Display device and manufacturing method for display
Patent Information
- Application Number
- JP2023127742
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2023-08-04
- Publication Date
- 2025-02-17
Smart Images
Figure 2025023535000001_ABST
Abstract
Description
[Technical field]
[0001] FIELD An embodiment of the present invention relates to a display device and a method for manufacturing a display device. [Background technology]
[0002] 2. Description of the Related Art In recent years, display devices have been proposed that use polymer dispersed liquid crystal that is switchable between a scattering state in which incident light is scattered and a transmitting state in which incident light is transmitted. [Prior art documents] [Patent documents]
[0003] [Patent Document 1] JP 2019-219609 A Summary of the Invention [Problem to be solved by the invention]
[0004] An object of the present embodiment is to provide a display device that is free from display unevenness and has improved display quality. [Means for solving the problem]
[0005] A display device according to an embodiment includes: A first substrate having a plurality of switching elements; a second substrate disposed opposite the first substrate; A sealant disposed between the first substrate and the second substrate; a polymer dispersed liquid crystal layer having a polymer and liquid crystal molecules, the polymer dispersed liquid crystal layer being disposed between the first substrate and the second substrate and in an area surrounded by the sealant; Equipped with The nematic-isotropic transition temperature of the polymer dispersed liquid crystal layer is higher than the curing temperature of the sealant.
[0006] In addition, in a method for manufacturing a display device according to an embodiment, forming a first substrate by forming a plurality of switching elements on a first base material; forming a sealant surrounding a display region including the plurality of switching elements; A liquid crystal material including liquid crystal molecules and a polymer dispersed liquid crystal material including a liquid crystal monomer is dropped into the area surrounded by the sealant; A second substrate is disposed opposite the first substrate; The sealing material is cured by irradiating it with ultraviolet light; By irradiating ultraviolet light, the liquid crystal monomer is polymerized to form a polymer; The sealing material hardened by the irradiation of the ultraviolet light is heated to harden the sealing material; The nematic-isotropic transition temperature of the polymer dispersed liquid crystal material is higher than the heat curing temperature of the sealant.
[0007] In one embodiment of the method for manufacturing a display device, forming a first substrate by forming a plurality of switching elements on a first base material; forming a sealant surrounding a display region including the plurality of switching elements; A liquid crystal material including liquid crystal molecules and a polymer dispersed liquid crystal material including a liquid crystal monomer is dropped into the area surrounded by the sealant; A second substrate is disposed opposite the first substrate; The sealing material is hardened by heating the sealing material; By irradiating ultraviolet light, the liquid crystal monomer is polymerized to form a polymer; The sealing material that has been hardened by heating is hardened by irradiating ultraviolet light, The nematic-isotropic transition temperature of the polymer dispersed liquid crystal material is higher than the heat curing temperature of the sealant. [Brief description of the drawings]
[0008] [Figure 1] FIG. 1 is a plan view showing a schematic configuration of a display device according to the present embodiment. [Diagram 2]FIG. 2 is a plan view showing a schematic configuration of a display area of the display device of FIG. [Diagram 3] FIG. 3 is a cross-sectional view showing an example of a configuration that can be applied to the display panel shown in FIG. [Figure 4] FIG. 4 is a cross-sectional view showing an example of a schematic configuration of a display panel. [Diagram 5] FIG. 5 is a plan view of a display panel of the first comparative example. [Figure 6] FIG. 6 is a flowchart showing the manufacturing process of the display panel of Comparative Example 1. [Figure 7] FIG. 7 is a plan view of a display panel of the second comparative example. [Figure 8] FIG. 8 is a flowchart showing the manufacturing process of the display panel of Comparative Example 2. [Figure 9] FIG. 9 is a plan view of a display panel of Comparative Example 3. As shown in FIG. [Figure 10] FIG. 10 is a flowchart showing the manufacturing process of the display panel of Comparative Example 3. [Figure 11] FIG. 11 is a flowchart showing the manufacturing process of the display panel of the embodiment. [Figure 12] FIG. 12 is a flowchart of another configuration example of the display device in the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0009] Hereinafter, each embodiment of the present invention will be described with reference to the drawings. Note that the disclosure is merely an example, and those who are skilled in the art can easily come up with appropriate modifications while maintaining the gist of the invention, which are naturally included in the scope of the present invention. In addition, in order to make the explanation clearer, the drawings may show the width, thickness, shape, etc. of each part in a schematic manner compared to the actual embodiment, but these are merely examples and do not limit the interpretation of the present invention. In addition, in this specification and each figure, elements similar to those described above with respect to the previous figures may be given the same reference numerals, and detailed explanations may be omitted as appropriate.
[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments described in this specification are not general, but are embodiments describing the same or corresponding special technical features of the present invention.
[0011] In this embodiment, the first direction X, the second direction Y, and the third direction Z are perpendicular to each other, but may intersect at an angle other than 90 degrees. The direction toward the tip of the arrow of the third direction Z is defined as up or upward, and the direction opposite to the direction toward the tip of the arrow of the third direction Z is defined as down or downward. The first direction X, the second direction Y, and the third direction Z may also be called the X direction, the Y direction, and the Z direction, respectively.
