JP2764559B2 - Lens array sheet, surface light source and transmissive display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens which exerts a uniform bright and excellent performance as an illuminating means for a backlight (back light source) of a translucent display such as a transmissive liquid crystal display device and an advertising board. The present invention relates to an array sheet, a surface light source using the same, and a transmissive display.

[0002]

2. Description of the Related Art In recent years, in a transmission type liquid crystal display device,
The demand for lighter weight and lower power consumption has been further increased, and various proposals have been made to effectively use light from the light source and to converge light in a specific direction in a surface light source that uniformly guides light only in necessary and sufficient directions. Have been. In these, a light source is usually arranged on a side surface of a light guide made of a plate material such as a transparent acrylic resin, and light from a light source incident from the side surface into the light guide is reflected by a reflective layer on the back surface of the light guide, thereby guiding the light. The light source light is emitted from the light emission surface on the upper surface of the light body and used. At this time, a diffusion sheet is arranged on the upper surface of the light guide to make the light uniform, and a lens array sheet that acts as a lens is provided to condense the emitted light only in a specific direction. A surface light source having a configuration to be arranged is used. Such a surface light source in which a light source is disposed on a side surface of a light guide is called an edge light type (or a side light type) surface light source because of its configuration. There is also a direct-type surface light source in which a light source is disposed immediately below a diffusion sheet or a lens array sheet. However, as a surface light source for a liquid crystal display element, its use is limited because it is thick.

In the above-mentioned surface light source, various devices have been proposed for effectively and efficiently using light from the light source, and a lens array sheet for condensing light as emitted light in a specific direction. Is one of them. As the lens arrangement sheet, for example, as shown in FIG. 10, a prism having a prism of a triangular prism as a unit lens and a large number of these arranged in a one-dimensional direction so that the ridge directions of the unit lenses are parallel to each other is known. Furthermore, it has been proposed to use two or more such lens array sheets so as to condense light more and increase luminance. For example, JP-A-5-203950,
JP-A-5-313156 and JP-A-5-313
Japanese Patent No. 164 proposes a configuration in which two lens array sheets each having a triangular prism as a unit lens are stacked.

[0004]

However, when two lens array sheets are stacked, the brightness is improved by the light-collecting effect, but there is a problem. That is, if the unit lens is arranged on the upper surface and the back surface is a lens array sheet with a smooth surface, the back surface of the upper lens array sheet and the vertex of the unit lens of the lower lens array sheet are microscopically adhered. I do. However, as a result, the optically transparent contact portion has a shape along the vertex portion of the lower unit lens, so that the lens vertex shape is visually observed. For example, if the unit lens is a triangular prism lens, the apex is a ridgeline, and many line segments are visually observed. Also, a Newton ring, which is a type of equal thickness interference fringes, may be generated as a concentric or concentric elliptical pattern on the entire surface of the surface light source due to a slight difference in the interval between the two lens array sheets. For this reason, the applicant of the present invention has proposed in Japanese Patent Application No. 5-323214 an attempt to form a fine unevenness by matting the back surface of the lens array sheet to prevent the lens array sheets from sticking to each other.

[0005] However, when the back surface of the lens array sheet is matted, the light is diffusely reflected there and acts like a diffusion sheet, condensing the light within a desired diffusion angle centered on a target direction. The brightness of the lens array sheet may be significantly reduced due to the deterioration of the function of the lens array sheet, or the blocking or absorption of light by matting (particularly in the case of incorporating light diffusing agent particles). Also, in the mat treatment, the height of the irregularities on the back of the lens array sheet is not completely uniform,
There is also a problem that a delicate difference in the interval between the two lens arrangement sheets is inevitable, and the same interference fringes are generated.

On the other hand, even when only one lens array sheet is used, if the rear surface of the lens array sheet is smooth,
When the lens array sheet is arranged on the light emitting surface of the light guide of the edge light type surface light source, the lens array sheet and the light emitting surface of the light guide are brought into close contact with each other to optically integrate the light guide. Light source light cannot be uniformly distributed over the entire surface due to total reflection of light on the body surface. In addition, even if spacers are provided at the four corners of the light guide or the lens array sheet to provide a gap between the light guide and the lens array sheet, the lens array sheet is bent and deformed, and the light guide and the lens array sheet are deformed. A subtle difference in the distance from the lens array sheet is inevitable, and uniform thickness interference fringes occur. In order to solve this problem, it is necessary to provide fine irregularities not less than the wavelength of the light from the light source on the entire back surface of the lens array sheet.
Japanese Patent Laid-Open No. 323319 and Japanese Unexamined Patent Application Publication No. Hei 6-324205 have proposed this. However, also in this case, such fine unevenness is a pattern of light isotropic diffusion such as grain, satin, etc.
Some of the light rays emitted from the light guide are dissipated outside the viewing angle as side lobe light, or are blocked or absorbed by light diffusing agent particles, resulting in reduced light-collecting action of the lens array sheet, and There is also a problem that energy is wasted and luminance is reduced.

In view of the above, the present invention solves the above-mentioned problems, makes effective use of the light energy of the light from the light source, maintains the light-collecting action, does not cause a decrease in luminance, and has the same thickness interference fringes and out-of-view angles. An object of the present invention is to provide a lens array sheet that does not dissipate unnecessary light to a light source, an edge light type surface light source using the same, and a bright transmissive display using the surface light source.

[0008]

Therefore, the lens array sheet of the present invention has a lens array in which unit lenses are arranged in one-dimensional or two-dimensional directions on the front side of the transparent base material, and has a lens array on the back side. The microprojections have a microprojection group randomly distributed two-dimensionally, and the microprojections have a polygonal prism or truncated pyramid shape, and the minimum diagonal length at the upper and lower bases is the maximum diagonal length at or above the wavelength of the light source light. Are assigned to the constituent elements of the cluster obtained at a percolation of the two-dimensional lattice below the critical percolation concentration Pc, and the small projection elements in the same cluster are fused. Further, in the lens array sheet, the occupation probability P less than the critical percolation concentration Pc is defined by using the lattice points of the two-dimensional lattice as the constituents of the cluster.
Then, a microprojection element is allocated to the lattice point, and a microprojection element obtained by fusing the microprojection elements in the same cluster is also used as the microprojection. Further, in the lens array sheet, the two-dimensional lattice is a square lattice, and the microprojection elements assigned to the lattice points are rectangular parallelepiped. Further, in the lens array sheet, an intersection line at which a horizontal plane of the lens array sheet intersects with a surface constituting the unit lens, and an intersection line at which the horizontal plane intersects with a side surface of the microprojection made of the rectangular solid microprojection element, The configuration may be non-parallel.

Further, in the surface light source of the present invention, at least
A light guide made of a light-transmitting flat plate, and a light source unit provided adjacent to at least one of the side end surfaces of the light guide,
A light reflecting layer provided on the back surface of the light guide, and one or two of the books formed by laminating a group of microprojections on the light emission surface of the light guide surface toward the light guide surface side; An edge light type surface light source constituted by the lens array sheet of the invention. Also, the lens array sheet is
It is also a configuration in which a plurality of lens array sheets are arranged, and the minute projections of the lower lens array sheet are stacked toward the light guide surface side.

In another surface light source of the present invention, in the configuration of the surface light source using one lens array sheet of the present invention, a light guide is further provided between the light guide and the lens array sheet of the present invention. In order from the light body side, it has a light diffusion sheet having unevenness on the front and back surfaces of the wavelength of light source light or more, and a lens array in which unit lenses are arranged in a one-dimensional or two-dimensional direction on the front side of the transparent base material. The side is a smooth surface without fine projections, and has a configuration in which a rear surface flat lens array sheet with the rear surface facing the light guide surface side is overlapped and arranged.

Further, a transmissive display of the present invention has a configuration in which the surface light source of the present invention is provided as a back light source of a translucent display.

Hereinafter, the lens array sheet of the present invention, an edge light type surface light source using the same, and a transmission type display using the surface light source as a backlight will be described in detail with reference to the drawings.

FIG. 1 is a perspective view showing one embodiment of a lens array sheet of the present invention. In the lens array sheet 1 of the present invention shown in FIG. 1, a triangular prism is used as a unit lens 41 on one surface of a transparent base sheet 31, and the unit lenses are adjacent to each other so that their ridge directions are parallel to each other. It has a lens array 4 arranged in a large number in the direction, and the other surface (in FIG. 1, the upper side is so as to be easy to see fine projections), the cross section is polygonal and the shape is random by a special method. A different polygonal prism as the minute projection 21
The microprojections 21 are provided with a plurality of microprojections 21 arranged on the entire surface in a random two-dimensional distribution.

