TWI792404B - Transparent film, display apparatus comprising the same and method of measuring average two-dimensional dispersibility of filler - Google Patents

Abstract

Disclosed are a light-transmitting film including a light-transmitting matrix and a filler dispersed in the light-transmitting matrix, wherein the filler has an average two-dimensional dispersibility of 25% or more, and a display device including the light-transmitting film, and a method of measuring an average two-dimensional dispersibility of a filler.

Description

Light-transmitting film, display element containing it, and flat measuring filler Uniform Dimensional Dispersion Method

The disclosure relates to a light-transmitting film and a display element including the same, and in particular to a light-transmitting film with excellent filler dispersibility and a display element including the same.

Recently, in order to reduce the thickness and weight of the display element and increase the flexibility, it has been considered to use a light-transmitting film instead of glass as the cover window of the display element. In order for the light-transmitting film to be useful as a cover window of a display element, the light-transmitting film needs to have excellent optical properties as well as excellent physical properties such as hardness, abrasion resistance, and flexibility.

Transparent plastic films are being studied as light-transmitting films for cover windows of display components. For example, among transparent plastic films, polyimide films with high hardness are being studied as materials for cover windows of flexible display elements. The polyimide film is made of polyimide (polyimide, PI) resin. Polyimide (PI)-based resins have insolubility, chemical resistance, heat resistance, radiation resistance, and low-temperature characteristics, and are therefore used as automotive materials, aviation materials, spacecraft materials, insulating coatings, insulating films, protective films and the like.

Meanwhile, in order to impart desired physical properties to the light-transmitting film, fillers may be added to the light-transmitting film. The filler is preferably uniformly dispersed in the transparent film.

Therefore, the present disclosure is made in view of the above problems, and an object of the present disclosure is to provide a light-transmitting film comprising fillers uniformly dispersed in a light-transmitting matrix.

Another object of the present disclosure is to provide a method for measuring the average two-dimensional dispersibility of fillers dispersed in a light-transmitting matrix.

Another object of the present disclosure is to provide a light-transmitting film comprising a filler dispersed in a light-transmitting matrix with an average two-dimensional dispersion of 25% or greater.

Another object of the present disclosure is to provide a method for producing a light-transmitting film with excellent filler dispersibility.

According to the present disclosure, the above and other objects can be achieved by providing a light-transmitting film, the light-transmitting film comprising: a light-transmitting matrix; and a filler dispersed in the light-transmitting matrix, wherein the filler has 25% or An average two-dimensional dispersion of greater than 25%, wherein the average two-dimensional dispersion is calculated according to the following equation:

Wherein Dx is the ideal two-dimensional distance between the filler particles calculated according to the number of filler particles shown in the microscope image of the sample of the light-transmitting film and the area of the microscope image; Daj is the closest distance shown in the microscope image and N is the total number of filler particles in the microscope image.

The filler may have an average two-dimensional dispersibility of 25% to 55%.

The filler may include at least one of inorganic particles, organic particles and organic-inorganic hybrid particles.

The filler may include silicon dioxide (SiO ₂ ).

The filler may have an average particle diameter of 5 nm to 50 nm.

The filler may be present in an amount of 0.01% by weight to 20% by weight based on the total weight of the light-transmitting film.

The light transmissive film may have a yellowness index of 3.5 or less.

The light-transmitting film may have a haze of 2% or less.

The light-transmitting film may have a light transmittance of 88% or more.

The light-transmitting film may have a 2% yield strength of 110 megapascals or greater.

The light-transmitting film may have a Young's modulus of 4.5 GPa or greater.

The microscope image may be a transmission electron microscope (TEM) image taken at a magnification of 20,000×.

The sample can be obtained by cutting the light-transmitting film into a thickness of 120 nm in a direction parallel to the thickness direction. The filler can have 5nm to 80nm The average grain size of rice.

The microscope image may be a scanning electron microscope (SEM) image taken at a magnification of 3,000×.

The microscope image can be obtained by imaging a cross-section of the light-transmitting film parallel to the thickness direction. The filler may have an average particle diameter of 50 nm to 500 nm.

The light-transmitting matrix may include imide repeating units.

The light-transmitting matrix may comprise amide repeating units.

According to another aspect of the present disclosure, a display element is provided, and the display element includes: a display panel; and a light-transmitting film disposed on the display panel.

According to yet another aspect of the present disclosure, there is provided a method of measuring the average two-dimensional dispersion of fillers, the method comprising: producing a sample of a light-transmitting film containing fillers; obtaining a microscope image of the sample; preprocessing the image to obtain a processed image; obtaining coordinate data about the location of filler particles from the processed image; using the coordinate data to determine the number of the filler particles; using the number of the filler particles and calculating an ideal two-dimensional distance between the filler particles from the area of the microscope image; and calculating the distance between the filler particles using the coordinate data.

According to an embodiment of the present disclosure, the average two-dimensional dispersibility of the filler contained in the light-transmitting film can be calculated arithmetically, and thus the dispersion state of the filler can be evaluated in an easily understandable manner.

According to the embodiments of the present disclosure, a light-transmitting film having excellent filler dispersibility can be produced, and thus a light-transmitting film having excellent filler dispersibility can be easily selected.

The light-transmitting film according to the embodiments of the present disclosure can exhibit excellent haze characteristics, Young's modulus and yield strength due to its excellent filler dispersibility.

The light-transmitting film according to the embodiments of the present disclosure can be used as a cover window of a display device due to its excellent optical and mechanical properties.

100: Light-transmitting film/polyimide film

110: Light-transmitting matrix/polyimide-based matrix/matrix

120: filler/filler particles

200: display components

210: molding

250: Knife

310, 410: samples

501: display panel

510: base

520: semiconductor layer

530: gate electrode

535: gate insulation layer

541: source electrode

542: Drain electrode

551: interlayer insulating layer

552: Planarization layer

570: Organic Light Emitting Components

571: first electrode

572: Organic light-emitting layer

573: second electrode

580: embankment layer

590: film encapsulation layer

a, b: length

P: part

TFT: thin film transistor

t1, t2: Thickness

X, Y: axis

By reading the following detailed description in conjunction with the accompanying drawings, the above and other purposes, features and other advantages of the present disclosure will be more clearly understood. In the accompanying drawings: FIG. 1 is a schematic diagram showing a light-transmitting film according to an embodiment of the present disclosure; Fig. 2 is a schematic diagram showing the steps of processing microscope images; Fig. 3 is a schematic diagram showing a method for calculating an ideal two-dimensional distance Dx between filler particles; Fig. 4 is a diagram showing the distribution of distances between filler particles Graph; FIG. 5 is a cross-sectional view showing a part of a display element according to another embodiment of the present disclosure; FIG. 6 is an enlarged cross-sectional view showing a portion "P" of FIG. 5; A schematic perspective view of cutting the light-transmitting film in the direction of t1) direction; FIG. 7 b is a perspective view showing a sample of a light-transmitting film according to an embodiment of the present disclosure and a method for imaging the film; and FIG. 8 is a perspective view illustrating a method of imaging a light-transmitting film according to another embodiment.

Hereinafter, embodiments of the present disclosure will be explained in detail with reference to the accompanying drawings. However, the following examples are provided only for illustration to clearly understand the present disclosure, and do not limit the scope of the present disclosure.

The shapes, sizes, ratios, angles and numbers disclosed in the drawings for illustrating the embodiments of the present disclosure are exemplary only, and the present disclosure is not limited to the details shown. Throughout this specification, the same reference numbers refer to the same parts. In the following description, when it is judged that a detailed description of a related well-known function or configuration unnecessarily obscures the subject matter of the present disclosure, the detailed description will be omitted.

Where a term such as "comprises", "has" or "comprises" is used in this specification, another part may also be present, unless the expression "only" is used. Terms in the singular may include the plural unless the context dictates otherwise. Furthermore, when explaining a component, the component should be construed as including a range of error even if there is no explicit description thereof.

In the description of positional relationship, for example, when a positional relationship is stated as "on", "above", "below" or "near", this may include the absence of contact between them, unless the use of " Exactly (just)" or "directly".

Spatially relative terms such as "below", "under", "lower", "above" and "upper" may be used herein to describe the relationship of an element or component to another element or component as shown in the figures. . It should be understood that in addition to the orientation depicted in the figure, empty Relative terms are also intended to encompass different orientations of elements during use or operation of the elements. For example, if an element in one of the figures is turned upside down, elements described as "below" or "beneath" the other elements would then be oriented "above" the other elements. Thus, the exemplary terms "below" or "under" can encompass both "below" and "above". Likewise, the exemplary terms "above" or "upper" can encompass both "above" and "below".

In stating temporal relationships, for example, when chronological order is stated using "after", "after", "next" or "before", discontinuities may be included unless "exactly" or "directly" are used the situation of the relationship.

It should be understood that although the terms "first", "second", etc. may be used herein to describe various components, these components should not be limited by these terms. These terms are only used to distinguish one component from another. Therefore, the first component may be referred to as the second component within the technical idea of the present disclosure.

