JP7517838B2 - RF tag and transparent antenna - Google Patents

Description

The present invention relates to an RF tag and a transparent antenna used therewith.

Transparent antennas are used in a variety of situations. For example, a film antenna that is installed on the windshield of an automobile is known as an antenna for receiving various radio waves such as television radio waves and FM radio waves, and radio waves related to position coordinate information from GPS (Global Positioning System) satellites used in car navigation systems.

Film antennas are also used in radio frequency identification (RFID) applications that are widely used in many industries, including transportation, delivery, manufacturing, waste management, postal tracking, baggage matching on airplanes, and toll management on toll roads. RF tags are useful for tracking deliveries from the supplier to the customer and through the customer's supply chain. For such film antennas, a technique has been proposed that improves the invisibility of the conductive pattern by forming the antenna with a fine conductive pattern (see, for example, Patent Documents 1 to 5).

JP 2011-66610 A JP 2011-91788 A JP 2017-175540 A JP 2003-209421 A JP 2016-105624 A

As described in the above patent document, miniaturization of the conductive pattern improves its invisibility. However, miniaturization of the conductive pattern may make it difficult to join the conductive pattern constituting the antenna to a semiconductor element such as an IC chip that is electrically connected to the conductive pattern.

Here, for example, in Patent Document 4, when bonding an IC chip, a child antenna pattern is formed around the IC chip in advance to generate an IC chip label. The child antenna pattern is then bonded so as to be conductive to the parent antenna pattern formed on the substrate. However, the IC chip and the child antenna pattern around it are highly visible, which can reduce the design quality of the resulting RF tag.

On the other hand, for example, Patent Document 5 describes the use of an anisotropic conductive paste (ACP) to bond an IC chip to a conductive pattern that constitutes an antenna. ACP contains conductive particles. ACP is characterized in that when electronic components are bonded together using the conductive particles, it achieves conductivity in the out-of-plane direction (direction perpendicular to the bonding surface) of the bonding surface, but does not exhibit conductivity in the in-plane direction (direction parallel to the bonding surface).

Here, when an antenna is constructed with a conductive pattern having a line width of 5 μm or less, conductive particles must be positioned on the conductive pattern in order to electrically bond the antenna to the semiconductor element using ACP. Here, if the particle size of the conductive particles and the line width of the conductive pattern are approximately the same, there is a high probability that the conductive particles will be positioned in openings where no conductive pattern is formed, and as a result, conductive bonding using ACP becomes difficult.

To address the above-mentioned issues with conductive bonding, it is sufficient to make only the joint with the semiconductor element a metal surface rather than a conductive pattern, but this increases the visibility of the formed metal surface. In this case, when observed from the back side of the surface on which the semiconductor element is disposed, the metal surface is observed as a bright spot, which is not desirable in terms of appearance. This is presumably because when a metal surface is formed on the surface of a transparent substrate, the surface in contact with the transparent substrate becomes a very smooth metal surface, which increases the regular reflectivity, resulting in a bright spot that stands out more in reflected light than the surroundings. Transparent antennas are particularly undesirable because they are often viewed from both sides of the transparent substrate in terms of their applications.

The present invention was made in consideration of the above problems, and aims to provide an RF tag and a transparent antenna used therewith that have good electrical connection with a semiconductor element and excellent invisibility of the connection with the semiconductor element from the back side.

The present invention relates to the following [1] to [9].
[1]
A transparent substrate;
An antenna portion disposed on the transparent base material;
a joint portion disposed on the transparent base material and electrically joined to the antenna portion;
a semiconductor element on the bonding portion and electrically bonded to the bonding portion;
the antenna portion is configured by a first conductive pattern having a line width of 0.25 μm or more and 5.0 μm or less,
the bonding portion is formed of a second conductive pattern having a line width of 0.25 μm or more and 5.0 μm or less,
The visible light transmittance _T2 of the joint is 30% or more and 80% or less, and
The visible light transmittance _T2 has a value smaller than the visible light transmittance _T1 of the antenna portion.
RF tag.
[2]
The opening width _W4 of the opening in the bonding portion where the second conductive pattern is not formed is 1.0 μm or more and 10 μm or less.
The RF tag described in [1].
[3]
The opening width _W4 is smaller than an opening width _W2 of an opening in the antenna portion where the first conductive pattern is not formed,
The opening width _W2 is 60 μm or more and 300 μm or less.
An RF tag according to [1] or [2].
[4]
an occupancy area ratio _A2 per unit area of the second conductive pattern formed in the bonding portion is greater than an occupancy area ratio _A1 per unit area of the first conductive pattern formed in the antenna portion;
The occupied area ratio _A2 is 30% or more and 80% or less,
The occupied area ratio _A1 is 0.5% or more and 10% or less.
An RF tag according to any one of [1] to [3].
[5]
The bonding portion and the semiconductor element are electrically bonded by conductive particles.
An RF tag according to any one of [1] to [4].
[6]
the bonding portion and the semiconductor element are electrically bonded by an anisotropic conductive adhesive containing the conductive particles;
The RF tag described in [5].
[7]
The opening in the bonding portion where the second conductive pattern is not formed has an opening width _W4 narrower than the average particle diameter of the conductive particles.
An RF tag according to [5] or [6].
[8]
The conductive particles have an average particle size D of 3 μm or more and 100 μm or less,
7. The RF tag according to claim 4, wherein the average particle size D, the opening width W ₄ , and the thickness H ₂ of the conductive thin wires constituting the conductive pattern satisfy the following formula (1): D=H 2 /H 2 ≦D≦1.
(W ₄ ) ² /4 < (D/2) ² - (D/2 - H ₂ ) ² (1)
[9]
A transparent substrate;
An antenna portion disposed on the transparent base material;
a joint portion disposed on the transparent base material and electrically joined to the antenna portion,
the antenna portion is configured by a first conductive pattern having a line width of 0.25 μm or more and 5.0 μm or less,
the bonding portion is formed of a second conductive pattern having a line width of 0.25 μm or more and 5.0 μm or less,
The visible light transmittance _T2 of the joint is 30% or more and 80% or less, and
The visible light transmittance _T2 has a value smaller than the visible light transmittance _T1 of the antenna portion.
Transparent antenna.

The present invention provides an RF tag and a transparent antenna used therewith that have good electrical connection between the antenna portion and the semiconductor element and excellent invisibility of the connection with the semiconductor element from the back side.

FIG. 1 is a schematic diagram of an RF tag 100 according to the present embodiment. FIG. 2 is a side view showing a schematic configuration of the RF tag 100 according to this embodiment. FIG. 3 is an enlarged view of a portion S1a in FIG. 1, showing a schematic configuration of the current collecting portion 12, the joint portion 121, and the antenna portion 13. As shown in FIG. FIG. 4 is an enlarged view of a portion S1 in FIG. FIG. 5 is a schematic diagram showing another embodiment of the first pattern 131. In FIG. FIG. 6 is an enlarged view of a portion S2 in FIG. 3, showing second conductive pattern 1211 constituting bonding portion 121. As shown in FIG. FIG. 7 is a schematic diagram showing another embodiment of the antenna portion and the joint portion. FIG. 8 is an enlarged view of a portion S1b in FIG.