The lens array sheet of the present invention is characterized by a group of minute projections provided on the surface opposite to the lens array.
The group of microprojections is composed of a number of microprojections, each of which has a separate shape and a different shape. Further, the microprojections are polygonal prisms or truncated pyramids, and the minimum diagonal length at each of the upper and lower bases is equal to or greater than the wavelength of the light source light, and the longest diagonal length is equal to or less than 500 μm. Are obtained by fusing one or more microprojections. Here, the term "fusion" means, in a simple manner, connecting and merging adjacent microprojections, and in the present invention, a method of obtaining microprojections from the microprojections by the fusion is described in the present invention. Use a special method. That is, a minute projection is created from a minute projection element by the percolation theory. That is, the microprojection elements are arranged at lattice points of a two-dimensional lattice such as a square lattice with a certain probability (this is called an occupation probability P), and the microprojection elements arranged at adjacent lattice points are connected to each other. As a result, one obtained by connecting a plurality of microprojection elements (this is called a cluster in percolation theory) is defined as a microprojection. When there is no adjacent minute projection element, one minute projection element becomes a minute projection as it is. Further, as will be described later, the placement target of the minute projections is not limited to the lattice points.

Therefore, a method for obtaining clusters (microprojections) by the percolation theory will be described.

First, the percolation theory will be outlined. For example, J. Feder, translation by Mitsugu Matsushita et al., "Fractal", published by Keigaku Shuppan, published May 31, 1991,
Chapter 7, "Infiltration," explains that there are two completely different types of randomness. One of them is the randomness due to particles moving randomly in a medium, which is well known as the so-called diffusion phenomenon. The other is the randomness shown in the behavior of particles moving in the medium based on the randomness of the medium itself. The latter randomness behaved like coffee in a percolator, and was named the percolation process by Hammersley. Specifically, there is the behavior of water penetration into cracks and cracks in rock. Also, Motoo Hori, Flame Propagation and Percolation Model, "Mathematical Science", June 1974, pp. 63-70, describes the process in which a fire spreads in an urban fire using this model.

The concept of percolation is described in J. In his book, this is explained by two-dimensional penetration on a square lattice. It is assumed that each grid point constituting the square grid is occupied by something (in the case of the present invention, a microprojection element) at an occupation probability P at random. For example, consider that "something" is a small hole in a rock. Then, it is considered that adjacent small holes are connected by a pipe. (The stoma is called a site, and the aggregate of connected sites is called a cluster.
The connecting pipe is called a bond. Thus, water injected into a stoma penetrates only to the stoma connected by a tube. That is, the water injected into the pores that make up a certain cluster stays in the cluster and does not spread any further. In addition, the number of sites forming one cluster is referred to as a cluster size or a cluster size. However, when the occupation probability P exceeds a certain critical value, an infinitely large cluster is generated in a cluster composed of aggregates of pores, and water injected into the pores of the cluster finally traverses the entire lattice. Penetrate as if to do. Such a cluster is called a permeation cluster, and the occupancy probability at which a permeation cluster first occurs is called a critical percolation concentration Pc (also called a critical probability). Incidentally, in a square lattice, PcＰ0.593.

In the above example, it is considered that grid points are occupied at a certain probability, and when the occupied grid points are adjacent to each other, they are all connected by pipes. What is expressed only by probability is called site percolation. On the other hand, what is expressed by the probability that the connecting pipes are open rather than closed is called bond percolation. In addition, the probability of the site, and (independent of that probability)
There may also be mixed percolation represented by both bond probabilities. In the paper by Mr. Hori Motoo, the propagation of the flame is examined by each of these percolation models.As an example of bond percolation, the phenomenon that a fire that occurred in a certain house in a dense wooden house area spreads to the neighbors,
It is explained that it is governed by the bond probability. Also,
The value of the critical percolation concentration Pc is that of site percolation in a square lattice, and the value of Pc in bond percolation is different from 1/2.

Based on the outline of clusters in percolation described above, the relationship between the microprojections and the microprojections of the present invention and the clusters will be described. In the site percolation of the above-mentioned square lattice, when looking at the lattice points of the square lattice, conversely from the obtained slater, a cluster is formed (that is, located inside the cluster).
There are small holes at the lattice points, and no small holes at the lattice points that do not constitute the cluster. Therefore, in the present invention,
The lattice points that make up the cluster (that is, are located inside the cluster) will be referred to as cluster constituents. Therefore, a lattice point where no pore exists, that is, a lattice point outside the cluster is not called a constituent. In other words, a grid point is a candidate location to which something can be assigned with a certain probability, and a constituent is a candidate location to which something should always be assigned.

By the way, in site percolation, a lattice point is a site, and a cluster formed by connecting adjacent “sites occupied by a certain object” with a bond therebetween by a bond. However, similar to this, bond percolation and mixed percolation, but in bond percolation,
"Bond occupied by something" more adjacent to the site
What can be connected to each other at the site is a cluster. In addition, in the case of mixed percolation, when considering site percolation, if all bonds are not connected and they are connected with a certain probability, it is difficult to form a permeation cluster, but similarly, clusters It will be easy to understand what is obtained.

Therefore, in bond percolation, what constitutes a cluster is a specific (for example, occupied) bond, and what constitutes a cluster in mixed percolation is a specific site and bond. Also, clusters are not limited to site percolation. Therefore, in the present invention, elements constituting a cluster obtained in any case in a site, a bond, or a mixed percolation are defined as constituents, regardless of whether they are a site, a bond, or both, in the present invention. .

However, in the following description, a cluster based on site percolation will be described as an example. That is, in the present invention, microprojections are obtained by connecting a plurality of microprojections, and in this regard, site percolation corresponding to an operation of arranging microprojections at lattice points at a certain probability is as follows. This is because it is easy to understand even intuitively. Furthermore, theoretically, it has been proved that the bond percolation problem is equivalent to the site percolation problem of another grid having a bond point at the center of the bond (this is called a coated grid) (Takashi Otagaki) , "Science of Percolation", published by Shokabo, June 2, 1993
This is from the 1st issue of the 0th issue.

First, a square lattice is typical as a two-dimensional lattice from which lattice points are based, but the present invention is not limited to this. In general, a two-dimensional lattice is a regular lattice in which unit cells are periodically arranged two-dimensionally adjacent to each other. Such a two-dimensional lattice includes a square lattice, a triangular lattice, a kagome lattice shown in FIG. 23A, a hexagonal lattice (honeycomb) shown in FIG. 23B, a Penrose lattice, and the like. Further, the square lattice is a square unit lattice in which the lattice length in the X-axis direction is equal to the lattice length in the Y-axis direction in the orthogonal coordinate system, but the lattice lengths of the unit lattices in the X-axis and Y-axis directions are not equal. Alternatively, a parallelogram lattice or the like may be used as an oblique coordinate system in which the coordinate axes are not orthogonal. Although these are all regular lattices, they may be irregularly shaped mesh-like lattices. To enumerate the critical percolation concentration Pc (of site percolation) for the main two-dimensional lattice, the honeycomb lattice lattice has a .0.
6962, 0.592745 for the square lattice, 0.65271 for the Kagome lattice, 0.5 for the triangular lattice, and 0.584 for the Penrose lattice. The shape of the cluster is random but generally fractal.

Next, the microprojection elements that occupy the lattice points with a certain probability are composed of polygonal prisms or truncated pyramids, and the shape of the bottom surface is a polygon such as a triangle, a quadrangle or a hexagon. Above all, squares include rectangles, squares, diamonds, etc.
A rectangular prism having a rectangular parallelepiped shape, which is a polygonal prism, in which two opposing sides forming a side surface of the columnar body are parallel and a rectangular or square shape in which adjacent side surfaces are perpendicular to each other, makes it easy to manufacture minute projections formed of clusters. In some respects, moiré is less likely to occur. Note that the side surface of the microprojection element, which can also be the side surface of the microprojection, is not limited to the vertical side, and may be a truncated pyramid made of a slope from the viewpoint of manufacturing problems or its easiness. In addition, the shape of the bottom surface of these polygonal prisms or truncated pyramids, together with the lattice shape of the two-dimensional lattice to be percolated later, if the two-dimensional lattice consists of a rectangular quadrilateral such as a square lattice, a rectangular quadrilateral, A triangular lattice is usually a triangle, and a hexagonal lattice is a hexagon, etc. from the point of symmetry, but is not necessarily limited to this.

The smallest x-slutter is composed of one independent constituent element, and one of the constituent elements to which (one) micro-projection element is assigned becomes one minimum-small projection.

FIG. 2 shows a rectangular parallelepiped as an example of the shape of the microprojection element 24. The relationship between the height H, the bases a and b, and the relationship between the three dimensions is a = b =
H (cube), a = b ≠ H, a ≠ b = H, a = H ≠ b,
a ≠ b ≠ H ≠ a. Incidentally, the diagonal lines d1 and d2 in the upper base have the same length in the cube and are also present in the lower base (not shown). It is preferable that the size of the microprojection element be within a certain specific range in terms of the height H and the diagonal d. In addition, the size of each microprojection element that is applied to a plurality of constituent elements (lattice points in the description here) is usually the same.

