Abstract:
There is provided a portable information processing terminal that places a reduced strain on a finger and is improved in operability. A housing of a cellular phone has a 15-key keypad. Of the buttons of 15-key keypad, the buttons disposed at the opposite ends of each row have a curved ridge. The manipulating surface of each button has inclined areas that extend upward from the ridge (toward a cursor key) and downward from the ridge (toward the bottom of housing).

Description:
[0001]    This nonprovisional application is based on Japanese Patent Application No. 2006-310454 filed with the Japan Patent Office on Nov. 16, 2006, the entire contents of which are hereby incorporated by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a portable information processing terminal. In particular, the invention relates to a structure of a manipulating part that accepts a manipulation for providing an input to the terminal. 
         [0004]    2. Description of the Background Art 
         [0005]    Cellular phones and other portable information processing terminals are provided with a set of buttons for inputting numerals or the like in the form of a keyboard, such as a ten-key keypad and a 12-key keypad. Such wireless communication terminals are designed to be operable with one hand in order to be portable. Specifically, a user of such wireless communication terminals can hold the terminal with one hand and input numerals and characters only with the thumb of the same hand. 
         [0006]    However, if the user performs an input operation only with the thumb, the input operation can be erroneous. Thus, for example, Japanese Patent Laying-Open No. 2001-312944 discloses a cellular phone having an integral multi-directional cursor key that is less likely to cause an erroneous manipulation. The cellular phone disclosed in Japanese Patent Laying-Open No. 2001-312944 has a key control device that has a single-piece button key (five-directional cursor key)  13  disposed on a central enter switch  3  and surrounding direction-indicating switches  4  to  7  and is capable of inputting directional commands for five directions including the central one direction and the surrounding four directions. The key control device has a central convex part  20  in the center area thereof corresponding to switch  3  and a convex annular part  21  in the peripheral area thereof corresponding to switches  4  to  7 . A recess  23 , which is substantially V-shaped in cross section, is formed at the border of the two areas to separate the center area and the peripheral area from each other. The protrusions and the depression on the top of the key control device enable the user to find the key for inputting their intended direction only based on the tactile sense of the finger. 
         [0007]    In addition, there has been proposed a cellular phone the manipulating buttons of which have a wavy manipulating surface (see “K-tai Watch, Wavy keys characteristic of W41 CA”, K-tai Watch website, K-tai Watch editorial office, 2006, http://k-tai.impress.co.jp/cda/parts/image_for_link/113381-27904-12-1.html). 
         [0008]    However, in the case of the cellular phone the manipulating buttons of which have a wavy manipulating surface, buttons closer to the user may be difficult to press because the buttons are close to the thumb, despite the wavy shape thereof. 
         [0009]    In addition, in general, if a user successively presses a button of a cellular phone or other wireless communication terminal to input a series of characters, a strain can be placed on the pressing finger (the thumb, for example), and the user can feel pain. 
       SUMMARY OF THE INVENTION 
       [0010]    The present invention has been made in order to solve the problems described above. An object of the present invention is to provide a wireless communication terminal improved in operability. 
         [0011]    In summary, in order to attain the object described above, an information processing terminal according to an aspect of the present invention includes a housing, and a plurality of manipulating parts arranged side by side in a first direction of the housing and configured to accept a pressing manipulation for providing an input to the information processing terminal. A manipulating part disposed at one end of the plurality of manipulating parts arranged in the first direction has a ridge, which is formed by a series of protrusions, on a manipulating surface for accepting the pressing manipulation. The ridge extends in a direction from the other end to said one end of the plurality of manipulating parts in such a manner that the ridge deviates from a virtual line extending in the first direction. 
         [0012]    Preferably, the ridge includes a curved part. Preferably, the ridge includes a straight part. Preferably, the information processing terminal further includes a display part configured to display an image. The ridge is curved toward the display part while extending in the direction form said the other end to said one end. 
         [0013]    Preferably, an area of the manipulating surface for accepting the pressing manipulation that extends from the ridge toward the display part is curved or flat in cross section. Preferably, an area of the manipulating surface for accepting the pressing manipulation that extends from the ridge toward the display part is tapered in cross section. 
         [0014]    Preferably, an end of the ridge located toward said one end is located on a side edge extending in a second direction perpendicular to the first direction of side edges of the manipulating surface for accepting the pressing manipulation. Preferably, an end of the ridge located toward said the other end is located on a side edge extending in the second direction of the side edges of the manipulating surface for accepting the pressing manipulation. Preferably, an end of the ridge located toward said the other end is located on a side edge extending in the first direction of the side edges of the manipulating surface for accepting the pressing manipulation. 
