JPH10187071A - Internal lighting type display instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal lighting type display instrument that can efficiently emit light from a display part. SOLUTION: The internal lighting type display instrument 1, which is provided with a light source 2 inside a housing 5 and equipped with a light reflection part 4 reflecting a projection light from the light source 2 and a display part 3 transmitting the projection light from the light source 2 and a reflected light from the light reflection part to the outside of the housing at least a part of the housing internal wall is constituted so that the light reflection part 4 is formed from a thermoplastic polyester resin foamed body of <=50μm in a mean air bubble diameter, >=0.2mm in as thickness and <=0.7 in a specific gravity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internally illuminated display device used for road signs, various signs, medical or photographic light boxes, and the like.

[0002]

2. Description of the Related Art FIG. 1 shows an example of the structure of a general internally illuminated display device. The internally illuminated display device 1 shown in FIG. 1 is configured such that a light source 2 is provided inside a housing 5 having a light reflecting portion 4 and a display portion 3 on a part of an inner wall. FIG. 1 shows a state in which the display unit 3 is removed from the housing 5 to explain the internal structure of the housing 5. The light emitted from the light source 2 and the light emitted from the light source 2 and reflected by the light reflection unit 4 are emitted from the display unit 3. Such an internally illuminated display device is used for a medical or photographic light box, or designed on a display unit 3 to design pictures and characters, and to display the pictures and characters effectively in a dark place. It can be used as a road sign and various signs. Therefore, it is desirable that the illuminance of the display unit 3 is as large as possible, and that the light is emitted from the display unit 3 as uniformly as possible. Conventionally, a metal material such as an aluminum plate or a steel plate coated with a paint containing a light-reflective pigment has been used as the light reflecting portion of the housing, and a milky white acrylic plate or the like has been used as the display portion 3. .

[0003]

However, the light reflecting portion 4
In the case where a white painted metal material is used, if the output of the light source is increased in order to obtain sufficient illuminance from the display unit 3, a problem occurs that the shape of the light source 2 can be seen through the display unit 3. In some cases, sufficient illuminance was not obtained as a part. If the distance between the light source 2 and the display unit 3 is increased, this can be improved to some extent, but it is not preferable because the size of the display device cannot be avoided.

An object of the present invention is to solve the above problems and to provide an internally illuminated display device capable of efficiently emitting light from a display unit.

[0005]

That is, in the present invention, a light source is provided inside a housing, and at least a part of the inner wall of the housing has a light reflecting portion for reflecting light emitted from the light source, and a light source. And a display part for transmitting the light emitted from the light source and the reflected light from the light reflection part to the outside of the housing. The light reflection part has an average bubble diameter of 50 μm or less and a thickness of 0.1 μm.
An internally illuminated display device is provided which is formed of a thermoplastic polyester resin foam having a specific gravity of 2 mm or more and 0.7 or less.

[0006]

FIG. 1 shows an embodiment of an internally illuminated display device of the present invention. The internally illuminated display device 1 shown in FIG. 1 is configured such that a light source 2 is provided inside a housing 5 having a light reflecting portion 4 and a display portion 3 on a part of an inner wall. In the present invention,
The light reflecting portion 4 has an average bubble diameter of 50 μm or less and a thickness of 0.5 mm
As described above, it is formed of a thermoplastic polyester resin foam having a specific gravity of 0.7 or less.

In the present invention, the average cell diameter, sheet thickness and specific gravity of the thermoplastic polyester resin foam are specified as described above for the following reasons. When the average bubble diameter exceeds 50 μm, the number of times that light from the light source diffusely reflects at the bubble interface decreases, and light penetrates into the light reflecting portion, so that the light is absorbed by the light reflecting portion itself. And the total reflection and diffuse reflectance tend to decrease. The average bubble diameter is preferably 50 μm or less, more preferably 30 μm or less. 50μ
When it is less than m, not only the total reflectance but also the diffuse reflectance increases. If the diffuse reflectance is insufficient even if the total reflectance is large, the light reflected from the light reflector 4a located on the opposite side of the display unit 3 with respect to the light source (the back side of the light source) is used to form the light source. Are visible from the display. 50μm average bubble diameter
The following is preferable because the light from the light source is sufficiently diffused by the reflection unit 4 and uniformly emitted from the entire display unit 3. When the average bubble diameter is smaller than the light wavelength, the incident light passes therethrough. Therefore, the average bubble diameter needs to be at least the light wavelength.

