Disk-shaped glass substrate

Abstract

To enable stable mass production of a thin plate glass substrate having a high surface quality and a highly accurate plate thickness.SOLUTION: A disk-shaped glass substrate is for cutting out one or a plurality of thin plate glass substrates. The disk-shaped glass substrate includes two circular main surfaces, an outer peripheral end face, and a beveling face connecting each of the two circular main surfaces and the outer peripheral end face, and forming a straight line in the lateral view, and has a refraction index of 1.60 or more. The beveling face forming the straight line is formed by beveling the edge of a disk-shaped glass blank having a plate thickness greater than that of the disk-shaped glass substrate so as to form the straight line, and grinding and polishing the two main surfaces of the beveled disk-shaped glass blank by using a double-side grinding device and a double-side polishing device.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a disk-shaped glass substrate.

Background Art

[0002] Some head-mounted displays can provide augmented reality by superimposing an image on a landscape for display. In this type of head-mounted display, a light guide made of glass having translucency may be employed in the display unit.

[0003] For example, Patent Document 1 discloses a light guide including a glass plate. As described in Patent Document 1, since a head-mounted display is worn on the head and thus weight reduction is required, it is desirable that the glass plate applied to the light guide has a thin thickness. Further, in order to display a high-resolution image, for example, a glass plate having high surface quality in terms of flatness, surface roughness, etc. of the two main surfaces of the glass plate is desirable.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, generally, it is difficult to stably mass-produce a glass plate with a thin thickness (hereinafter referred to as a "thin glass substrate") with high surface quality.

[0006] For example, when manufacturing a thin glass substrate with a large size and high surface quality, the size of the glass substrate (hereinafter referred to as "glass blank") used as the material also becomes large. In such a large glass blank, the frictional force applied to the main surface to be processed in processes such as grinding and polishing tends to be uneven. Therefore, the surface quality and plate thickness become uneven, and it is particularly difficult to process the glass blank thinly with high surface quality and high precision in a large glass blank.

[0007] In addition, in a large glass blank, when installing the glass blank in each device for performing grinding, polishing, etc., or when handling the glass blank before and after the processing steps such as when transporting the glass blank between those devices, the glass blank is likely to be damaged. Therefore, the yield when manufacturing a large and high-surface-quality thin glass substrate is extremely low.

[0008] For another example, when manufacturing a thin glass substrate having corners such as a rectangular thin glass substrate, usually, it is manufactured by processing a glass blank having corners. In this case, particularly in the vicinity of the corners, the frictional force applied to the surface to be processed in processes such as grinding and polishing tends to be uneven. Therefore, it is extremely difficult to process thinly with high surface quality and high precision in a glass blank having corners.

[0009] Even if a thin glass substrate having corners is cut out from a thin glass substrate with a larger size, in the manufacture of a large thin glass substrate, as described above, the surface quality and plate thickness tend to be uneven. Therefore, the thin glass substrate having the cut-out corners is likely to have variations in surface quality and plate thickness depending on where it is cut out from the large thin glass substrate. Also, as described above, the yield when manufacturing a large thin glass substrate is extremely low. Thus, even if the thin glass substrate to be manufactured is cut out from a thin glass substrate with a larger size, it is extremely difficult to stably mass-produce it with high surface quality and high-precision plate thickness.

[0010] The present invention has been made in view of the above circumstances, and an object thereof is to provide a disk-shaped glass substrate that enables stable mass production of thin glass substrates having high surface quality and high-precision plate thickness.

Means for Solving the Problems

[0011] To achieve the above object, a disk-shaped glass substrate according to the present invention is a disk-shaped glass substrate for cutting out one or more thin glass substrates, having two circular main surfaces, an outer peripheral end face, and a chamfered surface that forms a straight line when viewed from the side connecting each of the two main surfaces and the outer peripheral end face, having a refractive index of 1.60 or more, wherein the chamfered surface forming the straight line is formed by chamfering the edge of a disk-shaped glass blank having a plate thickness thicker than the plate thickness of the disk-shaped glass substrate so as to form a straight line, and then grinding and polishing the two main surfaces of the chamfered disk-shaped glass blank using a double-sided grinding device and a double-sided polishing device.

Advantages of the Invention

[0012] According to the present invention, it becomes possible to stably mass-produce thin glass substrates having high surface quality and high-precision plate thickness.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

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Figure 6

Figure 7

Figure 8

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Figure 11

[0014] Hereinafter, one Embodiment of this invention is demonstrated, referring drawings. The same code | symbol is attached | subjected to the same element through all the figures. In the description and drawing of the Embodiment of this invention, although the terms of up, down, front, back, left, and right are used, these are used in order to demonstrate a direction, and are not the meaning which limits this invention. In the figure, the ratio of the dimension of each part is changed suitably in order to make it easy to understand.

[0015] (Configuration of Disk-shaped Glass Substrate 100) As shown in FIG. 1 which is a perspective view and FIG. 2 which is an enlarged cross-sectional view, the disk-shaped glass substrate 100 which concerns on one Embodiment of this invention is a disk-shaped thin glass-made plate. The refractive index of the disk-shaped glass substrate 100 is preferably 1.60 or more.

[0016] Hereinafter, a "thin glass substrate" means a thin glass plate.

