JP2000294897A - Circuit board, display device using the same and electronics - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the adhesive power of adhesion resin agasint a base board and to improve the electric connection reliability of a semiconductor chip and a wiring board in the circuit board of structure where the semiconductor chip is mounted on the base board through the use of adhesion resin. SOLUTION: In a circuit board, an input wiring 420a, an output wiring 420b and a dummy wiring layer 422 are formed on the IC chip mounting area of a base film 410 having insulating property and flexibility and an IC chip 450 is mounted and formed through an anisotropic conduction film where conductive particles 21 are dispersed in adhesion resin 19. The dummy wiring layer 422 is insulated from the input wiring 420a, the output wiring 420b and the electrodes 450a and 450b of the IC chip, and several opening parts 422a are installed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit board formed by mounting a semiconductor chip on a base substrate by flip-chip mounting, and a display device and an electronic apparatus using the circuit board.

[0002]

BACKGROUND OF THE INVENTION In recent years,
Electronic components, such as IC chips, are directly mounted on FPC (Flexible Printed Circuit) substrates because of their small size, thinness and lightness, adaptability to bendable structures, and realization of high productivity by roll-to-roll. Technology has come to be used. Moreover, with this technology, TA
Unlike the B (Tape Automated Bonding) technology, the inner lead is not required, so that the copper foil can be made thin, and the fine pitch of the wiring can be easily achieved.

FIG. 16 is a cross-sectional view showing a conventional structure when electronic components are mounted on an FPC board. As shown in this figure, the input electrode 450a of the IC chip 450 and the input wiring 420a formed in advance on the base film 410
Is electrically connected via the conductive particles 21 dispersed in the bonding resin 19, and similarly, the output electrode 450 b of the IC chip 450 and the output wiring 420 b formed in advance on the base film 410 are connected to the bonding resin. 19 are electrically connected to each other via conductive particles 21 dispersed therein.

However, since the base film 410, which is the base material of the FPC board, is generally made of an organic film such as PI (polyimide) through which moisture easily penetrates, the base film 410 is opposite to the mounting surface (the lower side in the drawing). ), The moisture that has permeated the base film 410 reaches the wiring forming surface of the IC chip 450, thereby reducing the reliability of the IC chip or causing light leakage due to light transmitted through the base film 410. There is a disadvantage that the performance of the IC chip is reduced. This drawback becomes more prominent when the base film 410 is made thinner.

[0005] Further, since polyimide or the like having low surface wettability is generally used for the base film 410 as the base material of the FPC board, the bonding strength of the adhesive resin is extremely low.

Further, due to the effects of differences in the thermal expansion coefficients of the base film 410, the IC chip 450, and the bonding resin 19, stress concentrates on the bonding interface over time, and the bonding strength further decreases. There is a problem that a connection failure between the electrode of the chip 410 and the wiring of the FPC board is likely to occur. In particular, when the base film is made of a flexible thin material such as polyimide, the infiltration of moisture from the base film side causes a further decrease in the adhesive strength, and the IC chip 4
The problem that connection failure between the electrode of No. 10 and the wiring of the FPC board easily occurs was even more remarkable.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to provide a circuit board having a structure in which a semiconductor chip is mounted on a base board by using an adhesive resin. An object of the present invention is to provide a circuit board that can solve any of the problems, and a display device and an electronic device using the same.

1) Improve the adhesive strength of the adhesive resin to the base substrate.

2) The reliability of electrical connection between the semiconductor chip and the wiring board is improved.

3) To prevent the performance and reliability of the semiconductor chip from deteriorating.

4) It is possible to reduce the penetration of moisture from the base substrate side to the bonding area.

[0012]

(1) A circuit board according to the present invention comprises: a base material having an insulating property; a wiring board having a plurality of board-side terminals provided on the base material; A semiconductor chip mounted on the wiring substrate, the semiconductor substrate being electrically connected to the substrate-side terminal, wherein the wiring substrate has an area where the semiconductor chip is mounted. And a dummy wiring layer insulated from the substrate-side terminals and the semiconductor-side terminals in a region inside the substrate-side terminals.

According to the present invention, at least a part of the moisture permeating through the base material is blocked by the dummy wiring layer from the surface opposite to the mounting surface of the semiconductor chip. Therefore, the possibility that the reliability of the substrate-side terminal or the semiconductor-side terminal in the region where the semiconductor chip is mounted on the wiring substrate is reduced by moisture is reduced. When a semiconductor chip is mounted on a wiring board, the board-side terminals, the semiconductor-side terminals, and the wiring pattern often have a narrow pitch in the mounting area. Outbreaks are prone to happen. In the circuit board of the present invention, occurrence of such a problem can be reduced.

Further, in a semiconductor chip, current leakage may occur due to light penetration. However, the dummy wiring layer reduces the amount of light penetrating through the base material, so that a decrease in the performance of the semiconductor chip due to such a current leak can be suppressed.

(2) A circuit board according to the present invention is a resin-sealed board for sealing a portion where the semiconductor-side terminal and the board-side terminal are electrically connected and joining the semiconductor chip to the wiring board. It further has a stop.

According to the present invention, the resin sealing portion for the wiring board is provided by providing the dummy wiring layer in the area of the surface of the base material where the semiconductor chip is mounted and inside the terminal on the substrate side. Can increase the bonding area, thereby improving the bonding strength. As a result, the adhesive strength of the resin sealing portion to the wiring board increases, and the connection reliability between the semiconductor-side terminal and the board-side terminal can be improved.
Further, since the dummy wiring layer prevents the intrusion of humidity from the base substrate side, it is possible to suppress a decrease in the adhesive force of the resin sealing portion due to a change with time. Further, since the dummy wiring layer can be formed of a material having higher adhesiveness to the resin sealing portion than the base material, the adhesive strength of the resin sealing portion to the wiring board can be increased.

(3) In the circuit board according to the present invention, the resin sealing portion is formed of an anisotropic conductive film in which conductive particles are dispersed and mixed in a resin. The terminals are electrically connected by the conductive particles.

When the semiconductor chip and the wiring board are joined by the anisotropic conductive film as described above, TAB (Tape Automat) is used.
ed Bonding) The steps corresponding to the two steps of the bonding step and the molding step in mounting can be performed as one step, and there is an advantage that the manufacturing steps can be shortened.

