JP2005284139A - Display device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve light resistance of a light shielding member of a liquid crystal display device. <P>SOLUTION: A liquid crystal display panel 102 is equipped with the light shielding member 203. THe seal member 203 contains mixed insulating carbon black. The light shielding rate (100%-transmissivity) of the seal member 203 is preferably ≥80% when a film thickness is 6 μm and a wavelength is 550 nm so that a light leak is effectively prevented. Further, the volume resistance of the seal material 203 is preferably ≥10E12 Ωcm under measurement conditions of a 6 μm film thickness and a ≤30 V voltage so as to securely prevent a short circuit between wires of the seal member 203. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a display device and a manufacturing method thereof, and more particularly to a display device including a light-shielding sealing member and a manufacturing method thereof.

  As an image display device for personal computers and other various monitors, or as a display screen of a mobile phone or a television receiver, there has been a remarkable spread of liquid crystal display devices. The liquid crystal display device typically includes a liquid crystal display panel and a backlight unit disposed on the back surface thereof. The liquid crystal display panel displays an image by controlling the transmitted light. The backlight unit typically includes a light source and a plurality of optical members for effectively emitting light from the light source to the liquid crystal display panel. As a light source of the backlight unit, a cold cathode tube and a light emitting diode are known.

  The liquid crystal display panel can control the amount of transmitted light by enclosing a liquid crystal between two glass substrates and controlling an electric field applied to the liquid crystal. FIG. 3 is a schematic diagram showing a schematic configuration of a conventional liquid crystal display panel 300. 3A is a plan view of the liquid crystal display panel 300, and FIG. 3B shows a cross-sectional structure of a portion indicated by YY ′. The liquid crystal display panel 300 includes two transparent substrates 301 and 302 and a liquid crystal material sealed between the two transparent substrates 301 and 302.

  The liquid crystal display panel 300 includes a display area 303 composed of a plurality of pixels. An image is displayed in the display area 303. The two transparent substrates 301 and 302 are fixed by a seal member 304 formed in the outer peripheral area outside the display area 303. In addition, a large number of spacers 305 are dispersed between the transparent substrates 301 and 302 in order to keep the gap between the two transparent substrates 301 and 302 constant.

  For example, in a passive type liquid crystal display panel, electrodes are formed on both transparent substrates 301 and 302, and the electrodes on the transparent substrate 301 and the electrodes on the transparent substrate 302 are arranged to intersect each other. A portion where the electrodes intersect corresponds to a pixel. By applying an electric field to the liquid crystal material between the intersecting electrodes, light transmission by the liquid crystal material can be controlled.

  In an active matrix type liquid crystal display panel, pixel electrodes arranged in a matrix on one substrate, for example, a transparent substrate 301, and switch elements corresponding to the pixel electrodes are formed. By controlling the switch element, a signal can be supplied to the selected pixel electrode, and light transmission of the liquid crystal material in each pixel can be controlled. The counter electrode that forms an electric field with the pixel electrode can be formed on the other transparent substrate 302 or the same transparent substrate 301 as the pixel electrode, depending on the mode of the liquid crystal display panel.

  In the liquid crystal display device, it is one of important points to prevent light leakage from the outside or from the backlight unit into the display area. For this reason, in a conventional liquid crystal display device, a black dye is mixed into the seal member to form a light-shielding seal member. For example, Patent Document 1 discloses that a rectangular frame pattern made of a black colored layer is formed around a display area.

JP 2001-142088 A

  However, when the sealing member is colored with a dye, there is a problem that the dye in the sealing member is decomposed by ultraviolet rays contained in external light and fades with time. On the other hand, pigments are known as colorants in addition to dyes. Carbon black is widely known as a black pigment, but general carbon black has a problem of short-circuiting between wirings due to high conductivity. That is, there is a problem that a short circuit occurs between the lead wires formed on the upper and lower substrates or between the lead wires formed adjacent to each other in the portion where the seal member is formed.

  The present invention has been made against the background of the above circumstances, and an object of the present invention is to prevent a short circuit between wires in a light-shielding seal member of a display device and to improve light resistance in the light-shielding seal member. The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

  A display device according to a first aspect of the present invention is formed between a first substrate, a second substrate disposed opposite to the first substrate, and the first substrate and the second substrate. A plurality of pixels, and a light-shielding sealing member formed in an outer peripheral region of the plurality of pixels, fixing the first substrate and the second substrate, and mixed with insulating carbon black. . By having this structure, the short circuit between wiring in the light-shielding sealing member of a display apparatus can be prevented, and the light resistance in a light-shielding sealing member can be improved.

