KR102377684B1 - Pattern film for transferring display pixel and method for manufacturing display using the same - Google Patents

Abstract

A pattern film for transferring display pixels according to an exemplary embodiment of the present application includes a base material; and a polydimethylsiloxane-based film provided on the substrate and including a protrusion pattern on the surface, wherein the height of the protrusion pattern is 10㎛ to 50㎛, and the upper surface of the protrusion pattern has a 10-point average roughness (ten point). The median height roughness (Rz) is 0.5 ㎛ or less, and the 10-point average roughness of the surface without the protrusion pattern of the polydimethylsiloxane-based film is 1 ㎛ or more.

Description

Pattern film for transferring display pixels and method of manufacturing displays using the same {PATTERN FILM FOR TRANSFERRING DISPLAY PIXEL AND METHOD FOR MANUFACTURING DISPLAY USING THE SAME}

This application relates to a pattern film for transferring display pixels and a method of manufacturing a display using the same.

Recently, the demand for lighting fixtures made of LED (Light Emitting Diode) has increased explosively due to the advantages of having a long lifespan compared to existing incandescent or fluorescent lights, consuming relatively low power, and not emitting pollutants during the manufacturing process. The application areas of LED are gradually becoming more diverse, including application to not only display devices using light emission but also backlight elements of lighting devices and LCD displays.

In particular, LED has the advantage of low heat generation and long lifespan due to high energy efficiency while being able to be driven at a relatively low voltage. With the development of technology that can provide white light with high brightness, which was difficult to implement in the past, most currently used It is expected that it can replace light source devices.

Republic of Korea Patent Publication No. 10-2015-0033169

The present application seeks to provide a pattern film for transferring display pixels and a method of manufacturing a display using the same.

One implementation state of this application is,

write; and

A polydimethylsiloxane-based film provided on the substrate and including a protrusion pattern on the surface,

The height of the protrusion pattern is 10㎛ to 50㎛,

The ten point average height roughness (Rz) of the upper surface of the protrusion pattern is 0.5 μm or less,

A pattern film for transfer of display pixels is provided, wherein the 10-point average roughness of the surface of the polydimethylsiloxane-based film without the protrusion pattern is 1㎛ or more.

In addition, other embodiments of this application are:

Preparing a pattern film for transferring the display pixels;

providing display pixels on the surface of the protrusion pattern; and

Transferring the display pixels to a display electrode substrate

Provides a method of manufacturing a display including.

According to an exemplary embodiment of the present application, since a protrusion pattern is formed on the surface of the polydimethylsiloxane-based film, the contact surface between the electrode surface and the polydimethylsiloxane-based film can be reduced when transferring the display pixel, and the transfer of the display pixel Afterwards, the polydimethylsiloxane-based film has excellent release properties.

In addition, according to an exemplary embodiment of the present application, when using the pattern film for transferring display pixels, only light emitting device chips at specific intervals are selectively contacted among light emitting device chips formed on the wafer, thereby preventing contamination of the wafer. There are features that can be used.

In addition, according to an exemplary embodiment of the present application, the upper surface of the protrusion pattern is composed of a polydimethylsiloxane-based film surface with good adhesion characteristics and low surface roughness, but the protrusion pattern of the polydimethylsiloxane-based film is not provided. Even when unnecessary contact occurs by artificially adding surface roughness to the surface, it has the feature of making it easier to attach/release without damaging the electrode substrate.

1 and 2 are diagrams schematically showing a pattern film for transferring display pixels according to an exemplary embodiment of the present application.
Figure 3 is a diagram schematically showing a method of calculating the area ratio occupied by a protrusion pattern in an exemplary embodiment of the present application.
Figure 4 is a graph showing the surface roughness (Rz) measured for the laminate manufactured in Example 1 and Comparative Example 1 of the present application.

Hereinafter, this application will be described in detail.

