KR102402800B1 - Cover window and display device comprising the same - Google Patents

Abstract

A cover window for a display according to an embodiment includes a cover window for a display including a flexible substrate including one surface and the other surface opposite to the one surface, the display comprising: a first soft layer disposed on the one surface of the flexible substrate; a second soft layer disposed on the other surface of the flexible substrate; and a hard layer disposed on at least one of the first soft layer and the second soft layer, the hard layer having a lower elastic modulus than the first soft layer and the second soft layer, the cover window for the display The maximum height roughness (Rt) on one surface in the first direction is 0.2 μm to 0.4 μm.

Description

Cover window for display and display device including same

The embodiment relates to a cover window for a display and a display device including the same.

Recently, in various electronic products, interest in various electronic products such as a flexible cover window or a display device to which a foldable cover window is applied, for example, a mobile phone and a notebook computer, is increasing.

Such a flexible touch window or a foldable touch window may be bent or folded in one direction or another using a cover window for a foldable display.

In addition, recently, interest in a stretchable cover window that can be applied to various new environments that can be bent and stretched at the same time is increasing.

In order to implement such a flexible, foldable or stretchable display, the cover window for a display may use a flexible substrate rather than a rigid material. In addition, in order to supplement the strength of the flexible substrate, a functional layer such as a hard coating layer may be disposed on one or both surfaces of the flexible substrate.

For example, in order to realize stretchability, a cover window for a display is arranged with a soft layer and a hard layer in order to simultaneously implement elasticity and strength on a flexible substrate, and accordingly, the stretchable cover window is bent. It is possible to prevent cracks due to stress caused by bending along with the characteristics, and to implement the stretch characteristics of the cover window.

In the process of manufacturing the flexible substrate that is the base substrate of the cover window, a surface waviness having a specific period and height generated by a filling material that is a manufacturing material of the flexible substrate and the like may be formed.

When the soft layer and the hard layer are respectively laminated on the flexible substrate having such a surface corrugation, surface irregularities having a period and a height similar to the surface corrugation of the flexible substrate may be formed on the outer surfaces of the soft layer and the hard layer on the flexible substrate, , such a surface uneven shape may be visually recognized by a user outside the cover window of the display device.

Accordingly, since the user sees the surface uneven shape of the cover window on the screen of the display device, the user's overall visibility may be impaired by the surface uneven shape.

Accordingly, there is a need for a cover window for a display having a new structure capable of improving the visibility of a user by reducing the surface irregularities of the cover window for a display, and a display device including the same.

An embodiment is to provide a cover window for a display having improved visibility and surface quality.

A cover window for a display according to an embodiment includes a cover window for a display including a flexible substrate including one surface and the other surface opposite to the one surface, the display comprising: a first soft layer disposed on the one surface of the flexible substrate; a second soft layer disposed on the other surface of the flexible substrate; and a hard layer disposed on at least one of the first soft layer and the second soft layer, the hard layer having a lower elastic modulus than the first soft layer and the second soft layer, the cover window for the display The maximum height roughness (Rt) on one surface in the first direction is 0.2 μm to 0.4 μm.

The cover window for a display according to the embodiment may have improved visibility and surface quality.

In detail, when the cover window for a display according to an embodiment is coated with a soft layer and a hard layer implementing hardness and flexibility on a flexible substrate, the soft layer and the hard layer are not directly coated on the flexible substrate, but on another member Since it adheres to the flexible substrate after imprinting, the influence of the surface roughness and surface undulation of the flexible substrate can be prevented.

Accordingly, the cover window for a display according to the embodiment can reduce the height deviation of the surface roughness, can have improved surface quality, and can reduce the difference in light and shade according to the surface waveform, thereby preventing deterioration of visibility can do.

1 is a diagram illustrating a perspective view of a cover window for a display according to an embodiment.
FIG. 2 is a view showing a cross-sectional view taken along area AA′ of FIG. 1 .
3 to 6 are views for explaining a manufacturing process of a cover window for a display according to an embodiment.
7 and 8 are views illustrating measurement images of surface roughness measured through a scanning electron microscope.
9 and 10 are views illustrating two-dimensional graphs according to the measurement images of the surface roughness of FIGS. 7 and 8 , respectively.
11 and 12 are diagrams illustrating frequency distribution tables of surface roughness according to the measurement images of surface roughness of FIGS. 7 and 8 , respectively.
13 to 15 are diagrams for explaining the surface quality of a cover window according to an embodiment and a comparative example.
16 is a diagram illustrating a cross-sectional view of a display device to which a cover window according to an embodiment is applied.
17 is a diagram illustrating an example of a display device according to embodiments.

In the description of embodiments, each layer (film), region, pattern or structure is “on” or “under” the substrate, each layer (film), region, pad or patterns. The description of being formed in " includes all those formed directly or through another layer. The standards for the upper/above or lower/lower layers of each layer will be described with reference to the drawings.

In addition, when a certain part is said to be "connected" with another part, it includes not only the case where it is "directly connected" but also the case where it is "indirectly connected" with another member interposed therebetween. In addition, when a part "includes" a certain component, this means that other components may be further provided, rather than excluding other components, unless otherwise stated.

1 to 2 , the cover window 1000 for a display according to the embodiment may include the flexible substrate 100 .

The flexible substrate 100 may include a transparent material. The flexible substrate 100 may include a flexible material. For example, the flexible substrate 100 may include a transparent plastic material.

