JP3606636B2 - Lens sheet, surface light source, and display device - Google Patents

Lens sheet, surface light source, and display device Download PDF

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Publication number
JP3606636B2
JP3606636B2 JP14042095A JP14042095A JP3606636B2 JP 3606636 B2 JP3606636 B2 JP 3606636B2 JP 14042095 A JP14042095 A JP 14042095A JP 14042095 A JP14042095 A JP 14042095A JP 3606636 B2 JP3606636 B2 JP 3606636B2
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Prior art keywords
light
surface
lens
light source
lens sheet
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JPH08335044A (en
Inventor
暢 増淵
理加 安▲藤▼
久憲 石田
俊和 西尾
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大日本印刷株式会社
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Description

[0001]
[Industrial application fields]
The present invention relates to a lens sheet having a lens array layer on the surface, a direct type or edge light type surface light source using the lens sheet, and a liquid crystal display device, illumination advertisement, traffic sign, etc. using the surface light source. It relates to the device.
[0002]
[Prior art]
FIG. 13 is a schematic diagram showing a conventional example of a surface light source.
In the surface light source 100A, the lens sheet 101 is optically adhered onto the light guide plate 102, and the light source 103 is provided on the side surface of the light guide plate 102 (Japanese Utility Model Laid-Open No. 4-107237, Japanese Patent Laid-Open No. 5-127159, etc.). .
The lens sheet 101 typically has a lens array layer in a linear array of isosceles triangular prisms having an apex angle of 90 °.
[0003]
In the surface light source 100B, a high-haze light diffusing layer 104 is disposed between the lens sheet 101 and the light guide plate 102 (JP-A-6-18707, JP-A-6-301035, etc.). The light diffusing layer 104 has minute protrusions 104b on the back surface.
[0004]
The surface light source 100C is provided with a spacer protrusion 101c having almost no haze and light diffusibility on the back surface of the lens sheet 101C, and a high haze light diffusive layer 104 is disposed on the observation side of the lens sheet 101. (Japanese Patent Laid-Open No. 6-102506).
[0005]
[Problems to be solved by the invention]
The surface light source 100A described above has the following problems.
{Circle around (1)} Since only the diffusion of the prism of the lens array layer of the lens sheet 101 is performed, a moderately wide diffusion angle and an equality of luminance within the diffusion angle cannot be obtained.
{Circle around (2)} Since the lens sheet 101 and the light guide plate 102 are in optical contact, light source light is not propagated to the entire region of the light guide plate due to total light reflection at the light guide plate surface and the lens sheet interface. Therefore, although the light energy loss of the light source light 103 is relatively small, there is a problem that it concentrates in the vicinity of the light source and becomes non-uniform. Therefore, when the light source 103 is separated from the light source 103 to some extent, the luminance is rapidly attenuated, and high luminance with uniform distribution cannot be obtained over the entire surface of the light guide plate.
(3) Since the back surface of the light guide plate 102 is visible, the light diffusion dot pattern on the back surface of the light guide plate 102 is visually recognized.
(4) A thin-film air layer is formed between the lens sheet 101 and the light guide plate 102 (and between each sheet when there are two or more lens sheets). There was a problem.
[0006]
In the surface light source 100B, the light source light is output from the surface of the light guide plate and isotropically diffused and transmitted by the light diffusing layer 104, and then condensed by the lens arrangement layer of the lens sheet 101. A uniform luminance angle distribution (orientation characteristic) within the viewing angle can be obtained (solving (1) above).
In addition, since the image can be blurred and scattered by the haze (cloudiness value) of the light diffusing layer 104, the light diffusing dot pattern on the back surface of the light guide plate 104 can be made invisible (solving (3) above).
Furthermore, light is totally reflected on the surface of the light guide plate 102 by the minute protrusions on the back surface of the lens sheet 101 (the back surface of the light diffusing layer), and is uniformly distributed in the light guide plate 102, depending on the distance from the light source 103. Attenuation of the output light is relatively small (solving (4) above).
However, since the light source light is diffused at a wide angle by the light diffusing layer 104 and then enters the lens sheet 101, a part of the diffused light is not input to the lens sheet 101, and the light input loss is large and the entire surface is uniform. However, there arises a new problem that the luminance is insufficient.
[0007]
Since the surface light source 100C is provided with the light diffusing layer 104, the problem (3) is solved.
Further, since the spacer protrusion 101a is provided on the back surface of the lens sheet 101C, the thin film air layer is eliminated, and the occurrence of equal thickness interference fringes can be prevented (solving (4) above). Furthermore, since the optical contact between the rear surface of the lens sheet and the surface of the light guide plate is lost, the light is propagated to the entire light guide plate by the total reflection of light on the surface of the light guide plate, thereby solving the problem (2).
However, since the light diffusing layer 104 is provided on the most observation side of the lens sheet 101, the light once condensed once again diffuses, causing a problem that the viewing angle is too wide. The problem is not solved.
[0008]
The object of the present invention is to solve all the above-mentioned problems,
(1) A moderately wide diffusion angle and an isotropic direction of luminance within the diffusion angle are obtained.
(2) Low light energy loss of light source light, that is, higher brightness with respect to limited constant light source light energy,
(3) Enabling invisibility (in the case of edge light type) of the light diffusion dot pattern on the back of the light guide plate,
(4) Prevent attenuation of output light due to the distance from the light source (for edge light type),
(5) Moreover, it is possible to prevent equal thickness interference fringes between the light guide plate / lens sheet or between the lens sheet / lens sheet.
A lens sheet, a surface light source, and a display device are provided.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the invention of claim 1 includes a light-transmitting base sheet, a light-transmitting diffusion layer stacked on the surface of the base sheet, and a stack on the surface of the light-transmitting diffusion layer. A lens sheet comprising the lens array layer, wherein the base sheet has a smooth back surface in which the average roughness and the average interval of the irregularities are less than the maximum wavelength of the light source light spectrum, and the light transmission diffusion The layer has a refractive index different from that of the lens arrangement layer, and has an average roughness and an average interval of minute irregularities having a maximum wavelength of the light source light spectrum of 200 μm or less. The interface between the light transmission diffusion layer and the lens arrangement layer The lens array layer is made of a light transmissive material, and has a concave or convex lens shape arranged in a large number in one or two dimensions on the surface.
[0010]
The invention according to claim 2 is the lens sheet according to claim 1, characterized in that the base sheet has a height not less than the wavelength of the light source light and fine protrusions of 200 μm or less scattered on the back surface. Yes.
[0011]
According to a third aspect of the present invention, there is provided a light guide composed of a light-transmitting flat plate or a rectangular parallelepiped cavity, and a point-like or linear light source provided adjacent to at least one side surface of the side end face of the light guide. The lens sheet according to claim 1 or 2 laminated on a surface of the light guide.