Below, an embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described in detail with reference to the drawings as necessary, but the present invention is not limited to this, and various modifications are possible without departing from the gist of the invention. In the drawings, the same elements are given the same reference numerals, and duplicated explanations will be omitted. Furthermore, unless otherwise specified, positional relationships such as up, down, left, and right will be based on the positional relationships shown in the drawings. Furthermore, the dimensional ratios of the drawings are not limited to those shown in the drawings.

The RF tag according to this embodiment comprises a transparent substrate, an antenna portion disposed on the transparent substrate, a joint portion disposed on the transparent substrate and electrically joined to the antenna portion, and a semiconductor element disposed on the joint portion and electrically joined to the joint portion.
The antenna portion is constituted by a first conductive pattern having a line width of 0.25 μm or more and 5.0 μm or less.
The bonding portion is constituted by a second conductive pattern having a line width of 0.25 μm or more and 5.0 μm or less.
In addition, the visible light transmittance _T2 of the joint portion is 30% or more and 80% or less, and the visible light transmittance _T2 has a value smaller than the visible light transmittance _T1 of the antenna portion.

By having the above configuration, the RF tag according to this embodiment has good electrical connection between the antenna portion and the semiconductor element, and has excellent invisibility of the connection with the semiconductor element from the back side.

[RF tag]
"RF tag" is an abbreviation of "Radio Frequency tag". Incidentally, RF tags may also be called by other names such as electronic tags, IC tags, wireless tags, and RFID tags. In this embodiment, the "RF tag" refers to a tag that is used together with a corresponding reader and can transmit or receive data between the reader and the reader in a non-contact manner. Such non-contact transmission or reception is preferably performed by radio waves. Incidentally, the reader may also serve as a writer (writing). In this embodiment, the RF tag 100 is a passive tag that does not have a built-in battery and operates using radio waves received from a reader/writer as an energy source. However, the RF tag 100 of this embodiment may be an active tag that further has a built-in battery (not shown) and uses the power as a power source for transmission and reception and for internal circuits, or a semi-passive tag that has a built-in battery as a power source for other sensors and sensors. In this embodiment, the RF tag refers to a tag that has an antenna and is capable of transmitting and receiving a specific frequency. Therefore, even if it is called an IC tag, it is included in the RF tag of this embodiment as long as it satisfies the above configuration.

1 is a schematic diagram of an RF tag 100 according to this embodiment. FIG. 2 is a side view showing a schematic configuration of the RF tag 100 according to this embodiment. The RF tag 100 includes a transparent substrate 11 having a first main surface and a second main surface, an antenna section 13 disposed on the first main surface of the transparent substrate 11, a current collector 12 electrically connected to the antenna section 13, a joint 121 disposed on the first main surface of the transparent substrate 11, and a semiconductor element 14 electrically joined to the joint 121 on the joint 121. The semiconductor element 14 is joined to the joint 121 via a conductive adhesive layer 15. The current collector 12 is electrically connected to the antenna 13, and refers to a portion that collects electricity generated by the antenna section 13 in response to a predetermined frequency toward the semiconductor element 14. The joint 121 refers to a portion of the current collector 12 that is joined to the semiconductor element 14. Hereinafter, there is no need to distinguish between the current collecting part 12 and its joint 121, and when referring to both, it may be written as "current collecting part 12 (joint 121)." In addition, even if it is simply written as "current collecting part 12," it does not mean any part of the current collecting part 12 other than the joint 121.

Figure 3 is an enlarged view of the S1a portion of Figure 1, showing the schematic configuration of the current collecting part 12, the joint 121, and the antenna part 13. As shown in Figure 3, the loop-type current collecting part 12 has a joint 121 where the tips of the loops face each other. The joint 121 is the tip of the current collecting part 12, and is where it is joined to the semiconductor element 14.

In this embodiment, the transparent antenna has a transparent substrate 11 having a first main surface and a second main surface, an antenna section 13 disposed on the first main surface of the transparent substrate 11, and a joint section 121 disposed on the first main surface of the transparent substrate 11.

<Semiconductor element>
The semiconductor element 14 is not particularly limited, but may be an integrated circuit such as a memory element. Any known semiconductor element may be used as the semiconductor element 14 depending on the application of the RF tag 100. The configuration of the semiconductor element 14 is not particularly limited, but may include functional units such as a memory unit, a power supply rectifier, a receiver, a controller, and a transmitter.

<Antenna section>
FIG. 4 is an enlarged view of the S1 portion of FIG. 3 showing the first pattern 131 constituting the antenna unit 13. The antenna unit 13 has the first pattern 131 and an opening 132. The first pattern 131 has a conductive thin line having a line width of 0.25 μm or more and 5.0 μm or less. By having the conductive thin line of this line width, the conductive thin line in the first pattern 131 cannot be seen. The outer edge shape of the first pattern 131 is designed so that the antenna unit 13 responds to a predetermined frequency. The conductive thin lines constituting the first pattern 131 are electrically conductive to each other within the region of the antenna unit 13. The first pattern 131 is, for example, a grid made of conductive thin lines. The unit shape of the grid is not particularly limited, but examples thereof include a triangle, a rectangle, and a hexagon. FIG. 4 shows a grid whose unit shape is a rectangle. FIG. 5 is a schematic diagram showing another form of the first pattern 131. In this alternative embodiment, the grid has unit shapes that are hexagons.

The conductive thin wire is preferably a metal thin wire. The metal is not particularly limited, but examples include gold, silver, copper, and aluminum. Among these, silver or copper is preferred, and copper is more preferred.

(Line width W ₁ of first pattern)
The line width _W1 of the conductive thin line constituting the first pattern is preferably 0.25 μm or more and 5.0 μm or less, more preferably 0.5 μm or more and 4.0 μm or less, and even more preferably 1.0 μm or more and 3.0 μm or less. By setting the line width _W1 of the conductive thin line in this range, the conductive thin line constituting the first pattern becomes invisible, and the visibility of the antenna part can be reduced. The line width _W1 in this embodiment refers to the line width of the conductive thin line when the conductive thin line is projected onto the surface of the transparent substrate 11 from the surface side on which the first pattern 131 of the transparent substrate 11 is arranged.

(Thickness _H1 )
The thickness _H1 of the conductive thin wire constituting the first conductive pattern is preferably 10 nm or more and 1,000 nm or less, more preferably 50 nm or more, and even more preferably 75 nm or more. When the thickness _H1 of the conductive thin wire is 10 nm or more, the conductivity tends to be further improved. On the other hand, when the thickness _H1 of the conductive thin wire is 1,000 nm or less, the visibility is suppressed at a wide viewing angle.

(aspect ratio)
The aspect ratio ( _W1 / _H1 ) represented by the thickness _H1 of the conductive thin line relative to the line width _W1 of the conductive thin line is preferably 0.05 or more and 1.00 or less. The lower limit of the aspect ratio is more preferably 0.08 or more, and even more preferably 0.10 or more. By having an aspect ratio of 0.05 or more, there is a tendency that the conductivity can be further improved without decreasing the transmittance.