[0017] The disk-shaped glass substrate 100 is an intermediate for cutting out one or more thin plate glass substrates that are smaller in size than this. The cut-out thin plate glass substrates are used, for example, singly or in appropriate combinations as a light guide plate. When a plurality of cut-out thin plate glass substrates are combined and used as a light guide plate, typically, the cut-out thin plate glass substrates are laminated and used as a light guide plate. The light guide is applied to, for example, a display device such as a head-mounted display.

[0018] The disk-shaped glass substrate 100 has two main surfaces 101a, 101b, an outer peripheral end surface 102a, and chamfered surfaces 103a, 103b. FIG. 2 is an enlarged view of the cross-section CS1 surrounded by the dashed-dotted line in FIG. 1 as seen from the front shown in FIG. 1. The cross-section CS1 is a surface extending in the vertical direction and the horizontal direction, and is a cross-section along the diameter direction of each of the main surfaces 101a, 101b. Since the cross-section CS1 shown in FIG. 2 is extremely thin, the cross-section CS1 surrounded by the dashed-dotted line appears as a generally thick straight line.

[0019] The two main surfaces 101a, 101b are generally circular planes arranged in the vertical direction. The diameter of each of the two main surfaces 101a, 101b is, for example, 70 [mm (millimeters)] to 210 [mm].

[0020] The vertical length between the two main surfaces 101a, 101b, that is, the plate thickness of the disk-shaped glass substrate 100 excluding the outer peripheral end surface 102a and the chamfered surfaces 103a, 103b is, for example, 50 [μm (micrometers)] to 500 [μm]. Note that the plate thickness of the disk-shaped glass substrate 100 excluding the outer peripheral end surface 102a and the chamfered surfaces 103a, 103b is preferably 100 [μm] to 400 [μm], and more preferably 100 [μm] to 350 [μm].

[0021] The parallelism of the two main surfaces 101a, 101b is, for example, less than 1.0 [μm], preferably 0.95 [μm] or less, and more preferably 0.5 [μm] or less. The parallelism of the two main surfaces 101a, 101b may be 0.05 [μm] or more.

[0022] Here, the parallelism is a value called so-called TTV (Total Thickness Variation), and it is the difference between the maximum value and the minimum value of the lengths over the entire surface of the disk-shaped glass substrate 100 measured in the plate thickness direction (the vertical direction in this embodiment) with one of the main surfaces 101a and 101b as a reference surface.

[0023] The roughness (root mean square roughness) Rq of the two main surfaces 101a and 101b is, for example, 0.4 [nm] or less.

[0024] The outer peripheral end surface 102a is a surface that forms the radial end of the disk-shaped glass substrate 100 and is a curved surface that extends slightly in the vertical direction. Specifically, the outer peripheral end surface 102a generally forms a circle when viewed from above or below, and forms a rectangle that is short in the vertical direction and extremely elongated when viewed from the side. Here, the side is a direction perpendicular to the vertical direction.

[0025] The chamfered surfaces 103a and 103b are surfaces that connect between each of the two main surfaces 101a and 101b and the outer peripheral end surface 102a in an inclined manner and form an annular shape when viewed from above or below. That is, the upper chamfered surface 103a is an annular surface that connects between the outer edge portion 104a of the upper main surface 101a and the upper end portion 105a of the outer peripheral end surface 102a in an inclined manner. The lower chamfered surface 103b is an annular surface that connects between the outer edge portion 104b of the lower main surface 101b and the lower end portion 106a of the outer peripheral end surface 102a in an inclined manner.

[0026] In this embodiment, the chamfered surfaces 103a and 103b form a straight line when viewed from the side (see FIG. 2). Also, since the chamfered surfaces 103a and 103b are "inclined" as described above, they intersect with both of the two main surfaces 101a and 101b and the outer peripheral end surface 102a. The chamfered surfaces 103a and 103b according to this embodiment intersect with both of the two main surfaces 101a and 101b and the outer peripheral end surface 102a at an obtuse angle (see FIG. 2). Note that the chamfered surfaces 103a and 103b may form a curve when viewed from the side.

[0027] So far, the configuration of the disk-shaped glass substrate 100 according to this embodiment has been described.

[0028] The disk-shaped glass substrate 100 according to this embodiment is an intermediate for cutting out one or more thin glass substrates. Further, the disk-shaped glass substrate 100 has a plate thickness of 100 [μm] to 350 [μm] for the portion excluding the outer peripheral end face 102a and the chamfered faces 103a and 103b, and the parallelism of the two main surfaces 101a and 101b is less than 1.0 [μm], having high surface quality and high-precision plate thickness. Therefore, a thin glass substrate having high surface quality and high-precision plate thickness can be cut out.

[0029] In addition, the disk-shaped glass substrate 100 includes the chamfered faces 103a and 103b. Therefore, the possibility of the disk-shaped glass substrate 100 being damaged when cutting out the thin glass substrate is reduced, and the thin glass substrate can be cut out with a higher yield than when there are no chamfered faces 103a and 103b.

[0030] Furthermore, since the disk-shaped glass substrate 100 not only includes the chamfered faces 103a and 103b but is also disk-shaped, as will be described in detail later, even a relatively large thin glass substrate having high surface quality and high-precision plate thickness can be stably manufactured with a high yield.