(4) In the circuit board according to the present invention, the dummy wiring layer is formed of the same material as the substrate-side terminal.

For example, when the substrate side terminal is formed using Cu (copper), a dummy wiring layer is formed of Cu simultaneously with the substrate side terminal. Also, if the board side terminal is C
When the surface of u is formed by applying Ni plating, Au plating, or the like, the dummy wiring layer is also formed by performing the same plating process on the surface of Cu.

As a result, the dummy wiring layer and the substrate-side terminal can be formed simultaneously, and the manufacturing process of the circuit board can be simplified.

(5) In the circuit board according to the present invention, the base material is formed of a flexible material.

For example, the base material is formed of a flexible material such as polyimide. When the base material is formed from a thin flexible material, the base material is easily deformed by external stress. Therefore, when the semiconductor chip is joined to the wiring board by the resin sealing portion, stress is locally concentrated on the bonding interface between the base material and the resin sealing portion, and the adhesive strength is reduced, and the semiconductor side terminal and the substrate side Poor connection with terminals is likely to occur. Further, when the base material is a thin material such as polyimide, the infiltration of moisture from the base material side causes a decrease in the adhesive force, and connection failure between the electrode terminals is likely to occur as time passes. Therefore, in a circuit board in which a semiconductor chip is mounted on a wiring circuit using such a flexible base material using a bonding agent, a region of the surface of the base material where the semiconductor chip is mounted as in the present invention. If a dummy wiring layer is provided inside and inside the board side terminal,
The adhesive strength of the resin sealing portion to the base material is improved, and the connection reliability between the semiconductor side terminal and the substrate side terminal can be improved.

(6) In the circuit board according to the present invention, the base material, the dummy wiring layer and the substrate-side terminal are directly joined without interposing an adhesive layer.

When the dummy wiring layer and the substrate-side terminals are formed directly on the base material without using the adhesive layer, the current leakage due to the adhesive is reduced, the swelling of the adhesive is prevented, and the flexibility of the wiring substrate is reduced. Improvement can be achieved.

(7) The circuit board according to the present invention further has an open portion that is in contact with the dummy wiring layer in plan view, is an area where the base material is exposed, and is continuous with an area where the surrounding base material is exposed. The dummy wiring layer contacts only the opening in plan view.

According to the present invention, when the semiconductor chip is pressed against the wiring board with the bonding resin serving as the resin sealing portion interposed therebetween, the bonding resin is pushed to the outer portion through the open portion. Can be reduced, and the thickness of the resin sealing portion can be made uniform. Thereby, the distortion of the base material is eliminated and the residual stress can be reduced, so that the connection reliability is improved.

(8) In the circuit board according to the present invention, the dummy wiring layer is formed as one continuous region.

(9) The circuit board according to the present invention provides (8)
, The dummy wiring layer is formed as a meandering region.

(10) The circuit board according to the present invention comprises:
In (8), the dummy wiring layer is formed as a region formed by combining a plurality of first line segment regions parallel to each other and a second line segment region extending across the first line segment region. .

(11) The circuit board according to the present invention comprises:
In any one of (1) to (6), the dummy wiring layer has at least one opening.

According to the present invention, in the region where the semiconductor chip is mounted, the perforated dummy wiring layer is formed on the surface of the base material. Therefore, when the semiconductor chip is bonded to the wiring board by the resin sealing portion, the bonding interface between the wiring substrate and the resin sealing portion becomes uneven, and the bonding strength between the resin sealing portion and the wiring substrate is increased by mechanical engagement. The added reliability greatly improves the reliability of the joint.

(12) The circuit board according to the present invention comprises:
In any one of (1) to (6), the dummy wiring layer is formed as a plurality of dummy wiring regions separated by regions where the base material is exposed.

According to the present invention, when the semiconductor chip is bonded to the wiring board by the resin sealing portion, the bonding interface between the wiring substrate and the resin sealing portion becomes uneven, and the bonding between the resin sealing portion and the wiring board becomes uneven. Since the strength is increased by the mechanical engagement of the force, the reliability of the joint is greatly improved.

(13) The circuit board according to the present invention comprises (1)
In 2), the plurality of dummy wiring regions are partially connected. This makes it possible to improve the adhesion between the resin sealing portion and the wiring board when the semiconductor chip is joined to the wiring substrate by the resin sealing portion.

(14) The circuit board according to the present invention comprises:
In any one of (1) to (6), the dummy wiring layer has at least one recess having a wiring layer thinner than other regions of the dummy wiring layer.

According to the present invention, when the semiconductor chip is bonded to the wiring board by the resin sealing portion, the bonding interface between the wiring substrate and the resin sealing portion becomes uneven, and the bonding between the resin sealing portion and the wiring substrate is performed. Since the strength is increased by the mechanical engagement to the force, the reliability of the joint is improved.

(15) The display device according to the present invention comprises:
A circuit board according to any one of (1) to (14),
A flat panel having connection terminals to which the circuit board is electrically connected.

(16) The display device according to the present invention comprises:
In 5), the flat panel is a liquid crystal panel including a pair of opposed substrates and a liquid crystal sealed between the pair of substrates, and the connection terminal is formed on at least one of the pair of substrates. ing.

(17) The electronic device according to the present invention has the following features.
5) or the display device according to (16) is provided as display means.

[0041]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below more specifically with reference to the drawings.

1. First Embodiment 1.1 Circuit Board First, a mounting structure on a circuit board according to a first embodiment of the present invention will be described. FIG. 1 is a plan view showing a part of the circuit board, and FIG. 2 is a cross-sectional view taken along a line AA shown in FIG. In these figures, an FPC (Flexible Printed Circuit) is used as a wiring board.
it) The substrate 400 firstly forms a copper thin film on both sides of a base film 410 as a base material having insulation and flexibility by sputtering or vapor deposition. Third, it is patterned into a predetermined shape by a photolithography technique, etching, or the like, and thirdly, copper plating is applied on the patterned copper thin film. Further, as the FPC substrate 400, a substrate obtained by applying a polyamic acid, which is a precursor of a polyimide, to a copper foil, heating and polymerizing the polyamic acid to form a polyimide, and using the polyimide as a base film 410 to form a wiring substrate may be used. .