[0012] Furthermore, in the case of "a second member above the first member" and "a second member below the first member," the second member may be in contact with the first member or may be located away from the first member. In the latter case, a third member may be interposed between the first and second members. On the other hand, in the case of "a second member above the first member" and "a second member below the first member," the second member is in contact with the first member.
[0013] Also, it is assumed that an observation position for observing the display device is located at the tip side of the arrow in the third direction Z, and a planar view refers to a view from this observation position toward the XY plane defined by the first direction X and the second direction Y. A cross-sectional view refers to a view of a cross section of the display device in the XZ plane defined by the first direction X and the third direction Z, or in the YZ plane defined by the second direction Y and the third direction Z.
[0014] [Embodiment] Fig. 1 is a plan view showing a schematic configuration of a display device in this embodiment. Fig. 2 is a plan view showing a schematic configuration of a display area of the display device in Fig. 1. In this embodiment, the first direction X and the second direction Y correspond to directions parallel to the main surface of a substrate constituting the display device DSP.
[0015] In this embodiment, a liquid crystal display device using a polymer dispersed liquid crystal (PDLC) is disclosed as the display device DSP. The display device DSP includes a display panel PNL, a wiring board FPC, an IC chip ICP (drive circuit), and a plurality of light sources LS.
[0016] The display panel PNL includes a substrate SUB1 (array substrate), a substrate SUB2 (counter substrate), a liquid crystal layer LC, and a sealant SAL. The substrates SUB1 and SUB2 are formed in flat plate shapes parallel to the XY plane and face each other in the third direction Z. The liquid crystal layer LC is disposed between the substrates SUB1 and SUB2.
[0017] The display panel PNL has a display area DA for displaying an image and a frame-shaped peripheral area PA surrounding the display area DA. The seal material SAL is disposed surrounding the display area DA. The display area DA has a plurality of pixels PX arranged in a matrix in the first direction X and the second direction Y.
[0018] As will be described in detail later, the seal material SAL is made by curing a mixture of photocurable resin and thermosetting resin. As the photocurable resin, for example, acrylic resin is used. As the thermosetting resin, for example, epoxy resin is used. Acrylic resin is cured by ultraviolet light (UV), and epoxy resin is cured by heat.
[0019] The display area DA is provided with a plurality of scanning lines GL that extend along a first direction X and are arranged side by side along a second direction Y. The display area DA is provided with a plurality of signal lines SL that are arranged side by side along the first direction X and extend along the second direction Y. Pixels PX are provided at each of the intersections of the plurality of scanning lines GL and the plurality of signal lines SL. One pixel PX is arranged in an area surrounded by two scanning lines GL and two signal lines SL.
[0020] Each of the pixels PX includes a switching element SW, a pixel electrode PE, and a common electrode CE. The switching element SW is formed of, for example, a thin film transistor (TFT) and is electrically connected to one scanning line GL and one signal line SL. The scanning line GL is electrically connected to the switching element SW in each of the pixels PX aligned in the first direction X. The signal line SL is electrically connected to the switching element SW in each of the pixels PX aligned in the second direction Y.
[0021] The pixel electrodes PE are electrically connected to the switching elements SW. The common electrode CE is provided in common to the plurality of pixel electrodes PE. The liquid crystal layer LC is driven by an electric field generated between the pixel electrodes PE and the common electrode CE. The capacitance CS is formed, for example, between an electrode having the same potential as the common electrode CE and an electrode having the same potential as the pixel electrodes PE.
[0022] The scanning lines GL, signal lines SL, switching elements SW, and pixel electrodes PE are provided on a substrate SUB1, and the common electrode CE is provided on a substrate SUB2. The scanning lines GL extend into the peripheral area PA and are electrically connected to the wiring substrate FPC or the IC chip ICP. The signal lines SL extend into the peripheral area PA and are electrically connected to the wiring substrate FPC or the IC chip ICP.
[0023] The wiring board FPC is electrically connected to a terminal arranged on the extension portion Ex of the board SUB1. The extension portion Ex corresponds to a portion of the board SUB1 that does not face the board SUB2. For example, the wiring board FPC is a flexible printed wiring board. The IC chip ICP is mounted on the wiring board FPC. The IC chip ICP has built-in, for example, a display driver that outputs signals necessary for image display. The IC chip ICP may be mounted on the extension portion Ex.
[0024] The light sources LS overlap the extension portion Ex. The light sources LS are arranged at intervals along the first direction X. Each of the light sources LS includes, for example, a light-emitting element that emits red (R) light, a light-emitting element that emits green (G) light, and a light-emitting element that emits blue (B) light. These light-emitting elements may be, for example, light-emitting diodes (LEDs), but are not limited to this example.