[0031] Therefore, it becomes possible to stably mass-produce thin glass substrates having a desired shape with high surface quality and high-precision plate thickness.

[0032] Also, the refractive index of the disk-shaped glass substrate 100 may be 1.60 or more, and the parallelism of the two main surfaces 101a and 101b may be 0.5 [μm] or less. According to this, for the same reason as described above, it becomes possible to stably mass-produce thin glass substrates having a desired shape with even higher surface quality and high-precision plate thickness.

[0033] Furthermore, the thin glass substrate cut out from the disk-shaped glass substrate 100 may be a light guide plate used singly or in combination of a plurality by a method such as lamination. According to this, for the same reason as described above, it becomes possible to stably mass-produce a light guide plate having a desired shape with high surface quality and high-precision plate thickness.

[0034] (Manufacturing method of disk-shaped glass substrate 100) Hereinafter, the manufacturing method of the disk-shaped glass substrate 100 as an intermediate will be described.

[0035] The manufacturing method of the disk-shaped glass substrate 100 is a method for manufacturing the disk-shaped glass substrate 100 and includes, for example, the steps shown in the flowchart of FIG. 3.

[0036] A disk-shaped glass blank 107a is prepared (step S1).

[0037] The disk-shaped glass blank 107a is a disk-shaped glass substrate having a thickness thicker than that of the disk-shaped glass substrate 100 manufactured as an intermediate. The plate thickness t1 of the disk-shaped glass blank 107a is, for example, 0.5 [mm] to 1.0 [mm]. The refractive index of the disk-shaped glass blank 107a is preferably 1.60 or more. The accuracy of the plate thickness and the quality of each of the main surfaces 101c and 101d may be lower than those of the disk-shaped glass substrate 100.

[0038] The disk-shaped glass blank 107a has two main surfaces 101c and 101d and an outer peripheral end surface 102b as shown in FIG. 4 which is a perspective view and FIG. 5 which is an enlarged cross-sectional view.

[0039] FIG. 5 is an enlarged view of the cross section CS2 surrounded by the dashed-dotted line in FIG. 4 as viewed from the front shown in FIG. 4. The cross section CS2 corresponds to the cross section CS1 in FIG. 1 and is a plane extending in the vertical direction and the horizontal direction and along the diameter direction of each of the main surfaces 101c and 101d. Since the cross section CS2 shown in FIG. 4 is extremely thin, the cross section CS2 surrounded by the dashed-dotted line appears as a generally thick straight line similar to the cross section CS1 in FIG. 1.

[0040] Such a disk-shaped glass blank 107a may be manufactured by appropriate shaping processes.

[0041] Specifically, for example, the disk-shaped glass blank 107a may be manufactured by cutting out a cylindrical glass from a prism-shaped glass mass formed of a high-refractive-index glass and then slicing it into a disk shape. Also, for example, the disk-shaped glass blank 107a may be manufactured by cutting out a predetermined size from a large glass plate formed by the float process or the down-draw process. Further, for example, the disk-shaped glass blank 107a may be manufactured by press-molding molten glass between a pair of molds.

[0042] Here, chamfers may not be provided on the outer edge portions 104c and 104d that form the outer edges of the main surfaces 101c and 101d of the disk-shaped glass blank 107a, respectively. That is, each of the main surfaces 101c and 101d of the disk-shaped glass blank 107a and the outer peripheral end surface 102b intersect at the outer edge portions 104c and 104d. In other words, each of the outer edge portions 104c and 104d is a portion that generally forms a linear boundary between the main surfaces 101c and 101d of the disk-shaped glass blank 107a and the outer peripheral end surface 102b, and forms a ridge line. In the present embodiment, when viewed from the side, each of the main surfaces 101c and 101d and the outer peripheral end surface 102b intersect at a substantially right angle (see FIG. 5).

[0043] Note that, for example, when viewed from the side, each of the main surfaces 101c and 101d may be curved, or the outer peripheral end surface 102b may be curved in the vertical direction, etc., so that each of the main surfaces 101c and 101d and the outer peripheral end surface 102b intersect at an acute angle.

[0044] Referring again to FIG. 3. Chamfering is performed on the disk-shaped glass blank 107a (step S2). In the chamfering step (step S2), the outer edge portions 104c and 104d of each of the two main surfaces 101c and 101d of the disk-shaped glass blank 107a are chamfered.

[0045] By performing the chamfering process (step S2), the outer edge portions 104c and 104d that are the boundaries between the main surfaces 101c and 101d and the outer peripheral end surfaces 102b of the disk-shaped glass substrate 107a are removed. Then, as shown in FIG. 6 which is an enlarged cross-sectional view, chamfered surfaces 103c and 103d that are the surfaces connecting the main surfaces 101e and 101f of the disk-shaped glass substrate 107b to the outer peripheral end surface 102c are formed on the disk-shaped glass substrate 107b.

[0046] Specifically, the upper chamfered surface 103c is an annular surface that connects between the outer edge portion 104e of the upper main surface 101e and the upper end portion 105b of the outer peripheral end surface 102c in an inclined manner. The lower chamfered surface 103d is an annular surface that connects between the outer edge portion 104f of the lower main surface 101d and the lower end portion 106b of the outer peripheral end surface 102c in an inclined manner.