The FPC board 400 may be formed by laminating copper foil on both sides of a base film 410 with an adhesive and then patterning it into a predetermined shape, as described above. When the wiring pattern is directly formed on 410, the current leak due to the adhesive in the adjacent wiring pattern, the swelling of the adhesive does not occur, and the flexibility of the FPC board 400 is improved. Is advantageous.

As the base film 410 as a base material, other organic films such as polyethylene terephthalate and polyester may be used in addition to polyimide. On the other hand, the wiring patterns formed on the FPC board 400 include the input wiring 420a and the output wiring 42.
0b, a dummy wiring layer 422, and the like.

On the other hand, the rectangular parallelepiped IC chip 450 (semiconductor chip) has a plurality of input electrodes 450a and output electrodes 450b as semiconductor-side terminals on one peripheral portion thereof, and the input electrodes 450a and the output electrodes 450b are provided on the periphery. FPC board 400 with the formed surface facing down
Implemented in Each input electrode 450a and each output electrode 4
50b is a bump (protruding electrode) made of, for example, Au or the like.
Is formed in advance. In bonding the IC chip 450 to the FPC board 400, first, the IC chip 450 is placed at a predetermined position on the FPC board 400 in the form of a film in which the conductive particles 21 are uniformly dispersed in the adhesive resin 19 such as epoxy. Anisotropic Conductive F
ilm: ACF) is placed. After that, the IC chip 450 is pressed against the FPC substrate 400 in a heated state, and is pressed through the anisotropic conductive film that has been pressed and heated.
It is joined to the substrate 400. Thus, the IC as the semiconductor chip is mounted on the FPC board 400 as the wiring board.
A circuit board on which the chip 450 is mounted is formed.

In this mounting, as shown in FIG. 2, the input electrode 450a is connected to the input wiring 420a (terminal on the substrate), and the output electrode 450b is connected to the output wiring 420b (terminal on the substrate). Electrical connection is achieved via conductive particles 21 dispersed in an appropriate ratio in an adhesive resin 19 such as a curable resin. here,
The bonding resin 19 protects the surface of the IC chip 450 on which the input electrode 450a and the output electrode 450b are formed from moisture, contamination, stress, and the like, and joins the IC chip 450 to the FPC board 400. Also serves as.

When the IC chip 450 and the FPC board 400 are joined by the anisotropic conductive film, the conventional T
In the AB mounting, the joining step and the molding step can be performed as one step, and there is an advantage that the manufacturing step can be shortened.

Incidentally, the dummy wiring layer 422 in the present embodiment is provided so that the dummy wiring layer 422 does not contact any of the input wiring 420a and the output wiring 420b, which are the substrate-side terminals.
It is formed in a region where the C chip 450 is mounted, and has a plurality of openings 422a as shown in FIGS. Therefore, in the area where the IC chip 450 is mounted, the area where the base film 410 having a smooth surface is exposed is reduced, and the opening 422 is formed.
There is a dummy wiring layer 422 having a plurality of “a”. Therefore, in addition to the bonding strength between the base film 410 and the bonding resin 19, the mechanical strength of the dot-shaped dummy wiring layer 422 improves the mechanical engagement structure, and thus the bonding between the bonding resin 19 and the wiring board 400. The strength has improved significantly.

Also, due to the presence of the dummy wiring layer 422, the area where the base film 410 is exposed due to the absence of the copper foil is minimized in the region where the IC chip 450 is mounted. Therefore, in FIG. 2, moisture penetrating from below the base film 410 is blocked by the dummy wiring layer 422 and hardly penetrates into the bonding resin 19 which is a resin sealing portion. This prevents the reliability of the IC chip 450 from being reduced. Similarly to moisture, light that enters from below the base film 410 in the drawing is almost blocked by the dummy wiring layer 422 and does not enter the electrode forming surface (wiring forming surface) of the IC chip 450. IC by leak
A decrease in the performance of the chip 450 is also prevented.

In the above embodiment, the input electrode 4
The bonding between the input wiring 420a and the input wiring 420a and the bonding between the output electrode 450b and the output wiring 420b are performed via the conductive particles 21 dispersed in the bonding resin 19, that is, the anisotropic conductive film. However, other joining forms may be used. For example, the input wiring 420a and the output wiring 420
Au plating is applied to the copper foil forming
Au and the Au bump of the output electrode 450b.
-Au junction may be used. Further, the copper foil forming the input wiring 420a and the output wiring 420b is plated with tin, and this is heated in contact with the Au bumps of the input electrode 450a and the output electrode 450b of the IC chip 450, so that Au-Sn eutectic bonding is achieved. May be. Further, the copper foil forming the input wiring 420a and the output wiring 420b is formed into a solderable pattern, and the IC chip 4
The material of the bumps in the 50 input electrodes 450a and the output electrodes 450b may be solder-solder-bonded. In such bonding, the IC chip 450 is molded using a sealing material as a resin sealing portion.

Further, what is mounted on the FPC board 400 is not limited to the IC chip 450. For example, FPC board 4
Other active elements and non-active elements may be used as long as they are likely to be affected by moisture or light penetrating through the base film 410 when mounted on the base film 410.

Further, the adhesive resin 19 in which the conductive particles 21 are dispersed is concentrated on the input electrode 450a and the output electrode 450b of the IC chip 450, and the input electrode 450a
And the input wiring 420a, and the output electrode 450b and the output wiring 420b, respectively, and then these joints may be molded with a sealing material as a resin sealing portion.

In addition, since the dummy wiring layer 422 is not used as a wiring, if the potential is not determined, a capacitance component is generated, which is not preferable. For this reason, it is actually desirable to connect to the wiring of the ground level.

1.2 Display Device As described above, when the IC chip 450 is mounted on the FPC board 400, the time required for the process is longer regardless of the number of connection electrodes of the IC chip 450 as compared with wire bonding. It will be constant. Therefore, when the number of electrodes of the IC chip 450 is extremely large, the productivity is significantly improved. Here, as an IC chip having an extremely large number of electrodes, for example, a driving circuit (driver) for driving a data line or a scanning line in a display device is given. Therefore, as an application example of such a mounting structure, a liquid crystal device using an FPC board on which such a driver is mounted will be described.

