CN110582376A

CN110582376A - apparatus and method for edge finishing of optically coupled glass

Info

Publication number: CN110582376A
Application number: CN201880028098.8A
Authority: CN
Inventors: 韩明宝; 金燦圭; G·N·库德瓦; 李沈平; S·N·沙夫瑞尔
Original assignee: Corning Inc
Current assignee: Corning Inc
Priority date: 2017-04-27
Filing date: 2018-04-27
Publication date: 2019-12-17
Also published as: WO2018200913A1; TW201843008A; JP2020517480A; US20210101245A1; KR20200002958A

Abstract

Methods and apparatus for finishing an edge of a glass sheet are described. The edge of the glass sheet is finished using two grinding wheels mounted on a mandrel so that the edge of the grinding wheels is beveled during relative movement of the grinding wheels and the glass sheet.

Description

Apparatus and method for edge finishing of optically coupled glass

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. provisional application serial No. 62/490869 filed 2017, 04/27/2017, based thereon and incorporated herein by reference in its entirety, in accordance with 35u.s.c. § 119.

Technical Field

Embodiments of the present disclosure relate to apparatus and methods for processing an edge of a glass sheet. In particular, embodiments of the present disclosure relate to apparatus and methods for processing an edge of a glass sheet to increase optical coupling through the glass sheet.

Background

In the manufacture of various products, such as Light Guide Plates (LGPs), which are used for backlights of edge-emitting Liquid Crystal Display (LCD) devices to uniformly partially reject light on a display panel, a glass sheet is finished by grinding and polishing the edge of the glass sheet. Edge-lit backlight units for such devices include an LGP, which is typically manufactured from a highly transmissive plastic material such as Polymethylmethacrylate (PMMA). Problems associated with the use of polymer Light Guide Plates (LGPs) have limited the trend toward thinner displays. While such plastic materials have excellent properties, such as light transmission, these materials have poor mechanical properties, such as stiffness, Coefficient of Thermal Expansion (CTE), and moisture absorption. In particular, polymeric LGPs lack the dimensional stability required for ultra-thin displays. When polymeric LGPs are subjected to heat and humidity, the LGPs warp and expand, compromising the opto-mechanical properties. The instability of polymer LGPs requires designers to add wider slopes and thicker backlights, with air gaps to compensate for this movement.

have provided for using glass sheetsAs an LGP alternative to the display, the glass sheet must have suitable properties to have adequate optical performance in transmission, scattering and optical coupling. The glass sheet for a light guide plate must meet edge specifications such as verticality, straightness, and flatness. Corning Iris is sold by Corning Incorporated^TMGlass is used as a substitute for PMMA and other transparent plastic materials used for LGP. Iris^TMThe glass is very transparent and has absorption or scattering losses as low as 0.2dB/m or less in the 450-650nm visible wavelength range for light propagating along the LGP and guided by total internal reflection. Furthermore, the CTE of glass is much lower than that of suitable plastics and closer to that of LCD display panels, which makes it much easier to integrate large-size flat panel TV sets. In addition, the excellent mechanical strength and stiffness and low CTE enable a significant reduction in bezel thickness of the LCD.

One of the main requirements of a light guide plate is the efficient light coupling of Light Emitting Diodes (LEDs) to the light guide plate. The reduced gap between the LED and the LGP edge facilitates coupling and also provides the maximum surface area on the edge through which the most light is coupled. This is different from conventional display glazing processes that focus on creating rounded edges, having a diffusive surface to withstand shock and brittle failure modes, and other transportation related modes. Accordingly, there is a need in the art for an apparatus and method that provides a glass light guide plate with increased light coupling efficiency.

disclosure of Invention

A first aspect of the present disclosure pertains to an apparatus for finishing an edge of a glass sheet by grinding the edge of the glass sheet. In one or more embodiments, such an apparatus includes a table that supports the glass sheet while the edge is subjected to grinding and polishing. The X-axis is the direction of lateral movement of the plane of the glass sheet on the stage. The Y-axis is the direction of longitudinal movement in a plane perpendicular to the X-axis. The Z-axis is the direction of vertical movement relative to the plane. The first motor is placed on a first side of the plane. The first motor has a first spindle with a first spindle axis of rotation substantially aligned along the X axis. The second motor is placed on a second side of the plane. The second motor has a second spindle with a second spindle axis of rotation substantially aligned along the X axis. A first grinding wheel is mounted on the first spindle. The first abrasive wheel is substantially disc-shaped having a peripheral edge, and the first edge of the glass sheet is beveled with the peripheral edge of the first abrasive wheel. A second grinding wheel is mounted on the second spindle. The second grinding wheel is substantially disc-shaped having a peripheral edge, and the second edge of the glass sheet is beveled with the peripheral edge of the second grinding wheel.

A second aspect of the present disclosure pertains to a method of finishing an edge of a glass sheet. The method includes supporting a glass sheet on a work table with a portion of the glass sheet extending a distance from the work table. The glass sheet includes a first surface, a second surface opposite the first surface, and an end surface. The first surface intersects the end surface along a first edge, and the second surface intersects the end surface along a second edge. The X-axis is the direction of lateral movement of the plane of the glass sheet on the surface. The Y-axis is the direction of longitudinal movement in a plane perpendicular to the X-axis. The Z-axis is the direction of movement perpendicular to the plane. The first edge contacts a peripheral edge of at least one substantially disc-shaped first grinding wheel disposed on a first spindle shaft of a first motor. The second edge is in contact with a peripheral edge of at least one substantially disc-shaped second grinding wheel disposed on a second spindle shaft of a second motor. Relative movement between the first and second grinding wheels and the glass sheet occurs during contact of the first and second grinding wheels with the first and second edges, respectively, thereby beveling the first and second edges.

drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several aspects described below.

