Patent Description:
Vehicle switch devices that operate various in-vehicle devices by touch operation are known (see, for example, Patent Literature <NUM>). The technique described in Patent Literature <NUM> includes a light source, a display area in which a light emitted from the light source is transmitted and displayed, a touch switch unit, a touch detection unit, and a light source controller that changes a light amount of the emitted light.

Patent Literature <NUM>: <CIT>
<CIT> discloses a display device comprising at least one display means, a printed circuit board having at least one electrical illuminant which is contacted for the purpose of generating light from electrical energy on the printed circuit board, at least one optical waveguide having an input coupling surface, an output coupling surface and a light guiding section designed for guiding light from the illuminant that enters via the input coupling surface to the output coupling surface, which is optically coupled to the display means, and a holder fixed to the printed circuit board, said holder carrying the at least one optical waveguide. <CIT> discloses a display unit including light emitting means which are disposed on a substrate, a light transmission lens which guides the light from the light emitting means, a holder which is mounted with holes for capturing of the light from the light emitting means on one surface and is inserted with the light transmission lens and a display means which makes the prescribed display in accordance with the light from the light emitting means which is disposed at the light transmission lens and to which the light is guide by the light transmission lens. The display unit includes at least <NUM> reflection surfaces which are disposed at the light transmission lens, reflect the light from the light emitting means and project the light only to the prescribed display part of the display means, and light shielding grooves which are disposed at the light transmission lens, are projected with the light from the light emitting means only in the prescribed display part and prevents the leakage of the light to other display parts. Further, attention is drawn to <CIT> and <CIT>.

In a display device including a switch device having a display area, a light source is disposed on a back surface side of a display plate on which the display area is disposed, and the display area on a front surface is displayed. Therefore, it is desirable to reduce unevenness in brightness of the front surface.

The present disclosure has been made in view of the above, and an object thereof is to provide a display device, an electronic device, and an assembling method capable of reducing unevenness in brightness of a front surface.

According to one aspect, there is provided an assembling method of a display device comprising a substrate on which at least one light source is disposed; a display plate that is disposed to face the substrate; a tubular panel that surrounds and holds a periphery of the substrate and a periphery of the display plate; and a lens that is disposed between the substrate and the display plate and guides light emitted from the at least one light source; wherein the tubular panel has at least one rib protruding from an inner peripheral surface thereof, and the lens has at least one slide groove in which the at least one rib is movable forward and backward when the lens is assembled into the tubular panel and has at least one claw portion disposed adjacent to the at least one slide groove, the assembling method comprising: sliding the lens in a first direction, in a state where the at least one rib enters the at least one slide groove from a rear side of the tubular panel, and then sliding the lens in a second direction different from the first direction; assembling the display plate into the tubular panel from a front side; and assembling the substrate into a rear portion of the tubular panel into which the display plate and the lens are assembled, in a state where the at least one claw portion is positioned between the at least one rib and the display plate.

According to one aspect, there is provided an electronic device comprising: a display panel having a display surface on a front surface; a front panel surrounding a periphery of the display panel; and the display device described above adjacent to the front panel.

According to one aspect, there is provided an assembling method of a display device comprising: a substrate on which at least one light source is disposed; a display plate that is disposed to face the substrate; a tubular panel that surrounds and holds a periphery of the substrate and a periphery of the display plate; and a lens that is disposed between the substrate and the display plate and guides light emitted from the at least one light source; wherein the tubular panel has at least one rib protruding from an inner peripheral surface thereof, and the lens has at least one slide groove in which the at least one rib is movable forward and backward when the lens is assembled into the tubular panel and has at least one claw portion disposed adjacent to the at least one slide groove, the assembling method comprising: sliding the lens in a first direction, in a state where the at least one rib enters the at least one slide groove from a rear side of the tubular panel, and then sliding the lens in a second direction different from the first direction; assembling the display plate into the tubular panel from a front side; and assembling the substrate into a rear portion of the tubular panel into which the display plate and the lens are assembled, in a state where the at least one claw portion is positioned between the at least one rib and the display plate.

A display device, an electronic device, and an assembling method according to the present disclosure obtain an effect of reducing unevenness in brightness of a front surface.

Hereinafter, embodiments of a display device, an electronic device, and an assembling method according to the present disclosure will be described in detail with reference to the drawings.

