Viewing angle control film and display device including the same

Abstract

The present disclosure relates to a viewing angle control film and a display device including the same, and more particularly, according to an aspect of the present disclosure, a viewing angle control film includes a first base member, a first electrode disposed on the first base member, a transparent resin layer disposed on the first electrode and having a plurality of accommodation units, a second electrode disposed on the transparent resin layer, and a second base member disposed on the second electrode, wherein an ink including a charged black particle, a charged high refractive index particle, and a solvent is accommodated in each of the plurality of accommodation units, and the charged black particle has an opposite charge to the charged high refractive index particle.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to Korean Patent Application No. 10-2021-0113243, filed with the Korean Intellectual Property Office on August 26, 2021, the disclosure of which is incorporated herein by reference. Technical Field

[0003] This disclosure relates to a viewing angle control film and a display device including the viewing angle control film, and more specifically, to a viewing angle control film that has a fast switching speed between a wide viewing angle mode and a narrow viewing angle mode, excellent driving characteristics, and can improve color uniformity, and a display device including the viewing angle control film. Background Technology

[0004] With the increasing demand for personal privacy protection, various related products are being developed across different sectors. Among products that ensure personal privacy, the demand for viewing angle control devices attached to various displays (such as mobile phones, tablets, monitors, or vehicle displays) to block lateral light transmission and narrow the viewing angle is increasing year by year.

[0005] In this regard, existing technologies already utilize thin-film viewing angle control films that alternately form light-transmitting regions that allow light to pass through and light-blocking regions that block light in specific directions. These films include transmissive regions and light-blocking regions disposed between them to block or absorb light. The light-blocking regions consist of black pigment. In light incident from below, light with an incident angle equal to or greater than a predetermined angle is absorbed or blocked by the repeatedly formed light-blocking regions, preventing light from passing through the viewing angle control film. Consequently, at viewing angles equal to or greater than the predetermined angle, the light transmittance is significantly reduced, making the screen invisible. However, a drawback of existing viewing angle control films is that the viewing angle cannot be restored to its current state without removing the film, thus requiring removal of the viewing angle control film.

[0006] To address this inconvenience, a viewing angle control membrane is being developed that selectively switches between wide and narrow viewing angle modes based on an externally applied electrical signal without requiring the membrane to be attached or detached.

[0007] Meanwhile, existing switchable viewing angle control films exhibit ghosting, where the screen appears to overlap due to the different refractive indices of the transparent resin and ink that make up the film. Summary of the Invention

[0008] The objective of this disclosure is to provide a viewing angle control film in which the ghosting phenomenon is improved by reducing the refractive index difference between the transparent resin and the ink while maintaining high brightness and driving characteristics.

[0009] Furthermore, another objective of this disclosure is to provide a viewing angle control film that improves particle settling in ink and provides excellent switching speed between wide and narrow viewing angle modes.

[0010] The purpose of this disclosure is not limited to the above-mentioned purposes, and other purposes not mentioned above will be clearly understood by those skilled in the art from the following description.

[0011] According to one aspect of this disclosure, a viewing angle control film includes: a first substrate member; a first electrode disposed on the first substrate member; a transparent resin layer disposed on the first electrode and having a plurality of receiving units; a second electrode disposed on the transparent resin layer; and a second substrate member disposed on the second electrode, wherein each of the plurality of receiving units contains an ink comprising charged black particles, charged high refractive index particles and a solvent, and the charged black particles have a charge opposite to that of the charged high refractive index particles.

[0012] According to one aspect of this disclosure, a display device includes: a display panel; and a viewing angle control film disposed above or below the display panel.

[0013] Further details of the exemplary embodiments are included in the detailed description and accompanying drawings.

[0014] According to this disclosure, in the viewing angle control film, an ink comprising charged black particles, charged high-refractive-index particles, and a solvent is contained in each of a plurality of containment units. Therefore, the viewing angle control film of this disclosure reduces the refractive index difference between the ink and the transparent resin layer, thereby improving ghosting phenomena.

[0015] Furthermore, the viewing angle control film of this disclosure uses an ink comprising charged black particles and charged high refractive index particles to improve particle settling caused by gravity, thereby improving driving characteristics.

[0016] Furthermore, the viewing angle control film according to this disclosure and the display device including the viewing angle control film have excellent switching speed between wide viewing angle mode and narrow viewing angle mode and excellent driving performance.

[0017] The effects of this disclosure are not limited to those illustrated above; this specification includes a variety of other effects. Attached Figure Description

[0018] The above and other aspects, features and other advantages of this disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0019] Figure 1 This is a schematic cross-sectional view of the control membrane according to exemplary embodiments of the present disclosure;

[0020] Figure 2 This is an enlarged view of the control membrane according to exemplary embodiments of the present disclosure;

[0021] Figure 3A This is a schematic cross-sectional view of a view control membrane according to an exemplary embodiment of the present disclosure in a narrow view mode;

[0022] Figure 3B This is a schematic cross-sectional view of a view control membrane according to an exemplary embodiment of the present disclosure in a wide-viewing-angle mode;

[0023] Figure 4 This is a schematic cross-sectional view of the control membrane according to exemplary embodiments of the present disclosure;

[0024] Figure 5 This is a schematic cross-sectional view of an organic light-emitting display device according to an exemplary embodiment of the present disclosure;

[0025] Figure 6 This is a schematic cross-sectional view of a liquid crystal display device according to an exemplary embodiment of the present disclosure;

[0026] Figure 7 This is a graph showing the brightness measurement results of a display device including the viewing angle control film according to Example 1 and Comparative Examples 1 and 2;

[0027] Figure 8 This is a photograph showing that no ghosting phenomenon occurs in a display device including a viewing angle control film according to Embodiment 1;

[0028] Figure 9 This is a photograph showing the ghosting phenomenon in a display device including a viewing angle control film according to Comparative Example 1;

[0029] Figure 10 This is a graph showing the brightness measurement results of a display device including the viewing angle control film according to Example 1 and Comparative Examples 1, 3 to 5;

[0030] Figure 11 These are photographs showing whether ghosting occurs in a display device including the viewing angle control film according to Example 1 and Comparative Examples 1, 3 to 5. Detailed Implementation

[0031] The advantages and features of this disclosure, and its implementation methods, will become clear from the following exemplary embodiments described in detail with reference to the accompanying drawings. However, this disclosure is not limited to the exemplary embodiments disclosed herein, but will be implemented in various forms. These exemplary embodiments are provided by way of example only so that those skilled in the art can fully understand the disclosure and scope of this disclosure. Therefore, this disclosure will be limited only by the scope of the appended claims.

[0032] The shapes, dimensions, ratios, angles, and quantities shown in the accompanying drawings, which are used to describe exemplary embodiments of this disclosure, are merely examples, and this disclosure is not limited thereto. Throughout the specification, the same reference numerals generally denote the same elements. Furthermore, in the following description of this disclosure, detailed explanations of known related technologies may be omitted to avoid unnecessarily obscuring the subject matter of this disclosure. Terms such as “comprising,” “having,” and “including” as used herein are generally intended to allow for the addition of additional components, unless these terms are used in conjunction with the term “only.” Unless otherwise expressly stated, any reference to the singular may include the plural.

[0033] Even without explicit explanation, components are interpreted as including the normal tolerance range.

[0034] When using terms such as “above,” “over,” “below,” and “adjacent” to describe the positional relationship between two components, one or more components may be located between the two components, unless these terms are used in conjunction with the terms “immediately adjacent” or “directly.”

[0035] When one element or layer is disposed "on" another element or layer, the other layer or element may be disposed directly on the other element or inserted between the two elements or layers.

[0036] Although the terms "first," "second," etc., are used to describe various components, these components are not limited by these terms. These terms are only used to distinguish one component from other components. Therefore, the first component mentioned below can be the second component in the technical concept of this disclosure.

[0037] Throughout the specification, the same reference numerals generally denote the same elements.

[0038] The dimensions and thicknesses of the components shown in the accompanying drawings are for ease of description, and this disclosure is not limited to the dimensions and thicknesses of the components shown.

[0039] Features of the various embodiments of this disclosure may be combined or integrated with each other in part or in whole, and may be technically linked and operated in various ways, and the embodiments may be implemented independently or in relation to each other.

[0040] Unless otherwise stated herein, the average particle size refers to the particle size D50 corresponding to 50% of the cumulative particle size distribution measured using a Malvern Panalytical Nano ZS ZEN3600 at 20°C to 25°C.

[0041] Unless otherwise stated herein, charge refers to the ZETA potential value measured using a Malvern Panaco Nano ZS ZEN3600 at 20°C to 25°C.

[0042] In the following, a view control film and a display device according to exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

[0043] Figure 1 This is a schematic cross-sectional view of the view control membrane according to an exemplary embodiment of the present disclosure. Figure 2 This is an enlarged view of the view control membrane according to an exemplary embodiment of the present disclosure.