For example, the flexible substrate 100 may include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide (PI), polycarbonate (PC), polystyrene (PS), polyethersulfone (PES), and silicone. It may include at least one material among resins.

In detail, the flexible substrate 100 may include polyimide (PI). Since polyimide (PI) has excellent elongation rate and heat resistance, and excellent restoring force after bending compared to other materials, it may be suitably applied as a base substrate for a stretchable cover window for a display.

The thickness T1 of the flexible substrate 100 may be about 50 μm or less. In detail, the thickness of the flexible substrate 100 may be about 30 μm to about 50 μm.

When the thickness of the flexible substrate 100 is less than about 30 μm, the overall strength of the cover window may be lowered, and thus the reliability of the display device to which the cover window is applied may be reduced.

In addition, when the thickness of the flexible substrate 100 exceeds about 50 μm, cracks occur in the flexible substrate when the display device to which the cover window is applied is bent in one direction due to the thickness of the flexible substrate 100 . Therefore, the reliability of the display device may be deteriorated.

The flexible substrate 100 may include one surface 100a and the other surface 100b opposite to the one surface 100a.

In FIG. 1 , the flexible substrate 100 is illustrated as having a rectangular shape, but the implementation is not limited thereto, and the flexible substrate 100 may include a curved surface or have various polygonal shapes, depending on the use and shape of the applied display device. It may be formed in a shape.

X-axis (first axis), Y-axis (second axis), and Z-axis (third axis) directions may be defined in the flexible substrate 100 . For example, the X axis may correspond to a horizontal direction of the flexible substrate, the Y axis may correspond to a vertical direction of the flexible substrate, and the Z axis may correspond to a thickness, ie, a height direction, of the flexible substrate.

A surface waviness may be formed on the surface of the flexible substrate 100 . The surface corrugation may be defined as the curvature of the surface appearing at intervals larger than the intervals of surface roughness. The surface undulation may be caused by various displacements occurring during the process, such as vibration, magnetic anomalies between the machine tool and the sample, or non-uniformity of heat treatment of materials.

In detail, wavy patterns may be formed on the surface of the flexible substrate 100 with a period of about 3 mm to about 5 mm. Such a surface undulation may be defined as an intrinsic characteristic of the flexible substrate that is naturally formed during the manufacturing process of the flexible substrate 100 .

In detail, in order to manufacture the flexible substrate, a filler or the like may be included. These filling materials can be filled for extending, reinforcing, and forming processability of flexible substrates.

However, it may be included in the flexible substrate by such a filler material and cause surface undulation. In addition, when the amount or shape of the filling material is changed in order to prevent the surface corrugation, the values of intrinsic properties of the flexible substrate may be changed together.

When light is transmitted through the cover window by applying the cover window to the display device, bending of light may occur in the portion where the surface waveform is formed and in the portion where the surface waveform is not formed. Contrast differences may occur between the formed portion and the non-formed portion.

Surfaces of one surface and the other surface of the flexible substrate 100 may have surface roughness. Surface roughness can be defined as minute curves appearing at small intervals on a certain processed surface, and the shape and size may appear differently depending on the processing method or finishing method during the material processing process.

The surface roughness may be defined as a concave-convex pattern formed on the surfaces of one surface and the other surface of the flexible substrate 100 . The size of the surface roughness may be defined in various ways.

For example, the magnitude of the surface roughness may be defined by the values of the Ra, Ry, Rt and Rz parameters. Each of the parameters of the surface roughness may be defined as the magnitude of the surface roughness, and in particular, Ry and Rt are magnitudes related to the height deviation of the surface roughness, and may be related to the surface flatness.

Ra is an arithmetic mean roughness, and may be defined as a roughness value obtained by obtaining an average value after raising the lower part of the data extracted by the reference length from the surface roughness curve to the top of the average line.

In addition, Ry and Rt are maximum height roughness, and may be defined as the maximum roughness value indicating the height from the lowest point to the highest point of the surface roughness curve on the basis of the average line within the reference length or the average length.

In addition, Rz is a 10-point average roughness. From the data extracted as much as the reference length from the surface roughness curve, it is defined as a value added by averaging the values of the five highest points in the order of the highest point and the values of the five lowest points in the order of the lowest point based on the average line. can be

For example, the maximum height roughness Rt and Ry among the surface roughness values of the flexible substrate 100 may have a period of about 1 mm to about 2 mm, and may have a size of about 0.6 μm or more.

The maximum height roughness is a value obtained by calculating the deviation of the surface height. As the value increases, the surface flatness may decrease, and as the value decreases, the surface flatness may be improved.

The surface roughness curve of the flexible substrate 100 may be formed to extend in the X-axis or the Y-axis direction. In detail, the surface roughness curve of the flexible substrate 100 may be formed in an extension direction of the surface undulation of the flexible substrate, that is, in the same or similar direction to the longitudinal direction of the surface undulation, ie, a direction corresponding to the surface roughness curve of the flexible substrate 100 .

Such surface roughness and/or surface undulation of the flexible substrate may impair the user's visibility in the cover window. That is, when disposing other substrates or layers on the flexible substrate, the other substrates and layers are also directly affected by the surface roughness and/or surface undulation of the flexible substrate, so that even in the finally manufactured cover window, in the flexible substrate It may have a surface roughness and/or surface undulation of a similar magnitude to the resulting surface roughness and/or surface undulation. Accordingly, when the user uses the display device outside the display device to which the cover window is applied, the contrast difference due to the surface roughness and/or the surface waveform is recognized, thereby impairing the user's visibility.

