JP2006139286A - Transflective ips (in-plane switching) liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transflective in-plane switching (TIPS) liquid crystal display (LCD) having a patterning retardation film. <P>SOLUTION: The transflective liquid crystal display has a pixel divided into a reflective sub-pixel 10a and a transmissive sub-pixel 10b and comprises: (a) an IP mode LC cell having an electrode layer 14a and an LC layer 12 which can be switched between different alignments by applying an electric field having a main component parallel to the LC layer plane; (b) front and back polarizing plates 13a, 13b; and (c) at least one retardation film 16 which is disposed between the front polarizing plate and the LC layer and which has a pattern consisting of a region 16a having specified axial retardation and a region 16b having substantially no retardation, with the retardation region arranged to cover substantially only the reflective sub-pixel. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an in-plane switching (IPS) mode transflective liquid crystal display (LCD) having a patterned retardation film.

  Due to the demand for mobile electronic devices, transflective LCDs have attracted attention. Transflective LCD devices use a backlight to illuminate the display, but power consumption can be reduced by utilizing ambient light under bright conditions. Such devices can therefore be viewed under any environmental conditions.

Transflective displays in which each pixel is divided into reflective and transmissive subpixels have been proposed for twisted and non-twisted switching cell structures (Kubo et al., IDW 1999, page 183-187; Baek et al., IDW 2000, page
41-44; WO 03/019276 (Patent Document 1); Roosendaal et al., Proc. SID 2003, page 78-81). A transmissive subpixel has transparent front and back electrodes, while a reflective subpixel has a transmissive front electrode and a reflective back electrode, eg, a patterning electrode obtained by “hole-in-mirror” technology Need structure. The transmission mode uses half-wavelength (λ / 2) light modulation (λ = wavelength of incident light), and the reflection mode uses quarter-wavelength (λ / 4) light modulation. It has been proposed that the reflective subpixel be approximately half the cell gap of the transmissive subpixel by using (LC layer thickness).

In order for a reflective subpixel to work with a transmissive subpixel, an achromatic (or “broadband”) quarter wave film (AQWF) is required to produce circularly polarized light (AQWF is preferably all It exhibits an optical delay of λ / 4 in a wide wavelength band including the visible spectrum, and is formed, for example, by combining a half-wave film (HWF) having an optical delay of λ / 2 and QWF. Since AQWF also covers transmissive pixels, it is necessary to place an equivalent AQWF on the backlight side of the cell.
International Publication No. 03/019276 Pamphlet German Patent Application Publication No. 4000451 European Patent Application No. 0588568

Typically, a transflective display requires four retardation plates, two on the front (one QWF and one HWF) and two on the back (one QWF and one HWF). is there. To reduce the number of films, Beck et al. (Baek
et al., IDW 2000, p. 41-44) proposes that non-twisted LC cells be part of the AQWF, which makes the cell QWF and only requires two HWFs. As a result, the cell actually switches from AQWF to a simple half-wave plate. This idea reduces the number of films and still allows the reflective state to operate in conjunction with transmission, but the transmission state still has the problems of low contrast, narrow viewing angle, and poor chromaticity.

  WO 03/019276 and Van der Zande et al. (Van der Zande et al., Proceedings of the SID 2003, p. 194-197) describe patterned retardation plates with different retardation for reflection and transmission subpixels. A transflective TN cell structure with a sapphire has been reported. By using the patterning phase difference plate, the degree of freedom in designing a transflective cell is further increased, and the number of films necessary for improving display quality can be reduced. However, in the transmissive state, contrast, viewing angle and chromaticity are still insufficient.

  In particular, there is a problem with a narrow visual field range, and therefore there is not much interest in using a transflective display in a large-screen display device for on-site broadcasting and further for outdoor television.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a transflective display that does not have the above-described drawbacks, exhibits high contrast and brightness and low color shift over a wide range of viewing angles, and is easy to manufacture in a time efficient and cost effective manner There is to do. Other objects of the invention will be readily apparent to those skilled in the art from the following detailed description.

  The inventors have found that these objectives can be achieved by providing a transflective in-plane switching (IPS) mode display (TIPS) as claimed in the present invention.