(Pitch _P1 )
The pitch P ₁ of the conductive pattern 131 is preferably 5 μm or more, more preferably 50 μm or more, and even more preferably 100 μm or more. When the pitch P ₁ of the conductive pattern 131 is 5 μm or more, good transmittance can be obtained. In addition, the pitch P ₁ of the conductive pattern 131 is preferably 1,000 μm or less, more preferably 500 μm or less, and even more preferably 250 μm or less. When the pitch P ₁ of the conductive pattern 131 is 1,000 μm or less, the conductivity tends to be further improved. In addition, when the conductive pattern 131 is a square grid pattern, the pitch P ₁ of the conductive pattern 131 with a line width of 1 μm can be set to 200 μm to achieve an aperture ratio of 99%. In addition, the pitch P ₁ means the sum of the line width W ₁ and the distance between the conductive thin lines.

(Occupied area ratio _A1 )
The occupied area ratio _A1 is preferably 0.5% or more, more preferably 1.0% or more, and even more preferably 2% or more. By making the occupied area ratio _A1 equal to or more than this value, the conductivity of the antenna part tends to be further improved. In addition, the occupied area ratio _A1 is preferably 10% or less, more preferably 7% or less. By making the occupied area ratio _A1 equal to or less than this value, the visible light transmittance of the transparent antenna tends to be further improved.

The "occupancy rate" of the pattern can be calculated by the following formula for the region on the transparent substrate where the first pattern is formed.
Occupancy rate (%)=(area occupied by first pattern/area of region of transparent substrate where first pattern is formed)×100

The opening width _W2 of the opening 132 is preferably 50 μm or more, more preferably 60 μm or more, and even more preferably 70 μm or more. By setting it in this range, the visibility of the antenna part 13 can be further suppressed. The opening width _W2 of the opening 132 is preferably 500 μm or less, more preferably 300 μm or less, and even more preferably 100 μm or less. The electrical resistance of the antenna part 13 can be reduced, and the antenna function can be improved. The "opening width" means the width of the short side of the opening. In addition, when the opening is a square, it is the width of one side.

(Visible light transmittance _T1 of antenna part)
The visible light transmittance T ₁ of the antenna portion 13 is preferably 80% or more and 99.0% or less, more preferably 85% or more and 95% or less. The visible light transmittance can be measured by calculating the transmittance in the range of visible light (360 to 830 nm) in accordance with the total light transmittance of JIS K 7361-1:1997. When the visible light transmittance T ₁ is 80% or more, the visibility of the antenna portion can be further suppressed, and when it is 85% or more, the transmittance difference with the transparent substrate is small, and the antenna portion becomes difficult to see. In addition, when the visible light transmittance T ₁ is 99% or less, it is possible to maintain the conductivity due to the pattern of the antenna portion, and when it is 95% or less, it is easy to ensure good conductivity, which is preferable for industrial production.

The visible light transmittance T ₁ of the antenna portion 13 tends to be improved by reducing the line width of the first pattern and/or improving the aperture ratio.

(Surface resistivity of antenna part)
The surface resistivity of the antenna portion 13 is preferably 0.1 Ω/sq or more and 1,000 Ω/sq or less, more preferably 0.1 Ω/sq or more and 500 Ω/sq or less, even more preferably 0.1 Ω/sq or more and 300 Ω/sq or less, even more preferably 0.1 Ω/sq or more and 200 Ω/sq or less, even more preferably 0.1 Ω/sq or more and 100 Ω/sq or less, even more preferably 0.1 Ω/sq or more and 20 Ω/sq or less, and even more preferably 0.1 Ω/sq or more and 10 Ω/sq or less. The lower the surface resistivity, the more the power loss tends to be suppressed, and the sensitivity as an antenna can be increased.

Regarding the method of measuring the sheet resistivity, first, a portion of the antenna part of the transparent antenna, in which the first pattern 131 is disposed over the entire surface, is cut out in a rectangular shape to obtain a measurement sample. From the obtained measurement sample, the sheet resistivity R _s (Ω/sq) can be measured by a four-terminal method in accordance with JIS K 7194:1994. An example of a resistivity meter used to measure the sheet resistivity is "Loresta GP" (product name, manufactured by Mitsubishi Chemical Corporation).

The surface resistivity tends to decrease as the aspect ratio (thickness) increases, even for the same occupied area ratio of the conductive thin wire. It can also be adjusted by selecting the type of metal material that makes up the conductive thin wire.

(Haze on antenna part)
The haze of the antenna portion 13 is preferably 0.01% or more and 5.00% or less. The upper limit of the haze is more preferably 4.00% or less, and even more preferably 3.00% or less. If the upper limit of the haze is 5.00% or less, the clouding of the conductive film against visible light can be sufficiently reduced. The haze in this specification can be measured in accordance with the haze of JIS K 7136:2000.

<Current collecting section>
1, the current collecting part 12 may have a loop shape. The current collecting part 121 is preferably configured by a third conductive pattern having a line width of 0.25 μm or more and 5.0 μm or less. Here, the third conductive pattern in this embodiment has a similar configuration to the second conductive pattern 1211 described later, and therefore a detailed description thereof will be omitted.

<Joint>
1, the joint 121 may have a loop shape to facilitate connection with the antenna section 13. The semiconductor element 14 is connected to the joint 121 of the RF tag 100 according to this embodiment by an anisotropic conductive adhesive. The anisotropic conductive adhesive constitutes the conductive adhesive layer 16. The anisotropic conductive adhesive will be described in detail later.

(Visible light transmittance _T2 of joint)
The visible light transmittance _T2 of the joint 121 is 30% or more and 80% or less, and the visible light transmittance _T2 has a value smaller than the visible light transmittance _T1 of the antenna portion 13. By setting it in this range, it is possible to provide an RF tag that has good electrical connection with the semiconductor element and excellent invisibility of the joint with the semiconductor element from the back surface. The visible light transmittance _T2 of the joint 121 is preferably 75% or less, more preferably 70% or less. The visible light transmittance _T2 of the joint 121 is preferably 40% or more, more preferably 45% or more. The visible light transmittance can be measured by calculating the transmittance in the range of visible light (360 to 830 nm) in accordance with the total light transmittance of JIS K 7361-1:1997.

The visible light transmittance T ₂ of the bonding portion 121 can be set within the above range by adjusting the wiring density of the second conductive pattern 1211 .

The difference ( _T1 - _T2 ) between the visible light transmittance _T1 and the visible light transmittance _T2 is preferably 45% or more and 60% or less, more preferably 50% or more and 57% or less, and even more preferably 53% or more and 55% or less. By setting the difference ( _T1 - _T2 ) in this range, the electrical connection between the antenna portion and the semiconductor element can be further improved.

Figure 6 is an enlarged view of part S2 in Figure 3, showing the second conductive pattern 1211 constituting the joint 121. The joint 121 has the second conductive pattern 1211 and an opening 1212. The conductive thin wires constituting the second conductive pattern 1211 are preferably electrically conductive to each other within the region of the antenna section 13. The second conductive pattern 1211 is, for example, a grid composed of conductive thin wires. The unit shape of the grid is not particularly limited, but examples include a triangle, a rectangle, and a hexagon.

The conductive thin wire is preferably a metal thin wire. The metal is not particularly limited, but examples include gold, silver, copper, and aluminum. Among these, silver or copper is preferred, and copper is more preferred.

