JP2005134504A - Liquid crystal display element and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress a reduction in utilizing efficiencies of incident light and reflected light. <P>SOLUTION: A pair of electrodes 20a and 20b are provided on a driving circuit substrate 3 side. Thereby, light is made incident in a light controlling layer 4 without passing through a transparent electrode and the like and light reflected by the light controlling layer 4 is emitted without passing through the transparent electrode and the like. Thus, deterioration of incident light made incident in the light controlling layer 4 and reflected light reflected by the light controlling layer 4 by the transparent electrode and the like can be prevented and the reduction in light utilizing efficiency can be suppressed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a liquid crystal display element using a polymer network type liquid crystal which is a composite of a liquid crystal material and a transparent resin having a three-dimensional network structure as a liquid crystal device, and a method for manufacturing the same.

  In recent years, image displays (display devices) that are lighter and consume less power have been demanded for various displays that can be connected to televisions, computers, and the like, and liquid crystal display elements (LCDs) have been developed as flat displays that meet these requirements. : Liquid Crystal Display) is actively researched and developed.

  As a general liquid crystal display element, a liquid crystal display element using a twisted nematic mode (NT: Twist Nematic) in which the alignment direction of nematic liquid crystal molecules is twisted by 90 ° on the surface of a pair of opposing electrode substrates, For example, there is a liquid crystal display element using a super twist nematic (SNT: Super Twist Nematic) structure in which the alignment direction of nematic liquid crystal molecules is twisted between 180 ° and 300 ° on the surface of a pair of electrode substrates. In addition to these liquid crystal display elements, as a bright, high-contrast, inexpensive liquid crystal display element, for example, liquid crystal droplets are dispersed in a polymer by encapsulating liquid crystal molecules, and the polymer is converted into a film. Examples include a polymer dispersed liquid crystal display device (PDLC) having an optical layer (see Patent Document 1 and Patent Document 2).

In this polymer-dispersed liquid crystal display element, for example, when liquid crystal molecules encapsulated with polyvinyl alcohol or the like have a positive dielectric anisotropy in a thin layer, the liquid crystal molecules are aligned in the direction of the electric field in the presence of an electric field. When the liquid crystal has a refractive index n ₀ equal to the refractive index n _{p of the} polymer, transparency is exhibited. When the electric field is removed, the liquid crystal molecules return to a random arrangement, and the refractive index of the liquid crystal droplets deviates from n ₀ , so that the liquid crystal droplets scatter light at the boundary surface and block light transmission. Becomes cloudy.

  As for such a polymer dispersion type liquid crystal display element, for example, Patent Document 3 discloses a liquid crystal droplet dispersed in an epoxy resin, Patent Document 4 discloses a liquid crystal droplet dispersed in a special ultraviolet curable polymer, Patent Document 5 proposes a solution of a photocurable vinyl compound and a liquid crystal in which a light control layer is formed by utilizing phase separation of a liquid crystal substance accompanying photocuring of the photocurable vinyl compound. Yes.

However, in this polymer dispersion type liquid crystal display element, since liquid crystal molecules are dispersed in the polymer, when an electric field is applied, an electric field is applied to the liquid crystal droplets through the polymer, thereby changing the arrangement of the liquid crystal molecules. Requires a high driving voltage, and has disadvantages that impede various problems such as a slow reaction rate when the alignment of liquid crystal molecules changes. In addition, in order to achieve sufficient transparency when an electric field is applied, it is necessary to select each appropriately so that the refractive index n _{0 of the} liquid crystal and the refractive index n _{p of the} polymer are approximate. There is annoyance. Further, when performing a large display by multiplex driving utilizing the characteristics of a large-area device, there is no threshold voltage necessary to make it possible, and it is difficult to implement it. Furthermore, there are also problems such as matrix display, segment display method, and the like that have many restrictions on driving conditions and greatly restrict applications.

  As a liquid crystal display element that solves such a problem, there is a polymer network liquid crystal (PNLC) display element 101 shown in FIG. 11 that can suppress a driving voltage that changes the arrangement of liquid crystal molecules. It has been proposed (see Patent Document 6).

  This polymer network type liquid crystal display element 101 is a control comprising a liquid crystal material and a polymerizable and transparent organic resin between at least one pair of transparent substrates 102 provided with a pair of transparent electrodes 102a facing each other. A transparent resin 103b having a three-dimensional network structure is formed in a continuous layer of a liquid crystal material by interposing an optical layer forming material and polymerizing the polymerizable composition by irradiating the light control layer forming material with actinic rays or the like. In other words, the light control layer 103 in a state where the liquid crystal molecules 103a are interposed is arranged in the mesh of the transparent resin 103b having a three-dimensional network structure.

  In the polymer network type liquid crystal display element 101 having such a configuration, when the driving voltage for changing the arrangement of the liquid crystal molecules 103a is not applied to the light control layer 103, the alignment regulation of the transparent resin 103b having a three-dimensional network structure is performed. Due to the force, a plurality of liquid crystal molecules 103a of the light control layer 103 form a plurality of domains aligned in a certain direction, and the birefringence between the domains does not match because the alignment direction of the liquid crystal in each domain is random. The light incident from the transparent substrate 102 side is scattered by the light control layer 103 and emitted from the transparent substrate 102 side, that is, reflected. In addition, as shown in FIG. 12, the polymer network type liquid crystal display element 101 is applied between the pair of transparent electrodes 102a when a driving voltage for changing the arrangement of the liquid crystal molecules 103a is applied to the pair of transparent electrodes 102a. An electric field is generated in the thickness direction of the light control layer 4 interposed between the pair of substrates 102, and the alignment direction of the liquid crystal molecules 103a of the light control layer 103 becomes the electric field direction. Thereby, in the polymer network type liquid crystal display element 101, the birefringence between the liquid crystal molecules 103a aligned in the electric field direction is matched, and the light incident from the transparent substrate 102 side is applied to the pair of transparent electrodes 102a. The light control layer 103 is transmitted by the amount of light corresponding to the magnitude of the applied voltage.

