KR102310452B1 - Method for manufacturing plastic substrate for light guide panel - Google Patents

Abstract

A method for efficiently manufacturing a plastic substrate for a light guide plate using a wire saw cutting device is provided. According to the manufacturing method of the present invention, a plastic substrate for a light guide plate having a small degree of warpage and a small variation in thickness between substrates is provided.

Description

Manufacturing method of a plastic substrate for a light guide plate TECHNICAL FIELD

The present invention relates to a method of manufacturing a plastic substrate for a light guide plate having a small thickness deviation and a degree of warpage, and more particularly, to a method in which a plastic substrate for a light guide plate can be efficiently manufactured while having a small thickness deviation and degree of warpage .

The light guide plate is used in all electronic devices that adopt liquid crystal display devices, such as augmented reality devices, virtual reality devices, mobile phones, navigation devices, computers, and TVs. The light guide plate plays a role of uniformly distributing light flowing in from a light source located on the side within the light guide plate to a desired area. Therefore, when the thickness deviation of the substrate for the light guide plate is large or the degree of bending is large, the total reflection angle changes depending on the position of the substrate to cause a double image of the output image, so it is necessary to control the thickness deviation and the degree of warpage of the substrate for the light guide plate.

In general, glass and plastic are used as a material for a substrate for a light guide plate, and plastic has an advantage of being light and unbreakable compared to glass. Conventionally, when manufacturing a substrate for a light guide plate using a plastic, a substrate for a light guide plate is manufactured by forming a plastic in a certain shape through molding and grinding or processing the plastic. The molding method is a method of molding a plastic thicker than the thickness of the desired substrate and grinding it to make the substrate of the desired thickness. However, since only one substrate can be manufactured at a time by the conventional molding method, the substrate manufacturing efficiency is low, so there is a problem in that it is disadvantageous in manufacturing a large number of substrates.

On the other hand, as one of the methods of manufacturing a silicon substrate, which is a semiconductor substrate, a method of manufacturing a plurality of silicon substrates at once by cutting a silicon ingot with a wire-shaped saw is known.

However, in the case of manufacturing a plastic substrate for a light guide plate by a method of manufacturing a silicon substrate from a silicon ingot, there is a limitation in that a plastic substrate having a desired degree of thickness deviation and warpage cannot be obtained.

Korean Publication: KR 10-2007-0075809 A

The technical problem to be solved by the present invention is to provide a method for efficiently manufacturing a plastic substrate for a light guide plate having a small thickness deviation and a small degree of warpage.

However, the technical problems to be solved by the present invention are not limited to the above-mentioned problems, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

One embodiment of the present invention is a pair of guide rollers are spaced apart to rotate; a wire saw including a plurality of wires wound parallel to each other and wound on the pair of guide rollers; And a method of manufacturing a plastic substrate for a light guide plate using a wire saw cutting device comprising an ingot fixing unit located above or below the wire saw, the method comprising: fixing a plastic ingot to the ingot fixing unit; rotating the pair of guide rollers to drive the wire saw; cutting the plastic ingot with the wire saw to obtain a plastic base material; and polishing the surface of the plastic base material to obtain a plastic substrate, wherein the wire saw has a running speed of 350 m/min or more and 650 m/min or less, and the cutting speed of the plastic ingot is 230 μm/min or more and 300 Provided is a method for manufacturing a plastic substrate for a light guide plate having a thickness of μm/min or less.

With the manufacturing method according to an exemplary embodiment of the present invention, a plurality of plastic substrates for a light guide plate can be efficiently manufactured without thickness variation.

A plastic substrate for a light guide plate manufactured according to an exemplary embodiment of the present invention has a small thickness variation and a small degree of warpage.

1 is a view briefly showing a wire saw cutting device that can be used in a method of manufacturing a plastic substrate for a light guide plate according to an embodiment of the present invention.
2 is a view showing a plastic base material manufactured according to Examples and Comparative Examples of the present invention.

In the present specification, when a part "includes" a certain component, this means that other components may be further included rather than excluding other components unless otherwise stated.

In this specification, the maximum thickness variation (Total Thickness Variation (TTV)) means the maximum change in the wafer thickness, specifically, the difference between the maximum value and the minimum value of the thickness.