<FIG> is a front view illustrating an electronic device <NUM> according to a first embodiment. As illustrated in <FIG>, the electronic device <NUM> according to the present embodiment is, for example, an audio visual (AV) integrated car navigation device mounted inside a vehicle. The electronic device <NUM> has a display panel <NUM>, a front panel <NUM>, and a display device <NUM>.

Note that in the following description, an upper side of the electronic device <NUM> in normal use is referred to as an upper side of the electronic device <NUM>, and a lower side of the electronic device <NUM> in normal use is referred to as a lower side of the electronic device <NUM>. In addition, in the following description, a left-right direction when the electronic device <NUM> is viewed from a side of the front panel <NUM> is referred to as a left-right direction of the electronic device <NUM>.

The display panel <NUM> is formed in a rectangular shape and has a display surface 2a on a front face. The front face is a face visually recognized by an occupant of the vehicle. In the case of a car navigation device, the front face is a face facing a rear in the vehicle. The display surface 2a is formed in a rectangular shape smaller than the rectangular shape of the display panel <NUM>. The display surface 2a is disposed inside an outer edge <NUM> of the display panel <NUM>. In the present embodiment, in the display panel <NUM>, the display surface 2a is a touch panel.

The front panel <NUM> is formed in a rectangular shape so as to surround the display panel <NUM>. The front panel <NUM> has a rectangular frame portion <NUM> surrounding a periphery of the display panel <NUM> and a rectangular window portion <NUM> opening the display surface 2a of the display panel <NUM> inside the frame portion <NUM>.

<FIG> is an exploded perspective view of the display device <NUM> according to the first embodiment. <FIG> is a cross-sectional view of the display device <NUM> according to the first embodiment. As illustrated in <FIG>, the display device <NUM> is disposed adjacent to a peripheral edge of the front panel <NUM>. In the present embodiment, the display device <NUM> is disposed on a lower side of the front panel <NUM>. In the present embodiment, the display device <NUM> has a rectangular shape that is elongated in the left-right direction as viewed in a front-rear direction. The display device <NUM> has a substrate <NUM>, a display plate <NUM>, a panel <NUM>, and a lens <NUM>.

The substrate <NUM> is disposed along the display surface 2a of the display panel <NUM>. In the present embodiment, the substrate <NUM> has a rectangular shape that is elongated in the left-right direction. At least one light source <NUM> is disposed on a front surface 6a of the substrate <NUM>. The light source <NUM> emits a light toward a front side. The light source <NUM> is, for example, a light emitting diode (LED). In the present embodiment, the five light sources <NUM> are arranged side by side in the left-right direction.

The display plate <NUM> is disposed along the display surface 2a of the display panel <NUM>. The display plate <NUM> is disposed on the front side of the substrate <NUM> and is disposed to face the substrate <NUM>. In the present embodiment, the display plate <NUM> has a rectangular shape as viewed in the front-rear direction. The display plate <NUM> is formed in a plate shape and is disposed so as to close the front side of the panel <NUM> in which the substrate <NUM>, the display plate <NUM>, and the lens <NUM> are accommodated. The display plate <NUM> has a dark color such as black or gray, for example.

On a front surface 7a of the display plate <NUM>, a display unit <NUM> that displays characters, numbers, figures, and symbols such as a logo or a mark visually recognizable by the occupant of the vehicle is disposed. In the present embodiment, five display units <NUM> are arranged on the display plate <NUM> side by side in the left-right direction.

Each of the display units <NUM> has a transmission unit <NUM> formed on the front surface 7a of the display plate <NUM>. The transmission unit <NUM> transmits the light emitted from each of the light sources <NUM>. In the transmission unit <NUM>, for example, shapes such as characters, numbers, figures, and symbols in light colors, such as white and a translucent color, capable of transmitting the light are arranged. In the present embodiment, in the transmission unit <NUM>, shapes of characters of "AAA", "BBB", "CCC", "DDD", and "EEE" are arranged in order from the left side.

<FIG> is a perspective view of the panel <NUM> illustrated in <FIG>. As illustrated in <FIG>, the panel <NUM> surrounds and holds a periphery of the substrate <NUM>, an outer edge <NUM> around the display plate <NUM>, and a periphery of the lens <NUM>. The panel <NUM> is formed in a tubular shape surrounding the periphery of the substrate <NUM>, the outer edge <NUM> of the display plate <NUM>, and the periphery of the lens <NUM>. In the present embodiment, the panel <NUM> is formed in a rectangular tube shape.