[0044] The viewing angle control film according to exemplary embodiments of the present disclosure is applied to an organic light-emitting display device or a liquid crystal display device. When no electric field is formed, the viewing angle control film operates in a wide viewing angle mode to transmit light incident from below at various angles, allowing the image displayed on the display device to be viewed not only from the front surface but also from the side. Conversely, when no electric field is formed, the viewing angle control film absorbs light incident from below with an incident angle equal to or greater than a predetermined angle. Therefore, the viewing angle control film operates in a narrow viewing angle mode to enable the user to observe the image displayed on the display device from the front surface of the display device or only within a specific narrow angle range.

[0045] First, refer to Figure 1 and Figure 2 The viewing angle control film 100 according to an exemplary embodiment of the present disclosure includes a first substrate member 110a, a first electrode 120a, an adhesive layer ADH, a transparent resin layer 130, a plurality of receiving units 140, an ink 150, a second electrode 120b, and a second substrate member 110b.

[0046] The first substrate member 110a protects the first electrode 120a and the transparent resin layer 130. The first substrate member 110a may be formed of a transparent insulating material. For example, the first substrate member 110a may be formed as one or more polymers selected from polycarbonate, polyethylene terephthalate, polyimide, cyclic olefin polymers, cyclic olefin copolymers and triacetyl cellulose.

[0047] For example, the thickness of the first base member 110a can be from 10 μm to 50 μm, but is not limited thereto.

[0048] A first electrode 120a is disposed on a first substrate member 110a. The first electrode 120a may be formed of a transparent conductive material to transmit light incident from below. For example, the transparent conductive material may be one or more selected from indium tin oxide (ITO), indium zinc oxide (IZO), indium tin zinc oxide (ITZO), and aluminum zinc oxide (AZO), but is not limited thereto.

[0049] The first electrode 120a may be formed on the front surface of the first base member 110a and may be selectively patterned to overlap with the plurality of receiving units 140 as needed.

[0050] For example, the thickness of the first electrode 120a can be from 5 μm to 30 μm, but is not limited to this.

[0051] A transparent resin layer 130 is disposed on the first electrode 120a. The transparent resin layer 130 may be formed of a transparent insulating resin that transmits light incident from the lower part of the viewing angle control film 100. For example, the transparent resin layer 130 may include one or more selected from acrylic resin, polycarbonate, polyethylene terephthalate, triacetyl cellulose resin, polyethylene, and polypropylene.

[0052] For example, the transparent resin layer 130 may comprise an acrylic resin, and preferably an acrylic resin formed by curing a polyurethane acrylate compound. Acrylic resins formed from polyurethane acrylate compounds have the advantages of excellent curability, high transparency, and excellent adhesive properties. Specifically, for example, the transparent resin layer 130 can be formed by photopolymerizing a resin composition comprising 85 wt% to 95 wt% of a polyurethane acrylate compound, 1 wt% to 5 wt% of a photoinitiator, 1 wt% to 5 wt% of a surfactant, and 1 wt% to 5 wt% of a release agent.

[0053] To improve the curing rate and enhance physical properties such as adhesion, a mixture of low-molecular-weight polyurethane acrylate compounds and high-molecular-weight polyurethane acrylate compounds can be used. For example, a transparent resin layer can use 25 wt% to 75 wt% of a low-molecular-weight polyurethane acrylate compound and 25 wt% to 75 wt% of a high-molecular-weight polyurethane acrylate compound based on the total weight of the polyurethane acrylate compounds.

[0054] For example, the number average molecular weight of low molecular weight polyurethane acrylate compounds can be less than 1000 g / mol or more than 100 g / mol but less than 1000 g / mol. Furthermore, the number average molecular weight of high molecular weight polyurethane acrylate compounds can be more than 10000 g / mol or more than 10000 g / mol but is not limited to these.

[0055] There are no particular limitations on photoinitiators if they are commonly used in the art to manufacture transparent resins. For example, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide or acyl phosphine oxide can be used as photoinitiators, but are not limited thereto.

[0056] The transparent resin layer 130 may also include a surfactant. For example, the surfactant may be an ionic phosphate. As another example, the surfactant may be one or more selected from tricresyl phosphate and tributyl phosphate. In order to drive the viewing angle control film 100, an electric field needs to be formed by applying a voltage to the first electrode 120a and the second electrode 120b, so that the surfactant is dispersed in the transparent resin layer 130 to facilitate the formation of the electric field.

[0057] The transparent resin layer 130 may also include a release agent. The transparent resin layer 130 includes a plurality of receiving units 140, which are formed by processing methods such as mastering, imprinting, or photolithography. The release agent can readily separate the structure used to form the pattern (e.g., the mold used to form the plurality of receiving units 140) from the transparent resin layer 130. For example, the release agent uses silicon-based, polyvinyl-based, or paraffin-based materials commonly used in the art without reducing transparency.

[0058] For example, the thickness of the transparent resin layer 130 can be from 120 μm to 200 μm, but is not limited to this.

[0059] The transparent resin layer 130 includes a plurality of receiving units 140. Each of the plurality of receiving units 140 is a space for receiving ink 150 that absorbs light incident on the transparent resin layer 130. The plurality of receiving units 140 are grooves formed in the transparent resin layer 130 and are formed on the first electrode 120a opposite to the second electrode 120b.

[0060] Each of the plurality of receiving units 140 is configured to be spaced apart from each other at a predetermined interval along a first direction (x-axis direction) perpendicular to the thickness direction (z-axis direction) of the transparent resin layer 130.

[0061] Each of the plurality of receiving units 140 extends along a second direction (y-axis direction) perpendicular to the thickness direction (z-axis direction) and the first direction (x-axis direction). That is, each of the plurality of receiving units 140 extends from any corner of the first electrode 120a to another corner parallel to that corner to form on the first electrode 120a having a striped structure.

[0062] Each of the plurality of receiving units 140 comprises a lower surface 141, an upper surface 142, a first connecting unit 143a, and a second connecting unit 143b. Specifically, each of the plurality of receiving units 140 includes a lower surface 141 opposite to the first electrode 120a and an upper surface 142 opposite to the lower surface 141. Furthermore, each of the plurality of receiving units 140 includes a first connecting unit 143a connecting one end of the lower surface 141 and one end of the corresponding upper surface 142, and a second connecting unit 143b connecting the other end of the lower surface 141 and the other end of the corresponding upper surface 142.

[0063] Each of the plurality of receiving units 140 can be configured such that its width decreases from the first electrode 120a toward the second electrode 120b. That is, the width W1 of the lower surface 141 of each of the plurality of receiving units 140 is greater than the width W2 of the upper surface 142. In this case, a wider viewing angle can be provided in wide-viewing-angle mode. Although the cross-sectional shape of each of the plurality of receiving units 140 is shown to be trapezoidal in the figures, this is merely an example and not a limitation.

[0064] The upper surface 142 of each of the plurality of receiving units 140 is formed to be spaced apart from the second electrode 120b. That is, each of the plurality of receiving units 140 does not penetrate the transparent resin layer 130 in the thickness direction (z-axis direction). When the plurality of receiving units 140 are formed with a hole structure that penetrates the transparent resin layer 130, if liquid ink 150 is filled into the receiving unit 140, there will be no problems such as leakage, resulting in excellent productivity. Therefore, the upper surfaces 142 of the plurality of receiving units 140 are spaced apart from the second electrode 120b so that they do not contact each other, and the transparent resin layer 130 exists in the space between them. However, it is not limited to this, and as needed, the plurality of receiving units 140 can be formed to completely penetrate the transparent resin layer 130 in the thickness direction (z-axis direction).

[0065] The ink 150 includes charged black particles 151, charged high-refractive-index particles 152, and solvent 153. The charged black particles 151, acting as light-absorbing materials, absorb light incident on the transparent resin layer 130. The charged high-refractive-index particles 152 increase the refractive index of the ink 150 to reduce the refractive index difference between the transparent resin layer 130 and the ink 150. The solvent 153 disperses the charged black particles 151 and charged high-refractive-index particles 152, which are solid powders, within multiple containment units 140 to prevent sedimentation.

[0066] For example, solvent 153 may be one or more selected from halogenated hydrocarbon solvents, isoparaffin solvents, and ether solvents.

[0067] For example, the halogenated hydrocarbon solvent can be a fully or partially halogenated hydrocarbon. For example, the halogenated hydrocarbon solvent can include one or more of the following: halogenated hydrocarbon 0.8, halogenated hydrocarbon 1.8, halogenated hydrocarbon 4.2 and halogenated hydrocarbon 6.3 from Halocarbon LLC; FC-72, FC-74 and FC-70 from 3M; FCL 1031 from Milo; and HT55 from Solvay.

[0068] For example, isoparaffin solvents may include, but are not limited to, one or more of IsoparG, IsoparL, IsoparC, IsoparE, IsoparM and IsoparH selected from ExxonMobil Corporation.

[0069] For example, the ether solvent may include, but is not limited to, one or more selected from diethylene glycol dimethyl ether, propylene glycol methyl ether, and propylene glycol methyl ether acetate.

