JPH0618707A - Lenticular lens, surface light source and liquid crystal display device - Google Patents

Abstract

(57) [Summary] [Purpose] To obtain bright surface emission without increasing power consumption or heat generation. [Structure] A large number of prism-shaped unit lens portions 12 formed of triangular prisms are formed on one surface of a light-transmissive substrate 11 so that their major axis directions are parallel to each other, and a flat surface is formed on the other surface of the light-transmissive substrate 11. In the lenticular lens 10 in which 13 is formed, the apex angle α of the unit lens portion 12 is set to 95 degrees or more and 110 degrees or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a triangular prism type lenticular lens, a surface light source using the lenticular lens, and a liquid crystal display device using the surface light source as a backlight.

[0002]

2. Description of the Related Art A liquid crystal display device using a direct surface type or edge light type diffusion surface light source is known (JP-A-2-284102, JP-A-63-318003).
No. 3-92601). Such a surface light source uses a lenticular lens in which a large number of triangular prism type unit lens portions are arranged in parallel in order to diffuse the emitted light uniformly and isotropically within a desired angle range. In the conventional lenticular lens, the apex angle α of the unit lens part is 60.
Those of 90 ° and 90 ° were used. When this lenticular lens is used in combination with a matte transparent diffuser (matte transparent sheet), it is easier than the one using a matte transparent diffuser to set the light energy of the light source at a desired limited angle. It was possible to obtain a diffused light that was distributed mainly within the range and had high uniform isotropy within the angular range.

[0003]

However, in the above-described conventional technique, a phenomenon in which a part of light deviates from the above-mentioned angle range (occurrence of side lobes in the angular distribution of transmitted light intensity).
Was unavoidable. Since such light loss is not used for liquid crystal display, it is an obstacle to realizing a clear screen while taking advantage of the liquid crystal display element such as low power consumption in the case of a liquid crystal display element, especially in a color system. Become. When the output of the light source is increased to solve this problem, the temperature rises due to heat, which is not preferable for the liquid crystal. Further, the light leaking in the side direction becomes noise (stray light) for a third party, which is not preferable.

An object of the present invention is to solve the above-mentioned problems and provide a lenticular lens, a surface light source and a liquid crystal display device capable of obtaining a bright surface emission without increasing power consumption and heat generation amount in a liquid crystal display. It is to be.

[0005]

According to a first solution of the present invention, a large number of prism-shaped unit lens portions each having a triangular prism shape are formed on one surface of a light-transmissive substrate so that their major axis directions are parallel to each other. In the lenticular lens in which a flat surface is formed on the other surface of the translucent substrate, the apex angle of the unit lens portion is set to 95 degrees or more and 110 degrees or less.

A second solution is to provide a translucent base material having both flat surfaces and a prism-shaped unit lens portion formed of a triangular prism, which is laminated on one surface of the translucent base material. In the lenticular lens including a large number of lens layers made of a light-transmissive material so that the axial directions thereof are parallel to each other, the apex angle of the unit lens portion is set to 95 degrees or more and 110 degrees or less. Characterize.

A third solving means is the method according to the first or second solving means, wherein both or one of the light transmitting base material and the lens layer has a light isotropic diffusing property, or the light transmitting property. A light isotropic diffusing layer may be formed on one side of the substrate or the lens layer.

A fourth solving means is to stack a light guide plate made of a light-transmissive flat plate, a linear light source provided adjacent to both or one of side end faces of the light guide plate and a surface of the light guide plate. It is characterized in that it includes a light isotropic diffusing layer and the lenticular lens of the first or second solving means, and the surface serves as a diffused light emitting surface.

A fifth solving means is characterized by including a transmissive liquid crystal display element and the surface light source of the fourth solving means provided on the back surface of the liquid crystal display element.

[0010]

In the lenticular lens of the present invention, by setting the apex angle of the unit lens portion to 95 to 110 °, the angular distribution of the diffused light intensity emitted from the diffused light emitting surface is almost within the desired angle range. Has a uniform isotropic distribution, and
Since side lobes do not occur, it can be suitably used for an edge light type surface light source.

[0011]

The present invention will be described in detail below with reference to the drawings and the like. (Example of integrated lenticular lens) FIG. 1 is a perspective view showing a first example of a lenticular lens according to the present invention. Lenticular lens 1 of the first embodiment
In the case of 0, a large number of prism-shaped unit lens portions 12 formed of triangular prisms are formed on one surface of the translucent substrate 11 so that their major axes (ridges) are parallel to each other, and the other surface of the translucent substrate 11 is Is a flat surface 13. This unit lens part 1
2 is 95 ° ≦ α ≦, where α is the apex angle of the main cutting surface.
It is set to be 110 °.

