Patent Application
20070113713
This disclosure relates to a method of aligning a cutting tool disposed upon a turning machine. In particular, it relates to a method of alignment for a diamond-cutting tool in order to manufacture a brightness enhancing display film with prism apexes aligned normal to the surface and thus having maximum on-axis brightness in a liquid crystalline backlight assembly.
Brightness enhancing display films generally termed “prism sheets” are used in liquid crystalline display devices in order to collimate the light passing through a liquid crystal display. It is generally desirable to employ prisms on the brightness enhancing display films that have vertex angles of about 90 degrees. It is further desirable for a bisector of the vertex of the prisms to be normal to the surface of the brightness enhancing display film. This is shown in the
If the bisector of the vertex is not normal to the base, there is a reduction in the on-axis concentration of light and a displacement of the direction of maximum light concentration. A “misalignment angle” can be used to characterize the difference between the bisector of the vertex angle of the prism and the surface of the brightness enhancing display film. The misalignment angle is defined as 90 degrees minus the angle between bisector of the vertex and the surface of the brightness enhancing display film, i.e. the optimum display film performance is obtained as the misalignment angle is reduced to zero.
The on-axis brightness is the brightness measured in a direction perpendicular to the surface of the brightness enhancing display film. The surface of the brightness enhancing display film is parallel to the base of the prisms that are disposed upon the film substrate as shown in the
Brightness enhancing display films are manufactured by pressing a malleable material against a prism-shaped mold. The malleable material is disposed upon an optically transparent film substrate. Possible manufacturing processes include melt calendaring, embossing, injection molding, compression molding, casting and curing of thermally cured resin onto a substrate, and casting and curing of UV cured resin onto the film substrate. For example, the mold can be an electroform which is a replica of a drum that has a negative image of a prism surface machined on its outer surface by using a turning machine such as a lathe. The prisms on the drum are machined with a diamond-cutting tool.
In general, a misalignment of the cutting tool during the machining can result in a defective drum. The defective drum produces a defective electroform which then stamps out a defective brightness enhancing display film. One method of correcting this defect is to try to align the cutting tool by realigning the cutting tool holder using the edge of the tool holder as a locating device. An embodiment of this method is depicted in the
It is therefore desirable to have a method for aligning the cutting tool so as to facilitate the manufacture of drums that permit the misalignment angle to be about 0 degrees. This minimizes the defects in the prism sheets.
Disclosed herein is a method for aligning a cutting tool comprising displacing a first slide comprising a microscope in a first direction at a first speed; displacing a second slide comprising an adjustable tool holder and a cutting tool in a second direction at a second speed; wherein the adjustable tool holder is in operative communication with the cutting tool; observing an actual path of travel of a cross hair center of the microscope with respect to a cutting edge of the cutting tool; and adjusting the position of the cutting tool so that the cutting edge of the cutting tool and the cross hair center lie in the same plane during the travel of the cross hair center.
Disclosed herein is a method for aligning a cutting tool comprising locating a cross hair center of a microscope above a first point on a cutting edge of a cutting tool; wherein the cross hair center and the first point lie in a plane; displacing a first slide comprising the microscope in a first direction at a first speed; displacing a second slide comprising an adjustable tool holder and the cutting tool in a second direction at a second speed; wherein the adjustable tool holder is in operative communication with the cutting tool; terminating the displacement of the first slide and the second slide; observing a second point on the cutting edge of the cutting tool with the cross hair center of the microscope; and adjusting the tool position to permit the second point and the cross hair center to lie in the plane.
Disclosed herein too is a method for aligning a cutting tool comprising selecting two or more points on a first cutting edge and two or more points on a second cutting edge of a cutting tool; wherein the selecting is accomplished with a cross hair center of a microscope; determining mathematical equations to the first cutting edge and the second cutting edge; mathematically determining a location of a cutting tip of the cutting tool with respect to a drum; directing travel of the cross hair center according to the mathematical equations for a desired location of the first cutting edge or the second cutting edge; and adjusting the cutting tool to permit the travel of the cross hair center to trace a path that encompasses either the first cutting edge, the second cutting edge or both the first cutting edge and the second cutting edge.