FIG. 1A is a schematic view of a portion of a glass sheet according to one or more embodiments of the present disclosure;

FIGS. 1B and 1C are schematic illustrations of a portion of a glass sheet after edge processing according to one or more embodiments of the present disclosure;

FIG. 2 is a side view of an apparatus for finishing an edge of a glass sheet showing two grinding wheels positioned to grind the edge of the glass sheet according to one or more embodiments;

FIG. 3 is a top view of a glass sheet showing two grinding wheels positioned to treat an edge of the glass sheet according to one or more embodiments of the present disclosure;

FIG. 4 is a perspective view of an apparatus for finishing an edge of a glass sheet showing two grinding wheels positioned to process the edge of the glass sheet according to one or more embodiments;

FIG. 5 shows a side view of a grinding wheel on a mandrel according to one or more embodiments;

FIG. 6A shows a side view of a grinding wheel of an edge processing apparatus in a grinding position, according to one or more embodiments;

FIG. 6B shows a side view of an abrasive wheel of an edge processing apparatus in a position to change the abrasive wheel, according to one or more embodiments;

FIG. 7 is a partial side view of a glass sheet showing a grinding wheel grinding an edge of the glass sheet;

FIG. 8 is a cross-sectional view of a glass sheet including portions extending from a fixture and showing deflection that occurs when a force is applied to an end of the glass sheet;

FIG. 9 shows a schematic view of an edge finishing apparatus according to a portion of one or more embodiments of the present disclosure;

FIG. 10 shows a schematic view of an edge finishing apparatus according to a portion of one or more embodiments of the present disclosure;

FIG. 11 shows a schematic view of an edge finishing apparatus according to a portion of one or more embodiments of the present disclosure;

FIG. 12 shows a schematic view of an edge finishing apparatus according to one or more embodiments of the present disclosure;

FIG. 13 is a partial perspective view of a grinding wheel having a cooling system according to one or more embodiments;

FIG. 14 shows an exemplary embodiment of a light guide plate; and

Fig. 15 shows the total internal reflection of light at two adjacent edges of a glass light guide plate.

Detailed Description

Reference will now be made in detail to the various embodiments, examples of which are illustrated in the accompanying examples and drawings.

In the description below, like reference numerals designate similar or corresponding parts throughout the several views shown in the drawings. It should also be understood that, unless otherwise specified, terms such as "top," "bottom," "outward," "inward," and the like are words of convenience and are not to be construed as limiting terms. Further, whenever a group is described as comprising at least one of a group of elements and combinations thereof, it is understood that the group may comprise, consist essentially of, or consist of any number of those elements recited, either individually or in combination with each other. Similarly, whenever a group is described as consisting of at least one of a group of elements or a combination thereof, it is understood that the group may consist of any number of those listed elements, either individually or in combination with each other. Unless otherwise indicated, a range of numerical values set forth includes both the upper and lower limits of the range, as well as any range between the stated ranges. As used herein, the indefinite article "a" or "an" and its corresponding definite article "the" mean "at least one", or "one or more", unless otherwise indicated. It should also be understood that the various features disclosed in the specification and drawings may be used in any and all combinations.

Methods and apparatus for finishing an edge of a glass sheet are described herein. In particular embodiments the grooves are finished by grinding and polishing the glass sheet, thereby providing a light guide plate that can be used in a backlight unit according to embodiments of the present disclosure. In particular embodiments, light guide plates are provided that have similar or superior optical properties to light guide plates made from PMMA, and that have much better mechanical properties, such as stiffness, Coefficient of Thermal Expansion (CTE), and dimensional stability under high moisture conditions, than PMMA light guide plates.

Some embodiments of the present disclosure provide methods and apparatus to produce minimized bevels on a glass light guide plate to achieve maximized light coupling efficiency. Embodiments of the present disclosure may provide LGPs that may be used for thinner glass LEDs. For example, a 1.5 millimeter (mm) LED may use a 2mm thick LGP, but a 1.0mm LED uses a 1.1mm thick LGP. Therefore, the optimal coupling efficiency of thinner LEDs requires minimal slope on the LGP. In addition, the chamfer eliminates cantilever curl generated during separation and enhances edge reliability by reducing the likelihood of failure due to sharp features. Cantilever curling occurs when the top or bottom surface of the glass extends partially beyond the edge surface so that a localized area of the top or bottom surface is not perpendicular to the edge surface. Cantilever rolling can lead to brittle chips and cleavage, and areas with cantilever rolling are more prone to damage upon impact.

studies have shown that as the bevel thickness increases from 50 to 200 microns (micrometers, μm), the coupling efficiency decreases by about 5%. Normalizing the bevel height relative to the thickness shows that the coupling efficiency remains consistent across the thickness. However, as glass becomes thinner and thinner, and the LED thickness equals the glass thickness, the coupling efficiency is more sensitive to the LED-to-LGP gap for a given bevel height/thickness ratio.

Thin glass sheets provided to device manufacturers (e.g., electronic display manufacturers) typically include a machined edge. That is, the edges are ground and shaped (e.g., beveled) to eliminate sharp edges and edge flaws (chips, cracks, etc.) that are prone to damage that may reduce the strength of the glass as a result of the cutting process. Such sheets typically have a thickness between the opposite major surfaces of the sheet of equal to or less than about 2mm, and more preferably equal to or less than about 0.7mm, and in some applications equal to or less than about 0.5 mm. Very thin glass sheets may be equal to or less than 0.3mm and still provide the benefits of the present disclosure.

