Display board and method for producing the same

Abstract: A display board such as used for the dial of a vehicle dashboard instrument, includes a picture layer having one or more different coloured photopolymerization resin portions applied either directly to a substrate or to a transparent photopolymerization resin layer on the substrate when the display board is not of the light transmission type the substrate need not be transparent.

Description: The present invention relates to a display board by which voluntary colored picture is formed on a substrate. Such a display board is used as a dial board of a tachometer and a speed meter of a vehicle, for example. Letters, figures or the like on a dial board of a meter are conventionally formed on a resin substrate by printing, especially by screen printing. The screen printing enables the printing of a thick paint film to provide a deep picture. However, the above screen printing uses liquid ink diluted by solvent, causing the contamination of working environment, and fire due to the evaporation of the solvent within the ink, requiring time for removing ink from a printing plate clogged therewith and controlling the viscosity of ink, and requiring skill in controlling these operations. Accordingly, recently, a photopolymerization ink containing no solvent and setting in a short time has been proposed. This photopolymerization ink takes advantage of the photosetting property of the photopolymerization resin. It has low viscosity and high fluidity before light irradiation so as not to need any solvent. However, this photopolymerization ink requires the addition of reactant type diluent(for a monomer of low molecular weight) in order to adjust the viscosity thereof so as to be suited to the screen printing. This diluent functions similarly to the solvent so that unreacted substance gradually evaporates from the paint film. Moreover, the photopolymerization ink is of a low molecular weight as a whole thus having problems of a large scaled shrinkage due to setting, shortage of adhesion, or lack of flexibility. In addition, the production cost is expensive so that the photopolymerization ink is insufficient in practical use. Moreover, multicolor printing has been desired in order to improve the appearance of the dial board, and the visibility thereof. In order to satisfy the above desire, the conventional screen printing requires printing plates and inks of the same number as that of colors. This results in the troublesome producing processes and increased production cost. Meanwhile, offset printing has mainly been adopted as the multicolor printing in the printing trade. However, in applying this offset printing to a display board, this offset printing has also probelms that ink is liquid, or the color density of each printing plate is insufficient. It is an object of the present invention to provide a display board which is capable of displaying a picture of excellent quality with voluntary colours, and a method for producing such a display board without using any solvent or reactant type diluent with the improvement of the working environment and the work efficiency. According to one aspect of the present invention there is provided a display board comprising: a receiver base (1, 31); a first coloured photopolymerised resin layer (32) including a first colouring agent of a first colour, which is directly laminated on a surface of said receiver base to form a first picture pattern in said first colour; and a second coloured photopolymerised resin layer (33) including a second colouring agent of a second colour, said second coloured photopolymerised resin layer being directly laminated both on at least a portion of said surface of said receiver base (1, 31) on which said first picture pattern is not formed, and on at least a portion of a surface of said first coloured photopolymerised resin layer (32), to form a second picture pattern on said at least a portion of said surface of said receiver base (1, 31) and on said at least a portion of said surface of said first coloured photopolymerised resin layer (32), whereby a two-dimensional non-flat display including said first and second picture patterns is formed with said second picture pattern being on at least two levels thereof with respect to the receiver base. The method according to the present invention does not require the formation of the conventional printing plates, and the preparation of ink, and accordingly is free from such problems as the troublesome viscosity control of ink, contamination of the working environment due to the evaporation of the solvent, and clogging of the printing plates . Moreover, by forming the photopolymerization resin layer into a film shape, the handling thereof is facilitated as well as the control of operations, and the automation of the production processes. Figs. 1 to 8 illustrate a first embodiment of the present invention; Fig. 1 is a partially enlarged cross-sectional view of a dial board of a tachometer for a vehicle, to which the first embodiment is applied; Fig. 2 is a front view of the dial board; Fig. 3 is an enlarged cross-sectional view of a photopolymerization resin film for the formation of a picture layer. Figs. 4(1) to 4(12) are views showing the production processes of the dial board; Figs. 5 and 6 are partially enlarged cross-sectional views of a boundary of a picture layer of the dial board; Fig. 7 is a view showing the relation between