First, the height H of the microprojections is also the height H of the microprojections formed by the microprojections, as shown in FIG.
As shown in the example, when mounting a lens array sheet,
It serves as a spacer to another lens array sheet or the light emitting surface of the light guide. When the height H of all the microprojections distributed on the entire surface of the lens array sheet is the same, the same height does not bend when the lens array sheet is mounted, and a uniform interval can be secured. It is preferable that the heights H of all the microprojection elements arranged at the same position are the same. Therefore, usually, the heights H of the microprojections arranged at the lattice points are of the same size.

The size of the microprojection element can be determined by comparing with the wavelength of the light source light and with the size of the object that can be visually recognized.
There is an optimal range. From this point, the size of the microprojection element is evaluated by the height H and the dimensions of the sides a and b, which are more substantial than the dimensions of the diagonal line d. Among the diagonals in the upper bottom surface and the diagonal lines in the lower bottom surface (in the case of a truncated pyramid, the diagonals of the upper and lower bases are not equal), the smallest diagonal and the longest diagonal are evaluated. It is preferable that the height H and the minimum diagonal line d be equal to or larger than the wavelength of the light source light, and the height H and the maximum diagonal line d be equal to or smaller than 500 μm, more preferably equal to or smaller than 125 μm. When there is a distribution in the spectrum of the light source light, the wavelength is set to be equal to or longer than the maximum wavelength of the visible light spectrum. If the wavelength is less than the wavelength of light, it is not possible to effectively prevent the occurrence of interference fringes of equal thickness or the integration of the optical contact between the lens array sheet and the light guide. There is no point in increasing the dimensions, for example, the sheet may be easily deformed by bending, moire fringes may be easily generated between the sheet and the pixels of the display body, or manufacturing may be difficult.

The reason why the height H of the minute projection 21 (or the height H of the minute projection element 24) should be equal to or longer than the wavelength of the light source light will be described in detail below. First, the case where the lens array sheet is placed on a plate-shaped light guide and the back surface of the lens array sheet and the light guide surface are in contact will be considered. As shown in FIG.
Incident light L ₁ traveling from inside the light guide 51 toward the air
Reaches the light guide surface 55 which is the interface between the light guide 51 and air, if the incident angle θ is larger than the critical angle θc, total reflection occurs, and the energy of the incident light L ₁ is all reflected light L _1R
Thus, the incident light does not enter the air. However, looking at this phenomenon microscopically, the electromagnetic field of the incident light permeates the air from the light guide surface 55 at a distance of about the wavelength λ of the light source light due to the tunnel effect. The intensity of the permeated tunnel electromagnetic field L _1V is attenuated by an exponential function of the penetration distance, and when it reaches a wavelength of about λ, it is all returned to the light guide 51 side. Therefore, when viewed macroscopically, all light energy is reflected by the light guide surface 55.

Therefore, as shown in FIG. 21, when the distance ΔX between the lens array sheet 1 and the light guide surface 55 approaches a distance (ΔX <λ) smaller than the wavelength of the light from the light source, the light is not completely attenuated. The tunnel electromagnetic field L _1V becomes a traveling wave (output light) L _1T again inside the lens array sheet 1, and the light is transmitted through the lens array sheet 1. Therefore, when the height H of the minute projections 21 satisfies H <λ, total reflection of light from the light guide does not occur over the entire surface of the light guide surface 55. Partial result, for example, as the incident light L ₃ in FIG. 22, the angle of incidence of the light source near to incidence below the critical angle, but is taken out as output light L _3T, or more away to some extent from the light source incident light to, for example, since all the light, such as L ₂ in Figure 22 is the angle of incidence larger than the critical angle, not the output light will be totally reflected in the light guide surface 55. Therefore, the luminance distribution of the output light from the surface of the light guide is undesirably bright only in the vicinity of the light source and dark in other areas.

On the other hand, when the height H of the minute projections 21 satisfies H ≧ λ (Equation 1), even in a region away from the light source, the portion where the minute projections 21 and the light guide 51 are in contact is located. As shown by L ₁ in FIG. 22, the incident light L ₁ is not totally reflected but some of the light becomes the transmitted light L _1T to obtain the output light. Therefore, even in a region away from the light source, a sufficient amount of output light from the surface of the light guide is ensured. The light incident on a portion between each microprojection 21, for example as the L ₂ in FIG. 22, because of the wavelength or more gaps 9 of the light on the light guide surface, all in the light guide surface 55 Is reflected. Thus, L ₂ is not output in situ, is utilized as a more allocated to distant from the light source where the output light.

As can be seen from the above consideration, the minute projections 2
By placing a lens array sheet whose height H satisfies H ≧ λ such that the minute projections face the light guide surface,
It is possible to obtain output light having a uniform luminance distribution over the entire area of the light guide surface.

Next, the case where two lens array sheets are used in a superposed state will be considered. As proposed in Japanese Patent Application No. 5-323214 filed by the same applicant as the present invention, 2
The conditions for eliminating the equal-thickness interference fringes between the lens array sheets are as follows: the height H of the minute projections 21, the wavelength λ of the light from the light source, and the reflection from the observer on the light reflecting surface (front surface, back surface, etc.) of the lens array sheet. Assuming that the viewing angle of the illumination light source (sunlight from the window, light from the ceiling lamp, etc.) from the outside viewed from the outside is φ, H ≧ λ / (2Δφ ² ) [Equation 2]. However, under the normal use condition of the lens array sheet, [Equation 2] is satisfied if [Equation 1] is satisfied. That is, λ / (2Δφ ² ) ≧ λ is satisfied. Now, when the specific numerical values of [Equation 2] are obtained, it is assumed that the surface of the lens array sheet is observed using white light of 0.38 μm ≦ λ ≦ 0.78 μm as an external light source. Is usually 100 ° ≦ Δφ ≦ 120 °, ie, 0.1%, due to indoor lighting or natural light from windows.
When 75 [rad] ≦ [Delta] [phi ≦ 2.094 (rad), from [Formula 2], has the most large right-hand side of [Formula 2], delta phi
= 0.175 [rad], and λ _MAX = 0.78 [μ
m] can be obtained as follows: H ≧ 12.5 [μm]> λ _MAX = 0.78 [μm]

Next, the size of the diagonal line d of the minute projection element will be described. By the way, the smallest one of the micro projections 21 was one micro projection element. Therefore, the size of the bottom surface (upper bottom and lower bottom) of the microprojection element depends on the height H of the light source light, although it depends on the height H in order to secure the minimum strength as a spacer. Is the minimum wavelength of
Preferably, it needs to be 1 μm or more. The diagonal d is 1
When the thickness exceeds 25 μm, particularly 500 μm, the minute projections or minute projection groups become visible, and when used in a liquid crystal display element, moire fringes with the pixel tend to occur, which is not preferable.

Furthermore, since microprojections are generated by fusing and linking a plurality of microprojections, the regularity of the two-dimensional lattice used, the number of microprojections to be fused, and the complexity of the shape of the microprojections Although it depends on the method of fusion and the complexity of the shape of the microprojections after fusion, if the linear portion of the side surface is still extremely large due to the size of the microprojections after fusion, it may become visible, It is preferable that the linear portion is a minute projection having a size of about 1000 μm or less.
However, the shape of a microprojection (which is a cluster formed by merging and connecting microprojections) is random. Because it does not occur in the microprojections, it is less noticeable, and by appropriately selecting the two-dimensional lattice, the occupancy probability, the shape of the microprojections and the manner of fusion, the microprojections having the desired shape can be obtained from the microprojections without any problem. Obtainable. It is not necessary that all the microprojections assigned to the lattice points have the same shape and the same size, and even if they are changed (for example, microprojections having the same shape but three kinds of different sizes) are used, the regular With the use of the two-dimensional lattice, the generation of minute projections having long and long side linear portions can be suppressed to a lower rate. Further, as an amount for evaluating the size of the planar spread of the cluster, there is an average rotation radius Rs defined by the following [Equation 3]. Here, r ₀ is the position vector of the center of gravity of the cluster, r _i is the position vector of each site in the cluster, and s is the size of the cluster. Rs is the root mean square of the distance from the center of gravity of the cluster to each site within the cluster. Rs is d ≦ Rs
≦ 3 [mm] is preferred. The lower limit is self-evident, but the upper limit is determined by exceeding this limit because visual effects due to optical contact, that is, non-uniformity of equal thickness interference fringes and in-plane distribution of output luminance cannot be ignored.

