JP2015207046A - position sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a position sensor capable of detecting an input position properly (as per an actual input) even when a surface thereof is covered with a protective sheet.SOLUTION: A position sensor includes: a sheet-like optical waveguide W comprising a grid of cores 2 sandwiched between a sheet-like undercladding layer 1 and overcladding layer 3; a light-emitting element 4 coupled to one end face of each linear core 2 constituting the grid of cores 2; and a light-receiving element 5 coupled to the other end faces of the linear cores 2. A protective sheet S made of resin or the like is placed on top of the overcladding layer 3, the protective sheet S having an arithmetic mean roughness Ra of 10 μm or greater on a surface in contact with the overcladding layer 3.

Description

  The present invention relates to a position sensor that optically detects a pressed position.

  Conventionally, a position sensor that optically detects a pressed position (input position) has been proposed (see, for example, Patent Document 1). In this, a plurality of cores serving as optical paths are arranged in the vertical and horizontal directions, and the peripheral portions of the cores are covered with a clad to form a sheet, and light from the light emitting element is incident on one end surface of each of the cores, The light transmitted through each core is detected by the light receiving element at the other end surface of each core. When a part of the surface of the sheet-like position sensor is pressed with a finger or the like, the core of the pressed portion (input position) is crushed (the cross-sectional area of the core in the pressing direction is reduced), and the core of the pressed portion is Since the light detection level at the light receiving element is lowered, the pressed position can be detected. When the pressing is released, the part returns to the original flat state to prepare for the next pressing.

JP-A-8-234895

  In order to improve the durability of the sheet-like position sensor of Patent Document 1, the present inventors mount a PET (polyethylene terephthalate) sheet material as a protective sheet on the surface of the position sensor. I put it. And the character etc. were input with the writing implements, such as a pen, from the surface of the protection sheet. However, it may not be detected as entered.

  Therefore, as a result of the investigation of the cause by the present inventors, when the input mark is not detected as input, the input mark (press mark by the tip of the writing instrument) does not return to the original flat state, but remains in a groove shape. I found out that it was in a state. At that time, it was also found that although the protective sheet was not adhered to the surface of the position sensor, the recessed portion locally adhered to the surface of the position sensor. That is, as shown in a cross-sectional view in FIG. 5A, the protective sheet S1 is recessed together with the position sensor W1 by pressing with the writing instrument 10 during the input, but the recessed portion of the protective sheet S1 is the position sensor W1. Further, since the protective sheet S1 itself has a certain degree of rigidity, the position sensor W1 can be used even when the pressure is released, as shown in a sectional view in FIG. This deformation is constrained, and the dents are not restored to the original flat state. The dent is in a state of pressing the surface of the position sensor W1. Therefore, even if the tip of the writing instrument 10 moves to another position, the dent of the movement trace (pressing trace) that does not need to be detected is always detected (noise). It is not detected on the street. In FIGS. 5A and 5B, reference numeral 51 denotes a cladding, and reference numeral 52 denotes a core.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a position sensor that can normally detect an input position (as input) even if a protective sheet is provided on the surface. .

In order to achieve the above object, a position sensor of the present invention has a plurality of linear cores formed in a lattice shape, an under cladding layer that supports the core, and an over cladding layer that covers the core. A core-shaped light waveguide comprising: a sheet-shaped optical waveguide; a light-emitting element connected to one end surface of the core; and a light-receiving element connected to the other end surface of the core; It is a sheet-like position sensor that identifies a pressed position by a change in propagation amount, and has a configuration in which a protective sheet (A) below is placed on the surface of the over clad layer.
(A) The protective sheet in which the arithmetic average roughness Ra of the contact surface with the over cladding layer is set to 10 μm or more.

