PH12012000074B1

PH12012000074B1 - Method of manufacturing cover glass for portable device

Info

Publication number: PH12012000074B1
Application number: PH12012000074A
Authority: PH
Inventors: Hashimoto Kazuaki
Original assignee: Hoya Corp
Priority date: 2011-04-04
Filing date: 2012-04-02
Publication date: 2015-01-21
Also published as: JP5345225B2; PH12012000074A1; JP2012226308A

Abstract

Object of the Invention: It is an object of the invention to provide a method of manufacturing a cover glass for a portable device whereby the width of an unprintable offset region can be reduced as much as possible in an outer peripheral portion of a main surface of a plate-shaped glass processed in a shape of a cover glass for a portable device. Means for Achieving the Object: In a printing process, once mounted on a fixture J1, a glass substrate G is kept mounted on the fixture J1 until all the multilayered print layers are formed. The fixture J1, including the glass substrate G kept mounted thereto, is mounted on a fixture J2 of a printing device for executing screen printing of a first layer. Under the condition, screen printing is executed for forming a print layer A1 (Step S30). After formation of the print layer A1, the fixture J1 is removed from the fixture J2 (Step S40) and is then dried (Step S50). Ink attached to the fixture J1 is dried through the drying of Step S50. The ink attached to the fixture J1 can be thereby easily eliminated using a tool such as a spatula.

Description

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METHOD OF MANUFACTURING COVER GLASS FOR PORTABLE >

DEVICE a Sh iS \ %

BACKGROUND OF THE INVENTION a \ 7 [

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Field of the Invention oo

The present invention relates to a method of manufacturing a cover glass for a portable device.

Background Art

Cover glasses for portable devices have been used for mainly protecting the display screens of portable devices such as mobile phones, PDAs (Personal Digital Assistants), digital still cameras and video cameras. Variously shaped cover glasses have been recently fabricated for meeting requirements of variously shaped housings and display screens of portable devices as well as requirements of reduction in thickness of and highly sophisticated functions of portable devices. In some cover glasses for portable devices, a logo of a mobile phone manufacturer and a design, for instance, to enhance an aesthetic feature are printed on one of the main surfaces of a glass substrate. For example, Patent Literature 1 describes a protective plate for a portable display device that a film, on which characters or patterns are printed, is attached to one of the main surfaces of a glass substrate chemically strengthened by means of ion exchanging. Further, Patent Literature 1 describes a protective plate for a portable display device that characters or patterns are directly printed on a glass substrate.

CITATION LIST

PATENT LITERATURE :

Patent Literature 1: Japan Laid-open Patent Application Publication No. 2003-140558

SUMMARY OF THE INVENTION Technical Problem

Incidentally, an off-set region, on which printing is not executed, has been required to be formed on the outer peripheral portion of a main surface of a glass substrate in a printing process of executing printing onto the glass substrate. This has been a constraint on, for instance, flexibility in appearance and/or design of portable devices having a touch panel function. The drawback will be hereinafter further explained with reference to FIG 6. FIG 6 illustrates a state that a well-known glass substrate of a cover glass for a portable device is mounted on a printing device. FIG. 6 illustrates a plan view (upper side) and a side view (lower side).

In the well-known process of executing printing onto a glass substrate, a glass substrate as a printing target is mounted on a fixture for alignment that is fixedly disposed on a printing device (e.g., a screen printing machine), and a print layer is formed on the glass substrate by means of, for instance, screen printing as illustrated in FIG 6. When multilayered print layers are herein formed, the glass substrate is removed from the fixture after a print layer as a first layer of the multi-layers (i.e., a bottom layer) is formed, and is then dried in a drying furnace. In the case of a thermosetting ink, the drying is executed by subjecting the glass substrate to an environment at a temperature of roughly 60 to 100 degrees Celsius, for instance. In the case of a ultraviolet curable ink, the drying is executed by irradiating the glass substrate with UV (ultraviolet light) having a specified cumulative energy.

Subsequently, the glass substrate is again mounted on a fixture for forming a print layer as a second layer of the multi-layers. Thus, the second print layer is formed and the ink is similarly dried. The multilayered print layers are formed by repeating the aforementioned oo Co processing.

