JPH0875928A - Lens sheet, edge light type surface light source, and transmission type display - Google Patents

Abstract

PURPOSE: To provide a lens sheet to obtain uniform and bright light with good use efficiency, in a backlight used for a transmission type liquid crystal display element or the like, and to provide an edge light type surface light source and a transmission type display body. CONSTITUTION: On the top surface of a transparent substrate, a lens array 4 formed by arranging unit lenses in one or two dimensions, and lots of minute projections 21 in a polygonal shape with each side larger than the wavelength of the light source and <500μm length are randomly and wholly distributed in a two-dimensional distribution on the back surface. Or, such a structure is formed that minute projections are make to be rectangular parallelepipeds and that crosslines of the side faces of rectangular parallelepipeds and horizontal face of the lens sheet and crosslines of the unit lens faces and horizontal planes are not parallel. The surface light source is equipped with this lens sheet, and the transmission display is equipped with this surface light source.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Recently, in transmissive liquid crystal display elements,
Demands for lighter weight and lower power consumption are further increasing, and various proposals are made to condense light in a specific direction in a surface light source that effectively uses light from the light source and uniformly guides it in only necessary and sufficient directions. Has been done. In these devices, a light source is usually arranged on the side surface of a light guide made of a plate material such as transparent acrylic resin, and the light source light incident on the light guide body from the side surface is reflected by a reflection layer on the back surface of the light guide to guide the light. Light from the light source is emitted from the light emitting surface on the upper surface of the light body for use. At that time, in order to make the light uniform, a diffusion sheet is arranged on the upper surface of the light guide body, or a lens sheet acting as a lens is arranged in order to collect the emitted light only in a specific direction. A surface light source having a structure to perform is used. A surface light source in which a light source is arranged on the side surface of such a light guide is called an edge light type surface light source because of its configuration. Further, there is a direct type surface light source in which the light source is arranged directly below the diffusion sheet or the lens sheet, but its use is limited as a surface light source for a liquid crystal display element because it is thick.

In the above-mentioned surface light source, various measures have been proposed for effectively using the light from the light source without waste, and a lens sheet for condensing the light as emitted light in a specific direction is also proposed. It is one of them. The lens sheet is, for example, a triangular prism as a unit lens as shown in FIG.
It is known that many unit lenses are arranged in a one-dimensional direction such that the ridge directions of the unit lenses are parallel to each other. Further, it has been proposed that two such lens sheets are used in a stacked manner to further condense light to increase brightness. For example, JP-A-5-203950 and JP-A-5-313.
Japanese Patent Application Laid-Open No. 156 and Japanese Patent Application Laid-Open No. 5-313164 propose a structure in which two lens sheets each having a triangular prism as a unit lens are stacked.

[0004]

However, when two lens sheets are stacked, brightness is improved due to the condensing effect, but there is a problem. If a unit lens is arranged on the upper side surface and the back surface is a smooth surface lens sheet, the back surface of the upper lens sheet and the apex portion of the unit lens of the lower lens sheet are in microscopic contact. But as a result,
Since the optically transparent contact portion has a shape along the apex portion of the lower unit lens, the apex shape of the lens is visually recognized. For example, if the unit lens is a triangular prism lens, the apex is a ridgeline, and many line segments are visible.
Also, due to the subtle difference in the distance between the two lens sheets,
A Newton ring, which is a kind of equal-thickness interference fringes, may occur as a circular or elliptical pattern on the entire surface of the surface light source.
For this reason, for example, Japanese Patent Application No. 5-323214 proposes an attempt to prevent the adhesion of lens sheets to each other by matting the back surface of the lens sheet to form minute irregularities.

However, when the back surface of the lens sheet is matted, the light diffusely reflects there, acts like a diffusion sheet, and condenses the light within a desired diffusion angle centered on the intended direction. The function of the sheet may be deteriorated and the brightness may be significantly reduced. Further, in the mat processing, since the height of the unevenness on the back surface of the lens sheet is not completely uniform, a slight difference in the distance between the two lens sheets cannot be avoided, and the same thickness interference fringes also occur. is there.

On the other hand, even if only one lens sheet is used, if the back surface of the lens sheet is smooth, when the lens sheet is arranged on the light emitting surface of the light guide of the edge light type surface light source, the lens sheet is arranged. The light-emitting surface of the light guide and the light-emitting surface of the light guide are in close contact with each other and are optically integrated, so that it is impossible to uniformly distribute the light from the light source due to total reflection of light on the surface of the light guide.
Further, in order to provide a gap between the light guide and the lens sheet, even if spacers are provided at the four corners of the light guide or the lens sheet, the lens sheet bends and deforms,
A subtle difference in the distance between the light guide and the lens sheet is unavoidable and uniform interference fringes occur. Therefore, it is possible to form fine irregularities having a wavelength of the light of the light source or more on the entire back surface of the lens sheet, for example, Japanese Patent Laid-Open No. 5-323319 and Japanese Patent Application No. 5-869.
No. 54 is proposed. However, since such minute unevenness is a light isotropically diffusive pattern such as sand or satin, a part of the light beam emitted from the light guide is scattered as a side lobe light outside the viewing angle. The light effect is reduced,
There is also a problem that the energy of the light from the light source is wasted and the brightness is reduced.

Therefore, in the present invention, the above problems are solved, the light energy of the light source light is effectively used, the brightness is not lowered while the condensing action is maintained, and the uniform thickness interference fringes and the outside of the viewing angle are provided. It is an object of the present invention to provide a lens sheet that does not uselessly dissipate light, an edge light type surface light source using the lens sheet, and a bright transmissive display body using the surface light source.

[0008]

Therefore, the lens sheet of the present invention has a lens array in which unit lenses are arrayed in a one-dimensional or two-dimensional direction on the front surface side of the transparent substrate, and on the back surface side, It is a polygonal column and the length of each side is equal to or greater than the wavelength of the light source light and 5
A large number of fine protrusions of 00 μm or less are formed on the entire surface, and a fine protrusion group is formed by arranging them in a random two-dimensional distribution. Further, in the above lens sheet, the minute projections may be rectangular parallelepiped. Further, in the lens sheet, a line of intersection where the horizontal plane of the lens sheet intersects with the surface forming the unit lens and a line of intersection between the horizontal plane and the side surface of each rectangular parallelepiped forming the minute projection group are non-parallel to each other. It is also a configuration.

