JP2001265267A - Image display sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image display sheet capable of preventing degradation of a contrast of a transmissive image by internal lighting and enhancing the visibility of an internal lighting display image effectively, while enhancing luminance of a transmissive image by using base material high in transparency. SOLUTION: The image display sheet (10) is provided with the light transmissive base material (1) consisting of a laminated film containing a plurality of polymer layers and a light transmissive image layer (2) which is fixed on the surface of the light transmission base material (1) and includes the light transmissive image, and forms an image part of an inner lighting display device by being fixed being stretched by a frame of the inner lighting display device. The image layer (2) comprises a laminate containing the base layer (3) containing a light transmiissive polymer, the first image forming layer 4 fixed on the base layer 3 surface and the second image forming layer (5) fixed on the base layer (3) back surface. The light transmissive image has 100-800 μm thickness as a whole including a superimposing image formed from the first image forming layer (4) and the second image forming layer (5).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display sheet for an internally illuminated display device (for internally illuminated) used for an internally illuminated signboard, an internally illuminated sign and the like. The image display sheet of the present invention
It is suitably used in an internally illuminated display device using a frame to form an internally illuminated image portion. That is, it can be fixed to the frame of the internal illuminated display device while being pulled (that is, under tension) and used to form an image portion of the internal illuminated display device.

[0002]

2. Description of the Related Art Up to now, as an image display sheet for forming an image portion of an internally illuminated display device, for example, a soft print layer for printing an image on the surface or both surfaces of a scrim made of synthetic fiber cloth. A flexible laminated sheet having a vinyl chloride resin layer is used.
Further, a sheet using an acrylic resin or a fluorine resin is used for improving the durability to ultraviolet rays.

[0003] For example, Japanese Patent Application Laid-Open No. 7-198946 discloses a technique in which a thermoplastic resin film is laminated on at least one surface of a fiber cloth scrim, and a fluorine-based resin having a hydrophilic functional group on the film surface is formed on the thermoplastic resin film. A base material used for an image display sheet for internal lighting in which a resin film is laminated via an adhesive is disclosed. The fiber is generally a fiber made of a synthetic resin such as a polyester-based, polyamide-based, polyolefin-based, or polyaramid-based resin, and is, for example, a continuous yarn having a filament shape or a slit shape. Further, among the fabrics, a warp layer composed of a large number of warps arranged in parallel with each other, and a weft layer composed of a large number of wefts arranged in parallel with each other in a direction perpendicular to the warp, are overlapped, and the warp and the weft are overlapped. Are particularly preferably used.

[0004] The image display sheet is fixed to the frame of the internally illuminated display device while being pulled (that is, under tension) to form an image portion. Therefore, in the case of a single-layer polymer film substrate, the image display sheet is fixed to the frame. Sometimes breaks (torn, etc.). In that regard, a display sheet using a scrim having a stitch structure as described above as a base material,
It is preferable from the viewpoint of mechanical (or mechanical) strength. However, when an image display sheet using a scrim made of a fabric is observed in an internally illuminated state, the scrim fiber (stitch) is visually recognized, and the appearance of the image surface may be deteriorated.

[0005] Therefore, there has been proposed a base material for an internally illuminated image display sheet which has improved mechanical strength without using such a fiber scrim. For example, JP-A-6-19
No. 8818 discloses a flexible and optically uniform sign face base sheet as such a base material. The base sheet includes a base made of a multilayer transparent film formed by laminating a plurality of layers of a thermoplastic resin sheet. In order to effectively increase the strength of the substrate, a laminated structure in which the substrate contains more than five layers is suitable. The laminated structure of such a substrate is preferably a structure in which layers of rigid polyester (or copolyester) and layers of ductile polymer material are alternately laminated.

In a preferred example, the rigid polyester is polyethylene terephthalate and the ductile polymeric material is (1) the reaction product of terephthalic acid, sebacic acid and ethylene glycol, (2) terephthalic acid, sebacic acid and cyclohexane. Reaction products of dicarboxylic acids,
(3) 1,4-cyclohexanedicarboxylic acid, 1,4-
It is taught that it is better to be selected from the group consisting of the reaction product of cyclohexane dimethanol and polytetramethylene ether glycol, and (4) polyethylene co (co) vinyl acetate.

[0007] Such a base sheet is preferably used as follows. First, after the image layer is laminated on the base sheet, it is arranged while being pulled by the frame of the internal illuminated display device, and then the base sheet is pressed and fixed by a mechanical fixing tool or the like. Further, it is preferable to heat the base sheet after fixing to the frame. Heating causes the underlying sheet to shrink and tension in the frame, effectively removing sheet slack and surface wrinkles.