It should be noted that, in executing printing onto a cover glass for a portable device in general, printing is required to be executed onto the outer peripheral portion of the cover glass for concealing a variety of members to be attached below the print face of the cover glass (ie. the inside of the portable device) in mounting the cover glass onto the portable device. The members herein includes a variety of electronic devices and wiring, light emitting elements such as LED (Light Emitting Diode) light sources, either a double-sided tape or a resin material for bonding the cover glass to a housing and etc. In other words, it is required to reliably achieve a sufficient concealing performance, and further, a light blocking performance. Therefore, a thermosetting type ink is generally used for printing of a cover glass rather than an ultraviolet curable ink having a light transmissive property.

In exemplary cover glasses for portable devices currently on sale, it is not uncommon that a cover glass includes at least a few print layers, and in some instances, even more than 10 print layers. In fabricating such a cover glass for a portable device having multilayered (n-layered) print layers, a series of works of mounting a glass substrate on a fixture and removing the glass substrate therefrom is required to be repeated n-times in the aforementioned well-known printing process. Such a series of works are quite complicated and bothersome. In addition, such a series of works are executed while glass substrates are handled one by one. Therefore, work efficiency thereof is quite bad.

Further, when an ink is attached to a fixture for alignment while printing is executed for a given glass substrate in the aforementioned well-known printing process, the ink attached to the fixture may either contaminate another glass substrate as the next printing target or :

compromise appearance quality. Yet further, it is required to produce a clamp allowance in the outer peripheral portion of the glass substrate. The clamp allowance is required for removing the glass substrate from the fixture in drying the glass substrate. Thus, the entire surface of the glass substrate cannot be a printing target in order to prevent the ink from attaching to the fixture and/or reliably produce the clamp allowance. Therefore, the outer peripheral portion of the glass substrate, positioned in the vicinity of the fixture when the glass substrate is mounted on the fixture, is required to be excluded from the printing target.

In FIG 6, a non-printed region on the main surface of the glass substrate is referred to as “OFF-SET REGION”. An offset, a width of the off-set region, is set based on, for instance, a wobble caused between the glass substrate and the fixture when the glass substrate is mounted on the fixture due to variation in dimension of the contour of the glass substrate.

In recent years, it has been demanded to reduce the offset as much as possible, and preferably to eliminate the offset in terms of enhancement in an aesthetic aspect of, increase in a size of, and touch-panel functionalization of, the display screen of a portable device to which a cover glass is attached.

This relates to an appearance-related drawback produced when the offset region is not concealed on the display screen of a portable device. Specifically, the offset region may glare due to its non-printed nature and may outstand than the other regions. In response, it is preferable to reduce the offset as much as possible for reliably enlarging the display screen (i.e, an unconcealed region) as large as possible without producing visual strangeness for a glass substrate having a predetermined size.

Further, in fabricating a portable device having a touch panel function by attaching touch panel electrodes (e.g., a transparent conductive film represented by an ITO (Indium Tin

Oxide) film) onto a main surface of a glass substrate, a large number of wires for the touch panel are required to be disposed on a narrow outer peripheral portion of the main surface of the glass substrate in order to reliably obtain an effective touch panel display screen enlarged as much as possible within the constraints of a predetermined housing size of the portable device. When the glass substrate has a non-printable offset region on the outer peripheral portion of the main surface thereof, a region for disposing touch panel wires is further reduced by the offset region and this makes wiring design difficult. Further, the touch panel wires are inwardly displaced by the offset region when an upper electrode is bonded to a lower electrode disposed on the glass substrate. Therefore, workability in bonding gets

WOrse.

Yet further, light emitting elements, including a backlight for a LCD screen and a LED light source disposed on an operating button, are normally attached to the vicinity of the outer peripheral portion of a substrate. When the offset is produced on the substrate, the outer peripheral portion of the substrate more remarkably glares and this causes a problem of strangeness in appearance.

In view of the above, it is an object of an aspect of the present invention to provide a method of manufacturing a cover glass for a portable device whereby the width of an unprintable offset region can be reduced as much as possible in the outer peripheral portion of a main surface of a plate glass processed in a shape of a cover glass for a portable device. It is an object of another aspect of the present invention to improve the quality of a cover glass for a portable device by reducing frequency of attachment and detachment of a glass substrate

_ oo to and from an alignment fixture to be executed in forming a print layer, and further, improve work efficiency of forming multilayered print layers.