[0047] In the present embodiment, as shown in FIG. 6, chamfered surfaces 103c and 103d that form a straight line when viewed from the side are formed on the disk-shaped glass substrate 107b.

[0048] Such a chamfering process (step S2) is performed by, for example, mechanical processing such as grinding using a grindstone. The grinding surface of the grindstone is preferably set at an inclination angle of 30 to 60 degrees, preferably 45 degrees, with respect to each of the two main surfaces 101c and 101d. Thereby, the angles formed between the main surfaces 101e and 101f and the chamfered surfaces 103c and 103d when viewed from the side, and the angles formed between the outer peripheral end surface 102c and the chamfered surfaces 103c and 103d when viewed from the side are formed as obtuse angles of 120 to 150 degrees, preferably 135 degrees.

[0049] Here, FIG. 6 is a view showing an enlarged cross-section near the left end of the disk-shaped glass substrate 107b after the chamfering process (step S2) is performed, that is, the chamfered disk-shaped glass substrate 107b, as viewed from the front. Although the position and range of the cross-section in the disk-shaped glass substrate 107b here are not shown, similar to FIGS. 2 and 5, it is a surface extending in the vertical and horizontal directions and is a cross-section along the diameter direction of each of the main surfaces 101e and 101f.

[0050] In Fig. 6, an enlarged cross-section of the disk-shaped glass blank 107b is shown by a solid line. Also in Fig. 6, for comparison, an enlarged cross-sectional view (corresponding to the enlarged cross-sectional view shown in Fig. 5) of the disk-shaped glass blank 107a before chamfering prepared in step S1 is shown by a dashed-dotted line. Further in Fig. 6, for comparison, an enlarged cross-sectional view (corresponding to the enlarged cross-sectional view shown in Fig. 2) of the disk-shaped glass substrate 100 manufactured as an intermediate is shown by a dotted line.

[0051] As described above, each of the enlarged views of the disk-shaped glass blanks 107a and 107b and the disk-shaped glass substrate 100 shown in Fig. 6 shows a cross-section viewed from the front of generally the same position and range throughout each of the disk-shaped glass blanks 107a and 107b and the disk-shaped glass substrate 100. That is, Fig. 6 is arranged such that the planes cutting the vertical centers of each of the disk-shaped glass blanks 107a and 107b and the disk-shaped glass substrate 100 overlap each other, and the centers of the main surfaces 101a to 101f viewed from the vertical direction coincide, and shows an enlarged cross-section when corresponding portions of each of the disk-shaped glass blanks 107a and 107b and the disk-shaped glass substrate 100 are viewed from the front.

[0052] As can be seen from Fig. 6, the diameter of each of the main surfaces 101e and 101f of the disk-shaped glass blank 107b and the vertical length of the outer peripheral end face 102c are shorter than the diameter of each of the main surfaces 101c and 101d of the disk-shaped glass blank 107a prepared in step S1 and the vertical length of the outer peripheral end face 102b, respectively, as a result of the chamfering process (step S2).

[0053] Also, the outer peripheral end face 102c of the disk-shaped glass blank 107b and its upper end portion 105b and lower end portion 106b generally coincide with the outer peripheral end face 102a of the disk-shaped glass substrate 100 which is an intermediate and its upper end portion 105a and lower end portion 106a, respectively, as shown in Fig. 6. A part of the upper and lower chamfered surfaces 103c and 103d of the disk-shaped glass blank 107b generally coincides with the upper and lower chamfered surfaces 103a and 103b of the disk-shaped glass substrate 100 which is an intermediate, respectively, as shown in Fig. 6.

[0054] Also, referring to FIG. 6, when the plate thickness other than the outer peripheral end face 102c and the chamfered faces 103c and 103d of the chamfered disk-shaped glass substrate 107b is t1 [mm], and the plate thickness of the outer peripheral end face 102c of the chamfered disk-shaped glass substrate 107b is t2 [mm], the following formula (1) is satisfied. t1 × 0.15 < t2 < t1 × 0.4 ····· formula (1)

[0055] Note that the chamfering step (step S2) is not limited to mechanical processing, and may be performed by chemical processing such as etching. Chamfered faces 103c and 103d that form a curve when viewed from the side may be formed.

[0056] Referring to FIG. 3 again. Grinding is performed on the two main surfaces 101e and 101f of the chamfered disk-shaped glass substrate 107b (step S3). The grinding step (step S3) is mainly performed for the purpose of adjusting the plate thickness of the disk-shaped glass substrate 107b and adjusting the flatness and parallelism of the two main surfaces 101e and 101f of the disk-shaped glass substrate 107b.

[0057] The removal amount by the grinding step (step S3) is, for example, about 120 [μm] to 400 [μm]. Here, the removal amount means the vertical length of the portion removed in this step.

[0058] In the grinding step (step S3), for example, the two main surfaces 101e and 101f of the chamfered disk-shaped glass substrate 107b are simultaneously ground using the double-sided grinding device 108 shown in FIG. 7.

[0059] FIG. 7 shows the configuration of the double-sided grinding device 108. With reference to this figure, a method of grinding the main surfaces 101e and 101f of the disk-shaped glass substrate 107b in the grinding step (step S3) will be described.

