JP3123006B2 - Surface light source and liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to relates to a liquid crystal display device using the surface light source and a surface light source using a triangular prismatic lenticular lens as a backlight.

[0002]

2. Related Background Art As a liquid crystal display device, a device using a direct-type or edge-light type diffusion surface light source is known (Japanese Patent Application Laid-Open No. 2-284102, Japanese Patent Application Laid-Open No. 63-318003).
No. JP-A-3-92601). In such a surface light source, a lenticular lens in which a large number of triangular prism type unit lens units are arranged in parallel in order to uniformly and isotropically diffuse emitted light within a desired angle range is used. The conventional lenticular lens has an apex angle α = 60 of the unit lens portion.
° and 90 ° were used. When this lenticular lens is used in combination with a matte transparent diffuser (matte transparent sheet), the light energy of the light source can be simply adjusted to a desired limited angle as compared with that using the matte transparent diffuser. It was possible to obtain a diffuse light having high uniformity and isotropic distribution within the angle range and distributed within the angle range.

[0003]

However, in the above-mentioned prior art, a phenomenon in which a part of light deviates from the above-mentioned angle range (the occurrence of side lobes in the angle distribution of transmitted light intensity).
Was inevitable. Since such a loss of light is not used in a liquid crystal display, a liquid crystal display element, in particular, in the case of a color system, has a drawback of realizing a clear screen while taking advantage of the liquid crystal display with low power consumption. Become. If 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 is not preferable for a third party as noise (stray light).

An object of the present invention is to solve the problems described above, the liquid crystal display, power consumption and calorific value without increasing the provide can be Ru surface light source and liquid crystal display device to obtain a bright surface emitting It is.

[0005]

According to a first aspect of the present invention, there is provided a light source, wherein the light source is disposed on at least one side end surface, a reflecting layer is formed on a lower surface, and a light emitting surface is formed on the light emitting surface. A light guide that emits symmetrical light, a lenticular lens disposed on the emission surface of the light guide, and a lenticular lens that refracts light rays from the light guide in a normal direction; and a front surface of the lenticular lens. A light isotropically diffusing layer that isotropically diffuses light rays from the light guide, wherein the apex angle of the unit lens portion of the lenticular lens is set to 95 degrees or more and 110 degrees or less. A side lobe to main lobe ratio of 20% or less.

[0006]

[0007]

[0008]

According to a second aspect of the present invention, there is provided the transmission type liquid crystal display element and the first aspect provided on a back surface of the liquid crystal display element.
A liquid crystal display device characterized by including a surface light source described in (1).

[0010]

According to the present invention , the angle distribution of the intensity of diffused light emitted from the diffused light emission surface falls within a desired angle range by setting the apex angle of the unit lens portion to 95 to 110 °. Only in this case, the distribution becomes substantially uniform and isotropic, and side lobes are not generated. Therefore, it can be suitably used for an edge light type surface light source or the like.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings and the like. Figure 1 (lenticular lens integrated) is a perspective view showing a first example of a lenticular <br/> Renzu used in the surface light source of the embodiment of the present invention. In the lenticular lens 10 of the first example , a large number of prism-shaped unit lens portions 12 each formed of a triangular prism are formed on one surface of a light-transmitting substrate 11 so that long axes (ridges) are parallel to each other. The other surface of the conductive substrate 11 is a flat surface 13. The unit lens portion 12 has an apex angle of the main cut surface of α.
Then, it is set so that 95 ° ≦ α ≦ 110 °.

The translucent substrate 11 is made of a homo- or copolymer of acrylate or methacrylate such as polymethyl methacrylate or polymethyl acrylate, polyester such as polyethylene terephthalate or polybutylene terephthalate, polycarbonate, It is a sheet-shaped or plate-shaped member made of a transparent material such as a transparent resin such as polystyrene, a transparent glass, or a transparent ceramic such as a transparent ceramic. This translucent substrate 11
Has a thickness of 20 to 1 when used for a back light source.
It is preferable to use one having a planar shape of about 000 μm. The pitch of the unit lens portion 12 is preferably approximately 10 to 500 μm, though it depends on the application. As a method of forming the prism shape, for example, a known hot pressing method (described in JP-A-56-157310), an ultraviolet curable thermoplastic resin film is embossed with a roll embossing plate, and then irradiated with ultraviolet rays. And a method of curing the film (described in JP-A-61-156273).