Accordingly, in the cover window according to the embodiment, by controlling the processes of the soft layer and the hard layer to be described below, the surface roughness and/or the surface waveform of the cover window caused by the flexible substrate is reduced, thereby improving the visibility of the user. can do it

Referring to FIG. 2 , the soft layer 200 may be disposed on at least one of one surface and the other surface of the flexible substrate 100 . In detail, the soft layer 200 may be disposed on at least one of one surface and the other surface of the flexible substrate 100 .

In detail, the first soft layer 210 and the second soft layer 220 may be respectively disposed on one surface and the other surface of the flexible substrate. That is, the first soft layer 210 may be disposed on one surface of the flexible substrate 100 , and the second soft layer 220 may be disposed on the other surface of the flexible substrate 100 .

A thickness T2 of the first soft layer 210 and the second soft layer 220 may be about 10 μm or less. In detail, the thickness T2 of the first soft layer 210 and the second soft layer 220 may be about 5 μm to about 10 μm.

The first soft layer 210 and the second soft layer 220 may be formed to have the same or different thicknesses within the thickness range.

When the thickness T2 of the first soft layer 210 and the second soft layer 220 exceeds about 10 μm, the display device to which the cover window is applied is rotated in one direction by the thickness of the soft layer. When bending or stretching, cracks may be generated in the cover window, thereby reducing reliability of the display device.

In addition, disposing the thickness T2 of the first soft layer 210 and the second soft layer 220 to be less than about 5 μm may be difficult to implement, and the first soft layer 210 due to process defects. ) and the surface roughness of the second soft layer 220 may increase, thereby reducing overall visibility of the cover window.

The first soft layer 210 and the second soft layer 220 may be formed by the following process.

In detail, referring to FIG. 3 , after preparing a carrier glass 150 , the first resin composition R1 serving as a material of the first soft layer may be coated on the carrier glass 150 . The first resin composition (R1) may include a material having an elastic modulus of about 2 GPa or more.

The first resin composition (R1) may include a resin material, a photoinitiator, a crosslinking monomer, and an additive.

In detail, the resin material, the photoinitiator, the crosslinking monomer, and the additive may be mixed with a solvent such as propylene glycol monomethyl ether (PGME) to form a resin composition.

The resin material may include at least one of an acrylic resin and a urethane-based resin. For example, the resin material may include urethane acrylate.

In addition, the photoinitiator may include a photoinitiator material that cures the crosslinkable functional group.

In addition, the first resin composition (R1) may include a crosslinking monomer. For example, the first resin composition (R1) may further include a crosslinking monomer having at least one functional group selected from an acrylate group, an epoxy group, and an oxetane group. The hardness of the first soft layer may be improved by the crosslinking monomer.

In addition, the first resin composition (R1) may further include an additive. For example, the first resin composition (R1) may further include silica particles (SiO2). The silica particles may be dispersed and disposed in the first resin composition (R1).

The hardness of the first soft layer may be improved by the silica particles.

The silica particles may have a particle size of nano units. The silica particles may have a particle diameter of about 100 nm or less. In detail, the silica particles may have a particle diameter of about 10 nm to 100 nm.

When the particle diameter of the silica particles exceeds about 100 nm, dispersibility of the silica particles may be reduced, light is refracted by the silica particles, and haze of the cover window may be increased.

The silica particles may be included in an amount of about 10 wt% to about 65 wt% based on the total of the first resin composition (R1). In detail, the silica particles may be included in an amount of 30 wt% to about 65 wt% based on the total of the first resin composition (R1).

When the silica particles are included in less than about 10% by weight, the hardness of the first soft layer may be reduced. In addition, when the silica particle is included in an amount exceeding about 65% by weight, hardness may be improved, but a crack may be generated in the first soft layer when bending or pulling the cover window due to deterioration of bending properties.

In addition, the additive may further include a charge-discharge material. As the first resin composition (R1) includes a charge-discharge material, it is possible to block the inflow of foreign substances that may be introduced into the first resin composition (R1). Accordingly, after curing the first resin composition (R1), it is possible to prevent deterioration of the surface quality due to such foreign substances.

For example, the antistatic material may include conductive carbon such as carbon black, conductive polymers such as polyaniline, polypyrrole and PEDOT, nano metal such as silver, and the like, and may be included in the form of particles.

The antistatic material may be included in an amount of about 2 wt% or less based on the total of the first resin composition (R1). When the antistatic material is included in excess of about 2% by weight based on the total of the first resin composition (R1), the resistance of the first soft layer 210 is increased by the antistatic material, so that the cover window is touched When applied to a touch device such as a window, the touch sensitivity may be deteriorated thereby.

Next, the flexible substrate 100 is disposed on the first soft layer 210 , and the first resin composition R1 is cured to form the flexible substrate 100 and the first soft layer 210 . can be glued. Accordingly, the first soft layer 210 may be disposed on one surface of the flexible substrate 100 .

On the other hand, the surface of the first soft layer 210 , that is, the surface opposite to the surface where the first soft layer 210 contacts the flexible substrate 100 has a surface roughness lower than the surface roughness of the flexible substrate 100 . can have That is, since the first soft layer 210 is imprinted on the carrier glass 150 and then comes in contact with the flexible substrate 100 , the surface of the first soft layer 210 is the flexible substrate 100 . It is not affected by the surface roughness of the carrier glass 150 and is affected by the surface roughness of the carrier glass 150 .