[0036]

(Equation 1)

Next, a specific example of the generation of microprojections by percolation will be described with reference to the drawings, showing the process of generating microprojections from rectangular microprojections having a square bottom.
FIG. 5A shows a grid point of a square grid of 25 × 25.
This shows a state in which the microprojection elements 24 are assigned to the lattice points (constituent elements) selected with the occupation probability P = 0.4 (black indicates the microprojection elements in the drawing). The size of the microprojections (on the bottom surface) is 5/8 of the unit cell length of the square lattice. Then, the microprojections adjacent to each other in the vertical or horizontal direction (connected by bonds) are fused by filling the moat between them, and furthermore, the four microprojections are adjacent to each other so as to form a nearly twice as large square. In the portion where the projection is made, the portion surrounded by the microprojection element is also filled. By this operation, FIG.
(B) As shown in FIG.
Is obtained.

Here, the occupation probability P is preferably less than the critical percolation concentration Pc. When P ≧ Pc, a permeation cluster is generated as shown in FIG. The figure shows the case where P = 0.60 under the same conditions as in FIG. 5, but a permeation cluster (microprojection) 25 crossing the entire lattice from the upper side to the lower side is observed. In the present invention, when the occupancy probability P becomes equal to or higher than the critical percolation concentration Pc,
The size of the cluster is infinite (in an actual finite-size grid, of course, it is the size of a finite cluster, but in this case it is a cluster connected from one end of the grid to the other)
In addition to making the cluster more visible,
Optical contact between the lens array sheet and the light guide plate, or between the lens array sheets (contact at a gap smaller than the wavelength of the light source light)
Area cannot be ignored. Therefore, the interference fringes having the same thickness are visually observed, and the uniformity of the in-plane distribution of the output luminance from the light guide plate is undesirably reduced. Therefore, in the present invention, the occupation probability P is selected so that P <Pc. The occupancy probability P
The lower limit of で な い needs a finite value that is not at least zero. However, in order to fulfill the function as a spacer distributed over the entire surface of the lens array sheet, it depends on the size of the microprojection element and the like. It is about. More specifically, the value of the occupation probability P is determined by the size of the microprojection element (generally represented by the diagonal length of the bottom surface or the lengths a and b of the base in the case of a cuboid projection element), lattice constant, It is determined comprehensively in consideration of the flexibility of the lens array sheet. For example, FIG.
5 to 29, using a square lattice with a lattice constant of 100 μm, and assuming that one side of the microprojection element = lattice constant, the occupancy probabilities P = 0.2, 0.3, 0.4, 0.5, 0.6 in order. In the following five examples, computer simulations using uniform random numbers are performed. However, in FIGS. 25 to 29,
For convenience of display, only 25 × 25 grid points of the entire grid are shown. Of these, for 0.2 ≦ P ≦ 0.5, the maximum value of the average turning radius Rs Rs ^max = 110 μm
m to 630 μm, and the area ratio Sr of the protrusions is 18 to 54%. This Rs ^max falls within the preferred range described above, and
Sr falls within a preferred range described below, and is a practically preferred range. This will be shown in the embodiments described later.

Next, FIG. 6 shows an example of a method of fusing the microprojection elements. FIG. 6A shows a small projection element 2 having a square bottom surface and a size smaller than the unit cell length of a square lattice, which is assigned to a lattice point 8 (ie, a constituent element) selected at a certain occupation probability P.
4 shows the case where the two are adjacent to each other. In FIG. 6B, the shape of the connecting portion 26 between adjacent microprojections is such that the side surface of the obtained microprojection 21 is smooth and linear. By the way, FIG. 5B shows the manner of this fusion. FIG. 6C shows a fusion method in which the width of the connection portion 26 is smaller than that of the minute projection. In this way, even when the microprojections are continuously fused, the side surface of the microprojections can be prevented from becoming linearly long, and there is an advantage that moire fringes are less likely to occur as compared with FIG. However, FIG.
The method (2) has a difficulty in that the shape becomes complicated and higher processing accuracy is required as compared with FIG. 6 (b).

The two-dimensional distribution of the minute projections 21 on the lens array sheet surface is preferably a random distribution, but in fact, the present invention has randomness based on the percolation theory. (This can be understood by taking the center of gravity of the area element on the bottom surface of each microprojection as a representative value of its coordinates and seeing its distribution.) If the microprojections are periodically arranged, the microprojections and the lens Moire fringes appear because the unit lenses on the opposite surface of the array sheet (in most cases, they are periodically arrayed) always overlap at a certain period. When used as a backlight of a color liquid crystal display element in addition to the arrangement cycle of the unit lenses constituting such a lens arrangement, moire fringes tend to appear due to interference with the arrangement cycle of the pixels of the display element. Therefore, the occurrence of moiré fringes can be prevented by introducing randomness into the arrangement of the minute projections and making them non-periodic.

However, even if the arrangement of the microprojections 21 is randomized, if the shapes of the microprojections constituting the microprojections are the same and the orientations are uniform, the moire fringes are of the same type (for example, If the base is trapezoidal, the sides of the microprojections generated from each side of the trapezoid are all in the same direction, so these small sides in the same direction are aggregated, as if a large virtual It forms a side surface. In addition, even if the microprojections are randomly arranged, the virtual side uses a regular lattice (for example, a square lattice) having periodicity in the two-dimensional lattice used in the microprojection generation process and arranges the microprojections at lattice points. If all the elements have the same shape and size, periodicity also occurs. Then, the lower side surface interferes with the surface of the unit lens constituting the lens array, and moire fringes may be generated. Therefore, it is preferable that the surface forming the unit lens and the side surface of the minute projection have a certain relationship.

FIG. 4 is an explanatory diagram for preventing the occurrence of moire fringes. For example, let us consider a case where the lens array of the lens array sheet 1 is composed of unit lenses 41 of a triangular prism lens as shown in FIG. The exit surface of the lens array sheet 1 is a surface parallel to the XY plane, and is defined as a horizontal plane. The normal direction perpendicular to the light exit surface is the Z-axis direction (not shown). The surface forming the unit lens 41 is a slope 42 forming a mountain and a valley. An intersection line intersecting this surface (slope surface) with a horizontal plane is a line parallel to the X axis (the X axis is parallel to the intersection line). The coordinate axes are taken so that Strictly speaking, the slope is a finite surface, and there are many horizontal planes depending on how to take the Z-axis coordinates. The slope and the horizontal plane do not intersect depending on conditions, but the line of intersection here is the plane (slope) Is a line extending from the horizontal plane. Of course, in the case of a triangular prism unit lens, if it is arranged in a one-dimensional direction, there is only one type of intersection, but if another type of unit lens such as a quadrangular pyramid is arranged in a two-dimensional direction, There may be two or more types of intersecting lines derived from the surface constituting the unit lens, and the intersecting lines may not be orthogonal.

Next, FIG. 4B shows one intersection line derived from the minute projection group 2 with respect to the XY coordinate axis with respect to the intersection line derived from the unit lens 41 of the triangular prism lens. Is the X 'axis, and the orthogonal X'-Y' coordinate axes are superimposed. The side surfaces of each microprojection 21 are all oriented in the same direction, and there are two types of lines of intersection between the side surfaces and the horizontal plane of the lens array sheet, which are orthogonal to each other, parallel to the X 'axis and parallel to the Y' axis. Line of intersection. The X 'axis and the previous X axis form an angle α.

If the angle α between the X-axis and the X'-axis is zero, they become parallel and moiré fringes easily occur. However, moiré fringes can be prevented by arranging both the intersection line derived from the unit lens and the intersection line derived from the minute projections by more than 5 °. That is, if the intersection line derived from the minute projections gives a rectangular coordinate system, if the angle α is clockwise (clockwise) in the range of 5 to 85 °, more preferably in the range of 10 to 80 °, moire The generation of fringes can be effectively prevented. The angle α is -5 in a counterclockwise direction.
The range may be from -85 to -85, more preferably from -10 to -80. When the angle exceeds 85 °, the angle of the intersection line derived from the side surface of interest further increases, but the relationship with the adjacent side surface (which forms 90 ° with respect to the side surface) becomes
The relationship is close to a parallel relationship, and moire fringes are easily generated in relation to an adjacent side surface. As described above, the generation of moiré fringes can be prevented if the bottom surface providing the orthogonal coordinate system is separated from the parallel by more than 5 ° with respect to the side surfaces of the minute projections made of rectangular minute projection elements.

The microprojection element is made of, for example, a rectangular parallelepiped, and the line of intersection between the noted side surface of each rectangular parallelepiped and the horizontal plane of the lens array sheet, and the line of intersection between the unit lens surface and the horizontal line are as described above. When the angle is defined at a certain angle exceeding 5 ° as described above, it is not necessary to align all the directions of all the microprojection elements (in this case, rectangular parallelepipeds) allocated to the constituent elements. For example, even if 1% of all microprojection elements are horizontal, if they are not concentrated in adjacent parts and adjacent lattice elements, a parallel relationship that causes moire fringes is defined. This is because it does not have enough strength. In this sense, in claim 4 of the present invention, the meaning of “each rectangular parallelepiped” does not necessarily mean that the line of intersection derived from the side surface of each rectangular parallelepiped and the line of intersection derived from the unit lens are not parallel to each other. It is not limited that all the rectangular parallelepipeds arranged in the constituents have a non-parallel relationship, but also includes a meaning that even if some of the arranged rectangular parallelepipeds have a parallel relationship, there is a large number of non-parallel relationships. .