[0060] As shown in FIG. 7, the double-sided grinding device 108 includes a lower fixed disk 109, an upper fixed disk 110, an internal gear 111, a sun gear 112, and a generally disk-shaped carrier 113 provided with holding holes.

[0061] On each of the upper surface of the lower platen 109 and the lower surface of the upper platen 110, a diamond sheet (not shown) is adhesively bonded flat. The surface of this diamond sheet serves as the grinding surface. The particle size of the fixed abrasive grains is, for example, about 10 [μm].

[0062] The internal gear 111 is a generally hollow annular member having a tooth profile provided on its inner surface. The sun gear 112 is a generally cylindrical member disposed at the center of the internal gear 111 and having a tooth profile provided on its outer peripheral surface.

[0063] The carrier 113 is a holding member that holds the disk-shaped glass substrate 107b by holding holes. Specifically, the disk-shaped glass substrate 107b is housed so that its outer peripheral end face 102c is generally in close contact with the wall surface forming the holding holes of the carrier 113, and thus is held by the carrier 113 as shown in FIG. 7.

[0064] In addition, teeth are provided on the outer peripheral surface of the carrier 113. The carrier 113 holding the disk-shaped glass substrate 107b is arranged so that the teeth of the carrier 113 mesh with the respective teeth between the internal gear 111 and the sun gear 112. FIG. 7 shows an example in which four carriers 113 are arranged between the internal gear 111 and the sun gear 112.

[0065] Note that the number of carriers 113 arranged in the double-sided grinding device 108 is not limited to four, and may be one, two, three, or five or more. Also, the number of disk-shaped glass substrates 107b held by one carrier 113 is not limited to one, and may be a plurality.

[0066] The disk-shaped glass blank 107b held by the carrier 113 is clamped between the lower fixed plate 109 and the upper fixed plate 110 at a predetermined pressure. Then, either one or both of the upper fixed plate 110 and the lower fixed plate 109 perform a moving operation. As a result, the disk-shaped glass blank 107b and each fixed plate 109, 110 move relative to each other, and the two main surfaces 101e, 101f of the disk-shaped glass blank 107b are simultaneously ground by the fixed abrasive grains contained in the above-mentioned diamond sheet.

[0067] Note that instead of the fixed abrasive grains, free abrasive grains may be employed. In this case, the disk-shaped glass blank 107b can be ground in the same manner as in the case of the fixed abrasive grains using a grinding pad that replaces the above-mentioned diamond sheet and a grinding slurry containing free abrasive grains that replace the fixed abrasive grains.

[0068] Again, referring to FIG. 3. Polishing is performed on the two main surfaces of the disk-shaped glass blank (not shown), that is, the ground disk-shaped glass blank, after the grinding process (step S3) is performed (step S4). The polishing process (step S4) is performed for the purpose of removing scratches and distortions during grinding and mirror finishing.

[0069] The removal amount by the polishing process (step S4) is, for example, about 10 [μm] to 150 [μm], preferably 20 [μm] to 150 [μm]. The polishing process (step S4) is preferably performed in multiple stages as described later, whereby, for example, the disk-shaped glass substrate 100 described above with reference to FIGS. 1 and 2 may be produced.

[0070] In the polishing process (step S4), for example, polishing is simultaneously performed on the two main surfaces of the ground disk-shaped glass blank using a double-sided polishing apparatus.

[0071] The double-sided polishing apparatus may have a configuration generally similar to that of the above-described double-sided grinding apparatus 108, except that polishing pads are attached to the upper surface of the lower platen 109 and the lower surface of the upper platen 110 instead of diamond sheets. The polishing pad is a flat plate member having an overall annular shape, and is, for example, a resin polisher. Also, in the polishing step (step S4), a polishing slurry containing abrasive grains is used.

[0072] Although the double-sided polishing apparatus is not shown for simplicity, in the following description of the polishing step (step S4), reference numerals of the corresponding components in the double-sided grinding apparatus 108 shown in FIG. 7 are assigned to the components of the double-sided polishing apparatus used in this step (step S4).

[0073] The carrier 113 holds the ground disk-shaped glass substrate in the same manner as the above-described double-sided grinding apparatus 108. The carrier 113 holding the ground disk-shaped glass substrate is arranged such that the teeth of the carrier 113 mesh with the teeth between the internal gear 111 and the sun gear 112, respectively. The disk-shaped glass substrate held by the carrier 113 is clamped between the lower platen 109 and the upper platen 110 provided with polishing pads with a predetermined pressure. Then, while supplying the polishing slurry, either one or both of the upper platen 110 and the lower platen 109 move. As a result, the ground disk-shaped glass substrate and the platens 109, 110 move relative to each other, and the two main surfaces of the disk-shaped glass substrate are simultaneously polished by the free abrasive grains contained in the polishing slurry.

[0074] As shown in FIG. 3, the polishing step (step S4) according to the present embodiment includes a first polishing step (step S41) and a second polishing step (step S42).