Transfer is a series of actions that transfer a single or multiple micro LEDs to a counterpart substrate. The existing method of transferring a single LED chip has been applied in the packaging process using Pick & Place equipment, but as the size of LEDs decreases to several microns, high-precision transfer technology is needed. To this end, technology has been developed in two ways: direct transfer and printing transfer. Direct transfer is a technology that directly bonds the material or thin film to be transferred to the target substrate, and print transfer can be defined as a technology that utilizes an intermediate medium such as an electrostatic or bonding stamp. Representative technologies for direct transfer and print transfer are as follows.

The direct transfer method is a method of separating p-type GaN into several micro-sized pieces through an etching process and then directly bonding it to a substrate on which a fine switching device such as CMOS is formed. If necessary, the silicon or sapphire substrate used as the growth substrate can be removed, and individual GaN devices of several microns separated into a single size can be combined with a switching microelectronic device to make it easy to control the operating current. This method has the advantage of being easy to manufacture and transfer LEDs, but quality control of each device becomes a very important factor.

There are currently two known printing-type transfer methods. As a first method, Luxvue of the United States proposed a method using an electrostatic head. The principle is to apply voltage to the head made of silicone, thereby creating adhesion to the micro LED through an electrification phenomenon. This method has the advantage of being able to selectively transfer a desired area or a single element, but problems may arise regarding damage to the micro LED due to charging due to the voltage applied to the head during electrostatic induction. The second method, developed by X-Celeprint in the United States, uses a transfer head made of an elastic polymer material to transfer the LEDs on the wafer to the desired substrate. There is no problem with damage to the LED compared to the electrostatic head method, but the adhesive force of the elastic transfer head must be greater than that of the target substrate during the transfer process to transfer the micro LED stably. It has the disadvantage of requiring an additional process to form electrodes. . In addition, continuously maintaining the adhesion of the elastic polymer material also serves as a very important factor.

When using PDMS, which has excellent replication properties with conventional master molds, as an adhesive material for the transfer process, it is very difficult to remove it after transfer to the electrode substrate due to the self-adhesive nature of the PDMS surface. For precise transfer of fine pixel patterns for display purposes, face-to-face transfer in the form of a flat plate is inevitable.

In order to solve the above problem, even if a patterned PDMS film for transfer with a specific protrusion pattern shape is used, deformation of the protrusions due to pressure during transfer may partially occur depending on equipment precision or thickness uniformity of the pattern film. If unnecessary contact with the bottom PDMS layer occurs due to deformation, detachment from the electrode substrate may be difficult, detachment speed may decrease, and tack time may increase.

Accordingly, the present application seeks to provide a pattern film for transfer for forming display pixels with excellent transfer characteristics.

A pattern film for transferring display pixels according to an exemplary embodiment of the present application includes a base material; and a polydimethylsiloxane-based film provided on the substrate and including a protrusion pattern on the surface, wherein the height of the protrusion pattern is 10㎛ to 50㎛, and the upper surface of the protrusion pattern has a 10-point average roughness (ten point). The median height roughness (Rz) is 0.5 ㎛ or less, and the 10-point average roughness of the surface without the protrusion pattern of the polydimethylsiloxane-based film is 1 ㎛ or more.

In an exemplary embodiment of the present application, the display pixel may be a light emitting device chip (LED CHIP). The size of the light emitting device chip may be 10 μm to 100 μm and 25 μm to 50 μm in width and height, respectively.

In an exemplary embodiment of the present application, the substrate may be a glass substrate or a transparent plastic substrate with excellent transparency, surface smoothness, ease of handling, and waterproofness, but is not limited thereto, and is limited to any transparent substrate commonly used in electronic devices. It doesn't work. Specifically, the transparent substrate includes glass; polycarbonate-based resin; Urethane resin; polyimide resin; polyester resin; (meth)acrylate-based polymer resin; It may be made of polyolefin resin such as polyethylene or polypropylene.

The thickness of the substrate may be 100㎛ to 1,000㎛, 300㎛ to 700㎛, but is not limited thereto.

