JP2017003708A - Liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device capable of further improving display characteristics. A liquid crystal display device (10) includes first and second substrates (20, 21) arranged opposite to each other, a polymer dispersed liquid crystal layer (22) sandwiched between the first and second substrates (20, 21), and a first Wiring electrode 24 provided on substrate 20, interlayer insulating film 25 provided on wiring electrode 24 and having through hole 27 exposing a part of wiring electrode 24, and display electrode provided on interlayer insulating film 25 26, a connection electrode 26 </ b> A provided in the through hole 27 and electrically connecting the wiring electrode 24 and the display electrode 26, and a common electrode 28 provided on the second substrate 21. The angle θ formed by the inner wall of the through hole 27 and the surface of the wiring electrode 24 is set to a value that makes it difficult for the through hole 27 to be visually recognized in plan view. [Selection] Figure 5

Description

  The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device using polymer dispersed liquid crystal.

  A polymer-dispersed liquid crystal has a structure in which liquid crystals are phase-separated in a polymer (polymer network) formed in a three-dimensional network, and liquid crystal molecules are randomly arranged along the side wall of the polymer network. A light scattering state and a light transmission state are respectively created in a state where the liquid crystal molecules are arranged in the electric field direction by applying an electric field (for example, Patent Document 1). The degree of scattering is determined by the voltage applied to the liquid crystal, and the voltage applied to the liquid crystal is determined by the partial pressure between the polymer material and the liquid crystal.

  For example, a liquid crystal display device is configured by sandwiching a polymer-dispersed liquid crystal layer between two glass substrates and bonding the two glass substrates with a sealing material so as to enclose the polymer-dispersed liquid crystal layer. An interlayer insulating film is formed on the wiring electrode on the glass substrate, and a display electrode is further formed on the interlayer insulating film. The display electrode is electrically connected to the wiring electrode through a connection electrode in a through hole formed in the interlayer insulating film. In such a liquid crystal display device, a through hole in the display region may be noticeable when in a transmissive state.

JP 2000-195853 A

  The present invention provides a liquid crystal display device capable of further improving display characteristics.

A liquid crystal display device according to one embodiment of the present invention includes a first substrate and a second substrate arranged to face each other, a polymer-dispersed liquid crystal layer sandwiched between the first and second substrates, and the first substrate. A wiring electrode provided on the wiring electrode, an interlayer insulating film having a through hole exposing a part of the wiring electrode, a display electrode provided on the interlayer insulating film, and the through hole And a connection electrode that electrically connects the wiring electrode and the display electrode, and a common electrode provided on the second substrate. When the refractive index of the liquid crystal layer is n _PN , the refractive index of the interlayer insulating film is n _INS , and the film thickness of the interlayer insulating film is b (μm), the inner wall of the through hole and the surface of the wiring electrode are The angle θ formed is

And 90 degrees or less.

  ADVANTAGE OF THE INVENTION According to this invention, the liquid crystal display device which can improve a display characteristic more can be provided.

It is a top view of the liquid crystal display device concerning an embodiment. FIG. 2 is a cross-sectional view taken along line A-A ′ of the liquid crystal display device shown in FIG. It is a figure which shows the orientation state of the liquid crystal layer in embodiment. It is a top view of the through hole in an embodiment. FIG. 5 is a cross-sectional view taken along line B-B ′ of the through hole shown in FIG. 4. It is a figure which shows the relationship between the taper angle in an embodiment, a refraction angle, and the length of a taper part. It is a figure which shows the relationship between the taper angle in embodiment, and the length of a taper part. It is a figure which shows the relationship between the apparent length of the taper part of a through hole, and the visibility of a through hole. It is a figure which shows the relationship between the taper angle in embodiment, and the visibility of a through hole. It is a figure which shows the relationship between the film thickness of the interlayer insulation film and taper angle in embodiment. It is sectional drawing which shows the formation method of the through hole in embodiment.

  Hereinafter, embodiments will be described with reference to the drawings. However, it should be noted that the drawings are schematic or conceptual, and the dimensions and ratios of the drawings are not necessarily the same as the actual ones. Further, even when the same portion is represented between the drawings, the dimensional relationship and ratio may be represented differently. In particular, the following embodiments exemplify an apparatus and a method for embodying the technical idea of the present invention, and the technical idea of the present invention depends on the shape, structure, arrangement, etc. of components. Is not specified. In the following description, elements having the same function and configuration are denoted by the same reference numerals, and redundant description will be given only when necessary.

