KR20030050296A - Process for fabricating a mold of light-guide plate, which having non-isosceles triangled sectional shape on its surface, and the mold thereof - Google Patents

Abstract

PURPOSE: A method for manufacturing a light guide plate mold whose surface has an unequilateral triangle section and the mold fabricated by the method are provided to fabricate a light guide plate using a micro-electro-mechanical process. CONSTITUTION: A substrate having a surface that is not parallel with two crystalline planes anisotropically etched is prepared. An etching mask is formed on the surface of the substrate. The substrate is anisotropically etched to form a groove(110) having a shape of an unequilateral triangle section. A light guide plate mold material is filled in the groove formed on the surface of the substrate, to form a light guide plate mold. The light guide plate mold is separated from the substrate.

Description

TECHNICAL FIELD OF THE INVENTION A method for manufacturing a light guide plate mold having an equilateral triangular cross section on its surface, and a template thereof.

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method for manufacturing a light guide plate used for a liquid crystal display (LCD) or other light source for backlight, and a template thereof, and more particularly, to a method for manufacturing a light guide plate having an asymmetrical groove and a template thereof.

In a general liquid crystal display, since the liquid crystal itself does not emit light, a backlight in the form of a surface light source that maintains brightness by supplying light to the entire screen is required. This backlight unit should basically include a light source, especially when the light source is located on the side requires a unit to perform a special function that can convert the direction of light to the front of the LCD panel.

In order to perform this function, a light guide plate is generally used. The light guide plate reflects or refracts the light toward the front of the plate by using a dot-shaped printing pattern or minute mechanical irregularities disposed on the surface when the light emitted from the light source of the side passes into the transparent light guide plate. , Is one of the most important units of backlight unit.

1 is a schematic diagram showing how the direction of light changes inside a light guide plate having a groove 14 on a bottom surface thereof. A transparent acrylic plate-like light guide plate body 12 and side light source 11 are arranged as shown in the drawing, and a bottom surface portion includes a prism-shaped groove 14 having a triangular cross section and a reflective film 13.

The light emitted from the side light source 11 has various angles in the horizontal direction inside the body of the light guide plate, and light (a) incident at a predetermined angle or less with respect to the surface of the light guide plate is reflected back into the light guide plate due to total reflection and serves as a backlight. However, if there is a groove 14 on the bottom, this light b is refracted or reflected by the groove and exits the light guide plate to function as the backlight of the LCD.

The degree of reflection and refraction of light varies greatly depending on the shape of the groove. In particular, when the groove cross section is an isosceles triangle rather than an isosceles triangle, the light efficiency of the light guide plate is further improved. Here, the light efficiency refers to the degree to which the light guide plate is directed toward the front of the light source from the side light source, and the reason why the efficiency is improved when it is an isosceles triangle can be easily understood in comparison with FIGS. 2 and 3.

FIG. 2 schematically illustrates the propagation direction of light incident on the groove at various angles when the cross section of the groove is an isosceles triangle, that is, when x and y are the same. Light entering the groove at the same or similar angle as the light c proceeds from the light guide plate 12, which is a dense medium, to the air 14-1, which is a slight medium. Facing each other with respect to the upper surface of the light guide plate, so as to be out of the light guide plate.

However, the light entering at the same angle as the light d is reflected by the reflecting surface 13 after being folded as shown, and enters the light guide plate main body again so as to collide with the boundary surface q. The angle q is equal to the angle q ', which is the angle at which the light first hits the light guide plate, and this angle is smaller than the total reflection angle so that it does not escape the light guide plate again toward the inside of the light guide plate. In other words, the light is at an angle where the grooves do not function at all. In addition, the light e is also light that does not contribute to the backlight by refracting and not leaving the light guide plate as shown. After all, if the light having such an angle is not used, the light efficiency of the light guide plate is reduced so much, and a new type of groove is required to overcome this.

As such a new type of groove, grooves of asymmetric or anisotropic triangular shape as shown in FIG. 3 may be used. In the present invention, an asymmetric or an equilateral triangle refers to a case where a groove having a triangular cross section does not have the same bottom angle (x ') and far bottom (y') with respect to the light source. Although the light source is not shown in FIG. 3, it will be obvious to those skilled in the art that the light source will be on the left side of the drawing in view of the traveling direction of the light.