Although it has already been described that the microprojection element of the present invention may be a polygonal prism in addition to a rectangular parallelepiped, when the rectangular parallelepipeds targeted in the above description are arranged in the same orientation on the constituent elements, the side faces are mutually opposite. 90 ° because it forms 90 °
A similar situation occurs each time it rotates. However, in the case of a rectangular parallelepiped, the opposing side surfaces are parallel to each other, and therefore, in preventing the occurrence of moiré fringes, only two types of intersecting lines that are orthogonal to each other are considered. However, in the case of a polygonal prism other than a rectangular parallelepiped, for example, a triangular prism, there are three types of intersection lines to be considered, and in the case of a pentagonal prism, there are five types of intersection lines, all of which are more than in the case of a rectangular parallelepiped. Therefore, the conditions under which moiré fringes occur are increased, and the degree of freedom in design is reduced. Of course, even in the case of a square prism, adjacent side surfaces are not right angles, and in a free square prism, there are four types of intersection lines to consider, and in this regard, the opposite side surfaces are parallel, and the bottom surface is a parallelogram or Even with a square prism having a rhombus shape, the occurrence of moire fringes can be prevented as well as a rectangular parallelepiped. However, from the viewpoint of ease of manufacture, a rectangular parallelepiped is superior to a quadratic prism composed of a parallelogram or a rhombus. In addition, as a case where the intersection line derived from the side surface does not form a straight line, there is an n prism having n infinite, that is, a cylinder having a curved side surface, an elliptic cylinder, and the like. For example, when a microprojection, and thus an original film for forming a microprojection group is formed by a parallel scanning method such as a scanner, the projection is so small that a circular shape that forms a side surface that is not parallel or perpendicular to the scanning line. The contours of the cylinder are indented, and the smooth sides of the original cylinder cannot be formed.

The moiré fringes generated due to the relationship between each of the minute projections, the constituent surface, and the constituent surface of the unit lens are arranged in the same direction when assigning the minute protrusions to the constituents. This is because all the side surfaces formed by the minute projections define a recognizable intersection line, and a relationship occurs between the intersection line and an intersection line derived from the surface formed by the unit lens. However, even if all of the microprojections are of the same shape, if they are arranged in a random manner in arrangement to the constituents, that is, if they are rotated at random, the intersection line obtained from the surface formed by the side surface of each microprojection is , Each having an arbitrary angle dispersed therein, there is no intersection defined at a specific angle, and even in this case, the occurrence of moire fringes can be prevented. In this respect, a cylinder, an elliptical cylinder and the like are excellent, but there is a difficulty in manufacturing a side surface having a smooth curved surface as described above.

Further, the distribution density of the minute projections is such that the lens array sheet is bent so that no interference fringes of equal thickness can be formed, and even if the lens array sheet has a certain degree of rigidity, the lower side has a lower density. The distance is appropriately set so that a uniform interval can be secured between the optical member and the lens array sheet, and a slight difference in the interval does not allow uniform interference fringes to be formed. Therefore, the lattice size of the two-dimensional lattice may be determined from the viewpoint of the distribution density. The distribution density when the cross-sectional area of the microprojections is assumed to be zero, that is, the distribution density in terms of the number of microprojections, particularly when two lens array sheets are used in an overlapping manner, It is preferable that the average distance t between the adjacent protrusions of the minute protrusions is not more than twice the repetition period p of the unit lens on the surface of the lower lens array sheet, that is, t <2p. By designing in this manner, the supporting contact between the microlenses 21 on the back surface of the upper lens and the unit lens 41 on the surface of the lower lens array sheet that are in contact with each other regardless of the cross-sectional area of the microprojection element bends, It is possible to prevent the interval between the upper and lower lens array sheets from becoming uneven, thereby producing interference fringes of equal thickness, and the interval between the upper and lower lens array sheets to be less than the wavelength of the light source light. The average distance t is more preferably t <0.5p. However, since the microprojections have a finite cross-sectional area and the microprojections are connected to each other, t is
Even if it is larger than 0.5p, this prevention effect is sufficient.

On the other hand, when the cross-sectional area of the fine projections is evaluated as being finite, the distribution density that can prevent the interference fringes having the same thickness even when the lens array sheet is bent is as follows.
Ratio Sr (= Sp /) of the total sum Sp of the cross-sectional areas of the protrusions to the total area St where the light guide 51 and the light guide 51 face each other.
(St × 100), and generally about 0.01 to 60% is preferable. Although it is preferable that the function as a spacer functions at a minimum, it is necessary to some extent in terms of bending of the lens array sheet. It is also necessary to some extent to make the surface distribution uniform. Especially when the lens array sheet is 5
In the case of the same degree of flexibility as a biaxially stretched polyethylene terephthalate sheet of 0 to 100 μm, Sr = 20 to 60
% Is good.

In order to consider factors related to the surface distribution of luminance, an explanation will be given using an area ratio R which is inversely related to the above-mentioned area ratio Sr. The small protrusions 21 do not adhere to the surface of the light guide 51, and the total area Sa of the portions of the gaps 9 having a wavelength or more is the total area where the lens array sheet 1 and the light guide 51 face each other. Area ratio R as a ratio to St
[%] Is represented by [Equation 4]. R = Sa / St × 100 [Equation 4] Accordingly, the area ratio R is equal to the area ratio Sr and R + Sr = 1.
There is a relationship of 00. The area ratio R is determined by the required uniformity of brightness in a plane, the efficiency of light energy use, the dimensions of the light guide, and the like. Usually, the area ratio R is 80%.
More preferably, it is necessary to be 90% or more. The reason for this is that, as shown in FIG. 21, when the light guide surface 55 having a smooth surface roughness equal to or less than the wavelength of light is brought into close contact with the front surface (back surface) of the lens array sheet 1, as shown in FIG. Most of the input light incident on the light guide 51 from the light source 52 is emitted without being totally reflected in a region extending from the side end on the light source side to the distance y (the critical angle is formed on the surface of the light guide). Even if the light is incident as described above, the light is not totally reflected at that portion and enters the unit lens). Therefore, at a position farther than y, the brightness is sharply reduced and darkened. The percentage of the length y of the light emitting portion with respect to the total length Y in the light propagation direction of the light guide 51 is 10 to 20% when actually measured. Accordingly, in order to evenly distribute the amount of light energy incident on the light guide from the light source over the entire length Y, most of the light, that is, about 100% of light is emitted in the region of the length y of the light guide surface 55. Of the incident light coming to the area portion of the length y.
It is necessary to transmit and emit 0 to 20%, and totally reflect the remaining 90 to 80% of light. Here, R is approximately 80 to 90% (Sr = 10%) because approximately (total reflected light amount / total incident light amount) ≒ Sa / St = R.
２０20%). And since the approximation can be similarly performed at a place farther than y, the point that R is required to be 80 to 90% can be applied over the entire length. However, R is 100%
If (Sr is too close to 0%), the distance between the minute projection groups cannot be maintained to be equal to or more than the wavelength of light due to the bending of the lens array sheet as described above, which is not preferable. Therefore, the upper limit of R is 99.99% or less (Sr ≧ 0.01%)
It is good to

The randomization process based on the percolation theory may be performed by a computer, and the result may be printed on a film master for plate making. Alternatively, a group of microprojections randomized for a limited area may be used as a unit to repeatedly form a microprojection group having a finally required area by repeating the process from left to right.

By providing the specific minute projections as described above on one surface of the lens array sheet, light rays emitted out of the viewing angle are increased and the luminance is not reduced, and uniform thickness interference fringes and moiré fringes are prevented. Further, an excellent lens array sheet capable of distributing output light with a uniform surface distribution over the entire surface of the light guide can be provided.

FIG. 9 shows a lens array sheet 1 according to the present invention.
As shown in FIG. 9A and FIG. 9B, a three-layer structure in which a microprojection group 2 including a large number of microprojections 21 is provided on one surface of a flat transparent base material 3 and a lens array 4 is provided on the other surface. Or a two-layer structure in which the lens array 4 and the transparent substrate 3 are integrated with each other and provided with the microprojection group 2 as shown in FIG.
The lens arrangement 4, the transparent substrate 3, and the microprojection group 2 shown in FIG. 7 may be integrated into a single layer. In such an integrated lens array sheet, the portion of the transparent substrate is not always necessary, and there may be one having a minute projection group on the back surface of the lens array, and it is considered that these integrated ones are the transparent substrate. You can also. In FIG. 9B, the microprojection base 32, which is transparent and integrated with the microprojection group 2, has a smooth surface (the rear surface side as the lens array sheet) except for the microprojections 21. The entire surface of one side of the substrate 3 is covered. This is because such a configuration may form the microprojection base 32 at the same time when the microprojection group is formed on the transparent substrate 3. In this case, the microprojection base 32 can be considered as a part of the transparent substrate 3.