         [0015]    Preferably, a plurality of rows of the manipulating parts are arranged in a second direction perpendicular to the first direction. 
         [0016]    Preferably, the inclination of the manipulating surfaces of the plurality of manipulating parts arranged at said one end in the second direction varies among the manipulating parts. 
         [0017]    Preferably, another ridge, which is formed by a series of protrusions, is formed on a manipulating surface of a manipulating part disposed at said the other end of the plurality of manipulating parts. The other ridge extends in a direction from said one end to said the other end in such a manner that the other ridge deviates from the virtual line. 
         [0018]    Preferably, the other ridge includes a curved part. Preferably, the other ridge includes a straight part. 
         [0019]    Preferably, the information processing terminal further includes a display part configured to display an image. The other ridge extends toward the display part in the direction form said one end to said the other end. 
         [0020]    Preferably, an area of the manipulating surface for accepting the pressing manipulation that extends from the other ridge toward the display part is curved or flat in cross section. 
         [0021]    Preferably, an area of the manipulating surface for accepting the pressing manipulation that extends from the other ridge toward the display part is tapered in cross section. 
         [0022]    Preferably, an end of the other ridge located toward said the other end is located on a side edge extending in a second direction perpendicular to the first direction of side edges of the manipulating surface for accepting the pressing manipulation. 
         [0023]    Preferably, the other end of the other ridge located toward said one end is located on a side edge extending in the second direction of the side edges of the manipulating surface for accepting the pressing manipulation. 
         [0024]    Preferably, the other end of the other ridge located toward said one end is located on a side edge extending in the first direction of the side edges of the manipulating surface for accepting the pressing manipulation. 
         [0025]    Preferably, the ridge and the other ridge form a U-shape. 
         [0026]    Preferably, the plurality of manipulating parts include a plurality of buttons for accepting input of a number. 
         [0027]    Preferably, the plurality of manipulating parts include a plurality of buttons for accepting input of a character. 
         [0028]    Preferably, the information processing terminal further includes an editor configured to create a document based on a character input by manipulation of the plurality of buttons. 
         [0029]    Preferably, the information processing terminal further includes a sensing part configured to sense the pressing manipulation on any of the plurality of manipulating parts. The sensing part has a protrusion. The position of the protrusion corresponds to the position of the ridge formed on the manipulating surface. 
         [0030]    Since the portable information processing terminal according to the present invention has a manipulating surface on which ridges are formed, the contact area between the finger of a user of the terminal and the manipulating surface is increased. As a result, the strain placed on the finger pressing the manipulating surface is not concentrated at one part of the finger, and thus, finger fatigue is reduced. 
         [0031]    The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0032]      FIG. 1  illustrates a front view of a cellular phone  10  according to an embodiment of the present invention; 
           [0033]      FIG. 2  illustrates a perspective view of a housing  18  of cellular phone  10 ; 
           [0034]      FIG. 3A  illustrates a front view of housing  18 ; 
           [0035]      FIG. 3B  illustrates a cross-sectional view taken along the line A-B in  FIG. 3A ; 
           [0036]      FIG. 4  illustrates an enlarged view of a button  47  on which a numeral “4” is printed; 
           [0037]      FIG. 5  illustrates an enlarged cross-sectional view of housing  18 ; 
           [0038]      FIG. 6  is a diagram showing a manipulating surface of a housing of a cellular phone  500  according to a first modification of the embodiment; 
           [0039]      FIG. 7  is a diagram showing a manipulating surface of a housing of a cellular phone  600  according to a second modification of the embodiment; 
           [0040]      FIG. 8  is a diagram showing a manipulating surface of a housing of a cellular phone  700  according to a third modification of the embodiment; 
           [0041]      FIG. 9  illustrates a cross-sectional view of a 15-key keypad of a cellular phone according to a fourth modification of the embodiment; 
           [0042]      FIG. 10  illustrates a cross-sectional view of a 15-key keypad of a cellular phone according to a fifth modification of the embodiment; and 
           [0043]      FIG. 11  is a block diagram showing a hardware configuration of cellular phone  10 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0044]    In the following, with reference to the drawings, embodiments of the present invention will be described. In the following description, the same components are denoted by the same reference numerals and have the same names and the same functions. Therefore, detailed descriptions thereof will not be repeated. 