In FIG. 3, the lights c ', d' and e 'are light entering the groove at the same angle as the light c, d and e in FIG. 2. However, since the angles (x ', y') are not the same as in FIG. 2, the direction of light travel is completely wrong after hitting the groove. That is, the light c 'is totally reflected at the surface 31 of the groove of the base angle x' which is more sharp than the x of FIG. 2 to be out of the upper surface of the light guide plate, but is similar to FIG. Since the inclination of) is smaller than the inclination of the surface 31, unlike the light d of FIG. 2, the inclination of the c) is refracted to the surface of the light guide plate rather than to the inside of the light guide plate, thereby leaving the light guide plate. The light e 'also has an inclination of the surface 32 smaller than that of the surface 31 such that the angle r' hitting the upper surface of the light guide plate is larger than the angle of FIG. 2, thereby leaving the top surface of the light guide plate without total reflection.

As described above, in the light guide plate using the refraction phenomenon in the groove, when the base angles of the cross-section triangles are not equal to each other, especially when the base angle near the light source is larger than the base angle far from the light source, the incident light is as shown in the upper part of the light guide plate. It is well known that the off-plane probability is significantly greater than when the groove cross section is an isosceles triangle.

Further, when the reflecting plate 41 is formed in close contact with the bottom of the groove, as shown in FIG. 4, when the bottom angle x ″ of the side close to the light source is smaller than the bottom angle y ″ of the far side to the light source, it is incident as shown. It is sensational to see that the probability of the light falling off the top of the light guide plate is greatly increased.

Therefore, in the light guide plate using the groove, the light emission efficiency is higher when the cross section of the groove is an isosceles triangle than the isosceles triangle, but the problem is that the method of making such an isosceles triangle cross section on the light guide plate is not as simple as expected. Is the point. That is, since the groove used in the light guide plate has a fine structure having a width of about 100 μm to 10 μm, it is never easy to process it asymmetrically and evenly.

The general manufacturing method is injection molding by filling PMMA or resin, which is a raw material of the light guide plate, in a mold having a mold of an asymmetric groove, or forming a groove by pressing a stamp having a sharp end on the surface of the light guide plate. It's a mechanical way. However, in order to use this method, the injection molding die or the stamp die itself must be finely machined, and in particular, the blade dies that make fine grooves must be precisely asymmetrically processed again, which increases the probability of failure and accordingly increases the manufacturing cost of the light guide plate. It is one cause.

In the manufacture of light guide plates, this problem remains a challenge that many engineers have yet to solve.

In the present invention, a breakthrough MEMS (MicroElectroMechanical) process is introduced in order to solve the above-mentioned problems with the machining of the mold itself, and an isosceles triangle cross section using a mold made of silicon (Si) instead of a metal mold generally used. To provide a method for manufacturing a light guide plate having a groove of.

Another object of the present invention is to provide a silicon mold for forming a groove of an isosceles cross section and a processing method thereof in order to achieve the above object.

The present invention provides a method for processing a silicon mold of a groove having an anisotropic triangular cross section using the anisotropic etching property of the silicon substrate, and further provides a method for processing an anisotropic cross-sectional groove mold in all cases where anisotropic etching is possible. For that purpose.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows the propagation direction of the light in the light guide plate which has the groove in the bottom surface.

Figure 2 is a schematic diagram showing the direction of light travel inside the light guide plate having a groove of an isosceles triangle cross section on the bottom.

Figure 3 is a schematic diagram showing the direction of light travel inside the light guide plate having a groove of an equilateral triangular cross section on the bottom.

Fig. 4 is a schematic diagram showing the direction of light propagation in a light guide plate having a groove of an equilateral triangular cross section on its bottom face and a reflecting plate thereof;

5 is a schematic view of a silicon ingot grown in the (100) plane direction.

FIG. 6 is a substrate slicing the silicon ingot of FIG. 5 with an angle α. FIG.

FIG. 7 is a schematic view showing arrangement of crystal planes within the substrate of FIG. 6; FIG.

8 to 10 illustrate a step of manufacturing a groove mold on a surface using the substrate.

11 is a perspective view of a silicon substrate produced by the process of the present invention.

12 to 13 illustrate manufacturing a light guide plate mold using the silicon substrate.

14 is a perspective view of a light guide plate produced by the process of the present invention.

FIG. 15 is a schematic view showing a light propagation direction in a light guide plate having a protrusion of an isosceles triangle cross section on a surface of another embodiment of the present invention. FIG.