  The liquid crystal display device of the embodiment will be described below.

[1] Configuration of liquid crystal display device
FIG. 1 is a plan view of a liquid crystal display device according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the liquid crystal display device taken along line AA ′ of FIG. The liquid crystal display device 10 according to the present embodiment is a pattern display type liquid crystal display device capable of displaying a plurality of patterns such as characters and figures.

  The liquid crystal display device 10 includes a first substrate 20 provided with display electrodes, a second substrate 21 provided with a common electrode and disposed opposite to the first substrate 20, and between the first substrate 20 and the second substrate 21. And a sandwiched liquid crystal layer 22. The 1st board | substrate 20 and the 2nd board | substrate 21 are comprised from a transparent substrate, for example, are comprised from a glass substrate.

  The first substrate 20 and the second substrate 21 are bonded together by a frame-shaped sealing material 23 surrounding the display area (view area) VA. The liquid crystal layer 22 is sealed between the first substrate 20 and the second substrate 21 by a sealing material 23. The sealing material 23 is made of, for example, an organic adhesive and is formed by, for example, a printing process. The thickness (cell gap) of the liquid crystal layer 22 is, for example, about 7 μm. The liquid crystal layer 22 will be described in detail later.

  A plurality of wiring electrodes 24 are provided on the liquid crystal layer 22 side of the first substrate 20. An interlayer insulating film 25 is provided on the wiring electrode 24. A plurality of display electrodes 26 are provided on the interlayer insulating film 25 in the display area VA. The interlayer insulating film 25 electrically insulates between the wiring electrode 24 and the display electrode 26. Each of the plurality of display electrodes 26 is processed so that the planar shape thereof has a desired pattern.

  The display electrode 26 is electrically connected to the corresponding wiring electrode 24 via a connection electrode 26 </ b> A formed in the through hole 27. For example, the connection electrode 26 </ b> A is formed in the same process as the display electrode 26. Specifically, a through hole 27 is formed in the interlayer insulating film 25, and the same conductive material as that of the display electrode 26 is embedded in the through hole 27. Thereby, the connection electrode 26A and the display electrode 26 are integrally formed. The wiring electrode 24 is drawn from a part of the display electrode 26 to the outside of the display area VA, and is used to apply a voltage to the display electrode 26. The through hole 27 will be described in detail later.

  The display electrode 26, the connection electrode 26A, and the wiring electrode 24 are made of a transparent conductive material, for example, ITO (Indium Tin Oxide). The film thickness of the display electrode 26 and the wiring electrode 24 is, for example, 100 mm or more and 1000 mm or less. The interlayer insulating film 25 is made of, for example, silicon nitride (SiN) having a film thickness of 0.3 μm or more and 0.9 μm or less.

  A common electrode 28 is provided on the liquid crystal layer 22 side of the second substrate 21. The common electrode 28 is provided in a planar shape over the entire display area VA, and has a size that overlaps at least all the display electrodes 26. The common electrode 28 is made of, for example, ITO, and the film thickness is, for example, not less than 100 mm and not more than 1000 mm.

  A drive circuit 30 is provided in the peripheral area PA of the first substrate 20 other than the display area VA. The drive circuit 30 is configured by, for example, an LSI (large-scale integrated circuit). The drive circuit 30 is electrically connected to a plurality of wiring electrodes 24 connected to the display electrode 26 and the common electrode 28 in the display area VA via a plurality of terminals. The drive circuit 30 includes a driver that drives the display electrode 26 and the common electrode 28, a control circuit that controls the driver, and the like. The drive circuit 30 is electrically connected to a flexible printed circuit (FPC) 31 through a plurality of terminals.

  The flexible printed circuit board 31 includes a signal line for sending various signals to the drive circuit 30 and a power line for supplying power to the drive circuit 30. The flexible printed circuit board 31 is a flexible circuit board in which, for example, wiring is formed on a polyimide film base material. The flexible printed circuit board 31 is electrically connected to an external device (external circuit) including a power supply circuit via a plurality of terminals. The liquid crystal display device 10 displays characters in the display area VA by receiving power and control signals including image signals from an external device via the flexible printed circuit board 31 and the drive circuit 30.