the setting degree of the colored photopolymerization resin and the picture quality; Fig. 8 is a view showing the relation between the setting degree and the film hardness; Figs. 9 and 10 illustrate a second embodiment of the present invention; Fig. 9 is a partially enlarged cross-sectional view of a display board; Fig. 10 is a view showing the adhesion improvement effect obtained in the third embodiment; Figs. 11 and 12 illustrate a fourth embodiment of the present invention; Fig. 11 is a partially enlarged cross-sectional view of a display board; Fig. 12 is a partially enlarged cross-sectional view of a picture for controlling the amount of the transmitted light; Fig. 13 is a front view of the picture for controlling the amount of the transmitted light; and Fig. 14 is a view showing the relation between the roughness of a transparent supporting member and the glossiness of a picture layer. Hereinafter, the present invention will be explained in accordance with the embodiments with reference to the drawings. Figs. 1, 2 and 3 illustrate a first embodiment wherein the present invention is applied to a dial board of a tachometer for a vehicle. In this embodiment, the picture layer is formed by successively laminating colored photopolymerization resin films, each having a predetermined picture pattern, in place of using a compound layer of dots-shaped photopolymerization resins. And the figures, scales and letters in the region W of 0 to 6 are colored white while those in the region R of 6 to 8 are colored red, for example. The background except for these figures and scales is colored black. Fig. 1 is a partially enlarged cross-sectional view of Fig. 2. A white picture layer 31 is formed on the substrate 1 made of transparent resin so as to cover the entire surface thereof. And a red picture layer 32 made of red photopolymerization resin is formed on the white picture layer 31 thereby forming the picture pattern corresponding to the figures and scales of the region R of Fig. 2. On the red picture layer 32 is formed a black picture layer 33 made of black photopolymerization resin, which corresponds to the background B. These picture layers 31, 32 and 33 compose the picture layer 3. The above-described dial board is produced as follows: Each of the picture layers 31, 32 and 33 can be made of the colored photopolymerization resin film F shown in Fig. 3. In Fig. 3, a colored photopolymerization resin layer F1 is formed on a support member F3. The surface of the colored photopolymerization resin layer F1 is protected by a protective film F2. The colored photopolymerization resin layer F1 contains a coloring agent such as pigment, or dye, photopolymerization resin(molecular weight: tens to thousands), binder polymer(molecular weight:tens of thousands to hundreds of thousands), catalyst(photopolymerization initiator), and auxiliary agent(polymerization inhibitor). By voluntarily selecting the coloring agent, the layer F1 is colored yellow, magenta, cyan or black. The density of each color is set as follows in accordance with the density range of ink for screen printing of a dial board. yellow-based ink 0.1 to 0.6 magenta-based ink 0.2 to 0.7 cyan-based ink 0.3 to 1.0 black-based ink 0.8 to 3.5 The density of each color is measured by using a transmission density meter made by Dainihon Screen Co., Ltd. with setting the clear 0 without using any filter. Examples of the photopolymerization resin are urethane acrylate, epoxy acrylate, or polyol acrylate . Especially, urethane acrylate is preferably used. And acryl-based polymer has a film property and an adhesion property suitable to the binder polymer. The transparent photopolymerization resin layer F2 has a composition substantially equal to that of the colored photopolymerization resin layer F1 except for no pigment being included. The support member F3 supports the colored photopolymerization resin layer F1 until being transferred to the transparent photopolymerization resin layer F2. The material for the support member F3 is desired to be easily peeled off the layer F1. Examples of such a material are polyethylene terephthalate, polypropylene, polyethylene, polyvinyl alcohol, and polyvinyl chloride. The thickness of the support member F3 is ordinarily 10 to 150 µm, preferably 20 to 50 µm. The material for the protective film F2 is desired to be easily peeled off the layer F1, and to have a good light transmission property in order to expose the colored photopolymerization resin layer F1 therethrough. The preferable examples of such a material are polyetylene and polypropylene. The preferable thickness thereof is ordinarily 10 to 50 µm. In the first embodiment, the thickness of the colored photopolymerization resin layer F1 composing the picture layer is ordinarily 5 to 50 µm, preferably 10 to 15 µm in consideration of the visibility, appearance, or color density. And the transparent support member F3 is desired to have good light transmission property in order to expose the colored photopolymerization resin layer F1 therethrough. The photopolymerization resin films FW, FR, FB of white, red and black, each having the above-described construction were prepared, and a display board is produced in the processes shown in Figs. 4 (1) to 4 (12). Firstly, in the process shown in Fig. 4 (1), the white polymerization resin film FW is pasted on the substrate 1(thickness: about 0.5 to 1.5 mm) and is made to pressure-adhere thereto by means o the laminater 