(Line width W ₃ of second conductive pattern)
The line width _W3 of the conductive thin line constituting the second conductive pattern is preferably 0.25 μm or more and 5.0 μm or less, more preferably 0.5 μm or more and 4.0 μm or less, and even more preferably 1.0 μm or more and 3.0 μm or less. By setting the line width _W3 of the conductive thin line within this range, the conductive thin line constituting the second conductive pattern becomes invisible, and the visibility of the bonding portion 121 can be reduced. The line width _W3 in this embodiment refers to the line width of the conductive thin line when the conductive thin line is projected onto the surface of the transparent substrate 11 from the surface side on which the second conductive pattern 1211 of the transparent substrate 11 is arranged.

(Thickness _H2 )
The thickness _H2 of the conductive thin line constituting the second conductive pattern is preferably 10 nm or more and 1,000 nm or less, more preferably 50 nm or more, and even more preferably 75 nm or more. When the thickness _H1 of the conductive thin line is 10 nm or more, the conductivity tends to be further improved. On the other hand, when the thickness _H2 of the conductive thin line is 1,000 nm or less, the visibility is suppressed at a wide viewing angle.

(aspect ratio)
The aspect ratio ( _W3 / _H2 ) represented by the thickness _H2 of the conductive thin line relative to the line width _W3 of the conductive thin line is preferably 0.05 or more and 1.00 or less. The lower limit of the aspect ratio is more preferably 0.08 or more, and even more preferably 0.10 or more. By having an aspect ratio of 0.05 or more, there is a tendency that the conductivity can be further improved without decreasing the transmittance.

(Pitch _P2 )
The pitch _P2 of the second conductive pattern 1211 is preferably 1.0 μm or more, more preferably 1.2 μm or more. By having the pitch _P2 of the second conductive pattern 1211 be 1.0 μm or more, it is possible to obtain good transmittance while maintaining the conductivity with the ACP. In addition, the pitch _P2 of the second conductive pattern 1211 is preferably 7.0 μm or less, more preferably 4.0 μm or less. By having the pitch _P2 of the second conductive pattern 1211 be 7.0 μm or less, there is a tendency that the conductivity can be further improved. Note that the pitch _P2 means the sum of the line width _W3 and the distance between the conductive thin lines.

(Occupied area ratio _A2 )
The occupancy area ratio _A2 per unit area of the second conductive pattern 1211 formed in the bonding portion 121 is preferably larger than the occupancy area ratio _A1 per unit area of the first conductive pattern 131 formed in the antenna portion 13 described later. This relationship makes it possible to improve the electrical connection with the semiconductor element while increasing the visible light transmittance of the antenna portion 13.

The occupied area ratio _A2 is preferably 30% or more, more preferably 50% or more, even more preferably 60% or more, and even more preferably 70% or more. By making the occupied area ratio _A2 equal to or greater than this value, the electrical connection with the semiconductor element tends to be improved. In addition, the occupied area ratio _A2 is preferably 80% or less, more preferably 75% or less. By making the occupied area ratio _A2 equal to or less than this value, the invisibility of the connection with the semiconductor element from the back surface tends to be further improved.

When the bonding portion 121 and the semiconductor element 14 are electrically bonded by conductive particles, the opening 1212 preferably has an opening width _W4 narrower than the average particle diameter of the conductive particles. The "opening width" means the width in the short direction of the opening. When the opening is a square, it is the width of either side. When the width of the opening 1212 in at least the short direction is narrower than the average particle diameter of the conductive particles, the conductive particles come into contact with the conductive thin wires that make up the conductive pattern 1211, and the electrical bond between the bonding portion 121 and the semiconductor element 14 is improved.

It is preferable that the opening width _W4 of the opening in the bonding portion 121 where the second conductive pattern is not formed is smaller than the opening width _W2 of the opening in the antenna portion 13 where the first conductive pattern is not formed. This improves the electrical connection between the bonding portion 121 and the semiconductor element 14.

The opening width _W4 of the opening 1212 is preferably 0.75 μm or more, and more preferably 0.90 μm or more. By setting it in this range, the visibility of the joint can be further suppressed. The opening width _W4 of the opening 1212 is preferably 10 μm or less, and more preferably 6.0 μm or less. The electrical connection between the joint 121 and the semiconductor element 14 can be made better.

Figure 7 is a schematic diagram showing another embodiment of the antenna section and joint section. As shown in Figure 7, the antenna section 13 may be divided into two or more regions, and a joint section 121 may be provided in the center of the antenna section 13.

Figure 8 is an enlarged view of the S1b portion of Figure 7, showing the schematic configuration of the current collecting part 12, the joint 121, and the antenna part 13. In Figure 8, the current collecting part 12 has two or more joints 121 with opposing tips. Note that, although Figure 8 shows a trapezoidal current collecting part 12, the shape of the current collecting part 12 is not limited to this. As an example, it is preferable that the current collecting part 12 in Figure 8 has an area in plan view that is equal to or several times the projected area of the semiconductor element, and that when the semiconductor element 14 is joined to the joint 121, the current collecting part 12 is almost completely covered. In this case, it can be said that the current collecting part 12 is essentially composed of only the joint 121.

<Anisotropic conductive adhesive>
The form of the anisotropic conductive adhesive is not particularly limited, and it may be, for example, in any of a film, a paste, or a liquid form.

The anisotropic conductive adhesive contains conductive particles. The conductive particles are sandwiched between the metal wirings to be joined, so that the connection surface is electrically connected in the direction perpendicular to the connection surface. On the other hand, the conductive particles are present in a floating state in the binder resin on the surface direction side of the connection surface, so that they are not electrically connected. The RF tag 100 according to this embodiment has the joint 121, so that even when the anisotropic conductive adhesive is used, the electrical connection can be performed well. In other words, when the line width of the conductive thin wire is narrowed and the area ratio of the opening increases, the probability that the conductive fine particles are present in the opening increases, and the possibility of poor electrical connection increases. By setting the visible light transmittance _T2 of the joint to 40% or more and 70% or less, and setting the visible light transmittance _T2 to a value smaller than the visible light transmittance _T1 of the antenna portion, the probability that the conductive fine particles are present at the position of the conductive wiring increases, and the probability of good electrical connection increases.

The anisotropic conductive adhesive may contain conductive particles. The conductive particles are not particularly limited, but examples thereof include resin particles with a metal-coated surface, metal particles, and alloy particles. The metals are not particularly limited, but examples thereof include tin, bismuth, copper, silver, antimony, indium, zinc, and titanium. The alloys are not particularly limited, but examples thereof include alloys containing two or more of the above-mentioned metals.

The average particle diameter D of the conductive particles is preferably 1.0 μm or more and 100 μm or less, more preferably 2.0 μm or more and 60 μm or less, and even more preferably 3.0 μm or more and 30 μm or less. The average particle diameter of the conductive particles is measured by a dynamic light scattering particle diameter measuring device, and is the particle diameter (median diameter) at which the cumulative volume frequency in the volume fraction is 50% calculated from the minimum particle diameter. The particle diameter measuring device may be a particle diameter measuring device using a laser diffraction method, and is appropriately selected depending on the average particle diameter of the conductive particles. Even in the particle diameter measuring device using the laser diffraction method, the average particle diameter of the conductive particles is the particle diameter (median diameter) at which the cumulative volume frequency in the volume fraction is 50% calculated from the minimum particle diameter.

The content of the conductive particles is preferably 15% by mass or more and 40% by mass or less, more preferably 17% by mass or more and 30% by mass or less, and even more preferably 18% by mass or more and 25% by mass or less, based on the total amount of the anisotropic conductive adhesive.