It should be understood that the term "at least one" includes all combinations associated with any one item. For example, "at least one of the first component, the second component, and the third component" may include two or more components selected from the first component, the second component, and the third component, and the first component , all combinations of each of the second and third components.

Those skilled in the art will easily understand that the features of various embodiments of the present disclosure may be partially or completely coupled or combined with each other, and may interoperate with each other and be technically driven in different ways. Embodiments of the present disclosure may be implemented independently of each other, or may be implemented together in an interrelated manner.

FIG. 1 is a schematic diagram illustrating a light-transmitting film 100 according to an embodiment of the present disclosure.

The transparent film 100 according to an embodiment of the present disclosure includes a transparent matrix 110 and a filler 120 dispersed in the transparent matrix.

According to an embodiment of the present disclosure, the light-transmitting substrate 110 is light-transmitting. In addition, the light-transmitting substrate 110 may be flexible. For example, the light-transmitting substrate 110 can be bendable, foldable and rollable.

The light-transmitting matrix 110 includes light-transmitting resin. The light-transmitting matrix 110 may include, for example, imide repeating units. In addition, the light-transmitting matrix 110 may include, for example, amide repeating units.

The light-transmitting matrix 110 according to an embodiment of the present disclosure can be prepared from monomer components including, for example, dianhydride and diamine. More specifically, the light-transmitting matrix 110 according to an embodiment of the present disclosure may have imide repeating units formed from dianhydride and diamine. In addition, the light-transmitting matrix 110 according to an embodiment of the present disclosure may have an amide repeating unit formed from a dicarbonyl compound and a diamine.

The light-transmitting matrix 110 according to an embodiment of the present disclosure can be prepared from monomer components including dianhydrides, diamines and dicarbonyl compounds. Therefore, the light-transmitting matrix 110 according to an embodiment of the present disclosure may have an amide repeating unit and an amide repeating unit. The light-transmitting matrix 110 having imide repeating units and amide repeating units can be, for example, polyamide-imide resin.

The light-transmitting substrate 110 according to an embodiment of the present disclosure may include polyimide resin or polyamide-imide resin. According to an embodiment of the present disclosure, a resin including imide repeating units is called a polyimide-based resin. Polyimide-based resins include polyimide resins and polyamide-imide resins.

According to an embodiment of the present disclosure, the polyimide-based resin used for the light-transmitting matrix 110 may have excellent mechanical properties and optical properties.

The light-transmitting matrix 110 may have a thickness sufficient for the light-transmitting film 100 to protect the display panel. For example, the transparent substrate 110 may have a thickness of 10 microns to 100 microns. The thickness of the transparent matrix 110 may be the same as the thickness t1 of the transparent film 100 . The light-transmitting film 100 may have a thickness t1 of 10 micrometers to 100 micrometers.

The light-transmitting film 100 according to an embodiment of the present disclosure includes, for example, a polyimide-based film using a polyimide-based resin as the light-transmitting matrix 110 . Polyimide-based films include polyimide films and polyamide-imide films.

The filler 120 can be an inorganic material or an organic material. The filler 120 may have a particle shape. According to an embodiment of the present disclosure, the filler 120 may include at least one of inorganic particles, organic particles, or organic-inorganic hybrid particles.

According to an embodiment of the present disclosure, the filler 120 may include silicon dioxide (SiO ₂ ). For example, inorganic silicon dioxide (SiO ₂ ) particles can be used as the filler 120 .

According to an embodiment of the present disclosure, at least a portion of silicon dioxide (SiO ₂ ) used as the filler 120 may be surface-treated. More specifically, surface-treated silicon dioxide (SiO ₂ ) particles may be used as the filler 120 . According to an embodiment of the present disclosure, at least a part of the silicon dioxide (SiO ₂ ) used as the filler 120 may be surface-treated with an organic compound having an alkoxy group. According to embodiments of the present disclosure, silica particles are used regardless of the surface treatment; in other words, silica particles are intended to include non-surface-treated silica particles as well as surface-treated silica particles.

For example, silicon dioxide (SiO ₂ ) particles surface-treated with at least one of substituted or unsubstituted alkylalkoxysilanes or phenylalkoxysilanes may be used as the filler 120 .

Specifically, silicon dioxide (SiO ₂ ) particles surface-treated with methylalkoxysilane, ethylalkoxysilane, or phenylalkoxysilane may be used as the filler 120 . According to an embodiment of the present disclosure, for example, silicon dioxide (SiO ₂ ) particles surface-treated with trimethoxy(methyl)silane and phenyltrimethoxysilane can be used as the filler 120 .

According to an embodiment of the present disclosure, the filler 120 may have a unit structure represented by the following formulas 1 to 6:

[Formula 3]

[Formula 6]

wherein each R is independently an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, or a benzene having 6 to 18 carbon atoms at least one of the bases.

In the light-transmitting film 100 according to an embodiment of the present disclosure, the filler 120 dispersed in the light-transmitting matrix 110 has an average two-dimensional dispersion of 25% or greater.

The average two-dimensional dispersibility of the filler 120 is calculated using Equation 1 below.

where Dx is the ideal two-dimensional distance between filler particles, and Daj is the measured two-dimensional distance between adjacent filler particles.

Specifically, in Equation 1, Dx is the ideal two-dimensional distance between filler particles calculated from the number of filler particles shown in the microscope image of the sample of the light-transmitting film and the area of the microscope image, and Daj is the ideal two-dimensional distance between the filler particles in the microscope image. The measured two-dimensional distance between the nearest filler particles is shown, and N is the total number of filler particles in the microscope image.

The microscope image is a microscope image of a sample 310 of the light transmissive film 100 . through A sample 310 of the optical film 100 can be produced by cutting the optically transparent film 100 into a thickness t2 of 120 nm in a direction parallel to the thickness t1 (see FIGS. 7a and 7b ).

According to an embodiment of the present disclosure, the microscope image may be a transmission electron microscope (TEM) image taken at a magnification of 20,00Ox.

In the light-transmitting film 100 according to an embodiment of the present disclosure, the fillers 120 dispersed in the light-transmitting matrix 110 may have a ratio of 25% or more calculated using a transmission electron microscope (TEM) image taken at a magnification of 20,000x. Average two-dimensional dispersion.

The distance between filler particles 120 can be obtained according to the following method.

Fig. 7a is a schematic perspective view showing cutting of the light-transmitting film in a direction parallel to the thickness (t1) direction of the light-transmitting film. 7b is a perspective view showing a sample of a light-transmitting film and a method of imaging the film according to one embodiment of the present disclosure.

First, in order to obtain a microscope image, a sample 310 of the light-transmitting film 100 is produced. Referring to FIG. 7 a , the light-transmitting film 100 may be covered using a molding 210 . For example, the light-transmitting film 100 can be fixed by a molding 210 including epoxy resin.

As shown in FIG. 7 a , the light-transmitting film 100 is cut using a knife 250 . Specifically, the light-transmitting film 100 fixed by the molding 210 is cut to produce a sample 310 .

According to an embodiment of the present disclosure, the sample 310 of the light-transmitting film 100 can be produced by cutting the light-transmitting film 100 into a thickness t2 of 120 nm in a direction parallel to the thickness t1 direction. In FIG. 7a and FIG. 7b, the thickness direction of the transparent film 100 is the direction of t1, and the thickness direction of the sample 310 is the direction of t2.

Microscopic imaging was performed on the sample 310 shown in Figure 7b. Microscopic imaging was performed on a portion of the light transmissive film 100 from the top to the bottom of the image shown in FIG. 7b. more In general, a sample 310 of light transmissive film 100 can be imaged in the direction indicated by "PIC" in FIG. 7b.

Fig. 2 is a schematic diagram illustrating the steps of processing a microscope image.

By using microscope imaging, a microscope image of the light-transmitting film 100 as shown in FIG. 2A can be obtained. A microscope image can be generated by imaging the light transmissive film 100 including the filler 120 using a microscope. For example, the microscope used herein may be an optical microscope or a transmission electron microscope (TEM).

According to an embodiment of the present disclosure, the transmission electron microscope (TEM) used herein is JEM-2100F manufactured by JEOL. Microscopic images are obtained by performing imaging according to methods using known microscopes.

FIG. 2A is a transmission electron microscope (TEM) image taken at a magnification of 20,000x (20K) of the light-transmitting film 100 according to an embodiment of the present disclosure.

Next, the microscope images were preprocessed to generate the processed images shown in Figure 2(B). In the step of preprocessing the microscope image, the filler 120 can be clearly distinguished from the parts other than the filler 120 , so the distinction of the filler 120 can be improved. For example, a microscope image can be converted into a monochrome image or a two-color image by color separation. According to an embodiment of the present disclosure, the microscope image can be converted into a black and white image by preprocessing the microscope image.

FIG. 2B is a black and white image converted from a transmission electron microscope (TEM) image of the light transmissive film 100 .

Next, the coordinate data of the positions of the particles of filler 120 are extracted from the processed image.