In the panel <NUM>, a holding portion <NUM> that holds the outer edge of a base portion <NUM> of the lens <NUM> is disposed on an inner peripheral surface. The holding portion <NUM> protrudes from the inner peripheral surface of the panel <NUM>. The holding portion <NUM> is formed in a rectangular frame shape having an opening smaller than the outer edge of the base portion <NUM> of the lens <NUM>. The holding portion <NUM> positions the lens <NUM> in the front-rear direction in the panel <NUM>.

The panel <NUM> has at least one rib <NUM> protruding from the inner peripheral surface. The rib <NUM> is formed integrally with the holding portion <NUM>. The panel <NUM> has the ribs <NUM> arranged at an interval in the left-right direction. Each of the ribs <NUM> regulates deflection of the panel <NUM> due to a heat generation of the display panel <NUM> or an impact applied from the outside. The rib <NUM> connects opposing surfaces of the inner peripheral surface of the panel <NUM> and extends in a vertical direction. The opening of the holding portion <NUM> is defined by the ribs <NUM>. In the present embodiment, the four ribs <NUM> are disposed. In the present embodiment, each of the ribs <NUM> has a square cross section orthogonal to a central axis thereof.

<FIG> is a perspective view of the lens <NUM> illustrated in <FIG>. <FIG> is a partially enlarged view of the lens <NUM>. <FIG> is a partially enlarged view of a slide groove <NUM>. As illustrated in <FIG>, the lens <NUM> is disposed along the display surface 2a of the display panel <NUM>. As illustrated in <FIG>, the lens <NUM> is disposed on the front side of the substrate <NUM> and on the rear side of the display plate <NUM>. In other words, the lens <NUM> is disposed so as to be sandwiched between the substrate <NUM> and the display plate <NUM>. The lens <NUM> is disposed to face the substrate <NUM> and the display plate <NUM>. The lens <NUM> is an optical member that guides the light emitted from the light source <NUM>. The lens <NUM> is, for example, a light guide lens. The lens <NUM> is made of a milky white resin material.

More specifically, the lens <NUM> has the base portion <NUM>, multiple protrusions <NUM> protruding forward from the base portion <NUM>, and multiple claw portions <NUM> each protruding leftward from the left side of a front end portion of each of the protrusions <NUM>. In the lens <NUM>, the slide groove <NUM> is formed between the protrusions <NUM> that are adjacent to each other. The base portion <NUM>, the protrusions <NUM>, and the claw portion <NUM> are integrally formed.

The multiple protrusions <NUM> are connected in the left-right direction by the base portion <NUM>. In the present embodiment, the five protrusions <NUM> are disposed. As illustrated in <FIG>, each of the protrusions <NUM> is recessed on the rear surface side. As illustrated in <FIG>, in an assembled state, a front surface 92a of the protrusion <NUM> abuts on a back surface 7b of the display plate <NUM>. In the assembled state, the protrusion <NUM> is positioned in a window portion <NUM> surrounded by the holding portion <NUM> and the rib <NUM>.

The claw portion <NUM> is disposed adjacent to the slide groove <NUM>. In the assembled state, the claw portion <NUM> is positioned between the rib <NUM> and the display plate <NUM>. In the assembled state, the claw portion <NUM> is positioned on the front side of the rib <NUM>, and a front surface 93a of the claw portion <NUM> abuts on the back surface 7b of the display plate <NUM>.

In the slide groove <NUM>, the rib <NUM> is movable forward and backward when the lens <NUM> is assembled into the panel <NUM>. As illustrated in <FIG>, in the slide groove <NUM>, a straight line L1 passing through a center C1 of a starting end 94a, which is one end, and a center C2 of a terminal end 94b, which is another end, intersects with an optical axis M of the light source <NUM>. The starting end 94a is an entrance through which the rib <NUM> enters and exits. The slide groove <NUM> is bent. In the present embodiment, the slide groove <NUM> is formed in an L shape as viewed in the vertical direction. In the assembled state, the rib <NUM> is positioned in the slide groove <NUM>. When the lens <NUM> is assembled, the lens <NUM> is slid to the front side, in a state where the rib <NUM> is positioned in the slide groove <NUM>, and then the lens <NUM> is slid to the left side, whereby the lens <NUM> is assembled into the panel <NUM> from the rear side.