Solution to Problem

According to an aspect of the present invention, a method of manufacturing a cover glass for a portable device is provided, which is configured to execute printing a plurality of times with respect to an outer peripheral portion of a main surface of a glass substrate processed in a shape of the cover glass for a portable device. In the method of manufacturing a cover glass for a portable device, the glass substrate is fixed to a fixture and the printing and drying are executed with respect to the glass substrate kept fixed to the fixture without being removed therefrom.

According to an aspect of the present invention, a method of manufacturing a cover glass for a portable device is provided, which is configured to execute printing a plurality of times with respect to an outer peripheral portion of a main surface of a glass substrate processed in a shape of the cover glass for a portable device. The method of manufacturing a cover glass for a portable device includes a first printing step, a drying step and a second printing step. In the first printing step, a fixture including the glass substrate fixed thereto is mounted on a first printing device and then printing is executed with respect to the outer peripheral portion of the main surface of the glass substrate. In the drying step, the glass substrate kept fixed to the glass substrate is dried. In the second printing step, the fixture including the glass substrate kept fixed thereto is mounted either on the first printing device again or on another second printing device anew and then printing is executed with respect to the outer peripheral portion of the main surface of the glass substrate.

In any one of the aforementioned methods of manufacturing a cover glass for a portable device, the fixture is preferably configured to fix a plurality of glass substrates thereto.

Further, the first printing step and the second printing step are preferably respectively configured to execute printing and drying with respect to the plural glass substrates at the same time.

The aforementioned cover glass is configured to be used for a portable device equipped with an illuminance sensor. Further, the first printing step and the second printing step are respectively configured to form a paint region and a sensor hole for the illuminance sensor on the main surface of the glass substrate.

The aforementioned cover glass may be configured to be attached to a portable device while the outer peripheral portion of the main surface thereof is exposed.

Advantageous Effects of Invention

According to the present invention, it is possible to reduce the width of an unprintable offset region as much as possible in the outer peripheral portion of a main surface of a plate glass processed in a shape of a cover glass for a portable device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG 1A is a perspective view of the cover glass having an exemplary shape of the present exemplary embodiment.

FIG 1B is a cross-sectional view of the cover glass of the present exemplary embodiment.

FIG 2 is a flowchart representing a procedure of a printing process of the exemplary embodiment.

FIG. 3 is a diagram for explaining states of a substrate and a fixture in a side view in the printing process of the exemplary embodiment in association with FIG. 2.

FIG 4 is a diagram illustrating a case in which a plurality of glass substrates are mounted on a single fixture, and under the condition, the fixture is further mounted on a fixture for a printing device.

FIG. 5A is a diagram illustrating an exemplary shape of the fixture on which the cover glass of the exemplary embodiment is mounted.

FIG. 5B is a diagram illustrating an exemplary shape of the fixture on which the cover glass of the exemplary embodiment is mounted.

FIG. 6 is a diagram illustrating a state that a well-known glass substrate for a cover glass for a portable device is mounted on a printing device.

DETAILED DESCRIPTION OF EMBODIMENTS

(1) Cover Glass of Exemplary Embodiment

The structure of a cover glass according to an exemplary embodiment of the present invention will be hereinafter explained with reference to FIGS. 1A and 1B. FIG lA isa perspective view of the cover glass having an exemplary shape of the present exemplary embodiment, whereas FIG. 1B is a cross-sectional view of the cover glass of the present exemplary embodiment.

The cover glass of the present exemplary embodiment has a structure that a print layer is disposed on a glass substrate. For example, the cover glass of the present exemplary embodiment is preferably used as a cover glass for protecting the display screen of a portable electronic device, especially, a mobile phone (i.e., a portable device). Thus, the cover glass of the present exemplary embodiment is required to be a high-strength thin glass for satisfying a specification required for falling of a device or an operational input into the display screen (i.e., an operational input as a touch-panel function). Therefore, the cover glass of the present exemplary embodiment is chemically strengthened by means of ion exchange treatment.

