JP3424136B2 - Film lens for surface light source and surface light source using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film lens for a surface light source device used for displays such as liquid crystal televisions and personal computers, lighting equipment, and the like. The present invention relates to a triangular prism type lenticular lens for light control.

[0002]

2. Description of the Related Art As a conventional surface light source (for example, a backlight of a liquid crystal display device), light from a light source is transmitted through a light guide plate as shown in FIG. Let it enter the triangular prism type lenticular lens side,
An edge light type surface light source of a type in which light is emitted from a lens to an observer side is known from Japanese Utility Model Laid-Open No. 4-107201. Separately, there is also a direct type surface light source of a type in which light from a light source as shown in FIG. 7B is directly incident on a triangular prism type lenticular lens side through a diffusion plate and emitted from the lens to an observer side. No. 257188 and the like. These surface light sources (backlights, etc.) are controlled by using a lens array in which a large number of isosceles triangular prism type unit lenses are arranged in parallel in order to collect emitted light within a desired angle range. However, by arranging the diffusion plate,
Further, the light intensity (luminance) distribution is dispersed so as to be uniform and isotropic within a predetermined angle. In particular, in the case of an edge light type surface light source, the reason for adopting the above configuration is that most of the light from the light guide plate is emitted in a direction of about 63 degrees to the left and right from the normal direction, as shown in FIG. This is because, from the front of the backlight, only about 10 to 20% of the light intensity emitted in the direction of about 63 degrees to the left and right from the normal direction can be obtained. Even when the light is incident on the lens from the light guide plate via the diffusion plate, most of the light passing through the diffusion plate similarly exits in a direction of about 63 degrees to the left and right from the normal direction. This is because even in the case of the direct type, the angle of the light incident on the prism lens from the diffusion plate is wide, and the angle is controlled within the angle range necessary for the observer. As described above, by providing the isosceles triangular prism type lenticular lens on the light emitting surface side of the surface light source, it has been widely performed that the light has directivity and the angle is controlled.

In the edge light type surface light source, a lens having an array of a large number of unit triangular prisms each having an isosceles triangle whose main cut surface has a vertical angle of 90 ° is often used. In the case of using, the light entering the lens from the light guide plate or the diffuser plate in the direction of about 63 degrees to the left and right is emitted from the lens in the direction of about 30 degrees with respect to the normal direction, as shown in FIG. To be done. Therefore,
Most of the light incident on the lens is emitted in a narrow range of about 30 degrees to the left and right with respect to the normal direction. In this way, the light incident at a wide angle (angle of about 63 ° to the left and right with respect to the normal direction) is controlled so as to be focused around the normal direction of the light exit surface. However, when an isosceles triangular prism with an apex angle of 90 ° is used, the light rays incident from the vicinity of the normal direction of the light exit surface are returned in the direction in which they came by total reflection as shown in FIG. 9B. However, there was a limit to the improvement of brightness in the normal direction, which was a problem. When an isosceles triangular prism with an apex angle of 90 ° is used, most of the light is emitted within a narrow angle range of about 30 ° to the left and right from the normal direction, so that the brightness is not uniform as a whole. Was enough.
Also, including the normal direction required by the observer, 30
Phenomenon in which some light deviates from the angle range of ° to 100 ° (side lobes in the angular distribution of transmitted light intensity)
This is inevitable, and when observing the surface light source from the front, a large light loss occurs. That is, in the edge light type surface light source, in addition to such a loss of light, there is a limit to the improvement of the brightness in the normal direction, and the uniformity of the brightness is insufficient as a whole. It was a problem when realization of a clear screen with low power consumption was a problem. When the light output is increased in order to improve the brightness in the normal direction, the temperature rises due to heat, which is not preferable for a liquid crystal device or the like, which is a problem.

Also in the case of the direct type, the angle of light incident on the prism lens from the diffusion plate is distributed over a wide range, but basically the same problem is involved.

[0005]

Under the above circumstances, the present invention can improve the brightness in the normal direction by devising the shape of the film lens on the light exit side of a surface light source (backlight etc.). It is an object of the present invention to provide a surface light source (backlight) having a uniform luminance distribution in the desired angular range required by an observer as much as possible.