  The light shielding seal member preferably has a volume resistance of 10E12 Ω · cm or more. Thereby, the short circuit between wiring can be prevented more reliably. Alternatively, from the viewpoint of light shielding properties, the light shielding rate of the light shielding sealing member is preferably 80% or more.

  The method for manufacturing a display device according to the second aspect of the present invention includes a step of applying an uncured sealing material mixed with insulating carbon black on the first substrate, and applying the uncured sealing material. And laminating the second substrate on the first substrate, and curing the uncured sealing material to fix the first substrate to the second substrate. By having this structure, the short circuit between wiring in the light-shielding sealing member of a display apparatus can be prevented, and the light resistance in a light-shielding sealing member can be improved.

  The uncured sealing material applied to the first substrate is preferably mixed with 1 to 15 parts by weight of insulating carbon black with respect to 100 parts by weight of the sealing base material. More preferably, 2 to 8 parts by weight of insulating carbon black is mixed with 100 parts by weight of the sealing substrate. As a result, a short circuit between the wirings can be prevented more reliably, and the necessary light shielding and light resistance of the sealing member can be ensured.

  ADVANTAGE OF THE INVENTION According to this invention, the light resistance in the light-shielding sealing member of a display apparatus can be improved, and the short circuit between wiring in a light-shielding sealing member can be prevented.

  Hereinafter, embodiments to which the present invention can be applied will be described. The following description is to describe the embodiment of the present invention, and the present invention is not limited to the following embodiment. For clarity of explanation, the following description and drawings are omitted and simplified as appropriate. Moreover, those skilled in the art can easily change, add, and convert each element of the following embodiments within the scope of the present invention.

  FIG. 1 is an exploded perspective view for explaining the entire configuration of a liquid crystal display module according to the present embodiment, which is an example of the liquid crystal display device of the present invention. FIG. 1 shows an outline of a liquid crystal display module 100 having a sidelight type backlight unit. In FIG. 1, 101 is a backlight unit, and 102 is a liquid crystal display panel to which drive circuits 110 and 111 are attached. The liquid crystal display panel 102 is driven by drive circuits 110 and 111, and can display an image by controlling transmission of light from the backlight unit 101. The configuration of the liquid crystal display panel 102 will be described in detail later.

  The backlight unit 101 includes a prism sheet 103, a light guide plate 104, a reflection sheet 105, a frame 106, a cold cathode tube 107, and a lamp reflector 108. As shown in FIG. 1, the prism sheet 103, the light guide plate 104, and the reflection sheet 105 are laminated in this order from the viewing side. The prism sheet 103 improves the luminance of the display front by condensing light. The prism sheet 103 can be typically configured by forming an uneven structure with an organic resin on a base film such as polyethylene terephthalate.

  In this embodiment, a downward prism sheet is illustrated as the prism sheet 103. The prism sheet 103 has a plurality of prism structures having a light condensing function on one surface. In general, the prism structure portion that is disposed facing the light guide plate 104 is referred to as a downward prism sheet. The cross-sections of the plurality of prism structures are serrated, and the ridge lines extend along the longitudinal direction of the cold cathode tube 107 from one side of the prism sheet toward the opposite side.

  Typically, a plurality of prism structures having a triangular cross section extending from the cold cathode tube 107 side to the opposite side are formed on the surface of the light guide plate on the viewing side. The prism sheet 103 may be an upward prism sheet that is arranged so that the prism structure portion faces upward. Typically, the upward prism sheets are used as a set of two sheets, and are arranged so that the ridge lines of each prism sheet are orthogonal to each other.

  The light guide plate 104 guides and diffuses light from the cold cathode tube 107 which is a linear light source, and emits planar light. The light guide plate 104 can be formed of an acrylic resin. The reflection sheet 105 reflects the light incident from the light guide plate 104 to the viewing side. The components of the backlight unit 101 such as the prism sheet 103, the light guide plate 104, and the reflection sheet 105 are accommodated in the frame 106. The frame 106 can typically be formed of an organic resin such as polycarbonate.

  A cold cathode tube 107 serving as a linear light source is disposed inside a cylindrical lamp reflector 108. As a light source, in addition to the cold cathode tube 107 which is a linear light source, an LED (Light Emitting Diodes) which is a point light source can be used. The lamp reflector 108 can be formed of brass having a white reflective layer or an Ag reflective layer on the inner surface, or white resin. Reference numeral 109 denotes a bezel that holds and protects the liquid crystal display panel 102 and the backlight unit 101 from the outside. The bezel 109 is formed of resin or metal.