As shown in FIG. 3, the liquid crystal device 1
Is mainly composed of a liquid crystal panel 100 and the liquid crystal panel 10.
0 FPC boards 400X, 400Y joined to
And a control circuit board (not shown) connected to these FPC boards 400X and 400Y. Among them, the liquid crystal panel 100 is configured such that the element substrate 200 on which a plurality of data lines and the like are formed, and the counter substrate 300 on which a plurality of scanning lines and the like are formed, with the respective terminal regions 216 and 316 protruding outside, and In this case, the electrodes are bonded together with their electrode forming surfaces facing each other.

More specifically, as shown in FIG. 4, a plurality of pixel electrodes 234 arranged in a matrix and extending in the column direction on the surface of the element substrate 200 facing the opposite substrate 300. A data line (signal line) 212 is formed, and each column of pixel electrodes 234 is
Each of the data lines 212 has a TFD (Thin Film Diod).
e) connected via element 220; Where TF
The D element 220 includes a first metal film 222 as viewed from the substrate side.
And an oxide film 224 obtained by anodizing the first metal film 222
And a second metal film 226 to form a metal / insulator / metal sandwich structure. Therefore, T
The FD element 220 has a switching characteristic as a diode in both positive and negative directions.

On the other hand, of the opposing substrate 300, the element substrate 2
The scanning line 312 is provided on the surface facing
Are arranged in such a manner as to extend in a row direction perpendicular to the pixel electrodes 234, and are arranged so as to be opposed to the pixel electrodes 234. Further, although not shown, a color filter is provided corresponding to each pixel electrode 234. ing. Therefore, the liquid crystal cell corresponding to one pixel is configured to include the pixel electrode 234, the scanning line 312 which is an opposite electrode, and the liquid crystal filled between these two substrates.

Then, the element substrate 200 and the opposing substrate 300
Is that a certain gap (gap) is maintained by a sealing material applied along the periphery of the substrate and spacers appropriately dispersed, and for example, TN (Twis
ted Nematic) type liquid crystal is enclosed. In addition,
On the opposing surfaces of the element substrate 200 and the opposing substrate 300, an alignment film or the like rubbed in a predetermined direction is provided, and on the back surface, a polarizing plate corresponding to the alignment direction is provided. Omitted). However,
If a polymer-dispersed liquid crystal in which a liquid crystal is dispersed as fine particles in a polymer is used, the above-described alignment film, polarizing plate, and the like become unnecessary. The use of a polymer-dispersed liquid crystal enhances light use efficiency, which is advantageous in terms of high luminance and low power consumption.

In such a configuration, the data line 21
2 and the scanning line 312 are electrically coupled to each other at the intersection thereof via a series connection of the liquid crystal layer and the TFD element 220. Therefore, when a voltage equal to or higher than the threshold value is applied to the TFD element 220 by the scanning signal applied to the scanning line 312 and the data signal applied to the data line 212, the element is turned on and the element is turned on. A predetermined charge is stored in a liquid crystal layer connected to the liquid crystal layer. Then, even after the element is turned off after charge accumulation, if the resistance of the liquid crystal layer is sufficiently high, accumulation of charge in the liquid crystal layer is maintained. When the amount of charge to be stored is controlled by driving the TFD element 220 on and off in this manner, the alignment state of the liquid crystal changes for each pixel, and predetermined information can be displayed. At this time, since it is sufficient to accumulate electric charges in each liquid crystal layer during a part of the period, by selecting each scanning line 312 in a time-division manner, the data line 212 and the scanning line 31 are selected.
Time-division multiplex driving in which 2 is common to a plurality of pixels is possible. Note that the formation of the scanning lines and the data lines may be reversed, and the scanning lines may be formed on the element substrate 200 and the data lines may be formed on the opposite substrate.

Now, although not shown in FIG.
A data line terminal which is a connection terminal for leading each data line to the outside is provided in the terminal region 216 of 00, while a connection region for leading each scanning line to the outside is provided in the terminal region 316 of the counter substrate 300. A scanning line terminal, which is a terminal, is provided below the substrate.

The FPC boards 400X and 400Y are
For example, it has the structure of the above-described circuit board including the FPC board 400, the IC chip 450, and the dummy wiring layer 422. Among them, FPC board 400X
In this case, the driver 450X for driving each data line is mounted as an IC chip in an upside down manner in FIG. Therefore, the dummy wiring layer 422 in the FPC board 400X
X will be provided on the upper side in FIG. On the other hand, on the FPC board 400Y, a driver 450Y for driving each scanning line is mounted as an IC chip in the same direction as the top and bottom in FIG. Therefore, the dummy wiring layer 422Y in the FPC board 400Y is provided on the lower side in FIG.

Here, for the FPC board 400X,
A terminal located at one end thereof and extending the input wiring is joined to the control circuit board, while a terminal located at the other end and extending the output wiring is provided in the terminal region 216 of the element substrate 200. It is joined to the formed data line terminal which is a connection terminal. Similarly, the FPC board 400
In the case of Y, while terminals located at one end thereof and extending input wirings are joined to the control circuit board,
Terminals located at the other end and extending output wirings are joined to scanning line terminals, which are connection terminals formed in the terminal region 316 of the counter substrate 300.

With such a configuration, the driver 450Y
Generates a scanning signal according to a control signal supplied from the control circuit board, and supplies the scanning signal to each scanning line of the element substrate 200. On the other hand, the driver 450X supplies a data signal according to a control signal supplied from the control circuit board to each data line of the counter substrate 300. At this time, the driver 4 mounted on each of the FPC boards 400X and 400Y
As described above, in the 50X and 450Y, the reduction in reliability and performance is prevented by the dummy wiring layers 422X and 422Y provided corresponding to the mounting area.

In addition, as a liquid crystal panel,
Applicable to passive matrix method without TFD element or liquid crystal panel where scanning lines and data lines are provided on the element substrate and pixel electrodes are connected to their intersections via TFT (Thin Film Transistor) elements It is.

1.3 Electronic Equipment 1.3.1 Projector Next, an example in which the above-described liquid crystal device 1 is used for a display unit of an electronic equipment will be described. FIG. 5 is a plan view showing a configuration example of a projector using the liquid crystal panel as a light valve.

As shown in this figure, the projector 1
Inside 100, a lamp unit 1102 composed of a white light source such as a halogen lamp is provided. The projection light emitted from the lamp unit 1102 is separated into three primary colors of RGB by four mirrors 1106 and two dichroic mirrors 1108 arranged in the light guide 1104, and is used as a light valve corresponding to each primary color. Liquid crystal panels 1110R, 1110B and 1110
G is incident.