The anisotropic conductive adhesive may contain a binder resin. The binder resin is not particularly limited, but examples thereof include polyester resin, polyurethane resin, polyester urethane resin, polyether resin, polyamide resin, polyamideimide resin, polyimide resin, polyvinyl butyral resin, polyvinyl formal resin, phenoxy resin, polyhydroxy polyether resin, acrylic resin, polystyrene resin, butadiene resin, acrylonitrile-butadiene copolymer, acrylonitrile-butadiene-styrene copolymer, styrene-butadiene copolymer, and acrylic acid copolymer. These thermoplastic resins may be saturated or unsaturated.

The content of the binder resin is preferably 8% by mass or more and 35% by mass or less, more preferably 10% by mass or more and 30% by mass or less, and even more preferably 12% by mass or more and 25% by mass or less, based on the total amount of the anisotropic conductive adhesive.

The anisotropic conductive adhesive may contain an addition polymerizable resin having an unsaturated double bond. The addition polymerizable resin is preferably a resin having two or more unsaturated double bonds in one molecule. The addition polymerizable resin is, for example, an addition polymerizable resin having a weight average molecular weight of 800 or more and having two or more (meth)acryloyl groups. The addition polymerizable resin is not particularly limited, but examples thereof include urethane acrylate resin, epoxy acrylate resin, and silicon acrylate resin. These may be used alone or in combination of two or more. The weight average molecular weight of the addition polymerizable resin is preferably 1000 or more and 10000 or less, more preferably 1200 or more and 5000 or less.

The content of the addition polymerizable resin in the anisotropic conductive adhesive is preferably 5% by mass or more and 60% by mass or less, more preferably 10% by mass or more and 50% by mass or less, and even more preferably 15% by mass or more and 40% by mass or less.

The anisotropic conductive adhesive may contain a low melting point monomer having an unsaturated double bond. From the viewpoint of further improving the adhesive strength and coatability of the resulting anisotropic conductive adhesive, it is preferable that the anisotropic conductive adhesive contains both an addition polymerizable resin and a low melting point monomer. These may be used alone or in combination of two or more. These may be used alone or in combination of two or more. The low melting point monomer is a monomer that has one or more unsaturated double bonds in one molecule and is liquid at 25°C. The low melting point monomer is not particularly limited, but examples thereof include 2-hydroxy-3-phenoxypropyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, methoxydiethylene glycol (meth)acrylate, methoxytriethylene glycol (meth)acrylate, 2-ethylhexyl (meth)acrylate, isodecyl (meth)acrylate, n-lauryl (meth)acrylate, tridecyl (meth)acrylate, n-stearyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, isobornyl (meth)acrylate, and (meth)acryloylmorpholine. These may be used alone or in combination of two or more.

The content of the low melting point monomer is preferably 15% by mass or more and 55% by mass or less, more preferably 20% by mass or more and 50% by mass or less, and even more preferably 25% by mass or more and 40% by mass or less, based on the total amount of the anisotropic conductive adhesive.

The anisotropic conductive adhesive may contain a polymerization initiator. The polymerization initiator is not particularly limited, but examples thereof include thermal polymerization initiators and photopolymerization initiators. Examples of the thermal polymerization initiator include organic peroxides such as ketone peroxides, diacyl peroxides, hydroperoxides, dialkyl peroxides, peroxyketals, alkyl peresters, and percarbonates. Examples of the photopolymerization initiator include oxime initiators, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one, 4-(2- Examples of the polymerization initiator include (hydroxyethoxy)phenyl-2-(hydroxy-2-propyl) ketone, benzophenone, p-phenylbenzophenone, 4,4'-diethylaminobenzophenone, dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tertiary butylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, benzyl dimethyl ketal, acetophenone dimethyl ketal, and p-dimethylaminobenzoic acid ethyl ester. These polymerization initiators may be used alone or in combination of two or more.

The content of the polymerization initiator is preferably 0.1% by mass or more and 7% by mass or less, more preferably 0.5% by mass or more and 5% by mass or less, and even more preferably 1% by mass or more and 4% by mass or less, based on the total amount of the anisotropic conductive adhesive.

The anisotropic conductive adhesive may also contain other ingredients such as thixotropic agents and organic fillers.

By applying an anisotropic conductive adhesive to the joint and then thermocompressing the semiconductor element, the semiconductor element and the joint can be electrically joined.

<Formula (1)>
It is preferable that the conductive particles have an average particle size D of 3 μm or more and 10 μm or less, and that the average particle size D, the opening width W ₄ , and the thickness H ₂ satisfy the following formula (1).
(W ₄ ) ² /4 < (D/2) ² - (D/2 - H ₂ ) ² (1)
By satisfying the formula (1), the electrical connection with the semiconductor element can be made more reliable.

<Transparent substrate>
The term "transparent" in the context of a transparent substrate means that the visible light transmittance is preferably 80% or more, more preferably 90% or more, and even more preferably 95% or more. The visible light transmittance can be measured in accordance with JIS K 7361-1:1997.

The material of the transparent substrate is not particularly limited, but examples thereof include transparent inorganic substrates such as glass; transparent organic substrates such as acrylic acid esters, methacrylic acid esters, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyarylate, polyvinyl chloride, polyethylene, polypropylene, polystyrene, nylon, aromatic polyamide, polyether ether ketone, polysulfone, polyether sulfone, polyimide, and polyether imide. Among these, polyethylene terephthalate, polyimide, or polyethylene naphthalate is preferred. By using polyethylene terephthalate, the productivity (cost reduction effect) for manufacturing the conductive film is more excellent, and the adhesion between the transparent substrate and the thin metal wire tends to be more improved. In addition, by using polyimide, the heat resistance of the conductive film tends to be more improved. Furthermore, by using polyethylene naphthalate, the adhesion between the transparent substrate and the thin metal wire tends to be more excellent.

The transparent substrate may be made of one material or may be made of two or more laminated materials. In addition, when the transparent substrate is a multilayer body made of two or more laminated materials, the transparent substrate may be made of organic substrates or inorganic substrates laminated together, or an organic substrate and an inorganic substrate laminated together.

The thickness of the transparent substrate is preferably 5 μm or more and 500 μm or less, and more preferably 10 μm or more and 100 μm or less.

<Middle class>
The RF tag 100 of this embodiment may have an intermediate layer between the transparent substrate and the conductive portion. The intermediate layer can contribute to improving the adhesion between the transparent substrate and the thin metal wire of the conductive portion.

The components contained in the intermediate layer are not particularly limited, but examples thereof include silicon compounds (e.g., (poly)silanes, (poly)silazanes, (poly)silthians, (poly)siloxanes, silicon, silicon carbide, silicon oxide, silicon nitride, silicon chloride, silicate salts, zeolites, silicides, etc.), aluminum compounds (e.g., aluminum oxide, etc.), magnesium compounds (e.g., magnesium fluoride), etc. Among these, at least one selected from the group consisting of silicon oxide, silicon nitride, aluminum oxide, and magnesium fluoride is preferable. By using such components, the transparency and durability of the conductive film tend to be further improved, and the productivity (cost reduction effect) for manufacturing the conductive film is more excellent. The intermediate layer can be formed by a gas phase film formation method such as PVD or CVD, or a method of applying and drying an intermediate forming composition in which the components contained in the intermediate layer are dispersed in a dispersion medium. The intermediate forming composition may contain a dispersant, a surfactant, a binder, etc., as necessary.