With reference now to the Figures, wherein like elements are numbered alike:
It is to be noted that the terms “first,” “second,” and the like as used herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The terms “a” and “an” do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item. The modifier “about” used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., includes the degree of error associated with measurement of the particular quantity). It is to be noted that all ranges disclosed within this specification are inclusive and independently combinable.
Disclosed herein is a method for aligning a cutting edge of a cutting tool in such a manner that the tip of the tool is aligned normal to the surface to be machined, and such that a brightness enhancement film made from such a machined surface has maximum on-axis brightness in typical LCD backlight modules. An exemplary cutting tool is a diamond-cutting tool. Aligning the cutting tool prior to a machining operation reduces the probability of manufacturing a defective cylindrical master or electroform, which reduces the probability of manufacturing a defective brightness enhancing display film.
In a first embodiment, the method comprises displacing a microscope in a first direction at a first speed while simultaneously displacing a base on which a micrometer and cutting tool are disposed in a second direction at a second speed. The cutting tool is in operative communication with an adjustable tool holder. During this relative displacement of the microscope and the cutting tool, a cutting edge of the cutting tool is observed under the microscope. If the intersection point of the cross hairs (hereinafter cross hair center) of the microscope (located in the eye piece of the microscope) remains in the same plane that encompasses the cutting edge of the cutting tool, then the cutting tool is assumed to be properly aligned. If on the other hand, the cross hair center is observed to move out of the plane that encompasses the cutting edge of the cutting tool (i.e., off the edge of the diamond tool), then a micrometer is used to modify the position of the cutting tool so that the cutting edge of the cutting tool and the cross hair center lie in the same plane during the entire path of travel of the cross hair center.
The term “encompasses” implies that the entire length of a cutting edge of the cutting tool lies in a given plane or along a given path. The plane can be a vertical plane, a horizontal plane or any plane therebetween. An exemplary plane is a vertical plane. While all future embodiments in this specification have been described as occurring in the vertical plane, it is to be noted that they can be performed in any desired plane.
In one embodiment, the cutting tool can be adjusted using the micrometer. The micrometer can be adjusted manually or using a numerically controlled device, such as, for example, a stepper motor. In another embodiment, the cutting tool can be adjusted manually without using the micrometer, i.e., the position of the adjustable tool holder can be modified manually.
In a second embodiment, the method comprises displacing the microscope along a line in a plane that is supposed to encompass the cutting edge of the cutting tool. The microscope can be stopped at any two points during its displacement or travel. If the cross hair center lies in the same plane as the cutting edge at each of these two points, then the cutting tool is presumed to be properly aligned. If however, the cross hair center is determined not to lie in the same plane as the cutting edge at each of the two points, then the position of the cutting tool is modified by using the micrometer. The modification of the position of the cutting tool is performed till the two points on the edge of the cutting tool lie in the same plane that the cross hair center travels in.
In a third embodiment, a method for aligning a cutting tool comprises selecting two or more points on a first cutting edge and two or more points on a second cutting edge of a cutting tool. If the tip of the cutting tool is used as a first point then only one other point may be selected on each edge. These points are used to determine mathematical equations to the first cutting edge and the second cutting edge. The mathematical equations are advantageously used to compute cutting tool angles and a location of the cutting tool tip. If the mathematical equations define the plane that encompasses the appropriate cutting edge, then the cutting tool is presumed to be properly aligned. If not, the micrometer is used to modify the position of the cutting tool to correct the alignment. This method may advantageously used to determine the location of the cutting tool tip when the tip is pointed or curved.
