
Measure the initial static electricity value (kV) at 10 randomly selected sites for the optical film, and measure the peeling electrostatic value (kV) at 10 randomly selected sites on the surface within 1 minute, and calculate by Equation 1 below. An optical film with an applied charging parameter of 0.0005 to 0.0035.
[Equation 1]

(In Equation 1, Sr and Sp are the average values of the initial static electricity measurement value (kV) and the peeling static electricity measurement value (kV) measured at room temperature and 25% relative humidity, respectively, D is the thickness of the optical film (mm), L is the width (mm) of the optical film, T is the curing step shrinkage (%) of the gel film formed during the production of the optical film is calculated by the following formula (2).
[Equation 2]
{(length before measurement - length after measurement)/length before measurement} x 100
(In Equation 2, the length before measurement is the length (mm) of the gel film measured by TMA (room temperature), and the length after the measurement is the length (mm) of the gel film measured by TMA (280 degrees).) delete delete The method of claim 1,
The Sr is 4.5 or less, the Sp is 11.5 or less, and the D is 0.01 ~ 0.1mm optical film. The method of claim 1,
An optical film having a shrinkage ratio of 5% or less calculated by Equation 2 above. The method of claim 1,
An optical film with a total light transmittance of 88% or more. The method of claim 1,
Optical film in which the transparent polyimide-based resin is a polymer having a fluorine group 8. The method of claim 7,
An optical film in which the transparent polyimide-based resin includes a repeating unit derived from a bis(trifluoromethyl)benzidine derivative. As a method of manufacturing an optical film according to any one of claims 1 and 4 to 8,
A film forming step of casting a varnish containing a transparent polyimide-based resin into a film to provide a gel film of a first size; and
a tenter step of stretching the gel film to a second size by performing a tenter process;
A method of manufacturing an optical film comprising a; curing step of curing after performing the tenter step,
The tenter step is a method of manufacturing an optical film for compensating for shrinkage of the gel film in the curing step by making the gel film of the second size larger than the first size. 10. The method of claim 9,
The tenter step is a method of manufacturing an optical film to perform stretching by determining the second size by calculating in advance the shrinkage rate of the gel film in the curing step. 10. The method of claim 9,
After the curing step, the optical film is wound and then the quality determination step of inspecting the appearance of the film; further comprising,
In the quality determination step, the optical film is cut to 400mm x 400mm x Dmm so that the inner diameter from the center to the end of the optical film is 1 inch, stored in a roll form for 120 hours, and then unwound by turning the roll form twice Next, on the surface of the optical film, the initial electrostatic value (kV) was measured at 10 randomly selected sites for the optical film, and the peeling electrostatic value (kV) was measured at 10 randomly selected sites from the surface within 1 minute. A method of manufacturing an optical film to determine whether the value calculated by the following Equation 1 is 0.0005 to 0.0035 by performing it.
[Equation 1]

(In Equation 1, Sr and Sp are the average values of the initial static electricity measurement value (kV) and the peeling static electricity measurement value (kV) measured at room temperature and 25% relative humidity, respectively, D is the thickness of the optical film (mm), L is the width (mm) of the optical film, T is the curing step shrinkage (%) of the gel film formed during the production of the optical film is calculated by the following formula (2).
[Equation 2]
{(length before measurement - length after measurement)/length before measurement} x 100
(In Equation 2, the length before measurement is the length (mm) of the gel film measured by TMA (room temperature), and the length after the measurement is the length (mm) of the gel film measured by TMA (280 degrees).) As a film body comprising the optical film of any one of claims 1 and 4 to 8,
On one side or both sides of the optical film, a primer film, a hardness reinforcement film, a flexible film, a folding film, a flexural strength reinforcement film, a visibility improvement film, a barrier film, an antibacterial film, a water-repellent film, an anti-fingerprint film, an anti-reflection film and a film body comprising at least one selected from a film providing a smooth touch feeling.

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