  FIG. 1 shows an example of characters that can be displayed on the liquid crystal display device 10. The liquid crystal display device 10 can be applied to, for example, a camera finder. The character 32 that can be displayed on the liquid crystal display device 10 represents a focus point (rectangle) to be displayed on the camera finder, and the character 33 represents a frame indicating a plurality of focus point areas. The characters 32 and 33 are displayed by applying a voltage between the display electrode 26 and the common electrode 28. The display electrode 26 is processed into the same shape as the pattern of the characters 32 and 33, respectively.

[2] Operation of liquid crystal display device
FIG. 3 is a schematic diagram showing the alignment state of the liquid crystal layer 22 during operation of the liquid crystal display device. With reference to FIG. 3, the specific configuration of the liquid crystal layer 22 will be described first, and then the operation of the liquid crystal display device 10 will be described.

  The liquid crystal layer 22 includes a polymer layer 22A and a liquid crystal layer 22B. The liquid crystal layer 22B includes liquid crystal molecules 22C. More specifically, the liquid crystal layer 22 is made of polymer dispersed liquid crystal (PDLC) or polymer network liquid crystal (PNLC). The PDLC has a structure in which the liquid crystal 22B is dispersed in the polymer layer (polymer network) 22A. That is, the PDLC has a structure in which the liquid crystal 22B is phase-separated in the polymer layer 22A. Alternatively, the liquid crystal 22B in the polymer layer 22A may have a continuous phase.

  A photo-curing resin can be used as the polymer layer 22A. For example, PDLC irradiates a solution in which liquid crystal is mixed with a photopolymerizable polymer precursor (monomer) by irradiating ultraviolet rays, polymerizes the monomer to form a polymer, and the liquid crystal is dispersed in the polymer network. . As the liquid crystal 22B, for example, nematic liquid crystal having positive (positive) dielectric anisotropy is used. That is, when a voltage is not applied to the liquid crystal layer 22, the liquid crystal molecules 22C are randomly arranged in the polymer layer 22A, and when a voltage is applied to the liquid crystal layer 22, the liquid crystal molecules 22C stand in the electric field direction. (A state in which the long axis of the liquid crystal molecules 22C is directed in the electric field direction).

  Next, the operation of the liquid crystal display device 10 will be described. The display operation of the liquid crystal display device 10 is controlled by the drive circuit 30. The drive circuit 30 is electrically connected to the display electrode 26 and the common electrode 28, and applies a voltage between the display electrode 26 and the common electrode 28.

FIG. 3A is a diagram illustrating a scattering state of the liquid crystal layer 22, and FIG. 3B is a diagram illustrating a transmission state of the liquid crystal layer 22. In FIG. 3, a part of the liquid crystal layer 22 sandwiched between the display electrode 26 and the common electrode 28 is extracted and shown. The liquid crystal molecules 22C is represented by the spheroid optically (rotation in the ellipse long axis), the refractive index n _o of the size in the short-axis direction of the normal _light, the refractive index n of the diameter in the major axis direction is abnormal light _e .

  When no electric field is applied to the liquid crystal layer 22, that is, when the display electrode 26 and the common electrode 28 are set to the same voltage (for example, 0 V), the liquid crystal molecules 22C are randomly arranged. In this case, when white light is incident on the liquid crystal layer 22, the incident light is scattered and is observed as a white turbid state from the outside (white display).

On the other hand, when an electric field is applied to the liquid crystal layer 22, that is, when a voltage difference is applied between the display electrode 26 and the common electrode 28 (for example, a positive voltage is applied to the display electrode 26 and 0 V is applied to the common electrode 28), The major axis is oriented in the electric field direction (ie, the vertical direction). In this case, when the incident white light to the liquid crystal layer 22, (the direction perpendicular to the traveling direction) vibration direction of the light incident light so aligned to the refractive index n _o goes straight through the liquid crystal layer 22. For this reason, incident light is transmitted and observed as a transparent state from the outside (black display).

[3] Configuration of through hole 27
As described above, a through hole 27 is formed in the interlayer insulating film 25, and the connection electrode 26 </ b> A that electrically connects the wiring electrode 24 and the display electrode 26 is formed in the through hole 27. The taper part of the through hole 27 may become conspicuous during the transmission state. The taper portion is a part of the interlayer insulating film 25 including the inner wall of the through hole 27, and the cross section of the tapered portion is a right triangle region having the inner wall of the through hole 27 as a hypotenuse and the portion in contact with the surface of the wiring electrode 24 as the base. Point to. The reason why the tapered portion of the through hole 27 is noticeable will be described below.