[0012]
The invention according to claim 4 is the invention according to claim 1 or claim 1 that covers at least one point-like or linear light source, a light source housing that surrounds the light source and has one surface as an opening, and covers the opening. And a lens sheet described in item 2 above.
[0013]
The invention of claim 5 includes a transmissive display element, and the surface light source according to claim 3 or 4 provided on the back surface of the display element.
[0014]
[Action]
According to invention of Claim 1, the light from a light source is first entered from the back surface of a base material sheet. Since the back surface of the base sheet is a smooth surface with uneven steps that are less than or equal to the maximum wavelength of the light source light, loss (input loss) due to tangential diffusion and deviation of light input to the lens sheet can be reduced. .
Next, the light transmitted through the base sheet is input into the light transmission diffusion layer and is uniformly transmitted and diffused, so that the distribution in the luminance diffusion angle and the light exit surface can be made uniform.
Furthermore, after the light is diffused and diffused by the light transmissive diffusion layer, the light is again converged and output within a predetermined angle by the lens arrangement layer, so that the light diffusion angle can be concentrated within an appropriate angle. .
Therefore, the problems {circle around (1)} and {circle around (3)} of the above-described conventional technology can be solved.
In addition, the haze of the light transmissive diffusion layer allows the light diffusion dot pattern on the back surface of the light guide plate to be invisible (in the case of the edge light type). When the above lens sheets are used in an overlapping manner, it is possible to make invisible interference fringes generated between the lens sheets. Therefore, the problem (4) is solved.
[0015]
According to the second aspect of the present invention, since the minute projections serving as spacers are provided in a discrete distribution on the back surface of the base material sheet while leaving at least partially a smooth light input surface, the light guide plate Can be prevented from being integrated by optical contact between the lens sheet and the lens sheet, and equal thickness interference due to minute gaps between the lens sheets and between the lens sheet and the light guide plate can be prevented.
Therefore, it is possible to prevent the light distribution of the output light with a uniform surface distribution over the entire surface of the light guide plate and the equal thickness interference fringes due to the total reflection of the surface of the light guide plate. ▼ can be solved.
In addition, although the minute protrusions serve as spacers, there is almost no light diffusing effect, and no loss occurs due to light dissipation before entering the lens sheet. Therefore, unlike the case of the conventional surface light source 100B, the object (2) and the objects (4) and (5) can be achieved at the same time.
[0016]
【Example】
(First embodiment of lens sheet)
Hereinafter, the present invention will be described in more detail with reference to the drawings.
FIG. 1 is a perspective view showing a first embodiment of a lens sheet according to the present invention.
The lens sheet 10 of the first embodiment includes a transparent base sheet 11, a light transmission diffusion layer 12 stacked on the surface of the base sheet 11, and a lens arrangement layer 13 stacked on the surface of the light transmission diffusion layer 12. It has.
[0017]
The transparent substrate sheet 11 is formed from a translucent substrate. The translucent base material is described in [0008] and [0009] of JP-A-6-324205 filed by the applicant of the present application, and therefore detailed description thereof is omitted here.
The transparent base sheet 11 of this example has an average roughness of unevenness (elevation difference between bump height and valley height, level difference) Δz. 1 Has a smooth back surface (surface opposite to the lens array layer 13) 11a having a surface roughness equal to or less than the maximum wavelength λmax of the light source light spectrum.
This average roughness Δz 1 Is about 0.8 μm in the case of a normal white light source. Roughness average roughness Δz 1 Can be evaluated by an index obtained by averaging the difference in elevation between the concave portion and the convex portion, and can be suitably evaluated by, for example, a ten-point average roughness (Rz) according to a regulation based on JIS-B-0601.
This step Δz 1 When the wavelength exceeds the maximum wavelength λmax of the light source light spectrum, a part of the incident light is diffusely transmitted and a part is diffusely reflected, which is not preferable because the incident light is lost when entering the lens sheet 10.
In addition, in order to distinguish from the wavelength Λ of external light described later, the wavelength of the output light of the light source of the surface light source (for example, 43 in FIG. 12) is expressed by a small letter λ. Further, the average interval ΔS of the unevenness of the back surface 11a 1 For the same reason, the maximum wavelength of the light source light spectrum is set to be less than the maximum wavelength. ΔS 1 Is evaluated by, for example, the ISO standard average interval Sm. Δz like this 1 And ΔS 1 Can be obtained by applying a known precision finishing method for optical parts such as lenses.
[0018]
FIG. 2 is a schematic diagram illustrating a minute step on the back surface of the lens sheet according to the first example. FIG. 2A shows an uneven step Δz on the back surface 11 a of the base sheet 11. 1 Is smaller than the maximum wavelength λmax of the light source light spectrum.
The light beam L propagated from the light source is diffusely reflected by the light diffusive and reflective dot pattern 42a of the light guide plate 41, and the light beam L incident on the surface of the light guide plate at a critical angle or less. 21 ~ Ray L 22 In this range, the light enters the substrate sheet 11 through the gap A.
Where ray L 21 Represents the reflection component in the normal direction of the surface of the light guide plate 41, and the light beam L 22 Represents a reflection component in an oblique direction with respect to the normal direction (however, it is incident on the surface of the light guide plate 10 at a angle less than the critical angle).
These incident lights L 21 ~ L 22 Part of the transmitted light L 21T , L 22T Thus, it is transmitted in the direction of the lens array layer 13 and is effectively used. Further, the light beam L reflected on the back surface 11 a of the base sheet 11. 22R Part of the light beam L 22R ' → L 22R'T And sent in the direction of the lens array layer 13.
[0019]
FIG. 2B shows the uneven step Δz on the back surface 11 a of the base sheet 11. 1 Is larger than the maximum wavelength λmax of the light source light spectrum.
Compared with FIG. 2 (A), the light beam L which diffusely transmits or diffuses and reflects in a direction almost parallel to the front surface of the light guide plate 41 and the back surface of the base sheet 11. LOSS Occurs. This ray L LOSS Does not reach the direction of the upper lens array layer 13 and is dissipated, resulting in a loss of energy of the light source light. That is, light that has already been lost before entering the lens sheet. In the case of FIG. 2B, the output light energy or the light intensity I is naturally taken as the entire surface light source. N Is also not good because it also decreases.
[0020]
The light transmission diffusion layer 12 is a layer that diffuses while transmitting light. When a parallel light beam is incident on the light transmission diffusion layer 12, the emitted light beam spreads to a predetermined diffusion angle (evaluated by a half-value angle or the like).
The light transmission diffusion layer 12 has an uneven roughness average roughness Δz on its surface. 2 And mean interval ΔS 2 Is formed with a micro unevenness group 12a having a wavelength λmax or more of the light source light spectrum.
In addition, the light transmission diffusion layer 12 has a refractive index different from that of the adjacent lens arrangement layer 13, and the light transmission diffusion layer 12 and the lens arrangement layer 13 are not optically integrated. Unevenness is formed.