Specifically, the filler particles 120 are isolated from the processed image in order to extract coordinate information about the location of the filler particles 120 . Therefore, only points corresponding to particles of filler 120 in the image of FIG. 2B are left in the image of FIG. 2C . Here, points with too small a diameter are excluded from the points in the image. For example, points that are measured to have a diameter less than 1/10 of the average diameter of the filler 120 particles are excluded from the image. Thus, the image of Fig. 2C is obtained. In an embodiment of the present disclosure, the image shown in FIG. 2C is called a "rendered image".

The rendered image is analyzed using an image analysis program to extract the coordinates of the particles of the filler 120 . In this case, the point-based coordinates are referred to as "coordinates of the filler 120".

According to an embodiment of the present disclosure, the coordinates of the particles of the filler 120 can be obtained by iTEM using iTEM5.1 produced by Olympus as an image analysis program.

When the coordinates of the particles of the filler 120 are obtained, the number of filler particles included in an image can be obtained.

According to an embodiment of the present disclosure, the method shown in FIG. 3 can be used to calculate Dx, which is an ideal two-dimensional distance between particles of the filler 120 .

According to an embodiment of the present disclosure, in order to calculate Dx (Dx is the ideal two-dimensional distance between particles of filler 120), as shown in FIG. corresponding vertices of a long equilateral triangle. The length of each side of the equilateral triangle shown in FIG. 3 is determined by the number of particles of the filler 120 and the size of the rendered image.

Fig. 3 is a schematic diagram showing a method of calculating an ideal two-dimensional distance Dx between filler particles.

Referring to FIG. 3 , one side of the equilateral triangle is set parallel to the X-axis direction.

In FIG. 3 , the length of the rendered image in the X-axis direction is represented by "a", the length in the Y-axis direction is represented by "b", and the number of particles of the filler 120 arranged in a row in the X-axis direction is represented by " Nx" represents the number of particles of the filler 120 arranged in a row in the Y-axis direction by "Ny", and the length of one side of an equilateral triangle is represented by "Dx" as an ideal two-dimensional distance between filler particles. When the total number of filler particles is N, the following relationship is satisfied.

N=Nx×Ny

a=(Nx-1)×Dx

b=(Ny-1)×Dx×cos 30°

Area of rendered image = a×b

N, a, and b are obtained from the analysis of the rendered image, and Dx is obtained from N, a, and b.

In addition, the distance Daj between the particles of the filler 120 can be measured by the iTEM program using the actual coordinates of the particles of the filler 120 obtained by the image analysis program. Here, the measured distance Daj is the measured two-dimensional distance between adjacent particles of the filler 120 shown in the rendered image.

The distance between particles of filler 120 may be greater than Dx or smaller than Dx, which is the ideal two-dimensional distance between filler particles.

Fig. 4 is a graph showing the distribution of distances between filler particles. specific and 4 is a graph showing the relationship between the number of filler particles of the filler 120 dispersed in the light-transmitting film 100 and the measured two-dimensional distance Daj between adjacent particles according to an embodiment of the present disclosure.

It can be seen from FIG. 4 that the particles of the filler 120 are not dispersed at a predetermined distance, but are dispersed at different distances.

The average two-dimensional dispersibility of the filler 120 was determined by calculation according to Equation 1 using the values of Dx, Dy, and N thus obtained.

According to an embodiment of the present disclosure, the microscope image is a scanning electron microscope (SEM) image taken at a magnification of 3,000x, and the average two-dimensional dispersion can be calculated from the scanning electron microscope (SEM) image taken at a magnification of 3,000x . When using a scanning electron microscope (SEM) at a magnification of 3,000×, an image taken on a cross-section of the light-transmitting film 100 parallel to the thickness t1 direction of the light-transmitting film 100 ( FIG. 8 ) can be used.

FIG. 8 is a perspective view illustrating another embodiment of a method of imaging the light-transmitting film 100 . Referring to FIG. 8 , the light-transmitting film 100 may be covered with a molding 210 . For example, the light-transmitting film 100 can be fixed by the molding 210 including epoxy resin.

Referring to FIG. 8 , the light-transmitting film 100 covered with the molding 210 is cut in a direction parallel to the thickness t1 direction to produce a sample of the light-transmitting film 100 having an exposed cross-section in the thickness t1 direction. Scanning electron microscope (SEM) imaging was performed on a cross section in the thickness t1 direction of the sample 410 shown in FIG. 8 . Specifically, a sample 410 of light transmissive film 100 can be imaged in the direction indicated by "PIC" in FIG. 8 .

Using a scanning electron microscope (SEM) at a magnification of 3,000x The average two-dimensional dispersion was calculated from the images taken in the same manner as the average two-dimensional dispersion calculated using a transmission electron microscope (TEM) image taken at a magnification of 20,000x.

According to an embodiment of the present disclosure, the transmission electron microscope (TEM) may be a field-emission scanning electron microscope (FE-SEM). The field emission scanning electron microscope (FE-SEM) used herein may be, for example, JEM-2100F produced by JEOL. Microscopic images can be obtained by performing imaging according to methods using known microscopes.

According to an embodiment of the present disclosure, the fillers 120 dispersed in the light-transmitting matrix 110 of the light-transmitting film 100 may have a value of 25% or more calculated using a scanning electron microscope (SEM) image taken at a magnification of 3,000×. Average two-dimensional dispersion.

According to an embodiment of the present disclosure, the average two-dimensional dispersion can be calculated using images taken by an optical microscope. The optical microscope may be DSX510 manufactured by Olympus Group.

According to an embodiment of the present disclosure, when the filler 120 dispersed in the light-transmitting matrix 110 has an average two-dimensional dispersibility of 25% or more, the filler 120 is uniformly dispersed in the light-transmitting film 100, and thus can impart a transparent Excellent optical properties of optical film. In addition, when the filler 120 for improving mechanical properties is dispersed in the light-transmitting matrix 110 with an average two-dimensional dispersion of 25% or more, the effect of improving the mechanical properties of the light-transmitting film 100 may be maximized.

According to an embodiment of the present disclosure, the filler 120 may have an average two-dimensional dispersion of 25% to 55%. More specifically, filler 120 may have an average of 25% to 50% Two-dimensional dispersion. The filler 120 may have an average two-dimensional dispersibility of 30% to 45%.

According to embodiments of the present disclosure, there is no particular limitation on the size or content of the filler 120 . According to an embodiment of the present disclosure, the size and content of the filler 120 can be adjusted in consideration of the optical properties and mechanical properties of the light-transmitting film 100 .

According to an embodiment of the present disclosure, the filler 120 may have an average particle diameter of 5 nm to 500 nm.

When the average particle diameter of the filler 120 is less than 5 nm, the dispersibility of the filler 120 may be deteriorated, and particles of the filler 120 may aggregate. On the other hand, when the average particle diameter of the filler 120 is greater than 500 nm, the optical properties of the light-transmitting film 100 containing the filler 120 may be degraded. For example, when the filler 120 with an average particle size greater than 500 nm is excessively included, the haze of the light-transmitting film 100 may increase.

In addition, when the average particle diameter of the filler 120 is less than 5 nm, due to the aggregation of the filler 120, the mechanical strength of the light-transmitting film 100 deteriorates in the portion where the filler 120 aggregates, and the Young's modulus and 2 of the light-transmitting film 100 The % yield strength may deteriorate. When the average particle diameter of the filler 120 is greater than 500 nm, the yield strength of the light-transmitting film 100 may decrease, and its mechanical strength may deteriorate.

According to another embodiment of the present disclosure, the filler 120 may have an average particle diameter of 5 nm to 200 nm, may have an average particle diameter of 5 nm to 100 nm, or may have an average particle diameter of 5 nm to 80 nm. The average particle size. According to another embodiment of the present disclosure, the filler 120 may have an average particle diameter of 5 nm to 200 nm, or may have an average particle diameter of 10 nm to 20 nm.

According to an embodiment of the present disclosure, when using a transmission electron microscope When calculating the average two-dimensional dispersion from images taken by (TEM), considering the magnification of the transmission electron microscope (TEM), the filler 120 may have an average particle size of 5 nm to 80 nm. For example, the average two-dimensional dispersion of the light-transmissive film 100 comprising fillers 120 with an average particle size of 5 nm to 80 nm can be calculated using a transmission electron microscope (TEM) image taken at a magnification of 20,000x .

According to another embodiment of the present disclosure, when the average two-dimensional dispersion is calculated using an image taken by a scanning electron microscope (SEM), the filler 120 may have a thickness of 50 nm to 500 nm in consideration of the magnification of the scanning electron microscope (SEM). nanometer average particle size. For example, the average two-dimensional dispersion of the light-transmissive film 100 comprising fillers 120 with an average particle size of 50 nm to 500 nm can be calculated using scanning electron microscope (SEM) images taken at a magnification of 30,000x .

When the transparent film 100 includes the filler 120 , the optical and mechanical properties of the transparent film 100 can be improved by the light scattering of the filler 120 .

According to an embodiment of the present disclosure, based on the total weight of the light-transmitting film 100 , the content of the filler 120 may be within a range of 0.01 wt % to 20 wt %.