[0006]

A film lens for a surface light source of the present invention is an output control lens used on the light output side of a surface light source used for a display or the like, and is mainly formed on one surface of a transparent substrate. The cut surface shapes are the same in apex angle, and two kinds of non-isosceles triangle-shaped unit lenses, which are line-symmetrical and mirror-image-related, are alternately arranged adjacent to each other so that their ridge lines are parallel to each other. The other surface is a flat surface. Then, fine irregularities having a height of not less than the maximum wavelength of the light source and not more than 100 μm are formed on the flat surface of the film lens. Further, the height Δh on the flat surface of the film lens is Δh with respect to the maximum wavelength λ max of the light source light for observing this lens, and the angular radius Δθ of the light source observed through the reflecting surface on the film lens.
It is provided with fine irregularities satisfying ≧ λmax / 2Δθ ² .
Here, “parallel” means that the ridgeline of the apex angle portion and the ridgeline of the bottom portion of each unit lens are parallel to each other.

In the film lens of the present invention, as shown in a perspective view of FIG. 1 (a), a transparent lens portion 3 made of an ionizing radiation curable resin or the like is formed on the transparent base film 2, or Alternatively, the lens portion is directly formed on the transparent material film. The lens section 3 is shown in FIG.
As shown in (b), two different types of triangular prisms 3 having main cut surface shapes that are line-symmetrical and mirror-image to each other.
A and 3B are alternately arranged. The reason for such an arrangement is that optical symmetry can be maintained. The apex angle α is in the range of 60 ° to 120 °, the base angles β and γ are not equal, the lengths L1 and L2 of the sides sandwiching the apex angle are different, and the lengths of the sides sandwiching the apex angle are different. That is, the unit lenses are arranged so that the ridge lines are parallel to each other so that the unit lenses have the same length as the continuous sides of the sides of the adjacent triangular prisms.

The film lens of the present invention is shown in FIG.
As shown in (c), fine irregularities may be provided on the flat surface of the film lens. When the height of the fine irregularities is equal to or greater than the maximum wavelength of the light source light and equal to or less than 100 μm, when the edge light type surface light source is mounted on the surface of the light guide plate, the optical surface between the flat surface of the film lens and the light guide plate surface is The amount of totally reflected light and the amount of transmitted output light are appropriately distributed at the interface between the light guide plate and the film lens, thereby making the distribution of the brightness of the entire surface of the light guide plate uniform depending on the in-plane location. Also, the height Δh of the fine unevenness is the maximum wavelength λma of the light source light for observing this lens.
x, where Δh ≧ λmax / 2Δθ ² where Δθ is the angular radius of the light source observed through the reflecting surface on the film lens
It is preferable that the flat surface of the film lens is placed on the light guide plate, or interference fringes such as Newton's rings generated on the superposed surfaces when two kinds of film lenses are used are prevented.

The base film used in the film lens of the present invention is a transparent film used in a backlight mechanism of a normal optical display or liquid crystal display, and at least in the case of using a device as shown in FIG. Ionizing radiation permeable ones, when pressing only the film surface by a hot pressing method, a thermoplastic resin can be appropriately used, but polyester, nylon, acrylic resin, polycarbonate, polyarylate, fluorine resin, A film made of a synthetic resin such as polypropylene is preferable.

The optical path when light is incident on the film lens of the present invention will be briefly described below with reference to FIGS. In the case of FIG. 3, the light incident on the lens from the vicinity of the normal direction of the flat surface is not totally reflected, but most of the light is refracted by the long side of the main cut surface shape and emitted to the vicinity of the normal direction of the light exit surface. It This is because it is difficult for the conventional lens in which triangular prisms with an apex angle of 90 ° are arrayed to cause total retroreflection, and it is difficult to increase the brightness in the normal direction, but in the lens of the present invention, the back surface of the film lens is flat. Light rays incident from the normal direction of the surface can also be used as output light,
This means that the luminance in the normal direction can be increased relatively easily and efficiently. Further, when the light enters the lens at a wide angle in the case of FIGS. 4 and 5, it can be seen that most of the light is refracted in the normal direction from the long side sandwiching the apex angle. However, a part of the light is also refracted in the normal direction from the short side and is emitted. Consequently, a wide range of incident light can be used as output light in the vicinity of the normal direction of the light emitting surface, and the light distribution on the light emitting side can be reduced. That is, it is uniform over a wide range within a predetermined diffusion angle. Therefore, in the case of edge light type surface light source,
That is, when most of the light is incident at a wide angle from a specific angle (about 63 degrees to the left and right), when the light is focused in the normal direction by the lens, uniformity is provided in a wide range instead of a narrow range. This is also advantageous in this respect as compared with the conventional lens in which isosceles triangular prisms having an apex angle of 90 ° are arranged. Further, the apex angle α of the fill lens of the present invention is 80 ° to 100 ° in order to effectively emit the light incident on the lens at an angle close to the normal direction and improve the brightness in the normal direction. Particularly effective in the range.