The transparent substrate, the minute projections, and the lens array are formed from a transparent material. The transparency of such a material may be colored transparent or translucent depending on the application. The minute projections may be opaque to the extent that they are not visible because the size of the minute projections is very small, but it is preferably transparent.

Examples of the transparent base material, the lens array, and the transparent material forming the microprojections include polyester resins such as polyethylene terephthalate and polybutylene terephthalate, acrylic resins such as polymethyl methacrylate, polycarbonate resins, polystyrene resins, and polymethyl resins. An ionizing radiation-curable resin composed of a thermoplastic resin such as a pentene resin or an oligomer such as polyester acrylate, urethane acrylate or epoxy acrylate and / or a monomer such as an acrylate is cured by ionizing radiation such as ultraviolet rays or electron beams. A highly transparent resin such as a resin is used. Such a resin usually has a refractive index of about 1.49 to 1.55. In addition to glass, glass and ceramics can be used as long as they have good transparency.

The total thickness of the lens array sheet is usually 2
It is about 0 to 1000 μm.

As the lens array of the lens array sheet of the present invention, for example, as shown in FIG. 10, a unit lens 41 of a triangular prism as a columnar body is arranged adjacently with its major axis (ridge line) parallel to the one-dimensional direction. A triangular prism linear array sheet, a lenticular lens as shown in FIG. 11, or FIG.
As shown in FIG. 3, a fly-eye lens or the like formed by arranging a large number of unit lenses 21 each having a protruding shape such as a hemispherical surface and having an independent periphery in a two-dimensional direction can be used. Here, the cross-sectional shape of the unit lens may be a continuous smooth curve such as a circle, an ellipse, a cardioid, an egg shape of Rankine, a cycloid, or an involute curve as shown in FIGS. Part or all of a polygon such as a triangle, a quadrangle, or a hexagon may be used. As a unit lens arranged in a two-dimensional direction, a pyramid lens can also be used as shown in FIG. These unit lenses are shown in FIGS. 10, 11, 13,
A convex lens as shown in FIG. 14 or a concave lens as shown in FIG. 12 may be used. Among these, preferred are design, ease of manufacture, light condensing, light diffusion characteristics (half-value angle, side lobe light (lens array sheet) It is a cylinder or an elliptical cylinder in view of the small amount of light that is emitted in an oblique direction largely with respect to the normal to the emission surface, the isotropic luminance within the half-value angle, and the luminance in the normal direction). In particular, an elliptic cylinder having a longer diameter in the normal direction of the surface light source is preferable in terms of high luminance. In each of the drawings for describing the shape of the unit lens, the minute projections are not shown.

As a method for producing a lens array sheet, a single-layer lens array sheet as shown in FIG. 7 can be obtained by, for example, a known thermoplastic resin as disclosed in JP-A-56-157310. In addition to the use of a hot press method or an injection molding method, a mold having a lens arrangement 4 and a group of microprojections 2 having an inverted concavo-convex shape can be used.

Further, as another manufacturing method, for example, as disclosed in Japanese Patent Application Laid-Open No. 5-169015, a concave portion having a shape reverse to a desired lens arrangement shape (accurately, a concave and convex shape) is provided. A roll intaglio is filled with an ionizing radiation-curable resin liquid, and a transparent substrate sheet is stacked on top of the liquid. If it is transparent, it is also possible from the inside of the roll intaglio), cures the ionizing radiation-curable resin liquid, and then peels off the transparent substrate sheet from the roll intaglio together with the cured resin, thereby curing the ionizing radiation-curable resin. The liquid becomes a lens array 4 having a desired shape, and an intermediate sheet of the lens array sheet formed on the transparent base sheet is obtained. Next, if the same operation is performed on the back surface of the intermediate sheet with a roll intaglio having a concave portion having a shape opposite to the shape of the desired minute projection group, the minute irregular projection group is provided on the back surface, and The lens array sheet of the present invention having a lens array is obtained. Note that a group of minute projections may be formed before the lens array.

FIG. 19 is a conceptual diagram (cross-sectional view) showing an example of a manufacturing apparatus that can be used in such a manufacturing method using an ionizing radiation-curable resin. In the manufacturing apparatus of FIG.
Is a roll intaglio provided with a concave portion 72 having an inverse shape to the microprojection group 2 (or lens array 4) to be formed (however, the concave portion is shown in a square cross section for simplification of the drawing, and the roll intaglio is (Rotating around the core in the direction of the arrow),
73 is an ionizing radiation-curable resin liquid, 3 is a sheet-shaped transparent substrate, 74 is a pressing roll which abuts against the roll intaglio and presses the transparent substrate 3 against the roll intaglio 71, and 75 supports the running of the transparent substrate 3 A guide roll, 76 is a peeling roll, 77a and 77b are ionizing radiation irradiators for curing an ionizing radiation-curable resin liquid, and 21 is a fine particle formed on the transparent substrate 3 as a cured product of the ionizing radiation-curable resin liquid. The projections 1 and 1 are intermediate sheets 11 and 78 of a lens array sheet having fine projections 21 (or a lens array 4) on a transparent base material 3, and coating devices for ionizing radiation-curable resin liquid.

In the above-mentioned production method, a sheet made of a polyester resin such as polyethylene terephthalate and polybutylene terephthalate can be used as the sheet-like transparent substrate. The thickness is determined based on the workability of handling the device and the like.
It is about 0 μm.

According to such a method, a lens array sheet having a three-layer structure as shown in FIG. 9 having the microprojection group 2 and the lens array 4 on the front and back of the transparent substrate 3 can be obtained.

In the case of a lens array sheet having a two-layer structure as shown in FIG. 8, an intermediate sheet having a lens array is first prepared by press molding, injection molding, casting, or the like.
Next, it can be obtained by forming minute projections by a method using the above-mentioned ionizing radiation curable resin and a roll intaglio or plano intaglio.

Next, in the surface light source 100 of the present invention, the above-described lens array sheet of the present invention is arranged above the light emission surface of a conventionally known surface light source comprising a light source, a light guide, a reflective layer and the like. It can be obtained if implemented. As shown in a perspective view of one embodiment of the surface light source of the present invention in FIG. 16, at least a light guide 51 and a linear or point-like light source disposed adjacent to at least one side end face thereof. Light source 52 and light guide 5
1 is an edge-light type surface light source, which is composed of the light reflection layer 53 on the back surface of the first optical element 1 and the above-described lens array sheet 1 of the present invention. Usually, a lamp house 54 having a reflective surface on the inner surface is further provided around the light source 52. Usually, the light guide 51
Contains 1 to 10 of acrylic resin and polycarbonate resin
A transparent plate of about mm is used, a linear light source such as a cold cathode tube is used as the light source 52, and a metal film is deposited on the light reflecting layer 53 after white coating or sandblasting to diffuse and reflect light. Or by plating. Further, the arrangement of the light diffusion dot pattern printed in white may be adjusted to make the amount of light emitted from the light exit surface uniform. Further, a light diffusion sheet may be disposed between the light guide 51 and the lens array sheet 1 to uniformly diffuse light and make the light diffusion dot pattern of the light reflection layer 53 invisible.

When a lens array sheet is mounted on a surface light source, one sheet may be used. However, in the case of a columnar lens, in order to control the light diffusion angles in two directions (up and down and left and right), FIG.
The two lens array sheets may be stacked such that the ridge lines of the unit lenses intersect (orthogonal in the figure). In this case, a surface having a lens array (hereinafter, referred to as a lens surface)
The orientation of the two lenses should be the same so that the light transmission is high, and moire fringes between the lens surface of the lower lens array sheet and the minute projections on the back surface of the upper lens array sheet can be prevented. Although it is optimal, the lens surfaces of the two lens array sheets may of course be opposed to each other.

Also, using two lens array sheets,
If a sheet having unevenness on the front and back sides of the wavelength of the light source light or more is used as the above-mentioned light diffusion sheet 56 between the lens array sheet and the light guide 51, fine projections are not required on the back side of the lower lens array sheet. It is. This is because the unevenness on the front and back surfaces of the light diffusion sheet acts to prevent optical adhesion. With such a configuration, two lens array sheets are used, but one can use the conventional rear surface flat lens array sheet 19, which is advantageous in cost. In addition, while the light diffusion sheet provides the effect of uniform diffusion of light, the light emitted outside the viewing angle generally tends to increase, but the light diffusion dot pattern of the light reflection layer on the back surface of the light guide body is increased. There is an effect of invisibility. Such an edge light type surface light source 101 is shown in FIG.
FIG.