The light-transmitting substrate 11 is a homopolymer or copolymer of acrylic acid ester or methacrylic acid ester such as polymethylmethacrylate, polymethylacrylate, polyester such as polyethylene terephthalate, polybutylene terephthalate, polycarbonate, It is a sheet-like or plate-like member having a flat or curved surface shape made of a transparent resin such as polystyrene or the like, transparent glass or the like, or a transparent material such as transparent ceramics or the like. This translucent base material 11
Has a thickness of 20 to 1 when used as a back light source.
It is preferable to use a planar shape having a thickness of about 000 μm. The pitch of the unit lens portions 12 is preferably about 10 to 500 μm, though it depends on the application. As a method for forming the prism shape, for example, a publicly known heat pressing method (described in JP-A-56-157310), an ultraviolet ray curable thermoplastic resin film is embossed with a roll embossing plate, and then irradiated with ultraviolet rays. Then, a method of curing the film (described in JP-A-61-156273) is used.

The translucency required for the translucent base material 11 must be selected so that diffused light can be transmitted at least to the extent that it does not hinder the use of each application. It may be colored transparent or matt transparent. Here, the matte transparent has a property of diffusing and transmitting the transmitted light almost uniformly and isotropically in all directions within a semi-solid angle, and is synonymous with light isotropic diffusivity. That is, the matte transparent means the transparent substrate 11
Where θ is the angle formed by the surface normal to the normal direction, the angular distribution I ⁰ (θ) of the transmitted light intensity when the parallel light flux is incident from the back surface (incident angle i = 0) is the cos distribution [I ⁰ (θ) =
I ⁰ _mp cos θ, −90 ° ≦ θ ≦ 90 °, θ is an angle formed by the normal line N, and I ⁰ _mp is a transmitted light intensity in the normal direction) or a distribution similar thereto. The definition of I ⁱ (θ) will be described later.

(Embodiment of Laminated Lenticular Lens) FIG. 2 shows a second lenticular lens according to the present invention.
It is a perspective view showing an example of. The lenticular lens 10 of the first embodiment is formed by the transparent base material 11 alone, but the lenticular lens 10 ′ of the second embodiment has a flat transparent substrate 14 on which This is a structure in which a lens layer 15 made of a translucent material having a prism-shaped unit lens portion 12 made of a triangular prism is laminated. Also in this embodiment, the unit lens portion 12 has a vertical angle of 9
It is set so that 5 ° ≦ α ≦ 110 °.

(Transmission Measurement) The inventors of the present invention conducted various transmission measurements on the lenticular lens 10 and show the results in FIGS. 11 to 17. Here, the measurement conditions are shown and quoted in the following consideration. Transmission measurement: FIG. 11 Lenticular lens with apex angle α = 90 ° (lens portion is the light source side) Incident angle i = 0 ° Transmission measurement: FIG. 12 Matte transparent sheet (light isotropic diffusion layer) Incident angle i = 0 ° Transmission measurement: FIG. 13 Lenticular lens with apex angle α = 90 ° + matte transparent sheet Incident angle i = 0 ° Transmission measurement: FIG. 14 Lenticular lens with apex angle α = 100 ° + matte transparent sheet Incident angle i = 0 ° Transmission measurement: FIG. 15 Lenticular lens with apex angle α = 110 ° + matt transparent sheet Incident angle i = 0 ° Transmission measurement: FIG. 16 Layer structure of claim 1 and apex angle α = 90 ° (isosceles triangle) , Lenticular lens with prism period = 100 μm + matte transparent sheet (solid line) The layer structure of claim 2, and apex angle α = 90 ° (isosceles triangle), Lenticular lens with prism period = 50 μm + matte transparent sheet ( Dashed line Lenticular lens with α = 100 ° + matte transparent sheet (one-dot chain line) Matte transparent sheet (two-dot chain line) Incident angle i = 63 ° Transmission measurement: FIG. 17 Layer configuration of claim 1 and apex angle α = Lenticular lens with 90 ° (isosceles triangle) and prism period = 100 μm + matt transparent sheet (solid line) The lenticular with the layer structure of claim 2 and apex angle α = 90 ° (isosceles triangle), prism period = 50 μm Lens + matte transparent sheet (dashed line) Lenticular lens with apex angle α = 100 ° + matte transparent sheet (dashed line) Matte transparent sheet (dashed line) Incident angle i = 30 °