Further, in the edge light type surface light source of the present invention, at least a light guide body made of a translucent flat plate, and a light source unit provided adjacent to both or one of the side end surfaces of the light guide body, The light reflection layer provided on the back surface of the light guide body, and one or two of the above-mentioned books formed by stacking microprojections on the light emitting surface of the light guide surface toward the light guide surface side. And a lens sheet of the invention. In addition, the lens sheet is a structure in which two lens sheets are superposed on each other, and the minute projections of the lower lens sheet are laminated toward the light guide surface side.

Further, in another edge light type surface light source of the present invention, in the structure of the surface light source using one sheet of the lens sheet of the present invention, further, between the light guide and the lens sheet of the present invention, In order from the light guide body side, a light diffusing sheet having irregularities of the wavelength of the light source light or more on the front and back surfaces, and a lens array formed by arranging unit lenses in a one-dimensional or two-dimensional direction on the front surface side of the transparent substrate, The back side is a smooth surface with no minute protrusions,
A back surface flat lens sheet with the back surface facing the light guide surface side,
Are arranged in a stack.

The transmissive display body of the present invention has the edge light type surface light source of the present invention as a back light source of the translucent display body.

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

First, FIG. 1 is a perspective view showing an embodiment of the lens sheet of the present invention. In the lens sheet 1 of the present invention shown in FIG. 1, the unit lens 4 is provided on one surface of the transparent substrate sheet 31.
A triangular prism lens is used as 1 and has a lens array 4 in which a plurality of the unit lenses are arranged in a one-dimensional direction so that their unit ridges are parallel to each other.
Then, it is on the upper side so that the minute protrusions can be easily seen)
In addition, a large number of rectangular parallelepipeds are formed as the minute protrusions 21, and the minute protrusion group 2 formed by arranging them in a random two-dimensional distribution is provided on the entire surface.

The lens 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 minute projections are polygonal prisms and each side has a length not less than the wavelength of the light source and 500 μm. The following small protrusions are arranged in a large number on the entire surface in a random two-dimensional distribution.

The shape of the minute protrusions 21 is a polygonal column,
The polygonal prism includes a triangular prism, a quadrangular prism, a pentagonal prism, a hexagonal prism, and the like. Among them, the quadrangular prism includes a rhomboidal prism, a regular quadrangular prism, and the like, but two opposing sides forming a side surface of the columnar body are parallel to each other. A rectangular prism having a rectangular parallelepiped shape is preferable because it is easy to manufacture and moiré is less likely to occur. FIG. 2 shows the shape of one minute projection 21 formed of this rectangular parallelepiped, and has a height H,
The relationship between the three sizes of the bases a and b may be any of a = b = H (cube), a = b ≠ H, a ≠ b = H, and a ≠ b ≠ H. As illustrated in FIG. 3, the height H of the minute protrusions plays a role of a spacer with another lens sheet or the light emitting surface of the light guide when the lens sheet is mounted, and the entire surface of the lens sheet. It is preferable that the heights H of all the minute projections distributed in the same are not bent when the lens sheet is mounted and a uniform interval can be secured so that Newton's rings are hard to appear. The lengths of the sides a and b are
The minute protrusions 31 may be different or the same.

Further, the height H and the dimensions of the sides a and b are not less than the wavelength of the light source light and not more than 500 μm, and more preferably 12
It is preferably 5 μm or less. When the spectrum of the light source light has a distribution, it is set to the maximum wavelength of the visible light spectrum or more. If the wavelength is less than the wavelength of light, it is impossible to effectively prevent generation of equal-thickness interference fringes or integration of optical contact between the lens sheet and the light guide, and conversely 500 μm.
If it exceeds m, the lens sheet is likely to be flexibly deformed, moire fringes are likely to be formed between the lens sheet and the pixels of the display body, or it may be difficult to manufacture.

The reason why the height H of the minute projections 21 should be equal to or larger than the wavelength of the light from the light source will be described in detail below. First, consider a case where the lens sheet is placed on a plate-shaped light guide, and the back surface of the lens sheet and the light guide surface are in contact with each other. As shown in FIG. 20, when the incident light L ₁ traveling from the inside of the light guide body 51 into the air reaches the light guide body surface 55 which is the interface between the light guide body 51 and the air, the incident angle θ becomes If it is larger than the critical angle θc, total reflection occurs, and all the energy of the incident light L ₁ becomes the reflected light L _1R, and the incident light does not enter the air. However, looking at this phenomenon microscopically, the electromagnetic field of the incident light penetrates into the air at a distance of about the wavelength λ of the light source light from the light guide surface 55 due to the tunnel effect. The intensity of the tunnel electromagnetic field L _1V soaked in is attenuated by an exponential function of the approach distance, and all the light guide 51 is reached at a wavelength of about λ.
I will turn back to my side. Therefore, when viewed macroscopically, all the light energy is reflected by the light guide surface 55.

Therefore, as shown in FIG. 21, the lens sheet 1
When the distance ΔX between the light guide surface 55 and the light guide surface 55 approaches a distance (ΔX <λ) less than the wavelength of the light from the light source, the tunnel electromagnetic field L _1V that is not completely attenuated again travels inside the lens sheet 1 with a traveling wave ( The output light becomes L _1T , and the light is transmitted through the lens sheet 1. Therefore, the height H of the minute unevenness 21 is H
When <λ, the entire surface 55 of the light guide is
Total internal reflection of light from the light guide body does not occur. as a result,
For example, as the incident light L _{3 in} FIG. 22, since the incident angle near the light source is less than the critical angle, it is taken out as the output light L _3T , but is incident on the portion apart from the light source by a certain degree or more. All the light, for example, light such as L ₂ in FIG. 22 has an incident angle equal to or greater than the critical angle, and therefore is totally reflected by the light guide surface 55 and does not serve as output light. Therefore, the luminance distribution of the output light from the surface of the light guide body is bright only in the vicinity of the light source and dark in the other regions, which is not preferable.

On the other hand, when the height H of the minute protrusion 21 is H ≧ λ [Equation 1], even in the region away from the light source, the portion where the minute protrusion 21 and the light guide 51 are in contact with each other. Like L ₁ in FIG. 22, the incident light L ₁ is not totally reflected, but some of the light becomes transmitted light L _1T, and output light is obtained. Therefore, the amount of output light from the surface of the light guide is sufficiently secured even in the area away from the light source. Further, the light incident on the portion between the minute protrusions 21 is totally reflected on the light guide surface 55 because there is a void 9 having a wavelength of light or more on the light guide surface as shown by L ₂ in FIG. 22, for example. Is reflected. Therefore, L ₂ is not output on the spot, is distributed farther from the light source, and is used as output light there.