In an exemplary embodiment of the present application, based on the entire upper surface of the polydimethylsiloxane-based film, the area ratio occupied by the protrusion pattern may be 5% or less, 1% to 5%, and 1% to 3.5%. It may be %. If the area ratio occupied by the protrusion pattern exceeds 5% based on the entire upper surface of the polydimethylsiloxane-based film, detachment from the electrode substrate during the transfer process may become difficult, and if it is less than 1%, the upper surface of the protrusion may become difficult. Positional alignment defects may occur due to insufficient space for the light emitting device chip to be seated in the correct position.

The area ratio occupied by the protrusion pattern can be calculated using Figure 3 and Equation 1 below.

[Equation 1]

Area ratio occupied by the protrusion pattern (%) = [(a × b) / Pitch ² ] × 100

In Equation 1 above,

(a × b) is the upper area of the protrusion, and Pitch is the pitch of the protrusion pattern.

In an exemplary embodiment of the present application, the ten point average height roughness (Rz) of the upper surface of the protrusion pattern is 0.5㎛ or less, and the surface of the polydimethylsiloxane-based film not provided with the protrusion pattern The 10-point average roughness is characterized as 1㎛ or more. The Rz can be measured with Mitutoyo SJ301 measuring equipment.

If the ten point average height roughness (Rz) of the upper surface of the protrusion pattern exceeds 0.5㎛, it shows low adhesion characteristics, causing defects such as non-transfer defects or chip misalignment when transferring to the pixel chip. can do. Since the lower the Rz value of the upper surface of the protrusion pattern, the better, setting a lower limit is meaningless.

The 10-point average roughness of the surface without the protrusion pattern of the polydimethylsiloxane-based film is characterized as 1 ㎛ or more, and is not particularly limited to the upper limit if there is no problem of deterioration of the overall thickness uniformity of the laminate. If the 10-point average roughness of the surface of the polydimethylsiloxane-based film without the protrusion pattern is less than 1㎛, it is not suitable because the adhesion is high and desorption is difficult during the transfer process.

In an exemplary embodiment of the present application, the static friction coefficient and kinetic friction coefficient of the surface of the polydimethylsiloxane-based film without the protrusion pattern may be 10 or less.

The fact that the friction coefficient can be measured means that the surface adhesion weakens as the surface roughness of the polydimethylsiloxane-based film increases, and this means that the minimum slip resistance that allows the friction coefficient measurement evaluation is secured. When the static friction coefficient and the kinetic friction coefficient are less than 10, the adhesion of the polydimethylsiloxane-based film is offset by the surface roughness, and the closer it is to the lower limit of 0, the more advantageous it can be.

The static friction coefficient and kinetic friction coefficient can be measured using a friction tester (JIS K7125, -P8147, ISO 8295) manufactured by Toyoseiki. The sled used to measure the friction force was 1.96N (200g), and the friction coefficient μ can be divided into the static friction coefficient (uS) and the kinetic friction coefficient (uD).

f = μN (f: friction force, μ: friction coefficient, N: normal force)

In an exemplary embodiment of the present application, the shape of the protrusions constituting the protrusion pattern may be in the form of a polygonal pillar or a cylinder. Additionally, the upper surface of the protrusion may be flat, convex, concave, or a combination of these shapes.

In an exemplary embodiment of the present application, the shape of the protrusions constituting the protrusion pattern is in the form of a polygonal pillar or cylinder, and the upper surface of the protrusion is characterized in that it is in a flat shape. More specifically, the shape of the protrusions constituting the protrusion pattern may be in the form of a pillar such as a square pillar or cylinder, and the surface of the protrusion should be flat to reduce the risk of damage to the light emitting device chip. . In the present application, the “flat shape” means 0.5㎛ or less based on the 10-point surface roughness, Rz. The Rz can be measured with Mitutoyo SJ301 measuring equipment.

The upper area of the protrusion may vary depending on the display resolution and design structure, and may be more specifically 10 to 20 times the size of the display pixel, but is not limited thereto. Additionally, the shape of the protrusions constituting the protrusion pattern may be a square pillar, and in this case, the upper area of the square pillar may be 100㎛ × 200㎛, 100㎛ × 150㎛, etc.