         [0045]    First, with reference to  FIG. 1 , a cellular phone  10  according to an embodiment of the present invention will be described. Although cellular phone  10  is a portable information processing terminal according to an aspect of the present invention, the information processing terminal according to the present invention is not limited to cellular phone  10 . For example, the information processing terminal may be a terminal device, such as a personal digital assistant (PDA). Alternatively, the information processing terminal may be a terminal device, such as a game controller that is held by the hands and manipulated independently by the left and right hands. 
         [0046]      FIG. 1  illustrates a front view of cellular phone  10 . Cellular phone  10  includes housings  12  and  18 , a display  14  disposed in housing  12 , and a hinge  16  that couples housings  12  and  18  to each other. Housing  18  has key buttons  20 ,  22 ,  28  and  30  configured to accept input of an instruction to perform a preset function, a cursor key  24  configured to accept input of an instruction to move a cursor on display  14  from side to side and up and down, an enter button  26  configured to accept input of an instruction to confirm an item on display  14 , and a 15-key keypad  32  consisting of  15  buttons arranged in a matrix. 
         [0047]    Of the three buttons in each row of 15-key keypad  32 , a button  34  closest to one side (the left side, for example) of cellular phone  10  has a ridge, which is formed by a series of protrusions. The ridge extends, from the other side (the right side, for example) of cellular phone  10  to the one side, to deviate from a virtual line parallel to the row (that is, the line of arrangement of the three buttons). 
         [0048]    Similarly, a button closest to the other side (the right side, for example) has a ridge, which is formed by a series of protrusions. The ridge also extends to deviate from the virtual line from the one side to the other side. 
         [0049]    A button  36  also has a ridge, which is formed by a series of protrusions. The ridge extends substantially straight. Thus, viewed from the front of cellular phone  10 , the ridges on buttons  34 ,  35  and  36  look like a U shape. 
         [0050]    Here, positions on cellular phone  10  according to this embodiment will be defined. A top part  13  of housing  12  is defined as the top of cellular phone  10 . Positions in the housings of cellular phone  10  are defined based on a longitudinal direction  100  and a lateral direction  110 . The side edges of cellular phone  10  extending in longitudinal direction  100  are defined as side edges  120  and  130 . 
         [0051]    Although cellular phone  10  is shown as a foldable cellular phone in  FIG. 1 , the positions are defined in the same way even if cellular phone  10  is not a foldable cellular phone. 
         [0052]    Supposing that lateral direction  110  is a first direction, longitudinal direction  100 , which is perpendicular to lateral direction  110 , is defined as a second direction. If the cellular phone has a horizontally long manipulating part in another aspect of the present invention, the longitudinal direction of the cellular phone is defined as the first direction, and the lateral direction is defined as the second direction. 
         [0053]    15-key keypad  32  contains three buttons in each row and five buttons in each column. 15-key keypad  32  includes so-called ten-key buttons to which numerals “0” to “9” are assigned and other buttons to each of which a symbol or character is assigned. 
         [0054]    If cellular phone  10  has a document creation function, each of the ten-key buttons accepts input of a character. The document creation function is, for example, a function of creating and editing an E-mail message or other documents. The button to which a numeral “1” is assigned to the “A column” (“A-gyou” in the Japanese language). Which character in the A column is to be chosen depends on the number of pressings of the button. For example, if the button is pressed once, a hiragana character “a” of “a, i, u, e, o” is shown. If the button is pressed twice, a hiragana character “i” is shown. Similarly, if the button is pressed five times, a hiragana character “o” is shown. If the button is pressed six or more times, the hiragana character “a” and the following hiragana characters of the “A column” are shown again. As for the other columns (the “KA column” (ka-gyou) and “SA column” (sa-gyou), for example), characters are input in the same way. 
         [0055]    Characters that can be input are not limited to hiragana characters, and katakana characters in the Japanese language can also be input in the same way. Furthermore, characters that can be input are not limited to Japanese characters. For example, alphabetic characters or other European or Asian characters or the like can be input. In those cases, a plurality of characters are associated with each button, and one of the plurality of characters is input depending on the number of pressings of the button. 
         [0056]    A full stop, a comma and other symbols can also be input in the same way. Specifically, a plurality of symbols to be input are assigned to a certain button. Each symbol is chosen depending on the number of pressings of the button. In such a configuration, if cellular phone  10  is in an operation mode of document creation, the user of cellular phone  10  can input a plurality of characters, symbols or the like only using one button by changing the number of pressings of the button. 
         [0057]    Those skilled in the art can easily understand the document creation function and other character input functions of cellular phone  10 . Therefore, further detailed description of those functions will not be described. 
