Cutting methods for brittle material substrates

Abstract

This invention provides a method for cutting brittle material substrates that extends the lifespan of diamond cutting tools. The method involves coating a liquid containing a volatile solvent and a polymer compound onto a brittle material substrate G along a predetermined cutting line L, pressing the tip P of a diamond cutting tool 1 against the predetermined cutting line L, causing the brittle material substrate G and the cutting tool 1 to move relative to each other, thereby performing the cutting.

Description

[Technical Field]

[0001] This invention relates to a method for cutting brittle material substrates, which uses a diamond-tipped cutting tool to cut brittle material substrates such as glass substrates or silicon wafers. [Previous Technology]

[0002] Generally, glass substrates or silicon wafers are cut using a cutting tool employing a cutting wheel or single-crystal diamond. The single-crystal diamond cutting tool has a diamond at its tip, which serves as the contact point with the substrate. By moving the cutting tool in a straight line, a cutting line is formed at the tip (see, for example, Patent Document 1). [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-65245 [Summary of the Invention]

[0004] [Problem to be Solved by the Invention] In existing cutting methods using cutting tools, there is a problem that the diamond used for the cutting tip wears down with use, thus failing to achieve sufficient wire-forming performance. Furthermore, in recent years, with the lightweighting and foldability of mobile phone terminals and the continuous development of ultra-thin cover glass, high-strength diamonds have been developed for cutting ultra-thin glass sheets with a thickness of less than 100 μm. While high-strength diamonds can perform precision cutting, they also suffer from a short lifespan.

[0005] This invention was made in view of the problems described above, and its objective is to provide a method for cutting brittle material substrates that can achieve a long lifespan for diamond cutting of brittle material substrates. [Means for Solving the Problem]

[0006] The problem to be solved by the present invention is as described above, and the method for solving the problem will be described thereafter.

[0007] That is, the method for cutting brittle material substrates of the present invention is characterized in that: a liquid containing a volatile solvent and a polymer compound is applied to the brittle material substrate along a predetermined cutting line; the tip of a diamond cutting tool is pressed against the predetermined cutting line, causing the brittle material substrate and the cutting tool to move relative to each other, thereby performing cutting. As described above, in the method for cutting brittle material substrates of the present invention, applying a liquid containing a volatile solvent and a polymer compound along the predetermined cutting line can remove dust adhering to the predetermined cutting line, improve the lubricity between the brittle material substrate and the cutting tool tip, thereby reducing wear on the diamond used in the tip. This achieves a longer diamond lifespan, thus reducing the cost of tip replacement.

[0008] Furthermore, in the cutting method for the brittle material substrate of the present invention, it is preferable that the viscosity of the volatile solvent is lower than that of the polymer compound. By having this structure, stickiness after coating can be suppressed, thus eliminating the need for a cleaning step.

[0009] Furthermore, in the cutting method of the brittle material substrate of the present invention, it is preferable that the polymer compound is a water-soluble polymer compound. By having this structure, liquid can be applied in a way that prevents stains and dust from adhering after drying.

[0010] Furthermore, in the cutting method of the brittle material substrate of the present invention, the solvent is preferably ethanol, and the polymer compound is polyethylene glycol. By having this structure, the lubricity can be improved by polyethylene glycol, and the stickiness can be suppressed by the highly volatile nature of ethanol, thereby improving the machinability.

[0011] Furthermore, in the cutting method for the brittle material substrate of the present invention, it is preferable that the concentration of the polymer compound in the liquid is 1.0% by mass or less. By adopting this structure, lubricity can be ensured, and stickiness can be suppressed by the volatility of the solvent, thereby improving machinability.

[0012] Furthermore, in the cutting method of the brittle material substrate of the present invention, the solvent is preferably ethanol, and the polymer compound is polyethylene glycol. By having this structure, the lubricity can be improved by polyethylene glycol, and the stickiness can be suppressed by the highly volatile nature of ethanol, thereby improving the machinability.