  The liquid crystal display panel 102 in this embodiment will be described. The liquid crystal display panel 102 has a display area composed of a plurality of pixels and a peripheral area formed around the display area. As shown in FIG. 1, driver ICs 110 and 111 are connected to the peripheral region. Each pixel in the display area of the liquid crystal display panel 102 performs RGB color display. In a monochrome display, a monotone display changing between white and black is performed. An active matrix type liquid crystal display panel has an array substrate in which TFT (Thin Film Transistor) switch elements are formed on an array, and a counter substrate disposed to face the array substrate.

  In a color liquid crystal display panel, a color filter layer is formed on a counter substrate. In the display area on the array substrate, a plurality of signal lines and gate lines are arranged in a matrix. The signal line and the gate line are arranged so as to overlap each other at a substantially right angle. Each pixel applies an electric field to the liquid crystal based on a signal voltage input from the driver IC. This driver IC is typically connected to the array substrate by TAB (Tape Automated Bonding) as shown in FIG. 1, but may be provided directly on the glass substrate of the array substrate.

  Typically, a plurality of source driver ICs 110 for signal lines are provided on the X axis side of the TFT array substrate, and a plurality of gate driver ICs 111 for gate lines for controlling the gate voltage are provided on the Y axis side. A voltage input from the source driver IC 110 is sent to the pixel electrode through the source and drain of the TFT, and the pixel electrode on the array substrate and the common electrode on the counter substrate apply an electric field to the liquid crystal. By changing this voltage, the voltage applied to the liquid crystal can be changed, and the light transmittance of the liquid crystal is controlled. A circuit for applying a common potential to the common electrode is configured on a control circuit board (not shown).

  As the liquid crystal display panel 102, a simple matrix type switch having no switching element is known in addition to the above active matrix type. Other types of liquid crystal display panels include TN (Twisted Nematic) type liquid crystal display panels, STN (Super Twisted Nematic) type liquid crystal display panels, and IPS (In Plane) in which pixel electrodes and common electrodes are formed on the same substrate. Switching) type liquid crystal display panel is known. The present invention is applicable to various types of liquid crystal display panels as described above. Further, the present invention is not limited to the liquid crystal display device, but can be applied to other display devices such as an organic EL (Electro Luminescence) display device.

  FIG. 2 is a cross-sectional view showing a schematic configuration of a liquid crystal display panel 102 as an example of the present invention. FIG. 2 illustrates a partial configuration of the TFT color liquid crystal display panel. In the liquid crystal display module 100, a backlight unit 101 is disposed below the liquid crystal display panel 102 shown in FIG. As shown in FIG. 2, the liquid crystal display panel 102 includes an array substrate 201 on which a TFT array circuit is formed, and a counter substrate 202 that is disposed facing the array substrate 201 and on which a color filter is formed. .

  The array substrate 201 and the counter substrate 202 are bonded and fixed by a seal member 203 formed in an outer peripheral region that is outside a display region formed of a plurality of pixels. The seal member 203 is formed by applying an uncured seal material in a frame shape with a dispenser, for example, on the outer peripheral region of the color filter substrate 202, and superimposing the array substrate 201 and the color filter substrate 202 and curing them by light or heat. It is formed. The seal member of this embodiment is a light-shielding seal member that blocks light. Details of the seal member 203 will be described later.

  The array substrate 201 and the counter substrate 202 are maintained at a predetermined interval by bead spacers or columnar spacers. When using bead spacers, the bead spacers are spread on one substrate before the two substrates 201 and 202 are fixed by the seal member 203. A liquid crystal material is sealed between the two substrates 201 and 202. After the substrates 201 and 202 are fixed by the seal member 203, the liquid crystal material is injected between the substrates 201 and 202 by vacuum injection from an opening formed in the seal member. The opening of the sealing member is sealed with a sealing material after the liquid crystal is injected.

  The counter substrate 202 has a back side transparent substrate 204 formed of glass or resin on the back side (anti-view side) on the viewing side, that is, on the backlight unit 101 side. A polarizing plate 205 is fixed to the outer surface of the back side transparent substrate 204. The polarizing plate 205 allows only linearly polarized light having a vibration direction parallel to a specific transmission axis to pass.

  A color filter layer 206 is formed on the inner surface of the back side transparent substrate 204. Typically, the color filter layer 206 of any color of red, green, and blue is formed in each pixel according to a predetermined color arrangement. Around the color filter layer 206, a black matrix layer 207 made of a resin or a chromium metal is formed. The black matrix layer 207 blocks light from the backlight unit 101 in order to improve contrast and prevent light irradiation to the amorphous silicon of the TFT.