The translucency required for the translucent substrate 11 must be selected so as to transmit diffused light at a minimum so as not to hinder the use of each application. It may be colored transparent or matte transparent. Here, the term “matte transparency” refers to the property of transmitting transmitted light almost uniformly and isotropically in all directions within a semi-solid angle, and is used synonymously with light isotropic diffusion. That is, matte transparency means that the transparent substrate 11
The angle distribution I ⁰ (θ) of the transmitted light intensity when a parallel light beam is incident from the back surface (incident angle i = 0) is represented by cos distribution [I ⁰ (θ) =
I ⁰ _mp cos θ, −90 ° ≦ θ ≦ 90 °, θ indicates an angle formed with the normal line N, and I ⁰ _mp indicates transmitted light intensity in the normal direction) or a distribution similar thereto. The definition of I ⁱ (θ) will be described later.

[0014] (stacked lenticular lens) Figure 2 is a perspective view showing a second example of a lenticular <br/> Renzu used in the surface light source of the embodiment of the present invention. The lenticular lens 10 of the first example is formed as a single body of the light-transmitting base material 11, whereas the lenticular lens 10 ′ of the second example is formed on a flat light-transmitting substrate 14 from a triangular prism. This is a structure in which a lens layer 15 made of a light-transmitting material having a prism-shaped unit lens portion 12 is laminated. <br/> example of this also, the unit lens section 12, when the vertical angle and alpha, 95
The angle is set so as to satisfy the following condition.

(Transmission Measurement) The inventors of the present invention have made a
Various transmission measurements were made and the results are shown in FIGS. Here, the measurement conditions are shown and will be cited in the following discussion. Transmission measurement: FIG. 11 Lenticular lens with apex angle α = 90 ° (the lens portion is on 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 ° + matte transparent sheet Incident angle i = 0 ° Transmission measurement: FIG. 16 Layer structure of claim 1 and apex angle α = 90 ° (isosceles triangle) 3. A lenticular lens having a prism period of 100 μm + a matte transparent sheet (solid line). (Dashed line) Lenticular lens of α = 100 ° + matte transparent sheet (dotted line) Matte transparent sheet (dotted line) Incident angle i = 63 ° Transmission measurement: FIG. 17 Layer configuration of claim 1 and apex angle α = 3. A lenticular lens with 90 ° (isosceles triangle) and a prism period = 100 μm + a matte transparent sheet (solid line). Lens + matte transparent sheet (dashed line) Lenticular lens with apex angle α = 100 ° + matte transparent sheet (dashed line) matte transparent sheet (dotted line) Incident angle i = 30 °

(Explanation of apex angle α) The triangular prism type unit lens portion 12 has a transmitted light intensity I symmetrical with respect to the normal line N of the bottom surface or the base material surface.
In order to obtain (θ), when an isosceles triangle (symmetrical with respect to the normal line N) (see FIG. 3) or when the transmitted light distribution I (θ) is largely biased to either the left or right, It becomes a scalene triangle (see FIG. 4). However, the apex angle α is set to 95 ° ≦ α ≦ 110 ° in any case,
In particular, α is preferably around 100 °.