[0013] Furthermore, in the method for cutting a brittle material substrate according to the present invention, the brittle material substrate is preferably a glass substrate. After cutting the brittle material substrate, in order to easily and with high quality break the cut surface, a predetermined load must be applied to the tip of the substrate during cutting to form a cutting line with a fixed depth relative to the glass thickness. However, since the glass substrate has a high hardness, in order to obtain a cutting line of the required depth, the load on the base member must be increased, and consequently, lubrication is hindered when the base member contacts the glass surface. As a result, the wear of the base member increases, and the life of the cutting tool is shortened. By having a structure like the present invention, even for glass substrates that are prone to problems such as the need to apply a high load during cutting leading to a shortened life of the base member of the cutting tool, a long life of the base member can be achieved. The type of glass substrate used as the brittle material substrate is not specifically specified. Non-alkali glass substrates for displays and chemically strengthened glass substrates can be used appropriately. The concentration and molecular weight of polyethylene glycol in the liquid can also be adjusted appropriately according to the firing characteristics of the glass substrate used.

[0014] Furthermore, in the cutting method for the brittle material substrate of the present invention, it is preferable that the thickness of the glass substrate is 300 μm or less. If the thickness of the glass substrate is thin, the surface strength of the glass substrate is low, thus the conditions for cutting the glass substrate are very limited. If the load is excessively increased, the glass substrate is more likely to be damaged due to the load. On the other hand, if the load is reduced to prevent breakage, the cutting line becomes thinner, making it difficult to break the cut glass, or making it difficult to obtain a uniform cut surface when breaking, which easily leads to a decrease in the straightness of the cut line of the cut glass, thereby reducing the strength of the cut surface. According to the present invention, the above problems can be solved for cutting. [Effects of the Invention]

[0015] As an effect of the present invention, the following effects are achieved. That is, the cutting method for brittle material substrates according to the present invention can remove dust adhering to the predetermined cutting line, improve the lubricity between the brittle material substrate and the cutting tool tip, thereby reducing the wear of the diamond tip. This extends the lifespan of the diamond tip, thus reducing the cost of replacing the tip.

Implementation Method

[0017] Next, embodiments of the present invention will be described using FIG1A and FIG1B.

[0018] [Structure of the Cutting Tool] First, the structure of the cutting tool used in the cutting method for the brittle material substrate of the present invention will be described using FIGS. 1A and 1B. The cutting tool 1 is a device that forms a cutting line by abutting the tip P against a predetermined cutting line L of the brittle material substrate G. As shown in FIGS. 1A and 1B, the cutting tool 1 includes: a tool body 2 movable in the cutting direction, a base member 3 mounted on a corner post of the tool body 2, and a coating member 4 coated with a liquid containing a volatile solvent and a polymer compound.

[0019] The tool body 2 is disposed above the brittle material substrate G and is configured to move parallel to the surface of the brittle material substrate G. The tool body 2 is supported so that it can move horizontally on the operating table 11 on which the brittle material substrate G is disposed. The horizontal movement of the tool body 2 relative to the operating table 11 is controlled by a control device (not shown), and in this embodiment, it is configured to move horizontally along a predetermined cutting line L that cuts the brittle material substrate G. The brittle material substrate G is a plate-shaped member that is prone to breakage along scratches (cracks), and is made of, for example, a glass substrate. As a glass substrate, alkali-free glass, silicate glass, silicate oxide glass, and borosilicate glass can be used, for example. When the brittle material substrate G is a glass substrate, the thickness is preferably 300 μm or less. It is especially preferable for glass substrates with a thickness of 200 μm or less, i.e., so-called ultra-thin glass substrates. When cutting ultrathin glass substrates, a load needs to be applied to the substrate member 3 to obtain a high-quality, high-strength cut surface. However, due to the low surface strength of ultrathin glass, the conditions for achieving the cut become very limited. If the load is excessively increased, the glass substrate is more likely to be damaged due to the load. On the other hand, if the load is reduced to prevent breakage, the cut line becomes thinner. Therefore, it is difficult to break the cut glass, or it is difficult to obtain a uniform cut surface when breaking it, which easily leads to a decrease in the straightness of the cut line and thus a decrease in the strength of the cut surface. This method can be applied to glass substrates with a thickness preferably less than 100 μm, and more preferably less than 50 μm. Furthermore, the thickness of the glass substrate is preferably more than 10 μm.

[0020] The substrate component 3 is formed of single-crystal diamond. Furthermore, the raw materials for the substrate component 3 are not limited to this embodiment. For example, it may be polycrystalline diamond synthesized by chemical vapor deposition (CVD), polycrystalline diamond formed by sintering graphite particles or non-graphite carbon without containing binders such as iron group elements, or sintered diamond formed by bonding diamond particles with binders such as iron group elements.