[0008]

Problems to be Solved by the Invention Incidentally, a polymer sheet containing no fabric, such as the above-mentioned base sheet, has high transparency. Therefore, as a result of the study of the present inventors, it has become clear that the following problems occur when the image layer is used as it is on the base sheet and the image is observed while the image is internally illuminated. As described above, the image display sheet is mechanically fixed to the frame. The frame is arranged on the front of a box housing the light source for internal illumination. The light from the light source is
The light enters the sheet from the back surface of the image display sheet, passes through the base material, and reaches the light-transmitting image layer. The light that reaches the image layer illuminates so that the light-transmitting image contained in the image layer can be visually recognized by an observer.

The image layer usually includes a base layer containing a light-transmitting polymer, and an image forming layer such as a printing layer laminated only on one of the front surface and the back surface of the base layer. The image formed by the image forming layer reflects external illuminating light and is visually recognized as a reflected image when external illuminating light (external illuminating light) is relatively large, such as during the day. On the other hand, when the external illumination is relatively low, such as at night,
The transmitted image due to the internal illumination is visually recognized.

When the transparency of the base material is high, it is advantageous to increase the brightness of a transmission image due to internal illumination. However,
When the transparency of the substrate was high, it was found that the contrast of the transmission image was reduced and the visibility was reduced. Further, the above publication does not disclose an improvement of an image layer for solving such a problem when a laminated transparent film is used as a base material.

[0011] Accordingly, an object of the present invention is to use a highly transparent substrate and increase the brightness of a transmission image,
It is an object of the present invention to provide an image display sheet capable of effectively preventing a decrease in contrast of a transmitted image due to internal illumination and effectively improving visibility of an internal illumination display image.

[0012]

Means for Solving the Problems According to the present invention, (1) a light-transmitting substrate composed of a laminated film containing a plurality of polymer layers, and (2) a light-transmitting substrate fixed to the surface of the light-transmitting substrate A light-transmissive image layer including a light-transmissive image, and being fixed while being pulled on a frame of the internal light display device, forming an image portion of the internal light display device. Wherein the image layer comprises: (a) a base layer containing a light-transmitting polymer; (b) a first image forming layer fixed to the surface of the base layer;
And a second image forming layer fixed to the back surface of the base layer. The light transmissive image is a superimposed image formed by the first image forming layer and the second image forming layer. Includes a total of 100
An image display sheet having a thickness of ８００800 μm is provided.

In the present invention, the base layer preferably contains a white pigment, and the image layer further includes a support layer fixed to the back surface of the second image forming layer. It preferably contains a transparent polymer and a white pigment.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. First, the present invention will be described in terms of operation. As described above, usually, the image display sheet is mechanically fixed to the frame under tension, and is arranged on the front surface of the box housing the light source. The internal illumination enters the sheet from the back side of the image display sheet, passes through the base material,
A light-transmissive image layer is reached. The light that reaches the image layer illuminates so that the light-transmitting image contained in the image layer can be visually recognized by an observer. Thus, usually the substrate, the base layer of the image layer and the two image forming layers are light transmissive.

A light-transmitting substrate composed of a laminated film including a plurality of polymer layers has high transparency, and therefore, when an image is composed of one image forming layer, the contrast of a transmitted image due to internal illumination is reduced. , Visibility is reduced. However, in the image display sheet of the present invention, the light transmissive image is configured to include the superimposed image formed from the first image forming layer and the second image forming layer respectively disposed on the front surface and the back surface of the base layer. Have been. As a result, the contrast of the transmission image can be increased, and visibility due to internal illumination can be effectively increased.

The base layer of the image layer contains a light transmitting polymer. On the other hand, when the light transmitted through the light-transmitting image is diffuse light, the visibility of the transmitted image is effectively enhanced, so that the base layer is dispersed in the light-transmitting polymer and the light-transmitting polymer. It is preferable to include light diffusion particles such as a white pigment. When the base layer contains light diffusing particles, the visibility of the reflected image is also effectively increased. In order to effectively increase the mechanical strength of the image layer, it is preferable to further include a light-transmitting support layer fixed to the back surface of the second image forming layer.

On the other hand, when the base layer includes a support layer, the support layer is preferably made of a light-transmitting material in order to make the light transmitted through the light-transmitting image into diffused light and effectively enhance the visibility of the transmitted image. It contains a polymer and light-diffusing particles such as a white pigment dispersed in a light-transmitting polymer. When the support layer contains light diffusing particles, the base layer may be substantially free of a white pigment in order to effectively enhance the visibility of the reflected image. The fact that the base layer does not substantially contain a white pigment means that the light transmittance (total light transmittance measured by a spectrophotometer) of the base layer is 80% or more.