When the content of the filler 120 is less than 0.01% by weight based on the total weight of the light-transmitting film 100 , the light-scattering effect based on the filler 120 is insufficient, and the light transmittance or 2% yield strength of the light-transmitting film 100 is hardly improved.

On the other hand, when the content of the filler 120 is higher than 20% by weight based on the total weight of the light-transmitting film 100, the dispersibility of the filler 120 and the haze of the light-transmitting film 100 may deteriorate, and the excess filler 120 blocks light, And thus the light transmittance of the light-transmissive film 100 may be degraded.

According to an embodiment of the present disclosure, based on the total weight of the light-transmitting film 100 , the content of the filler 120 may be in a range of 0.01 wt % to 10 wt % or 0.01 wt % to 5 wt %. Alternatively, based on the total weight of the light-transmitting film 100 , the content of the filler 120 may be in a range of 0.5 wt % to 2 wt % or 0.5 wt % to 1 wt %.

In the case that the light-transmitting film 100 includes fillers 120, when the fillers 120 are not dispersed uniformly therein, the optical properties of the light-transmitting film 100 may deteriorate; for example, the optical transmittance of the light-transmitting film 100 may deteriorate, and the light transmission The haze of the film 100 may increase. However, according to an embodiment of the present disclosure, by adjusting the average two-dimensional dispersion of the filler in the light-transmitting matrix 110 to 25% or more, the haze of the light-transmitting film 100 can be prevented from increasing and its light transmittance can be reduced. .

According to an embodiment of the present disclosure, the light-transmitting film 100 may have a light transmittance of 88% or greater. More specifically, the light-transmitting film 100 according to an embodiment of the present disclosure may have a light transmittance of 89% or greater than 89%, or 90% or greater than 90%.

According to an embodiment of the present disclosure, the light-transmitting film 100 may have a yellowness index of 3.5 or less. More specifically, according to an embodiment of the present disclosure, the light-transmitting film 100 may have a yellowness index of 3.0 or less.

In addition, according to an embodiment of the present disclosure, the light-transmitting film 100 may have a haze of 2% or less. More specifically, the light-transmitting film 100 according to an embodiment of the present disclosure may have a haze of 1% or less, or 0.5% or less. According to an embodiment of the present disclosure, by adjusting the average two-dimensional dispersion of the filler in the light-transmitting matrix 110 to 25% or greater than 25%, the light-transmitting film 100 can be endowed with a Young's modulus of 4.5 GPa or greater than 4.5 GPa The 2% yield strength of 110 million Pa or greater than 110 million Pa.

The light-transmitting film 100 according to an embodiment of the present disclosure may have a 2% yield strength of 110 MPa or greater. More specifically, the light-transmitting film 100 according to an embodiment of the present disclosure may have a 2% yield strength of 120 megapascals or greater than 120 megapascals or a 2% yield strength of 125 megapascals or greater. .

In addition, the light-transmitting film 100 according to an embodiment of the present disclosure may have a Young's modulus of 4.5 GPa or greater than 4.5 GPa. More specifically, the light-transmitting film 100 according to an embodiment of the present disclosure may have a Young's modulus of 4.8 GPa or greater than 4.8 GPa.

FIG. 5 is a cross-sectional view illustrating a part of a display element 200 according to another embodiment, and FIG. 6 is an enlarged cross-sectional view of a portion 'P' in FIG. 5 .

Referring to FIG. 5 , a display element 200 according to another embodiment of the present disclosure includes a display panel 501 and a polyimide film 100 on the display panel 501 .

5 and 6, the display panel 501 includes a substrate 510, a thin film transistor TFT on the substrate 510, and an organic light emitting element 570 connected to the thin film transistor TFT. The organic light emitting element 570 includes a first electrode 571 , an organic light emitting layer 572 on the first electrode 571 and a second electrode 573 on the organic light emitting layer 572 . The display element 200 shown in FIGS. 5 and 6 is an organic light emitting display element.

The base 510 can be formed of glass or plastic. Specifically, the base 510 may be formed of plastic (such as polyimide resin or polyimide film). Although not shown, a buffer layer may be disposed on the substrate 510 .

The thin film transistor TFT is disposed on the substrate 510 . The thin film transistor TFT includes a semiconductor layer 520, is insulated from the semiconductor layer 520 and is connected to at least A portion of the overlapping gate electrode 530 , a source electrode 541 connected to the semiconductor layer 520 , and a drain electrode 542 spaced apart from the source electrode 541 and connected to the semiconductor layer 520 .

Referring to FIG. 6 , a gate insulating layer 535 is disposed between the gate electrode 530 and the semiconductor layer 520 . An interlayer insulating layer 551 may be disposed on the gate electrode 530 , and a source electrode 541 and a drain electrode 542 may be disposed on the interlayer insulating layer 551 .

A planarization layer 552 is provided on the thin film transistor TFT to planarize the top of the thin film transistor TFT.

The first electrode 571 is disposed on the planarization layer 552 . The first electrode 571 is connected to the thin film transistor TFT through a contact hole disposed in the planarization layer 552 .

A bank layer 580 is provided in a part of the first electrode 571 on the planarization layer 552 to define a pixel area or a light emitting area. For example, the bank layer 580 is arranged in the form of a matrix at the boundary between a plurality of pixels to define corresponding pixel regions.

The organic light emitting layer 572 is disposed on the first electrode 571 . The organic light emitting layer 572 can also be disposed on the bank layer 580 . The organic light emitting layer 572 may include one light emitting layer or two light emitting layers stacked in a vertical direction. Light having any one of red, green, and blue colors may be emitted from the organic light emitting layer 572 , and white light may be emitted from the organic light emitting layer 572 .

The second electrode 573 is disposed on the organic light emitting layer 572 .

The first electrode 571 , the organic light emitting layer 572 and the second electrode 573 can be stacked to form the organic light emitting element 570 .

Although not shown, when the organic light emitting layer 572 emits white light, each A pixel may include a color filter for filtering white light emitted from the organic light emitting layer 572 based on a specific wavelength. A color filter is formed in the light path.

A thin film encapsulation layer 590 may be disposed on the second electrode 573 . The thin film encapsulation layer 590 may include at least one organic layer and at least one inorganic layer, and the at least one organic layer and the at least one inorganic layer may be arranged alternately.

The polyimide film 100 is disposed on the display panel 501 having the above stacked structure. The polyimide film 100 includes a polyimide matrix 110 and a filler 120 dispersed in the polyimide matrix 110 .

The light-transmitting film 100 according to an embodiment of the present disclosure can be produced by a hybrid mixing method using a combination of solution-solution mixing and solution-powder mixing.

Hereinafter, a method of producing the light-transmitting film 100 according to an embodiment of the present disclosure will be explained. For convenience of description, a method of producing the light-transmitting film 100 will be explained with reference to an embodiment in which the light-transmitting film 100 is a polyimide-based film.

According to an embodiment of the present disclosure, the method for producing the light-transmitting film 100 includes: preparing light-transmitting resin powder; dissolving a first amount of light-transmitting resin powder in a first solvent to prepare a light-transmitting resin solution; solvent to prepare a filler dispersion; mix the filler dispersion with a light-transmitting resin solution to prepare a first mixed solution; and add a second amount of light-transmitting resin powder to the first mixed solution, followed by dissolution to prepare a second mixed solution solution. According to an embodiment of the present disclosure, as the light-transmitting resin, for example, a polyimide-based resin can be used. A filler dispersion can be prepared by adding the filler to a second solvent followed by stirring.

According to an embodiment of the present disclosure, the light-transmitting resin powder is divided into at least two equal parts, and mixed with the filler dispersion.

Specifically, a first amount of light-transmitting resin powder is dissolved in a first solvent, and mixed with the filler dispersion in the form of a light-transmitting resin solution. The first amount of light-transmitting resin powder may be 0.5% to 10% based on the weight of the filler. More specifically, based on the total weight of the filler 120 , the first amount of light-transmitting resin powder may range from 1% to 10%.

In addition, the second amount of light-transmitting resin powder is added in powder form. Specifically, the second amount of light-transmitting resin powder may be added in powder form to the first mixed solution prepared by mixing the filler dispersion with the light-transmitting resin solution.

The second amount of light-transmitting resin powder may correspond to an amount remaining after removing the first amount from the total amount of light-transmitting resin powder used to produce the light-transmitting film 100 . For example, the second amount can be at least 5 times, 10 times or 50 times the first amount. According to another embodiment of the present disclosure, the second amount of light-transmitting resin powder may be at least 100 times the first amount.

According to an embodiment of the present disclosure, before adding the second amount of light-transmitting resin powder to the first mixed solution, the method may further include adding a third solvent to the first mixed solution. The third solvent may be the same as or different from the first solvent. In an embodiment of the present disclosure, the third solvent may be the same as the first solvent.

N,N-Dimethylacetamide (DMAc) can be used as the first solvent. N,N-Dimethylacetamide (DMAc) or methyl ethyl ketone (MEK) can be used as the second solvent. N,N-Dimethylacetamide (DMAc) can be used as the third solvent. However, the facts of this disclosure The embodiment is not limited thereto, and other known solvents may be used as the first solvent, the second solvent, and the third solvent.