When the thickness of the foam is less than 0.2 mm,
Even if other requirements are met, there is more light leakage to the back of the foam. When the foam is provided as a light reflecting portion on the inner wall of the housing, if the foam has a thickness of 0.2 mm or less and is not self-supporting, some kind of support is required when the foam is disposed inside the housing. For example, the work becomes complicated, and workability when molding the foam into various shapes is deteriorated. Therefore, the thickness of the foam is practically 0.2 mm or more, more preferably 0.5 mm or more.

The specific gravity of the foam is 0.7 (bubble rate of about 52%)
Is exceeded, the leakage of light to the back surface of the foam increases due to the transparency of the foam even if other requirements are satisfied, so that the light loss increases. Particularly preferred specific gravity is 0.5 or less.

Hereinafter, the present invention will be described in more detail. Examples of the thermoplastic polyester resin used in the present invention include those made of polyethylene terephthalate and polybutylene terephthalate, and those made of various polymer alloys obtained by blending polycarbonate and the like based on these resins. Among them, those made of polyethylene terephthalate are more preferable.

In the present invention, a crystallization nucleating agent, a crystallization promoting agent, a foaming nucleating agent, an antioxidant, an antistatic agent, and the like are added to the thermoplastic polyester resin before foaming within a range that does not affect the optical characteristics. UV absorbers, flame retardants, pigments, dyes,
Various additives such as a lubricant may be blended. After foaming, these additives may be applied or laminated on the foam. Of these, regarding the amount of crystallization nucleating agent added,
It is preferably at most 5% by weight, more preferably at most 2% by weight.

The method for producing the thermoplastic polyester foam used in the internally illuminated display device of the present invention is not particularly limited. For example, a roll is formed by laminating and winding a sheet-like thermoplastic polyester resin and a separator. Then, the roll is held in a pressurized inert gas atmosphere to make the sheet-like thermoplastic polyester resin contain an inert gas, and then the sheet-like thermoplastic polyester containing the inert gas is heated and foamed under normal pressure. Is used. In this method, the roll made of the sheet-like thermoplastic polyester resin and the separator is held in a pressurized inert gas atmosphere, and before the sheet-like thermoplastic polyester resin contains an inert gas, an organic solvent is previously added to the roll. May be contained.

In this method, first, a roll is formed by laminating a sheet-like thermoplastic polyester resin and a separator. The separator used here may have any space as long as the inert gas or the organic solvent used as needed has a space where the organic solvent can freely enter and exit, and the penetration of the inert gas into itself can be ignored. . In particular, a resin nonwoven fabric or a metal net is preferable. As the nonwoven fabric made of resin, a nonwoven fabric made of a polyolefin resin or a nylon resin is preferable. In addition, a non-woven fabric made of a polyester-based resin can be suitably used as long as the fiber is stretched and the inert gas is hardly permeated. As a metal net, generally called wire cloth, plain weave, twill weave, plain tatami weave,
It is preferable that the vertical line and the horizontal line are woven in a perpendicular direction in a weaving method such as a twill tatami weave. The material can be iron, copper, aluminum, titanium or their alloys.
In consideration of the life and the like, stainless steel is more preferable. It is desirable that the sheet-like thermoplastic polyester resin is not stretched. This is because if the sheet-like thermoplastic polyester resin is stretched, the gas does not sufficiently penetrate into the sheet, so that a foam having desired characteristics cannot be obtained.

