KR101115095B1 - Method for desigining diffusing film having irregular spherical shaped patterns - Google Patents

Abstract

The present invention relates to a method of designing a diffusion film having an irregular distribution and having a spherical pattern formed without voids, comprising: a first step of generating irregular and uniform reference points on the entire surface of the film; A second step of forming a convex polygonal pattern having the reference points as one inside; Generating a circle inscribed to the convex polygons; And a fourth step of correcting a center point and a radius in consideration of the number of contacts of the generated circles.

Diffusion Film

Description

Design method of diffusing film with irregularly distributed spherical pattern {METHOD FOR DESIGINING DIFFUSING FILM HAVING IRREGULAR SPHERICAL SHAPED PATTERNS}

The present invention relates to a method for designing a diffuser film having an irregular spherical pattern, and more particularly, to a method for designing a diffuser film having a spherical pattern that has an irregularly distributed shape and is formed without voids.

The diffusion film is applied to the backlight unit of the display device, and refers to an optical film that performs a function of diffusing light emitted from the light source of the backlight unit. Generally, such a diffusion film is prepared by including bead particles having different refractive indices in the film or forming an uneven surface such as a micro lens array on the film surface.

The method of including the beads having different double refractive indices in the film has a high manufacturing cost, and there is a problem in that light is reflected from the surface of the bead particles and the transmittance is lowered. Therefore, in recent years, studies on a method of manufacturing a diffusion film by forming irregularities on the surface of the film instead of the method of using the beads are being actively conducted.

The easiest way to form the diffuser film by forming irregularities on the film surface is to form a spherical lens structure such as a micro lens array. However, in this case, irregularities tend to have a regular pattern, and as a result, moiré occurs due to the interaction between the irregularities formed on the surface of the film and the pixels of the LCD panel, resulting in poor image quality.

Therefore, in order to solve this problem, a method of distributing beads to protrude on the plate and duplicating the shape has been proposed. However, this method has a problem in that it is difficult to repeatedly produce a film of the same pattern and the quality of the product is not uniform.

The present invention is to solve such a problem of the prior art, and an object thereof is to provide a method for producing a diffusion film having a spherical pattern of irregular distribution without repeatability through the entire film area.

To this end, the present invention comprises a first step of generating irregular and uniform reference points on the entire surface of the film; A second step of forming a convex polygonal pattern having the reference points as one inside; Generating a circle inscribed to the convex polygons; And a fourth step of correcting a center point and a radius in consideration of the number of contacts of the generated circles, providing a method of designing a diffusion film having an irregularly distributed spherical pattern.

In this case, the first step may include generating arbitrary points within the entire area of the diffusion film; And measuring the spacing of the points, and removing the points when the spacing of the points is smaller than a predetermined value, and adding the points when the spacing of the points is smaller than a predetermined value.

In addition, the convex polygonal pattern of the second step may be formed by a Voronoi diagram.

In addition, the present invention generates an ellipse including the vertices of the convex polygon between the steps 2 and 3, when the aspect ratio of the ellipse exceeds 1: 2, and inserts a point inside the convex polygon, the convex polygon The method may further include reforming the pattern.

In the present invention, the fourth step may be performed by correcting the center and the radius of the circles of which the number of generated contacts is less than three.

When the diffusion film is produced by the method of the present invention, since there is no regularity in the unevenness, there is no fear of moir occurrence, and since the diffusion film having the same pattern can be repeatedly produced using a mold, the quality of the product can be improved. The advantage is that it can be kept constant.

Hereinafter, the present invention will be described more specifically.

The inventors of the present invention have repeatedly studied to produce a diffusion film capable of reproducing a pattern so as to maintain a constant product quality without regularity in the uneven pattern so that moiré does not occur. The present invention has been accomplished by discovering a method for forming a spherical lens pattern that is completely absent.