  In order to be able to detect the input position normally (as input) in the sheet-like position sensor, even if the sheet-shaped position sensor has a protective sheet on the surface, first, the above-described conventional technique is used. The reason why the input part (pressing part) of the protective sheet sticks to the surface of the position sensor was investigated. As a result, the cause was that the surface roughness of the contact surface of the protective sheet in contact with the surface of the position sensor was small (arithmetic average roughness Ra was less than 10 μm). That is, it has been found that the contact area of the protective sheet with the position sensor is large and sticks due to the initial adhesiveness (tack) of the surface of the position sensor.

  Therefore, the present inventors, even if the surface of the over clad layer of the sheet-shaped optical waveguide constituting the position sensor of the present invention has initial adhesiveness (tack), the input portion (pressing portion) in the protective sheet In order not to stick to the surface of the over clad layer, research was conducted on the surface roughness of the contact surface of the protective sheet. As a result, when the arithmetic average roughness Ra of the contact surface of the protective sheet with the over clad layer is set to 10 μm or more, the input portion (pressed portion) of the protective sheet does not stick to the surface of the over clad layer. I found out. And, when pressing the protective sheet during input, the protective sheet is recessed with the sheet-shaped optical waveguide, and when the pressing is released, the protective sheet quickly returns to the original flat state together with the sheet-shaped optical waveguide. Become. As a result, the present inventors have found that the input position is normally detected (as input) and reached the present invention.

  In the position sensor of the present invention, a protective sheet in which the arithmetic average roughness Ra of the contact surface with the over clad layer is set to 10 μm or more is placed on the surface of the over clad layer of the sheet-like optical waveguide. The input part (pressing part) in the protective sheet can be prevented from sticking to the surface of the over clad layer. As a result, when inputting, when the protective sheet is pressed, the protective sheet can be recessed together with the sheet-shaped optical waveguide, and when the pressing is released, the protective sheet is quickly returned to the original flat shape together with the sheet-shaped optical waveguide. It will be possible to return to the state. Therefore, the position sensor of the present invention can detect the input position normally (as input). Furthermore, the position sensor of the present invention has excellent durability due to the provision of the protective sheet.

An embodiment of the position sensor of the present invention is schematically shown, (a) is a plan view thereof, and (b) is an enlarged sectional view of a central portion thereof. It is sectional drawing which shows the use condition of the said position sensor typically, (a) is a press state, (b) is the state which canceled the press. (A)-(f) is an enlarged plan view which shows typically the cross | intersection form of the grid | lattice-like core in the said position sensor. (A), (b) is an enlarged plan view which shows typically the course of the light in the cross | intersection part of the said grid | lattice-like core. It is sectional drawing which shows the use condition of the conventional position sensor typically, (a) is a press state, (b) is the state which canceled the press.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

  Fig.1 (a) is a top view which shows one Embodiment of the position sensor of this invention, FIG.1 (b) is the figure which expanded the cross section of the center part. The position sensor according to this embodiment includes a rectangular sheet-like optical waveguide W in which a lattice-like core 2 is sandwiched between a rectangular sheet-like underclad layer 1 and an overclad layer 3, and the lattice-like core 2. The light emitting element 4 connected to the one end surface of the linear core 2 to perform and the light receiving element 5 connected to the other end surface of the linear core 2 are provided. Furthermore, in this embodiment, the sheet-like optical waveguide W, the light emitting element 4 and the light receiving element 5 are provided on the surface of a rigid plate 7 such as a resin plate or a metal plate. A protective sheet S made of resin or the like is placed on the surface of the over clad layer 3. In the protective sheet S, the arithmetic average roughness Ra of the contact surface (back surface) with the overcladding layer 3 is set to 10 μm or more, and the arithmetic average roughness Ra of the opposite surface (front surface) is set in this embodiment. , Is set the same as the back side. In FIG. 1B, the rough surfaces of the front and back surfaces of the over clad layer 3 are exaggerated for easy understanding.