         [0058]      FIG. 2  illustrates a perspective view of housing  18 . Each button of 15-key keypad  32  disposed on housing  18  has a ridged manipulating surface. The term “manipulating surface” refers to a surface on which a numeral or the like is printed and which accepts a pressing manipulation. 
         [0059]    In a row of buttons, the button disposed at the far left of the row has a ridge that extends from the right edge to the left edge of the button to deviate from a straight line extending perpendicularly from the right edge of the button. The ridges of the buttons arranged in a row constitute a U shape. The top of the ridges is chamfered. This chamfering reduces the load on the finger pressing the buttons. In addition, in the case where different buttons are pressed to input a plurality of characters or symbols, the chamfering allows the finger to move smoothly on the manipulating surface of 15-key keypad  32 . 
         [0060]    With reference to  FIGS. 3A and 3B , a structure of the buttons of cellular phone  10  will be further described.  FIG. 3A  illustrates a front view of housing  18 . 
         [0061]    With regard to a button  48 , which is one of the buttons of 15-key keypad  32  on housing  18 , the ridge on button  48  reaches to a left edge  42  of button  48 . The ridge is curved while extending from a right edge  41  of button  48  to left edge  42 . Specifically, the ridge is curved toward cursor key  24 . In other words, the ridge is curved to deviate from the line of arrangement of the buttons in this row including button  48 . 
         [0062]    In this embodiment, the terms “right” and “left” refer to “right” and “left” when cellular phone  10  is viewed from the front thereof. 
         [0063]    Since the ridge is curved in this way, it is ensured that, when the user is holding cellular phone  10  with the right hand, the finger moving from cursor key  24  to button  48  is stopped at button  48 . Therefore, the user is prevented from accidentally pressing another button (a button  49 , for example). 
         [0064]    A button  38  is disposed at the far right of the row including button  48 . Button  38  has, on the manipulating surface, a ridge that is curved while extending from the left edge to the right edge of button  38 . Specifically, the ridge is curved around cursor key  24  not to be excessively separated from cursor key  24 . In other words, the ridge is curved to deviate from the line of arrangement of the buttons in this row including button  48 . 
         [0065]    Since the ridge is curved in this way, it is ensured that, when the user is holding cellular phone  10  with the left hand, the finger moving from cursor key  24  to button  38  is stopped at button  38 . Therefore, the user is prevented from accidentally pressing another button (a button  39 , for example). 
         [0066]    Alternatively, when the user is manipulating cellular phone  10  with the thumb of the right hand, the thumb is stopped at the curved ridge of button  38 . Since the thumb does not move beyond button  38 , the user can quickly input characters. 
         [0067]    The shape of the ridge is not limited to that shown in  FIG. 3A . For example, instead of the curved shape of buttons  48  and  38  shown therein, the ridge may include a straight part. 
         [0068]    While the ridge extends to left edge  42  of button  48 , the end point of the ridge may not be on the left edge of button  48 . For example, the point may be a corner  40  of button  48 . Alternatively, the ridge may end at a point on an upper edge  43  close to left edge  42  of button  48 . The term “upper” used in this embodiment refers to the upper side when cellular phone  10  is viewed from the front thereof In other words, the term “upper” refers to the top of cellular phone  10  when cellular phone  10  is held in the vertical position. 
         [0069]    Other buttons of 15-key keypad  32  are configured similarly. Buttons disposed at the far right of 15-key keypad  32  are configured similarly except that the structure is inverted left-to-right. 
         [0070]    While the curved ridges of the buttons of the five rows of 15-key keypad  32  are identical in shape in the above description, the shape of the curved ridges may vary with the row. For example, the degree of curvature of the curved ridges of the buttons in the row including button  48  may be smaller than that of the curved ridges of the buttons in the row including a button  50  (that is, the row closest to the user on housing  18 ). When the user holds cellular phone  10 , the thumb of the right hand can barely reach and press button  48 , while the user has to bend the thumb to press button  50  or a button  46  located at the far left of the row. In this case, since the curved ridges of the buttons closest to the user are more sharply curved, the load on the thumb due to successive pressings of 15-key keypad  32  can be reduced. 
         [0071]    The shape of the curved ridge is determined by the size of each button of 15-key keypad  32 , for example. The phrase “size of button” refers to the vertical length and the horizontal length of the button if the button is rectangular. Alternatively, the phrase may refer to the area of the button viewed in the direction of pressing. 