[3-1] Apparent Length of Tapered Part FIG. 4 is a plan view of the through hole 27 in the liquid crystal display device 10 as viewed from above the display area. FIG. 5 is a cross-sectional view taken along line BB ′ of the through hole shown in FIG. In FIG. 5, the second substrate 21 and the common electrode 28 are omitted.

  As shown in FIG. 5, an interlayer insulating film 25 is formed on the wiring electrode 24 on the first substrate 20, and a display electrode 26 is further formed on the interlayer insulating film 25. The through hole 27 is a hole that is opened in the interlayer insulating film 25 and exposes a part of the wiring electrode 24. In the through hole 27, a connection electrode 26A for electrically connecting the wiring electrode 24 and the display electrode 26 is formed.

  The inner wall of the through hole 27 formed in the interlayer insulating film 25 is inclined with respect to the surface of the wiring electrode 24 as shown in FIG. At this time, an angle formed by the inner wall of the through hole 27 (the oblique side of the tapered portion 27A) and the surface of the wiring electrode 24 is referred to as a taper angle θ.

  Assuming that the bottom side of the taper portion 27A is a and the height is b, when the through hole 27 is viewed from above the display area VA, the apparent length of the bottom side of the taper portion 27A visually recognized by the observer is a ′. . This a 'is longer than a. This is because the oblique side of the tapered portion 27A is the interface between the liquid crystal layer 22 and the interlayer insulating film 25 (not considered because the thickness of the connection electrode 26A is sufficiently thin), and incident light is refracted at this interface. is there.

The apparent length a ′ of the bottom side of the tapered portion 27A can be calculated as follows. The incident angle of light entering the tapered portion 27A from the liquid crystal layer 22 is θ (same as the taper angle), the refraction angle is φ, the refractive index n _PN of the liquid crystal layer (polymer dispersed liquid crystal) 22 is 1.5, and the interlayer insulating film When the refractive index n _{INS of} 25 is 1.8 and the film thickness b of the interlayer insulating film 25 is 0.5 μm,
n _PN · sin θ = n _INS · sin φ (from Snell's law) (1)
a = b / tan θ (2)
a ′ = (a / cos θ) · sin (90 ° −φ) = a (cos φ / cos θ) (3)
It becomes. The display electrode 26 and the connection electrode 26A are sufficiently thinner than the liquid crystal layer 22 and the interlayer insulating film 25, and the refraction angle condition is omitted.

  FIG. 6 shows the values of φ, a, a ′ with respect to the taper angle θ when the film thickness of the interlayer insulating film 25 is 0.5 μm, and FIG. 7 shows the values of a, a ′ with respect to the taper angle θ. It can be seen that the apparent length a 'is longer than the actual length a of the bottom side of the tapered portion 27A. The difference increases as the taper angle θ increases. Therefore, it can be seen that the length of the bottom side of the tapered portion 27A of the through hole 27 is longer than the actual length and cannot be ignored.

[3-2] Visibility of apparent length of tapered part
Next, the result of examining the visibility of the tapered portion 27A of the through hole 27 will be described. Here, the apparent length a ′ that was not visually recognized by the observer was examined.

  FIG. 8 is a diagram showing the relationship between the apparent length a ′ of the bottom side of the tapered portion 27 </ b> A and the visibility of the through hole 27. When the observer actually sees the through hole 27 from above the display area VA, as shown in FIG. 8, when the apparent length a ′ of the bottom of the taper portion is longer than 1.5 μm, the taper of the through hole 27 is increased. It was found that the taper portion of the through hole 27 is not visually recognized when the portion is visually recognized reliably and the apparent length a ′ is shorter than 0.5 μm. That is, when the apparent length a ′ is longer than 1.5 μm, the tapered portion of the through hole 27 can be seen, and when the apparent length a ′ is shorter than 0.5 μm, the tapered portion of the through hole 27 cannot be seen. all right. Note that “visible / not visible” or “visible / invisible” described here is a result of a statistical examination, and a difference occurs depending on an observer.