According to an embodiment of the present disclosure, first, a part (first amount) of the light-transmitting resin powder is dissolved in a solvent and then mixed with the filler dispersion. Therefore, the dispersibility of the filler is improved.

When the light-transmitting resin powder is directly injected into the filler dispersion in which the filler is dispersed, the solvent immediately penetrates from the powder surface to the inside of the powder, and at this time, the concentration around the powder surface immediately increases, whereby filler particles may aggregate.

On the other hand, according to an embodiment of the present disclosure, by first adding a light-transmitting resin solution prepared by dissolving light-transmitting resin powder to a filler dispersion containing a solvent, the polymer of the light-transmitting resin dispersed between the filler particles Chains prevent aggregation of filler particles. Then, even if the second amount of light-transmitting resin powder is also added, aggregation of the filler particles does not occur. Therefore, aggregation of the filler can be prevented, and dispersibility of the filler can be improved.

According to an embodiment of the present disclosure, the light-transmitting film 100 including the filler 120 uniformly dispersed therein may use a hybrid mixing method in which solution-solution mixing and solution-powder mixing are combined.

According to the embodiments of the present disclosure, a high degree of freedom of the filler 120 and the light-transmitting resin can be maintained, thereby creating a favorable environment for dispersion. Therefore, the filler 120 can be bonded to the light-transmitting resin with a high degree of freedom, and the filler 120 can be uniformly dispersed in the matrix 110 formed of the light-transmitting resin.

According to an embodiment of the present disclosure, silica particles may be used as the filler 120 .

The dispersion of filler 120 may be a silica dispersion. A silica dispersion can be prepared by, for example, injecting dimethylacetamide (DMAc) and silica particles into a reactor followed by stirring.

Hereinafter, the present disclosure will be explained in more detail with reference to Preparations and Examples. However, the preparations and examples should not be construed as limiting the scope of the present disclosure.

<Preparation Example 1: Preparation of Light-Transmitting Polymer Solid>

Charge 776.655 grams of N,N-dimethylacetamide (DMAc) into a 1-liter reactor equipped with a stirrer, nitrogen injector, dropping funnel, temperature controller, and cooler while passing nitrogen through the reactor . Then the temperature of the reactor was adjusted to 25°C, 54.439 grams (0.17 moles) of 2,2'-bis(trifluoromethyl)benzidine (2,2'-bis(trifluoromethyl)benzidine, TFDB) were dissolved, and The resulting solution was maintained at 25°C. 15.005 grams (0.051 moles) of biphenyl-tetracarboxylic dianhydride (BPDA) was added thereto, followed by stirring for 3 hours to completely dissolve the BPDA, and then 22.657 grams (0.051 moles) of 4,4'-(hexa Fluoroisopropylidene) diphthalic anhydride (4,4'-(hexafluoroisopropylidene) diphthalic anhydride, 6FDA), and completely dissolved in it. The reactor temperature was lowered to 10° C., 13.805 g (0.068 mol) of terephthaloyl chloride (TPC) was added thereto, and the reaction was carried out at 25° C. for 12 hours to obtain a compound having 12% by weight. solids content of the polymer solution.

To the obtained polymer solution, 17.75 g of pyridine and 22.92 g of acetic anhydride were added, followed by stirring for 30 minutes, and then further stirring at 70° C. for 1 hour. The resulting product was cooled to room temperature, and 20 liters of methanol was added to the resulting polymer solution to precipitate a solid body, and the precipitated solid was filtered, pulverized, washed again with 2 liters of methanol, and then dried in vacuum at 100° C. for 6 hours to obtain a powdery light-transmitting polymer solid. The light-transmitting polymer solid prepared herein is a polyimide-based resin solid. More specifically, the light-transmitting polymer solid prepared in Preparation Example 1 is a powder of polyamide-imide polymer solid, and is a light-transmitting resin powder.

<Example 1>

35.40 parts by weight of N,N-dimethylacetamide (DMAc) (first solvent) was charged into a 500 ml reactor, and then stirred while maintaining the temperature of the reactor at 10°C. Then, 0.36 parts by weight (of the first amount) of polyamide-imide as a solid powder (light-transmitting resin powder) prepared in Preparation Example 1 was added thereto, followed by stirring for 1 hour, and then the temperature was raised to 25°C to prepare a light-transmitting resin solution as a liquid.

Fill another 1 liter reactor with 35.76 parts by weight of silica dispersion A (DMAC-ST, Nissan Chemical Industries). In silica dispersion A, the average particle size is 10 nm Silica particles down to 15 nm were dispersed in N,N-dimethylacetamide (DMAc) solution (second solvent) in an amount of 20% by weight, and at a rate of 0.5 g/min using a cylindrical pump The prepared liquid light-transmitting resin solution was slowly injected while maintaining the temperature of the reactor at 25° C. to prepare a first mixed solution in which the silica dispersion was mixed with the light-transmitting resin solution.

336.32 parts by weight of DMAc as a third solvent was added to the first mixed solution, followed by stirring. Then, 64.04 parts by weight (second amount) of polyamide as solid powder (light-transmitting resin powder) prepared in Preparation Example 1 was added thereto. Amine-imide, followed by stirring, to prepare a second mixed solution. The second mixed solution is a light-transmitting resin solution in which silicon dioxide particles are dispersed.

The obtained second mixed solution was applied to a glass substrate, cast, and dried with hot air at 130° C. for 30 minutes to produce a film, and then the produced film was peeled from the glass substrate and fixed to the frame with pins. There is no particular limitation on the type of casting substrate. The casting substrate may be a glass substrate, a stainless steel (SUS) substrate, a Teflon substrate, or the like. The casting substrate used in Example 1 was a glass substrate, and the same applies below.

The frame fixed with the film was put into a vacuum furnace, slowly heated from 100°C to 280°C for 2 hours, cooled slowly, and separated from the frame to obtain a light-transmitting film. The light-transmitting film was further heat-treated at 250° C. for 5 minutes.

Therefore, the production of the transparent film 100 having a thickness t1 of 80 μm and including the transparent matrix 110 and the silica-based filler 120 dispersed in the transparent matrix 110 is completed. Here, the light-transmitting matrix 110 is formed of polyimide-based resin, and has a film form.

<Example 2>

16.78 parts by weight of DMAc (first solvent) was charged into a 500 ml reactor, and then stirred while maintaining the temperature of the reactor at 10°C. Then, 0.17 parts by weight (first amount) of polyamide-imide as a solid powder (light-transmitting resin powder) prepared in Preparation Example 1 was added thereto, followed by stirring for 1 hour, and then the temperature was raised to 25°C to prepare a light-transmitting resin solution as a liquid.

16.95 parts by weight of silica dispersion A (DMAC-ST, Nissan Chemical Industries (Nissan Chemical Industries)) was charged into another 1 liter reactor, In silica dispersion A, silica particles with an average particle size of 10 nm to 15 nm were dispersed in N,N-dimethylacetamide (DMAc) solution (second solvent) in an amount of 20% by weight. ), and use a cylindrical pump to slowly inject the prepared liquid light-transmitting resin solution at a rate of 0.5 g/min, while maintaining the temperature of the reactor at 25°C to prepare the silica dispersion mixed with the light-transmitting resin solution the first mixed solution.

351.37 parts by weight of DMAc was added as a third solvent to the first mixed solution, followed by stirring. Then, 64.23 parts by weight (second amount) of polyamide-imide as a solid powder (light-transmitting resin powder) prepared in Preparation Example 1 was added thereto, followed by stirring, to prepare a second mixed solution. The second mixed solution is a light-transmitting resin solution in which silicon dioxide particles are dispersed.

The obtained second mixed solution was applied to a casting base, cast, and dried with hot air at 130° C. for 30 minutes to produce a film, and then the produced film was peeled from the casting base and fixed to a frame with pins.

The frame fixed with the film was put into a vacuum furnace, slowly heated from 100°C to 280°C for 2 hours, cooled slowly, and separated from the frame to obtain a light-transmitting film. The light-transmitting film was further heat-treated at 250° C. for 5 minutes.

Therefore, the production of the transparent film 100 having a thickness t1 of 80 μm and including the transparent matrix 110 and the silica-based filler 120 dispersed in the transparent matrix 110 is completed.

<Example 3>

1.61 parts by weight of DMAc (first solvent) was charged into a 100 ml reactor, and then stirred while maintaining the temperature of the reactor at 10°C. Then, to Thereto, 0.017 parts by weight (of the first amount) of polyamide-imide as a solid powder (light-transmitting resin powder) prepared in Preparation Example 1 was added, followed by stirring for 1 hour, and then raising the temperature to 25° C. , to prepare a light-transmitting resin solution as a liquid.

1.63 parts by weight of silica dispersion A (DMAC-ST, Nissan Chemical Industries (Nissan Chemical Industries)) was filled into another 1-liter reactor and slowly injected at a rate of 0.5 g/min using a cylindrical pump. liquid light-transmitting resin solution while maintaining the temperature of the reactor at 25° C. to prepare a first mixed solution in which the silica dispersion was mixed with the light-transmitting resin solution.