[0075] The first polishing step (step S41) is mainly performed for the purpose of removing scratches and distortions remaining on the main surface after grinding, or adjusting minute irregularities (such as micro-waviness and roughness) on the main surface after grinding. In the first polishing step (step S41), polishing of the two main surfaces of the disk-shaped glass substrate after the grinding step (step S3) is performed using a double-sided polishing apparatus as described above. The removal amount by the first polishing step (step S41) is, for example, about 10 [μm] to 100 [μm].

[0076] In the first polishing step (step S41), for example, a polishing slurry containing cerium oxide abrasive grains or zirconia abrasive grains having a particle size of about 1 [μm] to 2 [μm] as free abrasive grains is used.

[0077] In addition, in the first polishing step (step S41), it is preferable to perform polishing in multiple stages by changing at least one of the polishing pad and the polishing slurry. That is, in this case, the combination of the polishing pad and the polishing slurry applied to the double-sided polishing apparatus may be different in each stage of the first polishing step (step S41). By performing the first polishing step (step S41) in multiple stages in this way, it becomes possible to adjust the parallelism of the disk-shaped glass substrate within the range of 0.05 [μm] to 0.95 [μm]. As a result, it becomes possible to obtain the disk-shaped glass substrate 100 having a high surface quality and a high-precision plate thickness.

[0078] The second polishing step (step S42) is mainly performed for the purpose of mirror-finishing the main surface and reducing roughness. In the second polishing step (step S42), polishing of the two main surfaces of the disk-shaped glass substrate after the first polishing step (step S41) is performed using a double-sided polishing apparatus as described above. The removal amount by the second polishing step (step S42) is, for example, about 1 [μm].

[0079] In the second polishing step (step S42), the type and particle size of the free abrasive grains contained in the polishing slurry and the hardness of the resin polisher are different from those in the first polishing step (step S41). In the second polishing step (step S42) according to the present embodiment, as the free abrasive grains, for example, fine particles having a particle size of about 10 [nm (nanometers)] to 50 [nm], such as colloidal silica turbidized in the slurry, are used.

[0080] Note that in the second polishing step (step S42), it is sufficient that at least one of the type and particle size of the free abrasive grains contained in the polishing slurry and the polishing pad is different from that in the first polishing step (step S41). That is, in the first polishing step (step S41) and the second polishing step (step S42), the combination of the hardness of the resin polisher applied to the double-sided polishing apparatus and the polishing slurry may be different from each other.

[0081] By performing the second polishing step (step S42), the roughness (root mean square roughness) Rq of the main surface can be made 0.4 [nm] or less. As a result, it becomes possible to produce the disk-shaped glass substrate 100 having a high surface quality, and by cutting out from the disk-shaped glass substrate 100, it becomes possible to produce a thin glass substrate having a high surface quality.

[0082] By performing grinding (step S3) and polishing (step S4) on each of the two main surfaces 101e and 101f of the disk-shaped glass blank 107b, a disk-shaped glass substrate 100 having a high-precision plate thickness as shown in FIG. 1 can be produced. The plate thickness t3 of the produced disk-shaped glass substrate 100 is, for example, 50 [μm] to 500 [μm], preferably 100 [μm] to 400 [μm], and more preferably 100 [μm] to 350 [μm] in a portion excluding the outer peripheral end face 102a and the chamfered faces 103a and 103b.

[0083] In addition, the disk-shaped glass substrate 100 to be manufactured may be a large one with a diameter of 70 to 210 [mm]. And the disk-shaped glass substrate 100 to be manufactured has a high surface quality with the parallelism of the two main surfaces 101a and 101b being less than 1.0 [μm], preferably 0.95 [μm] or less, and more preferably 0.5 [μm] or less. The parallelism of the two main surfaces 101a and 101b of the disk-shaped glass substrate 100 may be 0.05 [μm] or more.

[0084] In the grinding process (step S3) and the polishing process (step S4), at least a part of each of the chamfered surfaces 103c and 103d formed in the chamfering process (step S2) is used to grind and polish the main surface of the disk-shaped glass blank in place of the remaining range after the steps S3 to S4 are performed. Thereby, the chamfered surfaces 103a and 103b can be surely provided on the disk-shaped glass substrate 100 manufactured by polishing (step S4).

[0085] Also, when the plate thickness of the outer peripheral end face 102c of the chamfered disk-shaped glass blank 107b is t2 [mm], and the plate thickness other than the outer peripheral end face 102a and the chamfered surfaces 103a and 103b of the disk-shaped glass substrate 100 manufactured by polishing (step S4) is t3 [mm] (see FIG. 6), the following formula (2) is satisfied. t3 × 0.5 < t2 ····· formula (2)

[0086] Referring to FIG. 3 again. After the polishing process (step S4), the disk-shaped glass substrate 100 is cleaned using a neutral detergent, pure water, IPA (isopropyl alcohol), etc. Thereby, the disk-shaped glass substrate 100 shown in FIG. 1 is completed. Note that the shape and size of the disk-shaped glass substrate 100, such as the plate thickness of the disk-shaped glass substrate 100, generally do not change significantly before and after the cleaning process (step S5).

[0087] The manufacturing method of the disc-shaped glass substrate 100 according to the present embodiment includes a chamfering step (step S2). During the subsequent processing steps (steps S3 to S5) or before and after each of the processing steps (steps S3 to S5), breakage of the disc-shaped glass green sheet due to cracking or the like can be suppressed.