  A protective layer 208 is formed on the color filter layer 206 and the black matrix layer 207. Further, on the protective layer 208, an ITO (Indium Tin Oxide) electrode layer 209, which is a transparent electrode layer that functions as a common electrode for applying an electric field to the liquid crystal, is formed. The ITO electrode layer 209 is formed as a single layer that is continuous inside the substrate. On the ITO electrode layer 209, an alignment film 210 for controlling the alignment and inclination of the liquid crystal is formed. The alignment film 210 is typically formed by rubbing a polyimide layer.

  The array substrate 201 has a front side (viewing side) transparent substrate 211 formed of glass or a resin material. A polarizing plate 212 is fixed on the outer surface of the front transparent substrate 211. The polarizing plate 212 can regulate the amount of light transmitted through the liquid crystal layer by transmitting only linearly polarized light that vibrates in a predetermined direction. The transmission axis of the polarizing plate 212 is arranged perpendicularly or parallel to the transmission axis of the polarizing plate 205 depending on the mode of the liquid crystal display panel.

  An array circuit is formed on the inner surface of the front transparent substrate 211. The array circuit includes a TFT 213 as a switch element and a pixel electrode 214 that applies an electric field to the liquid crystal. The TFT 213 can be formed using amorphous silicon or polysilicon. Similar to the common electrode, the pixel electrode 214 is formed of ITO. The TFT 213 and the pixel electrode 214 are formed for each pixel, and the selected pixel electrode 214 applies a display electric field to the liquid crystal with the ITO electrode layer 209 in accordance with the control signal and the display signal from the driver ICs 110 and 111. On the array circuit, an alignment film 215 for controlling the alignment and inclination of the liquid crystal is formed. The alignment direction of the alignment film 215 is formed so as to be twisted by 90 ° with respect to the alignment film 210.

  An optical operation of the liquid crystal display panel 102 will be described. Light from the backlight unit 101 enters a polarizing plate 205 formed on the outer surface of the back side transparent substrate 204 through an air layer. Of the incident light, only linearly polarized light that vibrates in a direction parallel to the transmission axis of the polarizing plate 205 is transmitted through the polarizing plate 205. Part of the incident light is blocked by the black matrix layer 207, and part of the light passes through the color filter layer 206. Further, a part of unnecessary light from the outside or from the backlight unit is blocked by the light-shielding seal member 203. In accordance with the liquid crystal state controlled by the applied electric field, the incident light passes through the liquid crystal layer without rotating or rotating the polarization axis of the linearly polarized light incident on the liquid crystal layer.

  The light that has passed through the liquid crystal layer passes through the front transparent substrate 211 and enters the polarizing plate 212 attached to the outer surface of the front transparent substrate 211. Of the incident light, only linearly polarized light having a vibration component parallel to the transmission axis of the polarizing plate 212 is transmitted. Thus, the amount of light irradiated on the display surface side is controlled by the electric field applied to the liquid crystal.

  As described above, the seal member 203 of this embodiment is a light-shielding seal member. The seal member 203 is mixed with a black pigment. Insulating carbon black is used as the pigment to be mixed. Unlike ordinary conductive carbon black, which is a condensed aromatic compound with π-electron conductivity, insulating carbon black has a molecular structure that modifies the particle surface to prevent π-electron conjugation and has extremely low conductivity. Indicates. As the insulating carbon black, for example, MA100R manufactured by Mitsubishi Chemical Corporation can be used. Since carbon black exhibits high light resistance, discoloration of the seal member 203 can be effectively suppressed.

  As a sealing material that is a base material of the sealing member 203, an ultraviolet curable resin or a thermosetting resin can be used. For example, an ultraviolet curable or thermosetting epoxy resin is used. As the sealing substrate, for example, an LCD sealing material XN-21S manufactured by Mitsui Chemicals, Inc. can be used. The light shielding rate (100% -transmittance) of the seal member 203 is preferably 80% or more at a film thickness of 6 μm and a wavelength of 550 nm in order to effectively prevent light leakage. Further, in order to surely prevent a short circuit between wirings by the seal member 203, the volume resistance of the seal member 203 is 10E12 Ω · cm or more in accordance with JIS-K6911 under measurement conditions of a film thickness of 6 μm and a voltage of 30 V or less. Is preferred.