363.63 parts by weight of DMAc was added as a third solvent to the first mixed solution, followed by stirring. Then, 64.383 parts by weight (second amount) of polyamide-imide as a solid powder (light-transmitting resin powder) prepared in Preparation Example 1 was added thereto, followed by stirring, to prepare a second mixed solution. The second mixed solution is a light-transmitting resin solution in which silicon dioxide particles are dispersed.

The obtained second mixed solution was applied to a casting base, cast, and dried with hot air at 130° C. for 30 minutes to produce a film, and then the produced film was peeled from the casting base and fixed to a frame with pins.

The frame fixed with the film was put into a vacuum furnace, slowly heated from 100°C to 280°C for 2 hours, cooled slowly, and separated from the frame to obtain a light-transmitting film. The light-transmitting film was further heat-treated at 250° C. for 5 minutes.

Therefore, the production of the transparent film 100 having a thickness t1 of 80 μm and including the transparent matrix 110 and the silica-based filler 120 dispersed in the transparent matrix 110 is completed.

<Example 4>

4.85 parts by weight of DMAc (first solvent) was charged into a 100 ml reactor, and then stirred while maintaining the temperature of the reactor at 10°C. Then, 0.05 parts by weight (of the first amount) of polyamide-imide as a solid powder (light-transmitting resin powder) prepared in Preparation Example 1 was added thereto, followed by stirring for 1 hour, and then the temperature was raised to 25°C to prepare a light-transmitting resin solution as a liquid.

Fill another 1 liter reactor with 2.45 parts by weight of silica dispersion B (MEK-ST-40, Nissan Chemical Industries). In silica dispersion B, the average particle size is 10 Silica particles of nanometers to 15 nanometers were dispersed in methyl ethyl ketone (MEK) solution (second solvent) in an amount of 40% by weight, and were prepared by slow injection at a rate of 0.5 g/min using a cylindrical pump The liquid light-transmitting resin solution, while maintaining the temperature of the reactor at 25° C., to prepare a first mixed solution in which the silica dispersion is mixed with the light-transmitting resin solution.

363.46 parts by weight of DMAc was added as a third solvent to the first mixed solution, followed by stirring. Then, 64.35 parts by weight (second amount) of polyamide-imide as a solid powder (light-transmitting resin powder) prepared in Preparation Example 1 was added thereto, followed by stirring, to prepare a second mixed solution. The second mixed solution is a light-transmitting resin solution in which silicon dioxide particles are dispersed.

The obtained second mixed solution was applied to a casting base, cast, and dried with hot air at 130° C. for 30 minutes to produce a film, and then the produced film was peeled from the casting base and fixed to a frame with pins.

Put the frame fixed with the membrane into a vacuum furnace and heat slowly from 100 °C to 280°C for 2 hours, slowly cooled, and separated from the frame to obtain a light-transmitting film. The light-transmitting film was further heat-treated at 250° C. for 5 minutes.

Therefore, the production of the transparent film 100 having a thickness t1 of 80 μm and including the transparent matrix 110 and the silica-based filler 120 dispersed in the transparent matrix 110 is completed.

<Example 5>

18.55 parts by weight of DMAc (first solvent) was charged into a 100 ml reactor, and then stirred while maintaining the temperature of the reactor at 10°C. Then, 0.19 parts by weight (of the first amount) of polyamide-imide as a solid powder (light-transmitting resin powder) prepared in Preparation Example 1 was added thereto, followed by stirring for 1 hour, and then the temperature was raised to 25°C to prepare a light-transmitting resin solution as a liquid.

9.37 parts by weight of Silica Dispersion B (MEK-ST-40, Nissan Chemical Industries) was charged into another 1-liter reactor, and injected slowly at a rate of 0.5 g/min using a cylindrical pump The liquid light-transmitting resin solution was prepared while maintaining the temperature of the reactor at 25° C. to prepare a first mixed solution in which the silica dispersion was mixed with the light-transmitting resin solution.

359.31 parts by weight of DMAc was added as a third solvent to the first mixed solution, followed by stirring. Then, 64.21 parts by weight (second amount) of polyamide-imide as a solid powder (light-transmitting resin powder) prepared in Preparation Example 1 was added thereto, followed by stirring, to prepare a second mixed solution. The second mixed solution is a light-transmitting resin solution in which silicon dioxide particles are dispersed.

The obtained second mixed solution is applied to the cast base, cast, and at 130 It was dried with hot air for 30 minutes at °C to produce a film, and then the produced film was peeled from the casting base and fixed to the frame with pins.

The frame fixed with the film was put into a vacuum furnace, slowly heated from 100°C to 280°C for 2 hours, cooled slowly, and separated from the frame to obtain a light-transmitting film. The light-transmitting film was further heat-treated at 250° C. for 5 minutes.

Therefore, the production of the transparent film 100 having a thickness t1 of 80 μm and including the transparent matrix 110 and the silica-based filler 120 dispersed in the transparent matrix 110 is completed.

<Example 6>

79.70 parts by weight of DMAc (first solvent) was charged into a 1 liter reactor, and then stirred while maintaining the temperature of the reactor at 10°C. Then, 0.8 parts by weight (of the first amount) of polyamide-imide as a solid powder (light-transmitting resin powder) prepared in Preparation Example 1 was added thereto, followed by stirring for 1 hour, and then the temperature was raised to 25°C to prepare a light-transmitting resin solution as a liquid.

40.25 parts by weight of Silica Dispersion B (MEK-ST-40, Nissan Chemical Industries) was charged into another 1-liter reactor and injected slowly at a rate of 0.5 g/min using a cylindrical pump The liquid light-transmitting resin solution was prepared while maintaining the temperature of the reactor at 25° C. to prepare a first mixed solution in which the silica dispersion was mixed with the light-transmitting resin solution.

340.78 parts by weight of DMAc was added as a third solvent to the first mixed solution, followed by stirring. Then, 63.60 parts by weight (second amount) of polyamide as solid powder (light-transmitting resin powder) prepared in Preparation Example 1 was added thereto. Amine-imide, followed by stirring, to prepare a second mixed solution. The second mixed solution is a light-transmitting resin solution in which silicon dioxide particles are dispersed.

The obtained second mixed solution was applied to a casting base, cast, and dried with hot air at 130° C. for 30 minutes to produce a film, and then the produced film was peeled from the casting base and fixed to a frame with pins.

The frame fixed with the film was put into a vacuum furnace, slowly heated from 100°C to 280°C for 2 hours, cooled slowly, and separated from the frame to obtain a light-transmitting film. The light-transmitting film was further heat-treated at 250° C. for 5 minutes.

Therefore, the production of the transparent film 100 having a thickness t1 of 80 μm and including the transparent matrix 110 and the silica-based filler 120 dispersed in the transparent matrix 110 is completed.

<Example 7>

0.03 parts by weight of DMAc (first solvent) was charged into the reactor, and then stirred while maintaining the temperature of the reactor at 10°C. Then, 0.000335 parts by weight (of the first amount) of polyamide-imide as a solid powder (light-transmitting resin powder) prepared in Preparation Example 1 was added thereto, followed by stirring for 1 hour, and then the temperature was raised to 25°C to prepare a light-transmitting resin solution as a liquid.

For silica dispersion C (MEK-ST-ZL, Nissan Chemical Industries) (in which silica particles with an average particle size of 70 nm to 100 nm are dispersed in methyl ethyl ketone (MEK) solution (second solvent)) such that the amount of silica particles is adjusted to 10% by weight to prepare diluted silica dispersion C with a silica content of 10% by weight . Fill another 1-liter reactor with 0.067 parts by weight of silica dispersion C, and use a cylindrical pump to slowly inject the prepared liquid light-transmitting resin solution at a rate of 0.5 g/min while maintaining the temperature of the reactor at 25° C. to prepare a first mixed solution in which the silica dispersion is mixed with the light-transmitting resin solution.

364.87 parts by weight of DMAc was added as a third solvent to the first mixed solution, followed by stirring. Then, 64.39967 parts by weight (second amount) of polyamide-imide as a solid powder (light-transmitting resin powder) prepared in Preparation Example 1 was added thereto, followed by stirring, to prepare a second mixed solution. The second mixed solution is a light-transmitting resin solution in which silicon dioxide particles are dispersed.

The obtained second mixed solution was applied to a casting base, cast, and dried with hot air at 130° C. for 30 minutes to produce a film, and then the produced film was peeled from the casting base and fixed to a frame with pins.

The frame fixed with the film was put into a vacuum furnace, slowly heated from 100° C. to 280° C. for 2 hours, cooled slowly, and separated from the frame to obtain a light-transmitting film. The light-transmitting film was further heat-treated at 250° C. for 5 minutes.

Therefore, the production of the transparent film 100 having a thickness t1 of 80 μm and including the transparent matrix 110 and the silica-based filler 120 dispersed in the transparent matrix 110 is completed.