In the first embodiment, the method comprises displacing a microscope in a first direction at a first speed while simultaneously displacing a micrometer and a cutting tool in a second direction at a second speed. During this relative displacement of the microscope and the cutting tool, the cross hair center of the microscope is programmed to traverse a line that lies in a vertical plane that is inclined at 45 degrees to the surface of a drum that is to be machined. It is to be noted that the angle between the vertical plane and the surface of the drum is dependent upon the angle at the tip of the cutting tool. If the angle at the tip is 90 degrees, then the vertical plane is inclined at an angle of 45 degrees to the surface of the drum.
The edge of the cutting tool need not always be observed directly through the microscope. In one embodiment, observing the tool edge through the microscope can include forming an image of the tool edge on a video camera attached to the microscope, as opposed looking through an eyepiece.
With reference now to the
During the alignment process, the first slide 20 is displaced in a first direction at a first speed, while the second slide 30 is displaced in a second direction at a second speed. The first and second speeds can be the same or different. In an exemplary embodiment, the first and second speeds are selected to permit the cross hair center to travel in a plane that encompasses a cutting edge of the cutting tool. In yet another embodiment, the first and second speeds are selected to permit the cross hair center to travel in a vertical plane inclined at 45 degrees with respect to an outer surface of the drum prior to machining. As depicted in the
In an exemplary embodiment, the first slide 20 can be displaced along an arbitrary x-axis direction, while the second slide 30 can be displaced along an arbitrary z-axis direction. The x-axis direction is mutually perpendicular to the z-axis direction. While it is generally desirable for the first slide 20 and the second slide 30 to be displaced in mutually perpendicular directions, other angles between the first slide 20 and the second slide 30 can be contemplated and used. In one embodiment, the angle between the directions of displacement of the first slide and the second slide is greater than or equal to about 75 degrees. In another embodiment, the angle between the directions of displacement of the first slide and the second slide is greater than or equal to about 55 degrees. In yet another embodiment, the angle between the directions of displacement of the first slide and the second slide is greater than or equal to about 45 degrees.
With respect now once again to the
It is generally desirable for the cross hair center to travel in a vertical plane that is inclined to the surface of the drum at an angle that is generally equal to about half of the angle at the cutting tip 330 of the diamond cutting tool. For example, when the angle between the first cutting edge 110 and the second cutting edge 220 is 90 degrees (i.e., the angle at the cutting tip is 90 degrees), the displacement between the first slide 20 and the second slide 30 causes the cross hair center to travel in a vertical plane that is inclined at an angle of 45 degrees to the surface of the drum. In another example, when the angle between the first cutting edge 110 and the second cutting edge 220 is 110 degrees, the displacement between the first slide 20 and the second slide 30 causes the cross hair center to travel in a vertical plane that is inclined at an angle of 55 degrees to the surface of the drum. In yet another example, when the angle between the first cutting edge 110 and the second cutting edge 220 is 70 degrees, the displacement between the first slide 20 and the second slide 30 causes the cross hair center to travel in a vertical plane that is inclined at an angle of 35 degrees to the surface of the drum.
A jaw 37 of the micrometer 32 is in operative communication with the tool base 33 via a cantilever 39. The position of the tool base 33 and hence of the cutting tool 35 can be adjusted by rotating the micrometer screw 38. A compression spring 36 is in operative communication with the cantilever 39 and the tool base 33. The compression spring 36 reduces any play or vibration that may be generated during the machining and also facilitates maintaining the desired position of the tool base 33 until the micrometer screw 38 is rotated.
With reference now to
In one embodiment, in one exemplary manner of aligning the cutting tool 35, a target-point on an edge of the cutting tool 35 is displaced through a fixed point on the microscope 24 as shown in the
During the oscillation along the relative motion line, it is desirable for the intersection point of the cross hairs of the microscope 24 to intersect with the first cutting edge 110 or the second cutting edge 220 of the cutting tool, throughout the travel of the microscope 32. If during the oscillation along the relative motion line, it is observed that the intersection point of the cross hairs deviates from the vertical plane encompassing the first cutting edge 110 or the second cutting edge 220 on the cutting tool, the micrometer screw 38 is appropriately rotated to promote the first cutting edge 110 or the second cutting edge 220 of the cutting tool 35 to lie in the vertical plane. Thus rotation of the micrometer screw 38 re-aligns the cutting tool 35. This procedure can be conducted along the first cutting edge 110 and the second cutting edge 220 in order to insure greater accuracy if desired.