A plate thickness T of a glass substrate 10 is not particularly limited. In general, however, the plate thickness T is preferably set to be less than or equal to 1 mm, and more preferably, less than or equal to 0.7 mm from the perspective of inhibiting increase in weight of and reducing the thickness of a variety of devices using the glass substrate 10. It should be noted that the lower limit of the plate thickness is preferably set to be greater than or equal to 0.2 mm from the perspective of reliably achieving mechanical strength for the glass substrate 10.

As the cover glass of the present exemplary embodiment, it is preferable to use heretofore known glass material such as: (1) aluminosilicate glass used for fabricating a plate glass using a down-draw method, containing SiO, ALO; and at least one selected from the group of alkali metal oxide including Li,O and NayO; and (2) soda-lime glass used for fabricating a plate glass using a float method or etc.

The glass substrate 10 includes a pair of compressive stress layers formed on the surface parts of the front and back faces thereof by means of chemical strengthening. The compressive stress layers are altered layers formed by substituting a part of alkali metal originally contained in the glass material forming the glass substrate with alkali metal having a larger ion radius. For example, sodium ions, contained in the glass material forming the glass substrate of the present exemplary embodiment, are substituted with potassium ions.

From the perspective of practical use (manufacturability, mechanical strength, chemical durability, etc.) as a plate glass, aluminosilicate glass more preferably contains: 62 to 75 % by weight of SiO, ; 5 to 15 % by weight of ALO;; 0 to 8 % by weight of LiO,; 4 to 16 % by weight of NayO; 0 to 6 % by weight of K;0; 0 to 12 % by weight of ZrO; and 0 to 6 % by weight of MgO.

With reference to FIG. 1B, multilayered print layers (two layers Al and A2 in the example of FIG 1B) are disposed on one of the main surfaces of the glass substrate 10 in the cover glass of the present exemplary embodiment. Printed contents of the multilayered print layers are not particularly limited. A typical example in forming multilayered print layers (an example that a negative print is made on a first layer) is as follows. The first layer is a print layer corresponding to the outer peripheral frame portion. A model name of a device, a logo of a company name, a variety of sensor holes and etc. are formed by partially eliminating the first layer. A second layer is a layer that the model name and the logo of the company name are printed with specified colors. A third layer is a backing print layer for shielding the print portions of the model name and the logo from light and for closing the pin holes formed through the frame print portion. A fourth layer is also a backing print layer.

A fifth layer is a filter ink for regulating transmittance, which is printed on a part corresponding to a brightness sensor hole. A sixth layer functions as an alignment guideline for either bonding the cover glass to a housing or attaching a wiring substrate for a touch panel to the cover glass.

(2) Method of Manufacturing Cover Glass of Exemplary Embodiment (2-1) Plate glass fabricating process

A plate glass fabricating process is a process of fabricating a plate glass from molten glass. For example, a down-draw method can be herein employed. The down-draw method is a method of continuously forming a glass ribbon by directing molten glass, poured from a wedge-shaped groove formed on the upper part of a glass plate forming device, to flow downwards along a sidewall of the glass plate forming device and fuse at the bottom end of the glass plate forming device. In the down-draw method, the molten glass, poured out of the glass plate forming device, fuses at the bottom end of the glass plate forming device and the resultant plate-shaped molten glass is subsequently extended in the vertical direction. The glass ribbon passes through a furnace while being supported by rollers disposed below the glass plate forming device. Meanwhile, the glass ribbon is annealed and is cut for obtaining a desired-sized plate glass. (2-2) Shaping process

Next, a shaping process is executed. The shaping process is a process of processing the plate glass obtained in the plate glass fabricating process into a desired-shaped glass substrate in accordance with the contour of a glass substrate for a portable device. A method using etching will be hereinafter explained as a method employed in the shaping process.

The shaping process using etching includes the following processes of: (a-1) an etching-proof film forming process; (a-2) a patterning process; and (a-3) a cutting process.

