JP2008158330A - Manufacturing method of liquid crystal display device using ferroelectric liquid crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a liquid crystal display element using a ferroelectric liquid crystal, wherein display unevenness due to distortion of a layer structure is eliminated and a wide process window is secured. <P>SOLUTION: In the manufacturing method of the liquid crystal display device using the ferroelectric liquid crystal having phase series of an isotropic phase, a chiral nematic phase or cholesteric phase and a smectic C phase, an alignment distortion region DA being an uneven display part generated from a spacer 20 as the starting point along a layer direction in a plane determined by a cone angle and an inclined angle of a layer of the ferroelectric liquid crystal is shifted so as to be superposed on a light shielding region BA by forming the spacer 20 in the light shielding region by a black matrix and controlling an alignment treatment direction of an alignment layer as a distortion region compensating alignment treatment direction CRD. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device, and more particularly to a method of manufacturing a liquid crystal display device using a ferroelectric liquid crystal that realizes high-speed response.

  Among ferroelectric liquid crystals, a ferroelectric liquid crystal having an isotropic phase, a chiral nematic phase (cholesteric phase), and a smectic C phase phase sequence undergoes a phase transition as shown in FIG. In the smectic C phase, the projection components of the liquid crystal molecules themselves onto the substrate are almost the same in the alignment processing direction. In addition, the angle of the layer on the substrate surface is determined by the cone angle when the smectic C phase is obtained, the tilt angle of the layer, and the angle in the orientation processing direction. Therefore, as shown in FIG. 12, there are two stable domains symmetrical with respect to the alignment processing direction.

  Therefore, conventionally, in order to convert the initial state in which two stable domains exist into a monodomain, the cooling rate when the chiral nematic layer (cholesteric layer) changes to the smectic C phase, DC (direct current voltage) application, and the like are performed. Some have been made (see, for example, Patent Document 1 and Patent Document 2). In addition, there is a method in which a partition is provided in a cell to control the orientation (for example, see Patent Document 3).

JP 2001-264822 A JP 2004-93964 A JP 7-318912 A

  However, the cooling rate in the vicinity of the temperature at which the chiral nematic phase (cholesteric phase) transitions to the smectic C phase, the cone angle change due to the subsequent temperature change, the surface condition of the substrate, etc., cause the orientation of the layer in the orientation direction in the substrate plane A region where the average liquid crystal alignment direction is different from the normal region along the tilt direction may occur starting from the spacer. When such a region occurs in the display area, the brightness in the black state increases and the contrast decreases. In addition, when such a region is unevenly generated in the panel surface, the image quality is poor.

  The present invention eliminates the occurrence of display unevenness due to the distortion of the layer structure and secures a wide process window in the liquid crystal display element using ferroelectric liquid crystal that realizes high-speed response by controlling the alignment of the spacers and the liquid crystal alignment direction. An object of the present invention is to provide a method of manufacturing a liquid crystal display element using a ferroelectric liquid crystal.

  The present invention relates to a method for manufacturing a liquid crystal display element using a ferroelectric liquid crystal having a phase sequence of isotropic phase, chiral nematic phase or cholesteric phase, and smectic C phase. A step of forming a spacer in a light blocking region by a black matrix formed on one of the pair of substrates, and orientation on at least one of the one substrate and the other substrate of the pair of substrates A step of forming a film, and an alignment treatment on the alignment film. In a completed liquid crystal display element, there is an alignment strain region that appears linearly starting from the position of the spacer with a specific inclination with respect to the alignment processing direction. Performing the alignment process in a strained region compensation alignment process direction having an inclination with respect to the light shielding region so as to overlap the light shielding region; A liquid crystal display element using ferroelectric liquid crystal, comprising: a step of bonding the pair of substrates so that the film is on the inside, and filling and sealing the ferroelectric liquid crystal therebetween It is in the manufacturing method.

  In the present invention, a non-uniform display portion, that is, an alignment strain region generated from the spacer as a starting point along the layer direction in the plane determined by the cone angle of the ferroelectric liquid crystal and the tilt angle of the layer, the spacer arrangement and the alignment film By controlling the direction of the alignment treatment to shift to the light-shielding region, it is possible to improve contrast and improve image quality.