The liquid crystal panels 1110R, 1110B and 1110G are the above-mentioned liquid crystal panels, and are supplied from the image signal processing circuit (not shown) to the FPC boards 400X and 400X.
It is driven by R, G, and B primary color signals supplied via Y, respectively. Light modulated by these liquid crystal panels enters a dichroic prism 1112 from three directions. This dichroic prism 111
In 2, the R and B lights are refracted at 90 degrees, while the G light goes straight. Therefore, as a result of combining the images of each color, a color image is projected on a screen or the like via the projection lens 1114.

Here, the liquid crystal panels 1110R, 1110
B and 1110G have dichroic mirror 110
8, light corresponding to each of the primary colors of R, G, and B enters, so that it is not necessary to provide a color filter on the counter substrate 300.

1.3.2 Mobile Phone FIG. 6 shows a mobile phone 30 which is another example in which the above-described liquid crystal device 1 is used for a display section of an electronic apparatus. The mobile phone 30 is configured by storing various components such as an antenna 31, a speaker 32, a liquid crystal device 1, a key switch 33, and a microphone 34 in an outer case 36 as a housing. Further, inside the outer case 36, a control circuit board 37 on which a control circuit for controlling the operation of each of the above-described components is mounted is provided. The liquid crystal device 1 is constituted by the liquid crystal device 1 shown in FIG.

In this portable telephone 30, the key switch 3
Signals input through the microphone 3 and the microphone 34, received data received by the antenna 31, and the like are input to the control circuit on the control circuit board 37. Then, the control circuit displays images such as numbers, characters, and patterns on the display surface of the liquid crystal device 1 based on the input various data.
The transmission data is transmitted from the antenna 31.

2. Second Embodiment The second embodiment is different from the first embodiment in the shape of the dummy wiring layer. Otherwise, the configuration is the same as in the first embodiment, and a description thereof will be omitted. Further, in the drawings, the same components as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment.

FIG. 7 is a plan view showing a mounting structure of the wiring board of the present embodiment, and FIG.
It is sectional drawing in the position along the A line. As shown in these figures, the FPC board 40 in the second embodiment
2 are provided with slits 424a as a plurality of openings formed by removing the copper foil.
Are provided in the longitudinal direction of the IC chip 450. Therefore, the area where the dummy wiring layer 424 is provided is
Since the projections and depressions have an uneven shape when viewed from the chip 450, the adhesion of the IC chip 450 to the adhesive resin 19 is improved as in the first embodiment.

In the second embodiment, the slit 424a provided in the dummy wiring layer 424 is set in the longitudinal direction of the IC chip 450, but may be in the short direction.
Further, the shape may be a cross shape in which the longitudinal and transverse directions are combined, or may be an oblique direction.

3. Third Embodiment The third embodiment differs from the first embodiment in the shape of the dummy wiring layer. Otherwise, the configuration is the same as in the first embodiment, and a description thereof will be omitted. Further, in the drawings, the same components as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment.

In the second embodiment, the IC chip 4
Although the adhesiveness of 50 is improved, the area where base film 410 is exposed in the area where IC chip 450 is mounted increases due to the presence of slit 424a.
For this reason, there is a disadvantage that the reliability and performance of the IC chip 450 may be reduced as compared with the first embodiment as a result of an increase in moisture and light amount penetrating the base film 410.

Therefore, after ensuring the reliability and performance of the IC chip 450 at the same level as in the first embodiment,
A description will be given of a mounting structure of the circuit board of the third embodiment in which the adhesion of the IC chip 450 is improved. FIG.
FIG. 10 is a plan view showing a mounting structure of the circuit board, and FIG. 10 is a cross-sectional view taken along a line AA shown in FIG. As shown in these drawings, the dummy wiring layer 426 provided on the FPC board 404 in the third embodiment has a plurality of slits 4 similar to the second embodiment.
26a is provided, but unlike the second embodiment,
The copper foil is not removed in the slit 426a. That is, as is apparent from FIG.
In the above, the thickness of the body foil was reduced, but not removed. Therefore, the area where the base film 410 is exposed in the region where the IC chip 450 is mounted is minimized, so that the moisture and light penetrating the base film 410 are substantially blocked by the dummy wiring layer 426. . As a result, similarly to the first embodiment, a decrease in the reliability and performance of the IC chip 450 is prevented. further,
The area where the dummy wiring layer 426 is provided is the IC chip 4
Since it has an uneven shape as viewed from 50, the adhesiveness of the IC chip 450 to the adhesive resin 19 is improved as in the first embodiment.

Note that such a dummy wiring layer 426 is
It can be formed by the following method. For example, FIG.
In the area of the dummy wiring layer 426 and the slit 426a
After forming the pattern of the body foil having a planar shape in which the region of FIG. 9 is added, light etching is performed on a portion corresponding to the slit 426a, and conversely, in FIG. 9, the region of the dummy wiring layer 426 and the region of the slit 426a After the pattern of the body foil having a planar shape with the addition of is added, the portion other than the portion corresponding to the slit 426a can be formed by a method of thickening copper by plating or the like.

4. Fourth Embodiment In a fourth embodiment, the shape of the dummy wiring layer, the arrangement of the semiconductor side terminals and the substrate side terminals, and the liquid crystal panel to which the circuit board is connected are:
This is different from the first embodiment. Otherwise, the configuration is the same as in the first embodiment, and a description thereof will be omitted.
Further, in the drawings, each part similar to the first embodiment includes:
The same reference numerals as in the first embodiment are used.

FIG. 11 is an exploded perspective view showing the liquid crystal device 1 according to the present embodiment. The liquid crystal device 1 is formed by connecting a circuit board 3 to a liquid crystal panel 2. If necessary, a lighting device such as a backlight,
Other accessory devices are attached to the liquid crystal panel 2.

The liquid crystal panel 2 has a pair of substrates 6a and 6b adhered by the sealing material 4, and a gap formed between the substrates, that is, a cell gap,
TN (Super Twisted Nematic) type liquid crystal is sealed and formed. The substrates 6a and 6b are generally formed of a translucent material, for example, glass, synthetic resin, or the like. A polarizing plate 8 is adhered to the outer surfaces of the substrates 6a and 6b.