The thickness of the intermediate layer is preferably 0.01 μm or more and 500 μm or less, more preferably 0.05 μm or more and 300 μm or less, and even more preferably 0.10 μm or more and 200 μm or less. When the thickness of the intermediate layer is 0.01 μm or more, adhesion between the intermediate layer and the thin metal wire is expressed, and when the thickness of the intermediate layer is 500 μm or less, the flexibility of the transparent substrate can be ensured.

By laminating the intermediate layer on the transparent substrate, when the metal components in the ink are sintered using a baking method such as plasma, etching of the transparent substrate in areas that are not covered by the thin metal line pattern can be prevented.

Furthermore, it is preferable that this intermediate layer has an antistatic function to prevent breakage of the metal thin line pattern due to static electricity. In order for the intermediate layer to have an antistatic function, it is preferable that the intermediate layer contains at least one of a conductive inorganic oxide and a conductive organic compound. Examples of conductive organic compounds include conductive organosilane compounds, aliphatic conjugated polyacetylene, aromatic conjugated poly(paraphenylene), heterocyclic conjugated polypyrrole, etc. Among these, conductive organosilane compounds are preferable.

The volume resistivity of the intermediate layer is preferably 100 Ωcm or more and 100,000 Ωcm or less, more preferably 1000 Ωcm or more and 10,000 Ωcm or less, and even more preferably 2000 Ωcm or more and 8000 Ωcm or less. When the volume resistivity of the intermediate layer is 100,000 Ωcm or less, an antistatic function can be exhibited. Furthermore, when the volume resistivity of the intermediate layer is 100 Ωcm or more, it can be suitably used for applications such as touch panels in which electrical conduction between metal thin line patterns is not preferable. The volume resistivity can be adjusted by the content of components that exhibit an antistatic function, such as conductive inorganic oxides and conductive organic compounds, in the intermediate layer. For example, when the intermediate layer contains silicon oxide (volume resistivity 10 ¹⁴ Ω·cm or more) with high plasma resistance and an organic silane compound, which is a conductive organic compound, the volume resistivity can be reduced by increasing the content of the conductive organic silane compound. On the other hand, the volume resistivity increases by increasing the content of silicon oxide, but the film has high plasma resistance, so it can be made into a thin film and does not impair optical properties.

[Method of manufacturing transparent antenna]
The transparent antenna can be obtained, for example, by forming the above-mentioned transparent antenna pattern on a transparent substrate. The method for producing the transparent antenna is not particularly limited, but may include, for example, a method having a pattern forming step of forming a pattern on a transparent substrate using an ink containing a metal component, and a firing step of firing the pattern to form a metal thin wire. In addition, the method for producing the transparent antenna of this embodiment may include an intermediate layer forming step of forming an intermediate layer on the surface of the transparent substrate prior to the pattern forming step.

(Intermediate layer forming process)
The intermediate layer forming step is a step of forming an intermediate layer on the surface of a transparent substrate. The method of forming the intermediate layer is not particularly limited, but examples thereof include a method of forming a vapor deposition film on the surface of a transparent substrate by a gas phase film forming method such as physical vapor deposition (PVD) or chemical vapor deposition (CVD); and a method of forming a coating film by applying a composition for forming an intermediate layer on the surface of a transparent substrate and drying it.

The composition for forming the intermediate layer contains the components exemplified as the components contained in the intermediate layer or their precursors, and a solvent, and may contain surfactants, dispersants, binders, etc. as necessary.

(Pattern Forming Process)
The pattern forming process is a process of forming a pattern using an ink containing a metal component. The pattern forming process is not particularly limited as long as it is a plate-based printing method using a plate having grooves of a desired metal thin line pattern, but includes, for example, a process of coating the surface of a transfer medium with ink, a process of placing the ink-coated transfer medium surface opposite the convex surface of a relief plate and pressing and contacting the surface to transfer the ink on the transfer medium surface to the convex surface of the relief plate, and a process of placing the ink-coated transfer medium surface opposite the surface of a transparent substrate and pressing and contacting the surface to transfer the ink remaining on the transfer medium surface to the surface of the transparent substrate. In addition, when an intermediate layer is formed on the transparent substrate, the ink is transferred to the surface of the intermediate layer.

Ink
The ink used in the pattern forming process contains a metal component and a solvent, and may contain a surfactant, a dispersant, a reducing agent, etc., as necessary. The metal component may be contained in the ink as metal particles, or may be contained in the ink as a metal complex. The metal element species contained in the metal component referred to here is not particularly limited, but may include, for example, gold, silver, copper, and aluminum. Among these, silver or copper is preferred, and copper is more preferred.

When metal particles are used, the average primary particle size is preferably 100 nm or less, more preferably 50 nm or less, and even more preferably 30 nm or less. The lower limit of the average primary particle size of the metal particles is not particularly limited, but may be 1 nm or more. By making the average primary particle size of the metal particles 100 nm or less, the width of the obtained metal thin wire can be made thinner. In this embodiment, the "average primary particle size" refers to the particle size of each individual metal particle (so-called primary particle), and is distinguished from the average secondary particle size, which is the particle size of an aggregate (so-called secondary particle) formed by gathering multiple metal particles.

The metal particles may be metal oxides such as copper oxide, metal compounds, or core/shell particles in which the core is copper and the shell is copper oxide. The form of the metal particles can be appropriately determined from the viewpoints of dispersibility and sinterability.

The content of metal particles in the ink is preferably 1% by mass or more and 40% by mass or less, more preferably 5% by mass or more and 35% by mass or less, and even more preferably 10% by mass or more and 35% by mass or less, based on the total mass of the ink composition. If the content of metal particles in the ink is 1% by mass or more based on the total mass of the ink composition, a conductive metal thin line pattern can be obtained, and if it is 40% by mass or less, the ink can be printed in the shape of a metal thin line pattern.

The surfactant is not particularly limited, but examples include silicone-based surfactants and fluorine-based surfactants. By using such surfactants, the coatability of the ink on the transfer medium (blanket) and the smoothness of the coated ink are improved, and a more uniform coating tends to be obtained. It is preferable that the surfactant is capable of dispersing metal components and is configured so as not to remain when fired.

The content of the surfactant in the ink is preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.1% by mass or more and 5% by mass or less, and even more preferably 0.5% by mass or more and 2% by mass or less, based on the total mass of the ink composition. If the content of the surfactant in the ink is 0.01% by mass or more based on the total mass of the ink composition, the coatability of the ink and the smoothness of the coated ink can be improved, and if it is 10% by mass or less, a thin metal line pattern with low resistance can be obtained.

The dispersant is not particularly limited, but examples thereof include dispersants that form non-covalent bonds or interactions with metal components, and dispersants that form covalent bonds with metal components. Examples of functional groups that form non-covalent bonds or interactions include dispersants that have phosphate groups. Use of such dispersants tends to further improve the dispersibility of metal components.