Further, the surface light source of the present invention is a surface light source used for displays and the like, and uses the above-mentioned film lens of the present invention as a light control lens on the light output side. As described above, the surface light source can be applied not only to the edge light type surface light source as shown in FIG. 7A but also to the direct type surface light source as shown in FIG. 7B.

[0012]

The film lens of the present invention having such a structure has a method of forming a flat surface on the back surface of the film lens as compared with a case where an isosceles triangular prism having an apex angle of 90 ° is used for a back light surface light source. Light incident from the line direction can also be used as output light, increasing the brightness in the normal direction on the light output side, and improving the brightness uniformity overall in the desired angle range necessary for the observer. ing. or,
In the film lens of the present invention, the main cut surfaces have the same apex angle, and two kinds of non-isosceles triangle-shaped unit lenses that are line-symmetrical and mirror-image-shaped are alternately arranged so that their ridge lines alternate with each other. By arranging them so as to be parallel to each other, it is possible to ensure optical symmetry as the entire fill lens.

[0013]

EXAMPLES Example 1 of the fill lens of the present invention will be described in detail below with reference to the drawings. The fill lens 1 of Example 1 illustrated in FIG. 1A is a biaxially stretched PET (A4
The main part of the lens part 3 is a base film 2 made of 100 to Tobo Co., Ltd.) and a lens part 3 made of urethane acrylate ionizing radiation resin (manufactured by Dainichiseika Co., Ltd.) provided on the base film 2. The triangular prisms 3A and 3B, which are unit lenses of two types of non-isosceles triangular shapes that are line-symmetrical and mirror images of each other and have the same apex angle as the surface shape, have their ridge lines alternate with each other. Adjacent to be parallel. The main cut surface shape of the lens part 3 is shown in FIG.
In (b), the apex angle α is 90 °, β is 30 °, and γ is 6
It is 0 °.

With respect to the film lens 1 of Example 1, the optical path when directional light was irradiated to the flat surface side was examined. As for the light that has entered the film lens in the vertical direction, as shown in FIG. 3, almost all of the light is emitted to the light output side, but most of the light is output in the direction of 17 ° to the left and right with respect to the normal direction. To be done. As shown in FIG. 9B of the conventional isosceles triangular prism having an apex angle of 90 °, retro-total reflection does not occur. This means that when the film lens 1 of Example 1 is used as a surface light source, the luminance in the normal direction can be improved as compared with the conventional case where an apex angle of 90 ° isosceles triangle rhythm is used. In addition, as shown in FIGS. 4 and 5, most of the light incident on the lens from the direction of about 63 ° to the left and right is refracted toward the normal direction on the long sides sandwiching the apex angle. Then, the light is partially refracted in the normal direction on the short side and then emitted. In this case, the light emitted from the long side is emitted in the left and right directions of 48 ° with respect to the normal direction,
Light emitted from the short side is 2 on the left and right with respect to the normal direction.
It is emitted in the direction of 1 °. Therefore, most of the light
When it is used for an edge type surface light source that is incident on the lens from a direction of about 63 ° to the left and right, it is left and right with respect to the normal direction as in the case of using a conventional 90 ° apex angle isosceles triangular prism. Unlike most of the light is emitted only in the vicinity of the direction of about 30 °, it will be dispersed in the directions of 48 ° on the left and right and two directions of 21 ° (a total of 4 directions on the left and right). As compared with the 90 ° isosceles triangular prism, the uniformity of the luminance distribution on the light emitting surface side is improved as a whole. Further, the diffusion angle is 96 ° (48 ° left and right), which is a sufficiently practical value. After all, when the lens in Example 1 is used, the brightness in the normal direction of the lens is improved, and the overall uniformity of the brightness distribution on the light emitting surface side is improved.