When the cutting tool has linear cutting edges 110 and 220, it is desirable for the cross hair center to travel in a vertical plane that encompasses the cutting edge of the cutting tool 35. In other words, the cross hair center traces the cutting edge of the cutting tool. When the cross hair center traces the cutting edge of the cutting tool 35, it indicates that the cutting edge of the cutting tool 35 is appropriately aligned. It is to be noted however, that the desirability of having the cutting edge lie in a vertical plane is related to the position occupied by the cutting tool 35 in the adjustable tool holder 34. For example, if the adjustable tool holder 34 were to be rotated clockwise through an angle of 30 degrees from a vertical, then it would be desirable for the cross hair center and the vertical plane to be rotated clockwise through 30 degrees as well in order for the cross hair center to trace the cutting edge of the cutting tool 35.
When the cutting tool has curvilinear cutting edge(s) 110 and/or 220, then it is desirable for the first speed and the second speed to be selected so as to permit the cross hair center to trace the curvilinear cutting edge of the cutting tool 35. If the cross hair center does not trace the curvilinear cutting edge of the cutting tool 35, then the micrometer screw 38 is appropriately adjusted in order to realign the cutting tool 35. Realignment of the cutting tool 35 is continued until the cross hair center traces the curvilinear cutting edge of the cutting tool 35.
In another embodiment, in another manner of determining the alignment of the cutting tool 35, the cross hair center is displaced in a vertical plane that encompasses the edge of the cutting tool 35. In this embodiment, the intersection point of the cross-hairs is first positioned at a first point located on the first cutting edge 110 of the cutting tool as shown in
In yet another embodiment, depicted in the
While the embodiment depicted in the
In another embodiment, an aspheric sag equation that describes the curvature of the cutting edges can be programmed into the machine. An exemplary aspheric sag equation for parabolic surfaces is described in U.S. Patent Application 2004/0109663 to Olczak, the entire contents of which are hereby incorporated by reference. The first slide 20 and the second slide 30 can be displaced at rates effective to permit the cross hair center to travel along a locus defined by the aspheric sag equation. If the cross hair center does not travel along the cutting edges of the cutting tool 35, then the position of the cutting tool 35 is adjusted as required using the micrometer.
These methods for aligning the cutting tool are advantageous in that it compensates for any misalignment between the cutting tool and the fixture 34 or any misalignment between the fixture 34 and the tool base 33. The precision offered by the rotating the micrometer screw 38 is greater than that offered by tapping the fixture into alignment as indicated in the
In one embodiment, the aforementioned methods for aligning the cutting tool promotes maintaining the misalignment angle of the prisms produced from the drum to be about 0 degrees. In another embodiment, the misalignment angles of the prisms produced from the drum is up to about ±1 degrees. In yet another embodiment, the misalignment angles of the prisms produced from the drum is up to about ±2 degrees. In yet another embodiment, the misalignment angles of the prisms produced from the drum is up to about ±5 degrees. In yet another embodiment, the misalignment angles of the prisms produced from the drum is up to about ±10 degrees. An exemplary misalignment angle is less than or equal to about ±0.5 degrees.
Drums manufactured by the aforementioned methods can be advantageously used to produce replica tools that are free from inherent machining defects. An exemplary replica tool is a metal electroform. Replica tools can be used to manufacture brightness enhancing display films that have prisms whose misalignment angles are up to about ±2 degrees. It is generally desirable for the replica tool to have prisms whose misalignment angles are less than or equal to about ±0.5 degrees. Brightness enhancing display films manufactured from the replica tools can be advantageously used in display devices. Exemplary display devices are television screens or computer screens that employ liquid crystals.
While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention.