  If this result is added to FIG. 7 described above, it will be as shown in FIG. 8 and 9, it can be seen that when the taper angle θ is 50 degrees or more, the apparent length a ′ can be made shorter than 0.5 μm, and the tapered portion of the through hole 27 can be prevented from being visually recognized. In addition, when the apparent length a ′ is 0.5 μm, it can be seen from FIG. 6 that the length a of the bottom side of the tapered portion 27A is about 0.42 μm. Therefore, if the bottom length a is 0.4 μm or less, the tapered portion of the through hole 27 can be prevented from being visually recognized. As described above, the film thickness of the interlayer insulating film 25 at this time is 0.5 μm.

  Further, the range in which the apparent length a ′ is 0.5 μm or more and 1.5 μm or less is a range in which the appearance is different depending on the observer, that is, a range in which the observer is visually recognized or not visually recognized.

[3-3] Taper angle of taper part
The taper angle θ at which the tapered portion of the through hole 27 is not visually recognized is as follows. From the condition that the tapered portion of the through hole 27 is not visually recognized, that is, the condition that the apparent length a ′ of the bottom side of the tapered portion is smaller than 0.5 μm (0 ≦ a ′ <0.5 μm), the taper angle θ is From equations (1), (2), (3)

And the taper angle θ is 90 degrees or less.

  Next, the taper angle θ when the film thickness b of the interlayer insulating film 25 was changed and the apparent length a ′ of the base of the tapered portion 27A was 0.5 μm was examined. FIG. 10 is a diagram illustrating the taper angle θ when the film thickness b of the interlayer insulating film 25 is changed.

  The interlayer insulating film 25 needs to maintain electrical insulation between the wiring electrode 24 and the display electrode 26 and to facilitate the formation of the through hole 27. For this purpose, the film thickness b of the interlayer insulating film 25 is preferably not less than 0.3 μm and not more than 0.9 μm. As shown in FIG. 10, when the film thickness b of the interlayer insulating film 25 is 0.3 μm or more and 0.9 μm or less, the taper angle θ when the apparent length a ′ of the bottom of the taper portion is 0.5 μm is It is 32.5 degrees or more and 86.8 degrees or less. Therefore, when the film thickness b of the interlayer insulating film 25 is 0.3 μm or more and 0.9 μm or less, the taper angle θ of the through hole 27 is set to 32 degrees or more and 90 degrees or less.

[3-4] Method for Controlling Taper Angle θ Next, a method for controlling the taper angle θ of the tapered portion of the through hole 27 will be described. In order to control the taper angle θ, the inclination of the inner wall of the through hole 27 (the oblique side of the tapered portion 27A) is controlled.

FIG. 11 is a cross-sectional view showing a process of forming a through hole 27 in the interlayer insulating film 25. Here, a process of forming taper angles θ _α , θ _β , and θ _γ (θ _α > θ _β > θ _γ ) is shown. In addition, the through hole 27 is actually opened until the wiring electrode 24 is exposed, but here, an example is shown in which the through hole 27 is opened halfway through the interlayer insulating film 25.

First, as shown in FIG. 11A, an interlayer insulating film 25, for example, a silicon nitride film is formed to a thickness of about 0.5 μm on the first substrate 20 and the wiring electrode 24 (not shown). The interlayer insulating film 25 is formed using, for example, SiH (eg, SiH ₄ ) and NH ₃ as main reaction gases by CVD (Chemical Vapor Deposition). The gas flow ratio (SiH / NH ₃ ) between SiH and NH ₃ at this time is α.

Next, a resist film 40 having an opening in the through hole 27 is formed on the interlayer insulating film 25 by photolithography. Subsequently, the interlayer insulating film 25 is etched by dry etching, for example, RIE (Reactive Ion Etching). Thus, as shown in FIG. 11 (b), through holes 27 taper angle is theta _alpha is formed. The taper angle theta _alpha in this case is about 90 degrees.

Next, the case where the through hole 27 having the taper angle θ _β smaller than the taper angle θ _α is formed will be described. First, as shown in FIG. 11C, an interlayer insulating film 25, for example, a silicon nitride film is formed to a thickness of about 0.48 μm on the first substrate 20 and the wiring electrode 24 (not shown). The interlayer insulating film 25 is formed by using, for example, SiH and NH ₃ as main reaction gases by CVD. The gas flow rate ratio between SiH and NH ₃ at this time is α as in the step shown in FIG.