The method using etching will be hereinafter explained. In the shaping process, however, cutting, grinding, polishing and etc. may be alternatively executed using mechanical means. (a-1) Etching-proof film forming process

In the etching-proof film forming process, an etching-proof film is formed on at least either of the faces of the plate glass. Normally, the etching-proof films are formed on the both faces of the plate glass. However, the etching-proof film is required to be formed only either of the faces of the plate glass when only either of the faces of the plate glass is contacted to etching solution in the subsequent cutting process. It should be noted that the following explanation is given on the premise of forming the etching-proof films on the both faces of the plate glass. Any suitable etching-proof films can be arbitrarily selected as long as they have characteristics of partially removable by a patterning treatment in the subsequent patterning process and of being neither dissolved nor removed by etching solution to be used in the cutting process. As the etching-proof films, it is preferable to use resist films that are insoluble or hardly soluble at least against hydrofluoric acid. In this case, the resist films can be patterned by means of an exposure treatment using a photo mask and a development treatment using a developer in the patterning process, and can be cut using etching solution in the cutting process. (a-2) Patterning process

In the patterning process, at least the etching-proof films are patterned. Accordingly, the etching-proof films, covering the entire surface of the plate glass, are removed except for a region thereof corresponding to the planar directional shape of a finally fabricated glass substrate. Photolithography, executed by the combination of the aforementioned exposure and development treatments, can be typically used as a patterning method of the etching-proof films. It should be noted that the patterning process is only required to be executed for at least either of the faces of the plate glass that the etching-proof films are formed on the both faces thereof, and therefore, may be executed for both faces thereof. (a-3) Cutting process

In the cutting process, the plate glass is cut into pieces by means of etching, i.e., by causing the plate glass face, on which the patterned etching-proof film is disposed, to make contact with the etching solution. The etching treatment is normally executed by submerging the plate glass into the etching solution. The etching solution is not limited to a particular solution as long as it contains at least hydrofluoric acid. However, other acids such as hydrochloric acid and/or a variety of additive agents such as surfactant may be added to the etching solution on an as-needed basis. (2-3) Chemical strengthening process

Next, a chemical strengthening process is executed.

In the chemical strengthening process, a plurality of desired-shaped glass substrates obtained in the shaping process are mounted on a cassette (holder), and the cassette is submerged in chemical strengthening treatment liquid containing molten salt. Accordingly, at least one of alkali metals contained in the glass substrate is ion-exchanged with alkali metal of the molten salt. As a result, a compression stress layer is formed on a surface part of the glass substrate.

Composition, temperature and soaking time of the molten salt may be arbitrarily selected depending on glass composition of the glass substrate, the thickness of the compression stress layer formed on the surface part of the glass substrate and etc. However,

it is preferable to employ a low temperature ion exchange method that the processing temperature of the chemical strengthening treatment liquid is normally set to be less than or equal to 500 degrees Celsius when the glass composition of the glass substrate is aluminosilicate glass or soda-lime glass as described above. This is because it is difficult to obtain a glass substrate suitable for a cover glass for a portable device in a high temperature ion exchange method of executing ion exchange at a temperature zone greater than or equal to the annealing point of glass. Specifically, the glass substrate cannot obtain high intensity in the high temperature ion exchange method unlike in the low temperature ion exchanging method. Further, the high temperature ion exchange method has chances that the glass surface is eroded by the molten salt in the strengthening treatment and glass transparency is thereby deteriorated. In the chemical strengthening process of the present exemplary embodiment, for instance, it is preferable to select composition, temperature and soaking time of the molten salt from the following exemplary ranges. - Molten salt composition: either potassium nitrate or mixed salt of potassium nitrate and sodium nitrate - Temperature of molten salt: 320 to 470 degrees Celsius - Soaking time: 3 to 600 minutes (2-3) Printing process

Next, a printing process is executed for forming a print layer on either of the main surfaces of the chemically strengthened glass substrate. A variety of heretofore known printing methods (e.g., screen printing) can be used depending on materials forming print layers A1 and A2 and thicknesses of the print layers Al and A2. 1s

The printing process according to the present exemplary embodiment will be hereinafter explained with reference to FIGS. 2 and 3. FIG 2 is a flowchart representing the procedure of the printing process according to the present exemplary embodiment of the present invention. FIG. 3 is a diagram for explaining side-view states of the glass substrate and the fixture in the printing process according to the present exemplary embodiment in association with FIG. 2.

First, a chemically strengthened glass substrate G is prepared and fixed to a fixture J1 (Step S10). The fixture J1 may have an arbitrary shape as long as it can restrict horizontal movement of the glass substrate. For example, the fixture J1 may have a recess formed along the contour shape of the glass substrate G or alternatively, may have a plurality of protrusions aligned along the contour of the glass substrate G In the printing process according to the present exemplary embodiment, once mounted on the fixture J1, the glass substrate G is kept mounted on the fixture J1 until all the multilayered print layers are formed.