[0021] The base member 3 may be formed of single-crystal diamond, except for the portion of the tip P that forms the cutting line. Other portions may be formed of metal or ceramic. The base member 3 is fixed to the side of the tool body 2 by means of screws or other fixing components. The base member 3 is formed of a polygonal prism with one or more vertices. The tip P is formed at the ridge of one or more vertices of the polygonal prism of the base member 3 that contacts the brittle material substrate G. The tip P is formed of the angular portion of single-crystal diamond and is configured to form a cutting line on the surface of the brittle material substrate G.

[0022] The coating member 4 is a member for coating a liquid containing a volatile solvent and a polymer compound onto the surface of a brittle material substrate G. The coating member 4 includes a liquid storage section 4a for storing the coating liquid and a coating section 4b for coating the liquid along a predetermined cutting line L of the brittle material substrate. The coating member 4 is held by the coating member holding section 2a of the tool body 2. In this embodiment, the coating section 4b is made of a fibrous material and is in direct contact with the predetermined cutting line L of the brittle material substrate G for coating. The coating section 4b has a cross-sectional area capable of coating the predetermined cutting line L with lubricant in a width of 1 mm to several mm.

[0023] The liquid applied by the coating member 4 is a lubricant. The lubricant comprises a liquid containing a volatile solvent and a polymer compound. The volatile solvent is preferably a colorless and transparent liquid, and in this embodiment, it is ethanol. Furthermore, the solvent is not limited to ethanol; ideally, it is a solvent whose evaporation rate from coating to cutting is slower than the cutting rate from coating to cutting. Moreover, the solvent is a substance with a viscosity lower than that of the polymer compound. Because the solvent has a low viscosity, the stickiness after applying the lubricant can be suppressed, thus eliminating the need for a cleaning step.

[0024] The polymer compound is a viscous liquid or semi-solid substance, and in this embodiment, it is polyethylene glycol (PEG). PEG has the property that its viscosity increases with increasing average molecular weight. The polymer compound is formed with a molecular weight at least greater than that of the solvent. By using PEG, which has a higher viscosity, a lubricating film is easily formed. In this embodiment, it is preferable to select a polymer compound with an average molecular weight of 10,000 or more but less than 100,000.

[0025] Furthermore, the polymer compound is not limited to polyethylene glycol. For example, in addition to natural polymers such as protein and starch, surfactants with high molecular chains such as cationic, anionic, or nonionic surfactants, polyacrylic acid, polyacrylamide, polyethylene oxide, polyvinyl pyrrolidone, and polyvinyl alcohol can also be used to synthesize polymers, as long as they are water-soluble polymer compounds that can be washed away with water after coating.

[0026] As a lubricant, for example in the case of PEG, the concentration of PEG in ethanol is preferably 1.0% by mass or less. The concentration of PEG in ethanol is further preferably 0.5% by mass or less. The concentration of PEG in ethanol is further preferably 0.2% by mass or less. This effectively suppresses the residue of PEG after the volatile ethanol evaporates.

[0027] [Cutting Method Using a Cutting Tool] Next, the cutting method using the cutting tool 1 will be described using FIG. 2. First, a glass substrate, which is a brittle material substrate G, is placed on the operating table 11 (step S10). Next, the coating portion 4b of the coating member 4 mounted on the tool body 2 is brought into contact with a point on the predetermined cutting line L of the brittle material substrate G (step S20). Next, the tip P of the substrate member 3 is brought into contact with the starting point on the predetermined cutting line L (step S30). Next, the tool body 2 is moved parallel to the predetermined cutting line L (step S40).

[0028] Cutting is performed by moving the tool body 2 parallel to the predetermined cutting line L using the tip P. Lubricant is pre-applied to the tool body 2 in the direction of travel of the tool body 2 along the predetermined cutting line L using a coating member. The tip P of the base member 3 forms a cutting line along the predetermined cutting line L through the portion of the coating section 4b coated with lubricating material. The lubricating effect of the applied lubricating material significantly reduces wear on the tip P of the base member 3, thereby extending the lifespan of the cutting tool.

[0029] Furthermore, the lubricating material is applied to the predetermined cutting line L by the coating member 4, thereby removing foreign matter from the predetermined cutting line L by the coating section 4b. The coating section 4b is made of fibrous material, and removes foreign matter from the predetermined cutting line L by allowing fine dust to enter the gaps between the fibers.