The carrier glass 150 does not have a surface roughness similar to that of the flexible substrate 100 , that is, the carrier glass 150 may have a smaller surface roughness than the flexible substrate 100 .

That is, the first soft layer 210 is not imprinted on the flexible substrate 100 , but is imprinted on one surface of the carrier glass 150 having a smaller surface roughness than the flexible substrate 100 . Then, since it adheres to the flexible substrate 100 , the surface roughness of the first soft layer 210 may have a surface roughness similar to that of the carrier glass 150 .

Next, referring to FIG. 4 , a second soft layer 220 may be disposed on the other surface of the flexible substrate 100 .

In detail, referring to FIG. 4 , after preparing the release member 170 , the second resin composition R2 , which is the material of the second soft layer 220 , may be applied on one surface of the release member 170 . have. The second resin composition R2 as the material of the second soft layer 220 may include the same or similar material as the first resin composition R1 as the material of the first soft layer 210 described above. have.

For example, the second resin composition R2 serving as the material of the second soft layer 220 may include a material having an elastic modulus of about 2 GPa or more.

In addition, the second resin composition R2 serving as a material of the second soft layer 220 may include a resin material, a photoinitiator, a crosslinking monomer, and an additive. The resin material, the photoinitiator, and the crosslinking monomer may include the same or similar material to the first soft layer 220 .

However, when the antistatic material included as an additive is included in the first soft layer 210 , it may not be included in the second soft layer 220 . That is, the antistatic material as an additive may be included in only one soft layer 210 of the first soft layer 210 and the second soft insect 220 .

When the antistatic material is included in both the first soft layer 210 and the second soft layer 220 , the sheet resistance on the surfaces of the first soft layer 210 and the second soft layer 220 is increases, and thus, when the cover window is applied to a touch device that implements a touch or the like, the touch sensitivity may be reduced thereby.

In detail, in order for the antistatic material to perform an antistatic function, a resistance of about 10 ¹⁰ Ω is required. Accordingly, the overall resistance value of the cover window may be increased according to the amount of the antistatic material. Accordingly, when the cover window is applied to a touch device implementing a touch, etc., the touch due to the interference phenomenon due to the resistance Sensitivity may be reduced. For example, when the resistance of the cover window exceeds about 10 ⁶ Ω, interference may occur and touch sensitivity may be reduced.

That is, when the antistatic material is included in both the first soft layer 210 and the second soft layer 220 , the resistance of the cover window is increased by the antistatic material, and thus the touch sensitivity is caused by interference. may be lowered.

Accordingly, the antistatic material may be included such that the cover window has a resistance value of about 10 ⁶ Ω or less, specifically, about 10 ¹ Ω to 10 ⁶ Ω. The release member 170 may include polyethylene terephthalate (PET), etc. of plastic material. After imprinting and coating the second resin composition R2 on one surface of the release member 170 , the release member may be disposed on the other surface of the flexible substrate 100 .

Alternatively, after applying a separate resin material on one surface of the release member 170 and curing it to form a resin layer, imprinting and applying a second resin composition (R2) on one surface of the resin layer, By disposing the release member on the other surface of the flexible substrate 100 , the second flexible layer 220 may be finally arranged on the other surface of the flexible substrate 100 .

On the other hand, the surface of the second soft layer 220 , that is, the surface opposite to the surface where the second soft layer 220 contacts the flexible substrate 100 has a surface roughness lower than the surface roughness of the flexible substrate 100 . can have That is, the second soft layer 220 is imprinted on the release member 170 having a smaller surface roughness than the surface roughness of the flexible substrate 100 and then comes in contact with the flexible substrate 100 , so that the second soft layer 220 is The surface of the soft layer 220 is not affected by the surface roughness of the flexible substrate 100 , but is affected by the surface roughness of the release member 170 .

The size of the surface roughness of the release member 170 or the resin layer may be smaller than that of the flexible substrate 100 .

That is, the second soft layer 220 is not imprinted on the flexible substrate 100 , but on one surface of the release member 17 or the resin layer having a smaller surface roughness than the flexible substrate 100 . After being imprinted on the substrate, since it adheres to the flexible substrate 100, the surface roughness of the second soft layer 210 may have a surface roughness similar to that of the release member 170 or the resin layer. .

A hard layer 300 may be disposed on the surface of the first soft layer 210 . The hard layer 300 may include a material having a smaller elastic modulus than that of the first soft layer 210 and the second soft layer 220 . The elastic modulus of the hard layer 300 may be about 1.5 GPa or less.

The first soft layer 210 and the second soft layer 220 may include the same or similar material. In detail, the first soft layer 210 and the second soft layer 220 may include the same or similar material.

The hard layer 300 may be disposed on the soft layer to improve durability by preventing scratch resistance of the cover window.

Meanwhile, the hard layer 300 may be disposed on any one of the first soft layer 210 and the second soft layer 220 . When the hard layer 300 is disposed on both the first soft layer 210 and the second soft layer 220, the elongation may be reduced and it may be difficult to apply to the stretchable window.

The thickness T3 of the hard layer 300 may be about 15 μm or less. In detail, the thickness T3 of the hard layer 300 may be about 5 μm to about 15 μm.

When the thickness T3 of the hard layer 300 is less than about 5 μm, overall durability of the cover window is deteriorated, and thus the cover window cannot be effectively protected from external impact.

In addition, when the thickness T3 of the hard layer 300 exceeds about 15 μm, when the display device to which the cover window is applied by the thickness of the hard layer 300 is bent in one direction, it is applied to the cover substrate. Cracks may occur, and elongation and restoring force may decrease, making it difficult to implement a stretchable touch window.