Description of the main parts of the drawing

61: Silicon Substrates Having Surfaces That Are Not Parallel to (111) Plane and (100) Plane

71: (100) crystal plane of silicon 72, 72 ': (111) crystal plane of silicon

81: etching mask 110: silicon mold substrate

120: light guide plate template 130: light guide plate disc

130 ': final light guide plate

A method of fabricating the light guide plate template of the present invention for achieving this object comprises the steps of providing a substrate having a surface that is not parallel to each of the two crystal faces capable of anisotropic etching, and forming an etching mask on the surface of the substrate. Forming an groove on the surface of the substrate by anisotropic etching on the substrate, and filling the surface of the substrate with a light guide plate material to form a light guide plate template; Separating from the. In addition to the silicon substrate, various substrates capable of anisotropic etching may be used. In the case of a silicon substrate, a combination of (100) and (111) surfaces may be used as two crystal planes capable of the anisotropic etching.

The present invention proposes a method of manufacturing a mold using a chemical etching method rather than a machining method, and by using a substrate capable of anisotropic etching, it is possible to manufacture an isosceles mold to solve the problem of the conventional method significantly Providing.

Hereinafter, with reference to the drawings will be described embodiments of the present invention;

5 is a schematic diagram showing a silicon ingot of a silicon single crystal made by a Cz (Czochralski) method. For example, the ingot of FIG. 5 is an ingot grown in the (100) plane direction, and the (111) plane is formed to be 54.74 ° with the (100) plane crystallographically. The silicon wafer used as the substrate in the embodiment of the present invention is a wafer having a surface that is not parallel to each of the two surfaces, for example, slicing a surface having an angle difference between the (100) plane and α as shown in the direction 51 shown. provided by slicing.

Slicing the ingot with an angle α results in a wafer substrate of elliptical wafers such as six. In the illustrated situation, for example, if the angle α is greater than 0 ° and less than 54.74 °, but particularly an angle that may have etching selectivity by anisotropic etching of silicon described later, the (111) and (100) planes as described above Any angle that is not parallel to is applicable. The reason why the surface between the (111) plane and the (100) plane is particularly selected in silicon is because the etching selectivity of the two surfaces is large, so that it is easy to obtain the mold desired by the present invention, which will be described later. In addition, these aspects are only one embodiment and reveals that the scope of the present invention is not limited thereto.

FIG. 6 shows an elliptical silicon wafer 61 sliced in the direction 51 of FIG. 5. Face 100 maintains 90 ° -α with the wafer surface and (111) face maintains 90 °-(54.74 ° -α), ie 35.26 ° + α. For example, if the angle α is 20 °, the (100) plane will be 70 ° and the (111) plane will be 55.26 ° with respect to the wafer surface.

7 is a cross-sectional view of the substrate 61, in which (100) planes 71 and (111) planes 72 and 72 'are shown. Crystallographically, the (111) plane has two planes (72, 72 ') between 109.48 °.

The (100) plane and the (111) plane of the silicon substrate have a property that the etching rate is significantly different with respect to an etching solution such as KOH. That is, the (100) plane is about 100 times faster than the (111) plane, which is understood as a phenomenon that occurs because the (111) plane has a higher atomic density of the crystal plane than the (100) plane. Etching the faces with the difference in etching rates with the same etching solution enables the formation of various types of fine structures by the geometric arrangement between the surfaces (this is commonly called anisotropic etching, and the speed difference is The MEMS process is a representative process using such anisotropic etching. The present invention can be said to have a great feature in the method for manufacturing a light guide plate template for producing a groove having an isosceles triangular cross-section by etching the surfaces capable of anisotropic etching.

8 to 11 sequentially illustrate a method of fabricating a silicon substrate template having a groove form having an asymmetric triangular cross section using the elliptical wafer substrate 61.

FIG. 8 is a cross-sectional view showing a state of depositing Si ₃ N ₄ to be used as an etching mask 81 on the wafer substrate 61. In general, these kinds of films serve to protect the silicon from being etched from the acid or KOH solution used to etch the silicon, and are deposited and processed by sputtering or reactive ion etching (RIE). In FIG. 8, the etching mask 81 has a portion where the groove mold is to be manufactured, and the crystallographic arrangement of the lower substrate is the same as that of FIG. 7. In addition, the etching mask is one embodiment, and in addition, any film having a certain degree or more resistance to the silicon etching solution, for example, a nitride film such as AlN or GaN or an oxide film such as SiO ₂ may be used.