As described above, the image display sheet of the present invention is mechanically fixed to the frame under tension. Therefore, it is necessary to have both sufficient elongation and strength against tension. From such a viewpoint, it is necessary that the entire image display sheet has a thickness of 100 to 800 μm. If the thickness is less than 100 μm, the strength is reduced, and there is a possibility of breakage during use.
If it is larger than μm, the elongation is reduced, and it may not be possible to fix the frame to the frame under tension. If the image display sheet is not fixed to the frame under tension, the image display sheet may be wrinkled or sagged, thereby impairing the appearance of the image. From such a viewpoint, the thickness of the entire image display sheet is preferably 150 to 700 μm, and more preferably 200 to 700 μm.
６００600 μm.

On the other hand, the image layer preferably contains a light-transmitting polymer having sufficient strength with respect to the tension when fixed to the frame. Accordingly, the light-transmitting polymer of the base layer preferably comprises an ionomer. The base layer containing the ionomer has sufficient light transmittance and strength against tension. The light-transmitting polymer contained in the support layer of the image layer for reinforcing the strength preferably also contains an ionomer. The support layer containing the ionomer has both sufficient light transmittance and strength against tension.

The ionomer is an ionic copolymer containing an alkali metal or an alkaline earth metal and having an ionic bridge bond by the metal ion. For example,
And a salt of an ethylene-acrylic acid copolymer. Also,
The ionomer-containing layer is a polymer other than the ionomer,
For example, those containing a polyolefin homopolymer or a polyolefin copolymer can be used.

On the other hand, the ionomer is easy to print when the image forming layer is formed on the base layer by electrostatic printing, has good adhesion of printing toner, and is easy to handle at the time of processing such as cutting an image display sheet. The properties (workability) are also good. Therefore, it is not particularly necessary to include a plasticizer in the layer containing the ionomer (base layer or support layer). Since the plasticizer bleeds out over time on the surface of the layer containing it and causes peeling or floating of another layer fixed on that layer, it is preferable to avoid using a cross-linking agent as much as possible. It is. From such a point, using the ionomer as the light-transmitting polymer of the base layer and / or the support layer also acts to increase the durability of the image display sheet.

Various additives can be added to the base layer and / or the support layer as long as the effects of the present invention are not impaired. As additives, for example, heat stabilizers, antioxidants, light stabilizers, transparent beads (such as glass beads), inorganic powder fillers, antistatic agents, thickeners, dyes, pigments, phosphors, flame retardants, etc. It is.

[0023]

Next, a preferred embodiment of the present invention will be described in detail with reference to the drawings. As shown in FIG. 1, an image display sheet (10) of the present invention is provided with a light-transmitting substrate (1) made of a laminated film, and fixed to the surface of the light-transmitting substrate (1). A light-transmissive image layer (2) containing an image. The image layer (2)
(a) a base layer (3) containing a light-transmitting polymer; and (b) a first image forming layer (4) fixed to the surface of the base layer.
And (c) a second image forming layer (5) fixed to the back surface of the base layer. As described above, the image layer (2) preferably includes a light-transmitting support layer (6) fixed to the back surface of the second image forming layer (5). Thereby, the strength of the image layer can be effectively increased.

In the illustrated example, the first image forming layer (4) is formed of a toner layer applied on the base layer (3) by an electrostatic printing method. On the other hand, the second image forming layer (5) is formed from a toner layer applied on the support layer (6) by an electrostatic printing method. In addition, each image forming layer can also be formed by a printing method other than electrostatic printing, for example, inkjet printing. In addition, a light-transmissive marking film may be used to form an image by a cutting method such as a cut character, and then bonded to form an image. Further, it can be formed by bonding an image formed on a transparent adhesive film.

The light transmissive image due to internal illumination is formed by light from a light source (in FIG. 1, represented by an arrow (8)).
The light passes through the image display sheet (10) and is observed from the front side of the display sheet (10). The light transmissive image includes a superimposed image formed from the first image forming layer (4) and the second image forming layer (5). Such a superimposed image is usually effectively visible due to the overlapping appearance of the first image forming layer (4) and the second image forming layer (5), which form substantially identical images. In the illustrated example, the support layer (6) and the base layer (3) on which the respective image forming layers are formed are laminated by adjusting the degree of overlap (position) of the respective image forming layers (4, 5). are doing. The support layer (6) and the base layer (3) are fixed to each other via an adhesive layer fixed to the back surface of the base layer (3).
Thereby, the second image forming layer (5) is fixed to the back surface of the base layer (3) via the adhesive layer.