  In this polymer network type liquid crystal display element, a driving voltage for changing to the arrangement of the liquid crystal molecules 103 a is directly applied to the liquid crystal molecules 103 a of the light control layer 103 as compared with the polymer dispersion type liquid crystal display element described above. In addition, the driving voltage that changes the alignment of the liquid crystal molecules 103a can be kept low, and the reaction speed when the alignment of the liquid crystal molecules 103a changes can be increased. Further, in this polymer network type liquid crystal display element 101, since it is possible to have a clear threshold voltage in the driving voltage that changes the arrangement of the liquid crystal molecules 103a in the light control layer 103, multiplex driving can be performed effectively. In addition, it can be effectively used for a matrix display method and a segment display method.

  However, in the polymer network type liquid crystal display element 101, when the light passes through the transparent electrode 102a on the light incident side of the pair of substrates 102 sandwiching the light control layer 103, the light transmittance of the transparent electrode 102a. Is 85% to 90%, the light that has been absorbed and deteriorated by the transparent electrode 102 a is incident on the light control layer 103. Further, in the polymer network type liquid crystal display element 101, the deteriorated light incident on the light control layer 103 is scattered and emitted from the substrate 102 on the light incident side, that is, incident on the light control layer 103. When the reflected light is reflected, the emitted light passes through the transparent electrode 102a again, so that the amount of light deteriorated to about 72% to 81% with respect to the light before entering the light control layer 103. The light utilization efficiency deteriorates.

  Further, when the polymer network type liquid crystal display element 101 is manufactured, it is necessary to form the transparent electrode 102a on each of the pair of substrates 102, which causes problems such as a decrease in manufacturing yield and an increase in manufacturing cost. Furthermore, in the polymer network type liquid crystal display element 101, since the transparent electrode 102a is interposed between the transparent substrate 102 on the light incident side and the light control layer 103, the substrate 102, the transparent electrode 102a, The visibility of the light reflected by the light control layer 103 is reduced or the display quality is deteriorated at the interface between the transparent electrode 102a and the light control layer 103.

JP-T 58-501631 US Pat. No. 4,435,047 JP-T61-502128 JP-A-62-2231 JP-A-63-271233 Japanese Patent No. 2853249

  The problem to be solved by the present invention is that light incident on the light control layer and light reflected by the light control layer deteriorate. Moreover, when manufacturing a liquid crystal display element, a yield falls and a manufacturing cost becomes high.

  A liquid crystal display element according to the present invention includes a first substrate, a second substrate disposed opposite to the first substrate and having light transparency, and between the first substrate and the second substrate. Provided with a light control layer having a liquid crystal material and a transparent resin having a three-dimensional network structure, and a pair of electrodes for applying an electric field to the light control layer is provided on the first substrate. It is a feature.

  In this liquid crystal display element, since a pair of electrodes for applying an electric field to the dimming layer is provided on the first substrate side, incident light from the second substrate side having optical transparency passes through the electrodes. The reflected light that is incident on the light control layer without being passed through and is scattered after entering the light control layer is emitted from the second substrate side to the outside without passing through the electrode. Therefore, in this liquid crystal display element, the incident light incident on the light control layer and the reflected light that is reflected by the light control layer are not absorbed or shielded by the electrode, so that a decrease in light utilization efficiency can be suppressed. .

  In addition, a liquid crystal display element according to the present invention includes a first substrate, a second substrate disposed opposite to the first substrate and having light transmission properties, and the first substrate and the second substrate. And a light control layer having a liquid crystal material and a transparent resin having a three-dimensional network structure, and electrodes for applying an electric field to the light control layer are provided on the first substrate and the second substrate, respectively. The light control layer is provided and has a region in contact with the second substrate.

  In this liquid crystal display element, since the light control layer has a region in contact with the second substrate, light incident from the side of the second substrate having light transparency to the region passes through the electrode. Instead, the light that is incident on the light control layer and reflected by the region of the light control layer that contacts the second substrate is emitted from the second substrate side without passing through the electrode. Therefore, in this liquid crystal display element, the incident light incident on the light control layer and the reflected light that is reflected by the light control layer are not absorbed or shielded by the electrode, so that a decrease in light utilization efficiency can be suppressed. .

  The method for manufacturing a liquid crystal display element according to the present invention includes a liquid crystal material and a three-dimensional network between a first substrate and a second substrate disposed opposite to the first substrate and having light transmittance. A method of manufacturing a liquid crystal display element in which a light control layer having a transparent resin with a structure is disposed, wherein a pair of electrodes for applying an electric field to the light control layer is formed on a first substrate. It is a feature.

  According to this method, incident light that is incident on the light control layer from the second substrate side that is light transmissive, or reflected light that is scattered by the light control layer and reflected by the light control layer is absorbed or shielded by the electrode. Thus, a liquid crystal display element in which a decrease in light use efficiency that is not caused can be suppressed can be manufactured.

  Further, according to this method, since the pair of electrodes can be collectively formed on the first substrate, the manufacturing process can be simplified, the manufacturing yield can be improved, and the manufacturing cost can be suppressed.

  The method for manufacturing a liquid crystal display element according to the present invention includes a liquid crystal material and a three-dimensional network between a first substrate and a second substrate disposed opposite to the first substrate and having light transmittance. A liquid crystal display element manufacturing method in which a light control layer having a transparent resin having a structure is disposed, and an electrode for applying an electric field to the light control layer is provided on each of the first substrate and the second substrate. It is characterized in that a region that contacts the second substrate is provided in the light control layer.

  In this method, the light incident on the second substrate side of the light control layer in the region contacting the second substrate or the light reflected from the region of the light control layer contacting the second substrate is reflected. However, it is possible to manufacture a liquid crystal display element in which a decrease in use efficiency of light that is not absorbed or shielded by the electrode is suppressed.

  According to the present invention, it is possible to obtain a liquid crystal display element having excellent utilization efficiency of incident light incident on the light control layer from the outside and reflected light obtained by reflecting the incident light on the light control layer. That is, the visibility of the reflected light reflected by the light control layer and the display quality can be improved.

  In addition, according to the present invention, the manufacturing process is simplified by collectively forming a pair of electrodes for applying an electric field to the dimming layer on the main surface of one substrate, so that the manufacturing yield is increased. The manufacturing cost can be reduced.