In the present specification, when a member is said to be located “on” another member, this means that the member may further include other components as well as the case where the member is in contact with the other member.

Hereinafter, the present specification will be described in more detail.

One embodiment of the present invention is a pair of guide rollers are spaced apart to rotate; a wire saw including a plurality of wires wound parallel to each other and wound on the pair of guide rollers; And a method of manufacturing a plastic substrate for a light guide plate using a wire saw cutting device comprising an ingot fixing unit located above or below the wire saw, the method comprising: fixing a plastic ingot to the ingot fixing unit; rotating the pair of guide rollers to drive the wire saw; cutting the plastic ingot with the wire saw to obtain a plastic base material; and polishing the surface of the plastic base material to obtain a plastic substrate.

1 is a view briefly showing a wire saw cutting device that can be used in a method of manufacturing a plastic substrate for a light guide plate according to an embodiment of the present invention. The wire saw device is not particularly limited, and may be appropriately modified and used commercially available. The wire saw cutting device is spaced apart and rotates a pair of guide rollers (100, 100'); A wire saw 300 comprising a plurality of wires 200 wound parallel to each other and spaced apart from each other on the pair of guide rollers 100 and 100'; and an ingot fixing unit 400 positioned on the wire saw. In some cases, the ingot fixing unit 400 may be located under the wire saw 300 .

According to an exemplary embodiment of the present invention, first, a plastic ingot 500 for manufacturing a plastic substrate for a light guide plate is fixed to the ingot fixing unit 400 .

A method of fixing the plastic ingot to the ingot fixing unit is not particularly limited, and for example, it may be fixed using an adhesive or an adhesive. Specifically, the ingot may be fixed by using an adhesive or an adhesive to a jig (JIG) and a dummy glass, which can be viewed as an ingot fixing unit.

According to an exemplary embodiment of the present invention, the plastic ingot may be prepared from at least one selected from a carbonate-based resin, an acrylate-based resin, a urethane-based resin, and an epoxy-based resin. The plastic ingot is more preferably manufactured from a urethane-based resin and/or an epoxy-based resin. The plastic ingot prepared from the urethane-based resin and/or the epoxy-based resin may have excellent mechanical stability.

The plastic ingot may be prepared by curing at least one selected from a carbonate-based resin, an acrylate-based resin, a urethane-based resin, and an epoxy-based resin. Specifically, the plastic ingot may be formed by thermosetting at least one selected from a carbonate-based resin, an acrylate-based resin, a urethane-based resin, and an epoxy-based resin at a temperature of 80°C to 120°C for 20 to 40 hours. In addition, the curing may be performed after the plastic composition is injected into a mold having a predetermined shape. The shape of the mold may be a cylindrical shape or a hexahedral shape, but is not limited thereto.

The carbonate-based resin may be formed by polymerization of bisphenol A and phosgene. In addition, the urethane-based resin has a urethane bond in the molecule, and may be formed by polymerization of diisocyanates and polyols. The epoxy resin may be formed by polymerization of bisphenol A and/or bisphenol F and epichlorohydrin.

According to an exemplary embodiment of the present invention, the carbonate-based resin, acrylate-based resin, urethane-based resin or epoxy-based resin is a carbonate-based resin containing sulfur, an acrylate-based resin containing sulfur, a sulfur-containing urethane-based resin or sulfur containing It may be an epoxy-based resin. The plastic ingot including at least one selected from the group consisting of a sulfur-containing carbonate-based resin, a sulfur-containing acrylate-based resin, a sulfur-containing urethane-based resin, and a sulfur-containing epoxy-based resin can secure a high refractive index. Specifically, the plastic ingot may have a refractive index of 1.7 or more and 2.0 or less.

According to an exemplary embodiment of the present invention, the plastic ingot may have a tensile modulus of elasticity of 2 GPa or more and 5 GPa or less at room temperature (25° C.). When the tensile modulus of elasticity of the plastic ingot is within the above range, the flatness of the surface of the plastic base material may be excellent when cutting with the wire saw. In addition, a plastic base material having a small degree of warpage can be obtained.

According to an exemplary embodiment of the present invention, the plastic ingot may have a cross-sectional area of 100 cm ² or less. When the cross-sectional area of the plastic ingot is within the above range, it is possible to obtain a plastic base material having a uniform thickness and a small degree of warpage, and accordingly, a substrate having a small thickness deviation and degree of warpage can be obtained.