[0025] Fig. 3 is a cross-sectional view showing an example of a configuration applicable to the display panel shown in Fig. 1. The substrate SUB1 includes a base material BA1, an insulating layer INS1, an insulating layer INS2, a capacitive electrode YE, an alignment film AL1, a switching element SW, and a pixel electrode PE. The base material BA1 has a surface BA1a and a surface BA1b located on the opposite side of the surface BA1a along the third direction Z. The surfaces BA1a and BA1b are also referred to as the lower surface and the upper surface of the base material BA1, respectively.
[0026] The switching element SW is disposed on the surface BA1b side. The insulating layer INS1 covers the switching element SW. Although the switching element SW is simplified in FIG. 3, the switching element SW actually includes a semiconductor layer and various electrodes. In addition, the scanning line GL and the signal line SL shown in FIG. 1 are disposed between the base material BA1 and the insulating layer INS1, but are not shown in FIG. 3.
[0027] The capacitance electrode YE is disposed between the insulating layer INS1 and the insulating layer INS2. The pixel electrode PE is disposed for each pixel PX between the insulating layer INS2 and the alignment film AL1. The pixel electrode PE is electrically connected to the switching element SW through an opening OP of the capacitance electrode YE. The pixel electrode PE faces the capacitance electrode YE to form the above-mentioned capacitance CS. The alignment film AL1 covers the pixel electrode PE.
[0028] The substrate SUB2 includes a base material BA2, a light-shielding layer LB, an overcoat layer (insulating layer) OC, an alignment film AL2, and a common electrode CE. The substrate BA2 has a surface BA2a facing the substrate SUB1, and a surface BA2b located on the opposite side of the surface BA2a along the third direction Z. The surfaces BA2a and BA2b are also referred to as the lower surface and upper surface of the substrate BA2, respectively.
[0029] In the present disclosure, the substrates BA1 and BA2 are also referred to as a first substrate and a second substrate, respectively. The alignment films AL1 and AL2 are also referred to as a first alignment film and a second alignment film, respectively.
[0030] The light-shielding layer LB and the common electrode CE are disposed on the surface BA2a. For example, the light-shielding layer LB faces the switching element SW, the scanning line GL, and the signal line SL. The common electrode CE is disposed across the pixels PX and faces the pixel electrodes PE in the third direction Z. The common electrode CE covers the light-shielding layer LB. The common electrode CE has the same potential as the capacitive electrode YE. The overcoat layer OC covers the common electrode CE. The alignment film AL2 covers the overcoat layer OC. The liquid crystal layer LC is disposed between the alignment films AL1 and AL2 and is in contact with these alignment films AL1 and AL2. The overcoat layer OC may not be provided, and the alignment film AL2 may cover the common electrode CE.
[0031] As described above, the light source LS and the wiring board FPC are provided on the extension portion Ex on the substrate SUB1 (on the base material BA1). The light source LS does not have to be provided on the extension portion Ex. The light source LS may be disposed outside the display panel PNL, on the opposite side to the extension portion Ex along the direction opposite to the second direction Y.
[0032] The substrate BA1 and the substrate BA2 are transparent insulating substrates such as a glass substrate or a plastic substrate. The insulating layer INS1 is formed of a transparent insulating material such as silicon oxide, silicon nitride, silicon oxynitride, or acrylic resin. In one example, the insulating layer INS1 includes an inorganic insulating film and an organic insulating film. The insulating layer INS2 is an inorganic insulating film such as silicon nitride. The capacitance electrode YE, the pixel electrode PE, and the common electrode CE are transparent electrodes formed of a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO).
[0033] The configuration of the display panel PNL is not limited to the example in Figures 1 and 2. For example, the substrate SUB1 does not have to include the capacitive electrode YE. Also, the substrate SUB2 does not have to include the light-shielding layer LB.
[0034] Moreover, the display device DSP does not include a polarizing plate. That is, no polarizing plate is provided on the surface BA1a of the substrate SUB1 of the display panel PNL, and no polarizing plate is provided on the surface BA2b of the substrate SUB2.
[0035] 4 is a cross-sectional view showing an example of a schematic configuration of a display panel. The display panel PNL has a liquid crystal layer LC between a substrate SUB1 and a substrate SUB2. In this embodiment, the liquid crystal layer LC has a polymer PM including a polymer chain and liquid crystal molecules MC. The liquid crystal molecules MC are dispersed in the gaps of the polymer PM.
[0036] The substrate SUB1 includes a base material BA1, an insulating layer INS1, a signal line SL, an insulating layer INS2, a capacitive electrode YE, a pixel electrode PE, and an alignment film AL1.
[0037] The insulating layer INS1 is provided on the surface BA1b of the base material BA1. The signal line SL is provided on the insulating layer INS1 and covered by the insulating layer ILY. The capacitive electrode YE is provided on the insulating layer INS1 in the opening OP and covered by the insulating layer INS2. The capacitive electrode YE overlaps the insulating layer ILY and faces the signal line SL.
[0038] The pixel electrode PE is provided on the insulating layer INS2 in the opening OP and is covered with an alignment film AL1. That is, the capacitive electrode YE is provided between the base material BA1 and the pixel electrode PE. The pixel electrode PE faces the capacitive electrode YE with an insulating layer INS2 sandwiched therebetween, forming a capacitance CS of the pixel PX. The alignment film AL1 is in contact with the liquid crystal layer LC.