[0070] Solvent 153 varies in density and dielectric constant depending on its type, and is appropriately selected according to the required properties. Furthermore, solvent 153 can use a single material, and, if necessary, two or more materials can be mixed to control the density or dielectric constant of ink 150.

[0071] Furthermore, considering process stability, it is preferable to use a solvent with a flash point below 60 degrees Celsius as solvent 153.

[0072] Simultaneously, solvent 153 is preferably used after removing moisture with a moisture-removing agent. Moisture in solvent 153 promotes particle aggregation, increasing the viscosity of ink 150. As the viscosity of ink 150 increases, the migration rate of charged black particles 151 decreases, deteriorating driving characteristics and reducing the switching speed between wide-viewing-angle and narrow-viewing-angle modes. Therefore, it is preferable to use moisture-removing agents commonly used in the art (e.g., zeolite, magnesium hydroxide, and porous silica) to remove as much moisture as possible from solvent 153.

[0073] The charged black particles 151 are formed of a light-absorbing material, which allows the charged black particles to absorb light incident on the transparent resin layer 130. For example, the charged black particles 151 may be one or more black particles selected from carbon nanotubes and carbon black, which are chemically stable and have excellent light absorption properties.

[0074] The charged black particles 151 can have a porous or non-porous structure. The charged black particles 151 need to remain stably dispersed in the ink 150 without settling due to gravity. Therefore, it is preferable that the charged black particles 151 have a density substantially equal to that of the solvent 153. When using a solvent 153 with a low density, the density between the solvent 153 and the charged black particles 151 can be controlled to be equal using porous black particles with a relatively low density. Furthermore, the charged black particles 151 can have a hollow structure. When the charged black particles have a hollow structure, their density is lower than that of particles without a hollow structure. Therefore, when using a solvent 153 with a low density, black particles with a hollow structure can be used to reduce the density difference between the solvent 153 and the charged black particles 151. Thus, the charged black particles 151 do not settle due to gravity but remain stably dispersed in the ink 150.

[0075] For example, the average particle size of the charged black particles 151 can be from 50 nm to 500 nm or from 100 nm to 250 nm. Within this range, the dispersion stability is excellent, and the charged black particles 151 have a high charge, resulting in excellent driving characteristics. When the average particle size is too small, particle aggregation occurs due to inter-particle interactions, and the dispersion stability of the charged hollow carbon black 151 decreases. When the average particle size of the charged black particles is too large, there may be a problem of the charged black particles 151 settling in the ink 150 due to gravity. When the average particle size of the charged black particles 151 is too large, the charge of the particles decreases, which may slow down the switching speed between wide-viewing-angle and narrow-viewing-angle modes.

[0076] The charged black particles 151 carry either a positive or negative charge. Therefore, when a voltage is applied to the first electrode 120a and the second electrode 120b, the charged black particles 151, uniformly dispersed in the solvent 153, accumulate near the first electrode 120a or the second electrode 120b due to the electric field formed between them. A detailed description of this will be provided below.

[0077] For example, the charged black particles 151 are negatively charged. Specifically, the negatively charged black particles 151 can be made from carboxylate groups (-COO-). - ), sulfonate (-SO3) - ) and sulfate (SO4) 2-Black particles with surface modification using one or more atomic groups from the group consisting of ) are used. For example, black particles modified with carboxylate groups are obtained by a simple process of adding black particles to nitric acid and / or sulfuric acid, reacting the black particles at a relatively low temperature of about 100°C, and then dispersing the black particles in solvent 153. The charged black particles 151 obtained as described above have a high surface charge. The high surface charge of the charged black particles 151 allows them to move more quickly by an electric field, thus improving bistability and enhancing the driving characteristics and stability of the viewing angle control film 100.

[0078] For example, based on the total weight of ink 150, the content of charged black particles 151 is between 0.1 wt% and 3.5 wt%. When the content of charged black particles 151 is too low, the light absorption effect will decrease. When the content of charged black particles 151 is too high, there is a problem that the brightness will decrease if the viewing angle control film 100 is applied to the display device.

[0079] The refractive index of the ink 150, which includes light-absorbing materials, is lower than that of the transparent resin layer 130. Ghosting, or overlapping of multiple images, may occur due to the refractive index difference between the ink 150 and the transparent resin layer 130, as described above. Charged high-refractive-index particles 152 are dispersed within the ink 150, which has a lower refractive index, to reduce the refractive index difference between the ink 150 and the transparent resin layer 130. Furthermore, the addition of charged high-refractive-index particles can suppress particle settling in the ink. This minimizes particle settling in the ink due to gravity.

[0080] For example, the charged high-refractive-index particles 152 may be one or more high-refractive-index particles selected from titanium dioxide, zirconium dioxide, and zinc oxide. These high-refractive-index particles have a high refractive index to reduce the refractive index difference between the ink 150 and the transparent resin layer 130. This minimizes ghosting. Preferably, for example, the high-refractive-index particles may be zinc oxide. Zinc oxide has the best optical properties, so when the viewing angle control film 100 is applied to a display device, ghosting can be minimized while maintaining high brightness.

[0081] For example, the refractive index of the high-refractive-index particles can be between 1.7 and 3 or between 1.8 and 2.1. Within this range, while maintaining the high transparency of the viewing angle control film 100, the refractive index difference between the ink 150 and the transparent resin layer 130 is reduced to minimize image distortion, such as ghosting. Specifically, when the refractive index of the high-refractive-index particles is in the range of 1.8 to 2.1, higher brightness can be achieved when the viewing angle control film 100 is applied to a display device.

[0082] The charged high-refractive-index particles 152 carry either a positive or negative charge. When the high-refractive-index particles are charged, they do not aggregate due to the repulsion between particles caused by the surface charge, but remain uniformly dispersed in the ink 150. Therefore, when the viewing angle control film 100 is applied to a display device, color inhomogeneity can be minimized while maintaining high brightness. When the high-refractive-index particles are uncharged, they are prone to aggregation, thereby increasing the reflective haze of the viewing angle control film 100 and reducing light transmittance.

[0083] The charged high-refractive-index particles 152 carry a charge opposite to that of the charged black particles 151. As described above, when a voltage is applied to the first electrode 120a and the second electrode 120b, the charged black particles 151 accumulate near the first electrode 120a or the second electrode 120b due to the electric field formed between them. At this time, when the charged high-refractive-index particles 152 and the charged black particles 151 move to the same electrode through the electric field, the moving speed of the charged black particles 151 decreases, thereby affecting the driving performance. Therefore, since the charged high-refractive-index particles 152 and the charged black particles 151 carry opposite charges, they will not move towards the same electrode when the electric field is formed.

[0084] For example, the charged high-refractive-index particles 152 carry a positive charge. For example, the charged high-refractive-index particles 152 can be high-refractive-index particles surface-modified with ammonium ions. Specifically, the charged high-refractive-index particles 152 can be high-refractive-index particles surface-modified with quaternary ammonium ions selected from hexadecyltrimethylammonium, tetradecyltrimethylammonium, octyltrimethylammonium, and dodecyltrimethylammonium. In this case, the charged high-refractive-index particles 152 are uniformly dispersed in the ink 150, and ghosting can be suppressed without reducing the optical properties of the viewing angle control film 100.

[0085] For example, the average particle size of the charged high-refractive-index particles 152 can be from 5 nm to 30 nm or from 8 nm to 15 nm. Within this range, the viewing angle control film 100 has the advantages of low reflectivity, high transmittance, and excellent driving characteristics. Regardless of whether an electric field is formed, the charged high-refractive-index particles 152 should be kept uniformly dispersed in the ink 150 to reduce the refractive index difference between the ink 150 and the transparent resin layer 130.

[0086] When the average particle size of the charged high-refractive-index particles 152 is too small, the particles may not be uniformly dispersed in the ink 150 due to inter-particle interactions, and may instead aggregate. Furthermore, as the particle size decreases, the ZETA potential increases to a positive value. Therefore, when a voltage is applied to the first electrode 120a and the second electrode 120b, the charged high-refractive-index particles 152 may not be uniformly dispersed, but may aggregate near the electrode where a negative voltage is applied. Therefore, the ghosting phenomenon may not be improved.

[0087] Furthermore, when the average particle size of the charged high-refractive-index particles 152 is too large, the light incident on the transparent resin layer 130 is scattered, thereby increasing the reflective haze of the viewing angle control film 100 and reducing its transmittance. When the average particle size of the charged high-refractive-index particles 152 is too large, the viscosity of the ink 150 increases, which may reduce the mobility of the charged black particles 151. Therefore, the driving characteristics and mode switching speed of the viewing angle control film 100 may decrease. Moreover, as the average particle size of the charged high-refractive-index particles 152 increases, the ZETA potential increases to a negative value. Therefore, when a voltage is applied to the first electrode 120a and the second electrode 120b, the charged high-refractive-index particles 152 will not disperse uniformly, but may aggregate near the electrode where the positive voltage is applied. Therefore, the ghosting phenomenon may not be improved.