As illustrated in <FIG>, a center C3 is a center of the rib <NUM> in a state where the rib <NUM> is positioned at the starting end 94a of the slide groove <NUM>. The state in which the rib <NUM> is positioned at the starting end 94a of the slide groove <NUM> refers to a state in which the entire rib <NUM> enters the slide groove <NUM>. A center C4 is a center of the rib <NUM> in a state where the rib <NUM> is positioned at the terminal end 94b of the slide groove <NUM>. The state in which the rib <NUM> is positioned at the terminal end 94b of the slide groove <NUM> refers to a state in which the lens <NUM> is assembled into the panel <NUM>. A straight line L2 passing through the center C3 and the center C4 intersects with the optical axis M of the light source <NUM>.

A thickness of each portion of the lens <NUM> will be described with reference to <FIG>. A thickness d1 is a thickness of the claw portion <NUM>. The thickness d1 of the claw portion <NUM> is set to such a thickness that the claw portion <NUM> can guide the light emitted from the light source <NUM> to set the display plate <NUM> abutting on the claw portion <NUM> to a predetermined brightness. A thickness d2 of the protrusion <NUM> and a thickness d3 of the base portion <NUM> are preferably the same as the thickness d1 of the claw portion <NUM> so that unevenness in brightness of the front surface 7a of the display plate <NUM> is reduced and the brightness becomes uniform. The lens <NUM> preferably has a uniform thickness.

Next, an assembling method and operation of the electronic device <NUM> will be described with reference to <FIG> is a perspective view illustrating an assembling procedure of the display device <NUM> according to the first embodiment.

As illustrated in an upper of <FIG>, the lens <NUM> is assembled from the rear side of the panel <NUM>. In a state where the rib <NUM> of the panel <NUM> enters the slide groove <NUM> of the lens <NUM>, the lens <NUM> is slid forward, which is a first direction, indicated by the arrow. A rear surface 82b of the rib <NUM> abuts on a front surface 91a of the base portion <NUM>. The protrusion <NUM> is positioned in the window portion <NUM> surrounded by the holding portion <NUM> and the rib <NUM>.

As illustrated in an lower of <FIG>, in a state where the rear surface 82b of the rib <NUM> abuts on the front surface 91a of the base portion <NUM>, the lens <NUM> is slid to a lateral side, which is a second direction, indicated by the arrow until the rib <NUM> abuts on a peripheral surface 92b of the protrusion <NUM> that defines the terminal end 94b of the slide groove <NUM>. In this way, the lens <NUM> is assembled into the panel <NUM>.

Next, the display plate <NUM> is assembled, from the front side, into the panel <NUM> into which the lens <NUM> is assembled. In a state where the display plate <NUM> is assembled into the panel <NUM>, the front surface 92a of the protrusion <NUM> and the front surface 93a of the claw portion <NUM> abut on the back surface 7b of the display plate <NUM>.

Next, the substrate <NUM> is assembled into the rear portion of the panel <NUM> into which the display plate <NUM> and the lens <NUM> are assembled. In this way, the assembled display device <NUM> is assembled on a lower side of the electronic device <NUM>.

In the display device <NUM> disposed on the lower side of the electronic device <NUM>, after the electronic device <NUM> is activated during activation of the vehicle, the light source <NUM> disposed on the substrate <NUM> emits the light forward. The light emitted from the light source <NUM> enters the lens <NUM> from the rear side. The light incident on the lens <NUM> is guided by the lens <NUM> and emitted from the peripheral surface of the lens <NUM> to the outside. The light emitted from the front surface 91a of the base portion <NUM> of the lens <NUM>, the front surface 92a of the protrusion <NUM>, and the front surface 93a of the claw portion <NUM> is incident on the display plate <NUM> from the back surface 7b. On the front surface 7a of the display plate <NUM>, portions abutting on the front surface 92a of the protrusion <NUM> and the front surface 93a of the claw portion <NUM> are brightened by the light emitted from the front surface 92a of the protrusion <NUM> and the front surface 93a of the claw portion <NUM>. In addition, on the front surface 7a of the display plate <NUM>, a portion facing the starting end 94a of the slide groove <NUM> is brightened by the light emitted from the front surface 91a of the base portion <NUM> and passing through the slide groove <NUM>. The claw portion <NUM> guides the light incident on the lens <NUM> to brighten the display plate <NUM> positioned on the front side of the rib <NUM>. The claw portion <NUM> compensates for the light, which would have been blocked by the rib <NUM> if there had been no claw portion <NUM>, and reduces unevenness in brightness of the display plate <NUM>. In this way, the unevenness in brightness is reduced on the front surface 7a of the display plate <NUM>. The transmission unit <NUM> of the display plate <NUM> transmits the light into shapes such as characters, numbers, figures, and symbols. As a result, shapes such as characters, numbers, figures, and symbols are displayed brightly on the transmission unit <NUM> of the display plate <NUM>.