[0021]
In this case, (a) the entire light-transmitting diffusion layer 12 may be formed of the same material to form a micro-unevenness group 12a on the surface, or (b) transparent fine particles are dispersed in the light-transmitting diffusion layer 12. Then, irregularities may be formed on the surface. (C) Alternatively, the fine unevenness group can be directly formed on the surface of the base sheet.
In the case of (a), the light transmitting and diffusing layer 12 is made of a material having a refraction different from that of the lens array layer 13 among resins such as acrylic, polycarbonate, polystyrene, polyester, epoxy, polyurethane, and peroxyne structure polytungstic acid. Choose the rate one.
The difference in refractive index between the lens array layer 13 and the light transmission diffusion layer 12 is 0.1 or more, more preferably, in order to form an optical interface (discontinuous surface) that sufficiently exhibits a diffusion function in both layers. Is preferably 0.2 or more.
For example, when an acrylic resin having a refractive index of 1.49 is used as the lens array layer 13, polycarbonate, polystyrene, epoxy, or the like having a refractive index of 1.60 is preferably used as the light transmission diffusion layer 12.
As a method of forming the unevenness, after the light transmission diffusion layer 12 is once coated or bonded on the base sheet 11, it is embossed by a known hot press embossing method, or disclosed in JP-A-6-324205 [ The method described in [0010] is preferably used.
Further, when the difference in refractive index between the light transmission diffusion layer 12 and the lens arrangement layer 13 cannot be made large, a substance having a high refractive index or a low refractive index is interposed between the light transmission diffusion layer 12 and the lens arrangement layer 13. A transparent layer may be formed. Examples of such a high refractive index substance include titanium dioxide (refractive index 2.5) and cerium dioxide (refractive index 2.3), and low refractive index substances include magnesium fluoride (refractive index). 1.38), quartz stone (refractive index 1.35), and the like. These layers can be formed on the light transmission diffusion layer 12 or the lens arrangement layer 13 by vacuum deposition, sputtering, or the like.
[0022]
In the case of (b), fine particles of a transparent material having a refractive index different from that of the lens array layer 13 is dispersed. As the shape of the fine particles, spheres, spheroids, polygons, scale-like foil pieces, and the like can be used.
The particle size of the particle size is determined by the average roughness Δz of the fine irregularities 12a on the surface 2 The lower limit is preferably about the maximum wavelength of the light source light spectrum (about 0.8 μm in the case of a normal white light source). The upper limit is about 100 μm, more preferably 60 μm.
Fine particle materials include resins such as acrylic, polycarbonate, polystyrene, epoxy, polyester, glass, calcium carbonate, silica (SiO 2 ), Arnami (Al 2 O 3 ), Quartz stone (AlF 3 ・ 3NaF), magnesium fluoride (MgF) 2 ), Solid particles such as mica, or hollow particles such as resin, glass, and shirasu.
The fine particles are selected from those having a refractive index different from that of the lens array layer 13. Also in this case, it is preferable to use a particle whose refractive index is different from that of the lens array layer 13 by 0.1 or more, more preferably 0.2 or more, as in the case of (a). is there.
In the case of (b), the refractive index of the dispersion medium (binder) in the light transmission diffusive layer 12 may be the same as that of the lens array layer 12, but in order to perform light diffusion transmission more efficiently. In addition, it is preferable to use a dispersion medium different from the lens array layer 13 like the fine particles.
[0023]
The minute unevenness group 12a transmits and diffuses the light incident on the lens sheet 10, thereby making the angular distribution of output light luminance within the diffusion angle of the light output from the lens sheet 10 uniform (isotropic). Further, the distribution of the output light within the light exit surface is made uniform (uniform), and in addition, the light diffusive reflective dot pattern on the back surface of the light guide plate 41 is made invisible by the haze (cloudiness value).
The average roughness Δz of the minute unevenness group 12a 2 And mean interval ΔS 2 Is the above-described Δz 1 , ΔS 1 In the same manner as above, the evaluation is carried out by averaging, but it can be suitably evaluated by the average interval Sm of the ISO standard such as the ten-point average roughness (Rz) defined in JIS-B-0601.
This Δz 2 , ΔS 2 Is preferably greater than or equal to the maximum wavelength λmax of the light source light spectrum. If it is less than λmax, the haze and coherence reduction (phase disturbance) effect due to the light diffusion effect due to the unevenness is lost. In addition, the upper limit value does not exist in particular for the light diffusion effect, but if it is too large, the uniformity of the in-plane distribution of the output light will be poor (rough), and bright spots and unevenness will become conspicuous in the output light. Usually, it is desirable to use at a maximum of about 200 μm or less.
The uneven shape of the fine unevenness group 12a may be a random isotropic shape such as a grain or a satin texture, or uniformly diffuses light within a predetermined angle such as an eyelet lens, a two-dimensional array of pyramid lens arrays, or the like. A microlens array can also be used.
Average interval ΔS between the convex portions (or the concave portions) of the minute unevenness group 12a 2 Is the average roughness Δz 2 It is preferable to set the same level as in the case of light transmission diffusivity and uniformity of output light. The reason for the upper limit and the lower limit for this interval is the same as the average roughness. Between the concave portions (or convex portions) are averaged and evaluated. As an indicator, for example, JIS
B 0601 It can evaluate suitably by Sm prescribed | regulated.
In addition, for evaluation of the light transmission diffusion layer by the level difference of the minute unevenness group, haze (JISK 7015) and total light transmittance (JIS K 7105) are suitable, and the haze is 5 to 80% and the total light transmittance. Is preferably 80% or more. Here, when the haze is less than 5%, the light diffusion effect is lost, and the light diffusion dot pattern of the light guide plate is not invisible. In addition, the spatial coherence of transmitted light is reduced, and the effect of eliminating equal thickness interference fringes is lost. On the other hand, when the haze exceeds 80%, the diffusion angle of the transmitted light becomes too wide, and the luminance within a predetermined angle of the output light is significantly lowered.
[0024]
The lens array layer 13 is made of a light-transmitting material, and has concave or convex lens shapes 13a (unit lenses) arranged in a one-dimensional or two-dimensional array on the surface. As the lens shape 13a, the light exiting the light transmission diffusion layer 12 can be converged within a desired diffusion angle, and if necessary, the output light can be deflected in a desired direction. There is no particular limitation.
[0025]
FIG. 3 is a perspective view illustrating an example of a lens arrangement layer of the lens sheet according to the first example. The unit lens 13a includes an array of convex lenses as shown in FIGS. 3A, 3B, 3E, 3F, 3H, an array of concave lenses as shown in FIG. 3D, or FIG. Any of a hybrid arrangement of concave and convex lenses as in C) may be used.
Further, the unit lenses 13a may be arranged one-dimensionally or two-dimensionally as shown in FIGS. 3A to 3F, or may be non-periodic as shown in FIG. May also be arranged.