The diffusion film design method of the present invention includes a first step of generating irregular and homogeneous reference points on the entire surface of the film; A second step of forming a convex polygonal pattern having the reference points as one inside; Generating a circle inscribed to the convex polygons; And a fourth step of correcting a center point and a radius in consideration of the number of contacts of the generated circles.

1, each step of the method of designing a diffusion film pattern of the present invention is shown. Hereinafter, the present invention will be described in more detail with reference to FIG. 1.

(1) step 1

First, irregular and homogeneous reference points are created over the entire area of a given diffusion film to be produced. In this case, the irregularity means that the distance between each point is not constant, and the uniformity means that the number of points included per unit area is the same.

These irregular and homogeneous reference points can be generated in the following way.

First, as shown in FIG. 1, random spots are generated in the entire area of the film. Then, the spacing of the generated points is measured, and if the spacing of the points is smaller than the predetermined value, the points are removed, and if the spacing is larger than the predetermined value, the points are added. Through this process, irregular and homogeneous reference points are generated as shown in FIG. 2.

(2) step 2

Next, a convex polygon including one reference point generated in step 1 is generated. This step can be performed using pre-spatial partitioning schemes to form a circular pattern. As such a preliminary spatial partitioning scheme, for example, but not limited to, a Voronoi diagram, a delaunay triangulation, and the like can be used.

Voronoi diagram refers to a method of dividing a plane by judging the point closest to an arbitrary point on a plane when several points are distributed in a plane. A polygon is formed by this plane division. It is called a noy polygon. In the Voronoi diagram, the number of Voronoi polygons is equal to the number of reference points distributed in the plane.

Delaunay triangulation is a method that finds the closest combination to an equilateral triangle by forming triangles connecting given points, and is widely applied in the finite element method. Based on trigonometry (Delaunay triangulation) through the combination of neighboring triangles can form a polygon closest to the circular shape.

Among the various spatial partitioning schemes, Voronoi diagrams are particularly desirable because they tend to suggest convex polygons to suggest the facet splitting scheme that most closely resembles the prototype to be placed under given conditions (positioning of points).

Meanwhile, in the present invention, after performing the above two steps as necessary, a step for correcting the shape of the generated convex polygon may be additionally performed.

Correction of the convex polygon may include generating an ellipse including vertices of the convex polygon generated in step 2, measuring aspect ratios of the generated ellipses, and when the aspect ratio of the measured ellipse exceeds 1: 2, Inserting the points inside the polygon, and forming a convex polygon pattern.

This is to prevent the problem that if the convex polygons formed through the second step is formed in a long shape in one direction, if the pattern is formed on the basis, the gap between the patterns becomes large. When the area of the void in which the pattern is not formed increases, light is transmitted without being diffused, and the diffusion efficiency is lowered.

(3) step 3

When a convex polygon is formed that divides the entire surface of the film in the same manner as described above, as shown in 4 of FIG. 1, a circle inscribed to the generated convex polygon is formed.

This is to form a spherical pattern, there is an advantage that the shape is easy to reproduce when the uneven pattern is formed into a spherical shape. In addition, since the spherical pattern has no directionality, it is advantageous in that the input light is diffused uniformly with respect to the azimuthal angle and the polar angle, regardless of which pattern the incident light enters.

(4) 4 steps

Next, considering the number of contacts of the circles formed in step 3, the circles whose contact number is less than a certain number correct the center and the radius. This step is to minimize the voids between the spherical patterns, the light is leaked when the voids are formed, the diffusion efficiency is reduced. Therefore, in the present invention, by minimizing the separation between the circles by correcting the circle of the contact number less than a certain number, it is possible to minimize the occurrence of voids.

In general, for circles with fewer than three contacts, it is desirable to perform the calibration.

On the other hand, the correction is preferably made by a method of changing the center and radius of the circle.

The mechanism of the correction will be described in more detail.