As can be seen from the above consideration, the minute projections 2
A lens sheet having a height H of H ≧ λ is placed so that the minute projections face the light guide surface, thereby obtaining output light having a uniform luminance distribution over the entire area of the light guide surface. It becomes possible.

Next, consideration will be given to the case where two lens sheets are used in an overlapping manner. As proposed in Japanese Patent Application No. 5-323214 (not yet published at the time of filing of this application) filed by the same applicant as the present invention, the condition for eliminating the equal-thickness interference fringes between the two lens sheets is a minute protrusion. 21. Height H, wavelength λ of light source light, illumination light source from the outside as seen from the light reflecting surface (front surface, back surface, etc.) of the lens sheet from the observer (sunlight from window, light from electric lamp on ceiling) , Etc., where H ≧ λ / (2Δφ ² ) [Equation 2]. However, under normal use conditions of the lens sheet, if [Equation 1] is satisfied, [Equation 2] will be satisfied. That is, λ / (2Δφ ² ) ≧ λ holds. Now, when the specific numerical value of [Equation 2] is obtained, it is assumed that the surface of the lens sheet is observed using 0.38 μm ≦ λ ≦ 0.78 μm of white light as an external light source, and the angular radius of the external light source is 1 usually by indoor lighting or natural light from windows
0 ° ≦ Δφ ≦ 120 °, that is, 0.175 [ra
d] ≦ Δφ ≦ 2.094 [rad], [Equation 2]
Therefore, the right side of [Equation 2] is the smallest, Δθ = 0.175.
As a value corresponding to [rad] and λ _MAX = 0.78 [μm], it is possible to obtain H ≧ 12.5 [μm]> λ _MAX = 0.78 [μm].

The dimensions a and b of the bottom surface of the minute protrusion 21 are required to be 1 μm or more in order to secure the minimum strength as a spacer, although it depends on the height H thereof. Further, when it is 125 μm or more, and particularly when it exceeds 500 μm, minute projections become visible, and when it is used for a liquid crystal display element, moire fringes with the pixel are likely to occur, which is not preferable.

The two-dimensional distribution of the minute projections 21 having the above dimensions on the lens sheet surface is preferably a random distribution.
If the minute protrusions are arranged periodically, the unit protrusions on the opposite surface of the lens sheet (in most cases, they are arranged periodically) will always overlap each other at a certain period. , Appear as moire stripes. Also,
When used as a backlight of a color liquid crystal display device, in addition to the arrangement period of the unit lenses forming such a lens arrangement, Moire fringes are likely to appear due to interference with the arrangement period of pixels of the display device. Therefore, the array of microprojections is
By making it non-periodic, the generation of moire fringes is prevented.

However, even if the fine projections 21 are randomized as described above, if the polygonal columns of the fine projections have the same shape and are aligned in the same direction, the moire fringes are of the same type (for example, trapezoidal shape). If so, all the side surfaces (upper bottoms) face in the same direction, so that these minute side surfaces in the same direction aggregate to form a large virtual side surface. Since the minute projections are randomly arranged on this virtual side surface, there is no periodicity, but there is a case where moire fringes may occur due to interference with the surface of the unit lens forming the lens arrangement. Therefore, it is preferable that the surface forming the unit lens and the side surface of the minute projection have a certain fixed relationship.

FIG. 4 is an explanatory diagram for preventing the generation of the moire fringes. For example, as shown in FIG. 4A, the lens array of the lens sheet 1 is a unit lens 41 of a triangular prism lens.
Consider the case of The exit surface of the lens sheet 1 is a surface parallel to the XY plane and is a horizontal plane. The normal direction perpendicular to the emission surface is the Z-axis direction (not shown). The surface forming the unit lens 41 is a slope 42 that forms a mountain valley, and the intersection line between this surface (slope) and the horizontal plane is a line parallel to the X axis (the X axis is parallel to the intersection line). The coordinate axes are set so that). Strictly speaking, the slope is a finite surface, and there are many horizontal planes depending on how the Z-axis coordinate is taken. The slope and the horizontal plane do not intersect depending on the conditions, but the line of intersection here is the plane (slope). Is a line that extends and intersects the horizontal plane. Of course, if the unit lenses are triangular prisms and they are arranged in a one-dimensional direction, there is only one kind of intersection line, but if other types of unit lenses such as a quadrangular pyramid are arranged in a two-dimensional direction, There may be two or more types of intersecting lines derived from the surfaces forming the unit lens, and these intersecting lines may not be orthogonal.

Next, FIG. 4B shows one intersection line derived from the microprojection group 2 with respect to the XY coordinate axes, which is based on the intersection line derived from the unit lens 41 of the triangular prism lens. The X'-axis is a combination of orthogonal X'-Y 'coordinate axes. All the minute projections 21 (here, rectangular parallelepipeds) are oriented in the same direction, and there are two types of intersecting lines between their side surfaces and the horizontal plane of the lens sheet, which are orthogonal to each other, and intersecting lines parallel to the X ′ axis and Y ′ axis. Is a line of intersection parallel to. This X'axis and the previous X
It forms an angle α with the axis. It should be noted that a large number of minute projections are scattered, and there are also many intersecting lines between those numerous side surfaces and the horizontal surface of the lens sheet, but since the directions of the minute protrusions are aligned, a rectangular parallelepiped is represented by the direction of the intersecting lines. In this case, there are two types of intersecting lines that intersect at right angles.

If the angle α formed by the X axis and the X'axis is zero, they become parallel and moire fringes are likely to occur. However, Moire fringes can be prevented by arranging the intersecting lines derived from the unit lens and the intersecting lines derived from the minute protrusions so that they are separated by more than 5 °. That is, in the case of a rectangular parallelepiped, if the angle α is clockwise (clockwise) and is in the range of 5 to 85 °, and more preferably in the range of 10 to 80 °, the generation of moire fringes can be effectively prevented. The angle α is -5 to -85 °, more preferably -10 to counterclockwise.
It may be in the range of -80 °. In the case of a rectangular parallelepiped, when the angle exceeds 85 °, the angle of the intersection line derived from the side face of interest becomes larger, but the relation with the adjacent side face (which makes 90 ° with respect to the side face) is parallel. Close to
Moire fringes are likely to occur due to the relationship with the adjacent side surfaces. In this way, due to the relationship with the side faces of the polygonal column, the occurrence of moire fringes can be prevented by separating from the parallel by more than 5 °.