The hard layer 300 may include at least one of a siloxane-based resin and an epoxy-based resin material.

The hard layer 300 may be formed by the following process.

Referring to FIG. 5 , after removing the release member 170 and/or the resin layer disposed on the second soft layer 220 , the material of the hard layer on one surface of the second soft layer 220 . A third resin composition (R3) to become can be applied.

The third resin composition (R3), which is the material of the hard layer, contains a photoinitiator, a crosslinking monomer and an additive together with a siloxane-based resin or epoxy-based resin material, such as propylene glycol monomethyl ether (PGME). It can be formed by mixing with a solvent.

Next, as shown in FIG. 6 , the carrier glass 150 disposed on the lower surface of the first soft layer 210 is removed, and a separate functional layer capable of protecting the hard layer 300 from external impact and impurities. By disposing 400 on the hard layer 300, a final cover window for a display may be manufactured. The functional layer 400 may include an anti-glare layer, an anti-reflection layer, and/or an anti-fingerprint layer to simultaneously implement an anti-reflection or anti-fingerprint function while protecting the cover window for a display.

A cover window for a display according to an embodiment including the first soft layer 210 , the second soft layer 220 , and the hard layer 300 disposed on one surface and the other surface of the flexible substrate 100 , respectively may have a surface roughness of a certain size extending in a specific direction, for example, in the same or similar direction to an extension direction of a surface wave formed on the flexible substrate 100 .

For example, the maximum height roughness Rt and Ry among the surface roughness values of the cover window for a display according to the embodiment may have a period of about 1 mm or less and about 0.5 μm or less. In detail, the maximum height roughness (Rt, Ry) of the surface roughness values of the cover window for a display according to the embodiment has a period of about 1 mm or less, and may be about 0.2 μm to about 0.4 μm.

In addition, the arithmetic mean roughness (Ra) of the surface roughness values of the cover window for a display according to the embodiment may be about 0.05 μm to 0.1 μm.

In addition, the 10-point average roughness Rz among surface roughness values of the cover window for a display according to the embodiment may be about 0.2 μm to 0.3 μm.

That is, when the surface waveform and the surface roughness of the flexible substrate 100 are formed to extend in the X-axis direction of the flexible substrate 100 , the surface roughness of the cover window for the display is the X-axis of the flexible substrate 100 . direction, the period is about 1 mm or less, and may be about 0.2 μm to about 0.4 μm.

In addition, when the surface undulations and surface roughness of the flexible substrate 100 are formed to extend in the Y-axis direction of the flexible substrate 100 , the surface roughness of the cover window for the display is the Y-axis of the flexible substrate 100 . direction, the period is about 1 mm or less, and may be about 0.2 μm to about 0.4 μm.

The cover window for the display may be defined as a composition of a flexible substrate, 1 and 2 soft layers, and a hard layer. Alternatively, the display cover window may be defined by including a flexible substrate, 1 and 2 soft layers, a hard layer, and a separate functional layer 400 disposed on the hard layer and/or the first soft layer.

When the cover window for display is defined as a composition of a flexible substrate, 1, 2 soft layers, and a hard layer, the cover window for a display is defined as a flexible substrate, 1, 2 soft layers, a hard layer, and the hard layer and/or the agent When it is defined as a separate functional layer 400 disposed on one soft layer, the surface roughness of the functional layer may be maintained the same as or similar to that of the following hard layer. In detail, the surface of the hard layer 300, that is, , the surface of the surface opposite to the contact surface of the hard layer 300 and the second soft layer 220 may be similar to the size of the surface roughness of the second soft layer 220 . For example, the maximum height roughness Rt and Ry among the surface roughness values of the hard layer 300 may have a period of about 1 mm or less and about 0.5 μm or less. In detail, the maximum height roughness (Rt, Ry) of the surface roughness values of the hard layer 300 has a period of about 1 mm or less, and may be about 0.2 μm to about 0.4 μm.

In addition, the arithmetic mean roughness Ra among the surface roughness values of the hard layer 300 may be about 0.05 μm to 0.1 μm. In addition, the 10-point average roughness Rz among the surface roughness values of the hard layer 300 may be about 0.2 μm to 0.3 μm.

That is, when the surface undulations and surface roughness of the flexible substrate 100 are formed to extend in the X-axis direction of the flexible substrate 100 , the surface roughness of the hard layer 300 is the X of the flexible substrate 100 . It extends axially, has a period of about 1 mm or less, and may be from about 0.2 μm to about 0.4 μm.

In addition, when the surface undulations and surface roughness of the flexible substrate 100 are formed to extend in the Y-axis direction of the flexible substrate 100 , the surface roughness of the hard layer 300 is the Y of the flexible substrate 100 . It extends axially, has a period of about 1 mm or less, and may be from about 0.2 μm to about 0.4 μm.

The cover window for a display according to the embodiment may have improved visibility and surface quality. That is, since the soft layer and the hard layer disposed on the flexible substrate are not directly disposed on the flexible substrate, but are indirectly disposed using a separate member, when the soft layer and the hard layer are disposed on the flexible substrate, the soft layer and since the hard layer is not directly affected by the surface roughness and surface corrugation of the flexible substrate, it is possible to remove the surface corrugation resulting from the flexible substrate and reduce the surface roughness.