[0039] The substrate SUB2 includes a base material BA2, a common electrode CE, and an alignment film AL2. As in Fig. 3, an overcoat layer may be provided between the common electrode CE and the alignment film AL2. The common electrode CE is provided in contact with a surface BA2a of the base material BA2 and is covered with the alignment film AL2.
[0040] In addition, in the substrate SUB2, a light-shielding layer may be provided directly above each of the switching elements SW, the scanning lines GL, and the signal lines SL. In addition, a transparent insulating layer (overcoat layer) may be provided between the base material BA2 and the common electrode CE. The common electrode CE faces the multiple pixel electrodes PE. In addition, the common electrode CE is electrically connected to the capacitive electrode YE and has the same potential as the capacitive electrode YE. The alignment film AL2 is in contact with the liquid crystal layer LC.
[0041] The polymer PM and the liquid crystal molecules MC each have optical anisotropy or refractive index anisotropy. The responsiveness of the polymer PM to an electric field is lower than that of the liquid crystal molecules MC to an electric field. For example, the alignment direction of the polymer PM hardly changes regardless of the electric field between the pixel electrode PE and the common electrode CE. On the other hand, the alignment direction of the liquid crystal molecules MC changes in response to the electric field.
[0042] When no electric field is applied to the liquid crystal layer LC or when the electric field is extremely weak, the optical axes of the polymer PM and the liquid crystal molecules MC are approximately parallel to each other. The refractive indexes of the liquid crystal molecules MC and the polymer PM are substantially equal to each other. In other words, the difference in refractive index between the liquid crystal molecules MC and the polymer PM is substantially eliminated. Therefore, the light incident on the liquid crystal layer LC is transmitted through the liquid crystal layer LC without being scattered much within the liquid crystal layer LC. Hereinafter, this state is called a transparent state. The voltage of the pixel electrode PE for realizing the transparent state is called a transparent voltage. The transparent voltage may be the same as the common voltage applied to the common electrode CE, or may be a voltage slightly different from the common voltage.
[0043] On the other hand, when a sufficient electric field is applied to the liquid crystal layer LC, the optical axes of the polymer PM and the liquid crystal molecules MC cross each other. Therefore, the light incident on the liquid crystal layer LC is scattered within the liquid crystal layer LC. Hereinafter, this state will be called the scattering state. The voltage of the pixel electrode PE to realize the scattering state will be called the scattering voltage. The scattering voltage is a voltage that creates a larger potential difference with the common electrode CE than the transparent voltage.
[0044] Here, a comparative example will be described. Fig. 5 is a plan view of a display panel of Comparative Example 1. In the display panel PNLr1 (display device DSPr1) shown in Fig. 5, a nematic liquid crystal material, for example, is used as the liquid crystal layer, rather than a polymer dispersed liquid crystal material. In the display panel PNLr1 shown in Fig. 5, the same components as those of the display panel PNL shown in Fig. 1 are denoted by the same reference numerals.
[0045] The sealant SAL of the display panel PNLr1 has a notch, and an injection hole INH is formed in this portion. After the liquid crystal material is sucked into the inside of the display panel PNLr1 by vacuum suction, the injection hole INH is sealed with the sealing material HSZ.
[0046] Fig. 6 is a flowchart showing the manufacturing process of the display panel of Comparative Example 1. In Fig. 6, injection of liquid crystal material will be particularly described.
[0047] After forming the scanning lines GL, switching elements, signal lines SL, pixel electrodes, a planarizing insulating layer, etc. on the substrate SUB1 of the display panel PNLr1, an alignment film material is applied (Coating alignment film member) (Step SR101). For example, polyimide resin is used as the alignment film material.
[0048] The alignment film material is subjected to rubbing or light alignment treatment (Rubbing or processing light orientation) (Step SR102), thereby forming an alignment film.
[0049] The display area DA is surrounded by a sealing member SAL, which is applied onto the substrate SUB1 (step SR103). The sealing member SAL is made of a thermosetting resin, for example, an epoxy resin. As described above, a notch is provided in the sealing member SAL.
[0050] The substrate SUB2 is superposed on the substrate SUB1 (Superposing substrates) (step SR104). A space is generated between the substrates SUB1 and SUB2 in a region (display region DA) surrounded by the seal material SAL.
[0051] The sealing material SAL is cured by heating (step SR105). The above-mentioned notch becomes the injection hole INH.
[0052] The display panel PNLr1 is placed in a vacuum chamber, and a liquid crystal material is injected into the above-mentioned space (display area DA) through the injection hole INH by a vacuum injection method (step SR106).
[0053] After the liquid crystal material is injected, the injection hole INH is sealed with a sealing material HSZ (Sealing injection hole) (Step SR107). With the above steps, the display panel PNLr1 is completed (Completion) (Step SR108).