  The sealing member 203 of this embodiment is formed by mixing insulating carbon black into an uncured sealing material and curing the sealing material applied on the substrate. In the formation of the sealing material, the amount of insulating carbon black mixed in the uncured sealing material is preferably 1 to 15 parts by weight with respect to 100 parts by weight of the sealing material. More preferably, 2 to 8 parts by weight of insulating carbon black is mixed with 100 parts by weight of the sealing material. By mixing the above amount of carbon black, it is possible to prevent a short circuit between wirings due to the seal member 203, and at the same time, it is possible to ensure the necessary light shielding properties and light resistance of the seal member 203.

  Finally, a manufacturing method of the liquid crystal display panel 120 having the above configuration will be described. First, the array substrate 201 and the counter substrate 202 are each manufactured by a conventional method. After the alignment films 210 and 215 are applied to the array substrate 201 and the counter substrate 202, an alignment process is performed in which a rubbing process is performed. Next, a sealing material is applied in a frame shape to the peripheral region of the counter substrate 202. A predetermined amount of insulating carbon black is mixed in the sealing material as described above. The sealing material is applied except for the liquid crystal material inlet.

  After the bead spacers are dispersed on the array substrate 201, the counter substrate 202 is superimposed on the array substrate 201 to obtain a laminate. After the gap width is adjusted, the sealing material is cured by ultraviolet rays or heat, and the light-shielding sealing member 203 is formed. After the curing process of the light-shielding seal member 203 is completed, a liquid crystal material is injected. The liquid crystal material is typically injected by vacuum. By placing the stacked substrates in the vacuum chamber, the gap between the two substrates is reduced in pressure, and the inlet is immersed in the liquid crystal material in that state, and the chamber is returned to atmospheric pressure by returning to the atmospheric pressure. The gap is filled with liquid crystal material. Thereafter, the inlet is sealed with an epoxy resin sealant.

  According to this embodiment, since carbon black, which is a black pigment, is mixed in the seal member, it is excellent in light resistance, and fading of the light-shielding seal member due to light can be effectively suppressed. In addition, by using insulating carbon black as the carbon black, sufficient light shielding properties can be ensured without causing a short circuit between wires in the seal member. In particular, by mixing the predetermined amount of the insulating carbon black into the seal member, it is possible to ensure the necessary light-shielding properties and light resistance and to prevent a short circuit between wirings. Further, the insulating carbon black can provide a reinforcing effect for the seal member.

  The polarizing plate can be formed on the outer surface of the transparent substrate or on the inner side of the transparent substrate. In this embodiment, the backlight unit does not have a diffusion plate, but the backlight unit can have a diffusion plate in order to further uniform the light.

It is a disassembled perspective view which shows schematic structure of the liquid crystal display module in this embodiment. It is sectional drawing which shows schematic structure of the liquid crystal display panel in this embodiment. It is a schematic diagram which shows schematic structure of the liquid crystal display panel in a prior art.

Explanation of symbols

100 liquid crystal display module, 101 backlight unit,
102 liquid crystal display panel, 103 prism sheet, 104 light guide plate,
105 reflective sheet, 106 frame, 107 cold cathode tube,
108 lamp reflector, 110, 111 drive circuit,
201 array substrate, 202 counter substrate, 203 seal member,
205 polarizing plate, 204 back side transparent substrate, 206 color filter layer,
207 Black matrix layer, 208 Protective layer,
209 ITO electrode layer, 210 alignment film, 211 front side transparent substrate,
212 Polarizing plate, 213 TFT, 214 Pixel electrode 300 Liquid crystal display panel, 301, 302 Transparent substrate, 303 Display area,
304 Seal member, 305 Spacer

Claims (6)

A first substrate;
A second substrate disposed opposite to the first substrate;
A plurality of pixels formed between the first substrate and the second substrate;
A light-shielding sealing member formed in an outer peripheral region of the plurality of pixels, fixing the first substrate and the second substrate, and mixed with insulating carbon black;
A display device.   The display device according to claim 1, wherein the light-shielding seal member has a volume resistance of 10E12 Ω · cm or more.   The display device according to claim 1, wherein the light shielding ratio of the light shielding seal member is 80% or more. Applying an uncured sealing material mixed with insulating carbon black on the first substrate;
Laminating a second substrate on the first substrate coated with the uncured sealing material;
Curing the uncured sealing material and fixing the first substrate and the second substrate;
A method for manufacturing a display device.   The display device according to claim 4, wherein the uncured sealing material applied to the first substrate is mixed with 1 to 15 parts by weight of insulating carbon black with respect to 100 parts by weight of the sealing base material. Manufacturing method.   The display device according to claim 5, wherein the uncured sealing material applied to the first substrate is mixed with 2 to 8 parts by weight of insulating carbon black with respect to 100 parts by weight of the sealing base material. Manufacturing method.

Images