Compared to conventional display modes such as TN or VA mode, where the electric field is applied substantially perpendicular to the plane of the LC layer, the IPS mode has an electric field substantially parallel to the plane of the LC layer. Is characterized in that is applied. Conventional IPS displays are disclosed, for example, in DE-A-4000451 (Patent Document 2) and EP-A-0588568 (Patent Document 3). In conventional displays, IPS mode has been reported to have advantages in many fields compared to, for example, VA and TN modes (Endoh
et al., IDW 1999, p.187-190). In addition, suitable compensation (Kim,
et al., IMID 2003, p.1-4) or multidomain structure (Klausmann
et al., J. Appl. Phys., 1998. 83 (4), p. 1854-1862), IPS mode has been reported to provide a very good LCD visual experience. IPS technology is particularly seen as a viable design for LC-TV that can meet the strict limitations on viewing angle and color shift in transmissive devices. However, the above document does not disclose the transflective IPS display claimed in the present invention.

  The current technology for transflective devices is limited in the use of IPS mode because it requires the use of circularly polarized light in the reflective state. Due to the nature of the IPS mode in which the director of the LC medium is reoriented in the plane of the display when an electric field is applied, the circularly polarized light is also affected regardless of whether the LC cell is switched or not, and no contrast is required between the states. Is done.

  The inventors have further found that these limitations can be overcome by properly designing an IPS display. For example, an IPS LC cell is a QW component that can switch an AQW phase difference plate, and by combining it with a non-switched HWF, the IPS cell does not try to influence circularly polarized light, but takes linearly polarized light, Since it can be converted to a circle or left straight, it is possible to use IPS in a transflective device. Further, to improve contrast, viewing angle and chromaticity, HWF is used as a patterned in-cell retardation plate having an HWF area covering the reflective subpixel and a non-retardation area covering the transmissive subpixel. Even if the optical performance can be improved, the number of films is also reduced, thereby reducing the thickness, increasing the brightness, and making the manufacturing process easy and inexpensive.

<Definition of terms>
The term “film” includes a rigid or flexible, self-holding or self-supporting film with mechanical stability, as well as a coating or layer on a support substrate or between two substrates.

  The term “liquid crystal or mesogenic material” or “liquid crystal or mesogenic compound” refers to a material comprising one or more rod-shaped, board-shaped or disk-shaped mesogenic groups, ie groups having the ability to induce liquid crystal (LC) phase behavior or Means a compound. LC compounds having rod-shaped or board-shaped groups are also referred to in the art as “calamitic” liquid crystals. LC compounds having disc-shaped groups are also referred to in the art as “discotic” liquid crystals. A compound or material having a mesogenic group need not necessarily exhibit an LC phase itself. It is also possible that they exhibit LC phase behavior only when they are in a mixture with other compounds, or only when mesogenic compounds or materials or mixtures thereof are polymerized.

  For brevity, the term “liquid crystal material” is used below for both mesogenic and LC materials.

  A polymerizable compound having one polymerizable group is also referred to as a “monoreactive” compound, and a compound having two polymerizable groups is referred to as a “direactive” compound and has more than two polymerizable groups. Compounds having are referred to as “multi-reactive” compounds. Compounds without a polymerizable group are also referred to as “non-reactive” compounds.

  The term “reactive mesogen” (RM) means a polymerizable mesogenic compound or a liquid crystal compound.

  The term “director” is known in the prior art and means the preferred orientation direction of the long molecular axis (in the case of calamitic compounds) or short molecular axis (in the case of discotic compounds) of the mesogenic group in the LC material.

  In films containing uniaxially positive birefringent LC material, the optic axis is provided by a director.

  The term “homeotropic structure” or “homeotropic orientation” refers to a film whose optic axis is substantially perpendicular to the film plane.

  The term “planar structure” or “planar orientation” refers to a film whose optical axis is substantially parallel to the film plane.

  The term “A plate” refers to an optical retardation plate that uses a layer of uniaxially birefringent material with an extraordinary axis oriented parallel to the layer plane.

  The term “C-plate” refers to an optical retardation plate that uses a layer of uniaxially birefringent material whose anomalous axis is perpendicular to the layer plane.