Subsequently, an interlayer insulating film 25A, for example, a silicon nitride film is formed on the interlayer insulating film 25 to a thickness of about 0.02 μm. This interlayer insulating film 25A is formed by using, for example, SiH / NH ₃ as a main reaction gas by CVD, and the gas flow ratio of SiH and NH ₃ at this time is β smaller than α. That is, the flow rate of NH ₃ is larger than the gas flow rate ratio α. As a result, the interlayer insulating film (N-H rich silicon nitride film) 25A having a higher content of N (nitrogen) and H (hydrogen) than the interlayer insulating film 25 is laminated on the interlayer insulating film 25.

Further, a resist film 40 in which a portion of the through hole 27 is opened is formed on the interlayer insulating film 25A by photolithography. Subsequently, the interlayer insulating film 25A and the interlayer insulating film 25 are etched by dry etching, for example, RIE. Thus, as shown in FIG. 11 (d), the through-holes 27 taper angle is theta _beta is formed. At this time, the etching rate of the interlayer insulating film 25 </ b> A is faster than the etching rate of the interlayer insulating film 25. Due to the difference in the etching rate, the taper angle θ _β is smaller than θ _α .

Next, the case where the through hole 27 having the taper angle θ _γ smaller than the taper angle θ _β is formed will be described. First, as shown in FIG. 11E, an interlayer insulating film 25, for example, a silicon nitride film is formed to a thickness of about 0.48 μm on the first substrate 20 and the wiring electrode 24 (not shown). The interlayer insulating film 25 is formed by using, for example, SiH and NH ₃ as main reaction gases by CVD. The gas flow rate ratio between SiH and NH ₃ at this time is α as in the step shown in FIG.

Subsequently, an interlayer insulating film 25B, for example, a silicon nitride film is formed on the interlayer insulating film 25 to a thickness of about 0.02 μm. The interlayer insulating film 25B is formed by using, for example, SiH / NH ₃ as a main reaction gas by CVD, and the gas flow rate ratio of SiH and NH ₃ at this time is γ smaller than β. That is, the flow rate of NH ₃ is larger than the flow rate ratio β of the gas flow rate ratio γ. As a result, the interlayer insulating film (N-H rich silicon nitride film) 25B having a higher content of N (nitrogen) and H (hydrogen) than the interlayer insulating film 25A is stacked on the interlayer insulating film 25.

Further, a resist film 40 having an opening in the through hole 27 is formed on the interlayer insulating film 25B by photolithography. Subsequently, the interlayer insulating film 25B and the interlayer insulating film 25 are etched by dry etching, for example, RIE. Thus, as shown in FIG. 11 (f), through-holes 27 taper angle is theta _gamma is formed. At this time, the etching rate of the interlayer insulating film 25B is faster than the etching rate of the silicon nitride film 25A. Due to the difference in the etching rate, the taper angle θ _γ becomes smaller than θ _β .

  In the present embodiment, the taper angle θ of the through hole 27 can be controlled by the forming method as shown in FIGS. 11 (a) to 11 (f). For example, when the thickness of the interlayer insulating film 25 is 0.5 μm, the taper angle θ of the through hole 27 can be formed to be 50 degrees or more. Further, when the film thickness of the interlayer insulating film 25 is 0.3 μm or more and 0.9 μm or less, the taper angle θ of the through hole 27 can be formed to 32 degrees or more and 90 degrees or less.

[4] Effects of the embodiment
In the liquid crystal display device according to this embodiment, the apparent length of the bottom of the tapered portion of the through hole in the display area VA is set to a predetermined length, that is, a length shorter than 0.5 μm, so that the through hole tapers. The portion can be made difficult to visually recognize, in other words, the through hole can be made inconspicuous.

  In a liquid crystal display device having a polymer-dispersed liquid crystal layer, a display electrode is disposed on a wiring electrode on a substrate via an interlayer insulating film. The display electrode is electrically connected to the wiring electrode through a through hole. For this reason, when the apparent length of the bottom part of the tapered portion of the through hole is increased, the through hole is visually recognized. For example, when the through holes are densely packed, the tapered portions of the through holes in the display region are conspicuously visible in the transmissive state.