[0088] For example, based on the total weight of ink 150, the content of charged high refractive index particles 152 is between 0.1 wt% and 4 wt%. When the content of charged high refractive index particles 152 is within the above range, the refractive index difference between ink 150 and transparent resin layer 130 is reduced, thereby improving the ghosting phenomenon. The refractive index of transparent resin layer 130 is greater than that of ink 150, and a predetermined amount or more of charged high refractive index particles 152 is added to ink 150, thereby reducing the refractive index difference between ink 150 and transparent resin layer 130. When the content of charged high refractive index particles 152 is too low, the increase in the refractive index of ink 150 is not significant, and the effect of improving color uniformity is not significant. Furthermore, when the content of charged high refractive index particles 152 is too high, the reflective haze of viewing angle control film 100 may increase. As a result, when viewing angle control film 100 is applied to a display device, the brightness may decrease. Furthermore, as the solid content in ink 150 increases, its viscosity also increases, potentially slowing down the switching speed between wide-viewing-angle and narrow-viewing-angle modes. Additionally, as the content of charged high-refractive-index particles 152 increases, the refractive index of ink 150 increases. When the content is excessive, the refractive index of ink 150 becomes greater than that of the transparent resin layer 130. Therefore, the refractive index difference between ink 150 and transparent resin layer 130 increases, which may not improve the ghosting phenomenon.

[0089] However, the content range of charged high-refractive-index particles 152 can vary depending on the type of high-refractive-index particles. The refractive index varies depending on the type of high-refractive-index particles, thus allowing the content range to be controlled accordingly. For example, using zinc oxide with a refractive index of 2.00 as the high-refractive-index particles, the content of charged high-refractive-index particles 152 can be 2 wt% to 3 wt% based on the total weight of ink 150, and within this range, excellent brightness and improved ghosting are observed. As another example, using titanium dioxide with a refractive index of 2.60 as the charged high-refractive-index particles, the content of charged high-refractive-index particles 152 can be 1.5 wt% to 2.3 wt% based on the total weight of ink 150.

[0090] Ink 150 may also include a dispersant. A dispersant having basic functional groups may be used. For example, the dispersant may be polyisobutylene succinimide represented by the following molecular formula 1.

[0091] [Molecular Formula 1]

[0092]

[0093] In formula 1, n is an integer from 5 to 500.

[0094] The amine groups of the dispersant represented by Formula 1 react with functional groups bonded to the surface of the charged black particles 151. The dispersant represented by Formula 1 forms a structure bonded to the surface of the charged black particles 151, thus surrounding the surface of the charged black particles 151. The dispersant represented by Formula 1 has a relatively long chain length, allowing it to surround the surface of the charged black particles 151 as a protective layer, thereby inhibiting particle aggregation. Furthermore, the dispersant represented by Formula 1 allows the negatively charged black particles 151 to stably maintain their charged state. Consequently, repulsive forces between particles are induced to minimize particle aggregation. Therefore, the dispersion characteristics of the charged black particles 151 are improved, the dispersion stability of the ink 150 is improved, and thus the driving characteristics of the viewing angle control film 100 are enhanced.

[0095] For example, based on the total weight of ink 150, the content of dispersant can be from 0.05 wt% to 5 wt%. When the content of dispersant is too low, the improvement in dispersion stability may be negligible. Dispersants have a relatively large molecular weight, so when too much dispersant is added, it may increase the viscosity of ink 150. When the viscosity of ink 150 increases, the movement of charged black particles 151 becomes difficult, which may reduce the driving characteristics of the viewing angle control film 100.

[0096] The ink 150 may also include a surfactant. For example, the surfactant may be a phosphate ester compound, but is not limited thereto. Specifically, for example, the surfactant may be selected from tricresyl phosphate and tributyl phosphate, but is not limited thereto. The surfactant increases the dielectric constant of the ink 150 to improve the response speed of the viewing angle control film 100.

[0097] The second electrode 120b is disposed on the transparent resin layer 130. Except that the second electrode 120b is disposed above the transparent resin layer 130, the second electrode 120b is substantially the same as the first electrode 120a described above. Furthermore, a second substrate member 110b is disposed on the second electrode 120b. Except that the second substrate member 110b is disposed on the second electrode 120b, the second substrate member 110b is substantially the same as the first substrate member 110a described above. Therefore, repeated descriptions will be omitted.

[0098] An adhesive layer ADH is disposed between the transparent resin layer 130 and the first electrode 120a. For example, the viewing angle control film 100 is manufactured by fabricating a first assembly consisting of a first substrate member 110a and a first electrode 120a, and a second assembly consisting of a second substrate member 110b, a second electrode 120b, and a transparent resin layer 130 in which ink 150 is contained within a plurality of receiving units 140, and then combining the first and second assemblies. In this case, after the ink 150 is injected into the plurality of receiving units 140, the first and second assemblies are bonded together using the adhesive layer ADH. However, this is not a limitation; the adhesive layer ADH may be disposed between the transparent resin layer 130 and the second electrode 120b, or it may be omitted depending on the manufacturing process or structure of the viewing angle control film 100.

[0099] For example, the thickness of the adhesive layer ADH can be from 1 μm to 100 μm, but is not limited to this.

[0100] For example, the adhesive layer ADH can be formed from materials selected from optically transparent adhesives (OCA), optically transparent resins (OCR), or pressure-sensitive adhesives (PSA), but is not limited thereto.

[0101] In the following text, reference will be made to Figure 3A and Figure 3B A more detailed description of the wide-view mode and narrow-view mode.

[0102] Figure 3A This is a schematic cross-sectional view of a view control membrane according to an exemplary embodiment of the present disclosure in a narrow view mode. Figure 3B This is a schematic cross-sectional view of a view control membrane according to an exemplary embodiment of the present disclosure in wide-view mode.

[0103] Reference Figure 3AWhen no electric field is formed between the first electrode 120a and the second electrode 120b, charged black particles 151 and charged high-refractive-index particles 152 are uniformly dispersed in solvent 152 and randomly distributed in each of the plurality of containment units 140. Since the charged black particles 151 are randomly dispersed in each of the plurality of containment units 140, some of the light incident on the plurality of containment units 140 can be absorbed by the charged black particles 151. That is, light incident at a predetermined angle or greater is blocked by the plurality of containment units 140. In other words, in the light incident from the lower part of the viewing angle control film 100a, light incident at a predetermined angle or greater relative to the front surface (z-axis) is absorbed by the charged black particles 151 dispersed in the plurality of containment units 140. Therefore, this light is not emitted to the outside of the viewing angle control film 100a. For example, in the light incident from the lower part of the viewing angle control film 100a, light incident at a first angle θ1 on the front surface (z-axis) is output to the outside of the viewing angle control film 100a. However, light incident at a second angle θ2 greater than the first angle will not be emitted to the outside. Therefore, light incident at a predetermined angle or greater is blocked to operate in narrow viewing angle mode.

[0104] Meanwhile, charged high refractive index particles 152 are uniformly dispersed in solvent 153 to reduce the refractive index difference between ink 150 and transparent resin layer 130, thereby suppressing the ghosting phenomenon that makes the image appear to overlap.

[0105] Reference Figure 3B When a voltage is applied between the first electrode 120a and the second electrode 120b to form an electric field, the charged black particles 151, which are randomly dispersed in the plurality of containment units 140, move to the electrodes through the electric field. That is, the charged black particles 151 move to the electrode to which the opposite voltage is applied according to their charged charge.

[0106] For example, when the charged black particles 151 are negatively charged, if a negative voltage is applied to the first electrode 120a and a positive voltage is applied to the second electrode 120b, the negatively charged black particles 151 move to the upper surface 142. The upper surface 142 is adjacent to the second electrode 120b to which a positive voltage is applied. Therefore, the charged black particles 151 are stacked from the upper surface 142 of the receiving unit 140 with a predetermined thickness. That is, in most areas outside the region adjacent to the upper surface 142 of the receiving unit 140 where the charged black particles 151 are stacked, there are almost no charged black particles 151. Therefore, the angle of light emitted to the outside of the viewing angle control film 100b is widened. Specifically, in the light incident from the lower part of the viewing angle control film 100b, not only light incident at a first angle θ1 relative to the front surface (z-axis), but also light incident at a second angle θ2 greater than the first angle is emitted to the outside. Therefore, with Figure 3ACompared to the previous method, the propagation angle of the light emitted to the outside of the viewing angle control film 100b is increased to enable operation in a wide viewing angle mode.

[0107] As another example, when the charged black particle 151 carries a negative charge, a positive voltage is applied to the first electrode 120a and a negative voltage is applied to the second electrode 120b, similar to... Figure 3B Works in wide-view mode. Repeated descriptions of it will be omitted.