It is known that breakage of glass can be traced back to an initial flaw (e.g., a small crack) and that the breakage extends from such an initial flaw. Cracking can occur over a very short period of time or, depending on the stresses present in the article, can occur gradually over an extended period of time. However, each break begins with a flaw, which is most commonly found along the edge of the glass sheet, and most particularly the edge that was previously scored and cut. To eliminate edge flaws, the sheet edge can be ground and polished to leave only minimal flaws, thereby increasing sheet strength by increasing the stress required for flaw propagation.

In addition, the grinding process itself is rarely uniform, as the grinding wheel may have some drift or variation in its position as it crosses the glass edge. That is, the grinding wheel may move closer to or further away from the glass sheet, so that the force exerted by the grinding wheel against the sheet material may vary simultaneously as a function of time and/or position. Such positional variations may result in variations in the amount of material removed from the edge. This variation can lead to uneven grinding and variation in the amount of particles produced. More simply, the bevel width may vary, and this variation is most severe if the sheet edge undergoing grinding is rigid.

Referring to fig. 1A through 1C, exemplary end portions of glass sheet 30 are shown before and after edge finishing. Fig. 1A shows glass sheet 30 prior to edge finishing. Glass sheet 30 includes a first surface 31, a second surface 32 opposite first surface 31, and an end surface 33. First surface 31 intersects end surface 33 along first edge 43, and second surface 32 intersects end surface 33 along edge 44. Fig. 1B and 1C show glass sheet 30 after edge finishing. Here, the edges 43, 44 are beveled, providing a first bevel 41 and a second bevel 42. First surface 31 intersects first ramp 41 at edge 46, end surface 33 intersects first ramp 41 at edge 47, end surface 33 intersects second ramp 42 at edge 48, and second ramp 42 intersects second surface 32 at edge 49. Total thickness T of glass sheet 30_gThickness T including first slope 41_C1Thickness T of end surface 33_eAnd the thickness T of the second slope 42_C2And (4) summing.

Thickness T of first bevel 41 of some embodiments_C1And the thickness T of the second inclined surface 42_C2The sum is less than the total thickness T of the glass sheet 30_gAbout 10% of the total. In some embodiments, the ramp 41,42 thickness T_C1And T_C2The sum is less than the total thickness T of the glass sheet 30_gAbout 5% of the total. In some embodiments, the average thickness T of the inclined surfaces 41, 42_C1And T_C2the sum is less than the total thickness T of the glass sheet 30_gabout 4%, 3%, 2.5%, 2%, 1.5% or 1%. In some embodiments, the inclined plane averages 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, or 90 μm. In some embodiments, the average thickness of the bevel is in the range: about 20 to about 80 μm, alternatively about 20 to about 50 μm, alternatively about 40 to about 80 μm.

the amount of particles generated during grinding of the first bevel 41 and the second bevel 42 (respectively characterized by bevel width W)_C1And W_C2) Should be minimized. The bevel width is defined as the length of the bevel surface from the edge surface 33 of the glass sheet 30 to the first surface 31 or the second surface 32, depending on which bevel is measured.

Once the bevel has been created on the glass sheet, the resulting additional edges 46, 47, 48, 49 may be polished to eliminate sharp angles at these edges and to form arcuate edges. This can be accomplished, for example, by a buffing wheel and a suitable abrasive paste.

shown in fig. 2-4 is an embodiment of an apparatus 100 for processing a thin glass sheet 30. Fig. 2 shows a side view, fig. 3 shows a top view, and fig. 4 shows a perspective view of a similar apparatus 100. The apparatus 100 includes a table 116, which may also be referred to as a support surface. The X-axis is the direction in which the table 116 and/or grinding wheel moves laterally during edge machining. The Y-axis is the direction of longitudinal movement perpendicular to the X-axis. The plane of the table 116 lies in the X-Y plane formed by the X-axis and the Y-axis. The Z-axis is perpendicular relative to the plane of the table 116. The illustrated embodiment provides a table 116 that supports glass sheet 30 in a horizontal manner in the X-Y plane, although alternative configurations are possible. In some embodiments, the platen 116 supports the glass sheet 30 in a vertical orientation and moves up or down.

The apparatus 100 includes a first motor 120 having a first spindle 121. First mandrel 121 is oriented such that rotational axis 122 is substantially aligned along the X-axis. The first mandrel 121 is placed on a first side of the plane of the table 116. The second motor 130 includes a second spindle 131 oriented such that the axis of rotation 132 is substantially aligned along the X-axis. The second mandrel 131 is placed on the second side of the plane of the table 116. The second side of the plane of the table 116 is opposite the first side of the plane of the table 116. For example, if the plane of the table 116 is oriented horizontally, the first mandrel 121 may be located above the plane and the second mandrel 131 may be located below the plane. As used in this manner, the term "substantially along the X-axis" means that the axis of rotation is within 20, 10, 5, 4, 3, 2, or 1 of the X-axis.

The apparatus 100 includes a support 110 (shown in fig. 4) that can hold and/or move a first motor 120 and/or a second motor 130. The support 110 may allow the motors to move independently or together. In some embodiments, the first motor 120 is located on the first support 110a and the second motor 130 is located on the second support 110B, as shown in fig. 6A and 6B. The support 110 can include a Z-axis motor (not shown) such that the first motor 120 or the second motor 130 moves in a direction perpendicular to the major plane formed by the glass sheet 30.