  Hereinafter, a liquid crystal display element to which the present invention is applied and a manufacturing method thereof will be described in detail with reference to the drawings. First, a polymer network type liquid crystal display element (hereinafter referred to as PNLC [Polymer Network Liquid Crystal] display element) 1 to which the present invention shown in FIG. 1 is applied will be described. Hereinafter, the PNLC display element 1 will be described as an active matrix type liquid crystal display element including a thin film transistor (hereinafter referred to as TFT [Thin Film Transistor]) for each pixel.

  The PNLC display element 1 includes a transparent substrate 2 and a drive circuit substrate 3 arranged to face each other, and a light control layer 4 having liquid crystal molecules 4 a and a mesh-like transparent resin 4 b between the transparent substrate 2 and the drive circuit substrate 3. And. Specifically, the PNLC display element 1 uses a polymer network type liquid crystal utilizing a light scattering opaque state and a transparent state for the light control layer 4 serving as a liquid crystal device.

  The transparent substrate 2 may be transparent, such as a glass substrate or a plastic substrate, and may be a flexible material such as a plastic film. The transparent substrate 2 is in close contact with the main surface of the light control layer 4 and functions as a protective film for protecting the light control layer 4.

  As shown in FIGS. 2 and 3, the drive circuit board 3 is, for example, a switching drive including a TFT 11 serving as a switching element and a capacitor 12 serving as an auxiliary capacitor that supplies electric power for generating an electric field in the dimming layer 4. A plurality of circuits 13 are formed in a matrix for each pixel 17a on a substrate 14 made of silicon, glass, quartz, plastic, or the like. A plurality of signal lines 15 electrically connected to the data electrodes of the respective TFTs 11 and scanning lines 16 electrically connected to the gate electrodes of the respective TFTs 11 are arranged on the substrate 14 in directions orthogonal to each other. The display area 17 corresponding to each pixel 17a is the vicinity where the signal line 15 and the scanning line 16 intersect. Further, outside these display regions 17, a signal driver 18 that applies a display voltage to each signal line 15 and a scan driver 19 that applies a selection pulse to each scan line 11 are formed as logic units. Note that the switching drive circuit 13 is generally manufactured by a higher withstand voltage process than that of the logic portion because the transistor is required to have a withstand voltage corresponding to the drive voltage of the light control layer 4.

On the substrate 14, as shown in FIG. 3, a plurality of pairs of electrodes 20a and 20b are formed in a matrix for each pixel. The pair of electrodes 20a and 20b is formed in the in-plane direction of the substrate 14 by a transparent conductive material such as ITO (Indium-Tin Oxide) which is a solid solution material of tin oxide (SnO ₂ ) and indium oxide (In ₂ O ₃ ). It is installed side by side. One of the pair of electrodes 20a and 20b is electrically connected to the signal line 15 via each TFT 11, and the other is connected to the common electrode 21 connected to the ground or the like via the capacitor 12. Here, for convenience, the description will be made assuming that the electrode 20 a is connected to the signal line 15 and the electrode 20 b is connected to the common electrode 21.

  The pair of electrodes 20a and 20b applies the power supplied from the signal line 15 to the light control layer 4 in the region located between the electrodes 20a and 20b as a driving voltage for changing the arrangement of the liquid crystal molecules. . That is, as shown in FIG. 4, the pair of electrodes 20 a and 20 b applies an electric field in a direction substantially orthogonal to the thickness direction of the light control layer 4 to the light control layer 4 by being supplied with a drive voltage.

  The pair of electrodes 20a and 20b formed on the substrate 14 has a thickness of about 50 to 500 nm. Here, the pair of electrodes 20a and 20b has been described as a transparent electrode. However, the present invention is not limited to this. For example, aluminum (Al), specifically, copper (Cu) used for wiring in an LSI process is used. ) And silicon (Si) added to the light control layer 4 with a function of reflecting the light incident from the light control layer 4 side. And a function of applying a drive voltage. Further, a multilayer film such as a dielectric mirror may be laminated on the Al film in order to increase the reflectance.

  As shown in FIG. 1, the light control layer 4 is a liquid crystal device using a light scattering opaque state and a transparent state in which a network-like transparent resin 4b having a three-dimensional network structure is formed in a continuous layer of a liquid crystal material. That is, the light control layer 4 is a so-called polymer network type liquid crystal in which the liquid crystal molecules 4a are interposed in the mesh of the network-like transparent resin 4b. Specifically, the polymer network type liquid crystal induces an irregular state of the liquid crystal molecules 4a due to the network-like transparent resin 4b in the liquid crystal layer, and scatters light, thereby expressing “whiteness” similar to paper or the like. In this state, when an electric field is applied by the pair of electrodes 20a and 20b, the liquid crystal molecules 4a are aligned in the direction of the electric field and become transparent. The polymer network type liquid crystal uses a state of “whiteness” and “transparency” for display, for example, a liquid crystal device that does not require a backlight, a polarizing plate, an alignment process, etc. This is a direct-view reflective liquid crystal element suitable for portable devices.

  The light control layer 4 made of a polymer network type liquid crystal has a preferable configuration in that the liquid crystal molecules 4a and the network-like transparent resin 4b constituting the liquid crystal device utilizing the light scattering opaque state and the transparent state are compatible. Further, display characteristics such as lower voltage drivability, higher resistance value, or higher contrast ratio can be improved, and the memory phenomenon can be reduced to achieve more uniform display of white turbidity. In other words, the light control layer 4 is a liquid crystal device that satisfies characteristics required for a matrix display method, for example. In addition, when the light control layer 4 is formed as a polymer network type liquid crystal, a transparent resin 4b having a substantially uniform size is irradiated by irradiating a resin material described later with ultraviolet light having an appropriate light intensity. Is formed in the liquid crystal phase and becomes a liquid crystal device having a driving voltage having a clear threshold and steepness, and time-division driving is possible.

  Next, a manufacturing process of the PNLC display element 1 having the above configuration will be described. In the following description of the manufacturing process, description of parts that are not directly related to the present invention, such as the capacitor 12, is omitted. When the PNLC display element 1 is manufactured, first, one or more of tantalum, aluminum, chromium, and the like are formed on the main surface of the substrate 14 made of, for example, silicon, glass, quartz, plastic, or the like that serves as the base of the drive circuit substrate 3. A conductive metal made of seed is formed into a thin film by sputtering or the like, and a scanning line 16 or a common electrode 21 is formed by applying a photolithographic technique to the metal foil. Although the substrate 14 has been described as a rigid substrate here, the present invention is not limited to this, and for example, a flexible substrate made of plastic or the like can be used as the substrate 14.