(Explanation of apex angle α) In order to obtain the transmitted light intensity I (θ) of the triangular prism type unit lens portion 12 whose shape is bilaterally symmetrical with respect to the normal line N of the bottom surface or the substrate surface. Is
Isosceles triangle (symmetrical with respect to normal line N) (see FIG. 3) or transmitted light distribution I (θ) on either side
When is biased a lot, it becomes an isosceles triangle (see FIG. 4). However, in all cases, the apex angle α is 95 ° ≦ α
≦ 110 ° is set, and in particular, α = about 100 ° is preferable.

The reason why the lower limit of the apex angle α is 95 ° is as follows. If α ≧ 95 °, transmission of a laminate of a triangular prism type lenticular lens and a matte transparent transparent base material (or the lenticular lens itself becoming a matte transparent substrate). Light intensity I
^This is because the distribution of ⁱ (θ) can be neglected by the side lobes (Side robes) generated in the peripheral portion away from the main direction. Specifically, it is found that R ≦ 15% when the side lobe to main lobe ratio of light intensity is R (FIGS. 13 to 17). That is, in the case of observing a character image or the like using a liquid crystal display element or the like, one of the optical characteristics required for the back light source is 30 to 100 ° (in particular, 30 to 100 ° to the left and right around the normal direction).
It is necessary to ensure bright and uniform isotropic diffused light only within the angular range of 60 °. This is because television screens, clocks, lighting advertisements, various monitors, etc. are usually exclusively observed within the above-mentioned angle range, and it is usually impossible to observe them outside this angle range. .
However, within this angle range, the screen must be visible from any angle with equivalent illuminance and definition. This can be easily understood by assuming that a plurality of people are laid side by side in front of the television screen and observing the screen. Light traveling outside this angular range results in light loss and also gives unwanted noise light in unrelated directions and should therefore be suppressed. For that purpose, the distribution of the transmitted light intensity I ⁱ (θ) is 30 ° on the left and right including the normal direction.
It is necessary to include most of the transmitted light amount within 100 °.

To evaluate this, the following two parameters are effective. Diffusion angle The diffusion angle is, for example, as shown in FIG. 5, when the transmitted light intensity I ⁱ (θ) is in the peak direction of the main lobe (the direction in which the transmitted light intensity of the main lobe is strongest, not necessarily the normal direction). However, it is preferable to evaluate at an angle θ _10% within a range having an intensity of 10% or more of the transmitted light intensity ( _Imp ). Side rope to main lobe ratio Diffusion angle θ _10% is the optimum range (30 ° ≤ θ _10% ≤ 100 °)
However, if the light intensity due to the side lobes is high, it is impossible to prevent the above-described loss of light and leakage of noise light to a third party. The side lobe-to-main lobe ratio R evaluates the effect of this side lobe, and is given by the following equation. R = (I _sp / I _mp ) × 100 [%] (1) However, I _sp : side lobe peak direction intensity I _mp : main lobe peak direction intensity In this way, efficient use of light, a third party R ≦ 20 from the viewpoint of preventing the influence of optical noise on (the side direction of the liquid crystal display element).
%, It was found that these effects of side lobes can be neglected.

The results of experiments conducted by the inventors of the present application show that
The value of R is the apex angle α of the unit lens portion 12 of the triangular prism type.
It was found that, in the range of α <95 °, R> 20%, and that the value suddenly decreases around α = 95 °. For example, as shown in FIG. 7 (A), a triangular prism type lenticular lens 10 on which an optically isotropic diffusion layer (matte transparent sheet) 20 is laminated is vertically incident from the back surface (incident angle i = 0. When a light ray is incident at an angle of 90 °), as shown in FIG. 13, when the apex angle α of the unit lens portion 12 is 90 °, R = 26% (> 20%), whereas as shown in FIG. It can be seen that when α = 100 °, R = 13%. Further, as shown in FIG. 15, α =
At 110 °, R = 6%.