The content of the dispersant in the ink is preferably 0.1% by mass or more and 30% by mass or less, more preferably 1% by mass or more and 20% by mass or less, and even more preferably 2% by mass or more and 10% by mass or less, based on the total mass of the ink composition. If the content of the dispersant in the ink is 0.1% by mass or more based on the total mass of the ink composition, an ink in which metal particles are dispersed can be obtained, and if it is 30% by mass or less, a metal thin line pattern with low resistance can be obtained.

Further, examples of the solvent include alcohol-based solvents such as monoalcohols and polyhydric alcohols; alkyl ether-based solvents; hydrocarbon-based solvents; ketone-based solvents; ester-based solvents; and the like. These may be used alone or in combination of one or more. For example, a monoalcohol having 10 or less carbon atoms may be used in combination with a polyhydric alcohol having 10 or less carbon atoms. By using such a solvent, the coating property of the ink on the transfer medium (blanket), the transfer property of the ink from the transfer medium to the relief plate, the transfer property of the ink from the transfer medium to the transparent substrate, and the dispersibility of the metal components tend to be improved. Note that the solvent is preferably configured to be capable of dispersing the metal components and to be less likely to remain after firing.

The content of the solvent in the ink is the remainder of the above-mentioned components such as metal particles, surfactant, and dispersant, and is, for example, preferably 50% by mass or more and 99% by mass or less, more preferably 60% by mass or more and 90% by mass or less, and even more preferably 70% by mass or more and 80% by mass or less, based on the total mass of the ink composition. If the content of the solvent in the ink is 50% by mass or more based on the total mass of the ink composition, the ink can be printed in the form of a thin metal line pattern, and if it is 99% by mass or less, a conductive thin metal line pattern can be obtained.

The amount of the above components in the ink can be adjusted appropriately from the viewpoint of adjusting the amount of voids in the metal wires by the decomposition gases etc. generated during firing.

(Firing process)
The firing process is a process of firing the pattern to form fine metal wires, and thus a conductive part having a fine metal wire pattern similar to the pattern applied with the ink can be obtained. The firing process is not particularly limited as long as the metal components are fused to form a metal component sintered film. For example, firing may be performed in a firing furnace, or may be performed using plasma, a heating catalyst, ultraviolet light, vacuum ultraviolet light, an electron beam, infrared lamp annealing, flash lamp annealing, a laser, or the like. When the resulting sintered film is easily oxidized, it is preferable to perform firing in a non-oxidizing atmosphere. In addition, when metal oxides and the like are difficult to reduce only by the reducing agent that may be contained in the ink, it is preferable to perform firing in a reducing atmosphere.

A non-oxidizing atmosphere is an atmosphere that does not contain oxidizing gases such as oxygen, and there are inert atmospheres and reducing atmospheres. An inert atmosphere is, for example, an atmosphere filled with inert gases such as argon, helium, neon, and nitrogen. A reducing atmosphere refers to an atmosphere in which reducing gases such as hydrogen and carbon monoxide are present. The ink coating film (dispersion coating film) may be baked by filling the baking furnace with these gases and forming a closed system. The baking furnace may also be a flow system in which these gases are flowed while the coating film is baked. When the coating film is baked in a non-oxidizing atmosphere, it is preferable to once evacuate the baking furnace to remove the oxygen in the baking furnace and replace it with a non-oxidizing gas. The baking may be performed in a pressurized atmosphere or a reduced pressure atmosphere.

The baking temperature is not particularly limited, but is preferably 20°C to 400°C, more preferably 50°C to 300°C, and even more preferably 80°C to 200°C. A baking temperature of 400°C or less is preferable because it allows the use of a substrate with low heat resistance. Also, a baking temperature of 20°C or more is preferable because the formation of the sintered film proceeds sufficiently and the conductivity tends to be good. The obtained sintered film contains conductive components derived from metal components, and may also contain non-conductive components depending on the components used in the ink and the baking temperature.

Among these, from the viewpoint of adjusting the diffusion and aggregation of the metal components and thereby adjusting the amount of voids in the metal wire, it is preferable to use, for example, heat, plasma, electron beam or a light source as the energy during firing, and it is preferable to use flash lamp annealing. From the same viewpoint, the firing time is preferably 100 μsec to 50 msec, more preferably 800 μsec to 10 msec, or 1 msec to 2.4 msec. Note that, if necessary, firing may be performed using flash lamp annealing multiple times.

In addition to the above-mentioned viewpoints, it is more preferable to use a plasma baking method, since it can promote the fusion of metal components and obtain a conductive film with higher conductivity. From the same viewpoint, the plasma output is preferably 0.5 kW or more, more preferably 0.6 kW or more, and even more preferably 0.7 kW or more. There is no particular limit to the upper limit of the plasma output, and it is sufficient as long as it is within a range that does not damage the transparent substrate or intermediate layer used. In addition, the lower limit of the baking time depends on the plasma output, but from the viewpoint of productivity, the upper limit is preferably 1000 sec or less, and more preferably 600 sec or less. If necessary, plasma baking may be used multiple times.

An example of the operation of each functional unit and the RF tag 100 of this embodiment when it is a passive type will be described. First, the antenna unit 13 of the RF tag 100 receives radio waves from the reader/writer, and an electromotive force is generated by electromagnetic induction or the like. Then, this electromotive force activates the semiconductor element 14 of the RF tag 100. At that time, the power supply rectifier converts the AC input to the antenna unit 13 into DC and supplies power to the circuit of the semiconductor element 14. In parallel with this, the receiver demodulates the carrier wave received from the reader/writer into a signal sequence and sends the signal sequence to the control unit. The control unit reads/writes information to the memory unit and passes the information processing result as a signal sequence to the transmitter unit according to the signal sequence received from the receiver. Here, the memory unit stores various information such as product information according to the application of the RF tag. Finally, the transmitter modulates the signal sequence received from the control unit into a carrier wave and transmits it from the antenna unit 13. Then, the antenna of the reader/writer receives the carrier wave and performs information processing. In this embodiment, RFID refers to a system consisting of an RF tag and a reader/writer.

The frequency bands that can be used by the RF tag 100 of this embodiment are not particularly limited, but examples include LF band (medium wave band): 120 to 130 kHz, HF band (short wave band): 13.56 MHz, UHF band (ultra high frequency band): 900 MHz band, and microwave: 2.45 GHz band. The type of antenna unit 13 can be adjusted appropriately according to the frequency band to be used. For example, when using the HF band, a loop type antenna can be used, and when using the UHF band, a dipole type antenna can be used.

The transmission and reception methods that can be used by the RF tag 100 of this embodiment are not limited to the radio wave method described above, and may also include an electromagnetic coupling method in which high frequency waves are applied to coils on the transmitting and receiving sides, and information is transmitted through the mutual induction that occurs, or an electromagnetic induction method in which information is transmitted through a magnetic field generated near the antenna.

The present invention will be described in more detail below using examples and comparative examples. The present invention is not limited in any way by the following examples.

Example 1
Polyethylene terephthalate (PET) was used as a transparent substrate, and a composition containing silicon oxide nanoparticles and a conductive organosilane compound was applied to one side of the substrate and dried to form a 50 nm-thick intermediate layer containing silicon oxide. This was used as substrate A.

Next, 20 parts by mass of cuprous oxide nanoparticles with a particle diameter of 21 nm, 4 parts by mass of a dispersant (manufactured by BYK-Chemie, product name: Disperbyk-145), 1 part by mass of a surfactant (manufactured by Seimi Chemical, product name: S-611), and 75 parts by mass of ethanol were mixed and dispersed to prepare an ink containing 20% by mass of cuprous oxide nanoparticles.