In an exemplary embodiment of the present application, the height of the protrusion pattern may be 10㎛ to 50㎛. If the height of the protrusion pattern is less than 10㎛, the height difference is not sufficient, so even a very weak transfer pressure causes deformation of the polydimethylsiloxane-based film and causes full contact, and if it exceeds 50㎛, the pattern There is a disadvantage that replication and master mold supply become difficult.

Additionally, the spacing between the protrusion patterns, that is, the pitch of the protrusion patterns, may be determined by display resolution, and may also include a repeating form of subpixels considering yield, etc. More specifically, the pitch of the protrusion pattern may be 700㎛ to 900㎛, or about 800㎛, but is not limited thereto.

The pitch of the protrusion pattern can be arbitrarily changed depending on the display resolution, but if the protrusion pitch is below a certain level, the contact area during transfer may be relatively large, making attachment and detachment disadvantageous. Therefore, in the present application, it is preferable that the pitch of the protrusion pattern for selective transfer of the light emitting device chip is 700㎛ to 900㎛. When the pitch of the protrusion pattern is less than 700㎛, there is a disadvantage in that it is difficult to apply, such as the size of the pixel to be transferred is designed to be too small.

In an exemplary embodiment of the present application, the protrusion pattern is used to selectively transfer only the chips that are separated by a specific pixel pitch from the light emitting device chips (LED CHIP) on the wafer. By selectively contacting and transferring only specific pixel chips, unnecessary contact is made. , contamination, etc. can be prevented, and the light emitting device chip can be easily attached and detached.

In an exemplary embodiment of the present application, a polydimethylsiloxane-based film including a protrusion pattern on the surface may be manufactured from a master mold including a groove pattern corresponding to the protrusion pattern. In particular, in an exemplary embodiment of the present application, the surface characteristics of the master mold are adjusted to determine the 10-point average roughness of the upper surface of the protrusion pattern and the 10-point average roughness of the surface without the protrusion pattern of the polydimethylsiloxane-based film. It was adjusted to distinguish them from each other. The surface properties of the master mold can be adjusted using chemical methods used in micro device processes, dry etching, etc., and other methods include physical polishing, sandblasting, or deposition or lamination of different materials. You can also use this method.

In an exemplary embodiment of the present application, the pattern film for transfer of display pixels includes preparing a master mold with roughness provided to the surface of the protrusion, coating and curing PDMS on the master mold, and applying PDMS on the master mold. It can be manufactured by a method including a mold release step.

Since the polydimethylsiloxane-based film has excellent mold replication and release properties, it can be more effectively applied to the pattern film for transfer of display pixels according to the present application. UV-curable polyurethane-based resin (PUA, Poly Urethane Acrylate), which is mainly used for conventional reproduction purposes, has the disadvantage of making it difficult to provide appropriate hardness and adhesiveness that affect transfer characteristics.

Conventionally, due to the self-adhesive nature of the surface of the polydimethylsiloxane-based film, it was very difficult to release the polydimethylsiloxane-based film after transferring the display pixels to the desired electrode substrate. However, in the present application, by forming a protrusion pattern with a specific area ratio and height on the surface of the polydimethylsiloxane-based film, the contact area between the electrode surface and the polydimethylsiloxane-based film can be reduced during the transfer of the display pixel, and the contact surface of the display pixel can be reduced. The polydimethylsiloxane-based film has the advantage of excellent release characteristics after transfer.

The thickness of the polydimethylsiloxane-based film may be 200㎛ to 800㎛, and when considering dimensional deformation, etc., it may be 300㎛ to 600㎛, but is not limited thereto.

In the present application, the adhesive force of the surface of the protrusion pattern may be 600 gf/cm ² or less. The adhesive force of the surface of the protrusion pattern is the maximum load applied when a glass substrate with an area of 1 cm × 1 cm is brought into contact with the surface of the protrusion pattern for 30 seconds under a load of 1,000 gf and then released. Additionally, the adhesive force of the surface of the protrusion pattern may be 300 gf/cm ² or more. If the adhesive force of the surface of the protrusion pattern is less than 300 gf/cm ² , the light emitting device chip may fall and be lost or unnecessary rotation may occur due to insufficient adhesive force during handling between processes.