The rear-surface flat lens array sheet has a lens array in which unit lenses are arranged in a one-dimensional or two-dimensional direction on the front surface side of a transparent base material, and the rear surface side is a smooth surface without minute projections. This is a configuration in which the lens array sheet 1 of the present invention does not have the minute projection group 2 on the back surface. The material and manufacturing method thereof are the same as those of the lens array sheet of the present invention. Applicable. Further, the light diffusion sheet has an uneven surface on the front and back surfaces in order to prevent the light diffusion sheet from adhering to the smooth surface of the front surface of the light guide and the back surface of the lower lens array sheet. On the other hand, the light diffusion action is performed by the light scattering agent on the uneven surface or inside the light diffusion sheet. As such a light diffusing sheet, a known light diffusing sheet can be used.For example, a transparent resin substrate such as an acrylic resin, in which light diffusing agent particles such as silica are dispersed, or a transparent resin surface What emboss-processed the fine uneven | corrugated shape, such as a grain, is mentioned.

Further, by disposing the above-described edge light type surface light source of the present invention as a backlight on the back of a transmissive display such as a transmissive liquid crystal display device or an advertising board, the transmissive type light source of the present invention is provided. A display is obtained. FIG. 17 shows an embodiment of the transmissive display 200 of the present invention in which the translucent display 6 is disposed on the surface light source 100 of the present invention of FIG.

[0069]

According to the lens array sheet of the present invention, since there are minute projections on the back surface, when two lens array sheets are stacked, or when they are stacked on the light emitting surface of the light guide surface as a surface light source, the lens array is arranged. Adhesion on the back surface of the sheet is prevented, and the occurrence of interference fringes of equal thickness is suppressed. When the lens array sheet is placed on the light guide such that the back surface of the lens array sheet (the surface on which the minute projections are formed) faces the light guide,
Emission light having a uniform luminance distribution over the entire light emission surface can be obtained without disturbing the distribution of light due to total reflection on the light guide surface. In addition, since each microprojection constituting the microprojection group is arranged in a random shape and position by a specific randomization method using percolation theory, there is no distribution unevenness regardless of the number of the microprojections. The uniform area distribution is obtained to help uniform luminance distribution, and the occurrence of moire fringes due to interference with the lens arrangement and the arrangement of pixels of the liquid crystal display element is suppressed. In addition, it is easy to manufacture by making the solid that constitutes the cluster of microprojections into a rectangular parallelepiped, and the arrangement of the rectangular parallelepiped depends on the specific relationship between the side surface and the surface of the unit lens that constitutes the lens array. By doing so, the occurrence of moire fringes due to the relationship with the lens arrangement is suppressed. According to the edge light type surface light source of the present invention, since the lens array sheet as described above is used, light energy is effectively used. Further, according to the transmission type display of the present invention, a bright display can be obtained because such a surface light source is used.

[0070]

【Example】

<< Example 1 >> By a manufacturing apparatus as shown in FIG. 19, a transparent biaxially stretched polyethylene terephthalate film having a thickness of 100 μm was used as a transparent substrate, and an ultraviolet-curable ink containing a urethane acrylate prepolymer as a main component was used.
An intermediate sheet having a lens array having an isosceles triangular triangular prism lens having a cross-sectional shape having a vertex angle β (see FIG. 10) of 100 ° as a unit lens was prepared. Next, similarly, using the same ultraviolet curable ink as the above on the back surface of the intermediate sheet, the height H is 10 μm, the length of one side a of the bottom is 100 μm, and the other side of the bottom is similarly set using the apparatus of FIG. A rectangular parallelepiped having a length b of 100 μm was defined as a microprojection element. The arrangement of the microprojection elements is a two-dimensional lattice having a grid number of 4096 × 409.
Six pieces were arranged on cluster sites of site percolation with an occupancy probability P = 0.2 on a square lattice having a lattice constant of 100 μm. Since adjacent microprojections have the same lattice constant as one side of the bottom of the microprojections, they are directly connected to form a cluster. As a result, a group of microprojections as shown in FIG. 25 was generated, and a lens array sheet of the present invention was obtained using the group. The roll intaglio shown in FIG. 19 for manufacturing the microprojection group was formed by forming a surface having the same shape and reverse irregularities as the microprojection group. These operations were performed by computer image processing based on the Monte Carlo simulation data to create the image data. Using this image data, a silver halide photosensitive film for plate making was exposed to light using a scanner for printing plate making to produce an original film (fine projections were black and the other portions were transparent). Then, a photosensitive resist is applied to the surface of the cylindrical copper cylinder, and the original film is contact-exposed thereon and developed to remove the resist in the unexposed portion (within a rectangle), and only the exposed portion becomes a cured film. A resist pattern was formed, the surface of the cylinder was corroded with an aqueous ferric chloride solution, and then the resist was removed to form a roll intaglio having a rectangular portion as a recess. The plate depth was the same for all rectangles. The directions of the rectangular parallelepipeds of the microprojections are all the same, and the intersection of the side surface of the rectangular parallelepiped with the horizontal plane of the lens array sheet (X ′ axis in FIG. 4) and the configuration plane of the unit lens and the horizontal plane of the lens array sheet Intersection (Fig. 4
And X axis) are parallel. The ratio Sr of the cross-sectional area of the microprojection to the total area is Sr = 20%,
The maximum turning radius Rs ^{max of the} cluster was 110 μm.

<< Embodiment 2 >> In Embodiment 1, a simulation was performed by changing the occupation probability to P = 0.3, and Sr = 30
%, Rs ^max = 230 μm, and a lens array sheet of the present invention was obtained in the same manner as in Example 1, except that the cluster pattern was a group of microprojections as shown in FIG.

<< Embodiment 3 >> In Embodiment 1, a simulation was performed by changing the occupation probability to P = 0.4, and Sr = 40
%, Rs ^max = 260 μm, and a lens array sheet of the present invention was obtained in the same manner as in Example 1 except that the cluster pattern was a group of microprojections as shown in FIG.

<< Embodiment 4 >> In the first embodiment, the simulation is performed by changing the occupation probability to P = 0.5, and Sr = 50
%, Rs ^max = 630 μm, and a lens array sheet of the present invention was obtained in the same manner as in Example 1, except that the cluster pattern was a group of microprojections as shown in FIG.

<Comparative Example 1> In Example 1, a lens array sheet in which fine irregularities were not provided on the rear surface of the intermediate sheet having the lens array formed on the front surface was used.

Comparative Example 2 In Example 1, after obtaining the intermediate sheet having the lens array formed on the front surface,
A coating liquid in which 3% by weight of acrylic resin beads having a particle size of 2 to 20 μm was added to a two-part curable urethane resin was applied at 5 g / m ² by a gravure coating method to obtain a matted lens array sheet.

<< Comparative Example 3 >> In Example 1, a simulation was performed by changing the occupation probability to P = 0.6 (> Pc).
Sr = 63%, Rs ^max = total lattice size (corresponding to an infinite cluster), and a lens array sheet was obtained in the same manner as in Example 1 except that the cluster pattern was a group of microprojections as shown in FIG. .

Table 1 shows the performance of the lens array sheets of the above Examples and Comparative Examples. The evaluation criteria are as follows. Adhesion resistance: "O" indicates no adhesion between the rear surface of the lens array sheet and another flat plate (light emitting surface of the light guide), and "X" indicates occurrence of adhesion. The close contact, that is, the presence or absence of the optical contact, indicates that there is close contact (x) when the area near the light source on the light emitting surface looks brighter than the others, and that there is no close contact when the bright area near the light source is not visually recognized ( ○). Equal thickness interference fringes: One lens array sheet was superimposed on another flat plate and visually observed. When no equal thickness interference fringes were generated, it was evaluated as “○”, and when it was generated, as “X”. Moiré fringes: A single lens array sheet was visually observed, and "○" indicates that no moire fringes between the microprojections and the lens array were generated, "△" indicates that it was slightly observed, and "x" indicates that it was noticeable. " Luminance factor: The portions other than the lens array sheet are the same edge light type surface light source, and the lens array sheet of each of the above-described embodiments and the comparative example is placed on the lens array side so that only the lens array sheet is replaced on the light guide surface. The light source was placed toward the output side (outside) of the light source, and the luminance was measured using a goniophotometer GONOPHOTOMETER manufactured by Murakami Color Research Laboratory. As a reference, the luminance in the normal direction of Comparative Example 1 in which no irregularities were formed on the back surface was measured at a portion near the light source where luminance did not decrease, and was set to 100%. Viewing angle: luminance is 5 with luminance in the normal direction being 100%.
The angle (half-value angle) from the normal line that is 0% was set. The measuring method is the same as described above.