The reason why the upper limit of the apex angle α is 110 degrees is as follows. When α> 110 °, this time the diffusion angle θ
_{Since 10%} deviates from the above angle range, α ≦ 11
Must be 0 °. For example, when α = 90 °, θ _10% = 82 ° (see FIG. 13), and when α = 100 °, θ _10% = 90 ° (see FIG. 14).
It can be seen that when α = 110 °, θ _10% = 98 ° (see FIG. 15) and the required upper limit of the diffusion angle is reached. Furthermore, when α = 180 °, that is, when considering a perfect plane, as the limit of increased α, it is none other than when the matte transparent sheet 20 is a single body. At that time, as shown in FIG. It can be seen that the angle θ _10% reaches 140 °.

(Definition of Transmitted Light Intensity I ⁱ (θ)) The angle dependence of the intensity of light transmitted through a light diffusive and transmissive substance depends on the transmitted light ray direction and the incident light ray direction. The value for evaluating the angle dependence of the transmitted light intensity is I
ⁱ (θ). That is, as shown in FIG. 6, the transmitted light intensity I ⁱ (θ) is the light that is diffused and transmitted in various directions and emitted when a light beam having an incident angle i is incident. It is defined as the light intensity that advances in the angle θ direction with respect to the direction normal to the emission surface.

(Light Isotropic Diffusion Layer) Light Isotropic Diffusion Layer 20
Is used as a light diffusing agent (matting agent) in the translucent material, in which inorganic fine particles such as calcium carbonate, silica, alumina, barium carbonate, or resin bead particles such as acrylic resin are dispersed. The diameter of the particles is approximately 1 to 20.
Those of the order of μm are used. The light isotropic diffusing layer 20 may be formed as a single layer by extruding a resin material obtained by kneading the light diffusing agent into the translucent material into a sheet by calendering or the like. Further, the translucent material is bound on the sheet (or plate) of the translucent material with a binder.
Alternatively, a two-layer structure may be used in which a coating material in which the light diffusing agent is dispersed is applied and formed. Further, the surface of the sheet (or plate) of the translucent material is subjected to sandblasting, embossing, or the like so as to have a center line average roughness of 1 to 20 μm.
It is also possible to form minute irregularities (grains, etc.) of m.

FIGS. 7 to 10 are views showing the layer structure of the lenticular lens and the light isotropic diffusive layer. When the lenticular lens 10 and the light isotropic diffusing layer 20 are laminated and used, when the lenticular lens 10 is on the observing side and the light isotropic diffusing layer 20 is on the light source side (FIGS. 7 and 9), It may be on the opposite side (FIGS. 8 and 10). At this time, the unit lens portion 12 of the lenticular lens 10 may be on the observation side [FIG. 7 (A) to FIG. 10 (A)], or the unit lens portion 12 may be on the light source side [FIG. 7 (B) to FIG. 10 (B)]. The light isotropic diffusive layer 20 may be in the form of a sheet (or a plate) (FIGS. 7 and 8), or may be directly coated on the lenticular lens 10 like the light isotropic diffusive layer 20 ′. It may be in the form of a film (FIGS. 9 and 10).

(Embodiment of direct type surface light source) FIG. 18 is a sectional view showing a first embodiment (direct type) of the surface light source according to the present invention, and FIG. 19 is transmitted light of the embodiment of FIG. It is a diagram explaining strength. The direct type surface light source 30 includes a line light source 32 such as a fluorescent lamp provided in a case 31, and a lenticular lens 10 and a light isotropic diffusing layer 20 provided on the opening side of the case 31. . The transmitted light intensity I ₁ ⁱ (θ) of the light isotropic diffusive layer 20 has a cos distribution and is shown in FIG.
9 (A). On the other hand, the lenticular lens 10 refracts light incident from the linear light source 32 and
It acts to divide the light into two directions, and the transmitted light intensity I
₂ ⁱ (θ) is as shown in FIG. Therefore, the transmitted light intensity I ₃ ⁱ (θ) of the surface light source 30 is a superposition of the two, and I ₃ ⁱ (θ) = I ₁ ⁱ (θ) ×
I ₃ ⁱ (θ) is obtained, and the shape is as shown in FIG.

(Example of Edge Light Type Surface Light Source) FIG.
0 is a cross-sectional view showing a second embodiment (edge light type) of the surface light source according to the present invention, FIG. 21 is a diagram for explaining the characteristics of the light guide plate, FIG. 22 is the transmission of the embodiment of FIG. It is a diagram explaining light intensity. The edge light type surface light source 40 is
The reflection layer 42 is formed on the lower surface of the light guide plate 41, and the lenticular lens 10 and the light isotropic diffusive layer 20 are arranged on the upper surface of the light guide plate 41. A light source 43, a reflective film 44, and a lighting cover 45 are provided on both sides of the side end surface of the light guide plate 41, respectively.