As the adhesive used for laminating and fixing the above layers, a pressure-sensitive adhesive, a heat-sensitive adhesive, or the like can be used. For example, an acrylic, natural or synthetic rubber, silicone, silicone polyurea, polyurethane, or polyolefin adhesive is used. In order to fix the image forming layer to the base layer (3) and the support layer (6), for example, an electrostatic printing system "Trademark: Scotch Print System" manufactured by 3M Co., Ltd. is used, and a computer is combined therewith. Therefore, it is preferable to accurately control the position, dimensions, and the like on the printing surface.

In the case where the support layer (6) is not included, the first image forming layer (4) and the second image forming layer (4) are formed on both sides of the base layer (3) using the electrostatic printing system as described above. The image forming layer (5) can also be fixed. Although the thickness of each image forming layer is preferably as thin as possible, it is usually 50 μm or less, preferably 0.1 μm or less.
1 to 30 μm.

The base layer (3) contains an ionomer as a light-transmitting polymer. Such a base layer (3)
Can be obtained, for example, by molding a polymer raw material containing an ionomer into a sheet shape using a melt extrusion molding method. The thickness of the base layer (3) is not particularly limited, but is usually 20 to 400 μm, preferably 30 to 300 μm.

The support layer (6) contains an ionomer as a light-transmitting polymer. Such a support layer (3) also
Like the base layer, it can be obtained by molding using a melt extrusion molding method. The thickness of the support layer (6) is also not particularly limited, but is usually 10 to 300 μm, preferably 20 to 250 μm.
m.

In the illustrated example, the base layer (3) is a milky white layer further containing a white pigment (such as titanium dioxide) dispersed in the ionomer. Thereby, the light transmitted through the light-transmitting image is made into diffused light, and the visibility of the transmitted image is effectively enhanced. On the other hand, although different from the illustrated example, the support layer may contain a light-transmitting polymer and a white pigment in order to effectively enhance the visibility of the transmission image. The light transmittance of the layer containing such a white pigment is usually 10 to 60%.

On the other hand, when the image display sheet of the present invention is provided in an internal light display device, the first image forming layer (4) is located outside. Therefore, it is preferable to arrange the surface protective layer (7) in order to increase the durability of the first image forming layer. The surface protection layer (7) is fixed in the image layer so as to cover the first image forming layer (4).

The surface protective layer (7) can be formed using, for example, a light-transmitting polymer film and an adhesive clear film provided with an adhesive layer on the back surface of the film.
The surface protective layer (7) is preferably one that can effectively prevent deterioration of the material of the image layer due to ultraviolet rays and fading of the image outdoors. Therefore, it is preferable that at least one or both of the acrylic polymer and the fluorine-based polymer are blended and contained.

The surface protective layer (7) can also be formed by a clear coating film, a thermally transferred thermoplastic film, or the like. In addition, the thickness of the protective layer (7) is not particularly limited, but is usually 1 to 150 μm, and preferably 5 to 100 μm. As the light transmissive substrate (1), for example, a sign face base sheet disclosed in the above-mentioned JP-A-6-198818 can be used.

The light-transmitting substrate (1) is usually a laminated film comprising a layer of polyester (including copolyester) and a stretched polymer layer, which are alternately laminated. The thickness of the laminated film is usually 7 to 500
μm, preferably 15 to 185 μm. The thickness of the polyester layer is usually 0.5 to 75 μm, preferably 1 to 25 μm.
μm. The thickness of the stretched polymer layer is preferably smaller than that of the polyester layer. The light-transmitting substrate (1) preferably contains at least five polymer layers, and particularly preferably contains six to 35 layers.

As the polyester, those having a high tensile modulus are suitable. The tensile modulus of the polyester preferably has a tensile modulus of greater than 200 kpsi (1,380 MPa), and particularly preferably greater than 400 kpsi (2,760 MPa) at a given temperature (typically about 25 ° C.). Useful polyesters are polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polybutylene naphthalate, and blends thereof. On the other hand, also useful polymers of the stretched polymer layer, polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate,
Polybutylene naphthalate, and blends thereof, can be used. In such a case, the stretched polymer layer and the polyester layer may be formed from the same material, or may be formed from different materials.