Therefore, when a user views the cover window for a display from the outside, since an unnecessary pattern is not visually recognized, visibility may be improved, and surface roughness may be reduced, thereby improving surface quality.

Hereinafter, the present invention will be described in more detail through cover windows for displays according to embodiments and comparative examples. These embodiments are merely presented as examples in order to explain the present invention in more detail. Therefore, the present invention is not limited to these examples.

Example One

Soft layers including urethane acrylate were coated on both sides of a substrate including polyimide.

First, a resin material including urethane acrylate was coated on one surface of the glass, and then the polyimide substrate and the resin material were adhered. Then, the resin material was cured using UV light to form one soft layer on one surface of the polyimide substrate.

Then, after coating a resin material including urethane acrylate on one surface of a polyethylene terephthalate (PET) substrate, the polyimide substrate and the resin material were adhered. Then, the resin material was cured using UV light to form two soft layers on the other surface of the polyimide substrate.

Then, after removing the polyethylene terephthalate (PET) substrate, a resin material containing an epoxy resin is applied on the second soft layer, dried by heat, and cured using UV to cure the second soft layer on the surface of the A hard layer was formed on the to prepare a cover window for a display.

Next, after removing the glass from the first soft layer, the surface roughness, visibility, and transmittance of the cover window for a display were measured.

At this time, the surface roughness of the cover window for display was measured using an atomic force microscope (AFM) in an area of 1 mm × 1 mm among the area of the cover window.

In detail, after fixing the cover window to the scanning probe microscope, the van der Waals force acting between the tip and the surface of the cover window is detected in a 1 mm × 1 mm area of the surface of the cover window by scanning the surface of the cover window to cover the cover. The surface roughness of the window can be measured.

In addition, the visibility difference was measured by using a Xe lamp to project the cover window for a display from a distance of about 1 m.

comparative example

Soft layers including urethane acrylate were coated on both sides of a substrate including polyimide.

Unlike the embodiment, a resin material containing urethane acrylate is directly coated on both sides of a substrate containing polyimide, and then the resin material is cured using UV to first and second surfaces on both sides of the polyimide substrate. A soft layer was formed.

Then, a resin material containing an epoxy resin is applied on the second soft layer, dried by heat, and cured using UV to form a hard layer on the surface of the second soft layer to form a cover window for a display. prepared.

Then, the surface roughness, visibility, and transmittance of the cover window for a display were measured in the same manner as in Examples.

Ra (μm) Rz (μm) Example 0.0659 0.2747 comparative example 0.1534 0.5171

polyimide comparative example Example Whether the surface waveform is visible poet poet not admitted

polyimide comparative example Example Transmittance (%) 88.6 90.1 91.6

7 (Comparative Example) and 8 (Example) are views showing measurement images of surface roughness measured through a scanning electron microscope, and FIGS. 9 (Comparative Example) and 10 (Example) are respectively FIGS. 7 and It is a view showing a two-dimensional graph in the X-axis direction in the evaluation length according to the measurement image of the surface roughness of Fig. 8, and Figs. 11 (comparative example) and 12 (example) are the surface roughness of Figs. It is a figure showing the frequency distribution table of the X-axis direction of the surface roughness according to the measurement image of .

7 and 9 , it can be seen that, in the cover window for a display according to the comparative example, the maximum height roughness of the surface roughness in the X-axis direction is about 0.5 μm or more. That is, since the cover window for a display according to the comparative example is directly affected by the surface roughness of the flexible substrate when the soft layer and the hard layer are disposed on the flexible substrate, the surface roughness of the flexible substrate as shown in FIGS. 7 and 9 . It can be seen that the height deviation is similar to the height deviation of .

Also, referring to FIG. 11 , it can be seen that in the cover window for a display according to the comparative example, roughness patterns having different heights are evenly distributed, that is, the surface flatness of the cover window is non-uniform.

On the other hand, referring to FIGS. 8 and 10 , it can be seen that the maximum height roughness of the surface roughness in the X-axis direction of the cover window for a display according to the embodiment is about 0.5 μm or less. That is, in the cover window for a display according to the embodiment, when the soft layer and the hard layer are disposed on the flexible substrate, they are coated irrespective of the surface roughness of the flexible substrate and then adhered to the flexible substrate. It can be seen that the height deviation is smaller than the height deviation of the surface roughness of the substrate.

Also, referring to FIG. 12 , it can be seen that, in the cover window for a display according to the embodiment, when only a roughness pattern having a specific height is distributed, that is, the surface flatness of the cover window is uniform.

Also, referring to Table 1, it can be seen that both the arithmetic mean roughness Ra and the 10-point average roughness Rz of the cover window for a display according to the embodiment are reduced compared to the cover window for a display according to the comparative example.

That is, it can be seen that the size of the overall surface roughness of the cover window for a display according to the embodiment is reduced compared to the cover window for a display according to the comparative example.

Therefore, since the cover window for a display according to the embodiment can implement a small maximum height roughness on one surface, the surface flatness of the cover window for a display can be made uniform, and the surface quality of the cover window can be improved.

13 to 15 are photographs in which the visibility of the cover window for a display is measured in Comparative Examples and Examples, respectively.

In detail, FIG. 13 is a photograph showing a photograph of the polyimide itself, FIG. 12 is a photograph according to a comparative example, and FIG. 15 is a photograph illustrating a photograph according to an embodiment.