  In A- and C-plates with optically uniaxial birefringent liquid crystal material with uniform orientation, the optical axis of the film is given by the direction of the extraordinary axis.

  An A plate or C plate having an optical uniaxial birefringent material with positive birefringence is also referred to as a “+ A / C plate” or “positive A / C plate”. An A plate or C plate having a film of optically uniaxial birefringent material with negative birefringence is also referred to as a “−A / C plate” or “negative A / C plate”.

  “E-mode” refers to a twisted nematic liquid crystal display (TN-LCD) whose incident light polarization direction is substantially parallel to the director of the LC molecule, ie, an extraordinary (E) refractive index direction when entering the display cell. ). “O-mode” refers to a TN-LCD that, when entering the display cell, has incident polarization substantially perpendicular to the director, ie, in the normal (O) refractive index direction.

  Unless otherwise noted, the term “polarization direction” of a linear polarization means means the polarization quenching axis. For example, in the case of a stretched plastic polarizing film containing a dichroic iodine dye, the extinction axis usually corresponds to the stretching direction.

The present invention relates to a transflective liquid crystal display (LCD) having one or more pixels divided into reflective and transmissive subpixels.
(A) an LC cell in in-plane switching (IPS) mode having an electrode layer and an LC layer that can be switched between different orientations when an electric field having a main component parallel to the LC layer surface is applied. An LC cell in which the layer is preferably provided inside the transparent substrate,
(B) Front and back polarizing plates sandwiching LC cells and having front and back polarization directions as optional components that may not be present,
(C) It is disposed between the front polarizing plate and the LC layer, and has a pattern of a region having a predetermined retardation and a region having substantially no retardation, and the retardation region is substantially a reflective subpixel. The present invention relates to a transflective liquid crystal display having at least one retardation film disposed so as to cover only the liquid crystal display.

  The present invention further relates to a patterned HWF used in a TIPS-LCD having transmissive and reflective sub-pixels and having a pattern of regions having half-wavelength (λ / 2) retardation and regions having substantially no retardation.

  As mentioned above, the first problem with using IPS in a transflective device is that circularly polarized light is affected by the birefringent material regardless of its orientation, and in an arrangement with an IPS cell. The conversion from right circular polarization to left circular polarization is that when the cell is switched to another arrangement in the plane, it does not have contrast because it does the same thing.

  In order to solve this problem, the IPS cell according to the present invention is made part of the element that generates circularly polarized light. Given that a standard AQWF consists of HWF and QWF oriented to produce an achromatic QWF doublet, it is possible to replace the QWF with a switchable LC cell there. Therefore, the IPS mode can be used, and the number of necessary films can be reduced at the same time. It is ideal for the reflective state, since it is possible to switch the LC cell to produce circularly polarized light in the dark state and linearly polarized light in the bright state.

  The second problem concerns the display design in the transmissive state. In the reflective subpixel, light passes through the LC layer twice, so its cell gap is preferably about 0.5 times the cell gap of the transmissive subpixel, giving the same retardation. By doing so, the transmissive LC cell effectively corresponds to the two QWFs applied from back to back. That means that using crossed polarizers results in unacceptably high chromaticity or low contrast. In order to overcome this problem, the reflective part and the transmissive part are operated together by using a patterning phase difference plate. The patterned retardation plate is formed of, for example, a patterned reactive mesogenic material that provides HWF retardation on the reflective subpixel and optically isotropic regions on the transmissive subpixel.

  In this way, by combining the advantages of the IPS transmission optical system with the desired reflection optical system, it is possible to produce a transflective display that is excellent in many fields.

  In the reflective subpixel, the LC layer preferably has a quarter wavelength retardation and thus has the function of a switchable quarter wavelength retarder. The retardation of the LC layer at the reflective subpixel is preferably 0.25 times the incident light wavelength. Particularly preferably, the retardation value is 90 to 200 nm, very preferably 130 to 145 nm.

  For transmissive subpixels, the retardation of the LC layer is preferably 0.5 times the incident light wavelength, or twice the retardation of the LC layer of the reflective subpixel. Particularly preferably, the retardation value is from 180 to 400 nm, very preferably from 260 to 290 nm.