When an organic solvent is contained in the sheet-shaped thermoplastic polyester resin formed into a roll, when the sheet is immersed in the organic solvent, the immersion time is preferably, for example, 1 day or more. , For example, it is preferable to keep it for 3 days or more. in this way,
When the thermoplastic polyester resin contains an organic solvent,
The crystallinity of the thermoplastic polyester resin is 30% or more, the rigidity of the resin is increased, the trace of the separator hardly remains on the sheet surface, and the permeation time of the inert gas can be shortened. Note that, depending on the type of the separator, the trace of the separator may not remain. Therefore, the treatment for containing the organic solvent is not always necessary, but it is preferable to perform the treatment from the viewpoint of shortening the gas permeation time.
Organic solvents used to increase the crystallinity of the resin include benzene, toluene, methyl ethyl ketone, ethyl formate, acetone, acetic acid, dioxane, m-cresol, aniline, acrylonitrile, dimethyl phthalate,
Examples include nitroethane, nitromethane, benzyl alcohol and the like. Of these, acetone is preferred from the viewpoint of handleability and economy.

Next, the sheet-like thermoplastic polyester resin formed into a roll is put in a high-pressure container, and is held in a pressurized inert gas atmosphere, and an inert gas serving as a foaming agent is added to the sheet-like thermoplastic polyester resin. Is contained. Examples of the inert gas include helium, nitrogen, carbon dioxide, and argon. Of these, carbon dioxide, which can be contained in a large amount in the resin, is more preferable. The permeation condition of the inert gas is a pressure of 30 kg / cm ² or more, preferably 50 kg / cm ² or more.
At a pressure of at least kg / cm ² , the permeation time varies depending on the pressure or the presence or absence of an organic solvent, but is preferably at least one hour.

Further, the sheet-shaped thermoplastic polyester resin formed in a roll shape is taken out from the high-pressure container, and only the sheet-shaped thermoplastic polyester resin containing an inert gas is heated and foamed while removing the separator.
Examples of the heating means include a hot-air circulation foaming furnace, an oil bath, and a molten salt bath, and it is preferable to use a hot-air circulation foaming furnace from the viewpoint of handling. The foaming conditions in the hot-air circulation type foaming furnace are set, for example, to a foaming temperature of about 230 ° C. and a linear velocity such that the foaming time is 1 to 2 minutes. Thereafter, the sheet-like resin foam after the heat foaming was added to 150
It is wound on a thermoforming roll whose temperature has been adjusted to not less than ° C. and cooled to obtain a desired thermoplastic polyester resin foam for a light reflecting portion of an internally illuminated display device.

The obtained thermoplastic polyester resin foam had a total reflection of 98% or more by a light reflectance measurement using a self-recording spectroscopic altimeter (UV-3101PC: manufactured by Shimadzu Corporation) with the light reflectance of the barium sulfate white plate being 100%. And a diffuse reflectance of 95% or more.

The thermoplastic polyester resin foam thus obtained is provided on the inner wall of a casing made of a steel plate, an aluminum plate, or the like, and is used as a light reflecting portion. As a method of laminating the foam on the inner wall, the foam is cut in accordance with the shape of the inner wall, and is subjected to a bending process or a secondary molding into a box shape as necessary, and is bonded with an adhesive or Various methods are possible, such as screwing or hooking on a hook provided inside the housing. As the display portion, glass, acrylic resin, polycarbonate resin, or the like is preferable in terms of light transmittance. The light source is not limited as long as it is a light source used as a light source of the internally illuminated display device. For example, a fluorescent lamp, an incandescent lamp, H
An ID lamp and the like can be mentioned. When the thermoplastic polyester resin foam according to the present invention is provided as a light reflecting portion on the inner wall of a housing that is a main body of a medical X-ray light box (Schaukasten) using a fluorescent lamp as a light source, a conventional white paint is used. The illuminance of the display unit was 1.5 times or more as compared with that of the light box in which the metal member functioned as a light reflection unit.