When the incident angle i of the light guide plate 41 is larger than the critical angle ic, as shown in FIG.
Only propagates while totally reflecting in the light guide plate 41,
There is no transmitted light from the emission surface 41a. On the other hand, when the incident angle i is smaller than the critical angle ic, as shown in FIG. 21B, at the side interface of the emission surface 41a of the light guide plate 41, part of the light beam is reflected (in the light guide plate 41). And the rest is transmitted and emitted. Moreover, in the actual light guide plate 41, as shown in FIG.
As shown in FIG. 1 (C), a light source 43 ′ is placed on the other end surface or a light reflecting layer 42 ′ is provided, so that light rays propagate bidirectionally inside the light guide plate 41 or a standing wave. In order to form the structure, from the emission surface 41a, as shown in FIG.
Light is emitted in the direction. This angle is θ = 60 ° and θ
It is known to have a sharp peak in the -60 ° direction. Therefore, in order to deflect this near the normal direction where the observer is present, the light beam is refracted by using the lenticular lens 10, and the optimum normal direction (for example, when the right angle α = 90 °, as shown in FIG. 11). (Θ = 30 °, −30 °). Therefore, in the case of either the direct type or the edge light type surface light source, the light emitted from the emitting surface has an angular distribution having peaks in two directions symmetrical to the normal of the emitting surface (FIG. 11). ). However, this is still not a uniform surface light source, and since the direction of the normal line where the observer is darkened, by further combining the light isotropic diffusing layer (matte transparent layer) 20, It has a gentle peak in the normal direction, and usually
It is possible to obtain a surface light source that emits diffused light only within the range of 30 to 100 ° on the left and right that is required by the observer.

In the surface light source 40, compared with the direct type surface light source 30, the light transmitted from the light guide plate 41 is not in the normal direction but in two symmetrical directions with respect to the normal line, for example, ± 63. °
Therefore, in both the light isotropic diffusive layer 20 and the lenticular lens 10, the transmitted light intensity I ⁱ (θ) is rotated by ± 63 ° in the normal direction with respect to the transmitted light in these two directions. 22 (A) and (B) !, which are further combined (the product of I ⁱ (θ)) to form the surface light source 4.
The transmitted light intensity I ⁱ (θ) becomes 0 [FIG. 22 (C),
(B)]. 16 and 17, of these, θ = + 6
Only the transmitted light intensity I ⁱ (θ) in the 3 ° and −30 ° directions is shown. At this time, peaks A and B in FIG. 22B cause side lobes A ′ and B ′. By setting the apex angle α of the unit lens portion 12 to α ≧ 95 °,
The side lobes A'and B'can be significantly attenuated.

(Example of Light Reflecting Layer) FIG. 23 is a view showing an example of a light reflecting layer used in an edge light type surface light source. The light reflection layer 42 is a layer having a property of diffusing and reflecting light, and can be configured as follows. As shown in FIG. 23A, a white layer 42A in which a pigment having a high hiding property and a high whiteness, for example, a powder of titanium dioxide, aluminum or the like is dispersed is formed on one surface of the light guide plate 41 by painting or the like. As shown in FIG. 23B, a matte fine unevenness 41a is formed on one surface of the light guide plate 41 by sandbright processing, embossing, or the like, and a metal such as aluminum, chromium, or silver is plated or evaporated. Then, the metal thin film layer 42
Form B. As shown in FIG. 23C, the metal thin film layer 42B is formed on the white layer 42A ′ (however, the hiding property may be low) similar to that of FIG. 22A. As shown in FIGS. 23D1 and 23D2, the halftone dot-shaped white layer 42A ″ is formed, and the area ratio is increased as the distance from the light source 43 increases, so that the attenuation of the light amount of the light source 43 is corrected. Good.

The surface light sources 30, 40 shown in FIGS. 18 and 20.
Can be used as a liquid crystal display device by disposing it on the back surface of a known transmissive liquid crystal display element.

[0030]

As described in detail above, according to the present invention, the intensity of the side lobe that causes the loss of light and stray light (optical noise) can be greatly attenuated, and the angle of a limited angle can be reduced. Within the range (30 ° to the left and right around the normal direction)
It has become possible to concentrate light with high uniformity and isotropy at 100 °. Therefore, when it is used as a surface light source, bright surface emission can be obtained without increasing power consumption or heat generation amount. At this time, the diffusion angle of light and the uniform isotropy of the light intensity within the diffusion angle can be maintained at substantially the same level as in the conventional case.

