WO2008082127A1

WO2008082127A1 - Printing type lighting guide sheet for light source

Info

Publication number: WO2008082127A1
Application number: PCT/KR2007/006793
Authority: WO
Inventors: Jong-Chul An
Original assignee: Digilog Display Co., Ltd.
Priority date: 2007-01-03
Filing date: 2007-12-24
Publication date: 2008-07-10

Abstract

There is provided with a printing type lighting guide sheet for light source in keypad structure comprising: PCB (1); LEDs (2) provided on the PCB (1) and used as light source; metal domes (3) for generating electric signals when its contact points are in contact with corresponding switch unit of the PCB (1); metal dome sheet (5) located over the metal domes (3); lighting guide sheet (8) over the metal dome sheet (5) for diffusing lights emitted from the LEDs (2); and keytop part (7) over the lighting guide sheet (8) for indicating letters or numbers, wherein the LEDs (2) are connected to one side surface of the lighting guide sheet (8), wherein the lighting guide sheet (8) comprises: transparent sheet (4); and diffusion layer (6) formed by screen printing paste with diffusion or reflection features on one surface of the transparent sheet (4) in order to diffuse the lights from the LEDs (2) toward the keytop part (7).

Description

PRINTING TYPE LIGHTING GUIDE SHEET FOR LIGHT

SOURCE

Technical Field

[1] The present invention relates to a printing type lighting guide sheet for light source.

More particularly, the present invention relates to a printing type lighting guide sheet for light source, wherein LEDs are connected to a side surface thereof and wherein the printing type lighting guide sheet has, on one surface thereof, a diffusion layer formed by screen printing paste for diffusing lights from the LEDs to whole parts of a keytop part so as to well identify letters and numbers on the keytop part. Background Art

[2] LED and EL sheet have been used as light emitting materials that provide lights to keypads of mobile phones.

[3] Among them, constructing a keypad light emitting unit with LED has drawbacks in that lights are not equally provided in spite of usage of a large number of LEDs and high brightness of LED itself because LEDs have to be mounted on PCB and mounted LEDs are located on either two outskirts of the PCB instead of being located right below metal domes thus to cause indirect illumination.

[4] Further, thickness of LED itself makes it difficult to reduce volume of a mobile phone and it requires extra processes of mounting the LEDs on PCB (SMD, SMT) so that it has another drawback of causing losses in time and cost.

[5] Also, constructing a keypad light emitting unit with EL sheets is to attach those sheets directly on the metal domes and has an advantage in that lights are equally provided by directly illuminating letters and numbers on the keypad. However, it requires an inverter for generating electric signals to activate lights and, thus, manufacturing cost for a mobile phone is likely to rise due to the inverter. In this regard, it has a disadvantage in that it is difficult to apply the keypad light emitting unit with EL sheets to a low price mobile phone. Further, it is not appropriate for broad usage because EL sheet has lower brightness and shorter lifetime than LED

[6] On the other hand, there is another type of a lighting guide sheet manufactured by injection molding. However, it has drawbacks in that it requires high costs in the beginning stage and it is not possible to carry out mass production. Further, it has another drawback in that the injection molding type lighting guide sheet can be embodied in only one color. Disclosure of Invention Technical Problem [7] The present invention is to solve the above-mentioned problems. The purpose of the present invention is to provide a printing type lighting guide sheet which makes it possible to cut down on manufacturing cost by simplifying working processes, which enables a slim-sized mobile phone by having a smaller volume than conventional light sources for keypads, which makes it possible to provide lights with even brightness to whole parts of the keypads and which makes letters and numbers on keytop part to be embodied in various colors. Technical Solution

[8] In order to solve the above-mentioned problems, the present invention provides a lighting guide sheet for light source in keypad structure comprising: PCB 1; LEDs 2 provided on the PCB 1 and used as light source; metal domes 3 for generating electric signals when its contact points are in contact with corresponding switch unit of the PCB 1; metal dome sheet 5 located over the metal domes 3; lighting guide sheet 8 over the metal dome sheet 5 for diffusing lights emitted from the LEDs 2; and keytop part 7 over the lighting guide sheet 8 for indicating letters or numbers, wherein the LEDs 2 are connected to one side surface of the lighting guide sheet 8, wherein the lighting guide sheet 8 comprises: transparent sheet 4; and diffusion layer 6 formed by screen printing paste with diffusion or reflection features on one surface of the transparent sheet 4 in order to diffuse the lights from the LEDs 2 toward the keytop part 7.

[9] Preferably, patterns of the diffusion layer 6 may comprise at least one of a group consisting of dot patterns, line patterns and plane patterns.

