JP2006318766A - Key top member bearing cutout character that has no break and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make at least a key top part with a metal in order to respond to a request that reduction of thickness and an appearance of a metallic texture are emphasized in a cellular phone because a design property is emphasized, and to prevent a so-called discontinued character having a discontinued character line born on a key top from being generated. <P>SOLUTION: In a translucent key sheet 1A, by forming a resist layer 2b on the undersurface of a metal plate body 11 constituting each key top, for instance, 2a, and by carrying out etching completely penetrating a cutout character or numeric character from the upper surface to the lower surface of the metal plate body, the so-called discontinued character is prevented from being generated; and an island character part 2e of the cutout character or numeric character is prevented from being lost even if a bridge 2d is not used by keeping it by the function of the resist layer 2b. The prevention of omission of a part (an island part) 2e surrounded by holes of a character line may be enhanced by attaching a transparent film 16 for reinforcement instead of expecting the function of the resist layer 2b or in addition to it. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a translucent key sheet in which a plurality of keys, which are input means for handy mobile devices such as a mobile phone and a personal digital assistant (PDA), are arranged together. The present invention relates to a technique for minimizing the thickness by using and preventing the letters and numbers displayed on the metal key top member from being cut out.

  The key sheet is a component that constitutes a handy mobile device such as a mobile phone or a personal digital assistant (PDA), and each of the key top members is a plurality of key top members (hereinafter referred to as alphabetic and / or numeric keys, function keys, etc.). Are simply arranged and bonded on a sheet-like member called a keypad. The keypad is a flexible member having rubber elasticity such as silicone rubber or thermoplastic elastomer. The key sheet configured as described above has a printed circuit board having a plurality of normally open contacts closed by pressing a push button on the lower surface thereof to form a push button switch, and further a key top. A light source for illuminating from the back surface is arranged to constitute a key unit as one unit assembly (sub-assembly).

  Since the key sheet is formed in such a state that a plurality of components are layered in this manner, the thickness of each component is accumulated to a considerable thickness. Therefore, it is required to make the whole as thin as possible so as to further improve the portability of the handy mobile device.

  However, for example, the technique disclosed in Patent Document 1 is a technique in which letters and the like are formed on a metal plate by half-etching and used for a key top. Even if the top is half-etched (by forming a “groove” by removing the metal material in a predetermined shape from the surface of the object to the middle in the thickness direction by etching), there is no reason to obtain translucency. Therefore, this half etching method does not make the technical idea of the present invention realizable. Japanese Patent Application Laid-Open No. H10-228707 describes a technique of making the key top an illumination type by performing an etching process in which characters or the like are penetrated instead of half etching on a metal plate used as a key top. The shapes of characters and the like are island characters with bridges, and do not make the technical idea of the present invention realizable.

  Although the technique disclosed in Patent Document 2 does not require the use of island characters with fridges, it is not formed by etching a metal plate as a translucent key top itself, but is made of a bowl-shaped metal. Since the characters are solid-printed on a transparent or translucent resin key top fitted in the frame, only a detour technique contrary to the gist of the present invention is disclosed.

JP-A-8-7691 JP-A-9-82174

  Mobile phones tend to be thinned because of emphasis on design. Accordingly, the key sheet is required to be thinned to about 1.0 mm. However, as long as the conventional technique using a resin key top such as PC (polycarbonate resin) is followed, there is a limit to reducing the thickness of the key sheet due to problems such as strength. The limit was 1.5 to 1.6 mm.

  The present invention uses a metal plate for the key top and reduces the thickness of the metal plate to 0 in order to cope with a design trend that requires a thin key sheet and a metallic appearance. 1 mm or less, and a part of the drawn line of characters displayed on the key top is cut off and connected by a non-illuminated fridge portion 2d as shown in FIG. The so-called “cut character” (the above “island character with bridge 2d”) does not occur, and can be displayed as a complete character as shown in FIG. 2e is maintained) is a problem to be solved.