  A method for manufacturing a liquid crystal display element using the ferroelectric liquid crystal of the present invention will be described below with reference to the drawings. First, the principle of the present invention will be described. FIG. 1 shows a schematic diagram of a cone in a smectic C phase of a ferroelectric liquid crystal. θ1 is the cone angle, and θ2 is the inclination angle of the layer with respect to the plane parallel to the glass substrate surface of the liquid crystal display element of the cone. These are characteristics determined by the ferroelectric liquid crystal material. θ3 is an apparent cone angle which is a cone angle in the plane parallel to the glass substrate surface due to the tilt of the cone by the tilt angle θ2.

  FIG. 2 is a schematic diagram when the cone of FIG. 1 is projected onto a plane parallel to the glass substrate surface. RD indicates the alignment treatment direction, and LCAD indicates the liquid crystal alignment direction. The projected component of the liquid crystal molecules themselves onto the substrate when the phase transition from the chiral nematic phase (cholesteric phase) to the smectic phase is allowed to stand at room temperature is slightly shifted from the alignment processing direction RD. As described above, the ferroelectric liquid crystal having the phase sequence of isotropic phase, chiral nematic phase (cholesteric phase), and smectic C phase forms a layer structure having an inclination angle with respect to the alignment processing direction in the substrate plane.

  For this reason, a strain along the layer may be generated due to a cooling temperature gradient in the vicinity of the transition temperature from the chiral nematic phase (cholesteric phase) to the smectic C phase and the subsequent temperature change. FIG. 3 shows the relationship between the light shielding area BA having a right-angled lattice shape composed of a vertical area and a horizontal area where light is blocked by the black matrix, the alignment treatment direction RD, the spacer 20, and the alignment distortion area DA. As shown in FIG. 3, in particular, when a spacer 20 such as a columnar spacer provided between a pair of substrates filled with liquid crystal is used, the alignment direction of the liquid crystal is distorted from the spacer 20 as a starting point. An orientation strain area DA is generated. In this orientation strain area DA, the average orientation direction of the liquid crystal is different from that of the normal area, so that the black luminance is increased and the contrast is lowered.

  Therefore, in the present invention, as shown in FIG. 4, the spacer 20 is arranged at the intersection of the vertical area and the horizontal area of the light shielding area BA where the light is shielded by the black matrix, and the alignment in the above-described substrate plane is performed. In consideration of the inclination angle of the layer from the processing direction, the alignment processing direction is determined as the strain region compensation alignment processing direction CRD so that the direction of the layer, that is, the direction of the alignment strain region DA overlaps with the light shielding region BA. A film orientation process is performed. The spacer 20 may be formed at least in the light shielding area BA.

  5 to 9 are sectional views showing a method for manufacturing a liquid crystal display element using a ferroelectric liquid crystal according to an embodiment of the present invention, and the manufacturing method will be described below according to this. First, one side is a TFT-array substrate on which signal lines such as data lines and gate lines are formed as display control parts, TFTs and pixel electrodes (not shown) at the intersections of the data lines and gate lines are formed, and the other is displayed A first substrate and a second substrate each made of a pair of glass substrates each including a color filter substrate on which a color filter, a common electrode, a black matrix and the like (both not shown) are formed as control components are prepared. The display control components formed on the first substrate and the second substrate are not limited to those described above.

  Then, as shown in FIG. 5, for example, spacers 20 are respectively formed in the light shielding region (see FIG. 4) of the first substrate 1a by a black matrix formed on the color filter substrate side. There is no limitation on the number of spacers 20. Also, the shape of the spacer 20 is not particularly limited, such as a column shape or a block shape.

  Next, as shown in FIGS. 6A and 6B, an alignment film 2 is formed on the surface of the first substrate 1a where the spacers 20 are formed and the main surface of the second substrate 1b. The alignment film 2 may be formed only on one of these.