[0030] [Structure of a Cutting Tool According to Another Embodiment] Next, the structure of a cutting tool according to another embodiment will be described using FIGS. 4A and 4B. The cutting tool 51 is a device that forms a cutting line by bringing its tip P against a predetermined cutting line L of a brittle material substrate G. As shown in FIGS. 4A and 4B, the cutting tool 51 includes: a tool body 52 movable in the cutting direction, a base member 53 mounted on a corner post of the tool body 52, and a coating member 54 coated with a liquid containing a volatile solvent and a polymer compound.

[0031] The tool body 52 is disposed above the brittle material substrate G and is configured to move parallel to the surface of the brittle material substrate G. The tool body 52 is configured to move horizontally with the operating table 11 on which the brittle material substrate G is disposed, and to move in the forward, backward, left, and right directions when viewed from above. For example, the tool body 52 is supported by a gate-shaped support member 52a that moves in the forward and backward direction. A rail is provided on the long side member of the gate-shaped support member 52a in the left and right direction, and the tool body 52 is supported so that it can slide relative to the rail. In this way, the gate-shaped support member 52a is moved in the forward and backward direction, and the tool body 52 is moved in the left and right directions along the rail, thereby configuring the tool body 52 to move in the forward, backward, left, and right directions when viewed from above. The horizontal movement of the tool body 52 relative to the operating table 11 is controlled by a control device (not shown), and in this embodiment, it is configured to move horizontally along a predetermined cutting line L that cuts the brittle material substrate G. The brittle material substrate G is a plate-shaped member that has the property of easily breaking along scratches (cracks), for example, it is made of a glass substrate. For example, alkali-free glass, silicate glass, silicate glass, and borosilicate glass can be used as the glass substrate. When the brittle material substrate G is a glass substrate, the thickness is preferably 300 μm or less.

[0032] The substrate component 53 is formed of single-crystal diamond. Furthermore, the raw materials for the substrate component 53 are not limited to this embodiment. For example, it may be polycrystalline diamond synthesized by chemical vapor deposition (CVD), polycrystalline diamond sintered from a binder of micro-graphite or non-graphitic carbon without iron group elements, or sintered diamond formed by binding diamond particles with binders such as iron group elements.

[0033] The base member 53 may be formed of single-crystal diamond, except for the portion containing the tip P that forms the cutting line; other portions may be formed of metal or ceramic. The base member 53 is fixed to the side of the tool body 52 by a fixing member such as a screw. The base member 53 is formed of a polygonal prism having one or more vertices. The tip P is formed at the ridge of one or more vertices of the polygonal prism of the base member 53 that contacts the brittle material substrate G. The tip P is formed of the angular portion of single-crystal diamond, configured to form a cutting line on the surface of the brittle material substrate G.

[0034] The coating member 54 is a member for coating a liquid containing a volatile solvent and a polymer compound onto the surface of a brittle material substrate G. The coating member 54 includes a liquid storage section 54a for storing the coating liquid and a coating section 54b for coating the liquid along a predetermined cutting line L of the brittle material substrate. The coating member 54 is held by the coating member holding section 52b of the tool body 52.

[0035] The coating member holding portion 52b includes a rotating holding portion 52c and a support shaft 52d. The rotating holding portion 52c is configured to rotate about the support shaft 52d in an axial direction. The rotating holding portion 52c is a member that holds the coating member 54. By rotating the rotating holding portion 52c about the axis, the posture of the coating member 54 also rotates about the axis. Moreover, the rotating holding portion 52c is configured to be fixed in a rotating posture by a fixing screw (not shown). In this way, the coating member 54 is fixed in an inclined posture, and compared with the upright posture, the coating portion 54b can be positioned closer to the substrate member 53.

[0036] The coating portion 54b of the coating member 54 has a cross-sectional area capable of coating lubricant in a width of 10 mm to 20 mm on the predetermined cutting line L. Therefore, when the tip P moves in a direction different from the front-back direction (left-right direction), the coating portion 54b can also coat a liquid containing volatile solvents and polymer compounds. For example, when the predetermined cutting line L of the brittle material substrate G is located in an inclined direction when viewed from above, as shown in FIG4B, the coating can completely cover the direction in which the tip P moves.

[0037] [Example] Next, a verification experiment for determining the effectiveness of the cutting method for the brittle material substrate G in realizing the present invention will be described.