[0108] To quickly switch from a narrow-viewing-angle mode to a wide-viewing-angle mode, the black particles 151 need to rapidly move to the electrode to which the opposite voltage is applied when an electric field is formed. For example, the negatively charged black particles 151 apply a negative voltage to the first electrode 120a, and when a positive voltage is applied to the second electrode 120b, the black particles 151 need to rapidly move to the upper surface 142. The upper surface 142 is adjacent to the second electrode 120b to which the positive voltage is applied. Therefore, the negatively charged black particles 151 need to have a negative charge amount to move rapidly under the driving voltage of the viewing angle control film 100b. For example, the charge amount of the negatively charged black particles 151 can be -25mV to -50mV. In this case, the driving voltage of the viewing angle control film 100b can be 10V to 60V. Within this range, when a voltage is applied to the first electrode 120a and the second electrode 120b, the charged black particles 151 move rapidly, resulting in excellent switching speed between the wide-viewing-angle mode and the narrow-viewing-angle mode, and excellent driving characteristics and stability of the viewing angle control film 100b.

[0109] Simultaneously, charged high-refractive-index particles 152 are added to ink 150, which has a refractive index lower than that of the transparent resin layer 130, so that the refractive index of ink 150 is controlled to be approximately equal to that of the transparent resin layer 130. Therefore, the refractive index difference between ink 150 and transparent resin layer 130 is significantly reduced, thereby minimizing ghosting phenomena. Thus, the charged high-refractive-index particles 152 need to remain uniformly dispersed in ink 150 regardless of the presence of an electric field.

[0110] For example, when the charged black particles 151 are negatively charged, the charged high-refractive-index particles 152 are positively charged (opposite to the charged black particles 151). However, when an electric field is applied, the positively charged high-refractive-index particles 152 are not attracted to the electrode to which a negative voltage is applied, but are instead uniformly dispersed in the ink 150. That is, even if a negative voltage is applied to the first electrode 120a and a positive voltage is applied to the second electrode 120b, the positively charged high-refractive-index particles 152 are not attracted to the lower surface 141 adjacent to the first electrode 120a to which a negative voltage is applied, but are instead relatively uniformly dispersed in the receiving unit 140. Therefore, regardless of whether an electric field is formed, the refractive index of the ink 150 and the refractive index of the transparent resin layer 130 remain equal, thereby improving the ghosting phenomenon.

[0111] The positively charged high-refractive-index particles 152 need to have a low amount of positive charge so that they are not attracted to the first electrode 120a, which is subjected to a negative voltage, when an electric field is formed. For example, the charge of the positively charged high-refractive-index particles 152 can be between +5mV and +11mV. In this case, the charged high-refractive-index particles 152 are not attracted to the electrode with the opposite voltage applied under the driving voltage of the viewing angle control film 100b, but can remain uniformly dispersed in the housing unit 140. Therefore, the ghosting phenomenon of the viewing angle control film 100b can be minimized.

[0112] When synthesizing high-refractive-index particles 152, the charge of the charged high-refractive-index particles 152 can be controlled by the pH of the solution. For example, when synthesizing zinc oxide particles using a zinc precursor, sodium hydroxide can be used to control the pH of the reaction solution in the range of 8 to 9. The charge of the thus prepared charged high-refractive-index particles 152 can be in the range of +5 mV to +11 mV.

[0113] The viewing angle is controlled by the width W1 of the lower surface 141 of the receiving unit 140, the width W2 of the upper surface 142, the distance D1 from the lower surface 141 to the upper surface 142 (i.e., the height of the receiving unit 140), the distances W3 and W4 between adjacent receiving units 140, and the tilt of the first connecting unit 143a and the second connecting unit 143b.

[0114] Reference Figure 2The width W1 of the lower surface 141 is 25 μm to 50 μm, and the width W2 of the upper surface 142 is 5 μm to 15 μm. Furthermore, the distance from the lower surface 141 to the upper surface 142, i.e., the height D1 of the receiving unit 140, can be 100 μm to 160 μm. The distance W3 between the lower surfaces 141 of adjacent receiving units 140 is 15 μm to 50 μm, and the distance W4 between the upper surfaces 142 is 25 μm to 60 μm. Within this range, a wider viewing angle can be provided in wide-viewing-angle mode without reducing brightness, and in narrow-viewing-angle mode, the propagation angle of the emitted light is small enough to provide a narrow viewing angle. Furthermore, the width W1 of the lower surface 141 is preferably formed to be greater than the width W2 of the upper surface 142. In this case, a wider viewing angle can be provided in wide-viewing-angle mode.

[0115] The angle θa formed by the first connecting unit 143a and the lower surface 141 and the angle θb formed by the second connecting unit 143b and the lower surface 141 can be between 90° and 120°. Within this range, a wide viewing angle can be provided in the wide viewing angle mode, and in the narrow viewing angle mode, the propagation angle of the emitted light is reduced to achieve a narrow viewing angle.

[0116] Despite Figure 1 , 2 In 3A and 3B, it is shown that the angle θa formed by the first connecting unit 143a and the lower surface 141 is equal to the angle θb formed by the second connecting unit 143b and the lower surface 141, which can be from 90° to 105°. However, this is only an example, and therefore this disclosure is not limited thereto. The angle θa formed by the first connecting unit 143a and the lower surface 141 and the angle θb formed by the second connecting unit 143b and the lower surface 141 can be different.

[0117] As described above, the upper surface 142 of each of the plurality of receiving units 140 is spaced apart from the second electrode 120b. For example, the distance D2 from the upper surface 142 to the second electrode 120b can be from 5 μm to 40 μm. A transparent resin layer 130 with insulating properties is formed in the space between the upper surface 142 and the second electrode 120b. Therefore, when the distance D2 is too long, the electric field strength at the same voltage will decrease, and the driving characteristics may be reduced.

[0118] Figure 4 This is a schematic cross-sectional view of a view control membrane according to another exemplary embodiment of the present disclosure.

[0119] In addition to the patterning of the first and second electrodes and the alteration of the structures of the first and second substrate members, Figure 4 The shown perspective t and Figure 1 and Figure 2The viewing angle control membrane 100 shown is largely the same. Therefore, repeated descriptions will be omitted. Even in Figure 4 The diagram shows that the first and second electrodes have patterned structures, but it is not limited to this. If desired, only either the first or second electrode may have a patterned structure.

[0120] Reference Figure 4 Multiple first patterned electrodes 220a are disposed below the adhesive layer ADH, and multiple second patterned electrodes 220b are disposed above the transparent resin layer 130.

[0121] Each of the plurality of first patterned electrodes 220a is configured to overlap with each of the plurality of receiving units 140.

[0122] Each of the plurality of first patterned electrodes 220a extends along a second direction (y-axis direction) perpendicular to the thickness direction (z-axis direction) and the first direction (x-axis direction). Therefore, each of the plurality of first patterned electrodes 220a has a linear shape extending along the second direction (y-axis direction).

[0123] The first base member 210a can be configured to cover the surface and sides of the plurality of first patterned electrodes 220a. That is, the first base member 210a is configured to cover the steps formed by the plurality of first patterned electrodes 220a.

[0124] Each of the plurality of second patterned electrodes 220b is configured to overlap with each of the plurality of first patterned electrodes 220a. Therefore, each of the plurality of second patterned electrodes 220b overlaps with each of the plurality of receiving units 140.

[0125] Similar to the first patterned electrode 220a, the second patterned electrode 220b has a line shape extending along a second direction (y-axis direction) perpendicular to the thickness direction (z-axis direction) and the first direction (x-axis direction).

[0126] The second base member 210b can be configured to cover the surface and sides of the plurality of second patterned electrodes 220b. That is, the second base member 210b is configured to cover the steps formed by the plurality of second patterned electrodes 220b.

[0127] For example, the widths of the plurality of first electrode patterns 220a and the plurality of second electrode patterns 220b can be from 5 μm to 60 μm. However, they are not limited thereto, and the width W1 of the lower surface 141 and / or the width W2 of the upper surface 142 can be varied according to the design.

[0128] like Figure 4As shown, when the electrodes are patterned to be configured as multiple patterned electrodes 220a and multiple patterned electrodes 220b, leakage current generated in the transparent resin layer 130 and the adhesive layer ADH can be minimized. Because leakage current is minimized, the mobility of charged black particles 151 in the multiple containment units 140 is further improved, and the driving characteristics and mode switching speed of the viewing angle control film can be further improved.

[0129] The viewing angle control film 100 disclosed herein is used in organic light-emitting display devices or liquid crystal display devices.

[0130] Figure 5 This is a schematic cross-sectional view of an organic light-emitting display device according to an exemplary embodiment of the present disclosure. (Refer to...) Figure 5 An organic light-emitting display device 500 according to an exemplary embodiment of the present disclosure includes an organic light-emitting display panel PNL1 and a viewing angle control film 100. The viewing angle control film 100 includes a first substrate member 110a, a first pattern electrode 120a, a transparent resin layer 130, a second pattern electrode 120b, and a second substrate member 110b. Figure 5 The viewing angle control film 100 in the organic light-emitting display device 500 shown is... Figure 1 and Figure 2 The viewing angle control membrane 100 shown is largely the same. Therefore, repeated descriptions will be omitted.