In the present application, an adhesive layer may be additionally included between the substrate and the polydimethylsiloxane-based film.

The adhesive layer may use materials known in the art, and more specifically, pressure-sensitive adhesive (PSA), an acrylic adhesive, a synthetic rubber adhesive, etc. may be used, but is not limited thereto. In addition, in an exemplary embodiment of the present application, the adhesive layer may use a double-sided PSA, and in this case, one side of the double-sided PSA may include a silicone-based adhesive, and the other side may include an acrylic adhesive, As a result, adhesion to dissimilar materials can be excellent.

The thickness of the adhesive layer may be 30㎛ to 300㎛, 50㎛ to 150㎛, but is not limited thereto.

A pattern film for transferring display pixels according to an exemplary embodiment of the present application is schematically shown in Figures 1 and 2 below.

As shown in FIG. 1 below, a pattern film for transferring display pixels according to an exemplary embodiment of the present application includes a substrate 10; and a polydimethylsiloxane-based film 30 provided on the substrate 10 and including a protrusion pattern 20 on the surface. At this time, the ten point average height roughness (Rz) of the upper surface 50 of the protrusion pattern is 0.5㎛ or less, and the surface 60 of the polydimethylsiloxane-based film without the protrusion pattern is The average roughness of 10 points is 1㎛ or more.

In addition, as shown in FIG. 2 below, an adhesive layer 40 may be additionally included between the substrate 10 and the polydimethylsiloxane-based film 30.

In addition, a method of manufacturing a display according to an exemplary embodiment of the present application includes preparing a pattern film for transferring the display pixels; providing display pixels on the surface of the protrusion pattern; and transferring the display pixels to a display electrode substrate.

The step of providing display pixels on the surface of the protrusion pattern may be performed using a lift-off technology using a laser, but is not limited to this.

The step of transferring the display pixels to the display electrode substrate can be done by attaching them to an electrode substrate provided with an adhesive function using appropriate transfer pressure.

In addition, according to an exemplary embodiment of the present application, when using the pattern film for transferring display pixels, only light emitting device chips at specific intervals are selectively contacted among light emitting device chips formed on the wafer, thereby preventing contamination of the wafer. There are features that can be used.

Hereinafter, the embodiments described in this specification will be illustrated through examples. However, it is not intended that the scope of the above embodiments is limited by the following examples.

< Example >

< Example 1>

A Si wafer etching mold (step 20 ㎛) with an engraved pattern (width × height, 100㎛ × 200㎛) was selectively formed with irregularities on the embossed part through a polishing method. The degree of unevenness is characterized by a 10-point average roughness (Rz) value of 5㎛. Here, the 10-point average roughness (Rz) value means the difference between the average height of the five highest peaks and the average depth of the five deepest valleys in the cross-section curve. Afterwards, PDMS (shinetsu) was coated to a thickness of 400㎛ using a gap applicator and cured at room temperature for 24 hours (hardness 30).

A 100㎛ thick silicone adhesive was coated on the cured PDMS surface and dried, followed by roll lamination with a PC board (500㎛) to complete the final laminate.

When the finished laminate is released from the wafer mold, the protrusions are flat, while the rough surface of the bottom remains in a replicated form.

The height of the protrusion pattern of the manufactured laminate was 20㎛, the pitch was 800㎛, and the upper area was (100㎛×200㎛). The area ratio occupied by the protrusion pattern calculated using Equation 1 above was 3.1%.

< Comparative example 1>

In Example 1, the same procedure as Example 1 was performed, except that unevenness was not formed on the embossed portion of the Si wafer etching mold.

< Experiment example >

The surface roughness, friction coefficient of the bottom, and post-transfer desorption evaluation of the laminates prepared in Example 1 and Comparative Example 1 are shown in Table 1 below. In addition, a graph measuring the surface roughness (Rz) of the laminates manufactured in Example 1 and Comparative Example 1 is shown in Figure 4 below.

[Table 1]

Protrusions: Upper surface of the protrusion pattern.