  Next, as shown in FIG. 7, each alignment film 2 formed is subjected to an alignment process by rubbing. As shown in FIG. 4, the alignment processing at this time is performed by shielding the alignment strain region DA that appears linearly from the position of the spacer 20 with a specific inclination with respect to the alignment processing direction in the completed liquid crystal display element. This is performed in a strain region compensation alignment processing direction CRD having an inclination with respect to the light shielding region BA so as to overlap the region BA. The alignment process is not limited to rubbing, and the same effect can be obtained by performing the alignment process in the strain region compensated alignment process direction CRD in the case of the alignment process by irradiation with UV light or an ion beam.

  Next, as shown in FIG. 8, for example, a UV curable material is applied as a material of the sealant 3 to the peripheral edge of the first substrate 1a. In addition, you may apply | coat the UV hardening material used as the material of the sealant 3 to the 2nd board | substrate 1b side.

  After that, as shown in FIG. 9, the first substrate 1a and the second substrate 1b are bonded so that the spacer 20 and the alignment film 2 are inside, and the ferroelectric liquid crystal 4 is filled therebetween, and UV light is irradiated. Then, the UV curable material is cured and sealed.

  Further, there is another method shown below as the steps shown in FIGS. As shown in FIG. 8, a thermosetting material, for example, is applied as a material for the sealant 3 to the peripheral edge of the first substrate 1a. In addition, you may apply | coat the thermosetting material used as the material of the sealant 3 to the 2nd board | substrate 1b side.

  After that, as shown in FIG. 9, the first substrate 1a and the second substrate 1b are bonded so that the spacer 20 and the alignment film 2 are inside, the sealant is thermally cured, and then the ferroelectric liquid crystal 4 is filled. A UV curable encapsulant is applied to an injection port (not shown) filled with the ferroelectric liquid crystal 4, and the UV curable encapsulant is cured by irradiation with UV light to be sealed.

  In consideration of the above, the following experiment was conducted. A columnar spacer made of a photosensitive resin is formed on one of the pair of substrates. Then, an alignment film made of a polyimide film was formed on the main surface of each of the substrates, and an alignment process was performed by rubbing in a direction parallel to the light shielding region by the black matrix formed on the color filter substrate side. Next, a thermosetting material is applied as a sealant to the peripheral edge of one of the substrates, and then the two substrates are bonded so that the orientation direction is antiparallel (the direction is reverse and parallel), and the sealant is thermoset. Then, a ferroelectric liquid crystal having a cone angle of about 55 ° at room temperature was filled between the two substrates, and UV cured and sealed to produce a cell.

  The produced cell was heated to about 70 ° C., cooled to 55 ° C. at a cooling rate of about 2.5 ° C./min, and then returned to room temperature by natural cooling. During cooling, a direct current (DC) was applied in the range of ± 5 ° C. of the phase transition temperature between the chiral nematic phase and the smectic C phase. An alignment strain area DA starting from the columnar spacer 20 as shown in FIG. 10 is generated in a part of the panel at that time, which is deviated by about 70 ° from the alignment processing direction RD in the substrate plane, with a cone angle of 55 °, The value was almost the same as the value obtained when the inclination angle of the layer was 14 °. As a result of measuring the average alignment direction of the liquid crystal, the region A in FIG. 10 is shifted from the rubbing direction by 3.3 °, the region B is 2.3 °, and the region C is shifted by 4.3 °. It is considered that the alignment direction of the liquid crystal at C is influenced by the alignment direction of the liquid crystal on the side surface of the columnar spacer 20.

  Further, when the contrast was measured with a measuring machine using a wavelength of 546 nm, the contrast of only the region A was 661, but when the contrast was measured in the range including the regions B and C, it was 261. This is because the average orientation of the liquid crystal in the regions B and C is shifted from the region A, so that the black luminance does not sink (the luminance does not decrease to the design value) and the liquid crystal in the B region. This is thought to be because the orientation of is poor compared to others.

  Therefore, in the method for manufacturing a liquid crystal display device using the ferroelectric liquid crystal according to the present invention, the alignment process direction in the alignment process of the alignment film formed on the substrate is changed to a light shielding region where light is shielded by a conventional black matrix. By rotating from the parallel alignment treatment direction, the alignment strain region generated from the spacer as the starting point overlaps the light shielding region.

