KR20200039276A - Method for manufacturing plastic substrate for light guide panel - Google Patents

Abstract

Provided is a method which can efficiently manufacture a plastic substrate for a light guide panel by using a wire saw cutting device. According to the manufacturing method of the present invention, provided is the plastic substrate for a light guide panel having a small bending degree and a small thickness deviation between substrates. The method includes the following steps of: fixing a plastic ingot to an ingot fixing unit; driving a wire saw by rotating a pair of guide rollers; cutting the plastic ingot into the wire saw to obtain a plastic basic material; and polishing a surface of the plastic basic material to obtain the plastic substrate.

Description

Manufacturing method of plastic substrate for light guide plate {METHOD FOR MANUFACTURING PLASTIC SUBSTRATE FOR LIGHT GUIDE PANEL}

The present invention relates to a method of manufacturing a plastic substrate for a light guide plate having a small thickness variation and a degree of warpage, and specifically, to a method that can be manufactured efficiently while having a small thickness variation and a degree of warpage. .

The light guide plate is used in all electronic devices that employ liquid crystal display devices such as augmented reality devices, virtual reality devices, mobile phones, navigation systems, computers, and TVs. The light guide plate serves to uniformly distribute the light flowing from the light source located on the side to the desired area by total reflection in the light guide plate. Therefore, when the thickness deviation of the substrate for the light guide plate is large or the degree of warpage is large, the total reflection angle is changed according to the position of the substrate to cause a double image of the exit image.

In general, glass and plastic are used as a material for the light guide plate, and plastic has light and unbreakable advantages over glass. In the past, when manufacturing a substrate for a light guide plate using plastic, a substrate for a light guide plate was manufactured by molding plastic into a certain shape and grinding or processing the same. The molding method is a method in which plastic is molded thicker than a desired substrate thickness and polished to make a desired thickness substrate. However, with the existing molding method, only one substrate can be manufactured at a time, and thus the manufacturing efficiency of the substrate is low, which is disadvantageous in manufacturing a large number of substrates.

Meanwhile, as one of methods for manufacturing a silicon substrate, which is a semiconductor substrate, a method of manufacturing a plurality of silicon substrates at a time by cutting a silicon ingot with a wire saw is known.

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

Korea Open 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 variation and a bending degree.

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

An exemplary embodiment of the present invention is a pair of guide rollers rotated spaced apart; A wire saw including a plurality of wires spaced parallel to each other and wound on the pair of guide rollers; And a method for manufacturing a plastic substrate for a light guide plate using a wire saw cutting device including an ingot fixing unit located at the upper or lower portion of 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 traveling 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 of manufacturing a plastic substrate for a light guide plate having a size of µm / min or less.

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

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

1 is a view schematically 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 exemplary embodiment of the present invention.
2 is a view showing a plastic base material prepared according to the Examples and Comparative Examples of the present invention.

In the present specification, when a part “includes” a certain component, it means that the component may further include other components, not exclude other components, unless otherwise stated.

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

In this specification, when a member is said to be "on" another member, this means that the member may further include other components, as well as when it is in contact with the other member.

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

An exemplary embodiment of the present invention is a pair of guide rollers rotated spaced apart; A wire saw including a plurality of wires spaced parallel to each other and wound on the pair of guide rollers; And a method for manufacturing a plastic substrate for a light guide plate using a wire saw cutting device including an ingot fixing unit located at the upper or lower portion of 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 obtaining a plastic substrate by grinding the surface of the plastic base material.

1 is a view schematically showing a wire saw cutting device that can be used in a method for manufacturing a plastic substrate for a light guide plate according to an exemplary embodiment of the present invention. The wire saw device is not particularly limited, and commercially available ones may be used with appropriate modifications. The wire saw cutting device is a pair of guide rollers (100, 100 ') are rotated spaced apart; A wire saw 300 including a plurality of wires 200 spaced apart and parallel to 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 one embodiment of the present invention, first, the plastic ingot 500 for manufacturing the plastic substrate for the light guide plate is fixed to the ingot fixing unit 400.

The method for fixing the plastic ingot to the ingot fixing unit is not particularly limited, and may be fixed using, for example, an adhesive or an adhesive. Specifically, the ingot may be fixed using an adhesive or an adhesive to a jig and dummy glass, which can be seen as an ingot fixing unit.

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

The plastic ingot may be prepared by curing at least one selected from carbonate-based resins, acrylate-based resins, urethane-based resins, and epoxy-based resins. Specifically, the plastic ingot may be formed by thermally curing at least one selected from carbonate-based resins, acrylate-based resins, urethane-based resins, and epoxy-based resins at a temperature of 80 ° C to 120 ° C for 20 to 40 hours. In addition, the curing may be performed after injecting the plastic composition into a mold having a predetermined shape. The shape of the mold may be cylindrical, hexahedral, 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 a molecule, and may be formed by polymerization of diisocyanates and polyols. The epoxy-based 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 each contain sulfur-containing carbonate-based resin, sulfur-containing acrylate-based resin, sulfur-containing urethane-based resin or sulfur-containing It may be an epoxy-based resin. The plastic ingot comprising at least one selected from the sulfur-containing carbonate-based resin, sulfur-containing acrylate-based resin, sulfur-containing urethane-based resin, and sulfur-containing epoxy-based resin may 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. Further, 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, a plastic base material having a uniform thickness and a low degree of warpage can be obtained, and accordingly, a substrate having a small thickness variation and a 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 ingots are cut by friction by driving the plurality of wire saws.

A plurality of grooves (not shown) may be formed on the surfaces 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 that they are fitted 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 around 500,000 pieces of the pair of guide rollers. The tensile strength applied to the wire wound on 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 fluctuation in thickness variation of the plastic base material and the substrate.