  The light emitted from the light emitting element 4 passes through the core 2 and is received by the light receiving element 5. And the surface part of the over clad layer 3 corresponding to the part of the lattice-like core 2 is an input region. In FIG. 1A, the core 2 is indicated by a chain line, and the thickness of the chain line indicates the thickness of the core 2. In FIG. 1A, the number of cores 2 is omitted. And the arrow of Fig.1 (a) has shown the direction where light travels.

  As described above, in the position sensor having the sheet-like optical waveguide W, the surface portion of the sheet-like optical waveguide W corresponding to the lattice-shaped core 2 portion (the surface portion of the over clad layer 3 in this embodiment) It is a great feature of the present invention to place the protective sheet S in which the arithmetic average roughness Ra of the contact surface with the over clad layer 3 is set to 10 μm or more. By providing such a protective sheet S, while improving the durability of the position sensor, the input portion (pressing portion) in the protective sheet S is prevented from sticking to the surface of the over clad layer 3. Can detect the input position normally (as input).

  That is, as shown in a sectional view in FIG. 2A, when characters or the like are input from the surface of the protective sheet S with a writing instrument such as a pen, the writing pressure by the pen tip 10a or the like is exceeded via the protective sheet S. The sheet-shaped optical waveguide W is pressed through the cladding layer 3. At this time, the protective sheet S is recessed together with the sheet-like optical waveguide W. As a result, the core 2 is deformed at the pressed portion by the pen tip 10a and the like, the propagation of light inside the core 2 is hindered, and the detection level of light at the light receiving element 5 is lowered. Is detected. In addition, you may perform the input of the said character etc. on the paper mounted on the surface of the said protection sheet S. FIG.

  Thereafter, as shown in a cross-sectional view in FIG. 2B, when the pressing is released, the input portion (pressing portion) in the protective sheet S is not attached to the surface of the over clad layer 3 as described above. There is no deformation constraint by the protective sheet S, and the protective sheet S quickly returns to the original flat state together with the sheet-like optical waveguide W. The protective sheet S normally has a restoring force, but even if it does not have a restoring force, it uses the restoring force of the sheet-like optical waveguide W to quickly return to the original flat state as described above. Return to. Thereby, the said position sensor can be quickly prepared for the next input (press).

  The protective sheet S will be described in more detail. As described above, the protective sheet S has an arithmetic average roughness Ra of a contact surface (back surface) with the over clad layer 3 set to 10 μm or more. It has become. In particular, if the arithmetic average roughness Ra is too large, the surface of the overcladding layer 3 tends to be damaged. Therefore, the arithmetic average roughness Ra is preferably set to 40 μm or less. The arithmetic average roughness Ra may be set by a polishing process, or a sheet material set in advance to such an arithmetic average roughness Ra may be purchased and used as the protective sheet S. .

  The thickness of the protective sheet S is preferably set in the range of 15 to 200 μm from the viewpoint of properly detecting the input. If the thickness is too thin, it tends to be difficult to set the arithmetic average roughness Ra, and if it is too thick, the sensitivity for detecting input (pressing) tends to decrease.

  Examples of the material for forming the protective sheet S include resins such as PET (polyethylene terephthalate), PI (polyimide), and PEN (polyethylene naphthalate), rubbers such as silicone rubber and acrylic rubber, and metals such as stainless steel and aluminum. Or paper.

  On the other hand, in this embodiment, the sheet-like optical waveguide W has a lattice-like core 2 embedded in the surface portion of the sheet-like underclad layer 1, and the surface of the underclad layer 1 and the top surface of the core 2. The sheet-like over clad layer 3 is formed in a state where the surface of the under clad layer 1 and the top surface of the core 2 are covered. The sheet-like optical waveguide W having such a structure can easily detect the pressing position in the input region because the over clad layer 3 can have a uniform thickness. The thickness of each layer is set, for example, such that the under cladding layer 1 is in the range of 10 to 500 μm, the core 2 is in the range of 5 to 100 μm, and the over cladding layer 3 is in the range of 1 to 200 μm.