  However, in order to make a metal key top that essentially does not transmit light an illumination type, it is necessary to provide holes in the form of letters and numbers for transmitting light. In the etched etching method and mechanical processing methods such as punching / drilling (shearing), there are portions that are left behind by being surrounded by holes of character lines such as the numbers 0 and 8 and alphabets a and b. In some cases, there was a problem that this part was cut off and separated. For this reason, conventionally, as illustrated in FIG. 1B, the so-called “cut character”, which requires the fridge portion 2d to connect the portion surrounded by the hole of the character stroke line, has been used. The bridge portion 2d has a portion that does not transmit light across the character drawing line, and has a problem that it is incomplete as a character or a number and is difficult to visually recognize.

  In other words, if the key top material is a hard resin, translucent characters can be obtained simply by forming characters on the front or back surface of the key tops by printing or painting. However, in the case of a metal plate, the method of forming characters by printing or painting is not a solution. Considering the above points, the problem solution reaches the conclusion that the bridge portion 2d for connecting the portions surrounded by the holes of the character stroke lines may be eliminated.

  When a hole having a shape such as a letter or number for transmitting light is provided, a portion 2e that is left behind by being surrounded by a hole of a character drawing line such as the numbers 0 and 8 and the alphabet a and b is cut off. Even if the metal plate body is penetrated by etching from the upper surface to the lower surface so that it does not come apart, for example, if it is temporarily held by a sticky sheet or held on the lower surface, it will be scattered at the etching stage. I do not. That is, as illustrated in FIG. 1C, the fridge portion 2d for connecting the portions surrounded by the holes of the character stroke lines is not necessary, and so-called “cut characters” are eliminated.

  Although the limit of the thickness of the key unit according to the prior art was 1.5 mm to 1.6 mm, a metal material that was a hindrance to the promising candidate “adoption of a metal key top” to overcome this limit By solving the “cut character problem” inevitably caused by the specific non-translucency by the present invention, it has been possible to realize a thinning that has been expected by those skilled in the art but has been blocked by the above limit.

  The mobile phone is configured such that the screen display part and the key top part are arranged on the same plane and the whole is a rod type (straight type), and a hinge (hinge) between the screen display part and the key top part. The key sheet thinning of the subject of the present invention can be applied to any type, so that it can be folded as an example. An example of application to (see FIG. 1) will be shown.

  When a plastic such as a PC is used for the key top as in the prior art, the thickness of the key top is 0.5 to 0.6 mm in order to ensure the required rigidity. However, when a metal plate is used as a key top according to the present invention, the metal is stronger than the resin and does not crack, so the thickness is 0.2 to 0.3 mm (considering deformation of the metal due to external force). Otherwise, about 0.1 mm is also possible).

  The material of the metal plate to be used is not particularly limited, but it is preferable that the metal plate body has low malleability and ductility, is hard, and has spring elasticity. For example, stainless steel (SUS). Basically, a material that has the above-mentioned characteristics and is resistant to corrosion is suitable. However, a material that is vulnerable to corrosion can be used by forming a protective film such as an overcoat on the surface. Even if the material does not match the above characteristics, such as gold, silver, copper, etc., if there is an advantage in terms of the characteristics given to the design such as texture and color tone, it is not used alone but by plating, vapor deposition, sputtering, etc. What is necessary is just to form in thin film form on the surface, such as a SUS board.

  First, each step in the method of forming a “translucent character” that is not a cut character for the “metal plate” in the present invention will be described with reference to FIGS.