  Next, on the main surface of the substrate 14, an interlayer insulating film 22 made of, for example, silicon nitride that prevents the scanning line 16 and the common electrode 21 from being short-circuited with the signal line 15 covers the scanning line 16 and the common electrode 21. The film is formed by plasma CVD (Chemical Vapor Deposition) method or the like.

Next, an undoped amorphous silicon is formed by plasma CVD, for example, at a predetermined position on the interlayer insulating film 22, specifically, at a position where the TFT 11 of each pixel 17a arranged in a matrix is disposed. A semiconductor film in which a film and an n ⁺ amorphous silicon film are sequentially stacked is formed.

  Next, a conductive metal such as titanium is thinly formed on the interlayer insulating film 22 by sputtering or the like, and a signal line 15 substantially orthogonal to the scanning line 16 is formed by applying a photolithographic technique to the metal foil. To do. At this time, a photolithographic method is applied to the conductive metal for forming the signal line 15 at a position where the TFT 11 is disposed, that is, immediately above the semiconductor film, so that one end is connected to the signal line 15 and substantially. A signal electrode line is formed at the same time as the signal line 15 by dividing the central portion and exposing the lower semiconductor film. As a result, the TFT 11 including the semiconductor film and the signal electrode line is formed on the interlayer insulating film 22.

  Next, at a position corresponding to each pixel 17a on the interlayer insulating film 22, an electrode 20a connected to the other end of the signal electrode line and an electrode 20b connected to the common electrode 21 via the capacitor 12 are sputtered, for example. The ITO film formed by the method or the like is collectively formed by applying a photolithographic technique. The pair of electrodes 20a and 20b formed in this way are transparent electrodes arranged in parallel in the in-plane direction of the substrate 14 in the pixel 17a. The electrode 20b is connected to the capacitor 12 by an interlayer connector that penetrates the interlayer insulating film 22 made of a conductive metal such as a via hole.

  Next, a passivation film made of silicon nitride, silicon oxide or the like is formed on the interlayer insulating film 22 by, for example, a plasma CVD method so as to cover the TFT 11 and the pair of electrodes 20a and 20b. In this manner, the drive circuit substrate 3 including the TFT 11 and the pair of electrodes 20a and 20b is formed for each of the pixels 17a arranged in a matrix on the substrate 14.

  Next, on the main surface of the drive circuit board 3 on which the pair of electrodes 20a and 20b are provided, the transparent substrate 2 is disposed on the main surfaces of the substrates 2 and 3 through spacers such as plastic beads having a diameter of about 20 μm. It arrange | positions so that a surface may oppose. And the edge part of the board | substrates 2 and 3 which main surfaces oppose is sealed with sealing agents, such as an adhesive agent, and the space part into which a light control layer forming material is inject | poured in the latter process between the board | substrates 2 and 3 Form. At this time, the space between the substrates 2 and 3 is sealed to form an injection port for allowing the light control layer forming material to be injected into a part of the sealant. In addition, a space part is determined by the diameter of the bead which becomes the space | interval of the board | substrates 2 and 3 as a spacer. This interval is the thickness of the light control layer 4.

  Next, in the space formed between the substrates 2 and 3, the liquid crystal material described above from the injection port provided in a part of the sealing agent, the transparent resin material described above, and a polymerization initiator as an optional component, etc. The light control layer forming material in which is uniformly dispersed is injected. Next, the injection port is sealed with the same material as the sealant, and the light control layer forming material injected into the space is sealed in the space formed between the substrates 2 and 3.

  Next, polymerization energy for polymerizing the transparent resin material in the light control layer forming material, such as irradiating ultraviolet light to the light control layer forming material sealed in the space formed between the substrates 2 and 3. Is polymerized so that the transparent resin in the light control layer forming material becomes a network transparent resin 4b having a three-dimensional network structure, and the light control layer 4 is formed. That is, a polymer network type liquid crystal having a structure in which a network-like transparent resin 4b is formed in a continuous layer of a liquid crystal material as a light control layer 4 to be a liquid crystal device is formed between the substrates 2 and 3. In this manner, the PNLC display element 1 having the display area 17 that includes a plurality of pixels 17a arranged in a matrix is manufactured.

  In the PNLC display element 1 manufactured in this way, when a driving voltage for changing the arrangement of the liquid crystal molecules 4a is not applied between the pair of electrodes 20a and 20b arranged in the pixel 17a, a three-dimensional network shape is formed. A plurality of liquid crystal molecules 4a in the light control layer 4 are aligned in a certain direction due to the alignment regulating force by the network-like transparent resin 4b having a structure, and the alignment direction of the liquid crystal in each domain is random. Therefore, the light control layer 4 scatters the incident light from the transparent substrate 2 side and emits it from the transparent substrate 2 side, that is, reflects it. On the other hand, in the PNLC display element 1, when a driving voltage for changing the arrangement of the liquid crystal molecules 4a is applied between the pair of electrodes 20a and 20b, the pair of electrodes 20a and 20b are in the plane of the substrate 14 of the driving circuit board 3. Since the electrodes are arranged side by side, an electric field in a direction substantially orthogonal to the thickness direction of the light control layer 4 is generated between the pair of electrodes 20a and 20b. Thereby, in the PNLC display element 1, when a predetermined drive voltage is applied between the pair of electrodes 20a and 20b, the alignment direction of the liquid crystal in the domain formed by the liquid crystal molecules 4a in the light control layer 4 is the electric field. Similarly, since the birefringence difference between the domains formed by the liquid crystal molecules 4a is reduced in a direction substantially orthogonal to the thickness direction of the light control layer 4, incident light from the transparent substrate 2 side is a pair of The light control layer 4 is transmitted according to the voltage value applied to the electrodes 20a and 20b. That is, in the PNLC display element 1, the light transmittance of the light control layer 4 increases as the drive voltage applied to the pair of electrodes 20a and 20b increases.