FIG. 9 illustrates an intermediate step of etching the wafer substrate 61 of FIG. 8 using a KOH solution or the like. As the etching solution, in addition to the KOH-based solution, an acid solution such as HF, NaOH, ethylene diamine, hydrazine, buffered oxide etchant (BOE), and nitric acid such as HNO ₃ may be used. In addition, any method capable of anisotropic etching, such as chemical plasma etching, may be used.

Since the crystallographic arrangement of the substrate surface is as shown, in this etching process, the etching rate in the (100) plane direction is faster than the speed in the (111) plane direction, and as shown is deeply etched in the (100) plane direction. About this, the (111) planes are formed in both sides.

10 shows a state in which the etching process is completed, the (100) plane disappears as the (111) planes contact each other, and a cross section of an isosceles triangle to be obtained in the present invention is made. FIG. 11 shows the final form of the silicon mold 110 with the etch mask removed from the etched substrate. Note that grooves having a plurality of equilateral triangular cross sections were formed on the silicon substrate surface.

12 to 14 relate to a method of manufacturing a light guide plate mold to be used in a stamping process or an injection molding process using the silicon substrate mold.

In FIG. 12, a metal, such as nickel (Ni), is filled in the silicon substrate mold by plating or other method to fabricate the light guide plate mold 120. In general, nickel is widely used as a mold material, but metals and ceramics of various materials may be used as the mold material. In the case of ceramics, a powdery material may be filled and then heat-treated to form a mold.

These mold materials are used separately from the silicon substrate mold. Since the two materials are so different, no bonding or bonding takes place, so with a little force the two molds are easily separated. In order to facilitate separation, a lubricant or the like may be applied to the surface of the silicon substrate before the filling step of FIG. 12.

FIG. 13 schematically illustrates a process of forming a groove on the surface of the light guide plate disc 130 by using the light guide plate mold 120 formed by the above-described process, and FIG. 14 is finally made by the process of the present invention. The light guide plate 130 'is shown. It can be seen that the groove of an isosceles triangular cross section to be obtained by the present invention is formed on the surface. In LCD manufacturing, the light guide plate is turned upside down and placed under the LCD panel to form the whole system.

Although not shown, the light guide plate mold 120 manufactured in FIG. 12 may be assembled to an injection molding mold, and then the light guide plate material may be filled into the mold to manufacture the light guide plate by injection molding.

15 is a view showing still another embodiment of the present invention. FIG. 15 is different from the above-described embodiment, the protrusion having a cross section of an isosceles triangle is formed on the bottom surface of the light guide plate instead of the groove of the equilateral cross section. Briefly describing the direction of the light in the protrusion, the light 140 'is originally a light having an angle totally reflected inside the light guide plate 141 as shown if the protrusion 142 is absent or the cross section of the protrusion is an isosceles triangle. Likewise, the light cannot escape inside the light guide plate. However, the light 140 is refracted and reflected as shown by the protrusion 142 of the equilateral triangular cross section of the present invention, and then may escape the light guide plate.

The method of making a conduit plate structure with such protrusions is simple. Since the above-described silicon substrate is engraved with the intaglio, the light guide plate having the embossed portion as shown in FIG. 15 may be fabricated by directly filling the raw material of the light guide plate, or the nickel mold of the embossed as described above is made, and then the intaglio is again inscribed from this embossment. A second mold may be made and the light guide plate material may be filled into the mold to produce the structure of FIG. 15. Of course, if necessary, lubricants may be applied to the surface to make the molds easily come off.

The present invention provides a method for manufacturing an asymmetric groove by a breakthrough method that was not conceived in the conventional light guide plate manufacturing method.

In the conventional method, when manufacturing a mold, a fine groove mold is manufactured by performing precise mechanical cutting on a mold disc, but it is never easy to uniformly process an asymmetric and an equilateral triangle cross section, and once a mold is made wrong Since the entire mold must be discarded, this cost has increased the manufacturing cost of the light guide plate.

In order to solve the problems of the conventional method, the mold is manufactured using a chemical etching method rather than a machining method, and the problem of the existing method is groundbreaking by allowing an anisotropic mold to be manufactured using a substrate capable of anisotropic etching. It provided a means to solve.