(A) As the metal plate 11 used for the key sheet 1A, a SUS plate having a thickness of 0.3 mm or less, for example, a thickness of 0.05 mm to 0.2 mm is prepared. Not limited to this, materials with low malleability and ductility, hard, spring elasticity, and corrosion resistance are suitable, but if a protective film such as an overcoat is formed on the surface etc., malleability / ductility, hardness, spring Even materials that do not satisfy the conditions in terms of elasticity and are vulnerable to corrosion can be used. Even if the material does not match the above characteristics, such as gold, silver, copper, etc., if there is an advantage in terms of the characteristics given to the design properties such as texture and color tone, the surface of the SUS plate etc. is applied by plating, vapor deposition, sputtering, etc. What is necessary is just to form in a thin film form.
(B) Photoresist (for example, composed of a novolac resin, a photosensitive agent and a solvent) 12 is coated on the upper and lower surfaces of the metal plate 11 prepared above, respectively, 12a and 12b. The photoresist 12 includes a positive type in which a pattern of a portion irradiated with light is removed by a subsequent development process, and a negative type in which a portion exposed to light remains. Any of them may be adopted. The following stage is an example when the positive type is used. The coating of the photoresist 12 may be any method such as screen printing and spraying, and is not particularly limited.
(C) A photomask 13 on which a display (mask pattern) of characters, symbols, figures, etc. indicating a desired key function is formed is overlaid on the metal plate 11 coated with the photoresist 12.
(C ′) The above stage (C) is an example in which a single-use photomask 13 is used as the photomask 13, but a non-contact type used repeatedly for the semiconductor manufacturing stage is also used. In this case, the mask pattern is projected and transferred by the optical system.
(D) UV (ultraviolet light: wavelength 436 nm or 365 nm) light 14 is applied from above the photomask 13 to transfer the mask pattern by degrading the photoresist of the irradiated portion 15.
(E) The photomask is removed and the photoresist 12 is developed. The development process is a process of, for example, dissolving and removing unnecessary portions of the photoresist 12 with a strong alkaline developer. After the processing, the portions irradiated with light (portions such as characters, symbols and figures) are removed, and only the surrounding portions remain.
(F) Next, the etching stage is entered. The metal plate body portion exposed by removing the photoresist 12 by development is removed to the lower surface with an etchant (metal etchant) (full etching). The photoresist 12b on the lower surface remains without being removed by the developer because the UV (ultraviolet) light 14 is not irradiated (that is, etching stops at the lower surface).
(G) Although the photoresist 12a on the upper surface is removed after the etching process, the photoresist 12b on the lower surface is not necessarily removed. A portion (island portion) surrounded by the hole of the character drawing line is held by the photoresist 12b on the lower surface so as not to drop off. Further, when the transparent film 6 having a thickness of, for example, 0.025 mm to 0.05 mm is pasted on the photoresist 12b on the back side of the metal plate 11 after the etching is finished, a portion surrounded by the hole of the character drawing line (Island part) can be more reliably prevented from falling off. In addition, it may replace with the transparent film 6 and may affix the thing similar to the EL light source sheet 17 mentioned later.
(G ′) Prior to the etching process, a transparent film 16 having a thickness of, for example, 0.025 mm to 0.05 mm is attached to the back side of the metal plate 11 for reinforcement, and is surrounded by a hole of a character line. You may keep the part (island part) from falling off. Usually, the transparent film 6 to be attached after the etching is made of PET (polyethylene terephthalate) resin or the like, but when attached before the etching process, it is made of PI (polyimide) resin that has high acid resistance and is not affected by the etching solution. The transparent film 6 may be used.

Although the following is omitted from the process diagram of FIG. 6, the following processes may be further added.
(H) As shown in FIGS. 2, 4, and 5, a coating layer 18 made of a transparent resin may be formed on the upper surface of the metal plate 11 constituting the key top for reinforcement or aesthetics. . The resin used for the coating layer 18 is, for example, a urethane acrylate UV curable resin. Since the coating layer 18 also fills the holes 19 for characters and the like, it is possible to prevent the fingertips from being damaged by the edge portions of the holes 19 for characters and the like during key operation.
When coloring a character or the like, the hole 19 of the character or the like is filled with a light-transmitting paint or the like, and then the coating layer 18 is formed. The coating layer 18 may be colorless or colored as long as it is transparent. The pseudo key top portion 18a can be formed by partially increasing the thickness of the coating layer 18. In this case, even if the thickness of the key top portion 18 a is added to the thickness of the metal plate 1, the thickness is about 0.2 to 0.3 mm.

  Holes having shapes such as letters and numbers can be formed by etching using laser light other than chemical etching. Also in this case, a film may be attached to the back side of the metal plate 11 prior to the racer etching. However, in this case, it is necessary to use a material having high heat resistance so that the film to be used can withstand laser etching.

  A configuration of a “thin key sheet” using the “key top member having a cut character that is not a cut character” formed by the method of the first embodiment will be described with reference to FIGS. 1 to 5.