[0131] The organic light-emitting display panel PNL1 includes an organic light-emitting layer to display images using light emitted therefrom. For example, the organic light-emitting display panel PNL1 includes a substrate, thin-film transistors, an anode, an organic light-emitting stack, a cathode, and an encapsulation layer.

[0132] The substrate is a base component that supports the various components of the organic light-emitting display panel (PNL1) and is formed of an insulating material. For example, the substrate can be a glass substrate or a plastic substrate. For example, the plastic substrate can be selected from polyimide, polyethersulfone, polyethylene terephthalate, and polycarbonate, but is not limited to these.

[0133] A thin-film transistor (TFT) is disposed on a substrate. The TFT includes a gate, an active layer, a source, and a drain. For example, the active layer is disposed on the substrate, and a gate insulating layer is disposed on the active layer to insulate the active layer from the gate. Furthermore, an interlayer insulating layer is disposed on the substrate to insulate the gate from the source and drain. The source and drain, in contact with the active layer, are formed on the interlayer insulating layer. A planarization layer may be disposed on the TFT. The planarization layer planarizes the upper portion of the TFT. The planarization layer may include contact holes electrically connecting the TFT and the anode.

[0134] The anode is disposed on the planarization layer. The anode is the component that provides holes to the organic light-emitting layer and is formed of a conductive material with a high work function. The anode can be divided for each sub-pixel. The cathode is disposed on the anode. The cathode can be formed of a metallic material with a low work function to smoothly supply electrons to the organic light-emitting layer. The cathode is formed as a single layer on the anode without patterning. That is, the cathode is not divided for each sub-pixel area, but is formed as a continuous monolayer. The organic light-emitting layer is disposed between the anode and the cathode. The organic light-emitting layer is the layer where electrons and holes couple to emit light. An encapsulation layer that minimizes degradation of the display panel due to moisture or oxygen and planarizes the upper surface of the organic light-emitting display panel PNL1 is disposed on the cathode.

[0135] A viewing angle control film 100 is disposed on an organic light-emitting display panel PNL1. For example, the viewing angle control film 100 is disposed on the encapsulation layer of the organic light-emitting display panel PNL1.

[0136] A viewing angle control film 100 is disposed on an organic light-emitting display panel PNL1 to provide a narrow viewing angle mode and a wide viewing angle mode. The narrow viewing angle mode provides a narrow viewing angle to allow a user to see the image formed by light emitted from the organic light-emitting layer of the organic light-emitting display panel PNL1. The wide viewing angle mode provides a wide viewing angle to allow others nearby to see the image. The configuration of the viewing angle control film 100, the narrow viewing angle mode, and the wide viewing angle mode are consistent with the above reference. Figure 1 , 2 Since 3A and 3B are described the same, their repeated descriptions will be omitted.

[0137] Figure 6 This is a schematic cross-sectional view of a liquid crystal display device according to an exemplary embodiment of the present disclosure. (Refer to...) Figure 6 The liquid crystal display device 600 according to an exemplary embodiment of the present disclosure includes a backlight unit BLU, a viewing angle control film 100, and a liquid crystal display panel PNL2. The viewing angle control film 100 includes a first substrate member 110a, a first pattern electrode 120a, a transparent resin layer 130, a second pattern electrode 120b, and a second substrate member 110b. Figure 6 The viewing angle control film 100 in the liquid crystal display device 600 shown is... Figure 1 and Figure 2 The viewing angle control membrane 100 shown is largely the same. Therefore, repeated descriptions will be omitted.

[0138] The backlight unit (BLU) includes multiple light sources to provide light to the liquid crystal display panel (PNL2). These light sources are electrically connected to a printed circuit board to be turned on or off. For example, the light sources can be light-emitting diodes (LEDs), which offer advantages such as high efficiency, high brightness, and low power consumption, but are not limited to these.

[0139] The backlight unit (BLU) includes a light diffuser plate disposed on multiple light sources to converge and diffuse light emitted from the multiple light sources, thereby allowing light to be uniformly incident on the liquid crystal display panel (PNL2).

[0140] A reflective layer that reflects light generated by the light source onto the front surface is disposed on the rear surface of the backlight unit (BLU).

[0141] The liquid crystal display panel PNL2 is disposed on the backlight unit BLU. The liquid crystal display panel PNL2 includes a liquid crystal layer and controls the light transmittance of the liquid crystal to display images.

[0142] For example, the liquid crystal display panel PNL2 includes a lower substrate, an upper substrate, a lower polarizing plate, and an upper polarizing plate.

[0143] The lower substrate supports various components that constitute the liquid crystal display panel PNL2. On the lower substrate, thin-film transistors, pixel electrodes electrically connected to the thin-film transistors, and a common electrode that forms an electric field together with the pixel electrodes are disposed. Therefore, the lower substrate can be called a thin-film transistor substrate. A liquid crystal layer comprising liquid crystal molecules is disposed on the thin-film transistor substrate.

[0144] The upper substrate and the lower substrate are opposite each other. A color filter layer and a black matrix layer are disposed on the upper substrate. The color filter layer selectively transmits light with a specific wavelength. Light emitted from the backlight unit (BLU) passes through the liquid crystal layer and the color filter to be converted into light with various colors. The black matrix layer prevents the thin-film transistors disposed on the lower substrate from being visible to the outside of the liquid crystal display device 600.

[0145] A lower polarizer is disposed on the lower surface of the lower substrate to polarize the light emitted from the backlight unit BLU toward the liquid crystal display panel PNL2. An upper polarizer is disposed on the upper surface of the upper substrate to polarize the light emitted to the outside of the liquid crystal display panel PNL2.

[0146] A viewing angle control film 100 is disposed between the backlight unit BLU and the liquid crystal display panel PNL2. The viewing angle control film 100 controls the propagation angle of the light emitted from the backlight unit BLU to provide a wide viewing angle mode and a narrow viewing angle mode.

[0147] Specifically, the viewing angle control film 100 is disposed on the backlight unit BLU to provide a narrow viewing angle mode and a wide viewing angle mode. In the narrow viewing angle mode, the viewing angle of light incident from the backlight unit BLU is controlled to be narrow, making the image displayed on the liquid crystal display panel PNL2 visible to the user. In the wide viewing angle mode, the viewing angle of light incident from the backlight unit BLU is controlled to be wide, providing a wide viewing angle to allow people in the vicinity to see the image displayed on the liquid crystal display panel PNL2. The configuration of the viewing angle control film 100, the narrow viewing angle mode, and the wide viewing angle mode are consistent with the above reference. Figure 1 , 2Since 3A and 3B are described the same, their repeated descriptions will be omitted.

[0148] The effects of this disclosure will be described in more detail below with reference to embodiments and comparative examples. However, the following embodiments are described for illustrative purposes only, and the scope of this disclosure is not limited thereto.

[0149] [Example 1]

[0150] 1. Preparation of charged high-refractive-index particles

[0151] 30 ml of a 4M NaOH aqueous solution and 20 ml of a 1M ZnCl2 aqueous solution were stirred and mixed at room temperature. Next, in a separate container, 50 ml of the pre-prepared mixed solution (pH 8-9), 45 ml of distilled water, and 5 ml of 0.2M hexadecyltrimethylammonium bromide (CTAB) were added, and the mixture was stirred at room temperature for 1 hour and 30 minutes. Then, stirring was stopped, and the mixture was heat-treated at 100°C for 4 hours. The resulting white precipitate was washed with distilled water at least three times and dried at 100°C to prepare charged zinc oxide particles.

[0152] 2. Ink Preparation

[0153] 10g of carbon black (density 1.8g / cm³) 3 Up to 2.1 g / cm 3 Add the precipitate to 100 ml of 65 wt% nitric acid and stir at 100 °C for 24 hours to allow the reaction to proceed. After the reaction is complete, centrifuge at 7500 rpm for 15 minutes, then separate the precipitate and wash with distilled water. Next, dry at 120 °C for 24 hours to obtain the product containing carboxylate-COO. - Surface-modified carbon black particles were prepared. Next, Isopar L (density 0.764 g / cm³) solvent was prepared in a separate container. 3 Afterwards, 0.2 wt% polyisobutylene succinimide (trade name T151) was added. Next, 0.1 g of surface-modified carbon black particles were added to 15 g of solvent-dispersant mixture, followed by ultrasonic treatment for 2 hours. Next, based on 100 wt% of the composition, charged zinc oxide prepared as described above was added at a concentration of 3 wt% to prepare the ink. As a reference, the charge (ZETA voltage) of the charged carbon black particles was confirmed to be -30 mV to -35 mV, the average particle size of the charged zinc oxide particles was 10.2 nm, and the charge (ZETA voltage) was +9.6 mV.