[0019]

Embodiments of the present invention will be described below.

(Examples 1 to 4) (Comparative Examples 2 to 5) Four types of polyethylene terephthalate (PET) sheets (C-0312 grade, manufactured by Unitika Ltd.) having different thicknesses,
An olefin-based nonwoven fabric (FT300 grade, manufactured by Nippon Vileen Co., Ltd.) was placed on top of the separator and rolled so that there was no portion where the surfaces of the PET sheet were in contact with each other. After keeping the roll in acetone-saturated steam for 3 days, the roll was taken out, placed in a high-pressure vessel, and
/ Cm ² of carbon dioxide gas was permeated for 2 to 4 hours. Next, the roll was taken out of the high-pressure container, and 0 to 12
After holding at room temperature for a period of time, while removing the separator, only the PET sheet is continuously supplied to a hot-air circulation type foaming furnace set at 230 ° C. so that the foaming time becomes 1 minute, and foamed, thereby obtaining a PET foamed sheet. Was.

The average cell diameter of the obtained PET foam sheet,
The thickness and specific gravity were measured, and the results are shown in Table 1. The average bubble diameter was determined by measuring the diameter of bubbles contained in a certain cross-sectional area from an SEM photograph of a sheet cross section, and calculating the average value. The specific gravity was measured by an underwater displacement method.

The obtained PET foam sheet is fixed to the inner wall of the housing other than the display section with screws, and the size of the display section is 56
5mm x 425mm photo light box (size 6
25 × 495 × 110, a case made of white painted steel plate, four 15 W fluorescent lamps were installed as a light source, and a milky white acrylic plate for a display unit) was produced. Further, as a conventional example, a light box having a light-reflecting portion on a white painted surface of the inner wall of the housing was prepared without providing the PET foam sheet on the inner wall of the housing.

Table 1 shows the values obtained by comparing the illuminances of the display portions of the light boxes of Examples 1 to 4, Comparative Examples 1 to 4 and the conventional example with the illuminances of the example and the comparative example based on the illuminance of the conventional example. . The illuminance of the display unit was measured by a digital lux meter (Custom Co., Ltd.) at 9 points immediately above the display unit, and the average value of the measured values was used.

[0024]

[Table 1]

The light boxes of Examples 1 to 4 use a thermoplastic polyester resin foam having an average cell diameter, thickness and specific gravity within the ranges specified in the present invention as the light reflecting portion. 1.6 to 2.1 times the illuminance as compared with. On the other hand, the light boxes of Comparative Examples 1 to 4 use foams whose average cell diameter, thickness, or specific gravity is out of the range specified in the present invention, and thus are compared with the conventional examples. The illuminance was about 0.9 to 1.2 times.

[0026]

As described in detail above, the internally illuminated display device having the specific thermoplastic polyester resin foam inside the housing suppresses the light loss inside the housing, so that the light Effective utilization becomes possible, and a brighter illuminance than the conventional product can be obtained on the display unit without increasing the output of the luminous body. Further, when trying to obtain the same brightness as the conventional product, the size of the appliance can be reduced and the power consumption can be reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view for explaining the structure of an internally illuminated display device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 internally illuminated display device 2 light source 3 display unit 4 light reflection unit 5 housing

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Naoki Yoshida 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd.

Claims (2)

[Claims] A light source is provided inside a housing, and at least a portion of an inner wall of the housing has a light reflecting portion for reflecting light emitted from the light source, and light reflected from the light source and light reflecting portion. A display unit for transmitting light to the outside of the housing, wherein the light reflection unit has an average bubble diameter of 50 μm or less, a thickness of 0.2 mm or more, and a thermoplastic polyester resin foam having a specific gravity of 0.7 or less. An internally illuminated display device characterized by being formed by a body. 2. The internally illuminated display device according to claim 1, wherein the thermoplastic polyester resin foam is a polyethylene terephthalate resin.