<Example 8>

0.16 parts by weight of DMAc (first solvent) was charged into the reactor, and then stirred while maintaining the temperature of the reactor at 10°C. Then, 0.001625 parts by weight (first amount) of the solid powder prepared in Preparation Example 1 was added thereto. (light-transmitting resin powder) of polyamide-imide, followed by stirring for 1 hour, and then raising the temperature to 25° C. to prepare a light-transmitting resin solution as a liquid.

0.325 parts by weight of the diluted silica dispersion C with a silica content of 10% by weight prepared in Example 7 was charged into another reactor and slowly injected using a cylindrical pump at a rate of 0.5 g/min to prepare The liquid light-transmitting resin solution, while maintaining the temperature of the reactor at 25° C., to prepare a first mixed solution in which the silica dispersion is mixed with the light-transmitting resin solution.

364.64 parts by weight of DMAc was added as a third solvent to the first mixed solution, followed by stirring. Then, 64.398 parts by weight (second amount) of polyamide-imide as a solid powder (light-transmitting resin powder) prepared in Preparation Example 1 was added thereto, followed by stirring, to prepare a second mixed solution. The second mixed solution is a light-transmitting resin solution in which silicon dioxide particles are dispersed.

The obtained second mixed solution was applied to a casting base, cast, and dried with hot air at 130° C. for 30 minutes to produce a film, and then the produced film was peeled from the casting base and fixed to a frame with pins.

The frame fixed with the film was put into a vacuum furnace, slowly heated from 100°C to 280°C for 2 hours, cooled slowly, and separated from the frame to obtain a light-transmitting film. The light-transmitting film was further heat-treated at 250° C. for 5 minutes.

Therefore, the production of the transparent film 100 having a thickness t1 of 80 μm and including the transparent matrix 110 and the silica-based filler 120 dispersed in the transparent matrix 110 is completed.

<Example 9>

3.22 parts by weight of DMAc (first solvent) was charged into a 100 ml reactor, and then stirred while maintaining the temperature of the reactor at 10°C. Then, 0.0325 parts by weight (of the first amount) of polyamide-imide as a solid powder (light-transmitting resin powder) prepared in Preparation Example 1 was added thereto, followed by stirring for 1 hour, and then the temperature was raised to 25°C to prepare a light-transmitting resin solution as a liquid.

6.5 parts by weight of the diluted silica dispersion C with a silica content of 10% by weight prepared in Example 7 were charged into another 1 liter reactor and slowly fed at a rate of 0.5 g/min using a cylindrical pump. The prepared liquid light-transmitting resin solution was injected while maintaining the temperature of the reactor at 25° C. to prepare a first mixed solution in which the silica dispersion was mixed with the light-transmitting resin solution.

359.08 parts by weight of DMAc was added as a third solvent to the first mixed solution, followed by stirring. Then, 64.367 parts by weight (second amount) of polyamide-imide as a solid powder (light-transmitting resin powder) prepared in Preparation Example 1 was added thereto, followed by stirring, to prepare a second mixed solution. The second mixed solution is a light-transmitting resin solution in which silicon dioxide particles are dispersed.

The obtained second mixed solution was applied to a casting base, cast, and dried with hot air at 130° C. for 30 minutes to produce a film, and then the produced film was peeled from the casting base and fixed to a frame with pins.

The frame fixed with the film was put into a vacuum furnace, slowly heated from 100°C to 280°C for 2 hours, cooled slowly, and separated from the frame to obtain a light-transmitting film. The light-transmitting film was further heat-treated at 250° C. for 5 minutes.

Thus, the finished film has a thickness t1 of 80 micrometers and includes a light-transmitting matrix 110 And the production of the light-transmitting film 100 of the silica-based filler 120 dispersed in the light-transmitting matrix 110 .

<Comparative example 1>

The light-transmitting film according to Comparative Example 1 was prepared using a solution-powder mixing method.

Specifically, 420.48 parts by weight of DMAc and 40.25 parts by weight of silica dispersion B (MEK-ST-40, Nissan Chemical Industries) were charged into a 1-liter reactor, and the silica dispersion In B, silica particles with an average particle diameter of 10 nm to 15 nm were dispersed in a methyl ethyl ketone (MEK) solution (second solvent) in an amount of 40% by weight, and then stirred while the reaction The temperature of the vessel was maintained at 10 °C. Then, 64.4 parts by weight of the polyamide-imide prepared in Preparation Example 1 as a solid powder was added thereto, followed by stirring for 1 hour, and then the temperature was raised to 25° C. to obtain a powder having silica dispersed therein. Light-transmitting resin solution of particles.

The obtained second mixed solution was applied to a casting base, cast, and dried with hot air at 130° C. for 30 minutes to produce a film, and then the produced film was peeled from the casting base and fixed to a frame with pins.

The frame fixed with the film was put into a vacuum furnace, slowly heated from 100°C to 280°C for 2 hours, cooled slowly, and separated from the frame to obtain a light-transmitting film. The light-transmitting film was further heat-treated at 250° C. for 5 minutes to produce a light-transmitting film having a thickness t1 of 80 μm.

<Comparative example 2>

The DMAc of 371.72 parts by weight and the silicon dioxide of 35.76 parts by weight are divided into Dispersion A (DMAC-ST, Nissan Chemical Industries) was charged into a 1-liter reactor. In silica dispersion A, silica particles with an average particle size of 10 nm to 15 nm were mixed with 20 An amount of % by weight was dispersed in an N,N-dimethylacetamide (DMAc) solution (second solvent), and then stirred while maintaining the temperature of the reactor at 10°C. Then, 64.4 parts by weight of the polyamide-imide prepared in Preparation Example 1 as a solid powder was added thereto, followed by stirring for 1 hour, and then the temperature was raised to 25° C. to obtain a powder having silica dispersed therein. Light-transmitting resin solution of particles.

The obtained second mixed solution was applied to a casting base, cast, and dried with hot air at 130° C. for 30 minutes to produce a film, and then the produced film was peeled from the casting base and fixed to a frame with pins.

The frame fixed with the film was put into a vacuum furnace, slowly heated from 100°C to 280°C for 2 hours, cooled slowly, and separated from the frame to obtain a light-transmitting film. The light-transmitting film was further heat-treated at 250° C. for 5 minutes to produce a light-transmitting film having a thickness t1 of 80 μm.

<Comparative example 3>

362.30 parts by weight of DMAc were charged into a 1 liter reactor. For silica dispersion C (MEK-ST-ZL, Nissan Chemical Industries) (in which silica particles with an average particle size of 70 nm to 100 nm are dispersed in methyl ethyl ketone (MEK) solution (second solvent)) so that the content of silica particles is adjusted to 10% by weight to prepare diluted silica dispersion C with a silica content of 10% by weight . 6.5 parts by weight of silica dispersion C with a silica content of 10 wt. liter reactor, and then stirred while maintaining the temperature of the 1 liter reactor at 10°C. Then, 64.4 parts by weight of the polyamide-imide prepared in Preparation Example 1 as a solid powder was added thereto, followed by stirring for 1 hour, and then the temperature was raised to 25° C. to obtain a powder having silica dispersed therein. Light-transmitting resin solution of particles.

The obtained second mixed solution was applied to a casting base, cast, and dried with hot air at 130° C. for 30 minutes to produce a film, and then the produced film was peeled from the casting base and fixed to a frame with pins.

The frame fixed with the film was put into a vacuum furnace, slowly heated from 100°C to 280°C for 2 hours, cooled slowly, and separated from the frame to obtain a light-transmitting film. The light-transmitting film was further heat-treated at 250° C. for 5 minutes to produce a light-transmitting film having a thickness t1 of 80 μm.

<Measurement example>

The following measurements were performed on the light-transmitting films produced in Examples 1 to 9 and Comparative Examples 1 to 3.

(1) Average two-dimensional dispersion (using TEM)

Microscope images were obtained by imaging the light-transmitting films produced in Examples 1 to 9 and Comparative Examples 1 to 3 using a transmission electron microscope (TEM). The details of the imaging process are as follows.

First, each of the light-transmitting films 100 produced in Examples 1 to 9 and Comparative Examples 1 to 3 were thinly cut using a microtome to form samples 310 of the light-transmitting film 100 . Specifically, the light-transmitting film 100 is covered with a molding 210 including epoxy resin to fix the light-transmitting film 100 . Then, use a microtome to cut the The light-transmitting film 100 is cut thinly in the direction of the direction. Thus, a sample 310 of the light-transmitting film 100 having a thickness t2 of 120 nm was produced (see FIGS. 7 a and 7 b ). Sample 310 was produced under the following conditions:

- Sample handling element (tome): Leica EM UC7 from Leica Biosystems

- Equipment condition:

Speed: 1 mm/s

Feed thickness (t2): 120nm

- Knife: DiATOME/Ultra 35 degrees

Next, a transmission electron microscope (TEM) is used to image the sample 310 of the light-transmitting film 100 to obtain a microscope image. Specifically, the sample 310 of the light-transmissive film 100 is imaged along the direction indicated by "PIC" in FIG. 7b to obtain a microscope image. Imaging was performed under the following conditions:

- Transmission Electron Microscope (TEM) (JEM-2100F from JEOL)

- Accelerating voltage: 200 kV

- Magnification: 20,000x(20K)

Next, the obtained microscope images are preprocessed.