The first grinding wheel 125 is connected to the first spindle 121 and rotates about the rotation shaft 122 of the spindle 121. The grinding wheel may be attached to the spindle by any suitable assembly as understood by those skilled in the art. The second grinding wheel 135 is connected to the second spindle 131 and rotates about the rotation shaft 132 of the spindle 131. The grinding wheel may be mounted at the end of the mandrel or along the length of the mandrel.

the first grinding wheel 125 and the second grinding wheel 135 may be the same type of grinding wheel or may be different. In some embodiments, the first abrasive wheel 125 and the second abrasive wheel 135 are flexible urethane-based wheels. Urethane-based wheels have abrasive elements held together in a cross-linked urethane binder (e.g., industrial diamond held in a polyurethane matrix). In some embodiments, the urethane-based wheel has a shore a scale hardness (astm d2240) of about 80 to about 104, or about 84 to about 98. An exemplary grinding wheel 125 is shown in fig. 5. The grinding wheel 125 may be a substantially disc-shaped component having an inner face 126, an outer face 127, and a peripheral edge 128. As used in this manner, the term "substantially disc-shaped" means that the grinding wheel has the appearance of a generally disc-shaped or drum-shaped assembly having at least one face and a peripheral edge. The term inner face 126 refers to the face of the wheel 125 that is closer to the motor. Peripheral edge 128 provides an abrasive surface that contacts glass sheet 30 during the beveling process. The grinding wheel is aligned for rotation about the X-axis and the peripheral edge 128 is used to bevel the edge of the glass sheet 30. In some embodiments, the grinding wheels use a circular wheel rim that includes a recessed central region, often referred to as a "cup" wheel based on the cup-like shape of the grinding wheel.

Typically, the abrasive surface of the peripheral edge 128 includes diamond particles as cutting media dispersed in a suitable matrix or binder (e.g., a resin or metal bond matrix). Other cutting media, such as carbide particles, may also be used. The average particle size of the abrasive material of the abrasive wheel of some embodiments is in the following range: from about 200 μm to about 3 μm, alternatively from about 150 μm to about 4 μm, alternatively from about 120 μm to about 5 μm, alternatively from about 100 μm to about 6 μm, alternatively from about 60 μm to about 7 μm, alternatively from about 50 μm to about 8 μm, alternatively from about 25 μm to about 10 μm. In some embodiments, the grit of the grinding wheel is from about P120 to about P6000, or from about P180 to about P3000, or from about P240 to about P2500, or from about P360 to about P2000, or from about P600 to about P1500, or from about P800 to about P1200, on the FEPA scale.

referring again to fig. 2, glass sheet 30 is supported by table 116 such that a portion 26 of glass sheet 30 extends beyond table 116. For example, glass sheet 30 can be placed in a horizontal arrangement (as shown), wherein glass sheet 30 can be said to be suspended from a table 116 (also referred to as a support element or support surface). However, glass sheet 30 may be held in any orientation at any angle. For example, glass sheet 30 may be supported in a vertical orientation. Apparatus 100 can also include a clamp element 117 that includes a rail, finger, hook, or other suitable clamp element to secure glass sheet 30 to table 116. Another method of securing the sheet is by including a vacuum cup in the table 116, which holds the glass sheet stationary. The vacuum may be used alone or may be used in conjunction with one or more of the gripper elements. Generally, any suitable method may be used to secure glass sheet 30 to work table 116 so long as one portion 26 of glass sheet 30 is positioned to extend from the securing device. In some embodiments, extension 26 is able to flex relative to the fixture while glass sheet 30 is securely attached. Glass sheet 30 may be secured to the fixture such that extension 26 extends a predetermined distance L from the fixture.

Referring to fig. 7, the grinding wheels 125, 135 contact the glass sheet 30, thereby beveling the edges. The rounded portion of the grinding wheel may leave a slightly rounded bevel corresponding to the shape of the grinding wheel. However, the amount of contact of the glass sheet 30 with the grinding wheel is small enough so that the bevel appears flat, or sufficient heat from friction to flatten the freshly beveled edge. The embodiment shown in fig. 7 is exaggerated to show the angle of the bevel (measured based on the edge of the bevel) relative to the end surface 33. The first grinding wheel 125 can form a first bevel 41 having a first angle α with respect to the end surface 33. The second grinding wheel 135 is positioned such that the grinding surface of the second grinding wheel forms a second angle beta with respect to the end surface 33. The first and second angles alpha, beta may be substantially the same or different angles.

Referring to fig. 2, showing an embodiment of the apparatus and method for removing glass sheet 30 from the plane of the page, and to fig. 7, first grinding wheel 125 rotates about shaft 122 and acts on first surface 31 with force F1. This force F1 in turn can produce a deflection δ 1 in glass sheet 30. That is, glass sheet 30 bends in response to the applied force. This can be seen generally with the aid of fig. 8, which shows the force F applied to glass sheet 30, causing a response in the form of deflection δ. The amount of bending or compliance (magnitude of δ) is related to many variables, including the material properties of the glass (e.g., young's modulus), the amount of protrusion from the fixture, and the magnitude of the applied force. These variables may be combined and characterized by a stiffness value k, where stiffness is equal to the applied force at the magnitude of the resulting deflection. The stiffness k can be roughly expressed as:

In the formula, the force F divided by the deflection δ is also proportional to the following parameters: the modulus of elasticity E of the glass sheet is multiplied by the moment of inertia I and divided by the third power of the amount L by which the glass sheet extends beyond the fixture.