Other suitable materials that can be used for the stretched polymer layer include ethylene-vinyl acetate, ethylene-
Copolymers such as acrylic acid, ethylene-methyl acrylate, ethylene-methacrylic acid, ethylene-methyl methacrylate, ethylene-ethyl acrylate, ethylene-ethyl methacrylate, and ionic copolymers such as ionomers. The laminated film is preferably formed into a film by the co-extrusion method using the above-mentioned materials.
The light transmissive substrate (1) is usually transparent, but may be translucent milky white or translucent colored.

As described above, the image display sheet of the present invention can be suitably formed by using the above constituent materials. The thickness of each layer is appropriately determined so that the thickness of the entire display sheet (T in FIG. 1) is in the range of 100 to 800 μm.

Finally, a more specific embodiment will be described. An image display sheet according to the present invention was produced using the following materials for each layer. The thickness of the entire image display sheet was about 365 μm.

Protective layer 3M Co., Ltd. [trademark: Scotchcal, product number SP4114 / fluorine / acrylic transparent film with adhesive (total thickness = 60 μm)] Image forming layer (same for both first and second) Electrostatic printing toner layer base layer 3M Co., Ltd. [trademark: Scotchcal, product number 8633 / ionomer-based milky translucent film with adhesive (total thickness = 110 μm) formed by the above-mentioned (trademark) Scotch print system )]

Support layer 3M Co., Ltd. [Trade name: Scotch Cal, product number 8908 / Ionomer-based transparent film with adhesive (total thickness = 8)
0 μm)] Light-Transmissive Substrate A transparent laminated film comprising a PET layer / stretched coPET (sebacic acid) layer produced by the method disclosed in the above-mentioned JP-A-6-198818. The number of layers is 13, the total thickness =
It was 100 μm.

As Comparative Example 1, a device in which the second image forming layer was omitted was manufactured. The visibility of the transmitted image due to internal illumination was compared between Comparative Example 1 and the example. As a result, in the image display sheet of the example, the contrast of the transmission image was higher, and the visibility by internal illumination was able to be effectively improved. As Comparative Example 2, a conventional milky white translucent sheet (thickness = 600 μm) formed from a plasticized vinyl chloride layer and a polyester fiber scrim.
An image display sheet was produced in the same manner as in the example except that was used as a base material. About Example and Comparative Example 2,
The characteristics shown below were evaluated. Table 1 shows the results. The evaluation method was as follows.

(Test Method) * Visibility of inside / outside illumination image: The image was visually observed under the inside illumination and under sunlight. * Base material strength: Measured by measuring the breaking strength at 25 mm width (3
(Tensile test at 00 mm / min). * Interlayer adhesive strength (room temperature): 20 ° C for 48 hours after fabrication
And measured in a peel test (180 °, 300 mm / min) between the substrate and the support layer in a width of 25 mm. * Interlayer adhesion strength (after heating): 65 ° C for one week after production
And measured in a peel test (180 °, 300 mm / min) between the substrate and the support layer in a width of 25 mm.

[0043]

[Table 1]

[0044]

As described above, according to the image display sheet of the present invention, the image display sheet has the same mechanical strength as the fiber scrim, and has a good appearance in both the reflection image (sunlight) and the transmission image (internal illumination). And high visibility. Furthermore, by employing a resin without a plasticizer in each layer, a remarkable effect that interlayer adhesion strength is improved and durability is enhanced is exhibited.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view showing an embodiment of an image display sheet according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Light transmission base material, 2 ... Image layer, 3 ... Base layer, 4
... first image forming layer, 5 ... second image forming layer, 6 ...
Light transmitting support layer, 7: surface protective layer, 10: image display sheet.

Claims (3)

[Claims] (1) a light-transmitting substrate formed of a laminated film including a plurality of polymer layers; and (2) a light-transmitting substrate fixed to a surface of the light-transmitting substrate and including a light-transmitting image. An image display sheet comprising: an image layer; and an image display sheet that is fixed to the frame of the internal light display device while being pulled and forms an image portion of the internal light display device. A laminate comprising: a base layer containing a polymer; (b) a first image forming layer fixed to the surface of the base layer; and (c) a second image forming layer fixed to the back surface of the base layer. The image display sheet, wherein the light transmissive image includes a superimposed image formed from the first image forming layer and the second image forming layer, and has a thickness of 100 to 800 μm as a whole. . 2. The image display sheet according to claim 1, wherein the base layer contains a white pigment. 3. The image layer further comprises a support layer fixed to a back surface of the second image forming layer, wherein the support layer contains a light-transmitting polymer and a white pigment. Image display sheet.