- Image processing: perform conversion to black and white images by color separation to obtain 2D black and white images

Next, coordinate information about the location of the particles of filler 120 is extracted from the processed image. Coordinate data are extracted under the following conditions.

- Image analysis program: iTEM (using iTEM5.1 produced by Olympus)

- Obtaining a rendered image by removing from the image what remains after excluding the points corresponding to the filler particles 120 , and deleting from the points of the image points whose diameter is less than 1/10 of the average diameter of the particles of the filler 120 .

- Set the coordinates of the particles based on the filler 120 (points in the image) to the coordinates of the particles of the filler 120.

Next, the number N of filler particles is determined based on the coordinates of the particles of filler 120, and Dx, which is an ideal two-dimensional distance between particles of filler 120, is calculated according to the method shown in FIG.

Assuming that the particles of the filler 120 are uniformly dispersed in the rendered image and located at the corresponding vertices of an equilateral triangle with sides of equal length, as shown in FIG. 3 , in order to calculate the ideal two-dimensional distance Dx between the particles of the filler 120 .

As shown in FIG. 3, one side of the equilateral triangle is set parallel to the x-axis direction.

In FIG. 3 , the length of the rendered image in the X-axis direction is represented by "a", the length in the Y-axis direction is represented by "b", and the number of particles of the filler 120 arranged in a row in the X-axis direction is represented by " Nx" represents the number of particles of the filler 120 arranged in a row in the Y-axis direction by "Ny", and the length of one side of an equilateral triangle is represented by "Dx" as an ideal two-dimensional distance between filler particles. When the total number of filler particles is N, the following relationship is satisfied.

N=Nx×Ny

a=(Nx-1)×Dx

b=(Ny-1)×Dx×cos 30°

Area of rendered image = a×b

N, a and b are obtained by analyzing the rendered image, and Dx is obtained according to N, a and b.

In addition, the distance Daj between the particles of the filler 120 is measured by using the actual coordinates of the particles of the filler 120 obtained by an image analysis program.

The average two-dimensional dispersibility of the filler 120 is calculated according to Equation 1 using N, Dx, and Daj thus obtained.

(2) Average two-dimensional dispersion (using SEM)

Microscopic images were obtained by imaging the light-transmitting films prepared in Examples 1 to 9 and Comparative Examples 1 to 3 using a scanning electron microscope (SEM). The details of the imaging process are as follows.

First, each of the light-transmitting films 100 is covered with a molding 210 including epoxy resin to fix the light-transmitting films 100 . Then, the light-transmitting film 100 is thinly cut in a direction parallel to the thickness t1 direction using a microtome. Thus, a sample 410 is generated, as shown in FIG. 8 . Sample 410 was produced under the following conditions:

- Sample handling element: Leica EM UC7 from Leica Biosystems. Molded with epoxy and then cut in cross section noodle.

- Knife: DiATOME/Ultra 35 degrees

- Equipment Conditions: Speed: 1mm/sec

Next, a field emission scanning electron microscope (FE-SEM) is used as a scanning electron microscope (SEM) to image the sample 410 of the light-transmitting film 100 to obtain a microscope image. Specifically, the sample 410 of the light-transmissive film 100 is imaged along the direction indicated by "PIC" in FIG. 8 to obtain a microscope image. Imaging was performed under the following conditions:

- Scanning electron microscope: JSM-7601F (Field Emission Scanning Electron Microscope, FE-SEM), manufactured by JEOL

- Accelerating voltage: 10 kV

- Mode: SEI

- WD: 7 to 9

- Magnification: 3,000x(3K)

Next, the obtained microscope images are preprocessed.

- Image processing: perform conversion to black and white images by color separation to obtain 2D black and white images

Next, coordinate information about the location of the particles of filler 120 is extracted from the processed image. Coordinate data are extracted under the following conditions.

- Image analysis program: iTEM (using iTEM5.1 produced by Olympus)

- the remaining after excluding the points corresponding to the filler particles 120 by removing from the image part, and the points whose diameter is less than 1/10 of the average diameter of the particles of the filler 120 are deleted from the points of the image to obtain a rendered image.

- Set the coordinates of the particles based on the filler 120 (points in the image) to the coordinates of the particles of the filler 120.

Next, the number N of particles of the filler 120 is determined based on the coordinates of the particles of the filler 120, and Dx, which is an ideal two-dimensional distance between the particles of the filler 120, is calculated according to the method shown in FIG.

Calculation of Dx is performed in the same method as in the case of using a transmission electron microscope (TEM).

(3) Light transmittance (%): According to the ASTM E313 standard, the average light transmittance at a wavelength of 360 nm to 740 nm was measured using a spectrometer (CM-3700D, KONICA MINOLTA).

(4) Yellowness index: According to the ASTM E313 standard, the yellowness index was measured using a spectrometer (CM-3700D, KONICA MINOLTA).

(5) Haze: The light-transmitting film produced was cut into pieces of 50 mm×50 mm, and a haze meter (model name: HM-150) manufactured by Murakami Color Research Laboratory was used according to ASTM The D1003 standard measures 5 times, and sets the average value as the haze.

(6) Young's modulus and 2% yield strength: the Young's modulus and 2% yield strength of the light-transmitting film were measured according to ASTM D885 using a universal tensile testing machine produced by Instron.

The measurement results are shown in Table 1 below.

According to the measurement results shown in Table 1, it can be seen that the light-transmitting film 100 according to an embodiment of the present disclosure has an average two-dimensional dispersion of 25% or more, and thus exhibits excellent light transmittance, low yellowness, and low yellowness. index and low haze.

100: Light-transmitting film/polyimide film

110: Light-transmitting matrix/polyimide-based matrix/matrix

120: filler/filler particles

Claims (20)

A light-transmitting film, comprising: a light-transmitting matrix; and a filler dispersed in the light-transmitting matrix, wherein the light-transmitting matrix comprises imide repeating units, wherein the filler has an average dioxane of 25% or greater than 25%. Dimensional dispersion, and wherein said average two-dimensional dispersion is calculated according to the following equation 1:

Wherein Dx is the ideal two-dimensional distance between the filler particles calculated according to the number of filler particles shown in the microscope image of the sample of the light-transmitting film and the area of the microscope image; Daj is the ideal two-dimensional distance shown in the microscope image and N is the total number of filler particles in the microscope image. The light-transmitting film according to claim 1, wherein the filler has an average two-dimensional dispersion of 25% to 55%. The light-transmitting film according to claim 1, wherein the filler includes at least one of inorganic particles, organic particles and organic-inorganic hybrid particles. The light-transmitting film according to claim 1, wherein the filler includes silicon dioxide (SiO ₂ ). The light-transmitting film according to claim 1, wherein the filler has an average particle diameter of 5 nm to 50 nm. The light-transmitting film according to claim 1, wherein the filler is present in an amount of 0.01% to 20% by weight based on the total weight of the light-transmitting film. The light-transmitting film according to claim 1, wherein the light-transmitting film has a yellowness index of 3.5 or less. The light-transmitting film according to claim 1, wherein the light-transmitting film has a haze of 2% or less. The light-transmitting film according to claim 1, wherein the light-transmitting film has a light transmittance of 88% or greater. The light-transmitting film according to claim 1, wherein the light-transmitting film has a 2% yield strength of 110 megapascals or greater than 110 megapascals. The light-transmitting film according to claim 1, wherein the light-transmitting film has a Young's modulus of 4.5 GPa or greater than 4.5 GPa. The light-transmitting film according to claim 1, wherein the microscope image is a transmission electron microscope (TEM) image taken at a magnification of 20,000x. The light-transmitting film according to claim 12, wherein the light-transmitting film is cut into 120 nm thickness to obtain the samples. The light-transmitting film according to claim 12, wherein the filler has an average particle diameter of 5 nm to 80 nm. The light-transmitting film according to claim 1, wherein the microscope image is a scanning electron microscope (SEM) image taken at a magnification of 3,000x. The light-transmitting film according to claim 15, wherein the microscope image is obtained by imaging a cross-section of the light-transmitting film parallel to the thickness direction. The light-transmitting film according to claim 15, wherein the filler has an average particle diameter of 50 nm to 500 nm. The light-transmitting film according to claim 1, wherein the light-transmitting matrix comprises amide repeating units. A display element, comprising: a display panel; and the light-transmitting film according to any one of Claims 1 to 18, disposed on the display panel. A method for measuring the average two-dimensional dispersion of a filler, the method comprising: producing a sample of a light-transmitting film comprising a filler as described in claim 1; obtaining a microscope image of the sample; and preprocessing the microscope image , to obtain the processed image; obtaining coordinate data about the location of filler particles from the processed image; determining a number of the filler particles using the coordinate data; calculating the filler particles using the number of the filler particles and the area of the microscope image ideal two-dimensional distance between; and calculating the distance between the filler particles using the coordinate data.

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