  Examples of the material for forming the core 2, the under cladding layer 1 and the over cladding layer 3 include photosensitive resin, thermosetting resin, and the like, and the sheet-like optical waveguide W is manufactured by a manufacturing method corresponding to the forming material. Can do. The refractive index of the core 2 is set larger than the refractive indexes of the under cladding layer 1 and the over cladding layer 3. The refractive index can be adjusted by, for example, selecting the type of each forming material and adjusting the composition ratio. Further, a rubber sheet may be used as the undercladding layer 1 and the cores 2 may be formed in a lattice shape on the rubber sheet.

  Further, the elastic modulus of the core 2 is preferably set to be larger than the elastic modulus of the under cladding layer 1 and the over cladding layer 3. The reason is that if the elastic modulus is set in the opposite direction, the periphery of the core 2 becomes hard, so that the sheet shape has a considerably larger area than the area of the pen tip 10a or the like that presses the input region portion of the over clad layer 3. This is because the portion of the optical waveguide W is recessed and it is difficult to accurately detect the pressed position. Therefore, as each elastic modulus, for example, the elastic modulus of the core 2 is set within a range of 1 to 10 GPa, and the elastic modulus of the over clad layer 3 is set within a range of 0.1 GPa or more and less than 10 GPa. The elastic modulus of the cladding layer 1 is preferably set within a range of 0.1 to 1 GPa. In this case, since the elastic modulus of the core 2 is large, the core 2 is hardly crushed by a normal pressing force (the cross-sectional area of the core 2 hardly changes), but the core 2 sinks into the under cladding layer 1 by the pressing. 2 (see FIG. 2A), light leakage (scattering) occurs from the bent portion of the core 2 corresponding to the recessed portion. In the core 2, the light receiving element 5 [FIG. Since the light detection level in [Ref.] Decreases, the pressed position can be detected.

  In the above embodiment, the arithmetic average roughness Ra of the protective sheet S is set to be the same on the contact surface (back surface) with the over clad layer 3 and on the opposite surface (front surface). If the arithmetic average roughness Ra of the contact surface (back surface) is set to 10 μm or more, the arithmetic average roughness Ra of the opposite surface (front surface) is an arbitrary value regardless of the arithmetic average roughness Ra of the back surface. It's okay.

  Moreover, in the said embodiment, each cross | intersection part of the grid | lattice-like core 2 is normally formed in the state where all the four directions which cross | intersect were continuous, as shown in an enlarged plan view in Fig.3 (a). Others are acceptable. For example, as shown in FIG. 3 (b), only one intersecting direction may be divided by the gap G to be discontinuous. The gap G is formed of a material for forming the under cladding layer 1 or the over cladding layer 3. The width d of the gap G exceeds 0 (zero), and is usually set to 20 μm or less. Similarly, as shown in FIGS. 3C and 3D, two intersecting directions (two directions facing each other in FIG. 3C and two adjacent directions in FIG. 3D) are discontinuous. As shown in FIG. 3 (e), the three intersecting directions may be discontinuous, or as shown in FIG. 3 (f), all the four intersecting directions may be discontinuous. It may be discontinuous. Furthermore, it is good also as a grid | lattice shape provided with the 2 or more types of cross | intersection part of the said cross | intersection part shown to Fig.3 (a)-(f). That is, in the present invention, the “lattice shape” formed by the plurality of linear cores 2 means that a part or all of the intersections are formed as described above.