  A key sheet 1A illustrated in FIG. 1 includes a numeric keypad portion 2a on which alphabets, symbols, and / or numbers are respectively displayed, a function key portion 2b to which functions such as power on / off, line disconnection, and mail are assigned. A plurality of keys, which are push buttons such as the cursor key 2c in the upper center portion, are gathered to be integrally formed on a single metal plate. The key sheets 1A, 2A, and 3A according to the present invention are configured as a module integrally with a printed circuit board having contacts and the like to be operated by the key sheets, and FIGS. It is illustrated in a complex shape.

  What is shown in the vertical left half of FIG. 2 is an enlarged partial sectional view showing the module including the key sheet 1A of FIG. 1 cut along the aa line. The illustrated key sheet 1A includes a metal plate 3 that constitutes a key top 2 formed integrally with a plurality of keys in which characters, symbols, figures, and the like indicating the function of the key are displayed as letters. A coating layer 18 that covers the upper surface of the metal plate 3 and fills the hole 19 of the drawn line of the character portion to be removed, a photoresist 12b attached to the lower surface of the metal plate, and a coating thereon A transparent film (for adhesion reinforcement) 6 and a contact suppression protrusion (presser) 3e are included. The transparent film 6 may be a reinforcing adhesive layer alone. Furthermore, a composite layer in which an EL light source sheet 17 for illuminating the key top display from the back surface may be used.

  What is illustrated in the vertical right half of FIG. 2 is a printed circuit board 5 having a plurality of normally open contacts that can close an electric circuit by selectively pressing the key top 2, a metal dome 4, , A protective film 7 for covering the metal dome 4 and the printed circuit board 5 and a filler for filling the space between the protective film 7 and the key top 2 portion and integrating them (foamed urethane resin, etc.) Are combined. When the EL light source seed 17 is not included on the transparent film 6 side, the EL light source sheet 17 may be disposed on the filler 8. A key module is configured as a whole by overlapping the key sheet 1A shown in the left half of FIG.

  On the right side of FIG. 1 of the key sheet 1A configured as described above, there is provided a metal dome 4 or the like for short-circuiting and electrically connecting a plurality of normally open contacts that are closed by pressing a push button as a switch element. The printed circuit board 5 is arranged in close contact, and an EL light source sheet 17 used as a light source for illuminating the key top from the back side is arranged on the back side of the key top 2, and is integrally modularized as an illuminated pushbutton switch. Yes.

  The drawn lines for displaying letters, symbols, figures and the like displayed on the top surface of the key top are etched so as to penetrate the metal plate from the top surface to the bottom surface in the thickness direction, but the back surface is at least a photoresist. By being fixed and held by 12b, the character stroke line is partially interrupted to form a so-called island character, and it has translucency that can display a complete cut-out character without becoming flared.

  The perspective view shown in FIG. 3 illustrates a key sheet 2A as an alternative to the key sheet 1A shown in FIG. As is apparent from the enlarged partial sectional view taken along the line bb in FIG. 4, the individual key tops of the coating layer 18 applied for reinforcement or aesthetics on the upper surface of the metal plate constituting the key top. This is an example in which the thickness corresponding to 2a is increased to make it square, for example, to have a shape like a flat tray. The resin used for the coating layer may be a urethane acrylate UV curable resin or the like. In the embodiment shown in FIG. 3, the configuration other than the provision of the coating layer 18 having an increased thickness is the same as the configuration shown in the cross-sectional view of FIG.

  FIG. 5 is an example in which each key top, for example, 2a, shaped like a face-down tray shown in the cross-sectional view of FIG. The embodiment shown in FIG. 5 has the same configuration as that shown in the cross-sectional view of FIG. 2 except that the shape of each key top portion is a gentle mountain shape.

  Since the coating layer 18 as shown in FIG. 2, FIG. 4, or FIG. 5 is not an essential component of the present invention, the clear coat is not adhered at all on the metal plate 1A on which the blank characters are formed. There can be examples. That is, as shown in FIG. 6G, after the etching process, the photoresist 12a on the upper surface is removed, leaving the photoresist 12b on the lower surface, and on the metal plate 1A to which the film 6 is attached. The clear coat does not necessarily have to be attached.

  Since the present invention relates to a thin key sheet used for mobile devices such as mobile phones and personal digital assistants (PDAs), it is equipped with translucent keys such as manufacturing of electronic devices and various parts thereof. In addition, the present invention has wide applicability in industrial fields that require thinning of these devices.