[0088] Also, since the grinding step (step S3) and the polishing step (step S4) are performed after the chamfering step (step S2) and the objects of grinding and polishing are disc-shaped, they do not include corners. As a result, the frictional forces applied to the main surfaces 101e and 101f of the disc-shaped glass green sheet 107b in steps S3 to S4 are likely to be uniform. As a result, the disc-shaped glass green sheet 107b can be processed thinly with high surface quality and high precision.

[0089] Furthermore, a disc-shaped glass substrate 100 having a high surface quality and a high-precision plate thickness as described above with reference to FIGS. 1 and 2 can be produced. That is, since the disc-shaped glass substrate 100 has a uniform plate thickness and a uniform and high surface quality, a thin glass substrate having a desired shape or size with a high surface quality and a high-precision plate thickness can be cut out.

[0090] Furthermore, by including the chamfering step (step S2), chamfered surfaces 103a and 103b are also formed on the produced disc-shaped glass substrate 100. As a result, the possibility of the disc-shaped glass substrate 100 being damaged when cutting out a thin glass substrate from the disc-shaped glass substrate 100 is reduced, and the thin glass substrate can be cut out with a higher yield than in the case where there are no chamfered surfaces 103a and 103b.

[0091] Therefore, it becomes possible to stably mass-produce a thin glass substrate having a desired shape with a high surface quality and a high-precision plate thickness.

[0092] Also, as described above, since the grinding process (step S3) and the polishing process (step S4) are performed after the chamfering process (step S2) and the object of grinding and polishing is disk-shaped, it does not include corners. Therefore, a disk-shaped glass substrate 100 with a large diameter of 70 to 210 mm, high surface quality, and high-precision plate thickness can be stably manufactured with a high yield. Usually, more thin plate glass substrates can be cut out from the large disk-shaped glass substrate 100 than from a small disk-shaped glass substrate 100. Therefore, by cutting out thin plate glass substrates from the large disk-shaped glass substrate 100, it becomes possible to more easily enable stable mass production of thin plate glass substrates having high surface quality and high-precision plate thickness.

[0093] (Method for manufacturing thin plate glass substrate 114) Hereinafter, the method for manufacturing the thin plate glass substrate 114 will be described.

[0094] The method for manufacturing the thin plate glass substrate 114 according to the present embodiment is a method for manufacturing a plurality of thin plate glass substrates 114 from a disk-shaped glass substrate 100 as an intermediate body, and includes, for example, the steps shown in the flowchart of FIG. 8.

[0095] In the method for manufacturing the thin plate glass substrate 114 according to the present embodiment, as shown in FIG. 8, after the steps S1 to S5 described above with reference to FIG. 3, a plurality of rectangular thin plate glass substrates 114 are cut out from the disk-shaped glass substrate 100 (step S6). In other words, the cutting process (step S6) is performed on the disk-shaped glass substrate 100 manufactured by the method for manufacturing the disk-shaped glass substrate 100.

[0096] Here, for simplicity in FIG. 8, the steps similar to steps S1 to S5 in the method for manufacturing the disk-shaped glass substrate 100 are omitted.

[0097] Specifically, in the cutting process (step S6), as shown in FIG. 9, the disk-shaped glass substrate 100 is cut along the straight line of the dotted line in the figure. As a result, a plurality of rectangular thin plate glass substrates 114 as shown in the enlarged view in FIG. 9 are cut out from the disk-shaped glass substrate 100.

[0098] According to the manufacturing method of the thin glass substrate 114, as described above, the disk-shaped glass substrate 100 having a uniform plate thickness and a uniform and high surface quality can be produced by the steps of steps S1 to S5. For such a disk-shaped glass substrate 100, a plurality of thin glass substrates 114 having a high surface quality and a high-precision plate thickness can be obtained regardless of the cutting location. Further, even for the thin glass substrate 114 having corners such as a rectangle, a thin glass substrate 114 having a high surface quality and a high-precision plate thickness can be obtained.

[0099] Further, by including the chamfering step (step S2), as described above, the possibility of the disk-shaped glass substrate 100 being damaged when cutting out the thin glass substrate 114 from the disk-shaped glass substrate 100 is reduced. Therefore, even for the thin glass substrate 114 having corners such as a rectangle as exemplified here, it can be obtained with a higher yield than when there are no chamfered surfaces 103a and 103b.

[0100] Therefore, it becomes possible to stably mass-produce a large number of thin glass substrates 114 having a high surface quality, a high-precision plate thickness, and corners.

[0101] In addition, in the cutting process (step S6), an example in which a plurality of rectangular thin glass substrates 114 are cut out has been described, but the number of thin glass substrates 114 cut out from the disk-shaped glass substrate 100 may be one. Further, in the cutting process (step S6), the shape and size of each of the one or more thin glass substrates 114 cut out from the disk-shaped glass substrate 100 may be appropriately changed, and for example, a shape without corners may be used. According to this, it becomes possible to stably mass-produce a large number of thin glass substrates 114 having a desired shape with a high surface quality and a high-precision plate thickness.

[0102] Note that the thin glass substrate 114 manufactured by the manufacturing method of the thin glass substrate 114 described herein may be used alone as a light guide plate. In this case, the manufacturing method of the thin glass substrate 114 described herein may be adopted as the manufacturing method of the light guide plate. According to this, it becomes possible to stably mass-produce a light guide plate having a desired shape with high surface quality and high-precision plate thickness.