  In particular, as shown in FIGS. 3B to 3F, when at least one intersecting direction is discontinuous, the light crossing loss can be reduced. That is, as shown in FIG. 4 (a), in an intersection where all four intersecting directions are continuous, if one of the intersecting directions [upward in FIG. 4 (a)] is focused, the light incident on the intersection Part of the light reaches the wall surface 2a of the core 2 orthogonal to the core 2 through which the light has traveled, and is transmitted through the core 2 because the reflection angle on the wall surface is large [two points in FIG. (See chain line arrow). Such light transmission also occurs in a direction opposite to the above intersecting direction (downward in FIG. 4A). On the other hand, as shown in FIG. 4B, when the intersecting one direction [upward in FIG. 4B] is discontinuous by the gap G, the interface between the gap G and the core 2 is Part of the light that is formed and passes through the core 2 in FIG. 4 (a) has a smaller reflection angle at the interface, so that it is reflected at the interface without passing through and continues to travel through the core 2 [FIG. 4 (b), see the two-dot chain line arrow]. From this, as described above, if at least one intersecting direction is discontinuous, the light crossing loss can be reduced. As a result, it is possible to increase the detection sensitivity of the pressed position by the pen tip 10a or the like.

  Furthermore, in the above embodiment, the rigid plate 7 is provided to support the sheet-like optical waveguide W or the like, but the rigid plate 7 may not be provided. In that case, the input is performed in a state where the sheet-like optical waveguide W of the position sensor is placed on a hard flat table such as a table.

  In the above embodiment, an elastic layer such as a rubber layer may be provided on the back surface of the under cladding layer 1. In this case, even if the restoring force of the under-cladding layer 1, the core 2 and the over-cladding layer 3 is weak or they are originally made of a material having a weak restoring force, the elastic force of the elastic layer is utilized. Thus, the weak restoring force can be assisted, and after the pressing by the pen tip 10a or the like is released, the original state can be restored.

  Next, examples will be described together with comparative examples. However, the present invention is not limited to the examples.

[Formation material of under clad layer and over clad layer]
Component a: 75 parts by weight of an epoxy resin (Mitsubishi Chemical Corporation, YL7410).
Component b: 25 parts by weight of an epoxy resin (manufactured by Mitsubishi Chemical Corporation, JER1007).
Component c: 2 parts by weight of a photoacid generator (manufactured by Sun Apro, CPI101A).
By mixing these components a to c, materials for forming the under cladding layer and the over cladding layer were prepared.

[Core forming material]
Component d: 75 parts by weight of an epoxy resin (manufactured by Daicel Corporation, EHPE3150).
Component e: 25 parts by weight of an epoxy resin (manufactured by Toto Kasei Co., Ltd., KI-3000-4).
Component f: 1 part by weight of a photoacid generator (manufactured by ADEKA, SP170).
Component g: 50 parts by weight of ethyl lactate (manufactured by Wako Pure Chemical Industries, Ltd., solvent).
A core forming material was prepared by mixing these components d to g.

[Production of sheet-shaped optical waveguide]
An over clad layer was formed on the surface of the glass substrate by spin coating using the over clad layer forming material. The over cladding layer had a thickness of 25 μm, an elastic modulus of 3 MPa, and a refractive index of 1.503. The elastic modulus was measured using a viscoelasticity measuring device (TA instruments Japan Inc., RSA3).

  Next, a core was formed on the surface of the over clad layer by the photolithography method using the core forming material. The core had a thickness of 100 μm, the core width of the lattice portion was 100 μm, the pitch was 600 μm, the elastic modulus was 2 GPa, and the refractive index was 1.523.

  Next, an under clad layer was formed on the surface of the over clad layer by spin coating using the under clad layer forming material so as to cover the core. The thickness of the under cladding layer (thickness from the surface of the over cladding layer) was 500 μm, the elastic modulus was 3 MPa, and the refractive index was 1.503.

  And what stuck the double-sided tape (thickness 25 micrometers) on the single side | surface of the board | substrate (thickness 1mm) made from PET was prepared. Next, the other adhesive surface of the double-sided tape was attached to the surface of the under cladding layer, and in this state, the over cladding layer was peeled from the glass substrate.

[Example 1]
[Production of position sensor]
Thereafter, a sheet material made of PET (Eigami Industry Co., Ltd., Z mat film: thickness 50 μm, arithmetic average roughness Ra 35.1 μm on the front and back surfaces) was directly placed on the surface of the over clad layer as a protective sheet. In addition, arithmetic average roughness Ra was measured using the laser microscope (Lasertec company make, OPTELICS H300).