An electrode 7a is formed on the inner surface of one substrate 6a, and an electrode 7b is formed on the inner surface of the other substrate 6b. These electrodes are formed in stripes, letters, numbers, or other appropriate patterns. These electrodes 7a and 7b are made of, for example, ITO (Indium T
It is formed of a translucent conductive material such as in Oxide (indium tin oxide).

One substrate 6a has an overhang extending from the other substrate 6b, and a plurality of connection terminals 9 are provided on the overhang.
Are formed. These connection terminals 9 are formed simultaneously with the formation of the electrodes 7a on the substrate 6a, and are formed, for example, of ITO. These connection terminals 9 include those extending integrally from the electrode 7a and those connected to the electrode 7b via a conductive material (not shown).

The electrodes 7a and 7b and the connection terminal 9 are
Actually, many are formed on the substrate 6a and the substrate 6b at extremely narrow intervals. However, in FIG. 11, in order to show the structure in an easily understandable manner, the intervals are schematically shown enlarged. Are shown, and other parts are omitted. The connection between the connection terminal 9 and the electrode 7a and the connection between the connection terminal 9 and the electrode 7b are also omitted in FIG.

The circuit board 3 is formed by mounting the liquid crystal driving IC chip 11 as a semiconductor chip at a predetermined position on the wiring board 13 and mounting a chip component 18 at another predetermined position on the wiring board 13. Is done. Wiring board 1
3 is a wiring pattern 1 made of Cu or the like on a base substrate 15 as a flexible base material such as polyimide.
6 is formed.

The wiring pattern 16 may be fixed on the base substrate 15 by an adhesive layer, or may be fixed directly on the base substrate 15 by a film forming method such as a sputtering method or a roll coating method. You may. The wiring board 13 can also be manufactured by forming a wiring pattern 16 of Cu or the like on a relatively hard and thick board such as an epoxy board.

When a mounting component is mounted on the wiring board 13 using a flexible base material (base board 15) as the wiring board 13, a circuit board of a COF (Chip On Film) system is formed. On the other hand, if mounting components are mounted on a wiring board using a hard base material (base board) as the wiring board 13, CO
A circuit board of a B (Chip On Board) system is configured.

In FIG. 11, the wiring pattern 16 includes
An output terminal 16a formed on one side of the circuit board 3 and an input terminal 16b formed on a side opposite to the output terminal 16a
Is included. Further, a portion of the wiring pattern 16 in a region for mounting the liquid crystal driving IC chip 11 constitutes a substrate-side terminal 17.

The liquid crystal driving IC chip 11 has a plurality of bumps 14 as semiconductor-side terminals on the bonding surface, that is, the active surface. The liquid crystal driving IC chip 11 is mounted at a predetermined position on the base substrate 15 by an anisotropic conductive film 12 as a bonding agent. Then, the chip component 18 is mounted at another predetermined position on the base substrate 15 by soldering. Here, as the chip component 18, a capacitor,
Passive components such as resistors and electronic elements such as connectors are conceivable.

As shown in FIG. 12, the anisotropic conductive film 12 is formed by mixing a plurality of conductive particles 21 in an adhesive resin 19. Liquid crystal driving IC chip 1
Reference numeral 1 denotes a liquid crystal driving IC chip 1 which is fixed to the base substrate 15 by an adhesive resin 19 in the anisotropic conductive film 12.
One bump 14 is formed of conductive particles 21 in anisotropic conductive film 12.
Thus, it is conductively connected to the substrate side terminal 17 of the wiring pattern 16.

When manufacturing the circuit board 3 shown in FIG. 12, first, a wiring pattern 16 having a predetermined pattern is formed on a base substrate 15 to manufacture a wiring board 13, and then the anisotropic conductive film 12 is formed. The liquid crystal driving IC chip 11 is placed at a predetermined position on the wiring board 13 with the liquid crystal driving IC chip 11 interposed therebetween, and the liquid crystal driving IC chip 11 is heated and pressed to melt the bonding resin 19 in the anisotropic conductive film 12. Thus, the liquid crystal driving IC chip 11 is mounted on the wiring board 13.

Thereafter, solder is patterned by printing, dispensing, or the like at a position on the wiring board 13 where the chip component 18 (see FIG. 11) is to be mounted, and the chip component 18 is placed on the solder pattern. The wiring board 13 is inserted into a furnace of a high-temperature furnace heated to 200 ° C. to 250 ° C. for a short time, heated, and then taken out of the furnace and cooled.

The insertion time at this time is as short as possible and sufficient to melt the solder. When the above-described series of soldering processes, that is, the so-called solder reflow process, is completed, the chip component 18 is mounted at a predetermined position on the wiring board 13 on which the liquid crystal driving IC chip 11 is already mounted by soldering.

Here, the order of mounting the IC chip 11 on the wiring board 13 and the step of mounting the chip components on the wiring board 13 may be reversed. That is, after mounting the chip component 18 on the wiring board 13, the IC chip 11 may be mounted on the wiring board 13.

The circuit board 3 configured as described above
Is connected to the overhang of the substrate 6a of the liquid crystal panel 2 by the anisotropic conductive film 22 in FIG. The anisotropic conductive film 22 is formed of an adhesive resin and conductive particles mixed therein similarly to the anisotropic conductive film 12, and as shown in FIG.
And the substrate 6a are fixed, and the output terminals 16a on the circuit board side and the connection terminals 9 on the board side are conductively connected by the conductive particles.

Further, in the circuit board 3, a dummy wiring layer 23 A is provided in a region of the surface of the base substrate 15 where the liquid crystal driving IC chip 11 is mounted and inside the substrate side terminal 17. I have. As shown in FIG. 13, these dummy wiring layers 23A include a plurality of independent line segment patterns (a plurality of line segment patterns parallel to the short side of the IC chip 11) arranged in parallel with each other in one direction. )
Is formed by An open portion 24 that is open outward is formed between these line segment patterns.

The dummy wiring layer 23A can be formed independently through a dedicated process, but in this embodiment,
When the substrate-side terminals 17 and the wiring patterns 16 are formed by a known patterning method, for example, a photolithography method, they are simultaneously formed of the same material, for example, Cu or the like. In addition, the surface of the substrate-side terminal 17 formed of Cu or the like may be subjected to Ni plating, Au plating, Sn plating, solder plating, or the like. In this case, the surface of the dummy wiring layer 23A is also provided. The same plating is applied.