[0054] In the vacuum sealing method, the sealant SAL comes into contact with the liquid crystal material after the sealant SAL has completely hardened. This has the advantage of reducing the risk of contamination of the liquid crystal material. However, because the liquid crystal material is injected into the evacuated display panel PNLr1 by capillary action, as the sizes of the substrates SUB1 and SUB2 become larger, the time required to inject the liquid crystal material becomes longer, which may result in poor productivity.
[0055] Fig. 7 is a plan view of a display panel of Comparative Example 2. In the display panel PNLr2 (display device DSPr2) shown in Fig. 7, a nematic liquid crystal material, for example, is used as the liquid crystal layer, instead of a polymer dispersed liquid crystal material. In the display panel PNLr2 shown in Fig. 7, the same components as those of the display panel PNL shown in Fig. 1 are denoted by the same reference numerals.
[0056] In the display panel PNLr2, the sealant SAL is provided without any gaps, surrounding the display area DA. No notch is provided in the sealant SAL of the display panel PNLr2.
[0057] Fig. 8 is a flowchart showing the manufacturing process of the display panel of Comparative Example 2. In Fig. 8, dropping of the liquid crystal material will be particularly described.
[0058] Similar to step SR101, an alignment film material is applied (Coating alignment film member) (step SR201).
[0059] Similarly to step SR102, the alignment film material is subjected to rubbing or light alignment processing (rubbing or processing light orientation) (step SR202), thereby forming an alignment film.
[0060] A sealing material SAL is applied onto the substrate SUB1 so as to surround the display area DA without any gaps (Coating sealing member) (step SR203). A photocurable resin and a thermosetting resin are used for the sealing material SAL. For example, an acrylic resin may be used as the photocurable resin. For example, an epoxy resin may be used as the thermosetting resin. Unlike the display panel PNLr1, the sealing material SAL of the display panel PNLr2 does not have a notch.
[0061] A liquid crystal material is injected by dropping into an area (display area DA) surrounded by the seal material SAL of the substrate SUB1 (step SR204). That is, the liquid crystal material is filled by the ODF (One Drop Fill) method.
[0062] The substrate SUB2 is superposed on the substrate SUB1 (Superposing substrates) (step SR205). A liquid crystal material is filled in an area (display area DA) between the substrates SUB1 and SUB2 and surrounded by the sealant SAL.
[0063] The sealing material SAL is cured by UV irradiation (step SR206). This cures the photocurable resin contained in the sealing material SAL.
[0064] The sealing material SAL is cured by heating (step SR207), whereby the thermosetting resin contained in the sealing material SAL is cured.
[0065] Through the above, the display panel PNLr2 is completed (Completion) (step SR208).
[0066] The ODF method does not require the time required to inject the liquid crystal material, as does the vacuum injection method. Therefore, the ODF method is superior to the vacuum sealing method in terms of productivity. Also, the ODF method does not allow the liquid crystal material to get outside the seal material SAL.
[0067] However, since the seal material SAL comes into contact with the liquid crystal material in an uncured state, there is a risk of contaminating the liquid crystal material and the alignment film.
[0068] As mentioned above, the sealant SAL used in the ODF method is generally composed of a photocurable resin such as acrylic resin and a thermosetting resin such as epoxy resin. Even if the photocurable resin of the SAL sealant used in the ODF method is irradiated with UV light, the temperature is low and so there is little contamination of the liquid crystal material.
[0069] On the other hand, the heat curing temperature of the sealant SAL used in the liquid crystal drop (ODF) method is about 120°C. The heat curing temperature of the sealant SAL is higher than the nematic-isotropic (nematic-isotropic phase) transition temperature (referred to as transition temperature Tni) of the liquid crystal material. In the heat curing process (step SR207) of the sealant SAL, if the liquid crystal material is heated at a temperature higher than the transition temperature Tni, the liquid crystal material undergoes a phase transition from the nematic phase to a highly fluid isotropic liquid. This makes the liquid crystal material more susceptible to contamination.
[0070] Fig. 9 is a plan view of a display panel of Comparative Example 3. In the display panel PNLr3 (display device DSPr3) shown in Fig. 9, a polymer dispersed liquid crystal material is used for the liquid crystal layer. In the display panel PNLr3 shown in Fig. 9, the same components as those of the display panel PNL shown in Fig. 1 are denoted by the same reference numerals.
[0071] A plurality of injection holes INH are formed in the sealant SAL of the display panel PNLr3. After the liquid crystal material is sucked into the interior of the display panel PNLr3 by vacuum suction, each of the injection holes INH is sealed with the sealing material HSZ.
[0072] Fig. 10 is a flowchart showing the manufacturing process of the display panel of Comparative Example 3. In Fig. 10, injection of liquid crystal material will be particularly described.
[0073] Similar to step SR101, an alignment film material is applied (Coating alignment film member) (step SR301).
[0074] Similarly to step SR102, the alignment film material is subjected to rubbing or light alignment processing (step SR302), thereby forming an alignment film.