According to an exemplary embodiment of the present invention, the plurality of wires may be wound at a distance of 0.8 mm or more and 2.0 mm or less and wound on the pair of guide rollers. When the spacing of the plurality of wires is within the above range, the plastic base material may be polished to have an appropriate thickness when forming a plastic substrate.

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 plurality of wire surfaces may be cut while depositing a slurry-type abrasive. The abrasive may include aluminum oxide particles, but is not limited thereto. The abrasive may be a mixture of gold steel 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, the flatness of the surface of the plastic base material may be excellent.

According to an exemplary embodiment of the present invention, by using a wire saw including a plurality of wires coated with abrasive containing the gold steel particles, the degree of damage to the surface of the plastic base material is remarkably low and a plastic substrate free of foreign matter is formed on the surface. 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 'and driven. Since the plurality of wires 200 are wound on 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 be rotated in both directions. According to an exemplary embodiment of the present invention, after rotating the pair of guide rollers 100 and 100 'in one direction, the wire saw may be repeatedly cut and rotated in the opposite direction.

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. Specifically, the traveling speed of the wire saw may be 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 manufacturing efficiency of the plastic substrate may be improved.

Further, according to an exemplary embodiment of the present invention, the speed at which the plastic ingot moves and is cut by a 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 variation 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 can 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. The maximum thickness deviation of the plastic base material may be, specifically, 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 can be manufactured.

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

A number of plastic substrates manufactured according to an exemplary embodiment of the present invention may have a maximum thickness deviation of 5 μm or less. 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 of uniform thickness.

The degree of bending of the plastic substrate manufactured according to an exemplary embodiment of the present invention may be 50 μm or less. When the degree of deflection of the substrate is within the above range, the light guide plate made of the substrate can maintain a constant total reflection angle of light flowing from the light source to secure a high quality exit image image.

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

The light guide plate manufactured using the plastic substrate manufactured according to the exemplary embodiment of the present invention may be used in augmented reality devices, virtual reality devices, mobile phones, navigation devices, electronic devices using liquid crystal display devices such as TVs. Specifically, a light emitting device using the light guide plate; Reflective sheet; The light guide plate; Diffusion sheet and; A liquid crystal display device including a backlight unit sequentially provided with prism sheets can be manufactured.

The light emitting device serves to provide light, and the reflective sheet serves to reflect the light exiting from the bottom of the light guide plate back to the light guide plate. In addition, the diffusion sheet is located on the top surface of the light guide plate and scatters light exiting from the surface of the light guide plate in a predetermined direction to spread evenly across 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 described in detail to specifically describe the present invention. However, the embodiments according to the present invention may be modified in various other forms, and the scope of the present invention is not interpreted to be limited to the embodiments described below. The embodiments of the present specification are provided to more fully describe the present invention to those skilled in the art.

Example  One

The plastic ingot was fixed to an 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 thermoset of sulfur-containing urethane-based resin and sulfur-containing epoxy-based resin. A plurality of wires are wound in a plurality of grooves formed at 1.7 mm intervals 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 buried with an abrasive prepared by mixing a gold steel yarn having an average particle size of 3 μm and a water-soluble oil in a weight ratio of 1: 1. Five plastic base materials were prepared by cutting the plastic ingot with a wire saw comprising the plurality of wires.

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

Using a polishing machine (Suzhou HRT Co., Ltd., rotation speed: 25 rpm, pressure: 0.1 MPa), the plastic base material is first polished with a Ce pad (using a powder type abrasive containing CeO ₂ ), and second polished with a melting pad. A plastic substrate having a thickness of 1.3 mm was manufactured 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 traveling speed of the wire saw wound on 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, since the thickness variation was large and the surface was rough, the polishing process was impossible, so that a plastic substrate could not be produced.

plastic Base material  And evaluation of the maximum thickness deviation of the substrate

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

Evaluation of substrate warpage

The height at 25 points of the plastic substrates of Examples and Comparative Examples was measured using a non-contact type three-dimensional measuring device (Dukin Corporation, PLUTO), and the maximum deviation of the height of the plastic substrate was calculated from the measured values to evaluate the degree of warpage. The height is the relative height of the substrate measured through the distance from the measurement sensor portion of the non-contact type 3D measuring device to the substrate.

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

Plastic base material Plastic substrate Thickness of five points (㎛) Maximum thickness deviation
(㎛) Thickness of five points (㎛) Maximum thickness deviation
(㎛) 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 Measurement not possible

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

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

Claims (8)

A pair of guide rollers spaced apart and rotating; A wire saw including a plurality of wires spaced parallel to each other and wound on the pair of guide rollers; And a method for manufacturing a plastic substrate for a light guide plate using a wire saw cutting device including an ingot fixing unit positioned at an upper or lower portion of the wire saw.
The method comprises 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,
The wire saw has a traveling speed of 350 m / min or more and 650 m / min or less,
The plastic ingot has a cutting speed of 230 μm / min or more and 300 μm / min or less.
According to claim 1,
The plastic ingot is a method of manufacturing a plastic substrate for a light guide plate manufactured from at least one selected from carbonate-based resin, acrylate-based resin, urethane-based resin and 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 plurality of wires are spaced apart at a distance of 0.8 mm or more and 2.0 mm or less, and a method of manufacturing a plastic substrate for a light guide plate.
According to claim 1,
The plurality of wires is a method of manufacturing a plastic substrate for a light guide plate, which is a wire coated with an abrasive.
The method of claim 6,
The abrasive is a method of manufacturing a plastic substrate for a light guide plate comprising gold steel particles.
According to claim 1,
The plastic base material is a method for manufacturing a plastic substrate for a light guide plate having a maximum thickness deviation of 10 μm or less.

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