Since the dummy wiring layer 23A of this embodiment is formed by line patterns that are electrically insulated from each other during the plating process, it is difficult to use the electrolytic plating process. It is desirable that the plating process on 23A be performed by an electroless plating process.

The dummy wiring layer 23A has a structure in which a metal such as Cu is used as a base and its surface is plated with Ni plating, Au plating or the like. 12 has high adhesiveness to the adhesive resin. In addition, the provision of the dummy wiring layer increases the bonding area of the bonding agent on the base substrate side, thereby improving the bonding strength. In addition, the dummy wiring layer can prevent intrusion of humidity from the base substrate side, and can suppress a decrease in adhesive strength of the bonding agent due to a change with time. Therefore, if the dummy wiring layer 23A is provided in a region of the base substrate 15 where the liquid crystal driving IC chip 11 is mounted, the anisotropic conductive film 12 and the base substrate 15
, That is, the adhesive force between the liquid crystal driving IC chip 11 and the base substrate 15 is increased, and as a result,
The connection reliability of the liquid crystal driving IC chip 11 to the base substrate 15 is improved.

The dummy wiring layer 23A has an open portion 24.
Is formed, the anisotropic conductive film 12 is
Anisotropic conductive film 12 pressed when heated and pressed to
Some of them flow out through their openings 24.
Thereby, generation of residual stress in the anisotropic conductive film 12 can be reduced, and the thickness of the anisotropic conductive film 12 can be made uniform. As a result, the distortion of the base substrate 15 is eliminated, and the residual stress can be reduced.

5. Fifth Embodiment The fifth embodiment is different from the fourth embodiment in the shape of the dummy wiring layer. Otherwise, the configuration is the same as in the fourth embodiment, and a description thereof will be omitted. In the drawings, the same components as those of the fourth embodiment are denoted by the same reference numerals as those of the first embodiment.

FIG. 14 is a partial plan view showing the circuit board of this embodiment in a state before the liquid crystal driving IC chip 11 is mounted. Dummy wiring layer 23B of the present embodiment
Are formed by one continuous pattern extending in one direction (i.e., the horizontal direction in the figure) while meandering. This dummy wiring layer 23B also has an open portion 2 that is opened outward.
4 Since the dummy wiring layer 23B has a single continuous pattern, when plating is performed on this surface, an electrolytic plating process can be used.

The dummy wiring layer 23B also increases the adhesive force between the anisotropic conductive film 12 and the base substrate 15, that is, the adhesive force between the liquid crystal driving IC chip 11 and the base substrate 15. As a result, the connection reliability of the liquid crystal driving IC chip 11 to the base substrate 15 is improved.

The open portion 24 is also provided in the dummy wiring layer 23B.
Is formed, the anisotropic conductive film 12 is
Anisotropic conductive film 12 pressed when heated and pressed to
Can reduce the occurrence of residual stress in the anisotropic conductive film 12 flowing out, and can make the thickness of the anisotropic conductive film 12 uniform. As a result, the distortion of the base substrate 15 is eliminated, and the residual stress can be reduced.

6. Sixth Embodiment A sixth embodiment is different from the fourth embodiment in the shape of the dummy wiring layer. Otherwise, the configuration is the same as in the fourth embodiment, and a description thereof will be omitted. In the drawings, the same components as those of the fourth embodiment are denoted by the same reference numerals as those of the first embodiment.

FIG. 15 is a partial plan view showing the circuit board of this embodiment in a state before the IC chip 11 for driving liquid crystal is mounted. Dummy wiring layer 23C of the present embodiment
Is a plurality of line segment patterns 26 (first line segment regions) arranged parallel to each other along one direction (that is, the left-right direction in the drawing), and extends in one direction across the line segment patterns 26. It is formed as a continuous pattern in combination with the linear pattern 27 (second line segment area). This dummy wiring layer 23C also has an opening 24 that is opened outward. Since this dummy wiring layer 23C is also a single continuous pattern, when plating this surface,
An electrolytic plating process can be used.

The adhesive force between the anisotropic conductive film 12 and the base substrate 15, that is, the adhesive force between the liquid crystal driving IC chip 11 and the base substrate 15 is also increased by the dummy wiring layer 23C. As a result, the connection reliability of the liquid crystal driving IC chip 11 to the base substrate 15 is improved.

The open portion 24 is also provided in the dummy wiring layer 23C.
Is formed, the anisotropic conductive film 12 is
Anisotropic conductive film 12 pressed when heated and pressed to
Can reduce the occurrence of residual stress in the anisotropic conductive film 12 flowing out, and can make the thickness of the anisotropic conductive film 12 uniform. As a result, the distortion of the base substrate 15 is eliminated, and the residual stress can be reduced.

7. <Modification> Here, a modification applicable to the above-described embodiment will be described. In each of the following modifications, only points different from the above-described embodiments will be described and described.

7.1 In the above-described embodiment, the TF which is a two-terminal switching element is used as the liquid crystal panel.
A liquid crystal panel in which TN type liquid crystal is filled with electro-optical characteristics using an active matrix type driving method using D (Thin Film Diode), and an STN (Super Twisted Nematic) type with electro-optical characteristics using simple matrix driving. The liquid crystal panel in which liquid crystal was sealed was shown. However, the liquid crystal panel is not limited to this. In terms of the driving method, a static drive type liquid crystal panel, a three-terminal switching element such as a TFT (Thin Film Transistor) or a two-terminal switching element such as an MIM (Metal- In
active-matrix type liquid crystal panel using sulator-metal), in terms of electro-optical characteristics, guest-host type,
Various types of liquid crystal panels can be used, such as a phase transition type, a ferroelectric type, and a BTN type using a bistable nematic liquid crystal having memory properties.

7.2 Further, the flat display panel used in the present invention is not limited to a liquid crystal panel, but may be another flat display panel, for example, an EL (Electro-Luminescence) display panel, a PDP (Plasma Display Panel) display panel, FE
It may be a D (Field Emission Display) panel or the like.

7.3 In each of the above embodiments, an example has been described in which a semiconductor device as a drive circuit is mounted on a circuit board, and the circuit board is connected to a flat display panel. However, a circuit board of the present invention connected to the flat display panel includes a circuit board on which at least one of a semiconductor device of a driving circuit, a semiconductor device of an image signal processing circuit, and a semiconductor device of another circuit is mounted. There may be.