[0154] 3. Preparation of viewing angle control film

[0155] A pair of electrode films were prepared by depositing a 25 μm thick ITO electrode on the entire surface of a 35 μm thick PET film. Next, a resin composition comprising 90 wt% polyurethane acrylate, 3 wt% diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, 2 wt% mold release agent, and 5 wt% tricresyl phosphate (or tributyl phosphate) was prepared. Multiple receiving units were formed on one electrode of the pre-prepared electrode films using an embossing process (or mastering process), and the ink prepared above was injected into the multiple receiving units to form a composite material. Figure 1 The same transparent resin layer is shown. At this point, the width of the lower surface of the receiving unit is 32 μm, the width of the upper surface is 8 μm, and the height is 140 μm. Next, an electrode film with the transparent resin layer is bonded to another electrode film using an optically transparent adhesive to prepare a viewing angle control film.

[0156] [Comparative Example 1]

[0157] Except for omitting the step of adding charged zinc oxide particles in the ink preparation process of Example 1, the ink was prepared using the same method as in Example 1. An angle control film was then prepared using the ink prepared as described above, in the same manner as in Example 1.

[0158] [Comparative Example 2]

[0159] Except that uncharged zinc oxide particles were added instead of charged zinc oxide particles during the ink preparation process of Example 1, the ink was prepared using the same method as in Example 1. The viewing angle control film was then prepared using the ink prepared as described above, using the same method as in Example 1.

[0160] [Experimental Example 1]

[0161] Brightness was measured after the viewing angle control films according to Example 1 and Comparative Examples 1 and 2 were bonded to the display panel. Brightness was measured using a SpectraDuo PR-680, and the results are shown below. Figure 7 Furthermore, it was determined whether ghosting spots were generated in the display device including the viewing angle control film according to Example 1 and Comparative Example 1.

[0162] Figure 7 This is a graph showing the brightness measurement results of a display device including the viewing angle control film according to Example 1 and Comparative Examples 1 and 2. Figure 8 This is a photograph showing that no ghosting phenomenon occurs in a display device including a viewing angle control film according to Embodiment 1. Figure 9 This is a photograph showing the ghosting phenomenon in a display device including the viewing angle control film according to Comparative Example 1.

[0163] First, refer to Figure 7 as well as Figure 8It was confirmed that no ghosting was observed in the display device including the viewing angle control film according to Example 1 and the display quality was excellent.

[0164] Reference Figure 7 as well as Figure 9 It was confirmed that in a display device including the viewing angle control film according to Comparative Example 1, even with excellent brightness, ghosting was observed, resulting in a reduction in display quality.

[0165] In other words, ghosting can be improved when using ink containing high-refractive-index particles with a charge opposite to that of the charged black particles. This is because the introduction of charged high-refractive-index particles reduces the difference in refractive index between the ink and the transparent resin layer. For reference, in the viewing angle control film according to Example 1 and Comparative Example 1, the refractive index of the transparent resin layer is 1.498, and the refractive index of the ink according to Comparative Example 1 is 1.437. This is attributed to the difference in refractive index between the ink and the transparent resin layer according to Comparative Example 1. Figure 9 As shown, a ghosting phenomenon occurs. In contrast, the refractive index of the ink according to Example 1 is 1.491, which is almost equal to the refractive index of the transparent resin layer. Therefore, when the viewing angle control film according to Example 1 is included, as... Figure 8 As shown, the results demonstrate the improvement in the ghosting phenomenon.

[0166] At the same time, refer to Figure 7 In Comparative Example 2, which included uncharged high refractive index particles, it was confirmed that the refractive index difference between the ink and the transparent resin layer could be reduced, but the brightness was lower than that of Example 1.

[0167] As can be seen from the summary of Experiment 1, when using ink containing high-refractive-index particles with the opposite charge to the charged black particles, the ghosting phenomenon is improved while maintaining high brightness.

[0168] To demonstrate the effect of varying the amount of charged high-refractive-index particles, the inventors prepared inks and viewing angle control films according to Reference Examples 1 and 2 as described below.

[0169] [Reference Example 1]

[0170] Except that the concentration of charged zinc oxide particles was changed from 3 wt% to 4 wt% in Example 1, the ink was prepared using the same method as in Example 1. A viewing angle control film was then prepared using the ink prepared as described above, in the same manner as in Example 1.

[0171] [Reference Example 2]

[0172] Except that the concentration of charged zinc oxide particles was changed from 3 wt% to 5 wt% in Example 1, the ink was prepared using the same method as in Example 1. A viewing angle control film was then prepared using the ink prepared as described above, in the same manner as in Example 1.

[0173] [Experimental Example 2]

[0174] The transmittance and haze of the viewing angle control films according to Example 1, Reference Example 1, and Reference Example 2 were measured. Furthermore, the viewing angle control films according to Example 1, Reference Example 1, and Reference Example 2 were bonded to an organic light-emitting display panel, and the brightness (wide viewing angle mode) and mode switching speed were measured. The results are shown in Table 1 below.

[0175] [Table 1]

[0176] Example 1 Reference Example 1 See Example 2 Electrolyzed zinc oxide content 3wt% 4wt% 5wt% Light transmittance 80.8％ 79.9％ 78％ Reflective haze 0.72 1.2 1.85 Brightness (wide viewing angle mode) 87.9％ 82.4％ 78.8％ Mode switching speed 2.7 seconds 3.1 seconds 3.3 seconds

[0177] Referring to Table 1, it can be seen that when the content of charged zinc oxide particles in the ink exceeds 3 wt%, the transmittance of the viewing angle control film decreases to less than 80%, and the reflection haze increases. Therefore, it is confirmed that in the organic light-emitting display device including the viewing angle control film according to Reference Examples 1 and 2, the brightness is worse and the mode switching speed is slower in wide viewing angle mode compared to Example 1.

[0178] Furthermore, charged zinc oxide was added during ink preparation to control the refractive index to be similar to that of the transparent resin layer, which has a high refractive index. However, it was confirmed that when the concentration of charged zinc oxide particles in the ink exceeded 3.5 wt%, the refractive index of the ink increased to 1.51 or higher. Therefore, when the concentration of charged zinc oxide particles in the ink exceeds 3.5 wt%, the refractive index becomes higher than that of the transparent resin layer, resulting in ghosting.

[0179] In other words, to suppress ghosting while maintaining high light transmittance of the viewing angle control film, it is necessary to control the content range of charged high-refractive-index particles. Furthermore, it was confirmed that optimal results were obtained when charged zinc oxide particles were added at an amount of 2 wt% to 3 wt% based on the total weight of the ink.

[0180] [Experiment Example 3]

[0181] To verify the effectiveness of adjusting the average particle size of charged high-refractive-index particles in the ink, the inventors prepared inks identical to those in Example 1, but with different average particle sizes of charged high-refractive-index particles. Furthermore, viewing angle control films were prepared using the inks described above. The average particle size and charge (ZETA potential) of the charged high-refractive-index particles in each ink, as well as the refractive index and particle settling velocity of the ink, were measured using a Lumisizer dispersion analyzer.

[0182] Furthermore, the viewing angle control film prepared as described above was bonded to an organic light-emitting display panel to fabricate an organic light-emitting display device, and the brightness of the organic light-emitting device (30° side view) was measured in both wide-viewing-angle mode and narrow-viewing-angle mode. The results are shown in Table 2 below. Figure 10 .

[0183] Furthermore, it was determined whether ghosting spots were generated in the organic light-emitting display device prepared as described above, and the results are shown in... Figure 11 middle.

[0184] Figure 10 This is a graph showing the brightness measurement results of a display device including the viewing angle control film according to Example 1 and Comparative Examples 1, 3 to 5.

[0185] Figure 11 These are photographs showing whether ghosting occurs in a display device including the viewing angle control film according to Example 1 and Comparative Examples 1, 3 to 5.

[0186] [Table 2]

[0187]

[0188] Refer to Table 2 and Figure 10 and Figure 11 It was confirmed that the refractive index (1.498) of the ink according to Example 1 is almost the same as that of the transparent resin layer, thus producing almost no ghosting. The display device including the ink according to Example 1 exhibits an excellent 30° side brightness of 104.6% in wide viewing angle mode and 0.90% in narrow viewing angle mode. Therefore, it can be confirmed that the display device is well driven in both narrow and wide viewing angle modes.

[0189] Meanwhile, in the ink of Comparative Example 3, the average particle size of the charged zinc oxide particles was 200 nm. In this case, it was confirmed that even when zinc oxide particles were prepared under the same conditions as in Example 1, the particles were not positively charged, but rather negatively charged. (From Table 2 and...) Figure 10 It can be seen that the driving characteristics of the display device, including the viewing angle control film, have deteriorated. Furthermore, referring to... Figure 11 It was confirmed that the ghosting phenomenon was caused by the difference in refractive index between the transparent resin layer and the ink.

[0190] In Comparative Example 4, where the average particle size of the charged zinc oxide particles was 62 nm, the charge was +3.2 mV and the particles carried a charge opposite to that of the charged black particles. However, as can be seen from Table 10, the charge was confirmed to be insufficient, resulting in poorer driving characteristics compared to Example 1. Furthermore, as... Figure 11 As shown, the ghosting phenomenon was further confirmed.

[0191] Furthermore, in Comparative Example 5, where the average particle size of the charged zinc oxide particles was 3.1 nm, it was confirmed that the (+) charge was higher than that of Example 1. Figure 10 It can be seen that the driving characteristics are worse than those in Example 1. Furthermore, as... Figure 11 The image further confirms the presence of ghosting.