[0038] In the verification experiment, a brittle material substrate G (Example 1: unwashed, Example 2: pre-cleaned before cutting, Example 3: unwashed) was used. Furthermore, the mixing ratio of ethanol and PEG contained in the lubricant was set as shown in Table 1. PEG300 was used.

[0039] [Table 1] ethanol (ml) PEG300 (ml) PEG concentration (%) (Volume ratio) Lubricant 1 99.9 0.1 0.1 Lubricant 2 99.95 0.05 0.05

[0040] The lubricant is stored in the liquid storage section 4a of the coating member 4 installed on the tool body 2. Then, the coating section 4b of the coating member 4 is brought into contact with a point on the predetermined cutting line L of the brittle material substrate G, thereby applying the lubricant. The tool body 2 is then moved parallel to the predetermined cutting line L, thereby performing cutting via the tip P. Furthermore, in Examples 1 and 2, lubricant 1 is applied, and in Example 3, lubricant 2 is applied.

[0041] The life test results of the base member 3 used in this cutting method are shown in Table 2. Furthermore, the test results of the comparative example, in which no lubricant is applied by means of the coated member, are also shown.

[0042] [Table 2] Types of glass Example 1 (Apply lubricant 1) Lifespan [m] Example 2 (Apply lubricant 1) Lifespan [m] Example 3 (Apply lubricant 2) Lifespan [m] Comparative example (No lubricant applied) Lifespan [m] Glass More than 1000 More than 6000 2000 and above 350

[0043] As shown in Table 2, when cutting uncoated plain glass, if no lubricant is applied during the cutting process, the lifespan of the base component 3 is about 350 m. In contrast, if a lubricant is applied during the cutting process, the lifespan of the base component 3 is extended to more than 1,000 m in Example 1, more than 6,000 m in Example 2, and more than 2,000 m in Example 3.

[0044] Based on the above results, by applying lubricating material to the predetermined cutting line L by the coating member 4, the wear of the tip P of the base member 3 can be greatly reduced, thereby extending the life of the cutting tool.

[0045] As described above, the present invention involves coating a brittle material substrate G with a liquid containing a volatile solvent and a polymer compound along a predetermined cutting line L, pressing the tip P of a diamond cutting tool 1 against the predetermined cutting line L, and causing the brittle material substrate G and the cutting tool 1 to move relative to each other, thereby performing cutting. With this configuration, the liquid lubricant can improve the lubricity between the brittle material substrate G and the tip P of the cutting tool 1, thereby reducing the wear of the diamond cutting tool used at the tip P. [Industrial Applicability]

[0046] The present invention relates to a technique for cutting brittle material substrates, wherein the technique involves using the tip of a diamond cutting tool to cut brittle material substrates such as glass substrates or silicon wafers. [Simplified Explanation of the Diagram]

[0016] FIG1A is a front view of a cutting tool according to one embodiment of the present invention, and FIG1B is a top view. FIG2 is a flowchart showing the cutting steps according to one embodiment of the present invention. FIG3 is a front cross-sectional view of a laminated brittle material substrate according to one embodiment of the present invention. FIG4A is a front view of a cutting tool according to another embodiment of the present invention, and FIG4B is a top view.

Claims

1. A method for cutting a brittle material substrate, characterized in that a liquid containing a volatile solvent and a polymer compound is applied to the brittle material substrate along a predetermined cutting line, and the tip of a diamond cutting tool is pressed against the predetermined cutting line to move the brittle material substrate relative to the cutting tool, thereby performing cutting, wherein the concentration of the polymer compound in the liquid is less than 1.0% by mass.

2. The method for cutting a brittle material substrate as described in claim 1, wherein the viscosity of the volatile solvent is lower than that of the polymer compound.

3. The method for cutting a brittle material substrate as described in claim 2, wherein the polymer compound is a water-soluble polymer compound.

4. A method for cutting a brittle material substrate as described in any one of claims 1 to 3, wherein the concentration of the polymer compound in the liquid is less than 0.5% by mass.

5. A method for cutting a brittle material substrate as described in any one of claims 1 to 3, wherein the concentration of the polymer compound in the liquid is less than 0.2% by mass.

6. The method for cutting a brittle material substrate as described in claim 3, wherein the solvent is ethanol and the polymer is polyethylene glycol.

7. A method for cutting a brittle material substrate as described in any one of claims 1 to 3, wherein the brittle material substrate is a glass substrate.

8. The method for cutting a brittle material substrate as described in claim 7, wherein the thickness of the glass substrate is 300 μm or less.

Images