[0078]

[Table 1] *: Cannot be measured. If the light is about 2cm away from the light source, the emitted light will be extremely dark.

[0079]

According to the lens array sheet of the present invention, when two lens array sheets are stacked, there is no close contact between the sheets, and even when one sheet is stacked on the light guide of the surface light source, the close contact with the light guide is maintained. Not
As a result, it is possible to prevent the occurrence of interference fringes having the same thickness. Moreover, compared to the conventional matte treatment to prevent adhesion,
The amount of light absorbed or emitted out of the viewing angle is small, and a decrease in luminance can be minimized. In particular, the minute projections are fractal random-shaped clusters, and the clusters are randomly distributed without unevenness. Therefore, even though the spread of clusters, that is, the average rotation radius is large, there are many random voids in the radius, and therefore, it is difficult to visually discriminate, and it is difficult to generate luminance unevenness. In the edge light type surface light source of the present invention, since the lens array sheet does not adhere to the light emitting surface of the light guide, light from the light source can be widely and uniformly distributed in the light guide. In addition, the luminance distribution of the light emitted from the light guide within the light emission surface can be made uniform. Then, the light energy is used effectively and the light is bright, and the light diffusion dot pattern can be made invisible. In addition, the amount of light emitted near the normal direction of the emission surface is large, and the light emitted away from the normal direction can be reduced as compared with the isotropic diffusion sheet. Further, the transmissive display of the present invention is bright over the entire display surface, and is uniform and bright depending on the viewing angle.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one embodiment of a lens array sheet of the present invention.

FIG. 2 is a perspective view showing an example of a polygonal column shape forming minute projections of the lens array sheet of the present invention.

FIG. 3 is a perspective view illustrating a cube as a polygonal pillar that forms a minute projection.

FIG. 4 is an explanatory diagram in which a side surface of a minute projection and a constituent surface of a lens array are non-parallel.

FIG. 5 is a view for explaining minute projections composed of clusters obtained by percolation of a two-dimensional lattice. (A) is a diagram in which grid points of a two-dimensional grid are occupied by squares with a certain occupancy probability, and (b) is a diagram in which (a) is a diagram in which adjacent squares in the vertical and horizontal directions are connected to generate clusters (microprojections). .

FIG. 6 is an explanatory diagram of how to fuse the microprojections.

FIG. 7 is a longitudinal sectional view of one embodiment (single layer) of the layer arrangement of the lens array sheet of the present invention.

FIG. 8 shows another embodiment (2) of the layer configuration of the lens array sheet.
Layer).

FIG. 9 shows another embodiment (3) of the layer configuration of the lens array sheet.
Layer).

FIG. 10 is a perspective view of an example of a lens array (a triangular prism lens) of the lens array sheet.

FIG. 11 is a perspective view of another example (an elliptic cylinder lens) of a lens array of the lens array sheet.

FIG. 12 is a perspective view of another example (concave lens) of the lens array of the lens array sheet.

FIG. 13 is a perspective view of another example of the lens array (fly-eye lens) of the lens array sheet.

FIG. 14 is a perspective view of another example (a pyramid lens) of the lens array of the lens array sheet.

FIG. 15 is a perspective view illustrating the two-lens arrangement sheet.

FIG. 16 is a perspective view of one embodiment of an edge light type surface light source of the present invention.

FIG. 17 is a perspective view of one embodiment of a transmissive display according to the present invention.

FIG. 18 is a perspective view of another embodiment of an edge light type surface light source according to the present invention.

FIG. 19 is a conceptual diagram showing an example of a manufacturing apparatus that can be used for manufacturing the lens array sheet of the present invention.

FIG. 20 is an explanatory diagram showing the microscopic behavior of a light beam traveling from the inside to the outside of the light guide.

FIG. 21 is an explanatory diagram showing the behavior of a light beam that travels by a tunnel effect from a light guide to a lens array sheet at a small distance.

FIG. 22 is an explanatory diagram in which a contact portion between a minute projection of the lens array sheet of the present invention and the surface of the light guide participates in the distribution of light inside the light guide.

23A and 23B are diagrams showing various examples of a two-dimensional lattice, in which FIG. 23A is a kagome lattice, and FIG. 23B is a hexagonal lattice.

FIG. 24: Occurrence probability P is critical percolation concentration Pc
The microprojection group at the time of the above.

FIG. 25 shows a group of minute projections when the occupation probability P is variously changed (part 1).

FIG. 26 shows a group of minute projections when the occupation probability P is variously changed (part 2).

FIG. 27 shows a group of minute protrusions when the occupation probability P is variously changed (part 3).

FIG. 28 shows a group of minute projections when the occupation probability P is variously changed (part 4).

FIG. 29 shows a group of minute projections when the occupation probability P is variously changed (part 5).

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Lens arrangement sheet 11 Intermediate sheet of lens arrangement sheet 19 Back plane lens arrangement sheet (conventional lens arrangement sheet) 2 Microprojection group 21 Microprojection 24 Microprojection element 25 Penetration cluster (microprojection) 26 Connection part of microprojection element 3 Transparent substrate 31 Transparent substrate sheet 32 Microprojection base 4 Lens arrangement 41 Unit lens 42 Triangular prism unit lens slope 51 Light guide 52 Light source 53 Light reflection layer 54 Lamp house 55 Light guide surface (light emitting surface) 56 Light Diffusion sheet 6 Translucent display body 71 Roll intaglio 72 Concave portion 73 Ionizing radiation curable resin liquid 74 Pressing roll 75 Guide roll 76 Peeling roll 77a, 77b Ionizing radiation irradiating device 78 Coating device 8 Grid point (component) 9 Micro projection Air gap 100 surface light source 101 surface light source (lens array Preparative two used) 200 transmissive display body n _1, n ₂ the refractive index L _1, L _2, L ₃ incident light L _1R reflected light L _1T, L _3T traveling wave output light, transmitted light L _1V tunnel field y guide The length of the light emitting portion near the light source of the light body Y The total length in the light propagation direction of the light guide α The intersection of the intersection line between the side surface of the minute projection and the horizontal plane of the lens array sheet, and the plane of the unit lens and the horizontal plane of the lens array sheet The angle between the line and the line. β Apex angle of triangular prism lens. λ Light wavelength θ Incident angle θ 'Exit angle θc Critical angle

Claims (8)

(57) [Claims] 1. A microprojection group in which unit lenses are arranged in a one-dimensional or two-dimensional direction on a front surface side of a transparent substrate, and microprojections are randomly and two-dimensionally distributed on a rear surface side. The microprojections are polygonal prisms or truncated pyramids, and the minimum diagonal length at the upper and lower bases at the upper and lower bases is equal to or greater than the wavelength of the light source light and the maximum diagonal length is 500 μm or less. What is claimed is: 1. A lens array sheet, which is assigned to constituents constituting a cluster obtained at a concentration lower than a critical percolation concentration Pc in percolation, and is obtained by fusing microprojections in the same cluster. 2. A method in which small projections are assigned to the lattice points with the occupancy probability P less than the critical percolation concentration Pc, and the small projections in the same cluster are fused with each other as a constituent element of the cluster using the lattice points of the two-dimensional lattice. 2. The lens array sheet according to claim 1, wherein is a minute projection. 3. The lens array sheet according to claim 1, wherein the two-dimensional lattice is a square lattice, and the microprojections assigned to the lattice points are rectangular parallelepipeds. 4. An intersection line at which a horizontal plane of the lens array sheet intersects with a surface constituting the unit lens, and an intersection line at which the horizontal plane intersects with a side surface of a microprojection made of a rectangular parallelepiped microprojection element are non-parallel to each other. 4. The lens array sheet according to claim 3, wherein: 5. A light guide comprising at least a light-transmitting flat plate, a light source unit provided adjacent to at least one of the side end surfaces of the light guide, and a light guide unit provided on a back surface of the light guide. The light reflecting layer provided, and one or two sheets formed by laminating a group of minute projections on the light emitting surface of the light guide surface toward the light guide surface side.
And a lens array sheet according to 2, 3, or 4. 6. A lens array sheet comprising:
6. The surface light source according to claim 5, wherein the plurality of lens arrangement sheets are stacked, and the minute projections of the lower lens arrangement sheet are stacked toward the light guide surface side. 7. A light-diffusing sheet having irregularities on the front and back sides of the light-emitting surface on the light-emitting surface of the light guide, and a unit lens on the front side of the transparent substrate in one-dimensional or two-dimensional directions. 5. A rear-surface flat lens array sheet having a lens array in which the rear surface is a smooth surface without fine projections and has a rear surface facing the light guide surface surface. The lens array sheet and the lens array sheet are arranged in this order so as to overlap with each other.
Surface light source as described. 8. A transmissive display comprising the surface light source according to claim 5, 6 or 7 as a rear light source of the translucent display.