[0192] Meanwhile, in Comparative Example 1, which did not include charged zinc oxide particles, it was confirmed that the refractive index was the lowest and the particle settling velocity was the highest. That is, adding charged high-refractive-index particles increases the refractive index and suppresses particle settling. Referring to Table 2, it was confirmed that the particle settling velocity was the slowest in the ink according to Example 1. Therefore, according to Example 1, the particles in the ink remain in a stable dispersed state and do not settle due to gravity.

[0193] Exemplary embodiments of this disclosure can also be described as follows:

[0194] According to one aspect of this disclosure, a viewing angle control film includes: a first substrate member; a first electrode disposed on the first substrate member; a transparent resin layer disposed on the first electrode and having a plurality of receiving units; a second electrode disposed on the transparent resin layer; and a second substrate member disposed on the second electrode, wherein each of the plurality of receiving units contains an ink comprising charged black particles, charged high refractive index particles and a solvent, and the charged black particles have a charge opposite to that of the charged high refractive index particles.

[0195] Each of the plurality of receiving units may be formed opposite to the second electrode, may be configured to be spaced apart from each other along a first direction perpendicular to the thickness direction of the transparent resin layer, and may extend along a second direction perpendicular to the thickness direction and the first direction.

[0196] Each of the plurality of receiving units may include a lower surface opposite to the first electrode, an upper surface opposite to the lower surface, and a connecting unit connecting the lower surface and the upper surface.

[0197] The upper surface can be spaced apart from the second electrode, and the distance from the upper surface to the second electrode can be from 5 μm to 40 μm.

[0198] The distance from the bottom surface to the top surface can be from 100 μm to 160 μm.

[0199] The width of the lower surface can be from 25 μm to 50 μm, and the width of the upper surface can be from 5 μm to 15 μm.

[0200] The black particles can be one or more selected from the group consisting of carbon nanotubes and carbon black.

[0201] Charged black particles can be produced by selecting carboxylate groups (-COO). -), sulfonate (-SO3) - ), sulfate (SO4 2- ) and hydrofluoric acid ions (F - Black particles that undergo surface modification from one or more atomic groups in a group consisting of )

[0202] The refractive index of high-refractive-index particles can range from 1.7 to 3.0.

[0203] High refractive index particles can be one or more selected from the group consisting of titanium dioxide, zirconium dioxide, and zinc oxide.

[0204] Charged high-refractive-index particles can be high-refractive-index particles with surface modification using ammonium ions.

[0205] The average particle size of charged black particles can be from 50 nm to 500 nm, and the average particle size of charged high refractive index particles can be from 5 nm to 30 nm.

[0206] The charge of the charged black particles can range from -25mV to -50mV, and the charge of the charged high-refractive-index particles can range from +5mV to +11mV.

[0207] Based on the total weight of the ink, the content of charged black particles can be from 0.1 wt% to 3.5 wt%, and the content of charged high refractive index particles can be from 0.1 wt% to 4 wt%.

[0208] The ink may also include one or more surfactants selected from the group consisting of tricresyl phosphate, tributyl phosphate, and polyisobutylene succinimide.

[0209] The transparent resin layer may include acrylic resin, release agent, and surfactant.

[0210] When no voltage is applied to the first and second electrodes, charged black particles and charged high refractive index particles can be uniformly dispersed in each of the multiple containment units, and the viewing angle control film can operate in a narrow viewing angle mode. When a voltage is applied to the first and second electrodes, the charged black particles can aggregate toward the upper surface of the multiple containment units, the charged high refractive index particles can be dispersed in the multiple containment units, and the viewing angle control film can operate in a wide viewing angle mode.

[0211] According to one aspect of this disclosure, a display device includes: a display panel; and a viewing angle control film disposed above or below the display panel, wherein the viewing angle control film is the aforementioned viewing angle control film.

[0212] The display panel may be a liquid crystal display panel and may also include a backlight unit disposed below the display panel, and the viewing angle control film may be disposed between the liquid crystal display panel and the backlight unit.

[0213] The display panel can be an organic light-emitting display panel, and the viewing angle control film can be placed above the organic light-emitting display panel.

[0214] Although exemplary embodiments of the present disclosure have been described in detail with reference to the accompanying drawings, the present disclosure is not limited thereto and may be implemented in many different forms without departing from the technical concept of the present disclosure. Therefore, the exemplary embodiments of the present disclosure are provided for illustrative purposes only and are not intended to limit the technical concept of the present disclosure. The scope of the technical concept of the present disclosure is not limited thereto. Therefore, it should be understood that the above exemplary embodiments are illustrative in all respects and do not limit the present disclosure. The scope of protection of the present disclosure should be interpreted based on the appended claims, and all technical concepts within the scope of their equivalents should be understood to fall within the scope of the present disclosure.

Claims

1. A viewing angle control film, comprising: a first base member; a first electrode provided on the first base member; a transparent resin layer provided on the first electrode and having a plurality of accommodation units; a second electrode provided on the transparent resin layer; and a second base member provided on the second electrode, wherein an ink including a charged black particle, a charged high refractive index particle, and a solvent is accommodated in each of the plurality of accommodation units, and the charged black particle has an opposite charge to the charged high refractive index particle, wherein the high refractive index particle has a refractive index of 1.7 to 3.0, wherein when no voltage is applied to the first electrode and the second electrode, the charged black particle and the charged high refractive index particle exist as being uniformly dispersed within each of the plurality of accommodation units, and the viewing angle control film operates in a narrow viewing angle mode, and wherein when a voltage is applied to the first electrode and the second electrode, the charged black particle is aggregated toward an upper surface of the plurality of accommodation units, the charged high refractive index particle is dispersed in the plurality of accommodation units, and the viewing angle control film operates in a wide viewing angle mode. Each of the plurality of accommodation units is formed so as to be opposed to the second electrode, is provided so as to be spaced apart from each other along a first direction perpendicular to a thickness direction of the transparent resin layer, and extends along a second direction perpendicular to the thickness direction and the first direction.

2. The viewing angle control film according to claim 1, wherein Each of the plurality of accommodation units includes a lower surface opposed to the first electrode, the upper surface opposed to the lower surface, and a connection unit connecting the lower surface and the upper surface.

3. The viewing angle control film according to claim 1, wherein The upper surface is spaced apart from the second electrode, and a distance from the upper surface to the second electrode is 5 μm to 40 μm.

4. The viewing angle control film according to claim 3, wherein A distance from the lower surface to the upper surface is 100 μm to 160 μm.

5. The viewing angle control film according to claim 3, wherein A width of the lower surface is 25 μm to 50 μm, and a width of the upper surface is 5 μm to 15 μm.

6. The viewing angle control film according to claim 3, wherein The black particle is one or more selected from the group consisting of a carbon nanotube and carbon black.

7. The viewing angle control film according to claim 1, wherein The high refractive index particle is one or more selected from the group consisting of titanium dioxide, zirconium dioxide, and zinc oxide.

8. The viewing angle control film according to claim 1, wherein The charged black particles are black particles surface-modified with one or more atomic groups selected from the group consisting of carboxylate (-COO - ), sulfonate (-SO3 - ), sulfate (SO4 2- ), and hydrofluoride (F - ).

9. The viewing angle control film according to claim 1, wherein The charged high refractive index particle is a high refractive index particle surface-modified with an ammonium.

10. The viewing angle control film according to claim 1, wherein An average particle diameter of the charged black particle is 50 nm to 500 nm, and an average particle diameter of the charged high refractive index particle is 5 nm to 30 nm.

11. The viewing angle control film according to claim 1, wherein A charge amount of the charged black particle is -25 mV to -50 mV, and a charge amount of the charged high refractive index particle is +5 mV to +11 mV.

12. The viewing angle control film according to claim 1, wherein A content of the charged black particle is 0.1 wt% to 3.5 wt%, and a content of the charged high refractive index particle is 0.1 wt% to 4 wt%, based on a total weight of the ink.

13. The viewing angle control film according to claim 1, wherein The ink further includes one or more surfactants selected from the group consisting of tricresyl phosphate and tributyl phosphate and polyisobutylene succinimide.

14. The viewing angle control film according to claim 1, wherein The transparent resin layer includes an acrylic resin, a release agent, and a surfactant.

15. The viewing angle control film according to claim 1, wherein 16. A display device, comprising: a display panel; and a viewing angle control film according to any one of claims 1 to 15. ​ A viewing angle control film is disposed above or below the display panel, The viewing angle control film is the viewing angle control film according to any one of claims 1 to 15.

17. The display device of claim 16, wherein, The display panel is a liquid crystal display panel, and the display device further comprises a backlight unit disposed below the display panel, and the viewing angle control film is disposed between the liquid crystal display panel and the backlight unit.

18. The display device of claim 16, wherein, The display panel is an organic light emitting display panel, and the viewing angle control film is disposed above the organic light emitting display panel.

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