[0026]
The unit lens 13a preferably uses a symmetrical arrangement as shown in FIGS. 3A to 3G when the luminance peak of the output light is set to the normal direction of the light exit surface. Further, the unit lens 13a preferably uses a left-right asymmetric arrangement as shown in FIG.
Since the manufacturing method of the lens array is described in [0010] of JP-A-6-324205, detailed description thereof is omitted.
[0027]
The unit lens 13a is inappropriate because its period (or lens interval) and the step between the concave portion and the convex portion are too small because convergence or deflection action as a lens disappears or spectral effect as a diffraction grating appears. If they are too large, the lens shape is conspicuous, and when a display device is mounted on a surface light source, moire fringes with the pixels of the display device are likely to occur, which is inappropriate.
Accordingly, the range that is usually used is preferably about 10 to 200 μm for both the step and the period (or the lens interval).
[0028]
The material of the lens array layer 13 is described in Japanese Patent Laid-Open No. 6-324205 [0008] and will not be described in detail.
[0029]
The light diffusing dot pattern 42a of the light guide plate 41 is described in Japanese Patent Laid-Open No. 6-109925 [0015], FIG. 2 or Japanese Patent Laid-Open No. 6-324205 [0023] (4). Detailed description is omitted.
[0030]
(Lens sheet of the second embodiment)
4 and 5 are perspective views of the second embodiment of the lens sheet according to the present invention as viewed from the front side or the back side.
In the lens sheet 10 </ b> B of the second example, a minute protrusion 11 b is formed on the back surface 11 a of the base sheet 11.
[0031]
The microprotrusions 11b are not for light diffusion, but create an air layer with an appropriate gap between the light guide plate 41 and the lens stacked below to generate uniform interference fringes or the lens sheet 10B and the light guide plate 41. This is to prevent optical close integration with.
However, even when it is used for a direct type surface light source or an edge light type surface light source, only one lens sheet is arranged so that the lens array layer 13 faces the light guide plate 41 side, or When the lens sheet 10B is thick and has a small number of layers and only the periphery of the lens sheet 10 is fixed by the spacer, the lens sheet 10B may be omitted.
[0032]
Even if this microprotrusion 11b has a columnar shape such as a quadrangular prism, a triangular prism, a hexagonal prism, or a cylinder (or an elliptical cylinder) [FIGS. A frustum shape [FIGS. 5 (F) to (I)] such as a table, a truncated cone (or an elliptical truncated cone) may be used.
[0033]
The dimension of the bottom surface of the microprotrusion 11b (usually evaluated by a radius or a diagonal length) is 1 μm or more although it depends on its height H in order to ensure the minimum strength as a spacer. On the other hand, when the thickness is 125 μm or more, particularly exceeding 500 μm, minute projections can be visually observed, or when used for a liquid crystal display element, moire fringes with the pixels are liable to occur.
[0034]
The two-dimensional distribution on the lens sheet surface of the minute projections 11b having the above dimensions is preferably a random distribution. If the microprotrusions are periodically arranged, there is always a unit lens 13a (in most cases, periodically arrayed) of the lens arrangement layer 13 on the opposite surface of the lens sheet. Since they overlap with each other, they appear as moire fringes.
In addition to the arrangement period of the unit lenses 13 a constituting the lens arrangement layer 13, when used as a backlight of a color liquid crystal display element, moire fringes are caused by interference with the arrangement period of pixels of the display element. Easy to appear. Therefore, generation of moire fringes can be prevented by aperiodic arrangement of the microprojections.
[0035]
However, even if the arrangement of the microprotrusions 11b is randomized as described above, the moire fringes have the same type of microprotrusions (for example, if they are trapezoidal) if the shapes of the polygonal columns of the microprotrusions 11b are the same and aligned. Since the side surfaces of the top and bottom surfaces are all in the same direction, the minute side surfaces in the same direction gather together to form a large virtual side surface. This virtual side surface has no periodicity because the microprojections are randomly arranged, but the surface of the unit lenses constituting the lens array may interfere with each other to generate moire fringes.
Therefore, it is preferable to make a certain relationship between the surface constituting the unit lens and the side surface of the minute protrusion.
[0036]
FIG. 6 is a diagram for explaining the prevention of the occurrence of moire fringes.
For example, as shown in FIG. 6A, a case where the lens array layer 13 of the lens sheet 10 is composed of unit lenses 13a of triangular prism lenses will be considered. The exit surface of the lens sheet 10 is a surface parallel to the XY plane, which is a horizontal plane. Note that the normal direction perpendicular to the exit surface is the Z-axis direction (not shown). The surface constituting the unit lens 13a is a slope 13a-1 forming a mountain valley, and the intersection line between this surface (slope) and the horizontal plane is parallel to the X axis (the X axis is the intersection line). The coordinate axes are taken to be parallel).
Strictly speaking, the slope is a finite plane, and there are many horizontal planes depending on how the Z-axis coordinates are taken. The slope and the horizontal plane do not intersect depending on the conditions, but the intersection line here is the plane (slope) It means the line that extends and intersects the horizontal plane. Of course, if the unit lens is a triangular prism and it is arranged in a one-dimensional direction, there is only one kind of intersection line. There may be two or more kinds of intersecting lines derived from the surfaces constituting the lens, and these intersecting lines may not be orthogonal.
[0037]
Next, FIG. 6B shows one intersection line derived from the microprojection group 11b with respect to the XY coordinate axis based on the intersection line derived from the unit lens 13a of the triangular prism lens. As shown, the orthogonal X′-Y ′ coordinate axes are superimposed.
The directions of the microprotrusions 11b (here, rectangular parallelepipeds) are all aligned, and there are two types of intersecting lines between the side surfaces and the horizontal surface of the lens sheet 10, and intersecting lines orthogonal to each other and parallel to the X ′ axis; It is an intersection line parallel to the Y ′ axis. The X ′ axis and the previous X axis form an angle α.
There are many small protrusions, and there are many intersecting lines between the many side surfaces thereof and the horizontal surface of the lens sheet. However, since the directions of the minute protrusions are aligned, the rectangular parallelepiped is represented by the direction of the intersecting lines. In this case, there are two types of intersecting lines orthogonal to each other.
[0038]
If the angle α formed by the X axis and the X ′ axis is zero, they are parallel and moire fringes are likely to occur. However, moire fringes can be prevented by arranging both such that the intersecting line derived from the unit lens and the intersecting line derived from the minute projections are separated by more than 5 °. That is, in the case of a rectangular parallelepiped, the occurrence of moire fringes can be effectively prevented if the angle α is clockwise (clockwise) in the range of 5 to 85 °, more preferably in the range of 10 to 80 °.
Further, the angle α may be in the range of −5 to −85 °, more preferably −10 to −80 ° counterclockwise. In the case of a rectangular parallelepiped, if the angle exceeds 85 °, the angle with respect to the intersection line derived from the target side surface becomes larger, but the relationship with the adjacent side surface (90 ° with respect to the side surface) is parallel. It becomes close to the relationship, and moire fringes are easily generated due to the relationship with the adjacent side surfaces. In this way, the occurrence of moire fringes can be prevented if they are separated from parallel by more than 5 ° in relation to the side surface of the polygonal column.