  In this PNLC display element 1, since the liquid crystal device is driven by an electric field in a direction substantially orthogonal to the thickness direction of the light control layer 4 generated by the pair of electrodes 20a and 20b, the substrate on the light incident side as in the prior art It is not necessary to form a transparent electrode or the like, and light that has passed through only the transparent substrate 2 is incident on the light control layer 4 and light reflected by the light control layer 4 is transmitted only through the transparent substrate 2 and is emitted to the outside. Is done. Thereby, in the PNLC display element 1, the fall of the utilization efficiency of the incident light from the transparent substrate 2 side and the reflected light which this incident light scattered in the light control layer 4 is suppressed, and the visibility and display quality of reflected light are suppressed. Can be improved.

  In this PNLC display element 1, since a pair of electrodes 20a and 20b for generating an electric field in the light control layer 4 can be formed at the same time on the drive circuit substrate 3 in the same process, the electrodes for generating an electric field as in the prior art are provided on the drive substrate. In addition, the manufacturing process can be simplified and the manufacturing yield can be improved, and the manufacturing cost can be reduced, without forming them separately on the counter substrate and the like.

  In the PNLC display element 1, for example, a plastic flexible substrate is used for the transparent substrate 2 and the substrate 14 of the drive circuit substrate 3, so that the entire device can be flexible.

  Here, white light is incident on the display area 17 of the PNLC display element 1 from a direction inclined at an angle of 45 ° with respect to the main surface of the transparent substrate 2, and the amount of reflected light reflected by the light control layer 4 is changed to that of the transparent substrate 2. Reading was performed with a detector having a light receiving element arranged substantially parallel to the main surface, and the amount of reflected light relative to the amount of incident light, so-called reflectance, was measured. Here, as shown in FIGS. 5A and 5B, an electric field is efficiently generated by the drive voltage applied to the pair of electrodes 20a and 20b arranged in parallel on the main surface of the substrate 14. In order to achieve this, a pair of electrodes 20a and 20b in which a plurality of protruding electrodes project from the base end in a direction in which the pair of electrodes 20a and 20b face each other are used, and one of the pair of electrodes 20a and 20b The other protruding electrode was arranged between them. Specifically, a pair of electrodes 20a and 20b formed in a comb-teeth shape is used, and the comb-teeth portions of the pair of electrodes 20a and 20b are arranged side by side, that is, the other comb-teeth is arranged between the one comb-teeth. Thus, the distance between the pair of electrodes 20a and 20b was reduced. Thereby, as shown in FIG. 5B, an electric field in a direction substantially perpendicular to the thickness direction of the light control layer 4 is generated between the adjacent comb teeth as shown in FIG. 5B. An electric field can be efficiently applied to the layer 4.

And as the samples 1 to 3 for measuring the reflectance, the distance from the base end of the comb teeth to the tip and the width L of the comb teeth are made constant, and the distance D between adjacent comb teeth is changed as shown in Table 1, The same method as the manufacturing method described above for the PNLC display element 1 in which the thickness of the light control layer 4 is 20 μm, the resistance of the pair of electrodes 20a and 20b is 10 Ω / cm ^2, and the thickness of the pair of electrodes 20a and 20b is 200 nm. Manufactured with.

  Moreover, as a sample 4 to be compared with the samples 1 to 3, instead of the pair of electrodes 20a and 20b arranged in parallel on the main surface of the substrate 14, the main surfaces of the driving circuit substrate and the transparent substrate facing each other as in the past. A PNLC display element was manufactured in the same manner as Samples 1 to 3 except that a transparent substrate having the same size as that of the pixel was formed.

  The measurement results of the reflectance of Sample 1 to Sample 4 are shown in FIGS. In this measurement, measurement was performed for a case where a drive voltage was not applied to the pair of electrodes 20a and 20b and a case where a 60 Hz pulsed alternating current was applied to the pair of electrodes 20a and 20b as the drive voltage. Table 2 shows the reflectance at an external light wavelength of 550 nm.

  From the evaluation results shown in FIGS. 6 and 7 and Table 2, in the samples 1 to 3 in which the pair of electrodes 20a and 20b are provided on the main surface of the substrate 14 in the drive circuit substrate 3, the drive circuit substrate is conventionally provided. In addition, it can be seen that the reflectance is higher than that of the sample 4 in which the transparent substrate having the same size as the pixel is formed on the opposing main surface of the transparent substrate.

  In sample 4, the light incident on the light control layer is absorbed and deteriorated when passing through the transparent electrode, and the light reflected by the light control layer is emitted through the transparent electrode. Is also absorbed by the transparent electrode and deteriorates. Thereby, in the sample 4, the utilization efficiency of incident light and reflected light deteriorates, and the reflectance decreases.

  On the other hand, in Samples 1 to 3, since the electrode for applying an electric field to the light control layer 4 is not provided on the transparent electrode 2 side, light incident on the light control layer 4 is absorbed by the transparent electrode, for example. In addition, since the light reflected from the light control layer 4 is emitted through the transparent electrode without being deteriorated, a decrease in utilization efficiency of incident light and reflected light is suppressed, and the reflectance is reduced. Can be bigger. In Samples 1 to 3, the reflectance increases as the distance D between adjacent comb teeth increases. This is because the main surface of the substrate 14 under the pair of electrodes 20a and 20b is exposed as the distance D between the adjacent comb teeth increases, specifically, the main surface of the substrate 14 other than the light control layer 4. This is because of the reflection. Therefore, the reflectance can be further increased by using a pair of electrodes 20a and 20b in which a multilayer film such as a dielectric mirror is laminated on an Al film.

  In addition, although the case where the pair of electrodes 20a and 20b used for Sample 1 to Sample 3 protrudes at substantially right angles from the base end toward the opposite electrode has been described here, such an electrode shape is used. As shown in FIG. 8, for example, a pair of electrodes 20 a and 20 b have the same function and effect even when the pair of electrodes protrudes in an oblique direction from the base end toward the opposite electrode. Can be obtained.