  A suitable cell gap can be selected depending on the birefringence of the LC medium used. A suitable cell gap is, for example, in the range of 0.5-5 μm.

  Unless otherwise noted, the above retardation values refer to a center wavelength of 550 nm.

A preferred TIPS-LCD according to the present invention is:
(A) the following elements: (a-1) first and second substrate surfaces that are parallel to each other and at least one of which is transparent to incident light;
(A-2) An array of non-linear electrical elements provided on one of the substrates that can be used to individually switch individual pixels of the LC cell, wherein the elements are preferably active, such as transistors An element, an array which is very preferably a TFT,
(A-3) Any one of the primary colors red, green and blue (R, G, B) provided on one of the substrates, preferably on the opposite side of the substrate having the array of non-linear elements. A color filter array having a pattern of various pixels that pass through the color filter array, wherein the color filter may be covered with a planarization layer,
(A-4) an electrode layer provided on the inner side of the first or second substrate, which is designed so that a main component can apply an electric field parallel to the surface of the LC layer;
(A-5) As an optional element (optional), an alignment layer provided on the electrode,
(A-6) a liquid crystal (LC) cell having an LC medium switchable between at least two different orientations by applying an electric field;
(B) a first linearly polarizing plate provided on the first side of the LC cell;
(C) a second linearly polarizing plate provided on the second side of the LC cell; and (d) a different retardation disposed between the first substrate and the second substrate of the LC cell. And / or at least one patterned retardation film having a pattern of a region having an orientation, and the orientation directions of the polarizing plate, the retardation film and the LC layer are as defined above and below.

  Suitable IPS electrode designs are well known in the art and are described in the literature for providing an electric field substantially parallel to the plane of the LC layer, such as interdigited electrodes.

  The patterning retardation film has a region having a predetermined on-axis retardation (a value of <0 or> 0) and a region having no on-axis retardation. In the retardation region of the film, the optical axis is preferably parallel to the film plane (A plate symmetry). In the non-retardation region, the film has, for example, an optically isotropic material, or the optical axis is, for example, perpendicular to the film plane (C-plate symmetry).

  In the transflective LCD according to the present invention, a switchable LC cell is formed, and a patterning phase difference plate is provided between substrates including a switchable LC medium (using “in-cell”). Compared to conventional displays where an optical retardation plate is usually placed between the LC cell and the polarizer, the use of the optical retardation plate in the cell has several advantages. For example, a display in which an optical retardation plate is attached to the outside of a glass substrate that forms an LC cell usually has a parallax problem that can significantly impair the viewing angle characteristics. When the retardation plate is provided inside the LC display cell, the parallax problem can be reduced or even avoided.

  Preferably, the patterned retardation plate is disposed on the front side of the display, preferably between the color filter and the LC medium, or between the color filter and the planarization layer if a planarization layer is present. Deploy.

  The thickness of the patterning retardation plate is preferably 0.5 to 3.5 microns, very preferably 0.6 to 3 microns, and most preferably 0.7 to 2.5 microns.

  The patterning retardation plate is preferably a half-wave retardation film (HWF) having an on-axis retardation (ie, 0 ° viewing angle) of preferably 180 to 400 nm, most preferably 200 to 350 nm.

  When the patterning retardation plate is a quarter wave retardation film (QWF), it preferably has an on-axis retardation of 90-200 nm, most preferably 100-175 nm.

  An LCD assembly according to a preferred embodiment of the present invention is schematically illustrated in FIG. The upper side of FIG. 1 corresponds to the front side of the display, that is, the viewer side. The lower side of FIG. 1 corresponds to the back side of the display, that is, the backlight side. FIG. 1 shows a layer of switchable LC medium 12 confined between two transparent plane parallel substrates 11a / b, eg glass substrates, and two with crossed polarization directions sandwiching the substrates. A pixel 10 of an LCD having a number of polarizing plates 13a / b is shown by way of example.