Next, the fixture J1 on which the glass substrate G is mounted is mounted on a fixture 12 of a printing device (a first printing device) configured to execute screen printing of a first layer, i.., the print layer Al in the present exemplary embodiment (Step S20). Screen printing is then executed under the condition for forming the print layer Al (Step S30). In forming the print layer Al, screen printing mat be executed for the entire region of the principal surface of the glass substrate G. In other words, an offset region not to be printed is not required to be set on the glass substrate G.

After the print layer Al is formed, the fixture J1, on which the glass substrate G is mounted, is removed from the fixture J2 (Step S40). Then, the fixture J1, on which the glass substrate G is mounted, is put and dried in a drying furnace at an in-furnace temperature of 60 to 150 degrees Celsius for 0.1 to 3 hours (Step S50). It should be noted that ink may be attached to the fixture J1 when printing is executed without setting the offset region in Step

S30. However, the ink attached to the fixture J1 is dried by executing drying in Step S50.

Therefore, the ink attached to the fixture J1 can be easily eliminated using a tool such as a spatula. Thus, the ink attached in Step S30 does not cause any troubles in the next step.

Next, the fixture J1 is taken out of the drying furnace. The fixture J1, on which the glass substrate G is mounted, is mounted on a fixture J3 of a printing device (a second printing device) configured to execute screen printing of a second layer, i.e., the print layer A2 in the present exemplary embodiment (Step S60). Then, screen printing is executed under the condition for forming the print layer A2 (Step S70). In forming the print layer A2, screen printing may be executed for the entire region of the main surface of the glass substrate G similarly to Step S30. After the print layer A2 is formed, the fixture J1, on which the glass substrate G is mounted, is removed from the fixture J3 (Step S80). ]

Similarly to Step S50, drying is then executed for the fixture J1 on which the glass substrate

G is mounted (Step S90). Even when ink is attached to the fixture J1 in Step S70, the ink attached to the fixture J1 is dried by executing drying in Step S90. Therefore, the ink attached to the fixture J1 can be easily eliminated using a tool such as a spatula similarly to the situation of the first layer.

Even in the case of three or more print layers, the printing process can be executed with a similar procedure.

According to the aforementioned printing process, printing and drying are executed for the glass substrate G as a printing target while the glass substrate G is mounted on the fixture

J1. Due to the configuration, even when ink is attached to the fixture J1, the ink attached thereto can be eliminated.

According to the aforementioned printing process, not only after drying of each layer but also after completion of printing and drying of all the layers, ink attached to the fixture can be eliminated after the glass substrate is removed from the fixture. Therefore, it is possible to prevent contamination of the next glass substrate G to be mounted anew and attachment of foreign substance thereto. It is thereby possible to set a printing range on the glass substrate G without taking into consideration of attachment of ink to the fixture J1.

Further, when multilayered print layers are formed in the printing process, the fixture J1 is removed from a printing device for a given layer and is mounted on the next print device while the glass substrate G is mounted on the fixture J1. In other words, the glass substrate

G is mounted on a new printing device without being directly touched by an operator or the like. Therefore, it is not required to take into consideration of setting the clamp allowance in the outer peripheral portion of the glass substrate G Therefore, a substantially offset-free printing can be executed in the aforementioned printing process.

The cover glass, fabricated by the method of manufacturing a cover glass for a portable device according to the present exemplary embodiment, is preferably attached to a portable device while the outer peripheral portion of the main surface thereof is exposed. In other words, regardless of attachment aspects of the cover glass, strangeness in appearance is not perceived due to the structure of the cover glass hardly including an offset region that can glare because of its unprinted nature. 1s the glass substrate G as a printing target while the glass substrate G is mounted on the fixture

According to the aforementioned printing process, not only after drying of each layer but also after completion of printing and drying of all the layers, ink attached to the fixture can be eliminated after the glass substrate is removed from the fixture. Therefore, it is possible to prevent contamination of the next glass substrate G to be mounted anew and attachment of foreign substance thereto. It is thereby possible to set a printing range on the glass substrate G without taking into consideration of attachment of ink to the fixture JI.