It can also be shown that the amount of material removed by the grinding wheel is proportional to the applied force. As can be seen from the above equation, the stiffness is infinite for a sheet material that is fully supported by a rigid support (no extensions and no deflection in the plane of the glass sheet under the applied force). In such a case, an increase in force (e.g., the force applied to the glass sheet by the grinding wheel) would result in a commensurate increase in the amount of material removed, and thus an increase in the width of the bevel. Such systems become undesirably sensitive to small changes in the position of the grinding wheels that are often observed in real life systems. This sensitivity can be as high as 1:1, where doubling the applied force results in doubling the removed material.

on the other hand, the above relationship also implies that if a portion of the sheet extends beyond the fixture (e.g., beyond the table 116), the stiffness of the extended portion is reduced and limited, and the sheet may flex. For low finite stiffness, this flexibility results in a reduced ramp width. In other words, skewing due to small positional changes of the contact of the grinding wheel with the (flexible exhibiting) sheet material having low stiffness may avoid a large increase in material removal compared to the same positional movement relative to the rigid sheet material (e.g. high stiffness). Furthermore, the level of precision of the beveling apparatus need not be as high as possible if the glass sheet does not exhibit flexibility. This may reduce equipment costs, as bearing accuracy may be reduced, for example.

Those skilled in the art will appreciate that the second grinding wheel 130 will exhibit a similar situation setting. That is, consider second grinding wheel 28b in contact with second edge 44 and applying force F2. However, since F2 is applied in the opposite direction to F1, the displacement of the extended portion of glass sheet 30 occurs in the opposite direction to the deflection produced by first grinding wheel 120.

According to embodiments of the present disclosure, a plurality of grinding wheels are used to create a bevel or a bevel on both edges of an end of a glass sheet restrained by a fixture, wherein the glass sheet includes a portion that extends beyond the fixture. At least two grinding wheels are disposed and arranged such that each of the at least two grinding wheels respectively engages an end of the glass sheet on opposite sides of the glass sheet. Each wheel rotates about a shaft and moves relative to each other along the end of the glass sheet to form two ramps along the end of the glass sheet.

For example, along the first edge 43 of the glass sheet 30, a bevel 41 is formed by the first grinding wheel 120. In some embodiments, the angle α of the chamfer with respect to the plane of the end surface 33 is in the range: from about 20 to about 75 degrees, alternatively from about 30 to about 70 degrees, alternatively from about 40 to about 65 degrees, alternatively from about 45 to about 65 degrees, alternatively from about 50 to about 65 degrees, alternatively about 60 degrees. Similarly, the second grinding wheel 130 creates a second bevel 42 at the second edge 44. In some embodiments, the ramp angle β is in the range: from about 20 to about 75 degrees, alternatively from about 30 to about 70 degrees, alternatively from about 40 to about 65 degrees, alternatively from about 45 to about 65 degrees, alternatively from about 50 to about 65 degrees, alternatively about 60 degrees.

To isolate the influence of the grinding wheels 120, 130, the grinding wheels 120, 130 are placed a predetermined distance D apart_eAs shown in fig. 9. The magnitude of this predetermined distance is selected so that the force applied to glass sheet 30 by one wheel does not affect the action of the other wheels. That is, the deflection produced by one cup wheel relative to the plane of the glass sheet does not cause deflection of the glass sheet in the area of influence of the other cup wheels. Perhaps more simply, the deflection relative to the plane of the glass sheet produced by one grinding wheel does not overlap the deflection produced by the other grinding wheel. In some embodiments, the adjacent faces of the grinding wheel are spaced at least about 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, or 10mm apart.

Referring again to fig. 6A and 6B, the first motor 120 and/or the second motor 130 may be movable in the Z-axis such that the motors, spindles, and attached grinding wheels move toward or away from each other and toward or away from the table. The Z-axis movement enables the grinding wheels 125, 135 to be replaced and a controlled amount of force applied to the glass sheet 30. In some embodiments, the first motor 120 and/or the second motor 130 may be movable in the Z-axis at a distance from the stage equal to or greater than about 30mm, 40mm, 50mm, 60mm, 70mm, or 80 mm. Fig. 6A shows the first motor 120 mounted on a support 110a separate from the support 110b of the second motor 130. The motors 120, 130 are in a processing position in which the glass sheet passing over the grinding wheels 125, 135 is edge treated. Fig. 6B shows the apparatus with motors 120, 130, spindles 121, 131, and grinding wheels 125, 135 moving in the Z-axis away from the machining position.

The first motor 120 and the second motor 130 may be configured to operate at any suitable speed. In some embodiments, the motor is configured to operate in the following speed ranges: from about 600rpm to about 3000rpm, alternatively from about 800rpm to about 2500rpm, alternatively from about 1000rpm to about 2400rpm, alternatively from about 1500rpm to about 2200 rpm.

Referring to fig. 9, first mandrel 121 is spaced a distance D from second mandrel 131_aSufficient to prevent the first grinding wheel 125 from contacting the second spindle 131 or the second grinding wheel 135 from contacting the first spindle 121. In some embodiments, the first spindle 121 is spaced from the second spindle 131 by an amount greater than or equal to the radius r of the first grinding wheel 125₁Or radius r of the second grinding wheel 135₂The larger of which adds a safety margin. In some embodiments, the safety margin is equal to or greater than about 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, 14mm, or 15 mm. In addition, the distance D between the thickness midpoints of the grinding wheels_cSufficient to prevent contact between adjacent faces of the grinding wheel.

the dimensions of the individual grinding wheels may vary. In some embodiments, the radius of the grinding wheel is about 25mm to about 250mm, or about 50mm to about 200mm, or about 75mm to about 150mm, or about 100mm, or about 150mm, or about 200 mm.