(A) is a perspective view showing an overall view of a foldable thin mobile phone provided with a thin key sheet using a key top member according to the present invention, and (B) is a translucent key top made of metal. Examples of island characters that cannot be avoided as letters such as 8 and 0 in the case of a plate, (C) is a book that can provide letters without forming island letters while using a metal plate. It is the figure which illustrated the translucent key top of invention. It is the aa line partial expanded sectional view of the thin key sheet | seat shown in FIG. It is a perspective view of the thin key sheet | seat using Example 3 of the key top member according to this invention. It is a bb line partial expanded sectional view of the thin key sheet shown in FIG. It is a partial expanded sectional view of Example 4 which shows the alternative structure with respect to the thin key sheet | seat shown in FIG. (A)-(D) is a figure which shows the manufacturing process of the keytop member according to this invention in a cross section in order of a step. (E)-(G) is a figure which shows the manufacturing process of the keytop member according to this invention in a cross section in order of a step.

Explanation of symbols

1, 1A, 2A, 3A Thin key sheet 2 Key top member 2a Numeric keypad 2b Function key 2c Cursor key 2d Fridge portion 2e Island character 3 Contact pressing protrusion (presser)
4 Metal Dome 5 Printed Circuit Board 5a Wiring Pattern 5b Through Hole 6 Transparent Film 7 Protective Film 8 Filling 11 Metal Plate 12 Photoresist 12a Upper Photoresist 12b Lower Photoresist 13 Photomask 14 UV (Ultraviolet)
15 Photoresist of irradiated portion 16 Transparent film 17 EL light source sheet 18 Coating layer 18a Pseudo key top portion 19 Character drawing line hole

Claims (9)

Forming a desired outer shape to constitute a key top member used for a thin key sheet, and preparing a metal plate having a thickness of 0.3 mm or less;
Coating a positive or negative resist film made of a photosensitive resin on an upper surface and a lower surface of the prepared metal plate by any means such as screen printing or spraying; and
A step of transferring a positive or negative mask pattern such as characters, symbols, and figures indicating the function of a key to a resist film on the upper surface side of the metal plate by exposure; and
A developing step for removing unnecessary portions other than the mask pattern of the resist film;
Forming a drawn line of a letter on the key top by etching the metal plate based on the mask pattern;
A step of forming a reinforcing layer that supports a portion (island portion) surrounded by the hole of the display drawn line by dropping a translucent film on the lower surface side of the metal plate after the etching treatment; ,
A method for manufacturing a key top member, comprising:   The step of applying a coating with a transparent resin is added to the upper surface of the metal plate body on which the extracted characters are formed in an optional step after the extracted characters are formed by the etching process. 2. A method for producing a key top member according to 1.   The method for producing a key top member according to claim 1, wherein the transparent resin to be coated is a urethane acrylate-based ultraviolet curable resin. A key top member including a metal plate formed by engraving and displaying a display pattern such as characters, symbols and figures indicating the function of the key, and having a desired outer shape,
A resist film made of a photosensitive resin is attached to at least the upper and lower surfaces of the metal plate, and the metal plate is exposed and etched from the upper surface so that the metal plate penetrates from the upper surface to the lower surface. Having a drawn character display drawn line,
Remaining in a state where a resist film is attached without being removed by the etching process on the lower surface of the metal plate,
Since the resist on the lower surface remains, the portion (island portion) surrounded by the drawn character display drawn lines is held in a state that does not fall off,
Thus, the key top member is characterized in that a cut character displayed on the metal key top while being a metal plate is given translucency without being cut out.   The key top member according to claim 4, wherein a reinforcing layer is formed by pasting a transparent film on the resist remaining on the lower surface of the metal plate.   6. The coating layer made of a transparent resin is provided on the upper surface of a metal plate on which a display pattern such as characters and symbol figures indicating the function of the key is engraved and displayed. Key top member.   The key top member according to any one of claims 4 to 6, wherein a thickness of the metal plate constituting a part of the thin key sheet is 0.3 mm or less.   The key top member according to claim 6, wherein the coating layer on the surface of the metal plate is made of a urethane acrylate UV curable resin.   The thickness of the coating layer on the surface of the metal plate is partially increased in accordance with each key region to form a pseudo key top portion. The key top member as described in.

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