[10] Preferably, the paste may be one of a group consisting of denatured polyurethane, denatured polyester and SiO

[11] Preferably, the transparent sheet may be made of one of a group consisting of PC,

PET, PU, PMMA.

[12] Preferably, the transparent sheet may have a transparency of more than 80%.

[13] Preferably, color additives may be added to the paste.

[14] Preferably, colors may be added to the transparent sheet itself.

[15] Further, there is provided with a printing type lighting guide sheet for light source delivering necessary lights for indicating letters and numbers of keytop part, wherein LEDs are connected to one side surface of the lighting guide sheet, wherein the lighting guide sheet comprises: transparent sheet; and diffusion layer formed by screen printing paste with diffusion or reflection features on one surface of the transparent sheet in order to diffuse the lights from the LEDs toward the keytop part, wherein patterns formed as the diffusion layer by being screen printed are at least one of a group consisting of dot patterns, line patterns and plane patterns.

[16] As another preferred embodiment of the present invention, there is provided with a printing type lighting guide sheet for light source comprising: transparent sheet having a transparency of more than 80% and made of flexible materials; and diffusion layer formed by screen printing paste with diffusion or reflection features on one surface of the transparent sheet, wherein the lighting guide sheet is connected to light source so that the lighting guide sheet diffuses lights emitted from the light source, and wherein the lights diffused by the lighting guide sheet are embodied in various colors.

[17] Preferably, there is provided with a printing type lighting guide sheet for light source wherein various color additives are added to the paste.

[18] Preferably, there is provided with a printing type lighting guide sheet for light source wherein colors are added to the transparent sheet itself.

[19] Preferably, the transparent sheet may be made of one of a group consisting of PC,

PET, PU, PMMA.

[20] Preferably, the paste may be one of a group consisting of denatured polyurethane, denatured polyester and SiO

Advantageous Effects

[21] A printing type lighting guide sheet for light source according to the present invention can be applied to various fields and it is appropriate for mass production because working processes are not complicated. Further, by adding color additives to paste or adding colors to transparent sheet of the lighting guide sheet, it is possible to embody various colors. Furthermore, it is possible to make appliances such as a mobile phone slimmer due to its smaller volume than conventional light sources. Brief Description of the Drawings

[22] Figure 1 shows a cross section of a keypad structure that employs a printing type lighting guide sheet 8 according to a preferred embodiment of the present invention.

[23] Figure 2 shows a process of diffusing and dispersing lights in the printing type lighting guide sheet shown in Figure 1.

[24] Figure 3 shows an arrangement of dots of diffusion layer 6 according to the present invention.

[25] Figure 4 shows a lighting guide sheet 18 with line patterns according to another preferred embodiment of the present invention. Best Mode for Carrying Out the Invention

[26] Hereinafter, preferred embodiments of the present invention will be explained in detail with reference to the attached drawings.

[27] Figure 1 shows a cross section of a keypad structure that employs a printing type lighting guide sheet 8 according to a preferred embodiment of the present invention.

[28] As shown in Figure 1, LEDs 2 to be used for light source are mounted on a PCB 1 and the LEDs are connected to one side of the lighting guide sheet 8. Metal domes 3 are also mounted on the PCB 1 and there is a metal dome sheet 5 over the metal domes 3. When contact point of the metal domes 3 is in contact with corresponding switch unit on the PCB 1, electric signals are generated. Due to the generation of the electric signals, the LEDs 2 are turned on, lights emitted from the LEDs 2 are dispersed through the lighting guide sheet 8.

[29] The lighting guide sheet 8 comprises: a transparent sheet 4 made of flexible materials such as PC, PET, PU, PMMA; and a diffusion layer 6 formed on one surface of the transparent sheet 4 by screen printing paste with diffusion or reflection features thereon. It is preferable that the transparent sheet 4 of the lighting guide sheet has a transparency of more than 80%. Further, it is preferable that the paste to be used for forming the diffusion layer 6 are made of materials such as denatured polyurethane, denatured polyester, SiO etc.

[30] Lights diffused through the lighting guide sheet 8 are diffused toward the keytop part 7 through the diffusion layer 6, thereby enabling users to identify letters or numbers on the keytop part 7. Figure 1 shows the diffusion layer 6 with dot patterns and it can be observed that the diffusion layer 6 is formed on a lower surface of the transparent sheet 4 (opposite side surface of the keytop part).

[31]

[32] Figure 2 shows a process of diffusing and dispersing lights in the printing type lighting guide sheet 8 shown in Figure 1.

[33] As shown in Figure 2, the lighting guide sheet 8 according to the present invention comprises: the transparent sheet 4 made of flexible materials such as PC, PET, PU, PMMA, etc. and connected to the LEDs 2 for light source; and the diffusion layer 6 formed with dot patterns on the lower surface of the transparent sheet 4.