As described above, in the present embodiment, the display device <NUM> disposed on the lower side of the electronic device <NUM> includes the substrate <NUM>, the display plate <NUM>, the lens <NUM>, and the panel <NUM> that surrounds and holds the substrate <NUM>, the display plate <NUM>, and the lens <NUM>. In addition, in the present embodiment, the lens <NUM> is provided with the slide groove <NUM> in which the rib <NUM> protruding from the inner peripheral surface of the panel <NUM> is movable forward and backward. Moreover, in the present embodiment, the claw portion <NUM> disposed adjacent to the slide groove <NUM> is positioned between the rib <NUM> and the display plate <NUM> in the assembled state. As a result, according to the present embodiment, on the front surface 7a of the display plate <NUM>, the portions abutting on the front surface 92a of the protrusion <NUM> and the front surface 93a of the claw portion <NUM> can be brightened by the light emitted from the lens <NUM>. Moreover, according to the present embodiment, on the front surface 7a of the display plate <NUM>, the portion facing the starting end 94a of the slide groove <NUM> can be brightened by the light emitted from the front surface 91a of the base portion <NUM> and passing through the slide groove <NUM>. Furthermore, according to the present embodiment, the claw portion <NUM> can guide the light incident on the lens <NUM> to brighten the display plate <NUM> positioned on the front side of the rib <NUM>. In the present embodiment, the light blocked by the rib <NUM> can be compensated by the claw portion <NUM>, and the unevenness in brightness of the display plate <NUM> can be reduced. In the present embodiment, it is possible to eliminate a portion where the light emitted from the lens <NUM> is blocked by the rib <NUM> on the front surface 7a of the display plate <NUM>. In this way, according to the present embodiment, it is possible to reduce the unevenness in brightness and make the brightness uniform on the front surface 7a of the display plate <NUM>. In the present embodiment, the transmission unit <NUM> of the display plate <NUM> transmits the light to shapes of characters, numbers, figures, symbols, and the like arranged and can brightly display the shapes of the characters, numbers, figures, symbols, and the like without the unevenness.

Here, a conventional display device 5X will be described for comparison with reference to <FIG> and <FIG>. <FIG> is a perspective view of a conventional lens 9X. <FIG> is a cross-sectional view of a conventional display device 5X. The conventional display device 5X is different from the display device <NUM> in that the lens 9X does not have a claw portion. In the display device 5X, since the claw portion is not disposed on the front side of the rib <NUM>, the brightness of the display plate <NUM> positioned on the front side of the rib <NUM> is reduced as compared with the surroundings. In the display device 5X, on the front surface 7a of the display plate <NUM>, a portion where the light emitted from the lens <NUM> is blocked by the rib <NUM> becomes darker than the surroundings.

<FIG> is a partially enlarged view of another example of the display device <NUM> according to the first embodiment. <FIG> is a partially enlarged view of another example of the display device <NUM> according to the first embodiment. <FIG> is a partially enlarged view of another example of the display device <NUM> according to the first embodiment. In the following description, the same constituent elements as those of the display device <NUM> are denoted by the same reference numerals or corresponding reference numerals, and a detailed description thereof will be omitted.

As illustrated in <FIG>, a rib 82A has a cross section including a surface inclined with respect to an optical axis of a center ray of the light source <NUM>. The rib 82A orthogonal to a central axis has a triangular cross section. A peripheral surface 82Aa and a peripheral surface 82Ab of the rib 82A are disposed so as to intersect with the optical axis of the light source <NUM>. A peripheral surface 82Ac of the rib 82A is disposed along the display surface 2a of display panel <NUM>. As a result, an area where the rib 82A and the claw portion <NUM> face each other is reduced. A space is formed between the peripheral surface 82Aa of the rib 82A and the peripheral surface 92b of the protrusion <NUM>. As a result, it is possible to prevent the light emitted from the lens <NUM> toward the display plate <NUM> from being blocked by the rib 82A.

As illustrated in <FIG>, a rib 82B has a rectangular cross section. The rib 82B orthogonal to a central axis has a rhombic cross section orthogonal to a central axis. All peripheral surfaces of the rib 82B are disposed so as to intersect with the optical axis of the light source <NUM>. As a result, an area where the rib 82B and the claw portion <NUM> face each other is reduced. A space is formed between a peripheral surface 82Ba of the rib 82B and the peripheral surface 92b of the protrusion <NUM>. As a result, it is possible to suppress the light emitted from the lens <NUM> toward the display plate <NUM> from being blocked by the rib 82B.