[0075] The display area DA is surrounded by a sealing member SAL applied onto the substrate SUB1 (step SR303). A thermosetting resin is used for the sealing member SAL. For example, an epoxy resin is used for the thermosetting resin. As described above, a plurality of notches are provided in the sealing member SAL.
[0076] The substrate SUB2 is superposed on the substrate SUB1 (Superposing substrates) (step SR304). A space is generated between the substrates SUB1 and SUB2 in a region (display region DA) surrounded by the seal material SAL.
[0077] The thermosetting resin of the sealing material SAL is cured by heating (step SR305). The above-mentioned multiple cutouts become multiple injection holes INH.
[0078] The display panel PNLr3 is placed in a vacuum chamber, and a polymer dispersed liquid crystal (PDLC) material is injected into the above-mentioned space (inside the display area DA) through the multiple injection holes INH by a vacuum injection method (Injecting PDLC member) (Step SR306).
[0079] Polymer-dispersed liquid crystal (PDLC) materials include liquid crystal materials containing liquid crystal molecules MC, liquid crystal monomers, photo-radical polymerization initiators, and the like.
[0080] After injecting the liquid crystal material, the injection hole INH is sealed with a sealing material HSZ (Sealing injection hole) (Step SR307).
[0081] The PDLC material is then cured by UV irradiation (step SR308).
[0082] When ultraviolet light (UV) is irradiated, polymerization is initiated by the photoradical polymerization initiator, and the liquid crystal monomer is polymerized. This results in the formation of a polymer PM containing polymer chains. The liquid crystal molecules MC of the liquid crystal material contained in the polymer dispersed liquid crystal (PDLC) material are dispersed in the gaps between the polymer PM, as explained in Figure 4.
[0083] Through the above, the display panel PNLr3 is completed (Completion) (step SR309).
[0084] As described above, in the vacuum injection method, as the size of the substrate SUB1 and the substrate SUB2 increases, the time required to inject the liquid crystal material becomes longer, which may result in poor productivity. Therefore, in this embodiment, a liquid crystal drop (ODF) method is used in the manufacture of a display panel that includes a polymer dispersed liquid crystal material as the liquid crystal layer LC. This makes it possible to improve the productivity of the display device.
[0085] Fig. 11 is a flowchart showing the manufacturing process of the display panel of the embodiment. In particular, the liquid crystal drop (ODF) method is described in Fig. 11. The display panel manufactured according to the flowchart shown in Fig. 11 is the display panel PNL (display device DSP) shown in Fig. 1.
[0086] As in step SR101, an alignment film material is applied (Coating alignment film member) (step ST101).
[0087] As in step SR102, the alignment film material is subjected to rubbing or light alignment processing (rubbing or processing light orientation) (step ST102), thereby forming an alignment film.
[0088] A sealing material SAL is applied onto the substrate SUB1 so as to surround the display area DA without any gaps (Coating sealing member) (step ST103). A photocurable resin and a thermosetting resin are used for the sealing material SAL. For example, an acrylic resin may be used as the photocurable resin. For example, an epoxy resin may be used as the thermosetting resin. As described above, the display area DA is surrounded by the sealing material SAL without any gaps, and no notches exist.
[0089] A polymer dispersed liquid crystal (PDLC) material is injected by dropping into an area (display area DA) surrounded by the seal material SAL of the substrate SUB1 (step ST104). That is, the polymer dispersed liquid crystal (PDLC) material is filled by the ODF method.
[0090] Polymer-dispersed liquid crystal (PDLC) materials include liquid crystal materials containing liquid crystal molecules MC, liquid crystal monomers, photo-radical polymerization initiators, and the like.
[0091] The substrate SUB2 is superposed on the substrate SUB1 (Superposing substrates) (step ST105). A polymer dispersed liquid crystal (PDLC) is filled in an area (display area DA) between the substrates SUB1 and SUB2 and surrounded by a seal material SAL.
[0092] The photocurable resin in the sealing material SAL is cured by UV irradiation (step ST106). This causes the photocurable resin in the sealing material SAL to be cured.
[0093] Then, the polymer dispersed liquid crystal (PDLC) material is cured by UV irradiation (step ST107).
[0094] When ultraviolet light (UV) is irradiated, polymerization is initiated by the photoradical polymerization initiator, and the liquid crystal monomer is polymerized. This results in the formation of a polymer PM containing polymer chains. The liquid crystal molecules MC of the liquid crystal material contained in the polymer dispersed liquid crystal (PDLC) material are dispersed in the gaps between the polymer PM, as explained in Figure 4.
[0095] Next, the thermosetting resin of the sealing material SAL is cured by heat (Curing sealing member by heating) (step ST108). This cures the thermosetting resin contained in the sealing material SAL. The heating temperature in step ST108 is temperature Tc. By heating the sealing material SAL at temperature Tc, the sealing material SAL is cured. Therefore, temperature Tc is also called the curing temperature of the sealing material SAL. Temperature Tc is lower than the transition temperature Tni.
[0096] Through the above steps, the display panel PNL (display device DSP) is completed (Completion) (step ST109).