         [0072]    The shape may be determined by taking into account the average thumb size of potential users of cellular phone  10 . Specifically, since the thumb size can be different among generations of users (between children and adult, for example), such a difference may be reflected in the shape of the curved ridge. In this case, if the intended user of cellular phone  10  is the youth, the degree of curvature can be higher than that of cellular phone  10  intended for adult. 
         [0073]    Of the three buttons of each row of 15-key keypad  32  (the buttons on which numerals “1” to “3” are printed, for example), the button at the far left (the button on which the numeral “1” is printed, for example) and the button at the far right (the button on which the numeral “3” is printed, for example) have curved ridges, as described above. 
         [0074]    However, the button between them (the button on which the numeral “2” is printed, for example) may have a curved ridge or a straight ridge. If the ridge is curved, the ridge can be the shape of an arc centered at a point on the longitudinal centerline of cellular phone  10 , for example. 
         [0075]    In this case, the ridge on each button may not be positioned to divide equally the manipulating surface of the button. For example, the distance from the ridge to the upper edge of the button (the edge closer to cursor key  24 ) is preferably longer than the distance from the ridge to the lower edge of the button. If this is the case, even when the user presses a button on cellular phone  10  with the side face of the thumb, the contact area between the region of the manipulating surface of the button above the ridge and the side face of the thumb increases, so that the button on cellular phone  10  can be pressed with reliability. 
         [0076]    According to another aspect, the ridges of the three buttons in a row may be parts of an arc centered at one virtual point. Alternatively, the left and right buttons may have a curved ridge similar in shape to corners of housing  18 . Here, the corners of housing  18  are the corners that are closer to the user holding cellular phone  10 . If this is the case, in addition to the improvement of the operability of the buttons and the reduction of the load on the finger of the user, cellular phone  10  can have a distinctive appearance because of the harmony between the shape of the manipulating surfaces of the buttons and the shape of the corners of housing  18 . 
         [0077]    Furthermore, the degree of curvature of the ridge of the buttons of each row of 15-key keypad  32  may be equal to that of the other rows or different from that of the other rows. For example, the degree of curvature of buttons  48 ,  49  and  46  may be equal or different. 
         [0078]    In the case where the degree of curvature of the ridge differs among the rows, for example, the degree of curvature (the so-called R-dimension) of the ridge on button  48 , which is disposed closer to cursor key  24 , can be greater than the degree of curvature of a ridge  44  of button  46 , which is disposed farthest from cursor key  24 . In this case, for example, it is ensured that a finger (the thumb) comes into contact with or is stopped at button  48 , so that button  48  can be pressed with reliability even with a weak pressing manipulation. Alternatively, the degrees of curvature may be in an inverse relationship. 
         [0079]    Furthermore, the degree of inclination of the inclined surface of the buttons, which depends on the degree of curvature described above, may vary. For example, the inclination of the upper area of button  48  above the ridge may be greater than the inclination of the upper area of button  46  above the ridge. In this case also, button  48 , which is disposed at the farthest position from the bottom end of housing  18  (the end close to the user), can be touched with a finger, so that the operability is improved. 
         [0080]      FIG. 3B  illustrates a cross-sectional view of housing  18  taken along the line A-B. The apex of each button of 15-key keypad  32  is recessed from a virtual line  300  that extends on the surface of housing  18  of cellular phone  10 . Therefore, in the case where cellular phone  10  is of foldable type or has a slide cover for protecting the manipulating surface of housing  18 , 15-key keypad  32  does not hinder covering of the manipulating surface of housing  18  with the other housing or the cover. 
         [0081]    In such a configuration, as described above with reference to  FIG. 3A , the buttons at the far left and the far right of each row of buttons has an end ridged to be smoothly contiguous to housing  18 . As a result, the buttons are more likely to come into contact with the finger (the thumb, in particular) of the user of cellular phone  10 , so that it is possible to prevent dust from being accumulated in gaps between the buttons of 15-key keypad  32  even if 15-key keypad  32  on housing  18  is recessed. 
         [0082]    With reference to  FIG. 4 , the manipulation surface of a button will be described.  FIG. 4  illustrates an enlarged view of a button  47  on which a numeral “4” is printed. Specifically, viewed from the front, a manipulating surface  480  of button  47  is rectangular. Manipulating surface  480  has side edges  410 ,  420 ,  430  and  440 . Side edges  410  and  420  extend in longitudinal direction  100  of cellular phone  10 . Side edges  430  and  440  extend in lateral direction  110  of cellular phone  10 . Manipulating surface  480  is a convex surface, and a series of protrusions on manipulating surface  480  form a ridge  470 . Ridge  470  extends between an end  450  and an end  460 . End  450  is located on side edge  410 . End  460  is located on side edge  420 . Ridge  470  extends from end  460  to end  450  while deviating from a virtual line extending in lateral direction  110 . 