Bottom part: Surface without protrusion pattern of polydimethylsiloxane-based film

The static friction coefficient and kinetic friction coefficient were measured using a friction tester (JIS K7125, -P8147, ISO 8295) manufactured by Toyoseiki. The sled used to measure the friction force was 1.96N (200g), and the friction coefficient μ can be divided into the static friction coefficient (uS) and the kinetic friction coefficient (uD).

f = μN (f: friction force, μ: friction coefficient, N: normal force)

The adhesion was measured when the surface of the laminated structure, i.e., the protrusion pattern, and PDMS were in simultaneous contact, and was the maximum load applied when a glass substrate with an area of 1 cm × 1 cm was brought into contact with a load of 1,000 gf for 30 seconds and then released.

In evaluating the suitability of the transfer process using the transfer equipment, Example 1 was more advantageous for desorption after transfer because the adhesion of the bottom PDMS was relatively weaker than Comparative Example 1. If the adhesive strength is above a certain level, the tact time during desorption may become longer, a load may be placed on the equipment during the process, and damage to the display substrate may occur.

As shown in the above results, according to an exemplary embodiment of the present application, a protrusion pattern is formed on the surface of the polydimethylsiloxane-based film, so that the contact surface between the electrode surface and the polydimethylsiloxane-based film can be reduced when transferring the display pixel, After transferring the display pixels, the polydimethylsiloxane-based film has excellent release characteristics.

In addition, according to an exemplary embodiment of the present application, when using the pattern film for transferring display pixels, only light emitting device chips at specific intervals are selectively contacted among light emitting device chips formed on the wafer, thereby preventing contamination of the wafer. There are features that can be used.

In addition, according to an exemplary embodiment of the present application, the upper surface of the protrusion pattern is composed of a polydimethylsiloxane-based film surface with good adhesion characteristics and low surface roughness, but the protrusion pattern of the polydimethylsiloxane-based film is not provided. Even when unnecessary contact occurs by artificially adding surface roughness to the surface, it has the feature of making it easier to attach/release without damaging the electrode substrate.

10: Description
20: Protrusion pattern
30: Polydimethylsiloxane-based film
40: Adhesive layer
50: Upper surface of protrusion pattern
60: Surface without protrusion pattern of polydimethylsiloxane-based film

Claims (10)

write; and
A polydimethylsiloxane-based film provided on the substrate and including a protrusion pattern on the surface,
The height of the protrusion pattern is 10㎛ to 50㎛,
The ten point average height roughness (Rz) of the upper surface of the protrusion pattern is 0.5 μm or less,
The 10-point average roughness of the surface without the protrusion pattern of the polydimethylsiloxane-based film is 1㎛ or more,
A pattern film for display pixel transfer, wherein the adhesive force of the surface of the protrusion pattern is 300 gf/cm ² to 600 gf/cm ² . The pattern film for transfer of display pixels according to claim 1, wherein the static friction coefficient and the kinetic friction coefficient of the surface of the polydimethylsiloxane-based film without the protrusion pattern are 10 or less. The pattern film for display pixel transfer according to claim 1, wherein an area ratio occupied by the protrusion pattern is 5% or less based on the entire upper surface of the polydimethylsiloxane-based film. delete The pattern film for display pixel transfer according to claim 1, wherein the pitch of the protrusion pattern is 700㎛ to 900㎛. The pattern film for display pixel transfer according to claim 1, wherein the polydimethylsiloxane-based film has a thickness of 200㎛ to 800㎛. The pattern film for display pixel transfer according to claim 1, wherein the display pixel is a light emitting device chip (LED CHIP). The pattern film for display pixel transfer according to claim 1, further comprising an adhesive layer between the substrate and the polydimethylsiloxane-based film. Preparing a pattern film for transfer of display pixels of any one of claims 1 to 3 and 5 to 8;
providing display pixels on the surface of the protrusion pattern; and
Transferring the display pixels to a display electrode substrate
A method of manufacturing a display comprising. The method of claim 9, wherein the display is a transparent light emitting device display.

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