  This display further has a pattern of the reflective electrode 14a and the transparent electrode 14b on the back side of the LC layer, thereby forming two sets of reflective subpixels 10a and transmissive subpixels 10b. The transparent electrode 14b is a layer of indium tin oxide (ITO), for example. The reflective electrode 14a includes, for example, a reflective layer 14a2 that returns light transmitted through the ITO layer 14a1 and the LC medium to the viewer again (indicated by a bent arrow). The reflective layer 14a2 is, for example, a metal layer (eg, Al), or can be formed as a mirror having a hole (the area of the mirror is in the reflective subpixel and the hole is in the transmissive subpixel). The electrode layer 14a1 and the mirror 14a2 can be adjacent layers, or may be spatially separated as shown in FIG.

  The display further comprises a color filter 15 having red, green and blue pixels and a patterned in-cell retardation film 16. The in-cell retardation plate 16 has a pattern of a region 16a having a predetermined retardation (value is <0 or> 0) and a region 16b having no on-axis retardation. The retardation region 16a covers the reflective subpixel 10a, and the non-retardation region 16b covers the transmissive subpixel 10b.

  When the display is of an active matrix type as shown in FIG. 1, it can be used to individually switch individual pixels, such as TFTs, on the side close to the electrode 14, preferably on the side opposite to the color filter 15 side. It also has an array of non-linear electrical elements 17 used.

  The reflective and transmissive subpixels 10a / b preferably have different cell gaps, as indicated by the double arrows in FIG. Preferably, the cell gap of the transmissive subpixel 10b is twice the cell gap of the reflective subpixel 10a.

  To obtain different cell gaps, the reflective sub-pixel has a step 18 that can be formed from, for example, a transparent resin (such as a photoresist). The step 18 may exist on the front side or the back side of the LC cell.

  In order to induce or enhance the desired surface alignment in the LC medium 12, the electrodes 14a / b may be covered by an alignment layer (not shown). Furthermore, as an optional configuration, an alignment layer (not shown) may be provided between the color filter 15 and the patterning in the cell retardation film 16. The display also has a backlight on the back side (not shown).

  In the TIPS-LCD according to the present invention, an optical layer preferably including a polarizing plate, an LC cell, an in-cell retardation film, and an additional retardation film as an optional element, the optical axes of which have a specific orientation direction with respect to each other. Arrange to have.

  The operation of the TIPS-LCD according to a preferred embodiment of the present invention will be exemplarily described below.

  The TIPS-LCD according to the first preferred embodiment of the present invention has a laminated structure of optical layers as shown in FIG. 2 in a sectional view, which is divided into a reflective sub-pixel 12a and a transmissive sub-pixel 12b. It includes an LC layer, a reflector 14a, front and back polarizing plates 13a / b, and an in-patterning cell HWF16. The in-cell HWF 16 has a pattern of a half-wavelength region 16a that covers the reflective subpixels and an optically isotropic region 16b that covers the transmissive subpixels. The transmission axes of the polarizing plates 13a / b are oriented at + 45 ° and −45 °, respectively, and the optical axis of the HWF region 16a is oriented at + 22.5 °.

  The LC layer thickness (d / 2) of the reflective subpixel is substantially 0.5 times the thickness of the transmissive subpixel (d). The retardation Δn · d of the LC layer (Δn is the birefringence of the LC medium) is such that, for incident light, the transmissive subpixel has a substantially half-wave retardation and the reflective subpixel is substantially 1 Selected to have / 4 wavelength retardation.

  The transmissive subpixel operates in the same manner as a normal IPS cell. The LC layer has a substantially planar alignment in a selected or bright (white) state (electric field applied) and a non-selected or dark (black) state (no electric field applied). In the dark state, for example, the LC director orientation provided by the cell surface rubbing direction is preferably parallel and perpendicular to the front and back polarizer directions, respectively. In the bright state, the majority of the LC layer in the cell switches the director orientation to preferably ± 45 ° (in a monodomain IPS LCD) relative to the front and back polarizer directions (usually applying an electric field to the IPS display). However, since some LC molecules do not rearrange with the electric field, eg, LC molecules on the substrate surface, an average director must be assumed to calculate switching). Light entering the display from the backlight side is linearly polarized by the back polarizer. In the dark state, its polarization orientation is not affected, so it is blocked by crossed front polarizers. In the bright state, its polarization direction is rotated by the LC layer (having an average orientation of ± 45 ° and a half-wave retardation) so that it can pass through the front polarizer.