According to an exemplary embodiment of the present invention, the plastic ingot 500 is fixed to the ingot fixing unit 400 and then the pair of guide rollers 100 and 100 ′ are rotated to drive the wire saw 300 . . When a plurality of wire saws come into contact with the plastic ingot, the plastic ingot is cut by friction caused by the driving of the plurality of wire saws.

A plurality of grooves (not shown) may be formed on the surface of the pair of guide rollers 100 and 100 ′ according to an exemplary embodiment of the present invention so that the plurality of wires 200 can be wound at regular intervals. Accordingly, the plurality of wires 200 may be wound in a manner such as being inserted into grooves formed at regular intervals on the surfaces of the pair of guide rollers 100 and 100 ′. At this time, the plurality of wires may be wound about 500,000 on the pair of guide rollers. The tensile strength applied to the wire wound around the guide roller may be 20 kg/mm ² or more and 30 kg/mm ² or less. Specifically, it may be 23 kg/mm ² or more and 27 kg/mm ² or less. More specifically, it ^{may be 24 kg/mm 2} or more and 25 kg/mm ² or less. When the tensile strength applied to the wire is within the above range, it is possible to prevent breakage of the wire or variations in the thickness of the plastic base material and the substrate.

According to an exemplary embodiment of the present invention, the plurality of wires may be wound around the pair of guide rollers spaced apart by an interval of 0.8 mm or more and 2.0 mm or less. When the distance between the plurality of wires is within the above range, the plastic base material may be polished to have an appropriate thickness when the plastic substrate is formed.

According to an exemplary embodiment of the present invention, the plurality of wires may be wires coated with an abrasive. The plurality of wires may be coated with an abrasive. According to an exemplary embodiment of the present invention, the cutting may be performed while immersing an abrasive in the form of a slurry on the surfaces of the plurality of wires. The abrasive may include, but is not limited to, particles of aluminum oxide. The abrasive may be a mixture of Kumgangsa powder and water-soluble oil in a weight ratio of 1:1. The gold steel particles may have an average particle size of 1 μm or more and 5 μm or less. Specifically, it may be 2 μm or more and 4 μm or less. When the average particle size of the gold steel particles is within the above range, excellent flatness of the surface of the plastic base material may be realized.

According to an exemplary embodiment of the present invention, by using a wire saw including a plurality of wires coated with an abrasive containing the gold steel particles, the degree of damage to the surface of the plastic base material is remarkably low and the surface of the plastic substrate is free of foreign substances. can produce

Meanwhile, a driving means (not shown) for applying a driving force may be coupled to the pair of guide rollers 100 and 100 ′ to be driven. Since the plurality of wires 200 are wound around the pair of guide rollers 100 and 100', the wire saw 300 travels due to the rotation of the pair of guide rollers 100 and 100'. . The pair of guide rollers 100 and 100' can rotate in both directions. According to an exemplary embodiment of the present invention, the pair of guide rollers 100 and 100' may be rotated in one direction and then rotated in the opposite direction to cut the wire saw as it moves back and forth.

The plastic ingot fixed to the ingot fixing unit is cut while moving in the traveling wire saw direction to obtain a plastic base material.

According to an exemplary embodiment of the present invention, the wire saw has a traveling speed of 350 m/min or more and 650 m/min or less. The traveling speed of the wire saw may be specifically, 365 m/min or more and 440 m/min or less, and more specifically, 380 m/min or more and 430 m/min or less. When the traveling speed of the wire saw is within the above range, the flatness of the surface of the plastic base material may be excellent, and the plastic substrate manufacturing efficiency may be improved.

In addition, according to an exemplary embodiment of the present invention, the speed at which the plastic ingot is moved and cut by the wire saw is 230 μm/min or more and 300 μm/min or less. The cutting speed of the plastic ingot may be specifically, 250 μm/min or more and 300 μm/min or less, and more specifically, 260 μm/min or more and 290 μm/min or less. When the cutting speed is within the above range, the thickness deviation and the degree of warpage of the plastic base material may be small, and the manufacturing efficiency of the plastic substrate for the light guide plate may be improved. The cutting speed of the plastic ingot may be maintained until the wire saw completely cuts the plastic ingot.