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 translucent substrate (or one in which the lenticular lens itself becomes a matte transparent substrate) Light intensity I
^This is because the distribution of ⁱ (θ) has negligible influence due to side lobes (side lobes) generated in the peripheral portion away from the main direction. Specifically, if the side lobe to main lobe ratio of the light intensity is R, it was found that R ≦ 15% (FIGS. 13 to 17). That is, in a case where a character image or the like is observed using a liquid crystal display element or the like, one of the optical characteristics required for the back light source is 30 to 100 ° left and right around the normal direction (particularly, 30 to 100 °).
It is necessary to ensure bright and uniform isotropic diffused light only within the angle range of 60 °). This is because television screens, clocks, lighting advertisements, various monitors, and the like are usually observed exclusively within the above angle range, and it is usually impossible to observe outside this angle range. .
However, within this angle range, the screen must be visible from any angle with the same illuminance and sharpness. This can be easily understood by assuming that the screen is observed in a state where a plurality of persons are arranged side by side in front of the television screen. Light traveling out of this angular range results in light loss and gives unwanted noise light in unrelated directions and should be suppressed rather. For this purpose, the distribution of the transmitted light intensity I ⁱ (θ) is 30 ° to 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, the transmitted light intensity I ⁱ (θ) is the peak direction of the main lobe (the direction in which the transmitted light intensity of the main lobe is the strongest, not necessarily the normal direction). However, the evaluation is preferably performed at an angle θ _10% within a range having an intensity of 10% or more of the transmitted light intensity _Imp of the transmitted light. Side rope to main lobe ratio Diffusion angle θ _10% is optimal range (30 ° ≦ θ _10% ≦ 100 °)
However, if the light intensity due to the side lobes is large, the above-described loss of light and leakage of noise light to a third party cannot be prevented. The side lobe to main lobe ratio R evaluates the influence of the side lobe, and is given by the following equation. R = (I _sp / I _mp ) × 100 [%] (1) where I _sp : peak direction intensity of side lobe I _mp : peak direction intensity of main lobe From the viewpoint of preventing the influence of optical noise on (the side direction of the liquid crystal display element), R ≦ 20
It has been found that these effects of side lobes are virtually negligible at%.

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

The reason why the upper limit of the apex angle α is 110 degrees is as follows. If α> 110 °, then the diffusion angle θ
_{Since 10%} deviates from the angle range, α ≦ 11
Must be 0 °. For example, when α = 90 °, θ _10% = 82 ° (see FIG. 13), when α = 100 °, θ _10% = 90 ° (see FIG. 14), and gradually increases.
When α = 110 °, θ _10% = 98 ° (see FIG. 15), and it can be seen that the required upper limit of the diffusion angle is reached. Further, when α = 180 ° as a limit where α is increased, that is, considering a perfect plane, when the matte transparent sheet 20 is a single body, there is no other choice but in that case, 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-diffusing and transmissive substance depends on the direction of transmitted light and the direction of incident light. The value for evaluating the angle dependence of the transmitted light intensity is I ⁱ (θ). That is, the transmitted light intensity I
ⁱ (θ) is, as shown in FIG. 6, the normal direction of the light emitting surface of the light that is diffused and transmitted in various directions and emitted when a light beam having an incident angle i is incident. Is defined as the light intensity traveling in the angle θ direction.

(Light Isotropic Diffusive Layer) The light isotropic diffusive layer 20 is formed by adding inorganic fine particles such as calcium carbonate, silica, alumina, barium carbonate and the like as a light diffusing agent (matting agent) to the translucent material. Alternatively, a dispersion of resin beads such as an acrylic resin is used, and the diameter of the particles is about 1 to 20 μm. As the light isotropically diffusing layer 20, a single layer formed by extruding or calendering a resin material obtained by kneading the light diffusing agent into the translucent material can be used. In addition, a two-layer structure is used in which a coating material in which the light-transmissive material is used as a binder (binder) and the light-diffusing agent is dispersed is formed on a sheet (or plate) of the light-transmissive material. It may be a constituent.
Further, the surface of the sheet (or plate) of the translucent material,
Fine irregularities (grain and the like) having a center line average roughness of 1 to 20 μm may be formed by sand blasting, embossing, or the like.

FIGS. 7 to 10 are diagrams showing the layer structure of the lenticular lens and the light isotropic diffusion layer. When the lenticular lens 10 and the light isotropically diffusing layer 20 are stacked and used, the lenticular lens 10 is on the observation side and the light isotropically diffusing layer 20 is on the light source side (FIGS. 7 and 9). There is a case on the opposite side (FIGS. 8 and 10). At this time, the unit lens unit 12 of the lenticular lens 10 may be on the observation side [FIGS. 7A to 10A], or the unit lens unit 12 may be on the light source side. 7 (B) to FIG. 10 (B)]. The light isotropically diffusing layer 20 may be a sheet (or a plate) (FIGS. 7 and 8) or may be directly applied to the lenticular lens 10 like the light isotropically diffusing layer 20 ′. It may be in the form of a film (FIGS. 9 and 10).