[0097] As shown in Fig. 11, after the polymer dispersed liquid crystal (PDLC) material is injected (step ST107), the sealant SAL is UV cured (step ST108). At this time, the polymer dispersed liquid crystal (PDLC) material near the sealant SAL is also exposed to ultraviolet light (UV). The liquid crystalline monomer contained in the polymer dispersed liquid crystal (PDLC) material is polymerized, and there is a risk that the part exposed to the ultraviolet light will cause display abnormalities. Therefore, after the polymer dispersed liquid crystal (PDLC) material is injected, the sealant SAL is thermally cured (step ST108).
[0098] The polymer dispersed liquid crystal (PDLC) material of this embodiment is a polymer dispersed liquid crystal (PDLC) material including a liquid crystal material having a transition temperature Tni equal to or higher than the temperature Tc at which the seal material SAL is heated in step ST108. More specifically, in this embodiment, a polymer dispersed liquid crystal (PDLC) material including a liquid crystal material having a transition temperature Tni of 120° C. or higher and 150° C. or lower is used. If the transition temperature Tni is higher than the temperature Tc, which is the heating temperature of the seal material SAL, the liquid crystal material including the liquid crystal molecules MC does not become an isotropic liquid and remains in the nematic phase even in the heating process of step ST108. This prevents display unevenness from occurring on the display panel PNL (display device DSP).
[0099] If the heating temperature for thermally curing the sealant SAL (step ST108) is higher than the transition temperature Tni of the liquid crystal material, the liquid crystal material undergoes a phase transition from a nematic phase to an isotropic liquid with high fluidity, which makes the liquid crystal material more susceptible to contamination and more likely to cause display unevenness.
[0100] A liquid crystal material having a transition temperature Tni of 120° C. or more and 150° C. or less is, for example, a liquid crystal material with a large molecular weight. More specifically, it may be a liquid crystal material having a high proportion of tricyclic compounds containing three six-membered rings such as cyclohexane or benzene rings, or tetracyclic compounds containing four six-membered rings. Furthermore, the proportion of the liquid crystal material having tricyclic compounds or tetracyclic compounds may be higher than the proportion of the liquid crystal material having bicyclic compounds containing two six-membered rings.
[0101] A liquid crystal material with a large molecular weight has a high viscosity. Therefore, the response speed of a liquid crystal layer using such a liquid crystal material is slow. However, the liquid crystal layer LC of this embodiment is a liquid crystal layer of a polymer-dispersed liquid crystal material. In the liquid crystal layer LC of a polymer-dispersed liquid crystal material, the liquid crystal molecules MC are dispersed in the gaps (microdomains, also called droplets) of the polymer PM. Therefore, the response speed of the liquid crystal molecules MC is fast. Therefore, even if the liquid crystal molecules MC of a liquid crystal material with a large molecular weight are used, the response speed of the liquid crystal layer LC of the display panel PNL of this embodiment is sufficiently fast. In this embodiment, even if a liquid crystal material with a large molecular weight, that is, a liquid crystal material with a transition temperature Tni of 120° C. or more and 150° C. or less is used, it is possible to obtain a display panel PNL (display device DSP) with a sufficiently fast response speed.
[0102] However, when the transition temperature Tni rises, the smectic-nematic transition temperature (referred to as transition temperature Tsn) also rises. When the liquid crystal material is below the transition temperature Tsn, the liquid crystal material goes into the smectic phase. In the display panel PNL of this embodiment, if the liquid crystal molecules MC in the liquid crystal layer LC go into the smectic phase, there is a risk that the display panel will not operate.
[0103] If the transition temperature Tni of the liquid crystal material of the liquid crystal layer LC of this embodiment is 120° C. or more and 150° C. or less, the transition temperature Tsn of the liquid crystal material will not become too high.
[0104] As described above, according to the present embodiment, it is possible to obtain a display device that does not cause display unevenness and a manufacturing method thereof. Since the display device DSP (display panel PNL) of the present embodiment does not cause display unevenness, it is possible to improve the display quality.
[0105] <Configuration example 1> Fig. 12 is a flowchart of another configuration example of the display device in the embodiment. The configuration example shown in Fig. 12 is different from the configuration example shown in Fig. 11 in that the curing process by heating the sealant SAL and the curing process by UV irradiation are reversed.
[0106] In this configuration example, steps ST101 to ST105 are the same as those in the embodiment (see FIG. 11). In this configuration example, steps ST201 to ST205 are the same as those in the embodiment (steps ST101 to ST105).
[0107] After the substrate SUB2 is superimposed on the substrate SUB1 (step ST205), the thermosetting resin of the sealing material SAL is cured by heat (curing sealing member by heating) (step ST206). This cures the thermosetting resin contained in the sealing material SAL. The temperature Tc, which is the heating temperature in step ST206, is lower than the transition temperature Tni, as in the embodiment.
[0108] In step ST206, the photocurable resin may also be cured by heating. If a thermal radical agent is added to the photocurable resin, the photocurable resin may also be cured by heat. The curing of the photocurable resin by heat may be performed on the entirety or only on a part of the photocurable resin.