[0039]
The microprotrusions are formed of, for example, a rectangular parallelepiped, and the intersecting line between the same type of side surface of interest of each rectangular parallelepiped and the horizontal surface of the lens sheet, and the intersecting line between the surface of the unit lens and the horizontal line are 5 ° as described above. It is not necessary to align all the directions of all the microprotrusions (in this case, a rectangular parallelepiped) to be arranged when the angle is defined to be a certain angle. For example, even if the number of 1% of all the microprotrusions is horizontal, it does not have the strength to define the parallel relationship that causes the generation of moire fringes if they are not assembled in adjacent portions. Because.
In this sense, the intersecting line derived from the side surface of each rectangular parallelepiped and the intersecting line derived from the unit lens are not parallel to each other. The meaning of “each rectangular parallelepiped” does not necessarily mean that all arranged rectangular parallelepipeds are nonparallel. It is not limited to having a relationship, and a part of the arranged rectangular parallelepiped includes the meaning that there is a general non-parallel relationship even if there is a parallel relationship.
[0040]
In addition to the rectangular parallelepiped, the microprotrusions may be polygonal columns. However, in the case of the rectangular parallelepiped targeted in the above description, the side surfaces form 90 ° with each other. Become. However, in the case of a rectangular parallelepiped, the opposing side surfaces are parallel to each other, and therefore, there are only two types of intersecting lines to be considered in preventing the occurrence of moire fringes.
However, in the case of a polygonal column other than a rectangular parallelepiped, for example, a triangular prism, there are three types of intersecting lines to be considered, and in the case of a pentagonal column, there are five types, both of which are more than in the case of a rectangular parallelepiped. Therefore, the conditions for generating moire fringes increase and the degree of freedom in design decreases. Of course, even in the case of a quadrangular prism, adjacent side surfaces are not perpendicular to each other, and in a free quadrangular column, there are four types of intersection lines to consider, and in this respect, the opposing side surfaces are parallel and the bottom surface is a parallelogram or Even with a quadrangular prism made of rhombus, the occurrence of moire fringes can be prevented in the same manner as a rectangular parallelepiped. However, from the viewpoint of ease of manufacture, a rectangular parallelepiped is superior to a quadrangular prism made of these parallelograms and rhombuses.
In addition, as a case where the intersecting line derived from the side surface does not form a straight line, there is an n-prism column in which n is infinite, that is, a cylinder, an elliptical column, etc. whose side surface is a curved surface. For example, if the original film for producing the microprojection group is scanned by a parallel scanning method such as a scanner, the projections are microscopic so that the contour of the circular shape that forms a side surface that is not parallel or perpendicular to the scanning line Can not be made, the smooth side of the original cylinder.
[0041]
In addition, as a method of arranging the minute protrusions at random, the X and Y coordinates for arranging the minute protrusions may be generated using random numbers in an XY plane having a predetermined area corresponding to the entire surface of the lens sheet. In FIG. 7A, reference numeral 22 denotes random coordinate points where the microprotrusions 11b thus obtained are to be formed.
Here, when the minute projections that are too adjacent to each other between the coordinate points 22 and have a finite size are arranged at the coordinates, the minute projections come into contact with each other as shown in FIG. It is possible that an overlapping portion 23 is formed. In FIG. 8A, a dotted line is a virtual line for clearly showing an overlapping portion. In such a case, if the overlapped shapes are used as they are, the minute protrusions become large and may be visible. For this reason, as one solution, as shown in FIG. 8B, it is preferable that the height H of the microprojections in the overlapping portion is zero. In this way, it is possible to prevent adjacent adjacent overlapping microprotrusions from fusing and widening the top of the microprotrusions. Thereby, even if the minute protrusions overlap each other, it is possible to prevent the minute protrusions from becoming large and becoming visible.
FIG. 7 (b) shows a state where the overlapping portion remains as it is, and FIG. 7 (c) shows a microprojection group in a state where the height H of the overlapping portion is set to zero by processing as described above.
[0042]
The moire fringes generated due to the relationship between each microprotrusion, the constituent surface, and the constituent surface of the unit lens are all arranged in the same direction when the microprotrusions are arranged. This is because all of the above are defined to define a recognizable intersection line, and a relationship between this intersection line and the intersection line derived from the surface formed by the unit lens occurs.
However, even if all the microprotrusions have the same shape, if each microprotrusion is arranged in a random direction, that is, in FIG. 6B, all the microprotrusions have the same orientation. However, if the Z-axis direction perpendicular to the XY plane is rotated at random as the rotation axis, the intersecting lines obtained from the surfaces formed by the side surfaces of the microprotrusions are dispersed arbitrarily. The crossing line defined at a specific angle is eliminated, and even in this case, the generation of moire fringes can be prevented. However, from the viewpoint of ease of manufacture of the lens sheet, it is better to use the same direction.
[0043]
In this respect, a cylinder, an elliptic cylinder, etc. are excellent. However, as described above, there is difficulty in manufacturing a side surface having a smooth curved surface. In addition, as described above as an example of countermeasures when adjacent minute protrusions overlap each other when randomly arranged, the above-described method in which the height H is zero can form an acute cross-sectional shape at the contact portion. It will be difficult above.
However, without taking the method of setting the height H to zero, if the X-coordinate value and the Y-coordinate value of the X- and Y-coordinates for arranging the microprotrusions obtained by random numbers are a cylinder, it will be larger than its diameter D. If random numbers are generated (value portions such as digits below the rounds are rounded), the obtained random coordinate points are always separated from the diameter D, so even if microprojections are arranged at these coordinate points, they overlap. There is nothing at all. Further, as an extension of this method, the minimum adjacent distance can be adjusted by intentionally increasing the size of the dent.
[0044]
In addition, the distribution density of the micro-projections is such that the lens sheet is bent and an equal thickness interference fringe cannot be formed, and even if the lens sheet has a certain degree of rigidity, the light guide plate or the lens sheet on the lower side A uniform interval can be secured between them, and the thickness is appropriately set to such an extent that an equal-thickness interference fringe cannot be formed due to a slight difference in the interval.
The distribution density when the cross-sectional area of the microprotrusions is assumed to be zero, that is, the number distribution density for arranging the microprotrusions, is particularly high when the two lens sheets are used in an overlapping manner. It is preferable that the average distance d between the adjacent protrusions of the minute protrusions is not more than twice the repetition period p of the unit lens on the lower lens sheet surface, that is, d <2p.
By designing in this way, the support contacts between the minute projections 11b on the back surface of the upper lens sheet and the unit lenses 13a on the surface of the lower lens sheet which are supported in contact with each other are bent, and the distance between the upper and lower lens sheets is non-uniform Thus, it is possible to prevent interference fringes of equal thickness and the distance between the upper and lower lens sheets to be less than the wavelength of the light source light. The average distance d is more preferably d <0.5p.