[0103] (Manufacturing method of light guide plate) Hereinafter, the manufacturing method of the light guide plate 115 will be described.

[0104] The manufacturing method of the light guide plate 115 according to the present embodiment is a method for manufacturing the light guide plate 115 by combining a plurality of thin glass substrates 114, and includes, for example, the steps shown in the flowchart of FIG. 10.

[0105] In the manufacturing method of the light guide plate 115 according to the present embodiment, as shown in FIG. 10, after the cutting process (step S6) described above with reference to FIG. 8, the cut thin glass substrates 114 are laminated (step S7). In other words, the lamination step (step S7) is performed on the thin glass substrate 114 manufactured by the manufacturing method of the thin glass substrate 114.

[0106] Here, for simplicity in FIG. 10, the steps similar to steps S1 to S6 in the manufacturing method of the thin glass substrate 114 are omitted. That is, steps S1 to S5 in the manufacturing method of the light guide plate 115 may be the same as those in steps S1 to S5 in the manufacturing method of the disk-shaped glass substrate 100, respectively.

[0107] Specifically, in the lamination step (step S7), the thin glass substrates 114 are laminated in the vertical direction by fixing the thin glass substrates 114 adjacent to each other, thereby producing a light guide plate 115 as shown in FIG. 11.

[0108] Note that, in FIG. 11, an example in which four thin glass substrates 114 are laminated is shown, but the number of thin glass substrates 114 laminated in the lamination step (step S7) may be appropriately determined.

[0109] According to the manufacturing method of the light guide plate 115, a plurality of thin glass substrates 114 having high surface quality and high-precision plate thickness can be cut out and laminated to produce the light guide plate 115. As described above, it is possible to stably mass-produce a large number of thin glass substrates 114 having high surface quality, high-precision plate thickness, and corners. Therefore, it becomes possible to stably mass-produce a large number of light guide plates 115 having high surface quality, high-precision plate thickness, and corners.

[0110] In addition, the thin glass substrate 114 cut out from the disk-shaped glass substrate 100 in the cutting process (step S6) may have a desired shape and size as described above. According to this, it becomes possible to stably mass-produce a large number of light guide plates 115 having a desired shape and having high surface quality and high-precision plate thickness.

[0111] As described above, one embodiment and modification example of the present invention have been described, but the present invention is not limited thereto. For example, the present invention includes forms in which the embodiments and modification examples described so far are appropriately combined, and forms in which appropriate changes are made to such forms.

Industrial Applicability

[0112] The present invention can be used for mass production of thin glass substrates having high surface quality, such as glass substrates applied to display devices such as head-mounted displays.

Explanation of Reference Numerals

[0113] 100 Disk-shaped glass substrate 101a~101f Main surfaces 102a~102c Outer peripheral end faces 103a~103d Chamfered surfaces CS1, CS2 Cross sections 104a~104f Outer edge portions 105a~105b Upper end portions 106a~106b Lower end portions 107a~107b Disk-shaped glass blank 108 Double-sided grinding device 109 Lower platen 110 Upper platen 111 Internal gear 112 Sun gear 113 Carrier 114 Thin glass substrate 115 Light guide plate

Claims

1. A disk-shaped glass substrate for cutting one or more thin glass substrates, Two circular major surfaces; An outer peripheral end surface, a chamfered surface that forms a straight line when viewed from the side and connects each of the two main surfaces to the outer peripheral end surface; The refractive index is 1.60 or more, The straight chamfered surface is formed by chamfering the edge of a disk-shaped raw glass plate having a thickness greater than that of the disk-shaped glass substrate into a straight line, and then grinding and polishing the two main surfaces of the chamfered disk-shaped raw glass plate using a double-sided grinding device and a double-sided polishing device. A disk-shaped glass substrate comprising:

2. The distance between the two main surfaces is 50 to 500 μm.

2. The disk-shaped glass substrate according to claim 1.

3. The distance between the two main surfaces is 350 μm or less.

3. The disk-shaped glass substrate according to claim 1 or 2.

4. Parallelism is 0.5 μm or less 4. The disk-shaped glass substrate according to claim 1, wherein the glass substrate is a glass substrate having a thickness of 100 nm or less.

5. The root mean square roughness Rq of the two main surfaces is 0.4 nm or less.

5. The disk-shaped glass substrate according to claim 1, wherein the glass substrate is a glass substrate having a thickness of 100 nm or less.

6. When the plate thickness of the outer peripheral edge surface is t2 mm, and the plate thickness other than the outer peripheral edge surface and the chamfered surface is t3 mm, the disk-shaped glass substrate from which one or more thin glass substrates are cut satisfies t3×0.5<t2. The disk-shaped glass substrate according to any one of claims 1 to 5.

7. The thin glass substrate is used as a light guide plate either alone or in combination with a plurality of substrates.

7. The disk-shaped glass substrate according to claim 1, wherein the glass substrate is a glass substrate having a thickness of 100 nm or less.

8. The thin glass substrates are laminated and used as light guide plates.

8. The disk-shaped glass substrate according to claim 7.

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