The minute protrusions are, for example, rectangular parallelepipeds,
When the line of intersection between the noted same side surface of each rectangular parallelepiped and the horizontal surface of the lens sheet and the line of intersection between the surface of the unit lens and the horizontal line are defined at an angle exceeding 5 ° as described above. , It is not necessary to align all the orientations of all the minute projections (in this case, rectangular parallelepipeds) to be arranged. For example, even if 1% of all the small protrusions are horizontal, if they are not gathered in adjacent portions, they have strength enough to define a parallel relationship that causes the generation of moire fringes. Because there is no. In this sense, in claim 3 of the present invention, 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 of the arranged rectangular parallelepipeds have a non-parallel relationship, and it also means that even if a part of the arranged rectangular parallelepipeds has a parallel relationship, there is a large number of non-parallel relationships.

The minute projections of the present invention may be polygonal prisms other than rectangular parallelepipeds. However, in the case of the rectangular parallelepipeds targeted in the above description, their side surfaces form 90 ° with each other.
° Every time it rotates, the same situation occurs. However, in the case of a rectangular parallelepiped, the opposite side surfaces thereof are parallel to each other, and therefore, in the prevention of moire fringe generation, 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, three types of intersecting lines are considered, and in the case of a pentagonal prism, there are five types of intersection lines, which are more than in the case of a rectangular parallelepiped. Therefore, the number of conditions for generating moire fringes increases, and the degree of freedom in design decreases. Of course, even if it is a quadrangular prism, adjacent side faces are not at right angles, and in a free quadrangular prism, there are four types of intersecting lines to consider, and at this point, the opposing side faces are parallel, the bottom face is a parallelogram, Even with a rectangular prism having a diamond shape, it is possible to prevent the generation of moire fringes in the same manner as a rectangular parallelepiped. However, from the viewpoint of ease of manufacturing, the rectangular parallelepiped is superior to the parallelogrammatic and rhomboidal rectangular prisms. In addition, when the intersection line derived from the side surface does not form a straight line, there are n prisms in which n is infinity, that is, a cylinder whose side surface is a curved surface, an elliptic cylinder, and the like. For example, if the original film for making a group of minute projections is performed by a parallel scanning method such as a scanner, since the projections are minute, a contour such as a circle that forms a side surface that is not parallel or at right angles to the scanning line is notched. It can be done, but the smooth side of the original cylinder cannot be done.

As a method of randomly arranging the minute protrusions, X of a predetermined area corresponding to the entire surface of the lens sheet is used.
Random numbers may be used in the Y plane to generate X and Y coordinates for arranging the minute protrusions. In FIG. 5A, 22 is a random coordinate point on which the minute protrusion 21 thus obtained is to be formed. Here, if the minute protrusions having a finite size are arranged too close to each other in the coordinate points 22 and are adjacent to each other, the minute protrusions come into contact with each other and overlap as shown in FIG. 6A. It is possible that part 23 can be created. In addition, in FIG. 6A, the dotted line is a virtual line for clearly indicating the overlapping portion. In such a case, if the overlapping shapes are left as they are, the fine protrusions may become large and may be visible. Therefore, as one solution, it is preferable to set the height H of the micro-projections in the overlapping portion to zero as shown in FIG. 6B. In this way, it is possible to prevent the adjacent and overlapping minute projections from fusing together and widening the crown of the minute projections. Thereby, even if the small protrusions overlap each other, it is possible to prevent the small protrusions from becoming large and visible. FIG. 5 (b) shows a state in which the overlapping portion remains as it is, and FIG. 5 (c) shows a minute projection group in a state where the height H of the overlapping portion is set to zero by processing as described above.

The moire fringes generated due to the relationship between the minute projections, the constituent surface, and the constituent surface of the unit lens are all arranged in the same direction when the minute projections are arranged.
This is because all the side surfaces formed by the minute protrusions are aligned to define a recognizable intersecting line, and a relationship between this intersecting line and the intersecting line derived from the surface formed by the unit lenses occurs. However, even if all the micro-protrusions have the same shape, when the micro-protrusions are arranged in random directions, that is, in FIG. 4B, all the micro-protrusions have the same orientation. However, if the Z-axis direction perpendicular to the XY plane is randomly rotated and arranged, the intersecting lines obtained from the surfaces formed by the side surfaces of the respective minute protrusions are distributed in arbitrary directions. And the line of intersection defined at a specific angle is eliminated, and even in this case, the generation of moire fringes can be prevented. However, in terms of easiness in manufacturing the lens sheet, it is better to make the same direction.

In this respect, a cylinder, an elliptic cylinder, etc. are excellent. However, as described above, there is a difficulty in manufacturing a side surface having a smooth curved surface. In addition, in the method of setting the height H to zero as an example of a measure against the case where adjacent minute protrusions overlap each other when randomly arranged, a sharp cross-sectional shape can be formed at the contact portion, which is also manufactured. It becomes the upper difficulty. However, without taking the method of setting the height H to zero, the X coordinate value and the Y coordinate value of the X and Y coordinates for arranging the minute protrusions, which are obtained by a random number, are larger than the diameter D of the cylinder if they are not sharp. If a random number is generated (the value part such as the digit below the flaw is rounded), the obtained random coordinate points are
Since the distance is always larger than the diameter D, even if the minute protrusions are arranged at these coordinate points, there is no overlap. Further, as an extension of this method, the minimum adjacent distance can be adjusted by intentionally increasing the flaw.

Further, the distribution density of the fine projections is such that the lens sheet does not bend to form equal-thickness interference fringes, and even if the lens sheet has a certain degree of rigidity, the lower light guide body is formed. The distance is set appropriately so that a uniform gap can be secured between the lens and the lens sheet, and due to a slight difference in the gap, uniform thickness interference fringes cannot be formed. The distribution density when the cross-sectional area of the minute protrusions is assumed to be zero, that is, the numerical distribution density of arranging the minute protrusions, is particularly small when the two lens sheets are used in an overlapping manner. It is preferable that the average distance d between adjacent protrusions is equal to or less than twice the repeating period p of the unit lens on the surface of the lower lens sheet, that is, d <2p. By designing in this way, the supporting contacts between the minute projections 21 on the back surface of the upper lens sheet and the unit lenses 41 on the front surface of the lower lens sheet that are in contact with each other are bent, and the intervals between the upper and lower lens sheets become uneven. It is possible to prevent equal thickness interference fringes from occurring and the distance between the upper and lower lens sheets to be less than the wavelength of the light source. The average distance d is more preferably d <0.5p.