The cover glass, fabricated by the method of manufacturing a cover glass for a portable device according to the present exemplary embodiment, is preferably attached to a portable device while the outer peripheral portion of the main surface thereof is exposed. In other words, regardless of attachment aspects of the cover glass, strangeness in appearance is not perceived due to the structure of the cover glass hardly including an offset region that can glare because of its unprinted nature.

Further, the cover glass, fabricated by the method of manufacturing a cover glass for a portable device according to the present exemplary embodiment, is preferably a cover glass for a portable device equipped with an illuminance sensor. The illuminance sensor is a type of sensor configured to measure illuminance in a wide range from a shadowed region to a sunlight-exposed region. The illuminance data is configured to be used for adjusting brightness of the display screen of a portable device. Therefore, a sensor hole (optical window) is formed through the main surface of the cover glass for allowing for light transmission to the illuminance sensor. Further, the illuminance sensor is preferably positioned not to be shaded by the hand of a user when the user operates a touch panel.

Therefore, the illuminance sensor is positioned on the outer peripheral portion of the main surface of a portable device. Put the above together, setting the position of the illuminance sensor on the outer peripheral portion of the main surface of a portable device implies that a print layer (paint region) is required to be formed on the outer peripheral portion of the main surface of a cover glass in order to shield the wires and etc. related to the illuminance sensor of the portable device from the outside. The manufacturing method of the present exemplary embodiment for implementing offset-free printing is preferable as a method of manufacturing a cover glass for a portable device equipped with an illuminance sensor.

Further in the aforementioned printing process, it is not required to execute a work of removing the glass substrate G from a given fixture and then mounting it on another fixture anew in forming multilayered print layers. Therefore, it is possible to inhibit or prevent scratching of the glass substrate G attributed to the work of removal and reattachment, and simultaneously, to further reduce a takt time than the well-known methods.

In the well-known printing process, chances are that the main surfaces and/or the lateral sides of a glass substrate make contact with a fixture many times by repeating a work of mounting the glass substrate on the fixture and that of removing the glass substrate from the fixture. Accordingly, the glass substrate may be scratched. Especially for a product requiring multicolor multilayered printing (for e.g., at least two layers, and in some instances, ten layers), chances are increased that the glass substrate is scratched by a work of mounting the glass substrate on the fixture and that of removing the glass substrate from the fixture in proportion to increase in frequency of printing. By contrast, the method of manufacturing a cover glass for a portable device of the present exemplary embodiment can reduce frequency of works of mounting a glass substrate on a fixture and removing the glass substrate from the fixture. It is thereby possible to inhibit or prevent the glass substrate from being scratched in the printing process. Accordingly, it is possible to inhibit deterioration in mechanical strength due to scratches.

It should be noted that FIG. 3 exemplifies the case of mounting the single glass substrate G on the fixture J1 but the method of processing a glass substrate is not limited to the single-substrate processing method. Efficiency of the printing process may be implemented by mounting a plurality of glass substrates on a fixture. For example, FIG 4 exemplifies a case in which a plurality of glass substrates G1 to G4 are mounted on a single fixture J10 and the fixture J10, together with the glass substrates G1 to G4, is further mounted ona fixture J20 of a printing device. When multilayered printing is herein executed for the plural glass substrates G1 to G4, the glass substrates G1 to G4 are kept mounted on the fixture J10 until all the multilayered print layers are formed thereon. Further, printing and ;

drying for each layer are executed for the glass substrates G1 to G4 at the same time.

Materials of the aforementioned fixtures J1 and J10 may be arbitrarily selected from materials not compromising the aforementioned drying in a drying furnace and washing using an organic solvent, that is, materials having organic solvent resistance and heat resistance in accordance with an operating temperature of 60 to 150 degrees Celsius. For example, metal/metals selected from a group of stainless steel, aluminum and etc. is/are preferable as the materials of the fixtures J1 and J10.

Further, the fixture J1 illustrated in FIG. 3 is shaped for restricting movement of the glass substrate G to be mounted thereon and for not compromising printing. Each of FIGS. 5A and 5B illustrates an example of such shapes.