         [0083]      FIG. 5  illustrates an enlarged view of the cross section of housing  18  shown in  FIG. 3B . Button  50  of 15-key keypad  32  has an apex  56  on the manipulating surface. A button  52  has a similar apex. Corners  54  and  58  of the manipulating surface of button  50  are chamfered and gently curved (or, in other words, form a large R). 
         [0084]    A pad  60  for receiving the force of pressing any of the buttons of 15-key keypad  32  is disposed on the back side of 15-key keypad  32 . Pad  60  is made of resin, for example. Pad  60  has protrusions  62  and  64 . Protrusion  62  transfers the pressing load exerted on button  50  to a contact sensing part  66 . Similarly, protrusion  64  transfers the pressing load exerted on button  52  to a contact sensing part  68 . 
         [0085]    Contact sensing parts  66  and  68  are piezoelectric elements, for example. The pressing force sensed by contact sensing part  66  or  68  is converted into an electrical signal, which is transferred to a control substrate  70  disposed in housing  18 . 
         [0086]    Control substrate  70  carries out a process determined by the pressing force. The process may be creation and edition of a document. If the operation mode of cellular phone  10  is an E-mail creation mode, a character is input according to the number of times of pressing a particular numeric button. In other words, the pressing force is converted into a signal that represents a character according to the number of times of pressings, and the signal is transmitted to control substrate  70 . A processor (not shown) that controls the operation of cellular phone  10  successively accepts input of characters represented by the signals transmitted to control substrate  70 . 
         [0087]    In such a configuration, apex  56  of button  50  is located at least on a virtual line connecting protrusion  62  and contact sensing part  66 . The same holds true for the other buttons. With such a configuration, although each button of 15-key keypad  32  has an inclined surface forming a ridge, pressing of the button can be sensed accurately, and the result of sensing can be transmitted to control substrate  70  with reliability. 
         [0088]    As described above, in cellular phone  10  according to this embodiment, 15-key keypad  32  has buttons having a ridge on the manipulating surface. The ridges on the buttons in the far left column and the far right column are curved. Thus, even if the user of cellular phone  10  successively presses buttons on cellular phone  10 , an erroneous operation, such as pressing a wrong button, can be avoided. 
         [0089]    Furthermore, the curved ridge more easily conforms to the tip (including the side) of the finger (the thumb, for example) of the user. As a result, even if the user presses buttons for a long time, the strain on the finger can be reduced. 
         [0090]    Furthermore, the user can sense the contact of the finger with the apex of the ridge on each button. Therefore, the user can input characters by touch typing without always seeing the manipulating surface of 15-key keypad  32 . Thus, the operability or user-friendliness of cellular phone  10  is improved. 
         [0091]    &lt;First Modification&gt; 
         [0092]    With reference to  FIG. 6 , a first modification of this embodiment will be described.  FIG. 6  is a diagram showing a manipulating surface of a housing of a cellular phone  500  according to the first modification. Cellular phone  500  has a 15-key keypad  510 , the configuration of the manipulating surface of which differs from that of 15-key keypad  32 . 
         [0093]    Specifically, a ridge  530  on a button  520  extends from a lower edge of button  520  to a left side edge of button  520 . The term “lower edge” refers to the lower edge of button  520 , which has a rectangular manipulating surface, viewed from the front thereof. 
         [0094]    With such a configuration, ridge  530  is shorter than the ridge of cellular phone  10  according to the first embodiment. However, since the protrusion is formed toward the left of button  520 , the finger is prevented from being off button  520 . Furthermore, of the regions of the manipulating surface of button  520  divided by ridge  530 , the region closer to a cursor key  24  is inclined toward ridge  530 , as in the first embodiment (see  FIG. 4 ). 
         [0095]    The button disposed at the far right of 15-key keypad  510  has the characteristics described above. 
         [0096]    Thus, according to the first modification, the contact area between button  520  of cellular phone  500  and the finger tends to be large. As a result, the tactile impression of the user of cellular phone  500  can be improved. 
         [0097]    &lt;Second Modification&gt; 
         [0098]    With reference to  FIG. 7 , a second modification of this embodiment will be described.  FIG. 7  is a diagram showing a manipulating surface of a housing of a cellular phone  600  according to the second modification. 