On the other hand, when the cross-sectional area of the minute projections is evaluated to be finite, the distribution density capable of preventing the equal-thickness interference fringes even when the lens sheet is bent is such that the lens sheet 1 and the light guide body 51 face each other. Area ratio Sr (= Sp / St × 1) of the total sum Sp of the sectional areas of the protrusions to the total area St
00) is preferably about 0.01 to 60%. It is preferable that it functions as a minimum as a spacer function, but it is necessary to some extent from the viewpoint of the bending of the lens sheet, and when it is combined with the light guide described below to form a surface light source, the surface distribution of brightness is To some extent, it is necessary to make the temperature uniform.

In order to consider the factors related to the surface distribution of luminance, the area ratio R, which is inversely related to the above-described area ratio Sr, will be used. The total area Sa of the areas of the voids 9 where the minute protrusions 21 do not come into close contact with the surface of the light guide body 51 and are spaced by a wavelength or more is the total area St where the lens sheet 1 and the light guide body 51 face each other. Area ratio R
[%] Is represented by [Formula 3]. R = Sa / St × 100 [Formula 3] Therefore, the area ratio R is the above 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 the surface, the utilization efficiency of light energy, the size of the light guide, and the like. Normally, the area ratio R is 80%.
As described above, it is necessary to set it to 90% or more, more preferably. The reason for this is that when a smooth light guide surface 55 having a surface roughness equal to or less than the wavelength of light as shown in FIG. 21 and the front surface (back surface) of the lens sheet 1 are brought into close contact with each other, as shown in FIG.
Most of the input light that enters the light guide 51 from the light source 52 is emitted without being totally reflected in a region from the side end portion on the light source side to the distance y (the light guide surface has a critical angle or more). Even if the light enters, the light does not undergo total reflection at that portion and the light enters the unit lens.) Therefore, the brightness suddenly decreases and the light becomes darker at a position farther than y. Then, the percentage of the length y of the light emitting portion with respect to the total length Y of the light guide 51 in the light propagation direction is 10 to 20% when actually measured. Therefore, in order to evenly distribute the amount of light energy incident on the light guide from the light source to the entire length Y, most of the light is emitted in the area of the length y of the light guide surface 55, that is, about 100% of the light is emitted. 10 to 2 out of the incident light coming to the region portion of length y
It is necessary that 0% is transmitted and emitted, and the remaining 90 to 80% of light is totally reflected. In this case, R is 80 to 90% (Sr = 10) because it is approximated by (total reflected light amount / total incident light amount) ≈Sa / St = R.
~ 20%) is required. Further, since it can be similarly approximated at a position 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 projections cannot be maintained at the wavelength of light or more due to the bending of the lens sheet as described above, which is not preferable. Therefore, the upper limit of R is preferably 99.99% or less (Sr ≧ 0.01%).

By providing the above-mentioned specific minute projection group on one surface of the lens sheet, equal-thickness interference fringes and moire fringes are prevented without increasing the number of light rays emitted outside the viewing angle and decreasing the brightness. Further, it is possible to provide an excellent lens sheet that can distribute output light with a uniform surface distribution over the entire surface of the light guide.

As shown in FIGS. 9A and 9B, the lens sheet 1 of the present invention is provided with a minute projection group 2 composed of a large number of minute projections 21 on one surface of a flat transparent substrate 3 and the other. A three-layer structure in which the lens array 4 is provided on the surface of
As shown in FIG. 7, the lens array 4 and the transparent base material 3 are integrally formed with the minute protrusion group 2 to form a two-layer structure, or the lens array 4, the transparent base material 3 and the minute protrusion group 2 shown in FIG. A single layer structure in which the persons are integrated may be used. In such an integrated lens sheet, the part of the transparent base material is not always necessary, and there may be one having a group of minute projections on the back surface of the lens array, and it is considered that these integrated parts are the transparent base material. You can also In FIG. 9B, the microprojection base 32, which is transparent and is integrated with the microprojection group 2 and has a smooth front surface (the back surface side as a lens sheet) except the microprojections 21, is a transparent substrate. The entire surface of one side of the material 3 is covered. This is because such a structure 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 is the transparent substrate 3
Can be considered part of the.

The transparent substrate, the minute protrusions and the lens array are formed of a transparent material. The transparency of such materials may be colored transparent or translucent depending on the application. Further, since the size of the minute protrusions is minute, the minute protrusions may be opaque so that they cannot be visually observed, but transparent is preferable.

Examples of transparent materials for forming these transparent substrates, lens arrays and minute protrusions include polyester resins such as polyethylene terephthalate and polybutylene terephthalate, acrylic resins such as polymethylmethacrylate, polycarbonate resins, polystyrene resins and polymethyl. A thermoplastic resin such as a pentene resin, or an ionizing radiation curable resin composed of an oligomer such as polyester acrylate, urethane acrylate, epoxy acrylate and / or a monomer such as an acrylate, is cured by ionizing radiation such as ultraviolet rays or electron beams. A resin having good transparency is used as the resin or the like. Such a resin usually has a refractive index of about 1.49 to 1.55. In addition to resins, glass, ceramics and the like can be used as long as they have good transparency.

The total thickness of the lens sheet is usually 20 to
It is about 1000 μm.

As the lens arrangement of the lens sheet of the present invention, for example, as shown in FIG. 10, unit lenses 41 of a triangular prism as a columnar body are arranged adjacent to each other with their long axis (ridge line) directions parallel to the one-dimensional direction. A columnar lens group (a lenticular lens in a broad sense) or a fly-eye lens in which a large number of projecting unit lenses 21 each having an independent periphery such as a hemisphere are arranged in a two-dimensional direction is used. obtain. Here, as the sectional shape of the unit lens, as shown in FIGS. 11 and 12, a continuous smooth curve such as a circle, an ellipse, a cardioid, a Rankine egg shape, a cycloid, or an involute curve, or as shown in FIG. Part or all of a polygon such as a triangle, a quadrangle, or a hexagon may be used. Further, as the unit lens arranged in the two-dimensional direction, a pyramid lens can be used as shown in FIG. These unit lenses may be convex lenses as shown in FIGS. 10, 11, 13, and 14 or concave lenses as shown in FIG. 12, among which,
Design, ease of manufacture, light collection, light diffusion characteristics (half-value angle, sidelobe light (light emitted in a direction that is largely oblique to the normal to the exit surface of the lens sheet), half-value angle It is a cylinder or an elliptic cylinder in terms of the isotropic brightness of the inside, the brightness in the normal direction, and the like. In particular, an elliptic cylinder having a major axis in the direction normal to the surface light source is preferable in terms of high brightness. In addition, in each of the drawings for explaining the shape of the unit lens described above, the illustration of the minute protrusions is omitted.