[0109] Next, the polymer dispersed liquid crystal (PDLC) material is cured by UV irradiation (Step ST207), whereby the liquid crystal monomer is polymerized, as in the embodiment.
[0110] The photocurable resin of the sealing material SAL is cured by UV irradiation (step ST208). This cures the photocurable resin contained in the sealing material SAL. If the photocurable resin is partially cured by heat, the entire photocurable resin is cured by step ST208.
[0111] Through the above steps, the display panel PNL (display device DSP) is completed (Completion) (step ST209). This configuration also provides the same effects as the embodiment.
[0112] In the present disclosure, the substrate SUB1 and the substrate SUB2 are referred to as a first substrate and a second substrate, respectively.The liquid crystal layer LC having a polymer dispersed liquid crystal material is referred to as a polymer dispersed liquid crystal layer.
[0113] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]
[0114] DA...display area, DSP...display device, HSZ...sealing material, INH...injection hole, LC...liquid crystal layer, MC...liquid crystal molecule, PM...polymer, PNL...display panel, SAL...sealing material, ST101...step, ST102...step, ST103...step, ST104...step, ST105...step, ST106...step, ST107...step, ST108...step, ST109...step.
Claims
1. A first substrate having a plurality of switching elements; a second substrate disposed opposite the first substrate; A sealant disposed between the first substrate and the second substrate; and a polymer dispersed liquid crystal layer having a polymer and liquid crystal molecules, the polymer dispersed liquid crystal layer being disposed between the first substrate and the second substrate and in an area surrounded by the sealant; Equipped with The display device, wherein the nematic-isotropic transition temperature of the polymer dispersed liquid crystal layer is higher than the curing temperature of the sealant.
2. 2. The display device according to claim 1, wherein the nematic-isotropic transition temperature of the polymer dispersed liquid crystal layer is 120° C. or higher and 150° C. or lower.
3. A plurality of pixels including the plurality of switching elements; a display area including the plurality of pixels; Further equipped with The display device according to claim 1 , wherein the sealing material is disposed so as to surround the display area.
4. 2. The display device according to claim 1, wherein the liquid crystal molecules of the polymer dispersed liquid crystal layer include a tricyclic compound having three six-membered rings or a tetracyclic compound having four six-membered rings.
5. forming a first substrate by forming a plurality of switching elements on a first base material; forming a sealant surrounding a display region including the plurality of switching elements; A liquid crystal material including liquid crystal molecules and a polymer dispersed liquid crystal material including a liquid crystal monomer is dropped into the area surrounded by the sealant; A second substrate is disposed opposite the first substrate; The sealing material is cured by irradiating it with ultraviolet light; By irradiating ultraviolet light, the liquid crystal monomer is polymerized to form a polymer; The sealing material hardened by the irradiation of the ultraviolet light is heated to harden the sealing material; A nematic-isotropic transition temperature of the polymer dispersed liquid crystal material is higher than a curing temperature by heating of the sealant.
6. 6. The method for manufacturing a display device according to claim 5, wherein the nematic-isotropic transition temperature of the polymer dispersed liquid crystal material is 120° C. or higher and 150° C. or lower.
7. The display device includes: A plurality of pixels including the plurality of switching elements; a display area including the plurality of pixels; Further equipped with The method for manufacturing a display device according to claim 5 , wherein the sealing material is disposed so as to surround the display region.
8. The method for manufacturing a display device according to claim 5 , wherein the liquid crystal molecules of the polymer dispersed liquid crystal material contain a tricyclic compound having three six-membered rings or a tetracyclic compound having four six-membered rings.
9. forming a first substrate by forming a plurality of switching elements on a first base material; forming a sealant surrounding a display region including the plurality of switching elements; A liquid crystal material including liquid crystal molecules and a polymer dispersed liquid crystal material including a liquid crystal monomer is dropped into the area surrounded by the sealant; A second substrate is disposed opposite the first substrate; The sealing material is hardened by heating the sealing material; By irradiating ultraviolet light, the liquid crystal monomer is polymerized to form a polymer; The sealing material that has been hardened by heating is hardened by irradiating ultraviolet light, A nematic-isotropic transition temperature of the polymer dispersed liquid crystal material is higher than a curing temperature by heating of the sealant.
10. 10. The method for manufacturing a display device according to claim 9, wherein the nematic-isotropic transition temperature of the polymer dispersed liquid crystal material is 120° C. or higher and 150° C. or lower.
11. The display device includes: A plurality of pixels including the plurality of switching elements; a display area including the plurality of pixels; Further equipped with The method for manufacturing a display device according to claim 9 , wherein the sealing material is disposed so as to surround the display region.
12. The method for manufacturing a display device according to claim 9 , wherein the liquid crystal molecules of the polymer dispersed liquid crystal material contain a tricyclic compound having three six-membered rings or a tetracyclic compound having four six-membered rings.
Citation Information
Patent Citations
Liquid crystal panel and electro-optical device
JP2019219609A