( Reference Example of Direct Type Surface Light Source) FIG. 18 is a sectional view showing a reference example (direct type) of a surface light source according to the present invention, and FIG. 19 illustrates the transmitted light intensity of the reference example of FIG. FIG. The direct-type surface light source 30 is the case 3
1, a linear light source 32 such as a fluorescent lamp is provided, and a lenticular lens 10 and an isotropic light diffusing layer 20 are provided on the opening side of a case 31. Light isotropic diffusion layer 2
The transmitted light intensity I ₁ ⁱ (θ) of 0 is a cos distribution,
The result is as shown in FIG. On the other hand, the lenticular lens 10 functions to refract light incident from the linear light source 32 and split the light into two directions, and the transmitted light intensity I ₂ ⁱ thereof.
(Θ) is as shown in FIG. Accordingly, the transmitted light intensity I ₃ ⁱ (θ) of the surface light source 30 is obtained by superposing the two, and I ₃ ⁱ (θ) = I ₁ ⁱ (θ) × I ₃
ⁱ (θ), which is a shape as shown in FIG.

FIG. 20 (edge light type surface light source Embodiment) is a sectional view showing an actual施例(edge light type) planar light source according to the present invention, FIG. 21, for explaining the characteristics of the light guide plate FIG. 22 is a diagram for explaining the transmitted light intensity of the embodiment of FIG. The edge light type surface light source 40 has a reflection layer 42 formed on the lower surface of a light guide plate 41, and the lenticular lens 10 and the light isotropic diffusion 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 inside 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, a part of the light beam is reflected (in the light guide plate 41) at the side interface of the emission surface 41 a of the light guide plate 41. And the rest is transmitted and emitted. In the actual light guide plate 41, FIG.
As shown in FIG. 1 (C), by placing a light source 43 'on the other end face or providing a light reflecting layer 42', a light beam propagates in the light guide plate 41 in both directions or a standing wave. As shown in FIG. 21 (D), from the emission surface 41a, ± θ symmetrical with respect to the normal
Light is emitted in the direction. This angle is θ = 60 ° and θ
= It is known to have a sharp peak in the direction of -60 °. Therefore, in order to deflect the light in the vicinity of the normal direction where the observer is present, the light beam is refracted by using the lenticular lens 10. Θ = 30 °, −30 °). Therefore, in the case of either the direct-type or the edge-light type surface light source, light emitted from the emission surface has an angular distribution having peaks in two directions symmetric with respect to the normal to the emission surface (FIG. 11). ). However, this still cannot be said to be a uniform surface light source, and the normal direction where the observer is present becomes dark. Therefore, by further combining the light isotropic diffusion 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 a range of 30 to 100 ° required for the observer.

The surface light source 40 is different from the direct surface light source 30 in that the light transmitted from the light guide plate 41 is not in the normal direction but in two directions symmetric with respect to the normal, for example, ± 63. °
For both the light isotropic diffusion layer 20 and the lenticular lens 10, the transmitted light intensity I ⁱ (θ) is such that the axis of symmetry is rotated by ± 63 ° in the normal direction with respect to the transmitted light in these two directions. [FIG. 22 (A), (B)], which are further combined (product of I ⁱ (θ)) to obtain the surface light source 4
The transmitted light intensity I ⁱ (θ) is 0 [FIG.
(B)]. FIGS. 16 and 17 show that θ = + 6
Only the transmitted light intensity I ⁱ (θ) in the directions of 3 ° and −30 ° is illustrated. At this time, peaks A and B in FIG. 22B cause side lobes A ′ and B ′. By setting the vertex angle α of the unit lens unit 12 to α ≧ 95 °,
The side lobes A 'and B' can be significantly attenuated.