[0045]
On the other hand, when the cross-sectional area of the microprotrusions is evaluated as a finite one, the distribution density that can prevent the equal thickness interference fringes even when the lens sheet is bent is the total of the lens sheet 10 and the light guide plate 41 facing each other. The area ratio Sr (= Sp / St × 100) of the total sum Sp of the cross-sectional areas of the protrusions with respect to the area St is preferably about 0.01 to 60%.
As the spacer function, it is preferable to function at the minimum, but it is necessary to some extent from the viewpoint of the bending of the lens sheet, and when the surface light source is combined with a light guide plate to be described later, the luminance surface Some degree is also necessary for uniform distribution.
[0046]
In order to consider the factors related to the in-plane distribution of luminance, an explanation will be given using the area ratio R that is inversely related to the area ratio Sr described above.
The total area Sa of the gaps 9 where the minute protrusions 11b are not in close contact with the surface of the light guide plate 41 and have an interval equal to or greater than the wavelength corresponds to the total area St where the lens sheet 10 and the light guide plate 41 face each other. As a ratio, the area ratio R [%] is expressed by the following equation.
R = Sa / St × 100
Therefore, the area ratio R has a relationship of area ratio Sr and R + Sr = 100.
The area ratio R is determined by the required in-plane luminance uniformity, light energy utilization efficiency, light guide plate dimensions, and the like. Usually, the area ratio R is 80% or more, more preferably 90%. This is necessary.
[0047]
The reason for this is that when the surface of the smooth light guide plate whose surface roughness is equal to or less than the wavelength of light and the surface (back surface) of the lens sheet 10 are in close contact with each other, a large amount of input light is incident on the light guide plate from the light source. The portion is emitted without being totally reflected in the region extending from the side edge on the light source side to the distance y (even if it is incident on the surface of the light guide plate at a critical angle or more, it is not totally reflected at that portion but is reflected on the unit lens. Since the light enters, the brightness is suddenly lowered and darkened at a place farther than y.
And the percentage with respect to the full length Y of the light propagation direction of the light guide plate of the light emission part length y will be 10 to 20% when actually measured.
Therefore, in order to evenly distribute the amount of light energy incident on the light guide plate from the light source over the entire length Y, most of light, ie, about 100% of light is emitted in the region of the length y on the surface of the light guide plate. Therefore, it is necessary to transmit and emit 10 to 20% of the incident light coming to the region having the length y and totally reflect the remaining 90 to 80% of the light.
Here, roughly
(Total reflected light amount / Total reflected light amount) ≈Sa / St = R
Therefore, R needs to be in the range of 80 to 90% (Sr = 10 to 20%).
And since it can approximate similarly also in the place far from y, the point which R needs 80 to 90% is applicable over the full length. However, if R is too close to 100% (Sr is 0%), it is not preferable because the distance between the minute projection groups cannot be kept above the wavelength of light due to the bending of the lens sheet as described above. Therefore, the upper limit of R is preferably 99.99% or less (Sr ≧ 0.01%).
In addition to the above, in the present invention, the light incident on the back surface of the lens sheet, which is one of the most important design concepts, is lost due to diffuse reflection (or transmission) in the tangential direction of the light exit surface of the surface light source. It is necessary to prevent as much as possible. From this point, the smaller the Sr, the better. Therefore, it is preferable to design so that the in-plane distribution of the luminance described above is minimized or is minimized within a range that satisfies the condition of equal thickness interference prevention.
[0048]
By providing the specific microprojection group as described above on one side of the lens sheet, the light beam emitted outside the viewing angle is increased and the luminance is not decreased, and the equal thickness interference fringes and moire fringes are prevented. An excellent lens sheet capable of distributing output light with a uniform surface distribution over the entire surface of the light guide plate can be obtained.
[0049]
Next, conditions and reasons for suppressing the generation of equal thickness interference fringes by the minute protrusions 11b will be described in detail.
FIG. 9 is a schematic diagram for explaining the principle of minute protrusions of the lens sheet according to the second embodiment. Here, description will be given by taking an example of an equal-thickness interference fringe formed between the lens sheets 10 and 10 (the base sheet 11 and the lens arrangement layer 13). However, the lens sheet 10 (the base sheet 11) and the light guide plate 41 are not described. The same applies to the case.
Height Δz of minute protrusion 11b 3 Is the longest wavelength of the visible light spectrum of the light source for observing this lens sheet 10B. max When the angle radius of the light source when the observer views the light source through the reflecting surface on the lens sheet 10B surface is Δθ, the condition of Expression (1) is satisfied. In order to distinguish from the wavelength λ of the light source of the surface light source, a capital letter Λ is used.
Δz 3 ≧ Λ max / 2Δθ 2 ... (1)
In addition, the one-dimensional and two-dimensional arrangements of the minute protrusions 11b are aperiodic, and the width Δx of the minute protrusions 11b satisfies the condition of Expression (2).
Δx ≦ 500 μm (2)
[0050]
Further, the average distance d between the adjacent minute protrusions 11b satisfies the condition of the expression (3) with respect to the period P of the unit lens 13a.
d <2P (3)
[0051]
Here, an example in which two sheets having the same structure as the lens sheets 10B-1 and 10B-2 are stacked and used so that the ridge lines of the unit lenses 13a are orthogonal to each other will be described.
[0052]
Next, the height of the minute protrusions 11b formed on the back surface of the lens sheet 10B-1 and the condition for eliminating the equal thickness interference fringes on the laminated surface of the lens sheets 10B-1 and 10B-2 will be described.
As shown in FIG. 9, a minute protrusion 11b is provided on the back surface of the lens sheet 10B-1 on the front surface side, and a gap H between the lens sheet 10B-1 and the lens sheet 10B-2 is provided. (X) Thus increasing the interface S 1 Ray L reflected from 1 And interface S 2 Ray L reflected from 2 The generation of equal-thickness interference fringes (a superordinate concept of the Newton ring) due to the interference with the.
[0053]
At this time, as the equal thickness interference fringes, it is considered that the equal thickness interference fringes are obtained by overlapping the equal thickness interference fringes of the minute protrusions 11b and the equal thickness interference fringes other than the minute protrusions 11b (peripheral part). It is necessary to do.
Among these, it is about the equal-thickness interference fringes other than the minute projections 11b (peripheral part), but the thickness H of the air gap layer (air layer) in that case (X) Is the thickness h when the lens sheets 10B-1 and 4-2 are directly contact-laminated due to the presence of the minute protrusions 11b. (X) And the height Δh of the minute protrusion 11b. That is,
H (X) = H (X) + Δh (4)
Here, since Δh> 0, 0 ≦ h (X) Even (ie h (X) → Even if it becomes 0 and asymptotically approaches 0)
H (X) ≧ Δh> 0 (5)
And H (X) No longer approaches 0.