By using the method of the present invention, it is possible to easily produce grooves of an isosceles triangle section having a uniform angle, and furthermore, it is possible to precisely control the process variables and the occurrence of errors during the mold fabrication.

Those skilled in the art having understood the above description will appreciate that various changes and modifications can be made without departing from the spirit of the present invention. For example, the mold of the present invention can be manufactured using various substrates capable of anisotropic etching such as GaAs in addition to the silicon substrate, and the substrate slicing angle of the ingot is also determined according to the angle when the base angle of the isosceles cross section is inclined. You can adjust it at will. In addition, in the silicon substrate, in addition to the (100) and (111) planes, any combination of surfaces such as (211) planes, (111) planes, (110) planes, and (111) planes is a combination having etching selectivity. It is also possible.

In addition, according to the shape of the etching mask and the degree of etching, it is also possible to manufacture a mold having an asymmetric pyramidal needle shape of the island shape, the production of the pyramid shape is well known in the solar cell field, so a detailed description thereof will be omitted. However, it is natural that the substrate used at this time should also use a sliced substrate so as not to be parallel to a plurality of surfaces capable of anisotropic etching.

Therefore, the protection scope of the present invention should not be limited to the contents described in the above embodiments, but should be defined by the following claims.

Claims (11)

In the method for manufacturing a light guide plate template having an isosceles triangular cross section on the surface using a substrate capable of anisotropic etching, Providing a substrate having a non-parallel surface for each of the two crystal faces capable of anisotropic etching; Forming an etching mask on the substrate surface; Performing anisotropic etching on the substrate to form grooves of an equilateral triangular cross section on the surface; Filling the surface of the substrate with a light guide plate material to form a light guide plate template; Separating the light guide plate mold from the substrate Light guide plate mold manufacturing method comprising a. The method of claim 1, wherein the substrate is a silicon substrate. 3. The method of claim 2, wherein the two anisotropic etchable crystal surfaces are a (100) plane and a (111) plane, respectively. The method of claim 1, wherein the light guide plate mold material is nickel. In the light guide plate manufacturing method having a groove of an equilateral triangular cross section on the surface, Providing a substrate having a non-parallel surface for each of the two crystal faces capable of anisotropic etching; Forming an etching mask on the substrate surface; Performing anisotropic etching on the substrate to form grooves of an equilateral triangular cross section on the surface; Filling the surface of the substrate with a light guide plate material to form a light guide plate template; Separating the light guide plate template from the substrate; Filling the light guide plate disc with the light guide plate mold to transfer the shape of the mold; Separating the transferred light guide plate Light guide plate manufacturing method comprising a. In the light guide plate manufacturing method which has the protrusion part of an equilateral triangular cross section on the surface, Providing a substrate having a non-parallel surface for each of the two crystal faces capable of anisotropic etching; Forming an etching mask on the substrate surface; Performing anisotropic etching on the substrate to form grooves of an equilateral triangular cross section on the surface; Transferring the shape of the mold by contacting the light guide plate disc with the substrate; Separating the light guide plate on which the form shape is transferred to form a protrusion; Light guide plate manufacturing method comprising a. In the light guide plate manufacturing method which has the protrusion part of an equilateral triangular cross section on the surface, Providing a substrate having a non-parallel surface for each of the two crystal faces capable of anisotropic etching; Forming an etching mask on the substrate surface; Performing anisotropic etching on the substrate to form grooves of an equilateral triangular cross section on the surface; Filling the surface of the substrate with a first LGP material to form an embossed first LGP template; Separating the first LGP template from the substrate; Filling the first LGP template with a second LGP material to form an intaglio second LGP template; Separating the second LGP template from the first LGP template; Transferring the shape of the mold by contacting the light guide plate disc with the second light guide plate mold; Separating the light guide plate on which the form shape is transferred to form a protrusion; Light guide plate manufacturing method comprising a. A silicon mold substrate for manufacturing a light guide plate having an equilateral triangular cross section on a surface thereof, wherein the surface of the silicon mold is a surface which is not parallel to each of two crystal planes capable of anisotropic etching. . The silicon mold substrate for manufacturing a light guide plate according to claim 8, wherein the two anisotropically etchable crystal surfaces are a (100) plane and a (111) plane, respectively. The method of claim 1, wherein the groove is groove-shaped. The silicon mold substrate of claim 8, wherein the groove has a groove shape.