Fig. 9 shows an embodiment with a single grinding wheel 125, 135 per spindle 121, 131. Mandrels 121, 131 are shown having approximately the same length; it will be appreciated that the length of the mandrels 121, 131 may be different and the position of the grinding wheels 125, 135 on the mandrels 121, 131 may be controlled to prevent contact between the grinding wheels.

In some embodiments, first mandrel 121 and/or second mandrel 131 further comprise additional grinding wheels. Fig. 10 shows an embodiment where the first spindle 121 has a single grinding wheel 125 and the second spindle 131 has two grinding wheels 135a, 135 b. The grinding wheels 135a, 135b are spaced apart along the length of the second mandrel 131 such that the grinding wheel 125 on the first mandrel 121 is located between the grinding wheels 135a, 135 b. Fig. 11 shows another embodiment in which the first spindle 121 has two grinding wheels 125a, 125b and the second spindle 131 has two grinding wheels 135a, 135 b. The grinding wheels 125a, 125b are spaced apart along the length of the first mandrel 121 and the grinding wheels 135a, 135b are spaced apart along the length of the second mandrel 131 such that the grinding wheels on the mandrels are alternating such that at least one of the grinding wheels 125a, 125b is located between the grinding wheels 135a, 135b and at least one of the grinding wheels 135a, 135b is located between the grinding wheels 125a, 125 b.

The width of the grinding wheel can be varied to provide sufficient contact length with the glass sheet. In the embodiment of FIG. 9, the width W of the grinding wheel 125_W1And width W of grinding wheel 135_W2Greater than or equal to about 25mm, 28mm, 30mm, 35mm, 40mm, 45mm, or 50mm, respectively. In the embodiment of FIG. 10, the width W of the grinding wheel 125_W1Greater than or equal to about 25mm, 28mm, 30mm, 35mm, 40mm, 45mm, or 50mm, respectively, the width W of the grinding wheel 135a_W2aWidth W of grinding wheel 135b_W2bGreater than or equal to about 25mm, 28mm, 30mm, 35mm, 40mm, 45mm, or 50 mm. A wheel with a greater contact length will use less force per unit area than an otherwise identical wheel with a smaller contact length.

Fig. 12 shows a schematic diagram of an apparatus 100 according to one or more embodiments of the present disclosure. The grinding wheel 125 is connected to the first spindle 121 and the first motor 120, and the grinding wheel 135 is connected to the second spindle 131 and the second motor 130. First motor 120 and second motor 130 are each connected to controller 145 using first force transducer 147 and second force transducer 148, respectively. A force transducer is an assembly that converts force into an electrical signal. For example, an exemplary force has an electrical output of 4 to 20mA, which is equivalent to a force range of 0 to 100N matching the transducer range. The force transducers 147, 148 may be any suitable force transducers capable of measuring a force within a predetermined range. The force transducers of some embodiments are operatively connected to the air bearings to provide a controlled amount of force to the motors 120, 130 to produce a controlled amount of force per unit area on the glass sheet 30 by the grinding wheels 125, 135. In use, the force transducer measures the force of the grinding wheel on the glass, and the feedback loop can adjust the air bearing (or other force transfer system) to apply the desired force. In other words, the first motor 120 and the second motor 130 are pushed toward the surface of the table 116, such that the force transducer pushes the motors downward if the motors are above the surface of the table. The force transducer in combination with the feedback system provided by the controller 145 can compensate for the flexibility of a single abrasive wheel so that abrasive wheels having different core materials can be used. Controller 145 may be any suitable controller, microcontroller, or computer, and may include, for example: a circuit, a central processing unit, a display unit and/or an input/output unit. In some embodiments, the force transducer is configured to maintain a pressure of the grinding wheel against the glass of about 10N, 20N, 30N, 40N, or 50N, or about 5 newtons to about 75 newtons, or about 10 newtons to about 50 newtons.

The platen 116, or a suitable assembly connected to the platen, can be configured to move the glass sheet 30 across the grinding wheel at any suitable speed. The term "across the grinding wheel" as used in this manner does not imply a direction or physical orientation of the assembly. Rather, the term is used to refer to the relative movement of the grinding wheel with respect to the glass sheet such that the edge of the glass sheet becomes beveled by the grinding wheel. The platen 116 can be configured to move the glass sheet at a rate of greater than or equal to about 5 m/min, 10 m/min, 15 m/min, 20 m/min, 25 m/min, or 30 m/min. In some embodiments, the platen 116 is configured to move the glass sheet at a rate of about 5 m/min to about 30 m/min.

Fig. 13 shows an embodiment of the apparatus 100 that includes a cooling system 170 to prevent overheating of the glass sheet 30 or the grinding wheels. The first motor 120, first spindle 121, and grinding wheel 125 are shown, but it will be appreciated that there may be two motors, spindles, or multiple grinding wheels. A single cooling system 170 may be used to cool multiple motors, spindles, and/or grinding wheels, or each motor, spindle, and/or grinding wheel may have a separate cooling system. The cooling system 170 may include a plurality of first perimeter liquid cooling nozzles 171 adjacent the first mandrel 121. The plurality of first perimeter liquid cooling nozzles 171 can be aligned or positioned to direct cooling liquid toward the perimeter edge 128 of the grinding wheel 125 and/or toward the glass sheet. In some embodiments, apparatus 100 includes a plurality of second peripheral liquid cooling nozzles adjacent to the second mandrel and positioned to direct cooling liquid toward the peripheral edge of the second grinding wheel and/or toward the edge of the glass sheet. The plurality of first perimeter liquid cooling nozzles and the plurality of second perimeter cooling nozzles may share a single cooling system 170, or they may each have separate independent cooling systems.

in one or more embodiments, the cooling nozzles are disposed at a range of distances from the edge of the glass sheet and/or the peripheral edge 128 of the grinding wheel 125 as follows: from about 10cm to about 200cm, alternatively from about 40cm to about 200cm, alternatively from about 80cm to about 200cm, alternatively from about 100cm to about 200cm, alternatively from about 150cm to about 200 cm. The cooling liquid may be flowed through liquid coolant lines 172 to the distal liquid cooling nozzles 171. The cooling system 170 may be fed through a supply line (not shown) which may be connected to a coolant source (not shown), such as a tap for supplying tap water or a pump connected to a tank (not shown) containing deionized and/or demineralized water.