[0054]
The equal thickness interference fringes disappear as the thickness H of the gap increases. Therefore, the lower limit value of H at which the equal thickness fringes disappear due to the increase in H, and this is substituted into equation (5) is the disappearance condition of the equal thickness fringes at the periphery of the microprotrusion 11b.
[0055]
Hereinafter, this condition is calculated. According to “Wave Optics” (Hiroshi Kubota, published by Iwanami Shoten, 4th edition, published on August 30, 1975), pages 87-89, when the light source has a spatial extent, the reflection surface S is observed from the observer. 1 , S 2 When the angle radius of the external light source 7 is Δθ [radian], the wavelength of the light source light is Λ [μm], and the thickness of the gap is H [μm].
Δθ << (Λ / 2H) 1/2 (6)
Then, it is known that equal thickness interference fringes are recognized. Therefore, from Equation (6), the condition that the uniform thickness fringes are not visible (the condition that no interference fringes are generated) is H. (X) When asked about
H (X) ≧ Λ / 2Δθ 2 ... (7)
It becomes. When Expression (7) is substituted into Expression (5), the height Δh of the minute protrusion 11b is
Δh ≧ Λ / 2Δθ 2 [Μm] (8)
If so, it is derived.
[0056]
The above is the case of a monochromatic light source. However, for a light source having an emission spectrum distribution that is normally used, since the equation (8) is directly proportional to λ, the light source spectrum (Λ min ≦ Λ ≦ Λ max ), The upper limit of spectral distribution Λ max If Eq. (8) is satisfied, it can be said that all of the remaining Λ satisfy Eq. (8). Therefore,
Δh ≧ Λ max / 2Δθ 2 [Μm] (1)
Is a condition for the height of the minute protrusion 11b for a light source having a spectral distribution.
[0057]
Now, when the specific numerical value of the expression (1) is obtained, the surface of the lens sheet 10B is observed using white light of 0.38 μm ≦ Λ ≦ 0.78 μm as the external light source 7, and the external light source 7 When the angular radius is 10 ° ≦ Δθ ≦ 120 °, that is, 0.175 [rad] ≦ Δθ ≦ 2.094 [rad] by normal indoor lighting or natural light from a window, the equation (1) can be expressed by the equation (1). Δθ = 0.175 [rad], and Λ with the smallest right-hand side max As a value corresponding to 0.78 [μm],
Δh ≧ 12.5 [μm] (9)
Get.
Note that the upper limit of Δh is not originally limited from the viewpoint of preventing optical adhesion. However, if Δh is too large, the lens sheet is likely to be bent, and when assembled to a surface light source, the thickness is increased and the protrusions are easily visible. Therefore, usually, it is preferable to make it 200 micrometers or less.
[0058]
In addition, although Formula (8), Formula (1), and Formula (9) are the minimum necessary conditions, the following conditions are added.
That is, in the case where the lens sheet 10B is made of an object that can be regarded as a completely rigid body, it is sufficient that the lens sheet 10B is supported by three protrusions that are not at the same straight line (triangular apex).
However, when the lens sheet 10B is made of a thin and flexible object made of, for example, a synthetic resin, if the distance between the minute protrusions 11b is too large, the lens sheet 10B bends at the portion of the minute protrusions 11b, and h (X) Furthermore, H (X) Does not satisfy the conditions of Expression (8), Expression (1), Expression (9), and Expression (5).
[0059]
Therefore, in this case, even if bending occurs, the minute projections 11b on the back surface with sufficient density so that the conditions of the expressions (8), (1), (9), and (5) are always satisfied. Is provided. As a measure of the density of the minute projections 11b, generally, it is two-dimensionally with a period of twice or less, more preferably 1/2 or less of the period P of the unit lens 13a of the lower lens sheet 10B-2. Try to distribute.
That is, the average distance d between the adjacent minute protrusions 11b and 11b may satisfy the condition of the expression (3) with respect to the period P of the unit lens 13a.
d <P (3)
Here, the condition of Expression (3) will be further described with reference to FIG. For the sake of simplicity, when the nearest three points A, B, and C of the microprojections 11b form an equilateral triangle ΔABC, and the lens sheet 10B is only a linear (one-dimensional) array of unit lenses 13a. 10A and 10B, when the distance AB between the two minute protrusions AB = distance BC = distance CA = 2P, the minute protrusions A and B are unit lenses 13a-1, 13a- When it is in contact with 3, focusing only on the y-axis direction, it appears that the unit lens 13 a-2 that does not come into contact with the minute protrusions is present between the minute protrusions A and B. However, when viewed two-dimensionally, the unit lens 13a-2 is supported by minute protrusions C separated in the y-axis direction.
In this way, all the unit lenses 13a are all supported by the microprojections 13b by the three-point support assembly as shown in FIGS. 10C and 10D, and therefore the lens sheet 10B-1 And the contact due to the bending of 4-2 is minimized.
Also, experimentally, when d exceeds P with d = 2P as a boundary, even thickness Δh and Δy begin to be visually observed even if Δh and Δy satisfy the conditions of equations (1) and (2), respectively. It has been confirmed. Therefore, the condition of equation (3) described above is obtained.
In this way, almost all the unit lenses 13a are supported by one minute protrusion 11b for every two unit lenses 13a, and the influence of bending is eliminated. However, if the average distance d is too small and the minute protrusions 11b are too dense, the diffusion angle of the emitted light is too wide, so it is preferable to select an appropriate range.
[0060]
Next, the equal thickness interference fringes of the minute protrusions 11b will be described. In the vicinity of the minute protrusion 11b, H (X) → Equal thickness fringes are unavoidable in order to achieve 0 (convergence). As means for practically avoiding this, the distribution of the microprotrusions 11b is randomly arranged without having a period in one or two dimensions, and the width ΔX of the microprotrusions 11b cannot be visually observed. The size is to be formed.
By doing so, even if an equal-thickness interference fringe is generated, it is localized only in the region of the microprotrusion 11b, and thus cannot be visually observed.
[0061]
However, if the microprotrusions 11b are periodically arranged, the microprotrusions 11b and the unit lens 13a always come into contact with each other with a certain period. Therefore, when observed from a distance, the micro interference fringes of the microprotrusions 11b are integrated. And will be visually observed as interference fringes.
By making the arrangement of the microprotrusions 11b non-periodic, the interference fringes of the microscopic microprotrusions 11b are randomly accumulated when they are observed from a distance and become zero, and are not visually observed.
Therefore, if the width ΔX of the minute protrusion 11b is normally set to about 100 μm or less, the practical purpose can be achieved. That is, it is sufficient to satisfy Expression (2).