First, an arbitrary circle (C1) is determined and the number of contacts that the circle is in contact with another circle is obtained. If the number of contacts between the circle C1 and the neighboring circles is a fixed number, for example, less than three, select one arbitrary circle C3 of the neighbor not contacting the adjacent circle C2 among each neighboring circle. The center and radius of C1 having three contacts are obtained through a three-dimensional quadratic system of equations in which the center coordinates (x, y) of the three circles C1, C2, and C3 and the radius r of each circle are variables. . Then, when correcting the center and radius of C1 to the obtained value, if there is an overlap with neighboring circles C4 other than C2 and C3, if there is an overlap, the obtained solution is discarded and the other neighboring circle ( Find the circle with three contacts again, including C4). Here, overlap means that the distance between the centers of two circles is smaller than the sum of the radius of the two circles.

If the number of contacts of the new reference circle is less than three, using the circle corrected through the above process or the circle having three points as a contact point as the new reference circle C1 ', the process is repeated. Correct the center and radius of the. By repeating this process for all circles, the voids are minimized around the original circle.

Through the above process, a pattern of circles of irregular size and arrangement is formed. Therefore, when the pattern formed by the above method is transferred to a mold and a diffusion pattern is manufactured using the mold on which the pattern is transferred, a diffusion pattern having an irregular spherical pattern may be formed on the surface.

The pattern transfer may be performed by a method of engraving the irregular spherical pattern on the mold by irradiating a flat die plate with a carbon dioxide laser or an Nd-YAG laser. In addition, after irradiating an irregular spherical pattern designed by the above method on a photo-resist-coated substrate with a UV laser, it is developed to form a photoresist pattern, and the surface is heat treated to use surface tension. Induced to form a hemispherical shape, it can be made in a reflow (cooling) method. When the hemispherical photoresist pattern is formed through the above method, the metal layer may be deposited through a pole process to manufacture a mold.

In the method of transferring a pattern using a laser, since the height can be adjusted for each pattern, the height of each pattern may be formed to be the same as the radius to form a regular hemispherical pattern. It is also possible to form different heights.

On the other hand, in the case of the reflow method, since the height of the pattern that can be formed is limited, the radius of the smallest circle becomes the height of the overall hemispheres, and therefore, the radius in the case of forming the mold by the reflow method A mold having a non-semi-spherical pattern that is not equal in height to is formed.

By filling the mold with the irregular spherical pattern transferred to the resin in the same manner as above and separating the solid after the solidification, a diffusion film having an irregular spherical pattern can be manufactured.

In the case of the diffusion film of the present invention prepared by the above method, there is an advantage that can reproduce the same pattern while having an irregular surface structure that does not generate moiré. In addition, there is an advantage that the diffusion efficiency is excellent by minimizing the voids.

1 is a view for explaining the diffusion film design method of the present invention.

Claims (5)

A first step of generating irregular and homogeneous reference points on the entire surface of the film; A second step of forming a convex polygonal pattern having the reference points as one inside; Generating a circle inscribed to the convex polygons; And And a fourth step of correcting a center point and a radius in consideration of the number of contacts of the generated circles. The method of claim 1, The first step, Generating arbitrary points within the entire area of the film; And Measuring the spacing of the dots to remove the dots if the spacing is less than the predetermined value, and adding the dots if the spacing is greater than the predetermined value, the design of the diffusion film having a spherical pattern of irregular distribution Way. The method of claim 1, The convex polygonal pattern has a spherical pattern of irregular distribution is formed by a Voronoi diagram or trigonometric method. The method of claim 1, Creating an ellipse including the vertices of the convex polygon between the steps 2 and 3, and if the aspect ratio of the ellipse exceeds 1: 2, inserting a point inside the convex polygon, and reforming the convex polygon pattern The method of designing a diffusion film having a spherical pattern of irregular distribution further comprising the step. The method of claim 1, The fourth step is a method of designing a diffuser film having a spherical pattern of irregular distribution that corrects the center and radius of the circle of the contact number of the generated circle less than three.

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