Retroreflection sheet and outer illumination type illumination system

Abstract

The retroreflective sheet of the present invention comprises a surface layer ( 1 ) including at least one layer, a focusing layer ( 2 ) containing glass spheres ( 3 ), and a metal reflective layer ( 4 ) on the back side of the focusing layer ( 2 ), wherein the glass spheres ( 3 ) are disposed at random locations in the thickness direction of the focusing layer ( 2 ). The external illumination system of the present invention comprises a sign having a sign face including the above-mentioned retroreflective sheet, and an external illumination source, and the distance from the illumination source to the sign face is within a range of at least 1 m and no more than 100 m. The present invention thereby provides a retroreflective sheet and an external illumination system with which wide-angle reflective performance with a wider incidence angle and observation angle can be ensured.

Description

technical field [0001] The invention relates to a retroreflective sheet and an externally illuminated lighting system used for road signs, guide signs, safety guide sign boards, safety instructions, billboards and the like. Background technique [0002] Retroreflection (retroreflection) sheets are widely used in various purposes such as traffic signs, guide signs, warning signs, regulatory signs, car license plates, and billboards. As an example of this retroreflective sheet, there is a so-called enclosed lens type retroreflective sheet, which is laminated with a surface layer formed of at least one layer, high refractive index glass beads, and a focus layer (also called a focus resin layer) in the following order. , Metal reflective layer. In addition, as another structure, there is a retroreflective sheet called a capsule lens type, which is composed of a plurality of transparent balls provided with mirrors in the lower hemisphere, a supporting resin sheet holding the afo...

AI Technical Summary

Problems solved by technology

That is, there is a problem that since the car driving in the leftmost lane observes the light irradiated from the external light projector at a small viewing angle, the amount of light returned from the sign is relatively large, so it can be seen clearly, but it is difficult for driving The viewing angle of the car in the far right lane is very large, so the amount of light returning from the sign is greatly reduced and it looks very dark

[0014] In addition, when the microprism-type retroreflective sheeting is exposed to light from an oblique or lateral direction, it is difficult to maintain the retroreflective performance, so the wave reflector makes the shape of the aforementioned microprism-type retroreflective sheeting wave-shaped, and the light irradiated from oblique or lateral directions is opposite to each other. As the incident angle of the aforementioned retroreflective sheeting decreases to allow light to enter, the brightness of the retroreflection increases as a result, but the retroreflective sheeting itself does not have wide-angle performance.

In addition, it is extremely difficult to print on the wave reflector by methods such as screen printing in order to shape it into a wave shape, so there is a problem that the necessary information is incorporated into the retroreflective sheet before the wave shape is formed, and then the shaping process must be performed. , which has the problem of raising the cost of

In addition, the inner surface of the wave reflector has a large wavy depression, and when it is attached to the side wall of the road, impurities such as garbage will be stored in the depression, and there is also a problem that the appearance of the film will be significantly damaged.

[0015] In addition, the aforementioned wide-angle prism-type retroreflective sheeting (VIP) is not designed to irradiate light from oblique or lateral directions and exhibit retroreflective performance at relatively large viewing angles.

For example, at an observation angle of 4° and an incident angle of 40° or more, there is a problem that retroreflection performance can no longer be maintained

[0016] In addition, in the case of a wide-angle prism type retroreflective sheeting for side display (EV-9010 manufactured by 3M Company), when the observation point is located in the lateral direction (display direction) of the sheeting, even at a large observation angle and a large incidence Retroreflection performance can be maintained at any angle, but when the observation point is in the longitudinal direction (up and down direction) of the sheet, there is a problem that if the incident angle exceeds 60°, the retroreflection performance will be extremely low.

[0022] In addition, as the reflective sheet proposed in the aforementioned Patent Document 4 ( Figure 8 As shown in D), if the focus layer is formed so that the side surface of the glass bulb retroreflects the reflected light as the reflected light g2 approximately parallel to the incident light g1, the incident light f1 from the front direction diffuses from the incident direction as reflection The problem of light f2 retroreflection

Therefore, the status quo is that even if the reflective performance can be obtained at a large viewing angle, it is far from meeting the Japanese Industrial Standard (JIS) and overseas marking standard values ​​of the reflective performance required in the frontal direction with a relatively small viewing angle.

Therefore, the use is limited, and it cannot be used for general traffic signs, and it is also difficult to be used for license plates of automobiles, etc., so that it cannot meet the needs of the market in terms of practicality.

[0023] As mentioned above, the existing lens-enclosed retroreflective sheeting has a large angle dependence, and cannot sufficiently ensure wide-angle reflection performance at relatively large observation angles and relatively large incident angles.

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