Δy ≦ 100 μm (2)
[0062]
The microprotrusions 11b are preferably colorless and transparent, and the manufacturing method thereof is mechanical processing such as embossing (embossing) or sandblasting on the back surface of the lens sheet 10B, casting of transparent resin ( Casting) method, transparent
[0063]
(Light guide plate)
The opposite surface of the light reflection layer of the light guide plate 41 is a flat surface, and the surface roughness (measured by the JIS-B-0601 ten-point average roughness Rz or the like) is finished below the wavelength of the light source light. Usually, the light source is visible light, and its wavelength is 0.4 to 0.8 μm, so the surface roughness is 0.4 μm or less. As a method of finishing to such a level of roughness, known methods such as hot pressing with a mirror plate, injection molding using a specular shape, casting (casting) molding, precision polishing performed with an optical lens, etc. Should be used.
[0064]
The material of the light guide plate 41 is selected from the same translucent materials as those of the lens sheet described above. Usually, a polycarbonate resin is used. The thickness of the light guide plate is usually about 1 to 10 mm.
[0065]
(Example of direct surface light source)
FIG. 11 is a sectional view showing a first embodiment (direct type) of a surface light source according to the present invention.
The surface light source 51 is obtained by arranging the lens sheet 10 of FIG. 1 on the opening side of a direct backlight 30 in which a linear light source 32 such as a fluorescent lamp is provided in a case 31. In order to effectively use the light energy of the light source 32, it is preferable that the inner surface of the case 31 is coated with white or the like to have a high reflectance surface.
[0066]
(Edge light type surface light source)
FIG. 12 is a perspective view showing a second embodiment (edge light type) of a surface light source according to the present invention.
In the surface light source 52, the lens sheet 10B of FIG. 4 is disposed on the upper surface of the light guide plate 41 of the edge light type backlight 40. In this backlight 40, a reflective layer 42 is formed on the lower surface of the light guide plate 41, and a light source 43, a reflective film 44, and an illumination cover 45 are provided on both sides of the side end surface of the light guide plate 41. The edge light type surface light source has an advantage that it is thin and the light emission surface hardly generates heat.
[0067]
The details of the surface light source are described in [0017] to [0025] of Japanese Patent Laid-Open No. 6-324205, and a detailed description thereof will be omitted.
[0068]
(Example of liquid crystal display device)
The surface light sources 51 and 52 shown in FIGS. 11 and 12 can be used as a liquid crystal display device by being arranged on the back surface of a known transmissive liquid crystal display element.
In addition to a transmissive liquid crystal display element, the present invention can be applied to an element that requires a back light source such as an electrochromic display element.
[0069]
【The invention's effect】
As described above, according to the present invention, the average roughness of the irregularities and the average interval between the irregularities, the light entering the lens sheet through the base material sheet having the average wavelength less than the maximum wavelength of the light source light spectrum is changed. In addition, since the average interval is input into the light transmission diffusion layer having a minute unevenness group having a wavelength greater than or equal to the maximum wavelength of the light source light spectrum and is uniformly transmitted and diffused, there is a loss due to light dissipation to the outside of the lens due to light transmission diffusion In addition, the distribution of the luminance within the diffusion angle and the light exit surface can be made uniform, and after the light is transmitted and diffused by the light transmission diffusion layer, the light is again transmitted at a predetermined angle by the lens arrangement layer. The light diffusion angle can be concentrated within an appropriate angle, and the light diffusion dot pattern on the back surface of the light guide plate can be reduced by reducing the haze and spatial coherence due to the light transmission diffusion layer. The emissions were invisible, even equal thickness fringe is generated, disrupting the interference fringes, it is possible loss, problems prior art has ▲ 1 ▼, ▲ 3 ▼, ▲ 4 ▼ can be solved.
[0070]
In addition, since the substrate sheet is provided with minute protrusions serving as spacers, it is possible to prevent the distribution of output light and uniform thickness fringes with a uniform surface distribution over the entire surface of the light guide plate due to total reflection of the surface of the light guide plate In addition, the problems (2) and (4) of the prior art can be solved.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a first embodiment of a lens sheet according to the present invention.
FIG. 2 is a schematic diagram illustrating a minute step on the back surface of the lens sheet according to the first example.
FIG. 3 is a perspective view showing an example of a lens arrangement layer of the lens sheet according to the first example.
FIG. 4 is a perspective view of a second embodiment of the lens sheet according to the present invention as viewed from the front side.
FIG. 5 is a perspective view of a second embodiment of the lens sheet according to the present invention as viewed from the back side.
FIG. 6 is a diagram illustrating prevention of occurrence of moire fringes.
FIG. 7 is a diagram illustrating minute protrusions of a lens sheet according to a second example.
FIG. 8 is a diagram illustrating minute protrusions of a lens sheet according to a second example.
FIG. 9 is a schematic diagram illustrating the principle of minute protrusions of a lens sheet according to a second example.
FIG. 10 is a schematic diagram illustrating the principle of minute protrusions of a lens sheet according to a second example.
FIG. 11 is a cross-sectional view showing a surface light source according to the first embodiment (direct type).
FIG. 12 is a perspective view showing a surface light source according to a second embodiment (edge light type).
FIG. 13 is a schematic diagram showing a conventional example of a surface light source.
[Explanation of symbols]
10 Lens sheet
11 Substrate sheet
12 Light transmission diffusion layer
13 Lens arrangement layer

Claims (5)

  1. A light-transmitting substrate sheet;
    A light transmission diffusion layer laminated on the surface of the base sheet;
    A lens sheet comprising a lens array layer laminated on the surface of the light transmission diffusion layer,
    The base sheet has a smooth back surface in which the average roughness of the unevenness and the average interval are less than the maximum wavelength of the light source light spectrum,
    The light transmission diffusion layer, the different lens array layer and the refractive index, average roughness and average interval of irregularities than the maximum wavelength of the source light spectrum, the following fine irregularities groups 200 [mu] m, the said light transmission diffusion layer lens At the interface of both layers with the alignment layer ,
    The lens sheet is characterized in that the lens array layer is made of a light transmissive material and has a concave or convex lens shape arranged on the surface in a large number in one or two dimensions.
  2. The lens sheet according to claim 1,
    The lens sheet according to claim 1, wherein the substrate sheet has a height that is not less than the wavelength of the light source light and fine protrusions of 200 μm or less scattered on the back surface.
  3. A light guide composed of a light-transmitting flat plate or a rectangular parallelepiped cavity;
    A point-like or linear light source provided adjacent to at least one side surface of the side end surface of the light guide;
    A surface light source comprising the lens sheet according to claim 1 or 2 stacked on a surface of the light guide.
  4. One or more point or line light sources;
    A light source housing that surrounds the light source and has an opening on one side;
    A surface light source comprising the lens sheet according to claim 1 or 2 that covers the opening.
  5. A transmissive display element;
    A display device comprising the surface light source according to claim 3 or 4 provided on a back surface of the display element.
JP14042095A 1995-06-07 1995-06-07 Lens sheet, surface light source, and display device Expired - Lifetime JP3606636B2 (en)

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