7.4 Further, in each of the above embodiments, the case where the circuit board according to the present invention is used as a component of the liquid crystal device has been described, but the circuit board according to the present invention may be used for any device other than the liquid crystal device. It can be used as a component.

7.5 In each of the above embodiments, a projector and a mobile phone have been described as examples of electronic equipment incorporating a display device using a circuit board according to the present invention. However, electronic devices incorporating a display device using the circuit board according to the present invention include, in addition to them, a liquid crystal television, a viewfinder type / monitor direct-view type video tape recorder, a car navigation device, an electronic notebook, and a calculator. , Word processors, workstations, mobile phones, pagers, video phones, POS (Point of
Sales) devices, devices with touch panels, and the like.

7.6 The present invention is not limited to the above embodiments, and various modifications can be made within the scope of the present invention or within the equivalent scope of the claims.

[Brief description of the drawings]

FIG. 1 is a plan view showing a circuit board according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along a line AA shown in FIG.

FIG. 3 shows two Fs having the structure shown in FIGS. 1 and 2;
FIG. 2 is an exploded perspective view showing a PC board and a liquid crystal panel.

FIG. 4 is a partially cutaway perspective view showing the configuration of the liquid crystal panel according to the first embodiment.

FIG. 5 is a cross-sectional view illustrating a configuration of a liquid crystal projector as an example of an electronic apparatus to which the liquid crystal device according to the first embodiment is applied.

FIG. 6 is an external view illustrating a mobile phone as another example of the electronic apparatus to which the liquid crystal device according to the first embodiment is applied.

FIG. 7 is a plan view showing a circuit board according to a second embodiment.

FIG. 8 is a cross-sectional view taken along a line AA shown in FIG. 7;

FIG. 9 is a plan view showing a circuit board according to a third embodiment.

FIG. 10 is a cross-sectional view at a position along the line AA depicted in FIG. 9;

FIG. 11 is an exploded perspective view showing a liquid crystal device according to a fourth embodiment.

FIG. 12 is a partial cross-sectional view illustrating a liquid crystal device according to a fourth embodiment.

FIG. 13 is a partial plan view showing the circuit board of the fourth embodiment in a state before the IC chip 11 is mounted.

FIG. 14 is a partial plan view showing the circuit board according to the fifth embodiment before the IC chip 11 is mounted.

FIG. 15 is a partial plan view showing a circuit board according to a sixth embodiment in a state before an IC chip 11 is mounted.

FIG. 16 is a sectional view showing a conventional circuit board.

[Explanation of symbols]

Reference Signs List 1 liquid crystal device 2,100 liquid crystal panel 3 circuit board 6a, 6b substrate 9 connection terminal 10 liquid crystal device 11 liquid crystal driving IC chip (semiconductor chip) 12 anisotropic conductive film 13 wiring substrate 14 bump (semiconductor side terminal) 15 base substrate (Base material) 17 Board-side terminal 19 Adhesive resin (resin sealing portion) 21 Conductive particles 23A, 23B, 23C, 422, 424 Dummy wiring layer 24 Opening portion 26 Line segment pattern (first line segment region) 27 Straight line Pattern (second line segment area) 30 Cellular phone (electronic device) 200 Element substrate 206 Terminal (connection terminal) 300 Counter substrate 400 FPC substrate (wiring substrate) 410 Base film (base material) 420a Input wiring (substrate side terminal) 420b Output wiring (board side terminal) 450 IC chip (semiconductor chip) 1100 Projector (electronic equipment)

Claims (17)

[Claims] 1. A substrate having an insulating property, a wiring board having a plurality of substrate-side terminals provided on the substrate, and a plurality of semiconductor-side terminals, wherein the semiconductor-side terminals are the substrate-side terminals And a semiconductor chip mounted on the wiring board, wherein the wiring board is in a region where the semiconductor chip is mounted and in a region inside the substrate-side terminal, A circuit board comprising a dummy wiring layer insulated from a board side terminal and the semiconductor side terminal. 2. The resin sealing part according to claim 1, further comprising: sealing a portion where the semiconductor-side terminal and the substrate-side terminal are electrically connected, and joining the semiconductor chip to the wiring board. Having a circuit board. 3. The resin-sealed portion according to claim 2, wherein the resin-sealed portion is formed of an anisotropic conductive film in which conductive particles are dispersed and mixed in a resin. A circuit board electrically connected by conductive particles. 4. The circuit board according to claim 1, wherein the dummy wiring layer is formed of the same material as the substrate-side terminal. 5. The circuit board according to claim 2, wherein the base material is formed of a flexible material. 6. The circuit board according to claim 1, wherein the base material, the dummy wiring layer, and the substrate-side terminal are directly joined without using an adhesive layer. 7. The opening according to claim 1, wherein the opening is in contact with the dummy wiring layer in a plan view and is an area where the base material is exposed, and is continuous with a surrounding area where the base material is exposed. Further, the circuit board, wherein the dummy wiring layer is in contact with only the opening in plan view. 8. The circuit board according to claim 1, wherein the dummy wiring layer is formed as one continuous region. 9. The circuit board according to claim 8, wherein the dummy wiring layer is formed as a meandering region. 10. The region according to claim 8, wherein the dummy wiring layer has a shape formed by combining a plurality of first line segment regions parallel to each other and a second line segment region extending across the first line segment region. Circuit board formed as a. 11. The circuit board according to claim 1, wherein the dummy wiring layer has at least one opening. 12. The circuit board according to claim 1, wherein the dummy wiring layer is formed as a plurality of dummy wiring regions separated by a region where the base material is exposed. 13. The circuit board according to claim 12, wherein the plurality of dummy wiring regions are partially connected. 14. The circuit board according to claim 1, wherein the dummy wiring layer has at least one concave portion whose wiring layer is thinner than other regions of the dummy wiring layer. 15. A display device, comprising: the circuit board according to claim 1; and a flat panel including a connection terminal to which the circuit board is electrically connected. 16. The liquid crystal panel according to claim 15, wherein the flat panel is a liquid crystal panel having a pair of substrates facing each other and a liquid crystal sealed between the pair of substrates. The display device formed in at least one of the above. 17. An electronic apparatus comprising the display device according to claim 15 as display means.