         [0099]    Cellular phone  600  has a 15-key keypad  610 . On 15-key keypad  610 , a button  620  disposed closer to the left side of a housing has a ridge  630 . The other buttons have a similar ridge. Ridge  630  includes a straight part extending in the direction of the row including the button and a curved part. In this case, a region of the manipulating surface of button  620  extending from ridge  630  toward a cursor key  24  is inclined. Ridge  630  forms an apex of button  620 . Button  620  having the ridge shaped in this way also easily conforms to the finger of the user of cellular phone  600 . 
         [0100]    &lt;Third Modification&gt; 
         [0101]    With reference to  FIG. 8 , a third modification of this embodiment will be described.  FIG. 8  is a diagram showing a manipulating surface of a housing of a cellular phone  700  according to the third modification. 
         [0102]    Cellular phone  700  has a 15-key keypad  710 . On 15-key keypad  710 , a button  720  disposed closer to the left side of a housing has a ridge  730 . The other buttons (the buttons on which numerals “1”, “4” and “7” and an asterisk mark “*” are printed) have a similar ridge. 
         [0103]    Ridge  730  includes two straight parts. An apex forming ridge  730  is chamfered. As can be apparently seen from  FIG. 8 , the ridges formed on the buttons of 15-key keypad  710  have the shape of an inverted trapezoid. 
         [0104]    On the other hand, the buttons disposed in the far right column of 15-key keypad  710  (the buttons on the manipulating surface of which “text”, “3”, “6”, “9” and “#” are printed) have a ridge formed symmetrically to ridge  730  with respect to a line extending in a longitudinal direction of cellular phone  700 . Each button has an inclined surface extending from the ridge. For example, the inclined surface extending from ridge  730  toward a cursor key  24  is a curved surface centered at a point on a virtual line passing through cursor key  24  of cellular phone  700 . Thus, the contact area between the finger of the user of cellular phone  700  and the inclined surface is larger than the contact area between the finger and an ordinary flat manipulating surface, and therefore, the strain on the finger is reduced. 
         [0105]    &lt;Fourth Modification&gt; 
         [0106]      FIG. 9  is a cross-sectional view of a 15-key keypad of a cellular phone according to a fourth modification of this embodiment. Buttons of the cellular phone according to this modification differ from the buttons of 15-key keypad  32  in that the manipulating surfaces are curved. 
         [0107]    Specifically, a manipulating surface  912  of a button  910  and a manipulating surface  922  of a button  920  are curved surfaces, and the cross sections thereof are curved lines. With such a configuration, when pressing a button, the tip of the finger more readily comes into contact with the button, and the button is pressed with higher reliability. 
         [0108]    &lt;Fifth Modification&gt; 
         [0109]      FIG. 10  illustrates a cross-sectional view of a 15-key keypad of a cellular phone according to a fifth modification of this embodiment. Buttons of the cellular phone according to this modification differ from the buttons of 15-key keypad  32  in that the inclination of the manipulating surfaces varies with the row. 
         [0110]    Specifically, the inclination of a manipulating surface  1012  of a button  1010  is greater than the inclination of a manipulating surface  1022  of a button  1020 . In this case, the user of the cellular phone can easily identify the positions of the buttons based on the difference in inclination, and therefore, an erroneous operation can be avoided. 
         [0111]    Furthermore, as illustrated in  FIG. 10 , in the case where the inclination of the manipulating surfaces of the buttons disposed far from the user (the buttons on which numerals “1”, “2” and “3” are printed shown in  FIG. 1 , for example) is smaller than the inclination of the manipulating surfaces of the buttons disposed close to the user (the buttons on which numerals “7”, “8” and “9” are printed, for example), the difference in degree of protrusion of the manipulating surfaces allows the user to easily manipulate the buttons far from the user or move the finger to the buttons far from the user. Thus, the operability of the buttons is improved. 
         [0112]    Now, with reference to  FIG. 11 , a specific configuration of cellular phone  10  according to an aspect of the present invention will be described.  FIG. 11  is a block diagram showing a hardware configuration of cellular phone  10 . Cellular phone  10  has an antenna  1108 , a communication device  1102 , manipulating buttons  1120 , a camera  1140 , a flash memory  1144 , a RAM  1146 , a data ROM  1148 , a memory card driving device  1180 , a CPU  11   10  that carries out an arithmetic processing, a sound signal processing circuit  1170 , a microphone  1172 , a speaker  1174 , a display  14 , a light emitting diode (LED)  1176 , a data communication interface (I/F)  1178 , and a vibrator  1184 . A memory card  1182  can be mounted in memory card driving device  1180 . 