In one or more embodiments, the cooling system 170 is configured to be activated during the beveling of the glass sheet. The plurality of perimeter liquid cooling nozzles may comprise any suitable number of nozzles to provide sufficient cooling during the grinding and/or polishing process. The embodiment shown in fig. 13 has two nozzles 171, but those skilled in the art will appreciate that more or fewer nozzles may be used. For example, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 perimeter liquid cooling nozzles may be provided. Similarly, the plurality of second perimeter liquid cooling nozzles can comprise any suitable number of nozzles to provide sufficient cooling during the milling process.

during the beveling process, the distal liquid-cooling nozzles 171 can be spaced any suitable distance from the edge of the glass sheet 30 or the peripheral edge 128 of the grinding wheel 125. During operation, the distal liquid cooling nozzle 171 can be spaced from the edge of the glass sheet or the peripheral edge 128 of the grinding wheel 125 by a distance as follows: 5cm, 10cm, 15cm, 20cm, 25cm, 30cm, 35cm, 40cm, 50, cm, 60cm, 70cm, 80cm, 90cm, 100cm, 125cm, 150cm, 200cm or up to 500 cm. Each cooling nozzle 171 may be sized and shaped as desired to achieve the desired cooling effect. For example, the diameter of the opening of the cooling nozzle 171 may be 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.8mm, 0.9mm, 1mm, 2mm, 3mm, 4mm, 5mm, or to 10 mm. For each of the coolant lines 172 and supply lines, conventional polyvinyl chloride (PVC) or other suitable plastic or metal pipes may be used. The cooling liquid may comprise water, chilled water, or other cooling liquid.

As described above, the apparatus and methods described herein may be used to manufacture glass light guide plates. Fig. 14 shows an exemplary embodiment of a light guide plate 200 that can be fabricated by edge grinding and polishing a finished glass sheet by the methods and apparatus of the present disclosure. The glass sheet has the shape and structure of a typical light guide plate, which includes a glass sheet having a first face 210 (which may be a front face) and a second face opposite the first face (which may be a back face). The first and second faces may have a height H and a width W. In one or more embodiments, the first and/or second faces have an average roughness (Ra) of less than 0.6 μm, 0.4 μm, or 0.2 μm, as measured by a 3D optical profiler or surface topography device.

Glass sheet 200 has a thickness T between the front and back sides, wherein the thickness forms 4 edges. The thickness of the glass sheet is generally less than the height and width of the front and back surfaces. In various embodiments, the light guide plate has a thickness that is less than 1.5% of the height of the front and/or back faces. In one or more embodiments, the thickness T may be about 2mm, about 1.9mm, about 1.8mm, about 1.7mm, about 1.6mm, about 1.5mm, about 1.4mm, about 1.3mm, about 1.2mm, about 1.1mm, about 1mm, about 0.9mm, about 0.8mm, about 0.7mm, about 0.6mm, about 0.5mm, about 0.4mm, or about 0.3 mm. In some embodiments, the thickness T of the light guide plate is: from about 0.1mm to about 2.5mm, alternatively from about 0.2mm to about 2mm, alternatively from about 0.3mm to about 1.5 mm. The height, width, and thickness of the light guide plate of some embodiments are configured and dimensioned for use as an LGP in LCD backlight applications.

In the illustrated embodiment, the first edge 230 is a light injection edge that receives light provided by, for example, one or more Light Emitting Diodes (LEDs). In some embodiments, in transmission, the light injection edge scatters light within an angle of less than 12.8 degrees of full width at half maximum (FWHM). The light injection edge may be obtained by grinding and polishing the first edge 230 according to the apparatus and methods described herein.

The glass sheet further includes a second edge 240 adjacent the first edge 230 (light injection edge) and a third edge opposite the second edge 240 and adjacent the light injection edge 230, wherein in reflection, the second edge 240 and/or the third edge 260 scatter light within an angle of less than 12.8 degrees of full width at half maximum FWHM. The second edge 240 and/or the third edge 260 may include a spread angle in reflection of less than 6.4 degrees. The glass sheet includes a fourth edge 250 opposite the first edge 230.

According to one or more embodiments, 3 of the 4 edges of the LGP have mirror-image polished surfaces for at least two reasons: LED coupling and Total Internal Reflection (TIR) at both edges. In accordance with one or more embodiments, and as shown in fig. 15, light injected into the first edge 230 may be incident on a second edge 240 adjacent to the injection edge and a third edge 260 adjacent to the injection edge, wherein the second edge 240 is opposite the third edge 260. The second and third edges may also include a low average roughness Ra at the edges, less than 0.5, 0.4, 0.3, or 0.2 microns (as measured by optical profilometry) without etching with hydrofluoric acid and/or slurry polishing the edges, such that incident light undergoes total internal reflection from both edges adjacent to the first edge.