  In another preferred embodiment, the TIPS-LCD has a viewing angle characteristic in which the transmissive subpixel (10b) is subdivided into a plurality (eg, two) domains having different orientation directions of the LC director in the white state. It is an improved multi-domain display. It can be achieved, for example, by providing a multi-domain alignment layer that induces different orientation directions as desired, or by a specific electrode design. In the preferred TIPS-LCD, the transmissive subpixel has two domains with both + 45 ° and −45 ° LC director orientation directions (in the white state) relative to the front and back polarizer directions. This creates problems with very wide viewing angles and very low chromaticity. The reflective subpixel is not necessarily required to have a multi-domain structure because it is self-compensating, but it may be multi-domain.

  The reflection state is formed by using the reflective sub-pixel (10a) of the LC cell as the switchable QW part of the AQW retardation plate (AQW retardation plate is a combination of QW and HW retardation plates). is there). The HWF portion is formed by a patterning retardation plate (16a) whose optical axis is oriented at 22.5 ° with respect to the extinction axis of the front polarizing plate, and therefore light (light transmitted by the front polarizing plate). The plane of polarization is rotated 45 °.

  In the dark state, when light interacts with the IPS cell, it is polarized in a plane at 45 ° from the slow axis of the IPS cell. The LC orientation direction in the non-selected state is preferably the same as in the reflective and transmissive subpixels. Since the IPS cell has only a quarter wavelength retardation due to its small thickness, it converts linearly polarized light into circularly polarized light. The combination of HWF and QW-IPS cell (to form an AQW retarder) means that the light is circularly polarized over the entire visible spectrum. When light strikes the reflector, it is converted to circularly polarized light in the opposite direction. When returning through the combination of QW-IPS and HWF, the light is blocked because it is converted to linearly polarized light oriented in the plane of the extinction axis of the front polarizer.

  Switching the QW-IPS cell by + 45 ° or −45 ° (because it is self-compensating, so there is no need for dual domain in the reflective cell) will produce a bright state. At this time, the light rotated by the HWF is parallel or perpendicular to the slow axis of the cell. The light is not converted into circularly polarized light but hits the reflector as linearly polarized light. The linearly polarized light passes again through the switched IPS cell. When passing through the HWF, its polarization direction rotates and returns to the direction of the transmission axis of the front polarizing plate, so that light can pass through the front polarizing plate.

  The above method is a preferred method that allows the TIPS-LCD to operate without compromising any of the other conditions. By using only one retardation film to produce achromatic circularly polarized light, the design becomes very attractive and further optical compensation of the transmission state is possible. For example, by using an A plate and a + C plate retardation plate on the back side of the display, it is possible to compensate for light leakage of the polarizing plate at off-axis positions of 45 °, 135 °, 225 °, and 315 °. .

  Therefore, the TIPS-LCD according to the second preferred embodiment of the present invention has a laminated structure of optical layers as exemplarily shown in FIG. 3 including the optical components shown in FIG. The display further includes a back surface + C plate phase difference plate 19 having an optical axis perpendicular to the film surface and a back surface + A plate phase difference plate 20 having an optical axis parallel to the film surface. The transmission axes of the polarizing plates 13a / b are oriented at + 45 ° and −45 °, the optical axis of the in-cell HWF region 16a is oriented at + 112.5 °, and the optical axis of the + A plate 20 is +45. Oriented at °.

  By adding + A and + C plates, contrast over a wide viewing angle is improved. Therefore, a contrast ratio of 100: 1 or more can be obtained at a viewing angle of 80 ° or more, which is ideal for a transflective television.

  The in-cell retardation plate further shows a pattern of R-, G-, and B-pixels with three different retardations covering the reflective sub-pixels, and the efficiency of converting linearly polarized light into circularly polarized light is red (R), green It is also possible to select the retardation at the R-, G- and B-pixels of the film to be optimized for each of the (G) or blue (B) colors. The arrangement of the retarder is such that its R-, G- and B-pixels cover the corresponding reflective R-, G- and B-subpixels.

  For R, G, B-pixelated QWF, the retardation values at R-, G-, and B-pixels are preferably selected as follows.