Referring to FIGS. 13 and 14 and Table 2, it can be seen that the cover window for a display according to the comparative example has a similar contrast to that of the polyimide substrate, which is a flexible substrate. That is, the cover window for a display according to the comparative example is directly affected by the surface waveform of the flexible substrate when the soft layer and the hard layer are disposed on the flexible substrate. can

On the other hand, referring to FIGS. 15 and 2 , it can be seen that the cover window for a display according to the embodiment has a small difference in contrast compared to the cover window for a display according to the flexible substrate and the comparative example. That is, when the soft layer and the hard layer are disposed on the flexible substrate, the cover window for a display according to the embodiment is coated irrespective of the surface waveform of the flexible substrate and then adheres to the flexible substrate. It can be seen that there is a small difference in contrast compared to the difference in light and darkness of the flexible substrate.

Accordingly, it can be seen that the cover window for a display according to the embodiment has a small contrast compared to the cover window for a display according to the comparative example, and thus has improved visibility.

In addition, referring to Table 3, it can be seen that the cover window for a display according to the embodiment has improved transmittance compared to the cover window for a display according to the comparative example.

That is, since the cover window for a display according to the embodiment has a reduced surface roughness compared to the comparative example, it can have improved transmittance by reducing the refraction of light due to the surface roughness and the surface waveform, and thus, for the display according to the embodiment When the cover window is applied to a display device, improved luminance may be realized.

That is, the polyimide substrate has a refractive index of about 1.5 or more, but as the display cover window according to the embodiment has a refractive index of about 0.5 to 1.4, a decrease in transmittance due to refraction of light can be prevented.

Hereinafter, a display device including a cover window for a display according to the embodiments described above will be described with reference to FIG. 16 . In the description of the display device according to the embodiment, the same or similar contents to the cover window according to the above-described embodiments will be omitted, and the same reference numerals will be given to the same components.

Referring to FIG. 16 , in the display device according to the embodiment, the decoration layer 500 and the reinforcing layer 600 are disposed under the cover window 1000 and the cover substrate 1000 , and the reinforcing layer 600 is disposed under the reinforcing layer 600 . It may include a polarizing layer 700 and a touch panel 810 to be formed, an adhesive layer 900 disposed under the touch panel 810 , and a display panel 820 disposed under the adhesive layer 900 .

The cover window 1000 may include an effective area AA and an invalid area UA. A display may be displayed in the effective area AA, and a display may not be displayed in the ineffective area UA disposed around the effective area AA.

The decoration layer 500 may be disposed under the cover window 1000 . In detail, the decoration layer 500 may be disposed on the ineffective area UA. In detail, the decoration layer 500 may be disposed in contact with the cover window 1000 on the ineffective area UA.

The decoration layer 500 may be formed by coating a material having a predetermined color so that the wiring electrode disposed on the ineffective area and the printed circuit board connecting the wiring electrode to an external circuit cannot be seen from the outside. can

The decoration layer 500 may have a color suitable for a desired appearance, for example, black or white including black or white pigment. Alternatively, various color colors such as red and blue may be expressed by using various color films.

In addition, a desired logo may be formed on the decoration layer 500 in various ways. The decoration layer 500 may be formed by deposition, printing, wet coating, or the like.

The decoration layer 500 may be arranged in at least one layer or more. For example, the decoration layer 500 may be disposed as one layer or at least two layers having different widths.

The reinforcing layer 600 may be disposed under the cover window 1000 . In detail, the reinforcing layer 600 may be disposed on the effective area AA and the ineffective area UA. In detail, the reinforcing layer 600 may be disposed in contact with the cover window 1000 on the effective area AA, and may be disposed in contact with the decoration layer 500 on the ineffective area UA.

The reinforcing layer 600 may flatten the lower surface of the cover window 1000 on which the decoration layer 500 is disposed. That is, the reinforcing layer 600 is disposed while enclosing the decoration layer 500 on the lower surface of the cover window 1000 , so that a step according to the decoration layer 500 may be removed. That is, the reinforcing layer 600 may be a planarization layer.

A polarization layer 700 and a touch panel 810 may be disposed under the reinforcing layer 600 .

The polarizing layer 700 may be a polarizing film. The polarizing layer 700 may be a colored film. For example, the polarizing layer 700 may be a black film. The thickness of the polarizing layer 700 may be about 5 μm or less. In detail, the thickness of the polarizing layer 700 may be about 2 μm or less.

The polarizing layer 700 may include an alignment layer and a liquid crystal dye layer on the alignment layer. The liquid crystal dye layer is composed of liquid crystal molecules to which two dyes having different colors are attached, and since the liquid crystal molecules in the liquid crystal dye layer have dichroism, they absorb light vibrating in the stretching direction and vibrate in the vertical direction. Light may have a function of transmitting. In addition, the dichroic dye entering the liquid crystal dye layer may include iodine.

A touch panel 810 may be disposed under the polarization layer 700 . The touch panel 810 may include a sensing electrode. For example, the touch panel 810 may include a first sensing electrode and a second sensing electrode extending in a direction crossing each other.

Accordingly, the position of the input device (eg, a finger or a stylus pen) may be sensed in the effective area or the like. In detail, when an input device such as a finger is in contact with the touch surface of the cover window 1000 , a difference in capacitance is generated by the first and second sensing electrodes at the portion where the input device is in contact, and the difference occurs can be detected as a contact position

A display panel 820 may be disposed under the touch panel 810 . An adhesive layer 900 may be disposed between the touch panel 810 and the display panel 820 , and the touch panel 810 and the display panel 820 may be bonded to each other by the adhesive layer 900 .