5 while peeling a protective film W2 off the film FW. Next, in the process shown in Fig. 4 (2), the film FW is irradiated with active energy rays such as ultraviolet rays L to be exposed and set. The exposure is performed by means of an ultra high pressure mercury lamp, and the amount of exposure is preferably 200 to 500mJ/cm 2 for white. Then, the transparent support layer W3 is peeled(Process of Fig. 4(3)) thereby forming the white picture layer 31 (transmission intensity: 0.8 to 1.0) on the substrate 1. In the process shown in Fig. 4 (4), the red photopolymerization resin film FR is made to pressure-adhere to the white picture layer 31 while peeling a protective film R2. On this red polymerization resin film FR is placed a negative mask 81 corresponding to the region R of Fig. 2, and is contact-exposed(Process of Fig. 4(5)). Then, a transparent supporting layer R3 is peeled off the film FR(Process of Fig. 4(6)). The amount of exposure is preferably 200 to 500 mJ/cm 2 . In the process shown in Fig. 4 (7), the wet development by using alkali or solvent, or the dry development is performed to remove unexposed portions from the film FR. This results in only the portions which are reacted to light so as to firmly adhere and be set, remaining thereby forming the red picture layer 32 corresponding to the figures and scales of the region R on the white picture layer 31 with the transmission density of 0.4 to 0.7). Next, in order to form the figures, scales or the like of the region W, and display them sharply as well as to give them the function as the transmission type display board, black photopolymerization resin film FB is subjected to similar processes. In the process shown in Fig. 4(9), the black photopolymerization resin film FB is made to pressure-adhere to the red picture layer 32 while peeling a protective film B2. And in the process shown in Fig. 4 (10), a negative mask 82 is placed on the film FB, and contact-exposure is performed. The preferable amount of exposure is about 1000 mJ/cm 2 . Then, the transparent support layer B3 is peeled off the film FB(Process of Fig. 4(11)), and the development is performed(Process of Fig. 4 (12)) to form a black picture layer 33 having a transmission density of 4 or more. Thus, the display board having the construction shown in Figs. 1 and 2 is obtained. By forming a masking picture layer having a large transmission density, such as the black picture layer 33, the obtained picture is observed as the reflection type picture in the daytime. In the nighttime, by placing a light source on the rear side of the substrate, the figures and letters transmit light to shine with various colors while the black background portion does not transmit light so that this construction can be used as the transmisiion type picture and illumination. In this case, it is preferable to use the masking picture layer having a transmission density of 2.0 or more. And a masking picture layer 9 may be arranged in contact with another picture layer 10 as shown in Fig. 5 Instead, an edge of the masking picture layer 9 may be laminated on another picture layer 10 as shown in Fig. 6. This construction enables the formation of a jointless beautiful picture. When the photopolymerization resin is colored, the setting degree tends to be slightly lowered. But when the colored photopolymerization resin for the picture layer of the present invention has a setting degree of about 70% or more, the picture layer is not affected by remaining unreacted substances. The present inventors' examination shows that the setting degree of the colored photopolymerization resin, and the picture quantity have such relations to each other as shown in Fig. 7. The picture quality implies the color maintaining force, light resistance, adhesion property to the substrate, film hardness, heat resistance, and heat cycle resistance. At the setting degree of 70% or more, practically usuable picture quality can be obtained. Picture layers, each having different setting degrees, were prepared from the colored photopolymerization resins having a thickness of 10 to 15 µm and a transmission density of about 1.3 in the thickness of 15 µm by varying the amount of exposure. The relation between the setting degree and the film thickness is shown in Fig. 8. And the prepared picture layers having setting degrees of 50%, 70%, and 100%, respectively, were subjected to the durability test under the conditions shown in Table 1. The evaluation was performed as follows: Namely, when all of the checking items are satisfied, the mark ○ is inserted, and otherwise, the mark X is inserted in Table 1. As is apparent from Table 1, at the setting degree of about 70 % or more, such high picture quality as to be sufficienly durable to long use can be obtained. Moreover, by adjusting the film thickness, color intensity, or amount of exposure, 100% of setting degree can be obtained. When the substrate has light transmission property like that of the present embodiment, the setting degree can be further improved by exposing the previously formed picture layer from the rear surface of the substrate again. In this case, unreacted portions of the photopolymerizaton resin are reduced, and accordingly the setting degree is improved. Fig. 9 illustrates a second embodiment of the present invention. In this embodiment, an adhesive layer 11 made of transparent photopolymerizaton resin is provided between the substrate 1 and the undermost picture