  For red light with a wavelength of 600 nm, the retardation is 140-190 nm, preferably 145-180 nm, very preferably 145-160 nm, most preferably 150 nm.

  For green light with a wavelength of 550 nm, the retardation is 122-152 nm, preferably 127-147 nm, very preferably 132-142 nm, most preferably 137 nm.

  For blue light with a wavelength of 450 nm, the retardation is 85-120 nm, preferably 90-115 nm, very preferably 100-115 nm, most preferably 112 nm.

  For R, G, B-pixelated HWF, the retardation value at R-, G- and B-pixels is preferably twice the preferred value of QWF above.

  In the LCD according to the present invention, the linear polarizing plate is a standard absorbing polarizing plate including, for example, a stretched dye-doped plastic film. For example, it is also possible to use a polymerized LC material having a uniform planar orientation as described in EP-A-0397263 and a linear polarizing plate having a visible light absorbing dichroic dye.

  The A plate is, for example, a stretched plastic film or a film of polymerized LC material having a planar structure as disclosed, for example, in WO 98/04651. The + C plate is, for example, a film of polymerized LC material homeotropic structure as disclosed, for example, in WO 98/00475. It is also possible to use other A-plate and C-plate retardation plates known in the prior art, for example as disclosed in US Pat. No. 5,619,352.

  The polarizing plate and the external retardation plate such as the A plate and the C plate can be attached to the substrate with an adhesive layer such as a commercially available PSA film (pressure sensitive adhesive).

  The in-cell retardation plate is preferably a film having a polymerized LC material that may have a retardation and / or orientation pattern. By applying it in the cell (ie, in the substrate on which the LC cell is formed), the parallax problem can be avoided, and by patterning with UV light, an isotropic region is formed throughout the transmissive part of the display. can do. Basically, any patterning retardation plate applicable in the cell can be used.

  Unpatterned QWF and HWF containing polymerized LC material are known in the prior art and are described, for example, in EP-A-1363144.

Patterning retardation plates suitable for use in LCDs according to the present invention have been reported in the prior art. For example, the report of WO 03/019276 and Van der Zande et al. (Van der Zande
et al., Proceedings of the SID 2003, p. 194-197) can be used.

Particularly preferred is a patterning optical retardation film described in WO2004 / 090025A1. Preferably the patterning film is
a) providing a polymerizable LC material layer containing at least one photopolymerizable compound on a substrate;
b) arranging the LC material layer in a planar orientation;
c) exposing the LC material in the layer or selected areas of the layer with light irradiation, preferably UV irradiation, which causes isomerization of the isomerizable compound;
d) a method of fixing the orientation by polymerizing the LC material in at least a part of the exposed region of the material; and e) an optional step of removing the polymerized film from the substrate. There,
Manufactured by a method in which the retardation and / or orientation of the LC material is controlled by changing the amount and / or type of photopolymerizable compound and / or by changing the intensity and / or exposure time of light irradiation. Is done.

  Preferably the LC material is exposed to light that causes photoisomerization and photopolymerization. The photoisomerization step and the photopolymerization step are performed under different conditions, particularly in different gas atmospheres, particularly preferably the photoisomerization is performed in the presence of oxygen, and the photopolymerization is performed in the absence of oxygen. Is called.

  Particularly preferred is a patterned film comprising a polymerized liquid crystal (LC) material having at least two regions having different retardations and at least two regions having different orientations of the LC material, the regions having different retardations being oriented. May be different, or they may be different regions. Thus, for example, the film has a pattern of first and second regions, and the first and second regions differ in both retardation and orientation. In another embodiment, the film has a pattern of first, second and third regions, wherein the first and second regions are different in either retardation and orientation, and the third The region differs from at least one of the first and second regions in at least one of retardation and orientation. In another embodiment, the film has a pattern of first, second, third and fourth regions, each having a different retardation from each other, two of the regions being Have the same orientation. Other combinations are possible.

  Apart from the specific conditions and materials described in the present invention, steps a) to e) are known to those skilled in the art and can be carried out according to standard procedures described in the literature.

