TECHNICAL FIELD

The present invention relates to an optical member for use in illumination devices, image displaying devices, and the like. More particularly, the present invention relates to an optical member which, when integrated with a lightguide, is able to selectively extract light from the lightguide.

BACKGROUND ART

In order to extract light from a lightguide, a lightguide having concave-convex shapes formed on the surface thereof has conventionally been used. In making a lightguide having such concave-convex shapes on the surface, according to the purpose and dimensions, it is necessary to make a mold of the concave-convex shapes each time. In such a lightguide having concave and convex parts, while the presence of air in contact with the concave-convex shapes plays a geometrically important role for light extraction, the lightguide is difficult to be made thin or laminated with other members. Furthermore, as the concave-convex shapes need to be made more precise and complex for realizing multiple functions, the production of lightguides is becoming time-consuming and costly, among other problems.

On the other hand, Patent Document 1 proposes that: a variable-refractive index light extraction layer having a geometric arrangement of two regions of different refractive indices be made; and, when it is integrated with a lightguide, light be selectively extracted from the lightguide.

CITATION LIST

Patent Literature

Patent Document 1: Japanese National Phase PCT Laid-Open Publication No. 2015-534100

SUMMARY OF INVENTION

Technical Problem

The inventors have studied Patent Document 1, and found that the three points as detailed below need to be improved.

Firstly, as shown inFIG. 1, the light extraction layer disclosed in Patent Document 1 includes low-refractive index layers1and a high-refractive index layer2disposed along the planar direction of the light extraction layer, such that an interface exists at which regions of considerably different refractive indices adjoin, and therefore light scattering due to reflection or refraction at the interface occurs, possibly causing leakage of light.

Secondly, according to the method of producing a light extraction layer disclosed in Patent Document 1, as shown inFIG. 2, the spaces between regions of low refractive index (first region; low-refractive index layers1) are not sufficiently filled with a second region (high-refractive index layer2) having a higher refractive index than that of the first region, thus leaving air layers3, so that not only is there a risk of light scattering, but there is also a risk of insufficient mechanical strength due to the light extraction layer not being sufficiently bonded to the lightguide.

Thirdly, since regions of low refractive index inherently include porous structures, regions of low-refractive index are very brittle and difficult to handle. In addition, there are extreme manufacturing difficulties in creating partial coatings of low refractive index regions on a support substrate.

A problem to be solved by the present invention is to provide an optical member which suffers little light scattering and achieves excellent mechanical strength when being integrated with a lightguide, the optical member enabling selective extraction of light, and a method of easily producing such an optical member.

Solution to Problem

The present invention has been made in view of the above problem, and summary of the present invention is as follows.

An optical member comprising:a first layer that includes a first region having a refractive index n1and a second region having a refractive index n3; anda second layer disposed on a first main surface of the first layer so as to be in contact with the first region and the second region, the second layer having a refractive index n2, wherein,the first layer includes a plurality of said second regions adjoining the first region along a planar direction of the first layer;the plurality of second regions constitute a geometric pattern; andn1to n3satisfy inequality (1) below.
n1<n3<n2(1)

Advantageous Effects of Invention

According to the present invention, when an optical member according to the present invention is integrated with a lightguide in use, an effect is provided in that excellent light extraction function is exhibited and leakage of light due to light scattering is suppressed, while good mechanical strength is attained at the same time.