layer(in this embodiment, the white picture layer 31). The other construction of the second embodiment is similar to that of the first embodiment. The adhesive layer 11 is transparent and does not include any dye or pigment so as to exhibit high setting degree as compared with the colored one whereby high adhesion of the picture layer and the substrate can be obtained. By exposing the substrate of the construction of the second embodiment from the rear surface thereof again, the adhesion of the picture layer and the substrate can be much improved. Accordingly, a display board which is excellent in the working resistance in drilling and assembling in a display panel, is obtained. The thickness of the adhesive layer 11 is ordinarly about 0.1 to 100 µm, and preferably about 5 to 10 µm. Fig. 10 shows the result of the scratch test of the sample of the second embodiment by means of pencils of various hardness. In addition, the test results of the samples of the first embodiment, each being exposed in only the display surface thereof or in both display surface and rear surface thereof, are also shown for comparison. The test result shows that the samples of the first embodiment exhibit hardness(adhesion) good enough to be practically used, and by also exposing the rear surface and providing the adhesive layer in the second embodiment, the hardness(adhesion) is drastically improved. Fig 11 illustrates a third embodiment of the present invention. In the present embodiment, in order to adjust the amount of transmitting light, another picture layer shown in Fig. 12 is further laminated on a rear surface of the dial board of the tachometer for a vehicle shown in Figs. 1 and 2. This construction prevents the lightness of the displayed picture from lacking uniformity due to the light source disposed on the rear side of the display board. In Fig. 12, the picture adapted for adjusting the amount of transmitting light is formed by successively forming a white picture layer 31' and a black picture layer 33′, each having a predetermined pattern, on an under surface of a substrate 1′ made of transparent resin so as to have a picture pattern as shown in Fig. 13, for example. In the drawing, the region B corresponds to the black picture layer while the region W corresponds to the white picture layer. The light source is disposed at a nearly central portion of the region B. The masking property is gradually decreased as the distance from the light source is increased. The picture layer is not formed in the region C which is comparatively remote from the light source. In the region C, the transparent substrate is exposed to the outside. This picture pattern is voluntarily changed in consideration of the lightness, and position of the light source. The display board having the above described construction is produced as follows: Picture layers 31, 32, and 33 are previously formed on the substrate 1 while picture layers 31', 33' are previously formed on the substrate 1′, and then, the substrates 1, 1′ on which the picture layers are formed, respectively, are exposed again from the respective rear surfaces thereof to improve the hardness thereof. By further providing the adhesive layer shown in the second embodiment, the adhesion can be much improved. Thereafter, the substrates 1, 1′ are pasted or secured to each other by means of bolts or the like so as to come into close contact with each other. As described above, in accordance with the present invention, the display board may be composed by laminating a plurality of substrates on each of which desired picture layers are formed. In this case, the displayed picture can be made different between the reflection type display board and the transmission type display board. For example, by disposing a decorative picture as the background between the letter picture and the light amount adjusting picture, in the daytime, only the uppermost letter picture is perceived while at the time the light source is lighted up, the decorative picture is added to the letter picture to increase the decorativeness of the display board. Moreover, in accordance with the present invention, the frosted picture can be obtained by roughing the surface of the picture layer to reduce the glossiness thereof. This frosted picture prevents the surface of the reflection type picture from shining, and give the picture quiet tone of color. The frosted picture can be realized by previously roughing the surface of the colored photopolymerization resin film, which is to come in contact with the colored photopolymerization resin layer of the transparent support member, or roughing the surface of the formed picture layer by hot pressing. For instance, by varying the roughness of the transparent supporting member made of polyethylene terephthalate(PET), the glossiness of the surface of the picture layer can be reduced from 87% to 11%(roughness of the transparent support member:0.5 µm) or 2% (roughness of the transparent support member:2 to 3 µm). In the preceding first to third embodiments, the picture is composed of three colors, white, red and black. In accordance with the present invention, the colors for composing the picture are not limited to these three colors. A plurality of films, each having a desired color can be voluntarily combined with each other. When the display board is not of transmission type, it is unnecessary to compose the substrate of transparent resin. Colored resin will do.