         [0113]    A signal received at antenna  1108  is sent to CPU  1110  via communication device  1102 . CPU  1110  transfers the signal to sound signal processing circuit  1170 . Sound signal processing circuit  1170  performs a predetermined signal processing on the signal and outputs the processed signal to speaker  1174 . Speaker  1174  outputs a sound based on the signal. 
         [0114]    Microphone  1172  receives a voice into cellular phone  10  and outputs a signal according to the voice. Sound signal processing circuit  1170  performs a predetermined signal processing for conversation based on the signal and sends the processed signal to CPU  1110 . CPU  1110  converts the signal into a transmission signal and sends the transmission signal to communication device  1102 . Communication device  1102  transmits the signal from antenna  1108 , and then, the user of cellular phone  10  can enter into a conversation with a person at the other end of the line. 
         [0115]    Camera  1140  takes a picture of a subject in response to a manipulation of manipulating buttons  1120  and transmits the signal obtained by taking the picture to CPU  1110 . 
         [0116]    Flash memory  1144  stores data transmitted from CPU  1110 . CPU  1110  can read the data stored in flash memory  1144  and perform a predetermined processing using the data. 
         [0117]    RAM  1146  temporarily stores data generated by CPU  1110  based on a manipulation of manipulating buttons  1120 . Data ROM  1148  stores data or a program for making cellular phone  10  perform a predetermined operation. CPU  1110  reads the data or program from data ROM  1148  and makes cellular phone  10  perform a predetermined processing. The program includes an application that makes CPU  1110  function as an editor  1112 . 
         [0118]    Memory card driving device  1180  receives memory card  1182 . Memory card driving device  1180  reads data from memory card  1182  and transmits the data to CPU  1110 . In addition, memory card driving device  1180  writes data output from CPU  1110  to a storage area of memory card  1182 . 
         [0119]    Sound signal processing circuit  1170  performs a processing on the signal used for conversation as described above. CPU  1110  and sound signal processing circuit  1170  may be integrated with each other. 
         [0120]    Display  14  shows an image prescribed based on data output from CPU  1110 . For example, if CPU  1110  reads data about a telephone number from flash memory  1144 , display  14  shows the telephone number in a display area. 
         [0121]    LED  1176  emits light in a predetermined manner based on the signal from CPU  1110 . For example, if LED  1176  can emit light of a plurality of colors, LED  1176  emits light of a color associated with the data included in the signal output from CPU  1110 . 
         [0122]    Data communication I/F  1178  accepts connection of an external communication cable. Data communication I/F  1178  transmits the signal output from CPU  1110  to the outside through the cable. Alternatively, data communication I/F transmits a signal received through the cable to CPU  1110 . Vibrator  1184  vibrates at a predetermined frequency based on the signal output from CPU  1110 . 
         [0123]    According to an aspect, CPU  1110  functions as editor  1112  by executing a program stored in data ROM  1148 . More specifically, CPU  1110  accepts character input based on a signal from manipulating buttons  1120  and creates an E-mail message or other documents. Manipulating buttons  1120  include 15-key keypad  32 . As described above, since 15-key keypad  32  has ridges, the strain on the user during character input can be reduced. The basic operation of cellular phone  10  can be readily understood by those skilled in the art and therefore will not be repeatedly described. 
         [0124]    As described in detail above, the cellular phones according to this embodiment and modifications thereof have a 15-key keypad with ridges and inclined surfaces as a mechanism for accepting a pressing manipulation. With such a configuration, when the user presses the buttons of the 15-key keypad, the strain on the finger is reduced. In particular, when the user successively presses a plurality of buttons to input characters, finger fatigue is reduced. 
         [0125]    The buttons of the 15-key keypad of the cellular phone according to this embodiment is made of resin. However, the kind of the resin is not limited to the existing ones. For example, a curable resin may be used. In this case, the shape of each button of 15-key keypad  32  can be changed until a certain length of time elapses. Then, after a time specific to the resin elapses, the shape cannot be changed. If this is the case, the user&#39;s characteristics of the way of pressing the buttons of cellular phone  10  are reflected in the shape of the buttons, and therefore, the usability of cured buttons of cellular phone  10  for the user is improved. 
         [0126]    The present invention can be applied to a cellular phone or other portable information processing terminals. More specifically, the present invention can be applied to an information processing terminal that has a manipulation part that accepts a pressing manipulation. 
         [0127]    Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the scope of the present invention being interpreted by the terms of the appended claims.