[Brief description of drawings]

FIG. 1 is a perspective view showing a first embodiment of a lenticular lens according to the present invention.

FIG. 2 is a perspective view showing a second embodiment of the lenticular lens according to the present invention.

FIG. 3 is a diagram for explaining an apex angle of a unit lens portion of a lenticular lens according to an example.

FIG. 4 is a diagram for explaining an apex angle of a unit lens portion of a lenticular lens according to an example.

FIG. 5 is a diagram for explaining a diffusion angle.

FIG. 6 is a diagram for explaining transmitted light intensity I ⁱ (θ).

FIG. 7 is a diagram showing a combination of a lenticular lens and a light isotropic diffusing layer.

FIG. 8 is a diagram showing a combination of a lenticular lens and a light isotropic diffusing layer.

FIG. 9 is a diagram showing a combination of a lenticular lens and a light isotropic diffusing layer.

FIG. 10 is a diagram showing a combination of a lenticular lens and a light isotropic diffusing layer.

FIG. 11 is a diagram showing a result of transmission measurement (a lenticular lens having an apex angle of 90 °).

FIG. 12 is a diagram showing a result of transmission measurement (light isotropic diffusive layer).

FIG. 13 is a diagram showing a result of transmission measurement (combination of a lenticular lens having an apex angle of 90 ° and a light isotropic diffusing layer).

FIG. 14 is a diagram showing a result of transmission measurement (combination of a lenticular lens having an apex angle of 100 degrees and a light isotropic diffusing layer).

FIG. 15 is a diagram showing a result of transmission measurement (combination of a lenticular lens having an apex angle of 110 ° and a light isotropic diffusing layer).

FIG. 16 is a diagram showing a result of transmission measurement (incident angle: 63 °).

FIG. 17 is a diagram showing the results of transmission measurement (incident angle 30 °).

FIG. 18 is a sectional view showing a first embodiment (direct type) of a surface light source according to the present invention.

FIG. 19 is a diagram illustrating the transmitted light intensity of the example of FIG.

FIG. 20 is a cross-sectional view showing a second embodiment (edge light type) of the surface light source.

FIG. 21 is a diagram for explaining the characteristics of the light guide plate.

22 is a diagram illustrating the intensity of transmitted light in the example of FIG.

FIG. 23 is a diagram showing an example of a light reflecting layer used in an edge light type surface light source.

[Explanation of symbols]

 10 Lenticular lens 11 Light transmissive base material 12 Unit lens part 20 Light isotropic diffusive layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuo Masubuchi 1-1-1 Ichigayakamachi, Shinjuku-ku, Tokyo Dai Nippon Printing Co., Ltd.

Claims (5)

[Claims] 1. A plurality of prism-shaped unit lens portions each formed of a triangular prism are formed on one surface of a light-transmissive substrate so that their major axis directions are parallel to each other, and a flat surface is formed on the other surface of the light-transmissive substrate. In the lenticular lens in which the apex angle of the unit lens portion is 95 degrees or more,
A lenticular lens characterized by being set to less than or equal to a degree. 2. A translucent base material having flat surfaces on both sides, and prism-shaped unit lens portions formed of triangular prisms, which are laminated on one surface of the translucent base material, are parallel to each other in a long axis direction. In the lenticular lens including a plurality of lens layers made of a translucent material, the apex angle of the unit lens portion is 95 degrees or more and 110
A lenticular lens characterized by being set to less than or equal to a degree. 3. Either or both of the light-transmissive base material and the lens layer have a light isotropic diffusivity, or one side of the light-transmissive base material or the lens layer has a light isotropic diffusivity. The lenticular lens according to claim 1 or 2, wherein a layer is formed. 4. A light guide plate made of a light-transmissive flat plate, a linear light source provided adjacent to both or one of the side end faces of the light guide plate, and a light isotropic diffusivity laminated on the surface of the light guide plate. A surface light source comprising a layer and the lenticular lens according to claim 1 or 2, wherein the surface serves as a diffused light emitting surface. 5. A liquid crystal display device comprising a transmissive liquid crystal display element and the surface light source according to claim 4 provided on the back surface of the liquid crystal display element.