Light may be injected into the first edge 230 from an array 300 of LEDs arranged along the first edge 230. The LED may be positioned less than 0.5mm from the first edge 230. According to one or more embodiments, the thickness or height of the LEDs may be less than or equal to the thickness of the glass sheet to provide efficient light coupling with the light guide plate 200. According to one or more embodiments, the two edges 240, 260 may also include a spread angle in reflection of less than 6.4 degrees.

Various modifications and variations may be made in the materials, methods, and articles described herein. Other aspects of the materials, methods, and articles described herein will be apparent from consideration of the specification and practice of the materials, methods, and articles disclosed herein. The specification and examples should be considered as exemplary. It will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure without departing from the spirit and scope of the disclosure.

Claims

1. An apparatus for finishing an edge of a glass sheet, the apparatus comprising:

A table supporting the glass sheet when the edge is subjected to grinding and polishing, wherein an X-axis is a lateral movement direction on a plane of the glass sheet on the table, a Y-axis is a longitudinal movement direction on a plane perpendicular to the X-axis, and a Z-axis is a vertical movement direction with respect to the plane;

A first motor having a first spindle with a first spindle axis disposed on a first side of a plane, the axis of the first spindle being substantially aligned along an X axis;

A second motor having a second spindle with a second spindle axis disposed on a second side of the plane, the axis of the second spindle being substantially aligned along the X axis;

A first grinding wheel mounted on the first mandrel, the first grinding wheel being substantially disc-shaped having a peripheral edge, the first edge of the glass sheet being beveled with the peripheral edge of the first grinding wheel; and

A second grinding wheel mounted on the second mandrel, the second grinding wheel being substantially disc-shaped having a peripheral edge, the peripheral edge of the second grinding wheel being used to bevel the second edge of the glass sheet.

2. The apparatus of claim 1, wherein one or more of the first mandrel or the second mandrel further comprises an additional grinding wheel.

3. The apparatus of any of claims 1-2, wherein the first mandrel and the second mandrel are configured to produce a bevel that is less than or equal to about 5% of the thickness of the glass sheet.

4. The apparatus of any one of claims 1-3, wherein the first grinding wheel and the second grinding wheel each independently have an average particle size range of about 200 μm to about 3 μm.

5. The apparatus of any one of claims 1-4, wherein the first and second grinding wheels are flexible urethane-based wheels.

6. The apparatus of any one of claims 1-5, wherein the first mandrel is spaced from the second mandrel by greater than or equal to the radius of the first or second grinding wheel plus 10 mm.

7. the apparatus of any one of claims 1-6, wherein the first motor and the second motor are each movable in the Z-axis a distance equal to or greater than 60mm from the stage.

8. The apparatus of any one of claims 1-7, wherein the platen is configured to move the glass sheet in a plane adjacent to the first and second grinding wheels, the plane formed by the X-axis and the Y-axis.

9. The apparatus of claim 8, wherein the platen is configured to move the glass sheet at a rate of about 5 m/min to about 30 m/min.

10. The apparatus of any one of claims 1-7, wherein the first abrasive wheel and the second abrasive wheel each have a thickness sufficient to provide contact of greater than or equal to about 25 mm.

11. The apparatus of any one of claims 1-7, wherein the first motor and the second motor are urged toward the table.

12. The apparatus of claim 11, further comprising one or more of an air bearing or a force transducer connected to the first motor and the second motor.

13. The apparatus of any of claims 1-7, wherein the first motor and the second motor are configured to operate at a speed of about 600rpm to about 3000 rpm.

14. The apparatus of any one of claims 1-7, further comprising a first plurality of perimeter liquid cooling nozzles adjacent to the first mandrel and positioned to direct cooling liquid toward the perimeter edge of the first abrasive wheel, and a second plurality of perimeter liquid cooling nozzles adjacent to the second mandrel and positioned to direct cooling liquid toward the perimeter edge of the second abrasive wheel.

15. the apparatus of any one of claims 1-7, further comprising a plurality of distal liquid cooling nozzles positioned away from the first and second grinding wheels and positioned to direct cooling liquid toward the edge of the glass sheet.

16. A method of finishing an edge of a glass sheet, the method comprising:

supporting a glass sheet on a platen, a portion of the glass sheet extending a distance from the platen, the glass sheet including a first surface, a second surface opposite the first surface, and an end surface, the first surface intersecting the end surface along a first edge, and the second surface intersecting the end surface along a second edge, wherein an X-axis is a direction of lateral movement in a plane of the glass sheet on the surface, a Y-axis is a direction of longitudinal movement in a plane perpendicular to the X-axis, and a Z-axis is a direction of movement perpendicular to the plane;

Contacting the first edge with at least one first grinding wheel disposed on a first spindle shaft of a first motor, the first grinding wheel being substantially disc-shaped;

contacting the second edge with at least one second grinding wheel disposed on a second spindle shaft of a second motor, the second grinding wheel being substantially disc-shaped; and

Relative movement between the first and second grinding wheels and the glass sheet occurs during contact of the first and second grinding wheels with the first and second edges, respectively, thereby beveling the first and second edges.

17. The method of claim 16, wherein the bevel is less than or equal to about 5% of the thickness of the glass sheet.

18. The method of any of claims 16-17, wherein the platen is configured to move the glass sheet at a rate of about 5 m/min to about 30 m/min.

19. The method of any one of claims 16-18, wherein the first abrasive wheel and the second abrasive wheel each have a thickness sufficient to provide a contact of greater than or equal to about 25mm, respectively.

20. the method of any of claims 16-19, further comprising providing a force to urge the first motor and the second motor toward the table.