Claims: A display board comprising: a receiver base (1,31); a first coloured photopolymerised resin layer (32) including a first colouring agent of a first colour, which is directly laminated on a surface of said receiver base to form a first picture pattern in said first colour; and a second coloured photopolymerised resin layer (33) including a second colouring agent of a second colour, said second coloured photopolymerised resin layer (33) being directly laminated both on at least a portion of said surface of said receiver base (1,31) on which said first picture pattern is not formed, and on at least a portion of a surface of said first coloured photopolymerised resin layer (32), to form a second picture pattern on said at least a portion of said surface of said receiver base (1, 31) and on said at least a portion of said surface of said first coloured photopolymerised resin layer (32), whereby a two-dimensional non-flat display including said first and second picture patterns is formed with said second picture pattern being on at least two levels thereof with respect to the receiver base. The display board according to claim 1, wherein said receiver base (1,31) includes a first part (1) composed of a transparent resin, and a third coloured photopolymerised resin layer on said transparent resin, and said first coloured photopolymerised resin layer (32) has an adhesion region which adheres to said third coloured photopolymerised resin film (31). The display board according to claim I or claim 2, wherein each of said first coloured photopolymerised resin layer (32) and said second coloured photopolymerised resin layer (33) has a thickness of between 5 and 50 µm. The display board according to claim 1, 2 or 3, wherein each of said first coloured photopolymerised resin layer (32) and said second coloured photopolymerised resin layer (33) includes a support member (B3,R3) to which it is attached prior to being laminated on said surface of said receiver base (1,31), thereby to increase the strength of each of said first coloured photopolymerised resin layer (32) and said second coloured photopolymerised resin layer (33). The display board according to any preceding claim, wherein said receiver base (1,31) includes a third coloured photopolymerised resin layer (31) which is totally exposed and photopolymerised, and coloured with a third colour different from said first colour and said second colour, and said first coloured photopolymerised resin layer (32) is directly adhered to said third coloured photopolymerised resin layer (31). The combination of display board according to any preceding claim and a light source for illuminating light to said receiver base (1,31) from a side where said first coloured photopolymerised resin layer (32) is not provided. A method of forming a display board comprising the steps of: 1) directly affixing a first coloured photopolymerisable resin layer (32) of a first colour on a surface of a receiver base (1,31); 2) exposing said first coloured resin layer (32) through a negative (81) having a first picture pattern, to provide exposed portions and unexposed portions in said first coloured resin layer (32); 3) removing said unexposed portions by wet development to directly form said first picture pattern of said first colour, which includes said first coloured resin layer (32); 4) directly affixing a second coloured photopolymerisable resin layer (33) of a second colour different than said first colour, both on at least a portion of said surface of said receiver base (1,31) on which said first picture pattern is not formed and on at least a portion of said first coloured resin layer (32), and exposing said second resin layer through a negative (82) of a second picture pattern to form exposed portions and unexposed portions of said second resin layer; and 5) removing said unexposed portions in said second coloured resin layer (33) by wet development to directly form said second picture pattern of said second colour, which is composed of said second coloured resin layer (33), on both said at least a portion of said receiver base (1,31) and said at least a portion of said first coloured resin layer (32) to form a two-dimensional non-flat display including said first and second picture patterns, with said second picture pattern on at least two levels thereof with respect to the receiver base. The method according to claim 7, wherein each of said first coloured resin layer (32) and said second coloured resin layer (33) has a thickness of 5 to 50 µm. The method according to claim 7 or claim 8, wherein each of said first coloured resin layer (32) and said second coloured resin layer (33) is supported by a support member (B3,R3) prior to being directly affixed on said surface of said receiver base for increasing the strength of each of said first coloured resin layer (32) and said second coloured resin layer (33). The method according to claim 7, 8 or 9, wherein a surface of said support member (B3,R3), which is to come into contact with each of said first coloured resin layer (32) and said second coloured resin layer (33) has good light transmission properties in order to expose the coloured photopolymerised layer therethrough.

Inventors: IMAI TAKESHI, IWASE TERUHIKO, KOURA TOSHIO, IMAI, TAKESHI, IWASE,TERUHIKO, KOURA, TOSHIO
Applicants: NIPPON DENSO CO, NIPPONDENSO CO., LTD.
Application year: 1989
Main classification: G03F7
IPC codes: G03F7, G01P1