Then, the ink was applied to the surface of the transfer medium, and the ink-applied transfer medium surface was opposed to a plate having grooves of a conductive pattern, and pressed and contacted to transfer a part of the ink on the transfer medium surface to the convex surface of the plate. After that, the transfer medium surface coated with the remaining ink was opposed to the substrate A, and pressed and contacted to transfer the ink of the conductive pattern having the desired shape of the antenna part and the joint part onto the substrate A. Next, the conductive pattern-shaped ink (dispersion coating film) was baked by flash lamp annealing in a room temperature environment using Pulseforge 1300 manufactured by NovaCentrix. The conductive pattern in the antenna portion was in the form of a square grid with a line width _W1 of 3.0 μm, an opening width _W2 of 60 μm, and a visible light transmittance _T1 of 84%, while the conductive pattern in the joint portion was in the form of a square grid with a line width _W3 of 1.0 μm, an opening width _W4 of 3.0 μm, and a visible light transmittance _T2 of 52%.
The antenna unit is a dipole antenna having two rectangular conductive patterns, each having a long side width of 49 mm and a short side width of 10 mm, as shown in Figure 7, which are arranged with their short sides facing each other at a distance of 2 mm from each other, and the gap between the joints formed between the two conductive patterns is 150 μm.

A semiconductor element was bonded to the bonding portion of the transparent antenna obtained as described above using an anisotropic conductive paste having conductive particles with an average particle size of 30 μm, to obtain an RF tag.
The radiation characteristics of the obtained RF tag were measured, and as a result, a communication distance of 1.3 m was obtained at 920 MHz, and antenna characteristics equivalent to those of a metal dipole antenna made of copper foil with the same external dimensions were obtained.

Example 2
An RF tag was obtained in the same manner as in Example 1, except that the conductive pattern at the joint was a square grid shape, with line width _W3 : 2.0 μm, opening width _W4 : 5.0 μm, and visible light transmittance _T2 of 47%.
The obtained RF tag achieved a communication distance of 1.3 m at 920 MHz, and exhibited antenna characteristics equivalent to a metal dipole antenna made of copper foil and having the same external dimensions.

Example 3
An RF tag was obtained in the same manner as in Example 1, except that the conductive pattern at the joint was a square grid shape, with line width _W3 : 2.0 μm, opening width _W4 : 8.0 μm, and visible light transmittance _T2 of 59%.
The obtained RF tag achieved a communication distance of 1.3 m at 920 MHz, and exhibited antenna characteristics equivalent to a metal dipole antenna made of copper foil and having the same external dimensions.

Example 4
An RF tag was obtained in the same manner as in Example 1, except that the conductive pattern at the joint was a square grid shape, with line width _W3 : 2.0 μm, opening width _W4 : 3.0 μm, and visible light transmittance _T2 : 33%.
The obtained RF tag achieved a communication distance of 1.3 m at 920 MHz, and exhibited antenna characteristics equivalent to a metal dipole antenna made of copper foil and having the same external dimensions.

Comparative Example 1
An RF tag was obtained in the same manner as in Example 1, except that the conductive pattern at the joint was a square grid shape, with line width _W3 : 1.0 μm, opening width _W4 : 60 μm, and visible light transmittance _T2 : 89%.
The RF tag thus obtained did not respond to communication at 920 MHz, and no antenna characteristics were obtained. It was presumed that the electrical continuity between the antenna section and the IC chip was insufficient.

Comparative Example 2
An RF tag was obtained in the same manner as in Example 1, except that the conductive pattern at the joint was a square grid shape, with line width _W3 : 5.0 μm, opening width _W4 : 2.0 μm, and visible light transmittance _T2 of 7.0%.
The obtained RF tag achieved a communication distance of 1.3 m at 920 MHz, and exhibited antenna characteristics equivalent to a metal dipole antenna made of copper foil and having the same external dimensions.
However, when observed from the backside, the chip joint was observed as a bright spot, and under magnification a metallic luster was clearly observed.

100... RF tag, 11... transparent substrate, 12... current collector, 121... joint, 13... antenna, 15... conductive adhesive layer, 131... first pattern, 1211... second pattern, 132, 1212... openings

Claims (7)

A transparent substrate;
An antenna portion disposed on the transparent base material;
a joint portion disposed on the transparent base material and electrically joined to the antenna portion;
a semiconductor element electrically connected to the joint portion by conductive particles on the joint portion;
the antenna portion is configured by a first conductive pattern having a line width of 0.25 μm or more and 5.0 μm or less,
the bonding portion is formed of a second conductive pattern having a line width of 0.25 μm or more and 5.0 μm or less,
The visible light transmittance _T2 of the joint is 30% or more and 80% or less, and
The visible light transmittance _T2 has a value smaller than the visible light transmittance _T1 of the antenna portion ,
The conductive particles have an average particle size D of 3 μm or more and 100 μm or less,
The average particle size D, the opening width W ₄ of the opening in the bonding portion where the second conductive pattern is not formed , and the thickness H ₂ of the conductive thin wire constituting the conductive pattern satisfy the following formula (1):
(W ₄ ) ² /4 < (D/2) ² - (D/2 - H ₂ ) ² (1)
RF tag. The opening width _W4 is 1.0 μm or more and 10 μm or less.
The RF tag according to claim 1. The opening width _W4 is smaller than an opening width _W2 of an opening in the antenna portion where the first conductive pattern is not formed,
The opening width _W2 is 60 μm or more and 300 μm or less.
The RF tag according to claim 1 or 2. an occupancy area ratio _A2 per unit area of the second conductive pattern formed in the bonding portion is greater than an occupancy area ratio _A1 per unit area of the first conductive pattern formed in the antenna portion;
The occupied area ratio _A2 is 30% or more and 80% or less,
The occupied area ratio _A1 is 0.5% or more and 10% or less.
The RF tag according to any one of claims 1 to 3. the bonding portion and the semiconductor element are electrically bonded by an anisotropic conductive adhesive containing the conductive particles;
The RF tag according to any one of claims 1 to 4 . The opening in the bonding portion where the second conductive pattern is not formed has an opening width _W4 narrower than the average particle diameter of the conductive particles.
The RF tag according to any one of claims 1 to 5 . A transparent substrate;
An antenna portion disposed on the transparent base material;
a joining portion disposed on the transparent base material and electrically joined to the antenna portion by conductive particles ;
the antenna portion is configured by a first conductive pattern having a line width of 0.25 μm or more and 5.0 μm or less,
the bonding portion is formed of a second conductive pattern having a line width of 0.25 μm or more and 5.0 μm or less,
The visible light transmittance _T2 of the joint is 30% or more and 80% or less, and
The visible light transmittance _T2 has a value smaller than the visible light transmittance _T1 of the antenna portion ,
The conductive particles have an average particle size D of 3 μm or more and 100 μm or less,
The average particle size D, the opening width W ₄ of the opening in the bonding portion where the second conductive pattern is not formed , and the thickness H ₂ of the conductive thin wire constituting the conductive pattern satisfy the following formula (1):
(W ₄ ) ² /4 < (D/2) ² - (D/2 - H ₂ ) ² (1)
Transparent antenna.