The display panel 820 may include a liquid crystal display panel or an organic light emitting display panel. For example, the display panel 820 may include an organic light emitting display panel.

In detail, the display panel 820 may include an organic light emitting display panel including a self-luminous device that does not require a separate light source. For example, in the display panel 800 , a thin film transistor may be formed on a substrate, and an organic light emitting diode contacting the thin film transistor may be formed. The organic light emitting device may include an anode, a cathode, and an organic light emitting layer formed between the anode and the cathode. In addition, the organic light emitting device may further include another substrate serving as an encapsulation substrate for encapsulation.

The cover window for a display according to the embodiment may have improved visibility and surface quality.

In detail, when the cover window for a display according to an embodiment is coated with a soft layer and a hard layer implementing hardness and flexibility on a flexible substrate, the soft layer and the hard layer are not directly coated on the flexible substrate, but on another member Since it adheres to the flexible substrate after imprinting, the influence of the surface roughness and surface undulation of the flexible substrate can be prevented.

Accordingly, the cover window for a display according to the embodiment can reduce the height deviation of the surface roughness, can have improved surface quality, and can reduce the difference in contrast according to the surface waveform, thereby preventing the deterioration of visibility can do,

Hereinafter, an example of a display device to which the cover substrate according to the above-described embodiments is applied will be described with reference to FIG. 17 .

Referring to FIG. 17 , as an example of a display device, a mobile terminal is illustrated. The mobile terminal may include an effective area and an invalid area. In the effective area, a touch signal may be sensed by a touch of a finger or the like, and a command icon pattern unit and a logo may be formed in the ineffective area.

Also, a display apparatus including a cover window for a display according to an embodiment may include flexible and stretchable devices that are bent, folded, or stretched. Accordingly, a display apparatus including the same may be a flexible device apparatus. Accordingly, the user may bend or bend it by hand. Such a flexible and stretchable device device may be applied to a wearable touch such as a smart watch.

In addition, although not shown in the drawings, a display device including a cover window for a display according to an embodiment is applied to a vehicle and implements various stretching and restoration characteristics, regardless of the shape and location of the vehicle's interior. A display device can be implemented in the area

Features, structures, effects, etc. described in the above-described embodiments are included in at least one embodiment of the present invention, and are not necessarily limited to only one embodiment. Furthermore, features, structures, effects, etc. illustrated in each embodiment can be combined or modified for other embodiments by those of ordinary skill in the art to which the embodiments belong. Accordingly, the contents related to such combinations and modifications should be interpreted as being included in the scope of the present invention.

In addition, although the embodiments have been described above, these are merely examples and do not limit the present invention, and those of ordinary skill in the art to which the present invention pertains are exemplified above in a range that does not depart from the essential characteristics of the present embodiment. It can be seen that various modifications and applications that have not been made are possible. For example, each component specifically shown in the embodiments may be implemented by modification. And the differences related to these modifications and applications should be construed as being included in the scope of the present invention defined in the appended claims.

Claims (9)

a flexible substrate including one surface and the other surface opposite to the one surface;
a first soft layer disposed on the one surface of the flexible substrate;
a second soft layer disposed on the other surface of the flexible substrate; and
and a hard layer disposed on at least one of the first soft layer and the second soft layer, and having a lower elastic modulus than the first soft layer and the second soft layer,
The maximum height roughness (Rt) of the flexible substrate is 0.6㎛ or more,
A cover window for a display wherein the maximum height roughness (Rt) in the first direction from the surface is 0.2 μm to 0.4 μm. The method of claim 1,
A cover window for a display, wherein one of the first soft layer and the second soft layer includes an antistatic material. The method of claim 1,
The thickness of the first soft layer and the second soft layer is 5㎛ to 15㎛ cover window for a display. 4. The method of claim 3,
The thickness of the hard layer is 10㎛ to 15㎛ cover window for a display. The method of claim 1,
The first direction is a cover window for a display corresponding to an extending direction of the flexible substrate. The method of claim 1,
The first soft layer and the second soft layer include a resin composition having an elastic modulus of 2 GPa or more,
The hard layer is a cover window for a display comprising a resin composition having an elastic modulus of 1.5 GPa or less. 3. The method of claim 2,
The resistance of the cover window for the display is 10 ¹ Ω to 10 ⁶ Ω for the display cover window. Preparing a flexible substrate having a maximum height roughness (Rt) of 0.6 μm or more; and
Forming a first soft layer, a second soft layer, and a hard layer on the flexible substrate so that the maximum height roughness (Rt) in the first direction is 0.2㎛ to 0.4㎛;
The step of preparing the flexible substrate,
the flexible substrate on which the expression waveform is formed in the first direction; carrier glass; and preparing a release member,
Forming the first soft layer, the second soft layer and the hard layer,
forming a first soft layer by applying a first resin composition on the carrier glass;
adhering the first soft layer to one surface of the flexible substrate;
forming a second soft layer by applying a second resin composition on the release member;
adhering the second soft layer to the other surface of the flexible substrate;
after releasing the release member, applying a third resin composition on the second soft layer to form a hard layer having a lower elastic modulus than the first soft layer and the second soft layer; and
Method of manufacturing a cover window for a display comprising the step of removing the carrier glass. 9. The method of claim 8,
In the step of forming a first soft layer by applying a first resin composition on the carrier glass or forming a second soft layer by applying a second resin composition on the release member, the first resin composition or the second The method of manufacturing a cover window for a display further comprising the step of adding an antistatic material to the resin composition.

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