The plastic base material manufactured according to an exemplary embodiment of the present invention may have a maximum thickness deviation of 10 μm or less. Specifically, the maximum thickness deviation of the plastic base material may be 7 μm or less, and more specifically, 5 μm or less. When the maximum thickness deviation of the plastic base material is within the above range, a plastic substrate having a uniform thickness may be manufactured.

According to an exemplary embodiment of the present invention, in the step of forming the plastic substrate by polishing the plastic base material, the polishing may be performed by using an abrasive such as _{Al 2} O ₃ , CeO ₂ , SiO _{2 , or PVC.} The polishing may be primary polishing using a powder abrasive and secondary polishing using a liquid abrasive.

A plurality of plastic substrates manufactured according to an exemplary embodiment of the present invention may have a maximum thickness deviation of 5 μm or less. Specifically, the maximum thickness deviation of the plastic substrate may be 3 μm or less, more specifically, 1 μm or less. When the maximum thickness deviation of the plastic substrate is within the above range, a uniform light guide plate may be manufactured using a plastic substrate having a uniform thickness.

The degree of warpage of the plastic substrate manufactured according to an exemplary embodiment of the present invention may be 50 μm or less. When the bending degree of the substrate is within the above range, the light guide plate made of the substrate maintains a constant angle of total reflection of light introduced from the light source, thereby securing a high-quality output image image.

A light guide plate may be manufactured using the plastic substrate manufactured according to the exemplary embodiment of the present invention.

The light guide plate manufactured by using the plastic substrate manufactured according to an exemplary embodiment of the present invention may be used in electronic devices such as augmented reality devices, virtual reality devices, mobile phones, navigation devices, computers, TVs, etc. where liquid crystal displays are used. Specifically, using the light guide plate, a light emitting device; reflective sheet; the light guide plate; diffusion sheet and; A liquid crystal display including a backlight unit in which a prism sheet is sequentially provided may be manufactured.

The light emitting device serves to provide light, and the reflective sheet serves to reflect the light exiting the lower surface of the light guide plate and return it back into the light guide plate. In addition, the diffusion sheet is located on the upper surface of the light guide plate, and serves to scatter light emitted from the surface of the light guide plate in a predetermined direction to spread it evenly over the surface of the light guide plate. The prism sheet refracts and condenses light emitted from the diffusion sheet to increase luminance on the backlight surface.

Hereinafter, examples will be given to describe the present invention in detail. However, the embodiments according to the present invention may be modified in various other forms, and the scope of the present invention is not to be construed as being limited to the embodiments described below. The embodiments of the present specification are provided to more completely explain the present invention to those of ordinary skill in the art.

Example One

The plastic ingot was fixed to the ingot fixing unit of a wire saw cutting device (NIPPEI TOYAMA, MWM442DM). The plastic ingot has a cross-sectional area of 64 cm ² and a length of 10 mm, and is a thermosetting product of a sulfur-containing urethane-based resin and sulfur-containing epoxy-based resin. A plurality of wires are wound in a plurality of grooves formed at intervals of 1.7 mm on a pair of guide rollers included in the wire saw cutting device. The wire saw was driven by rotating the pair of guide rollers. The plurality of wires were coated with an abrasive prepared by mixing gold steel sand and water-soluble oil having an average particle size of 3 μm in a weight ratio of 1:1. Five plastic base materials were prepared by cutting the plastic ingot with a wire saw including the plurality of wires.

At this time, the running speed of the wire saw wound around the guide roller was 400 m / min, the cutting speed of the plastic ingot was 280 ㎛ / min.

Using a polishing machine (Suzhou HRT Co., rotation speed: 25 rpm, pressure: 0.1 MPa), the plastic base material was first polished with a Ce pad ( _{using a powdered abrasive containing CeO 2} ), and secondary polished with a fusion pad A plastic substrate having a thickness of 1.3 mm was prepared by _{(using a liquid abrasive containing SiO 2 ).}

comparative example One

A plastic base material was prepared in the same manner as in Example 1, except that the running speed of the wire saw wound around the guide roller was 500 m/min and the cutting speed of the plastic ingot was 70 μm/min.