  Therefore, in the present embodiment, when the through hole formed in the interlayer insulating film is viewed through the liquid crystal layer, the length of the bottom side of the tapered portion of the through hole appears to be longer than the actual length. In order to shorten the apparent length a ′ of the bottom side, the taper angle of the through hole is set within a predetermined range. Specifically, the apparent length a ′ is set to 0.5 μm or less by determining the taper angle θ so that the formula (4) is satisfied and the taper angle θ is 90 degrees or less. To do. Thereby, the taper part of a through hole can be made difficult to visually recognize, ie, a through hole can be made inconspicuous. As a result, a liquid crystal display device capable of further improving display characteristics can be realized.

  Further, when the taper angle θ of the through hole is 90 degrees due to the manufacturing apparatus, manufacturing conditions or conductive material, the connection electrode (ITO) formed in the through hole is disconnected, and the wiring electrode and the display electrode are electrically connected. May not be connected. In such a case, the taper angle θ is determined so that the formula (4) is satisfied and the taper angle θ is smaller than 90 degrees. Thereby, disconnection of the connection electrode formed in the through hole can be prevented by making the taper angle θ smaller than 90 degrees. Furthermore, since the taper angle θ satisfies the formula (4), the through hole can be made inconspicuous. That is, it is possible to make the through-hole inconspicuous while ensuring the electrical connection by the connection electrode of the through-hole.

  In addition, the liquid crystal display device 10 according to the present embodiment can be applied to a pattern display type liquid crystal display device that displays characters and figures superimposed on a finder such as a camera. In addition, the liquid crystal display device 10 according to the present embodiment can be applied to a digital timepiece, light control glass, a liquid crystal display device capable of segment display, a liquid crystal display device capable of matrix display, and the like. In addition, the liquid crystal display device 10 of the present embodiment can be applied to various electronic devices that are used to display different images on a subject, background, and image.

  The present invention is not limited to the above embodiment, and can be embodied by modifying the constituent elements without departing from the scope of the invention. Further, the above embodiments include inventions at various stages, and are obtained by appropriately combining a plurality of constituent elements disclosed in one embodiment or by appropriately combining constituent elements disclosed in different embodiments. Various inventions can be configured. For example, even if some constituent elements are deleted from all the constituent elements disclosed in the embodiments, the problems to be solved by the invention can be solved and the effects of the invention can be obtained. Embodiments made can be extracted as inventions.

  DESCRIPTION OF SYMBOLS 10 ... Liquid crystal display device, 20 ... 1st board | substrate, 21 ... 2nd board | substrate, 22 ... Liquid crystal layer, 22A ... Polymer layer, 22B ... Liquid crystal layer, 22C ... Liquid crystal molecule, VA ... Display area (view area), 23 ... Sealing material, 24 ... wiring electrode, 25 ... interlayer insulating film, 26 ... display electrode, 27 ... through hole, 28 ... common electrode, 30 ... drive circuit, 31 ... flexible printed circuit board (FPC), 32, 33 ... character.

Claims (6)

First and second substrates disposed opposite to each other;
A polymer-dispersed liquid crystal layer sandwiched between the first and second substrates;
A wiring electrode provided on the first substrate;
An interlayer insulating film provided on the wiring electrode and having a through hole exposing a part of the wiring electrode;
A display electrode provided on the interlayer insulating film;
A connection electrode provided in the through hole and electrically connecting the wiring electrode and the display electrode;
A common electrode provided on the second substrate;
Comprising
When the refractive index of the liquid crystal layer is n _PN , the refractive index of the interlayer insulating film is n _INS , and the film thickness of the interlayer insulating film is b (μm), the inner wall of the through hole and the surface of the wiring electrode are The angle θ formed is
And a liquid crystal display device having an angle of 90 degrees or less.   The liquid crystal display device according to claim 1, wherein the angle θ is not less than 32 degrees and not more than 90 degrees.   3. The liquid crystal display device according to claim 1, wherein a thickness of the interlayer insulating film is not less than 0.3 μm and not more than 0.9 μm.   4. The length of the bottom side is 0.4 μm or less in a right-angled triangle having the inner wall of the through hole as a hypotenuse and the base of the surface of the wiring electrode as set forth in claim 1. A liquid crystal display device according to 1.   5. The liquid crystal display device according to claim 1, wherein the interlayer insulating film is made of silicon nitride.   6. The liquid crystal display device according to claim 1, wherein the polymer dispersed liquid crystal layer includes a polymer layer and a liquid crystal provided in the polymer layer.