As a method for producing a lens sheet, in order to obtain a single-layer lens sheet as shown in FIG. 7, for example, a known thermoplastic resin as disclosed in JP-A-56-157310 is used. In the pressing method or the injection molding method, it is possible to use a mold having the lens array 4, the microprojection group 2 and an inverted concavo-convex shape, or cast molding of a curable resin by ultraviolet rays or heat.

Further, as another manufacturing method, for example, as disclosed in Japanese Patent Laid-Open No. 5-1699015,
A roll intaglio having concave portions (correctly, concave and convex shapes) opposite to the desired lens array shape is filled with ionizing radiation curable resin liquid, and a transparent base material sheet is stacked on top of this, and UV or Irradiating electron beam or other ionizing radiation from the transparent substrate sheet side (when the roll intaglio is transparent such as glass, it can also be applied from the inside of the roll intaglio) to cure the ionizing radiation-curable resin liquid, and then the transparent substrate. By peeling the material sheet together with the cured resin from the roll intaglio, the cured ionizing radiation-curable resin liquid becomes the lens array 4 of the desired shape, and the intermediate sheet of the lens sheet formed on the transparent base material sheet is obtained. can get. Then, the same operation is performed on the back surface of the intermediate sheet with a roll intaglio having recesses having a shape opposite to the desired shape of the micro projections. A lens sheet of the present invention having a lens array is obtained. In addition, you may form a microprojection group ahead of a lens array.

FIG. 19 is a conceptual diagram (cross-sectional view) showing an example of a manufacturing apparatus that can be used in the manufacturing method using such an ionizing radiation curable resin. In the manufacturing apparatus of FIG.
Is a roll intaglio provided with a recess 72 having a shape opposite to that of the microprojection group 2 (or lens array 4) to be formed (however, the recess is shown in a rectangular cross section for simplification of the drawing. It is rotating in the direction of the arrow around the core),
73 is an ionizing radiation curable resin liquid, 3 is a sheet-shaped transparent base material, 74 is a pressing roll that contacts the roll intaglio plate and presses the transparent base material 3 against the roll intaglio plate 71, and 75 supports running of the transparent base material 3. Guide rolls, 76 peeling rolls, 77a and 77b are ionizing radiation irradiation devices for curing the ionizing radiation curable resin liquid, and 21 are minute particles formed on the transparent substrate 3 as a cured product of the ionizing radiation curable resin liquid. The protrusions 1 are intermediate sheets 11 and 78 of the lens sheet having the minute protrusions 21 (or the lens array 4) on the transparent substrate 3, and the coating devices of the ionizing radiation curable resin liquid.

In the above manufacturing method, as the sheet-shaped transparent substrate, for example, a sheet made of polyester resin such as polyethylene terephthalate or polybutylene terephthalate can be used. The thickness is determined depending on workability such as handling of the device, but usually 10 to 100
It is about 0 μm.

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

As for the two-layer lens sheet as shown in FIG. 8, first, an intermediate sheet having a lens array is prepared by the above-mentioned press molding, injection molding, cast molding or the like, and then the above-mentioned ionization is carried out. It can be obtained by forming minute projections by a method using a radiation curable resin and a roll intaglio or plano intaglio.

Next, the edge light type surface light source 10 of the present invention.
0 can be obtained by arranging and mounting the above-mentioned lens sheet of the present invention above the light emitting surface of a surface light source that is conventionally known and includes a light source, a light guide, a reflection layer, and the like. The edge light type surface light source of the present invention is, as shown in a perspective view of one embodiment thereof in FIG. 16, at least a light guide body 51 and a linear or linear shape installed adjacent to at least one position of a side end surface thereof. It is composed of a point light source 52, a light reflection layer 53 on the back surface of the light guide 51, and the lens sheet 1 of the present invention described above. In addition, a lamp house 54 having an inner reflecting surface is usually provided around the light source 52. Usually, a transparent plate of about 1 to 10 mm such as acrylic resin or polycarbonate resin is used for the light guide body 51, a linear light source such as a cold cathode tube is used for the light source 52, and light is used for the light reflection layer 53. To diffuse and reflect, a metal film is formed by vapor deposition or plating after white painting or sandblasting. In addition, the arrangement of the light diffusion dot pattern printed in white may be adjusted to make the amount of light emitted from the light emitting surface uniform. In addition, the light guide 51 and the lens sheet 1
In some cases, a light diffusing sheet may be disposed between and to diffuse the light uniformly and make the light diffusing dot pattern of the light reflecting layer 53 invisible.

When the lens sheet is mounted on the surface light source, only one sheet may be used, but in the case of a columnar lens, in order to control the light diffusion angle in two directions (vertical direction and horizontal direction), as shown in FIG. The lens sheets may be laminated so that the ridge lines of the unit lenses intersect (orthogonally in the figure). In this case, the direction of the surface having the lens array (hereinafter referred to as the “lens surface”) is
It is optimal that the two sheets have the same orientation because the light transmittance is high and the moire fringes between the lens surface of the lower lens sheet and the minute protrusions on the back surface of the upper lens sheet can be prevented. Of course, the lens surfaces of the two lens sheets may be opposed to each other.

Also, two lens sheets are used, and the light diffusion sheet 56 described above is provided between the lens sheet and the light guide 51.
If a sheet having unevenness on the front and back sides of the wavelength of the light of the light source or more is used, the minute projections are not required on the back surface of the lower lens sheet. This is because the unevenness on the front and back of the light diffusion sheet has a function of preventing optical adhesion. With such a configuration, two lens sheets are used, but one can use the conventional back flat lens sheet 19, which is advantageous in terms of cost. Further, while the light diffusing sheet provides the effect of uniformly diffusing light, the light emitted outside the viewing angle generally tends to increase, but the light diffusing dot pattern of the light reflecting layer on the back surface of the light guide body Has the effect of invisibility. Such an edge light type surface light source 101 is shown in FIG.