However, in the case of the plastic base material of Comparative Example 1, the thickness deviation was large and the surface was rough, so that the polishing process was impossible, so that the plastic substrate could not be manufactured.

plastic base material and evaluation of the maximum thickness deviation of the substrate

The thickness of five points of the plastic base material and the substrate of Examples and Comparative Examples was measured using a digital micrometer (Mistoyo Corporation, IP 65), and the maximum thickness deviation of the plastic base material and the substrate was evaluated from the measured values.

Evaluation of the degree of warpage of the substrate

The height at 25 points of the plastic substrates of Examples and Comparative Examples was measured using a non-contact three-dimensional measuring instrument (Dukin, PLUTO), and the degree of warpage was evaluated by calculating the maximum deviation of the height of the plastic substrate from the measured values. The height is the relative height of the substrate measured through the distance from the measuring sensor portion of the non-contact three-dimensional measuring instrument to the substrate.

2 is a view showing a plastic base material manufactured according to Examples and Comparative Examples of the present invention. The evaluation of the maximum thickness deviation of the plastic base material and the substrate is shown in Table 1 below. And, the evaluation of the degree of warpage of the plastic substrate is shown in Table 2 below.

plastic base material plastic substrate thickness of five points (μm) Maximum thickness deviation
(μm) thickness of five points (μm) Maximum thickness deviation
(μm) Example 1 1078 1073 1072 1074 1071 7 823 823 822 821 821 2 Comparative Example 1 1530 1367 1438 1178 1090 440 -

plastic substrate Warpage (um) Example 1 25.1 Comparative Example 1 Measurable

In the case of Example 1, it can be seen that the maximum thickness deviation of the five plastic base materials and the substrate manufactured at once is small, and the degree of warpage is small. On the other hand, in the case of Comparative Example 1, in which the running speed of the wire saw wound around the guide roller is 500 m/min, and the cutting speed of the plastic ingot is 70 μm/min, it can be confirmed that the maximum thickness deviation of the plastic base material is large, Accordingly, it can be confirmed that the plastic substrate cannot be manufactured. Accordingly, it can be seen that a plurality of plastic substrates for a light guide plate having a small thickness variation and a small degree of warpage can be manufactured by the manufacturing method according to an exemplary embodiment of the present invention.

100, 100': guide roller
200: a plurality of wires
300: wire saw
400: ingot fixing unit
500: ingot

Claims (8)

A pair of guide rollers that are spaced apart and rotate; a wire saw including a plurality of wires wound parallel to each other and wound on the pair of guide rollers; And as a method of manufacturing a plastic substrate for a light guide plate using a wire saw cutting device comprising an ingot fixing unit located on the upper or lower portion of the wire saw,
The method includes fixing a plastic ingot to the ingot holding unit;
rotating the pair of guide rollers to drive the wire saw;
cutting the plastic ingot with the wire saw to obtain a plastic base material; and
Polishing the surface of the plastic base material to obtain a plastic substrate,
The wire saw has a running speed of 350 m/min or more and 650 m/min or less,
The cutting speed of the plastic ingot is 230 μm/min or more and 300 μm/min or less,
The tensile strength applied to the wire is 20 kg/mm ² or more and 30 kg/mm ² or less,
The method of manufacturing a plastic substrate for a light guide plate, wherein the plastic base material has a maximum thickness deviation of 10 μm or less.
According to claim 1,
The plastic ingot is a method of manufacturing a plastic substrate for a light guide plate prepared from at least one selected from a carbonate-based resin, an acrylate-based resin, a urethane-based resin, and an epoxy-based resin.
According to claim 1,
The plastic ingot is a method of manufacturing a plastic substrate for a light guide plate having a tensile modulus of elasticity of 2 GPa or more and 5 GPa or less at room temperature (25° C.).
According to claim 1,
The plastic ingot is a method of manufacturing a plastic substrate for a light guide plate having a cross-sectional area of 100 cm ^{2 or less.}
According to claim 1,
The method of manufacturing a plastic substrate for a light guide plate, wherein the plurality of wires are wound at intervals of 0.8 mm or more and 2.0 mm or less.
According to claim 1,
The method of manufacturing a plastic substrate for a light guide plate, wherein the plurality of wires are wires coated with an abrasive.
7. The method of claim 6,
The abrasive is a method of manufacturing a plastic substrate for a light guide plate comprising gold gangbang particles.
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