FIG 5A exemplifies a fixture J 1a for positioning the main surface (as a printing face) of the glass substrate G higher than the top face thereof by a height of gl in order to prevent ink from easily attaching thereto in printing. In this case, gl is preferably set to be less than the plate thickness of the glass substrate G for reliably fixing the glass substrate G to the fixture

Jla. On the other hand, FIG 5B exemplifies a fixture J1b for positioning the main surface (as a printing face) of the glass substrate G at the same height as the top face thereof. In this case, the fixture J1 is partially tapered in the vicinity of the lateral sides of the glass substrate

G for fixing the glass substrate G thereon, and simultaneously, for separating the top face thereof from the lateral sides of the glass substrate G at a clearance of g2 in order to prevent ink from easily attaching thereto in printing.

The exemplary embodiment of the present invention has been described above.

However, the method of manufacturing a cover glass for a portable device according to the

CL SE present invention is not limited to that of the aforementioned exemplary embodiment. It is apparent that a variety of changes and modifications can be herein made without departing from the scope of the present invention.

REFERENCE SIGNS LIST

10,GG1,G2,G3,G4 Glass substrate

AlLA2 Print layer

J1,J2,13,110,J20, J1a,J1b Fixture

Claims

1. A method of manufacturing a cover glass for a portabie device, the method . configured to execute printing a plurality of times with respect to an outer peripheral Yr, i portion of a main surface of a glass substrate processed in a shape of the cover glass for YY; on aportable device, “Y i wherein the glass substrate is fixed to a fixture and the printing and drying are 7 os oN executed a plurality of times repeatedly with respect to the glass substrate kept fixed to Gp > the fixture without being removed therefrom, and wherein, when the glass substrate is fixed to the fixture, the top face of the fixture is positioned lower than the main surface of the glass substrate as a printing face, and is positioned upper than the opposite face to the printing face of the glass substrate.

2. A method of manufacturing a cover glass for a portable device, the method configured to execute printing a plurality of times with respect to an outer peripheral portion of a main surface of a glass substrate processed in a shape of the cover glass for a portable device, wherein the glass substrate is fixed to a fixture and the printing and drying are executed a plurality of times repeatedly with respect to the glass substrate kept fixed to the fixture without being removed therefrom, and wherein the fixture has a tapered shape in the vicinity of the lateral sides of the glass substrate so that the top face of the fixture separates from the main surface of the glass substrate as a printing face and the fixture fixes the glass substrate at the opposite face to the printing face of the glass substrate.

3. A method of manufacturing a cover glass for portable device, the method configured to execute printing a plurality of times with respect to an outer peripheral portion of a main surface of a glass substrate processed in a shape of the cover glass for a portable device, the method comprising: a first printing step of mounting a fixture including the glass substrate fixed thereto on a first printing device and then executing printing with respect to the outer peripheral portion of the main surface of the glass substrate; a drying step of drying the glass substrate kept fixed to the glass substrate; and a second printing step of mounting the fixture including the glass substrate kept fixed thereto either on the first printing device again or on another second printing

. device anew and then executing printing with respect to the outer peripheral portion of the main surface of the glass substrate, wherein, when the glass substrate is fixed to the fixture, the top face of the fixture is positioned lower than the main surface of the glass substrate as a printing face, and is positioned upper than the opposite face to the printing face of the glass substrate.

4. A method of manufacturing a cover glass for a portable device, the method configured to execute printing a plurality of times with respect to an outer peripheral portion of a main surface of a glass substrate processed in a shape of the cover glass for a portable device, the method comprising: a first printing step of mounting a fixture including the glass substrate fixed thereto on a first printing device and then executing printing with respect to the outer peripheral portion of the main surface of the glass substrate; a drying step of drying the glass substrate kept fixed to the glass substrate; and a second printing step of mounting the fixture including the glass substrate kept fixed thereto either on the first printing device again or on another second printing device anew and then executing printing with respect to the outer peripheral portion of the main surface of the glass substrate, wherein the fixture has a tapered shape in the vicinity of the lateral sides of the glass substrate so that the top face of the fixture separates from the main surface of the glass substrate as a printing face and the fixture fixes the glass substrate at the opposite face to the printing face of the glass substrate.

5. The method of manufacturing a cover glass for a portable device recited in claim 3 or 4, wherein the fixture is configured to fix a plurality of glass substrates thereto, and the first printing step and the second printing step are respectively configured to execute the printing and the drying with respect to the plural glass substrates at the same time.