The back surface flat lens sheet has a lens array in which unit lenses are arrayed in a one-dimensional or two-dimensional direction on the front surface side of a transparent base material, and the back surface side is a smooth surface without minute protrusions. Which is the lens sheet 1 of the present invention.
On the other hand, it has a configuration in which there is no microprojection group 2 on the back surface, and the same material and manufacturing method as the lens sheet of the present invention can be applied. Further, the light diffusing sheet has uneven surfaces on the front and back surfaces in order to prevent the light diffusing sheet from sticking to the smooth surface of the light guide surface and the lower lens sheet back surface. On the other hand, the light diffusing action is performed by each light powder agent on the uneven surface or inside the light diffusing 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 is formed. An example is a product obtained by embossing fine irregularities such as grain.

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

[0053]

According to the lens sheet of the present invention, since there are minute projections on the back surface, when two lens sheets are stacked or when they are stacked on the light emitting surface of the light guide surface as a surface light source,
Adhesion of the back surface of the lens sheet is prevented, and generation of equal-thickness interference fringes is suppressed. Further, when the lens sheet is placed on the light guide body so that the back surface of the lens sheet (the surface on which the minute protrusions are formed) faces the light guide body, the light due to total reflection on the light guide surface is It is possible to obtain emitted light having a uniform luminance distribution over the entire light emitting surface without hindering the distribution. Further, since the respective minute protrusions forming the minute protrusion group are arranged at random positions, generation of moire fringes due to interference with the lens arrangement and the arrangement of the pixels of the liquid crystal display element is suppressed. Also, by making the micro-projections a rectangular parallelepiped, manufacturing becomes easier,
Further, the arrangement of the rectangular parallelepiped has a specific relationship between the side surface and the surface of the unit lens forming the lens array, so that the occurrence of moire fringes due to the relationship with the lens array is suppressed. According to the edge light type surface light source of the present invention, since the lens sheet as described above is used, light energy is effectively used. Further, according to the transmissive display of the present invention, since such a surface light source is used, a bright display can be obtained.

[0054]

【Example】

<< Example 1 >> A transparent biaxially stretched polyethylene terephthalate film having a thickness of 100 μm was used as a transparent substrate by a manufacturing apparatus as shown in FIG. 19, and an ultraviolet curable ink containing a urethane acrylate prepolymer as a main component was used.
An intermediate sheet having a lens array in which an isosceles triangular prismatic lens having a cross-sectional shape of apex angle β (see FIG. 10) of 100 ° was used as a unit lens was prepared. Next, using the same apparatus as shown in FIG. 19, the height H is 10 μm, the length of one side a of the base is 125 μm, and the length of the other side of the base is 125 μm. A rectangular parallelepiped having a length b of 125 μm was used as a minute protrusion to form a group of minute protrusions randomly arranged to obtain a lens sheet of the present invention. In addition, FIG. 19 for randomly arranging the minute protrusions
For the roll intaglio, image data was created by computer image processing, and as shown in FIGS. 5 and 6, the minute protrusions were black, and the overlapping portions were white (zero density). Then, using a scanner for printing plate making from this image data, it was exposed to a silver salt photosensitive film for plate making to make an original film (black in the rectangle of the micro-projections, transparent in the overlapping part and parts other than the rectangle) . Then, a photosensitive resist is applied to the surface of a cylindrical copper cylinder, and the original film is closely contacted and exposed to light, and developed to remove the resist in the unexposed area (inside the rectangle), and only the exposed area is a cured film. Then, the resist pattern was formed, and the surface of the cylinder was corroded with an aqueous solution of ferric chloride. After that, the resist was removed to prepare a roll intaglio plate in which the rectangular portion became a recess. The printing depth was the same for all rectangles. In addition, the directions of the rectangular parallelepipeds of the small protrusions are all the same,
The line of intersection between the side surface of the rectangular parallelepiped and the horizontal surface of the lens sheet (X 'axis in FIG. 4) and the line of intersection between the constituent surface of the unit lens and the horizontal surface of the lens sheet (X axis in FIG. 4) are parallel. And
The ratio Sr of the cross-sectional area of the minute protrusions to the total area is S
It was r = 60 [%].

Example 2 A lens sheet of the present invention was obtained in the same manner as in Example 1 except that the height H of the rectangular parallelepiped was changed to 15 μm.

Example 3 A lens sheet of the present invention was obtained in the same manner as in Example 1 except that the height H of the rectangular parallelepiped was changed to 20 μm.

<Fourth Embodiment> In the first embodiment, the rectangular parallelepiped is arranged by rotating, and all the rectangular parallelepipeds are oriented in the same direction, and the angle α formed by the X ′ axis and the X axis in FIG. 4 is set to 10 °. A lens sheet of the present invention was obtained in the same manner as in Example 1 except for the above.

Comparative Example 1 In Example 1, the intermediate sheet having the lens array formed on the front surface was left as it was, and a lens sheet having no fine irregularities on the rear surface was provided.

Comparative Example 2 In Example 1, after obtaining an intermediate sheet having a lens array formed on its front surface,
A coating liquid prepared by adding 3% by weight of acrylic resin beads having a particle diameter of 2 to 20 μm to a two-component curing type urethane resin was applied at 5 g / m ² by a gravure coating method to obtain a matted lens sheet.

Comparative Example 3 The procedure of Example 1 was repeated except that the cylinder surface was sandblasted with # 80 spherical sand as a roll intaglio plate.
A lens sheet having a matt back surface was obtained.

Table 1 shows the performance of the lens sheets of the above Examples and Comparative Examples. The evaluation criteria are as follows. Adhesion resistance: The case where the back surface of the lens sheet and the other flat plate (light emitting surface of the light guide body) did not come into contact with each other was evaluated as “◯”, and the case where they did occur was evaluated as “x”. The presence or absence of close contact, that is, optical close contact, indicates close contact when the area near the light source on the light emitting surface looks brighter than the other (x), and no contact when the bright area near the light source is not visually observed. It was judged as (○). Equal thickness interference fringes: “O” indicates that no uniform thickness interference fringes occur when one lens sheet is overlaid on another flat plate and visually observed.
When it occurred, it was designated as "x". Moire fringes: One lens sheet was visually observed, and when the moire fringes between the minute protrusions and the lens array did not occur, the mark was “◯”, and when they occurred, the mark was “x”. Luminance rate: The portions other than the lens sheet are the same edge light type surface light source, and in order to replace only the lens sheet on the surface of the light guide, the lens sheet of each of the above-mentioned examples and comparative examples,
The lens array side is placed facing the output side (outside) of the surface light source, and the variable angle photometer GONI manufactured by Murakami Color Research Laboratory Co., Ltd.
Luminance was measured using an OPOTOMETER. Then, as a reference, the luminance in the normal direction of Comparative Example 1 in which no unevenness is formed on the back surface was set to 100%. Viewing angle: Brightness is 5 with 100% normal direction brightness.
The angle from the normal to 0% (half-value angle) was used. The measurement method is the same as.