[34] Because the paste used for forming the diffusion layer 6 are materials with diffusion and reflection features, lights emitted from the LEDs 2 are transmitted through the transparent sheet 4 of the lighting guide sheet 8 and then the lights are diffused by the diffusion layer 6 and delivered toward the keytop part 7. With this mechanism, the lighting guide sheet 8 according to the present invention serves as keypad backlight.

[35] Figure 2 shows the LED 2, the transparent sheet 4 and the diffusion layer 6 with a simple purpose of explaining a process of delivering lights emitted from LED 2. Further, it is not intended to limit relations among sizes of respective components and size and gap of dots of the diffusion layer 6. Therefore, it should not be understood that relations among sizes of the respective components and construction of the diffusion layer 6 are limited by the description of Figure 2.

[36]

[37] Figure 3 shows an exemplary arrangement of dots of diffusion layer 6 according to the present invention. [38] It is general that the dots of the diffusion layer 6 according to the present invention are printed convexly on the transparent sheet 4. As shown in Figure 3, it is possible to arrange dots of the diffusion layer 6 such that density of dots in regions close to the LEDs 2 is different from density of dots in regions not close to the LEDs 2. That is, considering the fact that brightness of the regions with high density of dots is higher than brightness of the regions with low density of dots, the diffusion layer 6 is arranged to have low density of dots in regions where lights from LEDs 2 can be reached well and high density of dots in regions where lights can not be reached well.

[39] On the other hand, if dots are evenly arranged, brightness in regions of dots with big size is high while brightness in regions of dots with small size is low. Thus, it is possible to arrange dots with small size in regions close to the LEDs 2 and dots with big size in regions not close to the LEDs 2.

[40] Accordingly, when constructing the lighting guide sheet 8 with dot patterns, not as shown in Figure 3, it is possible to design the diffusion layer 6 by employing dots of different sizes or fully considering both sizes of the dots and density of the dots. Further, it is more preferable for manufacturing a lighting guide sheet with desired brightness evenness if brightness of specific regions are measured and reflected to design of the diffusion layer 6. The design regarding dot patterns obtained through such a process can be performed by a dot pattern design program. Thus, it is possible to perform mass production of the lighting guide sheet with desired pattern arrangement by using such a dot pattern design program.

[41]

[42] Figure 4 shows a lighting guide sheet 18 with line patterns according to another preferred embodiment of the present invention.

[43] The lighting guide sheet 18 according to this embodiment has the same construction as the lighting guide sheet 8 according to the embodiment shown in Figures 1 to 3 in that a diffusion layer is formed on one surface of a transparent sheet by screen printing, while the lighting guide sheet 18 has different constructions that the diffusion layer comprises line type patterns instead of dot type patterns and line type patterns with various colors are embodied. Thus, explanations on the same constructions as the prior embodiment will be omitted.

[44] It has advantages in that it is possible to embody clear figures, and brightness and evenness of diffused lights are excellent when line type patterns are formed on the transparent sheet. This is because lights are evenly delivered upwardly.

[45] For forming a diffusion layer 16 of the lighting guide sheet 18 according to this embodiment of the present invention, it is possible to embody color lighting guide sheet by adding color additives to paste at the time of printing the line type patterns. Further, it is also possible to embody a lighting guide sheet with various colors by adding various color additives to the paste for printing.

[46] Construction of forming diffusion layer with various colors of the lighting guide sheet according to this embodiment of the present invention by adding color additives to paste at the time of printing has been explained through Figure 4. On the other hand, it is possible to embody desired colors by adding the desired colors to the transparent sheet itself.

[47] Although constructions of adding color additives to the paste and adding the desired colors to the transparent sheet itself are not explained herein in detail, there are no difficulties of embodying the lighting guide sheet according to the present invention based on ordinary knowledge regarding the above-mentioned constructions and the explanations regarding the other constructions in this specification. Thus, constructions of adding color additives to the paste and adding the desired colors to the transparent sheet itself will not be explained herein in detail.

[48] The lighting guide sheet with the diffusion layer comprising dots and the lighting guide sheet with the diffusion layer comprising line patterns were explained respectively with reference to Figures 1 to 3 and with reference to Figure 4. However, types of patterns printed as the diffusion layer of the lighting guide sheet according to the present invention are not limited to the dots or lines. That is, it should be noted that all lighting guide sheets with diffusion layer using dot patterns, line patterns, plane patterns or combination of the above-mentioned patterns are within the scope of the lighting guide sheet according to the present invention.