  In the above, in the drive circuit substrate 3, the pair of electrodes 20a and 20b are formed on the interlayer insulating film 22 provided on the front surface of the substantially flat substrate 14, but the present invention is not limited to such a shape. As shown in FIG. 9, for example, by forming the interlayer insulating film 22 between the pair of electrodes 20a and 20b, an effect of further reducing the driving voltage can be obtained in addition to the above-described effects. Specifically, by not forming the interlayer insulating layer 22 between the pair of electrodes 20a and 20b, a recess 23 that is recessed toward the drive circuit board 3 is formed between the pair of electrodes 20a and 20b. The light control layer 4 is formed. Thereby, in the PNLC display element 1, not only the electric field generated on the transparent substrate 2 side with reference to the pair of electrodes 20a and 20b but also the inside of the recess 23, specifically, the drive circuit board 3 with reference to the pair of electrodes 20a and 20b. An electric field can also be generated on the side. Therefore, the electric field utilization efficiency is improved because an electric field substantially perpendicular to the thickness direction of the light control layer 4 generated on the transparent substrate 2 side and the drive circuit substrate 3 side can be applied to the light control layer 4 with reference to the pair of electrodes 20a and 20b. The driving voltage applied to the pair of electrodes 20a and 20b can be suppressed.

  In the above description, the pair of electrodes 20a and 20b for generating an electric field is formed on the drive circuit board 3 side. However, the present invention is not limited to this. For example, as shown in FIG. 20b can be formed on the main surface of the transparent substrate 2 facing the light control layer 4. Here, for convenience, the electrode 20a connected to the signal line 15 among the pair of electrodes 20a and 20b is defined as the electrode 20a connected to the signal line 15, and the electrode formed on the transparent substrate 2 is connected to the common electrode 21. The electrode 20b will be described.

  In this case, the electrode 20b formed on the transparent substrate 2 side is formed as a transparent electrode made of at least an ITO film or the like, and as much as possible in order to prevent light incident on the light control layer 4 from being absorbed by the transparent electrode. It is preferable to form small and thin. That is, in this PNLC display element 1, the light control layer 4 is provided with a region in contact with the transparent substrate 2 surrounded by a broken line in FIG. 10, in other words, a region A that does not face the electrode 20b formed on the transparent electrode 4 side. Thereby, in the PNLC display element 1, at least the light incident on the region A from the transparent substrate 2 side is incident without passing through the electrode 20b, and the light reflected by the region A is emitted outside without passing through the electrode 20b. Therefore, in the region A, there is no deterioration of incident light and reflected light by the electrode 20b, and a decrease in light use efficiency can be suppressed. Therefore, in the PNLC display element 1, when the transparent electrode is also formed on the transparent substrate 2 side, the region A that contacts the transparent substrate 2 of the light control layer 4 is made as large as possible with respect to the pixel 17a, so that incident light or A reduction in the utilization efficiency of the reflected light can be suppressed, and the visibility and display quality of the reflected light can be improved.

  Next, the material constituting the polymer network type liquid crystal used for the light control layer 4 of the PNLC display element 1 described above, the formation method thereof, and the like will be described in more detail.

  In the light control layer 4 made of polymer network type liquid crystal, the liquid crystal material does not need to be a single liquid crystal compound, and a mixture containing two or more kinds of liquid crystal compounds and substances other than the liquid crystal compounds. A material that is generally recognized as a liquid crystal material in this technical field is used, and those having a positive dielectric anisotropy are preferred.

  Examples of the liquid crystal material interposed in the light control layer 4 in the state of the liquid crystal molecules 4a include nematic liquid crystal, smectic liquid crystal, and cholesteric liquid crystal, and one or more of these are used, and nematic liquid crystal is particularly preferable. . As a nematic liquid crystal, the dielectric anisotropy (hereinafter referred to as Δε) is 8 or more and the birefringence (hereinafter referred to as Δn) has a dielectric constant anisotropy of 0.8 or more. The nematic liquid crystal is preferably a nematic liquid crystal having Δε of 10 or more and Δn of 0.2 or more. Δn is preferably as large as possible in order to increase white turbidity, increase contrast, and increase steepness. In addition, in order to improve the performance of the liquid crystal molecules 4b, the above-described liquid crystal material may contain, for example, one or more kinds of cholesteric liquid crystal, chiral nematic liquid crystal, chiral smectic liquid crystal, and chiral compounds.

  Specifically, the liquid crystal material is preferably a blended composition comprising one or more compounds selected from the following compound group, and the characteristics of the liquid crystal material, that is, the phase transition temperature, melting point, viscosity, Δn, Δε of the liquid crystal material. Can be appropriately selected, blended and used for the purpose of further improving solubility with the polymerizable composition and the like. Liquid crystal materials include benzoate, cyclohexyl carboxylate, biphenyl, terphenyl, phenylcyclohexane, biphenylcyclohexane, pyrimidine, pyridine, dioxane, cyclohexanecyclohexane ester, cyclohexylethane, Various liquid crystal compounds such as alkenyl and alkenyl are used. Specifically, for example, 4-substituted benzoic acid 4′-substituted phenyl ester, 4-substituted cyclohexanecarboxylic acid 4′-substituted phenyl ester, 4-substituted cyclohexanecarboxylic acid 4′-substituted biphenyl ester, 4- (4-substituted) Cyclohexanecarbonyloxy) benzoic acid 4′-substituted phenyl ester, 4- (4-substituted cyclohexyl) benzoic acid 4′-substituted phenyl ester, 4- (4-substituted cyclohexyl) benzoic acid 4′-substituted cyclohexyl ester, 4-substituted 4′-substituted biphenyl, 4-substituted phenyl 4′-substituted cyclohexane, 4-substituted 4 ″ -substituted terphenyl, 4-substituted biphenyl 4′-substituted cyclohexane, 2- (4-substituted phenyl) 5-substituted pyrimidine, etc. Can be mentioned.

  As the transparent resin material for forming the network-like transparent resin 4b, a material that forms a three-dimensional network structure in a continuous layer of a liquid crystal material, such as a polymer-forming monomer or oligomer, and exhibits light transmittance is used. The transparent resin material contains a polymerization initiator as necessary.