(Light Reflecting Layer) FIG. 23 is a view showing an example of a light reflecting layer used in the edge light type surface light source according to this embodiment . Light reflection layer 42
Is a layer having the ability to diffuse and reflect light, and can be configured as follows. As shown in FIG. 23A, a white layer 42A in which a pigment having high concealment and 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. 23 (B), the matte fine irregularities 4 are formed on one side of the light guide plate 41 by sand brightening, embossing or the like.
1a, and a metal such as aluminum, chromium, silver or the like is plated or vapor-deposited to form a metal thin film layer 42B.
To form As shown in FIG.
The metal thin film layer 42B is formed on the same white layer 42A ′ (however, the concealing property may be low). FIG. 23 (D
As in 1) and (D2), it is possible to correct the attenuation of the light amount of the light source 43 by forming the halftone dot white layer 42A ″ and increasing the area ratio as the distance from the light source 43 increases.

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

[0030]

As described above in detail, according to the present invention, the intensity of the side lobe causing light loss and stray light (optical noise) can be greatly attenuated, and a limited angle can be obtained. Within the range (30 ° left and right around the normal direction)
(100 °). Therefore, when used as a surface light source, bright surface light emission can be obtained without increasing power consumption or heat generation. At this time, the light diffusion angle and the uniform isotropy of the light intensity within the diffusion angle can be maintained at substantially the same level as in the related art.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first example of a lenticular lens used for a surface light source according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a second example of the lenticular lens used for the surface light source according to the embodiment of the present invention.

FIG. 3 is a diagram for explaining a vertex angle of a unit lens portion of the lenticular lens of FIGS. 1 and 2 ;

FIG. 4 is a view for explaining a vertex angle of a unit lens portion of the lenticular lens of FIGS. 1 and 2 ;

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 diffusion layer.

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

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

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

FIG. 11 is a diagram showing a result of a transmission measurement (a lenticular lens having a vertex angle of 90 degrees).

FIG. 12 is a diagram showing the results of transmission measurement (light isotropic diffusion layer).

FIG. 13 is a diagram showing a result of transmission measurement (a combination of a lenticular lens having a vertex angle of 90 degrees and a light isotropic diffusion layer).

FIG. 14 is a diagram showing transmission measurement results (combination of a lenticular lens having a vertex angle of 100 degrees and a light isotropic diffusion layer).

FIG. 15 is a diagram showing the results of transmission measurement (combination of a lenticular lens having a vertex angle of 110 degrees and a light isotropic diffusion layer).

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

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

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

19 is a diagram illustrating transmitted light intensity of the reference example of FIG. 18;

20 is a sectional view showing an actual施例(edge light type) of the surface light source.

FIG. 21 is a diagram illustrating characteristics of a light guide plate.

FIG. 22 is a diagram illustrating transmitted light intensity in the embodiment of FIG. 20;

FIG. 23 is a diagram illustrating an example of a light reflection layer used in an edge light type surface light source according to the present embodiment .

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Lenticular lens 11 Translucent base material 12 Unit lens part 20 Light isotropic diffusion layer

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroyuki Amemiya 1-1-1, Ichigaya-Kaga-cho, Shinjuku-ku, Tokyo Inside Dai Nippon Printing Co., Ltd. (72) Inventor Noboru Masubuchi 1-chome, Ichigaya-cho, Shinjuku-ku, Tokyo No. 1 Inside Dai Nippon Printing Co., Ltd. (56) References JP-A-4-32888 (JP, A) JP-A-3-92601 (JP, U) US Patent 2,474,317 (US, A)

Claims (2)

(57) [Claims] 1. A light source, a light guide, wherein the light source is disposed on at least one side end surface, a reflective layer is formed on a lower surface, and light symmetrical with respect to an emission surface is emitted; A lenticular lens disposed on the emission surface of the light guide and refracting light rays from the light guide in a normal direction; and a light isotropic light disposed on the front surface of the lenticular lens and diffusing light from the light guide in a light isotropic manner. A diffusing layer, and the vertex angle of the unit lens portion of the lenticular lens is 9
A surface light source characterized in that the side lobe to main lobe ratio is set to be not less than 5 degrees and not more than 110 degrees so that the ratio of side lobe to main lobe is not more than 20%. 2. A liquid crystal display device comprising: a transmission type liquid crystal display element; and the surface light source according to claim 1 provided on a back surface of the liquid crystal display element.