  Next, a light emitting element (Optowell, XH85-S0603-2s) is connected to one end face of the core, and a light receiving element (Hamamatsu Photonics, s10226) is connected to the other end face of the core. A position sensor was prepared.

[Example 2]
A sheet material made of PET (manufactured by Unitika Ltd., Emblet AT: thickness 38 μm) was prepared, and one surface thereof was polished with sandpaper of No. 800 and set to arithmetic average roughness Ra 12.4 μm. Then, the polished sheet material was used as a protective sheet, and the polished surface was placed in contact with the surface of the over clad layer. The other parts were the same as in Example 1.

Example 3
A sheet material made of PET (manufactured by Mitsubishi Chemical HD, Diafoil S100: thickness 50 μm) was prepared, and one side thereof was polished with an 800th sandpaper, and the arithmetic average roughness Ra was set to 10.5 μm. Then, the polished sheet material was used as a protective sheet, and the polished surface was placed in contact with the surface of the over clad layer. The other parts were the same as in Example 1.

[Comparative Example 1]
In the position sensor of Example 2, the sheet material was placed on the surface of the over clad layer as a protective sheet without being polished. The arithmetic average roughness Ra of the front and back surfaces of the sheet material (protective sheet) was 5.9 μm. The other parts were the same as in Example 2.

[Comparative Example 2]
In the position sensor of Example 3, the sheet material was placed on the surface of the over clad layer as it was as a protective sheet without polishing. The arithmetic average roughness Ra of the front and back surfaces of the sheet material (protective sheet) was 3.1 μm. The other parts were the same as in Example 3.

[With or without sticking]
After pressing the surface of the protective sheet with a ballpoint pen having a tip diameter of 0.5 mm, the pressing mark was visually observed. And when there was no interference fringe on the surface of the press mark, it was judged that there was no sticking, and when there was an interference fringe, it was judged that there was sticking. The results are shown in Table 1 below.

[Presence of noise]
90 μm thick paper was placed on the surface of the protective sheet of the position sensors of Examples 1 to 3 and Comparative Examples 1 and 2, and letters were written on the surface of the paper with a ballpoint pen having a tip diameter of 0.5 mm. Then, after finishing writing the character (release the press with the pen tip), the light reception spectrum was observed to confirm the presence or absence of noise. The results are shown in Table 1 below.

  From the results of Table 1 above, in the position sensors of Examples 1 to 3, since the arithmetic average roughness Ra of the contact surface of the protective sheet with the over clad layer is 10 μm or more, sticking is caused at the pressing portion of the protective sheet. Therefore, it can be seen that there is no noise. On the other hand, in the position sensors of Comparative Examples 1 and 2, since the arithmetic average roughness Ra is less than 10 μm, it can be seen that there is sticking at the pressing portion of the protective sheet, and therefore there is noise.

  In addition, even when the sheet material was replaced with a PI material, a silicone rubber material, or a stainless steel material, the same results as described above were obtained.

  The position sensor of the present invention can be used to detect the input position normally (as input) when inputting characters or the like with a writing instrument such as a pen.

S protective sheet W sheet-like optical waveguide 1 under clad layer 2 core 3 over clad layer 4 light emitting element 5 light receiving element

Claims (1)

A sheet-like optical waveguide having a plurality of linear cores formed in a lattice shape, an under clad layer that supports the core, and an over clad layer that covers the core, and is connected to one end face of the core A sheet-like position that includes a light-emitting element and a light-receiving element connected to the other end surface of the core, and identifies a pressing position by a change in the amount of light propagation of the core due to pressing to an arbitrary position on the surface of itself It is a sensor, Comprising: The protective sheet of the following (A) is mounted in the surface of the said over clad layer, The position sensor characterized by the above-mentioned.
(A) The protective sheet in which the arithmetic average roughness Ra of the contact surface with the over cladding layer is set to 10 μm or more.

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