[49] Although it is explained with reference to Figures 1 and 2 that the diffusion layer is formed on the lower surface of the transparent sheet, it is clear that constructions of forming the diffusion layer comprising dot patterns, line patterns or etc. on the upper surface of the transparent sheet (a surface facing the keytop part 7) and forming such diffusion layers on both surfaces of the transparent sheet are also within the scope of the present invention.

[50] Comparing with the preferred embodiment of the present invention explained through Figures 1 and 2, the construction of forming the diffusion layer on the upper surface of the transparent sheet has a mere difference in terms of a surface where the diffusion layer is formed but there are no differences in other constructions and effects caused by the other constructions, so that detailed explanations are omitted.

[51] Merely several preferred embodiments of the present invention combining some of a construction of forming the diffusion layer by screen printing, a construction about various patterns of the diffusion layer, a construction on which surface of the transparent sheet the diffusion layer formed, and a construction of embodying patterns of the diffusion layer with colors were explained in detail. However, combining the above-mentioned constructions arbitrarily and embodying them also are within the scope of the present invention, although preferred embodiments regarding such combinations are not specifically described in this specification. Industrial Applicability

[52] The lighting guide sheet according to the present invention has advantages in that it is possible to embody desirable brightness despite thin thickness, it allows mass production because patterns can be printed according to pattern design programs and it is possible to embody various colors and thus to meet various requirements from customers.

[53] That is, the lighting guide sheet according to the present invention can be applied to all industrial fields, for example, for improving exterior design of various electronic devices as well as keypads of mobile phones.

[54] Accordingly, it is clear that applying important features of the lighting guide sheet according to the present invention into technical fields other than mobile phones is also within the scope of the present invention.

Claims

[1] A printing type lighting guide sheet for light source in keypad structure comprising:

PCB 1; LEDs 2 provided on the PCB 1 and used as light source; metal domes 3 for generating electric signals when its contact points are in contact with corresponding switch unit of the PCB 1 ; metal dome sheet 5 located over the metal domes 3; lighting guide sheet 8 over the metal dome sheet 5 for diffusing lights emitted from the LEDs 2; and keytop part 7 over the lighting guide sheet 8 for indicating letters or numbers, wherein the LEDs 2 are connected to one side surface of the lighting guide sheet 8, wherein the lighting guide sheet 8 comprises: transparent sheet 4; and diffusion layer 6 formed by screen printing paste with diffusion or reflection features on one surface of the transparent sheet 4 in order to diffuse the lights from the LEDs 2 toward the keytop part 7.

[2] The printing type lighting guide sheet according to claim 1, wherein patterns of the diffusion layer 6 comprise at least one of a group consisting of dot patterns, line patterns and plane patterns.

[3] The printing type lighting guide sheet according to claim 1, wherein the paste is one of a group consisting of denatured polyurethane, denatured polyester and SiO

[4] The printing type lighting guide sheet according to claim 1, wherein the transparent sheet is made of one of a group consisting of PC, PET, PU, PMMA.

[5] The printing type lighting guide sheet according to claim 1, wherein the transparent sheet has a transparency of more than 80%.

[6] The printing type lighting guide sheet according to claim 1, wherein color additives are added to the paste.

[7] The printing type lighting guide sheet according to claim 1, wherein colors are added to the transparent sheet itself.

[8] A printing type lighting guide sheet for light source delivering necessary lights for indicating letters and numbers of keytop part, wherein LEDs are connected to one side surface of the lighting guide sheet, wherein the lighting guide sheet comprises: transparent sheet; and diffusion layer formed by screen printing paste with diffusion or reflection features on one surface of the transparent sheet in order to diffuse the lights from the LEDs toward the keytop part, wherein patterns formed as the diffusion layer by being screen printed are at least one of a group consisting of dot patterns, line patterns and plane patterns. [9] A printing type lighting guide sheet for light source comprising: transparent sheet having a transparency of more than 80% and made of flexible materials; and diffusion layer formed by screen printing paste with diffusion or reflection features on one surface of the transparent sheet, wherein the lighting guide sheet is connected to light source so that the lighting guide sheet diffuses lights emitted from the light source, and wherein the lights diffused by the lighting guide sheet are embodied in various colors. [10] The printing type lighting guide sheet according to claim 9, wherein various color additives are added to the paste. [11] The printing type lighting guide sheet according to claim 9,

Wherein colors are added to the transparent sheet itself. [12] The printing type lighting guide sheet according to claim 9, wherein the transparent sheet is made of one of a group consisting of PC, PET,

PU, PMMA. [13] The printing type lighting guide sheet according to claim 9, wherein the paste is one of a group consisting of denatured polyurethane, denatured polyester and SiO