  From the above, the rubbing direction (orientation treatment direction) parallel to the conventional light shielding region shown in FIG. 10 was rubbed in the direction rotated by 20 ° as shown in FIG. 11 as the strain region compensation orientation treatment direction CRD. An alignment state in which the alignment strain region generated from the spacer as shown in FIG. 11 overlaps the light shielding region was obtained.

  As described above, the alignment strain region, which is a non-uniform display portion generated from the spacer, is formed along the layer direction in the plane determined by the cone angle of the ferroelectric liquid crystal and the tilt angle of the layer, and the arrangement of the spacers. By controlling the alignment direction of the liquid crystal to shift to the light-shielding region, it was possible to improve contrast and improve image quality, and to secure a wider process window.

It is a schematic diagram of the cone in the smectic C phase of a ferroelectric liquid crystal. It is a schematic diagram when the cone of FIG. 1 is projected on a surface parallel to the glass substrate surface. It is a figure which shows the relationship between the light shielding area | region, the alignment process direction, a spacer, and an orientation distortion area | region in the manufacturing method of the conventional liquid crystal display element. It is a figure which shows the relationship between the light-shielding area | region, the distortion area compensation alignment process direction, a spacer, and an orientation distortion area | region in the manufacturing method of the liquid crystal display element by this invention. It is sectional drawing for demonstrating the manufacturing method of the liquid crystal display element using the ferroelectric liquid crystal by one Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing method following FIG. It is sectional drawing for demonstrating the manufacturing method following FIG. It is sectional drawing for demonstrating the manufacturing method following FIG. It is sectional drawing for demonstrating the manufacturing method following FIG. It is a schematic diagram for demonstrating the result of the experiment conducted based on this invention. It is a schematic diagram for demonstrating the result of the experiment conducted based on this invention. It is a figure for demonstrating the ferroelectric liquid crystal which has a phase sequence of an isotropic phase, a chiral nematic phase, a cholesteric phase, and a smectic C phase.

Explanation of symbols

  1a, 1b substrate, 2 alignment film, 3 sealant, 4 ferroelectric liquid crystal, 20 spacer, A, B, C region, BA light shielding region, CRD strain region compensation alignment processing direction, DA alignment strain region, LCAD liquid crystal alignment direction, RD Orientation treatment direction, θ1 cone angle, θ2 tilt angle, θ3 Apparent cone angle.

Claims (5)

A method for producing a liquid crystal display element using a ferroelectric liquid crystal having a phase sequence of isotropic phase, chiral nematic phase or cholesteric phase, smectic C phase,
Forming a spacer in a light-shielding region of a black matrix formed on one of the pair of substrates of one of the pair of substrates;
Forming an alignment film on at least one of the side of the one substrate on which the spacer is formed and the other of the pair of substrates;
An alignment process is performed on the alignment film, and in a completed liquid crystal display element, an alignment strain region that appears linearly with a specific inclination with respect to the alignment processing direction as a starting point overlaps the light shielding region. Performing the alignment process in a strain area compensated alignment process direction having an inclination with respect to the light shielding area;
Bonding the pair of substrates so that the spacer and the alignment film are on the inside, filling the ferroelectric liquid crystal between them and sealing;
A method for producing a liquid crystal display element using a ferroelectric liquid crystal, comprising:   2. The method of manufacturing a liquid crystal display element using a ferroelectric liquid crystal according to claim 1, wherein an alignment film is formed on one of the pair of substrates, and alignment processing is performed in the strain region compensation alignment processing direction.   2. A liquid crystal display device using a ferroelectric liquid crystal according to claim 1, wherein an alignment film is formed on each of the pair of substrates, and each is subjected to an alignment process in the strain region compensation alignment process direction. Method.   4. The strong according to claim 1, wherein an inclination of the strain region compensation alignment processing direction with respect to the light shielding region is based on a cone angle of a smectic C phase of the ferroelectric liquid crystal and an inclination angle of the layer. A method of manufacturing a liquid crystal display element using a dielectric liquid crystal.   The method for manufacturing a liquid crystal display element using a ferroelectric liquid crystal according to any one of claims 1 to 4, wherein the black matrix and the light shielding region have a lattice shape forming a right angle.

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