A method of manufacturing the film lens of Example 1 of the present invention will be described below with reference to FIG. First, a roll intaglio 43 having the same cross-sectional shape as the film lens of Example 1 and the same shape as that of the film lens is used, and at least the recess of the roll intaglio 43 rotating about the axis is ionized and radiation-cured by the nozzle coating device 45. The liquid 42 was filled, the strip-shaped base film 41 was sandwiched between the pressing roll 44 and the roll intaglio 43, and was made to come into contact with the roll intaglio 43 to run. As the film base material 41, a strip-shaped sheet film made of A4100 (manufactured by Tobo Co., Ltd.) single-sided adhesive color PET (polyethylene terephthalate) is used. Angle 90 °, base angle 30 ° and 60 °, long side 58
A linear engraving plate having a cm and a short side of 34 cm was used. Further, as the ionizing radiation curable resin 42, a urethane acrylate prepolymer main body was used. Then, roll intaglio 43
Are synchronously rotated at the same peripheral speed as the traveling speed of the base film 41, and while the base film 41 is in contact with the roll intaglio 43, ionizing radiation (ultraviolet ray) 46a is irradiated by an ionizing radiation device (high pressure mercury lamp) 46. Then, the ionizing radiation curable resin liquid 42 interposed between the roll intaglio 43 and the base material film 41 was cured to bring the resin and the base material film 41 into close contact with each other, and at the same time, the resin was shaped into a concave shape. Then, the base film 41 and the cured resin adhered thereto were peeled off from the roll intaglio plate 43, and a lens array having the same cross-sectional shape as that of the film of Example 1 was produced on the base film 41.

Next, a second embodiment of the film lens of the present invention will be described. The film lens of Example 2 illustrated in FIG. 1C has a 10-point average roughness of 12 μ of JIS-B-0601 on the flat side surface of the film lens of Example 1.
The fine irregularities of m are formed. The manufacturing method of this fill lens is substantially the same as that of the first embodiment, except for the step of forming fine irregularities. The fine concavities and convexities were formed by applying a UV-curable resin coating composed of urethane acrylate prepolymer, in which transparent acrylic resin beads were dispersed, with a gravure coater and curing the UV rays.

Next, examples of the surface light source of the present invention will be described.
The surface light source of the embodiment is the edge light type surface light source 10 shown in FIG. 2, and the film lens 11 is the same as the film lens of the second embodiment of the present invention. In the figure, 11 is a film lens, 12 is a light source (fluorescent lamp), 13 is a light guide plate,
Reference numeral 14 is a reflective layer, and 15 is fine unevenness. In the surface light source of this embodiment, compared with the case where a triangular prism having an apex angle of 90 ° is used for a backlight (surface light source), the brightness in the normal direction on the light output side is improved, and the desired angle necessary for the observer. In the range, the brightness was made uniform throughout.

[0018]

As described above, the film lens of the present invention can improve the brightness in the normal direction and the uniformity of the brightness distribution in a surface light source (backlight) device.

[Brief description of drawings]

FIG. 1 is a perspective view of a film lens of the present invention.

FIG. 2 is a surface light source body of the present invention.

FIG. 3 is a diagram for explaining an optical path in the film lens of the present invention.

FIG. 4 is a diagram for explaining an optical path in the film lens of the present invention.

FIG. 5 is a diagram for explaining an optical path in the film lens of the present invention.

FIG. 6 is a schematic diagram for explaining a method for producing a film lens of the present invention.

FIG. 7 is a diagram for explaining a surface light source.

FIG. 8 is a diagram for explaining an angular distribution of light emitted from a light guide plate of an edge light type surface light source.

FIG. 9 is a diagram for explaining an optical path in an isosceles triangular prism type lenticular lens having an apex angle of 90 °.

[Explanation of symbols]

1,1a film lens 2 Base film 3 lens part 3A, 3B triangular prism 4 Fine unevenness α vertical angle β base angle γ Base angle L1 long side length L2 short side length 10 surface light source 11 film lenses 12 light sources 13 Light guide plate 14 Reflective layer 15 Fine unevenness 40 film lenses 41 Base film 42 Radiation curable resin 43 roll intaglio 44 Press roll 45 nozzle coating equipment 46 Ionizing radiation device 46a Ionizing radiation

Claims (4)

(57) [Claims] 1. An output control lens used on the light output side of a surface light source used for display or the like, wherein one surface of a transparent substrate has main cutting surfaces having the same apex angle, Two kinds of unit lenses, which are axisymmetric and mirror-image-shaped and have a non-isosceles triangular shape, are arranged adjacent to each other so that their ridge lines are parallel to each other, and the other surface is a flat surface. A film lens for surface light source, which is characterized in that 2. The film lens for surface light source according to claim 1, wherein fine irregularities having a height of not less than the maximum wavelength of the light source and not more than 100 μm are formed on the flat surface of the film lens. 3. A flat surface of the film lens has a height Δh with respect to a maximum wavelength λ max of light from a light source for observing this lens, and an angular radius Δθ of the light source observed through a reflecting surface on the film lens. The film lens for a surface light source according to claim 1, wherein fine irregularities satisfying Δh ≧ λmax / 2Δθ ² are provided. 4. A surface light source used for display or the like, wherein the light control lens on the light exit side is used as a light control lens.
A surface light source using the described film lens.