As illustrated in <FIG>, at least a part of the peripheral surface of a rib 82C has an arc-shaped cross section. The rib 82C orthogonal to a central axis has a circular cross section. A space is formed between a peripheral surface of the rib 82C and the peripheral surface 92b of the protrusion <NUM>. As a result, it is possible to suppress the light emitted from the lens <NUM> toward the display plate <NUM> from being blocked by the rib 82C.

A display device <NUM> according to the present embodiment will be described with reference to <FIG> is a partially enlarged view of the display device <NUM> according to the second embodiment. The present embodiment is different from the first embodiment in a rib 82D and a slide groove 94D of a lens 9D. The rib 82D is formed in the same manner as the rib 82B illustrated in <FIG>.

The slide groove 94D is formed along a direction intersecting with the optical axis of the light source <NUM>. The slide groove 94D extends obliquely from the left side, from the front side to the rear side, as viewed in the vertical direction. A claw portion 93D is disposed adjacent to the slide groove 94D.

When the lens 9D is assembled, the lens 9D is slid obliquely forward, in a state where the rib 82D enters the slide groove 94D of the lens 9D, until a front surface 92Da of a protrusion 92D and a front surface 93Da of the claw portion 93D abut on the back surface 7b of the display plate <NUM>.

As described above, in the present embodiment, the slide groove 94D is formed along the direction intersecting with the optical axis of the light source <NUM>. According to the present embodiment, since the slide groove 94D does not have a bent portion, the lens 9D can be smoothly assembled.

A display device <NUM> according to the present embodiment will be described with reference to <FIG> is a partially enlarged view of the display device <NUM> according to a third embodiment. The present embodiment is different from the first embodiment in a rib 82E and a slide groove 94E of a lens 9E. The rib 82E is formed in the same manner as the rib 82C illustrated in <FIG>.

The slide groove 94E is curved. A claw portion 93E is disposed adjacent to the slide groove 94E.

When the lens 9E is assembled, the lens 9E is slid obliquely forward, in a state where the rib 82E enters the slide groove 94E, until a front surface 92Ea of a protrusion 92E and a front surface 93Ea of the claw portion 93E abut on the back surface 7b of the display plate <NUM>.

As described above, in the present embodiment, the slide groove 94E is formed in a curved shape. According to the present embodiment, since the slide groove 94E does not have a bent portion, the lens 9E can be smoothly assembled.

The above-described constituent elements include those that can be easily assumed by those skilled in the art and those that are substantially the same. Moreover, the above-described configurations can be appropriately combined.

Although the display device has been described above, the present invention is not limited thereto. For example, the display device may be a display device that has a function as a switch and brightly displays characters, numbers, figures, symbols, and the like.

Claim 1:
A display device (<NUM>) comprising:
a substrate (<NUM>) on which light sources (<NUM>) are disposed;
a display plate (<NUM>) that is disposed to face the substrate (<NUM>);
a tubular panel (<NUM>) that surrounds and holds a periphery of the substrate (<NUM>) and a periphery of the display plate (<NUM>); and
a lens (<NUM>) that is disposed between the substrate (<NUM>) and the display plate (<NUM>) and guides light emitted from the light sources (<NUM>);
wherein
the lens (<NUM>) has at least one slide groove (<NUM>) and at least one claw portion (<NUM>) disposed adjacent to the at least one slide groove (<NUM>),
characterised in that the tubular panel (<NUM>) has at least one rib (<NUM>) protruding from an inner peripheral surface thereof,
wherein the slide groove (<NUM>) is configured to receive the at least one rib (<NUM>), such that when the lens (<NUM>) is assembled into the tubular panel (<NUM>), in a state where the rib (<NUM>) of the panel (<NUM>) enters the slide groove (<NUM>) of the lens (<NUM>), the lens (<NUM>) is configured to be slid forward, which is a first direction of the lens (<NUM>) towards the display plate (<NUM>), till a rear surface (82b) of the rib (<NUM>) abuts on a front surface (91a) of the base portion of the lens (<NUM>) and then the lens (<NUM>) is configured to be slid to a lateral direction, different to the first direction, and
the at least one claw portion (<NUM>) is positioned between the at least one rib (<NUM>) and the display plate (<NUM>) in an assembled state.