  Examples of the polymer-forming monomer include styrene, chlorostyrene, α-methylstyrene, divinylbenzene, and the like. These monomers are methyl, ethyl, propyl, butyl, amyl, 2-ethylhexyl, octyl, nonyl, dodecyl, hexadecyl. , Octadecyl, cyclohexyl, benzyl, methoxyethyl, butoxyethyl, phenoxyethyl, allyl, methallyl, glycidyl, 2-hydroxyethyl, 2-hydroxypropyl, 3-chloro-2-hydroxypropyl, dimethylaminoethyl, diethylaminoethyl, etc. A group substituted with a substituent such as acrylate, methacrylate or fumarate having a group is used.

  Examples of the polymer-forming monomer include the above-described monomers such as ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, 1,3-butylene glycol, tetramethylene glycol, hexamethylene glycol, neopentyl glycol, trimethylolpropane, Those substituted with a substituent such as mono (meth) acrylate or poly (meth) acrylate such as glycerin and pentaerythritol can be used. Furthermore, the above-mentioned monomers are, for example, vinyl acetate, vinyl butyrate or vinyl benzoate, acrylonitrile, cetyl vinyl ether, limonene, cyclohexene, diallyl phthalate, diallyl isophthalate, 2-, 3- or 4-vinyl pyridine, acrylic acid, methacrylic acid. Diol of diol obtained by adding 2 mol or more of ethylene oxide or propylene oxide to 1 mol of neopentyl glycol, acrylamide, methacrylamide, N-hydroxymethyl acrylamide or N-hydroxyethyl methacrylamide and their alkyl ether compounds Di or tri (meth) acrylate of triol obtained by adding 3 mol or more of ethylene oxide or propylene oxide to 1 mol of meth) acrylate and trimethylolpropane Di- (meth) acrylate of diol obtained by adding 2 mol or more of ethylene oxide or propylene oxide to 1 mol of bisphenol A, 1 mol of phenyl isocyanate or 1-mol of n-butyl isocyanate Reaction products of poly (meth) acrylate of dipentaerythritol, poly (meth) acrylate of tris- (hydroxyethyl) -isocyanuric acid, poly (meth) acrylate of tris- (hydroxyethyl) -phosphoric acid, di- ( Hydroxyethyl) -dicyclopentadiene substituted with a substituent such as mono (meth) acrylate or di (meth) acrylate can be used.

  Examples of the polymer-forming oligomer include caprolactone-modified hydroxypivalic acid and ester neopentyl glycol diacrylate.

  Examples of the polymerization initiator contained as necessary include 2-hydroxy-2-methyl-1-phenylpropan-1-one ("Darocur 1173" manufactured by Merck & Co.), 1-hydroxycyclohexyl phenyl ketone (Ciba-Geigy). “Irgacure 184”), 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one (“Darocur 1116” manufactured by Merck), benzyldimethyl ketal (“Irgacure” manufactured by Ciba Geigy) 651 "), 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropanone-1 (" Irgacure 907 "manufactured by Ciba-Geigy), 2,4-diethylthioxanthone (manufactured by Nippon Kayaku Co., Ltd.) “Kayacure DEXT”) and ethyl p-dimethylaminobenzoate (“KAICURE” manufactured by Nippon Kayaku Co., Ltd.) PA "), a mixture of isopropylthioxanthone (" Kantacure ITX "manufactured by Ward Prekinsop) and ethyl p-dimethylaminobenzoate, and the like, which are liquid 2-hydroxy-2-methyl-1 -Phenylpropan-1-one is particularly preferred in terms of compatibility with liquid crystal materials, polymer-forming monomers or oligomers.

  The light control layer 4 having the above configuration is formed as follows. When the light control layer 4 is formed, between the substrates 2 and 3 in a state where the main surface of the transparent substrate 2 and the main surface on which the pair of electrodes 20a and 20b of the drive circuit substrate 3 are formed are opposed to each other. The liquid crystal material described above, the transparent resin material described above, and a light control layer forming material in which a polymerization initiator or the like is dispersed almost uniformly as an optional component are interposed, the polymerization light is supplied to the light control layer forming material, and transparent By polymerizing and curing the resin material, the light control layer 4 in which the network-like transparent resin 4b having a three-dimensional network structure is formed in the continuous layer of the liquid crystal material is formed. In addition, the range of 60 to 95 weight% is preferable and, as for content of the liquid crystal material in the light control layer forming material, the range of 70 to 90 weight% is especially preferable. Moreover, a crosslinking agent, a chain transfer agent, an antioxidant, a dye, an alignment material, a light stabilizer, and the like can be added to the light control layer forming material as necessary.

  In order to interpose the light control layer forming material between the substrates 2 and 3, this light control layer forming material may be injected between the substrates 2 and 3, but a pair of the main surface of the transparent substrate 2 and the drive circuit substrate 3 is used. The light control layer forming material is applied almost uniformly to one of the main surfaces on which the electrodes 20a and 20b are formed using an appropriate solution coating machine, spin coater, etc. The main surface of the uncoated substrate may be overlapped and adhered to the coated surface. Moreover, after applying the light control layer forming material to the main surface of one substrate, the transparent resin material in the light control layer forming material is polymerized and cured to form the light control layer 4, and the other light control layer 4 is formed on the other surface. Alternatively, the substrates may be bonded together. In the case of this method, it is preferable to polymerize the transparent resin material under anaerobic conditions such as performing a polymerization step in a nitrogen atmosphere.

  The polymerization energy for polymerizing the transparent resin material is not particularly limited as long as the transparent resin material in the light control layer forming material is appropriately polymerized to form a three-dimensional network structure, for example, radiation such as ultraviolet rays and electron beams. , Heat and the like.

In particular, a method of polymerizing the transparent resin material by irradiating the light control layer forming material interposed between the substrates 2 and 3 from the transparent substrate 2 side is preferable. In the polymerization of a transparent resin material in a liquid crystal material by ultraviolet irradiation, the light irradiation intensity and the irradiation amount also need to exceed a certain level, but this depends on the reactivity of the transparent resin material and the type and concentration of the polymerization initiator. By selecting an appropriate light intensity, it is possible to form a three-dimensional network structure and make the mesh size substantially uniform. Furthermore, as a method of irradiating ultraviolet rays, irradiating ultraviolet rays having substantially uniform light intensity in a plane is because the transparent resin material interposed between the substrates 2 and 3 is irradiated with ultraviolet rays having substantially uniform light intensity. Polymerization of the transparent resin material proceeds substantially uniformly, and is effective in forming the mesh-like transparent resin 4b in which the mesh size is substantially uniform. Specifically, when the distance between the substrates 2 and 3, that is, the thickness of the light control layer 4 to be formed is 5 μm to 30 μm, 10 mJ / cm ² at a light intensity of at least 3 mW / cm ² or more from the transparent substrate 2 side. It is necessary to irradiate the above-mentioned irradiation amount of ultraviolet rays for about 5 seconds to 10 seconds.