[0062]

[Table 1] *: Cannot be measured. The emitted light becomes extremely dark when it is separated from the light source by about 2 cm.

[0063]

Since the lens sheet of the present invention is constructed as described above, when two lens sheets are stacked, there is no close contact between the sheets, and when one sheet is stacked on the light guide of the surface light source. However, there is no close contact with the light guide, and as a result, it is possible to prevent the occurrence of equal-thickness interference fringes. In addition, the amount of light emitted outside the viewing angle is small and the reduction in brightness can be suppressed to a minimum, as compared with the conventional prevention of adhesion by matting. Also,
In the edge light type surface light source of the present invention, since the lens sheet does not adhere to the light emitting surface of the light guide body, the light from the light source can be widely and uniformly distributed in the light guide body, and as a result,
It is possible to make the luminance distribution of the light emitted from the light guide within the light emission surface uniform. The light energy is effectively used and bright, and the light diffusion dot pattern can be made invisible. Further, a large amount of light is emitted in the vicinity of the normal direction of the emission surface, and the amount of light emitted away from the normal direction can also be reduced as compared with the isotropic diffusive sheet. Further, the transmissive display according to the present invention is bright on the entire display surface and is uniform and bright depending on the viewing angle.

[Brief description of drawings]

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

FIG. 2 is a perspective view of an example of the shape of minute protrusions of the lens sheet of the present invention.

FIG. 3 is an enlarged perspective view illustrating a minute projection provided on a lens sheet in an enlarged manner.

FIG. 4 is an explanatory view in which a side surface of a minute protrusion and a constituent surface of a lens array are not parallel to each other.

FIG. 5 is an explanatory view of a process of forming randomly arranged minute protrusions.

FIG. 6 is an explanatory diagram of a shape process when minute protrusions overlap each other.

FIG. 7 is a vertical cross-sectional view of an example (single layer) of the layer structure of the lens sheet of the present invention.

FIG. 8 is a vertical cross-sectional view of another example (two layers) of the layer structure of the lens sheet of the present invention.

FIG. 9 is a vertical cross-sectional view of another example (three layers) of the layer structure of the lens sheet of the present invention.

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

FIG. 11 is a perspective view of another example (elliptical cylinder lens) of the lens arrangement of the lens sheet of the present invention.

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

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

FIG. 14 is a perspective view of another example (pyramidal lens) of the lens arrangement of the lens sheet of the present invention.

FIG. 15 is a perspective view illustrating a two-sheet structure of the lens sheet of the present invention.

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

FIG. 17 is a perspective view of an embodiment of a transmissive display body of the present invention.

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

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

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

FIG. 21 is an explanatory diagram showing the behavior of a light ray that travels by a tunnel effect to a lens sheet that is separated from the light guide body by a minute distance.

FIG. 22 is an explanatory diagram in which the contact portion between the minute protrusions of the lens sheet of the present invention and the surface of the light guide body is involved in the distribution of light inside the light guide body.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Lens sheet 11 Intermediate sheet of lens sheet 19 Rear surface lens sheet (conventional lens sheet) 2 Microprojection group 21 Microprojection 22 Coordinate points forming microprojection 23 Overlapping portion of microprojection 3 Transparent base material 31 Transparent base material sheet 32 microprojection base 4 lens array 41 unit lens 42 slope of triangular prism unit lens 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 71 Roll Intaglio 72 Concave 73 Ionizing Radiation Curable Resin Liquid 74 Pressing Roll 75 Guide Roll 76 Peeling Roll 77a, 77b Ionizing Radiation Irradiating Device 78 Coating Device 9 Voids Secured by Micro-Protrusions 100 Surface Light Source 101 Surface Light Source (Lens Sheet Two) 200 transmissive display n ₁ , n ₂ 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 electromagnetic field y length of light emitting part near light source of light guide Y total length of light guide in light propagation direction α The angle formed by the line of intersection between the side surface of the minute protrusion and the horizontal surface of the lens sheet and the line of intersection between the surface of the unit lens and the horizontal surface of the lens sheet. β The vertical angle of the triangular prism lens. λ Wavelength of light θ Incident angle θ ′ Exit angle θc Critical angle

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Michiko Takeuchi 1-1-1, Ichigayaka-cho, Shinjuku-ku, Tokyo Dai Nippon Printing Co., Ltd.

Claims (7)

[Claims] 1. A transparent base material has a lens array formed by arranging unit lenses in a one-dimensional or two-dimensional direction on the front surface side, and has a polygonal column shape on the back surface side, and each side has a length of the light source light. A lens sheet comprising a large number of fine protrusions having a wavelength of not less than 500 μm and arranged on the entire surface in a random two-dimensional distribution. 2. The lens sheet according to claim 1, wherein the minute protrusions are rectangular parallelepipeds. 3. An intersection line between a horizontal surface of the lens sheet and a surface forming a unit lens and an intersection line between the horizontal surface and a side surface of each rectangular parallelepiped forming the minute projection group are not parallel to each other. The lens sheet according to claim 2, wherein: 4. A light guide body comprising at least a translucent flat plate, a light source unit provided adjacent to both or one of side end surfaces of the light guide body, and a light provided on the back surface of the light guide body. The 1 or 2 piece which laminated | stacked the reflective layer and the microprojection group on the light emission surface of the said light guide surface toward the light guide surface side.
Or an edge light type surface light source, comprising: 5. The lens sheet is a stack of two lens sheets, and the microprojection group of the lower lens sheet is laminated toward the light guide surface side. Edge light type surface light source. 6. A light-diffusing sheet having a light-emitting surface on the surface of the light guide body, the front and back surfaces of which have projections and depressions of a wavelength of light of a light source or more, and a unit lens on the front surface side of the transparent substrate in one-dimensional or two-dimensional direction. A back surface flat lens sheet having a lens array formed by arraying, the back surface side being a smooth surface without microprojections, and the back surface facing the light guide surface side, and the lens sheet according to claim 1, 2. 5. The edge light type surface light source according to claim 4, wherein, and are arranged in this order. 7. A transmissive display body, comprising the edge light type surface light source according to claim 4, 5 or 6 as a back light source of a translucent display body.