  Further, the temperature at the time of polymerizing the transparent resin material is preferably as low as possible. When the temperature at the time of polymerization is high, the polymerization rate is too high so that the degree of polymerization does not increase, the white turbidity of the light control layer 4 is poor, it becomes transparent even in a non-voltage state, and the drive voltage becomes high. Resulting in. The temperature at which such a defect occurs is equal to or higher than the temperature of the phase transition point of the liquid crystal material, for example.

  According to the present invention, in addition to the active matrix type liquid crystal display element described above, the present invention is also used for a passive matrix type liquid crystal display element using a polymer network type liquid crystal as a liquid crystal device, a segment type liquid crystal display element, or the like. Is possible. Further, as a device provided with a liquid crystal display element, for example, it can be used for a display device for displaying advertisements, time, etc., a projection display device, and the like. Further, it can be used for a thin, light, foldable display device, so-called electronic paper, and the like.

It is a figure which shows typically the polymer network type liquid crystal display element to which this invention is applied. It is a schematic diagram which shows the structure of the drive circuit board | substrate and switching drive circuit of the polymer network type liquid crystal display element. It is a top view which shows a drive circuit board of the polymer network type liquid crystal display element partially through. It is a schematic diagram which shows the state of the electric field which arises in the polymer network type liquid crystal display element. 2A and 2B show a pair of electrodes formed in a comb-teeth shape of the polymer network type liquid crystal display element, in which FIG. 1A is a plan view and FIG. 1B schematically shows an electric field generated between the pair of electrodes. It is. It is the characteristic view which showed the reflectance of the light control layer when the drive voltage is not applied to a pair of electrode. It is the characteristic figure which showed the reflectance of the light control layer when a drive voltage is applied to a pair of electrodes 10V. It is a top view which permeate | transmits and shows another example of the drive circuit board | substrate of the polymer network type liquid crystal display element partially. It is a schematic diagram which shows the state of the electric field produced in the other example of the polymer network type liquid crystal display element. It is a schematic diagram which shows the other example of the polymer network type liquid crystal display element, and shows the state of the electric field produced between electrodes. It is a figure which shows the conventional polymer network type liquid crystal display element typically. It is a schematic diagram which shows the state of the electric field which arises in the polymer network type liquid crystal display element.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Polymer network type liquid crystal display element, 2 Transparent substrate, 3 Drive circuit board, 4 Light control layer, 4a Liquid crystal molecule, 4b Network transparent resin, 11 Thin film transistor, 12 Capacitor, 13 Switching drive circuit, 14 Substrate, 15 Signal line, 16 scanning lines, 17 display areas, 17a pixels, 18 signal drivers, 19 scanning drivers, 20a, 20b electrodes, 21 common electrodes, 22 interlayer insulating films, 23 recesses

Claims (14)

A first substrate;
A second substrate disposed opposite the first substrate and having optical transparency;
A light control layer provided between the first substrate and the second substrate and having a liquid crystal material and a transparent resin having a three-dimensional network structure;
The liquid crystal display element, wherein the first substrate is provided with a pair of electrodes for applying an electric field to the light control layer.   The liquid crystal display element according to claim 1, wherein the pair of electrodes applies an electric field substantially orthogonal to a thickness direction of the light control layer to the light control layer.   The liquid crystal display element according to claim 1, wherein a driving element for driving the pair of electrodes is provided on the first substrate.   The liquid crystal display element according to claim 1, wherein a plurality of the pair of electrodes are arranged in parallel in an in-plane direction of the first substrate.   The liquid crystal display element according to claim 1, wherein a recess is provided between the pair of electrodes on the first substrate side. A first substrate;
A second substrate disposed opposite the first substrate and having optical transparency;
A light control layer provided between the first substrate and the second substrate and having a liquid crystal material and a transparent resin having a three-dimensional network structure;
The first substrate and the second substrate are each provided with an electrode for applying an electric field to the light control layer,
The liquid crystal display element, wherein the light control layer has a region in contact with the second substrate.   The liquid crystal display element according to claim 6, wherein the electrode applies an electric field substantially orthogonal to the thickness direction of the light control layer to the light control layer.   The liquid crystal display element according to claim 6, wherein a driving element for driving the electrode is provided on the first substrate. A light control layer having a liquid crystal material and a transparent resin having a three-dimensional network structure is disposed between the first substrate and the second substrate that is disposed opposite to the first substrate and has light transmittance. A method of manufacturing a disposed liquid crystal display element,
A method of manufacturing a liquid crystal display element, wherein a pair of electrodes for applying an electric field to the light control layer is formed on the first substrate.   10. The method of manufacturing a liquid crystal display element according to claim 9, wherein a driving element for driving the pair of electrodes is formed on the first substrate.   The method for manufacturing a liquid crystal display element according to claim 9, wherein a plurality of the pair of electrodes are arranged on the first substrate in the in-plane direction of the first substrate.   The method for manufacturing a liquid crystal display element according to claim 9, wherein a recess that is recessed toward the first substrate is formed between the pair of electrodes. A light control layer having a liquid crystal material and a transparent resin having a three-dimensional network structure is disposed between the first substrate and the second substrate that is disposed opposite to the first substrate and has light transmittance. A method of manufacturing a disposed liquid crystal display element,
An electrode for applying an electric field to the light control layer is formed on each of the first substrate and the second substrate,
A method of manufacturing a liquid crystal display element, wherein the light control layer is provided with a region in contact with the second substrate. 14. The method for manufacturing a liquid crystal display element according to claim 13, wherein a driving element for driving the electrode is formed on the first substrate.

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