  Polymerizable LC materials include photoisomerizable compounds, preferably photoisomerizable mesogenic or LC compounds, very preferably photoisomerizable compounds that are also polymerizable. Isomerizable compounds change shape when exposed to light of a specific wavelength, such as UV light, for example by EZ-isomerization. This creates a perturbation of the uniform planar orientation of the LC material, resulting in a decrease in birefringence. Since the optical retardation of the oriented LC layer is given as the product d · Δn of the layer thickness d of the LC material and birefringence Δn, the decrease in birefringence also causes a decrease in retardation in the irradiated portion of the LC material. Next, the orientation and retardation of the LC material is fixed by in situ polymerization of the irradiated area of the entire film.

  The polymerization of the LC material is performed, for example, by thermal polymerization or photopolymerization. When using photopolymerization, the type of light used for photoisomerization and photopolymerization of the LC material may be the same or different. When using light of a wavelength that causes both photoisomerization and photopolymerization of the LC material, for example UV light, the photoisomerization and photopolymerization steps are preferably performed under different conditions, in particular under different gas atmospheres. In that case, the photoisomerization is preferably performed in the presence of oxygen such as in the air, and the photopolymerization is performed in the absence of oxygen, particularly preferably in an inert gas atmosphere such as a rare gas such as nitrogen or argon. . When the isomerization step is carried out in the presence of oxygen or in air, the oxygen prevents the polymerization by scavenging free radicals from the photopolymerization agent present in the material. In the next step, polymerization is caused by removing oxygen or air and replacing it with an inert gas such as nitrogen or argon. Thereby, the control of the process steps can be improved.

  The degree of isomerization in the layer of LC material, and thus the change in birefringence, can be controlled, for example, by changing the irradiation dose, ie light intensity, exposure time and / or power. Furthermore, by providing a photomask between the light source and the LC layer, a film having a pattern of regions or pixels having different specific retardation values can be manufactured. For example, a film composed of two different retardation values can be formed using a simple monochromatic mask. More complex films showing multiple regions of different retardation can be formed using a tone mask. After obtaining the desired retardation value, the LC layer is polymerized. In this way, a polymer retardation film having a retardation value ranging from that of the initial LC layer to zero can be formed. The retardation value in the initial LC material layer is controlled by appropriate selection of the layer thickness and the type and amount of the individual components of the LC material.

  The polymerizable LC material is preferably a nematic or smectic LC material, in particular a nematic material, preferably comprising at least one direactive or polyreactive achiral RM and optionally one or more monoreactive achiral RMs. . By using di- or multi-reactive RMs, a cross-linked film is obtained in which the structure is permanently fixed and exhibits high mechanical stability against external influences such as temperature or solvent and high optical properties. Therefore, a film containing a crosslinked LC material is particularly preferred.

The polymerizable mesogenic mono-, di- and polyreactive compounds used in the present invention are known per se and are, for example, standard works of organic chemistry (eg Houben-Weyl, Methoden der organischen Chemie, Thieme-Verlag). ,
By the method described in Stuttgart).

  Examples of suitable polymerizable mesogenic compounds that can be used as monomers or comonomers in the polymerizable LC mixture are disclosed, for example, in WO 93/22397, EP 0261712, DE 19504224, WO 95/22586, WO 97/00600 and GB 2351734. However, the compounds disclosed in these documents are to be regarded merely as examples and are not intended to limit the scope of the invention.

  Examples of particularly important polymerizable mesogenic compounds (reactive mesogens) are listed below, but these should only be illustrative and do not limit the invention in any way: It is for demonstrating this invention.

In the above formula, P is a polymerizable group, preferably an acrylic, methacrylic, vinyl, vinyloxy, propenyl ether, epoxy, oxetane or styryl group; x and y are the same or different integers from 1 to 12; Is 1,4-phenylene, or 1,4-cyclohexylene, which may be mono-, di- or tri-substituted by L ¹ ; u and v are, independently of one another, 0 or 1; Z ⁰ Is —COO—, —OCO—, —CH ₂ CH ₂ —, —CH═CH—, —C≡C— or a single bond; R ⁰ is a polar or non-polar group; L, L ¹ and L ^2, independently of one another, H, F, Cl, may be halogenated with a CN or 1-7 C atoms alkyl, alkoxy, alkylcarbonyl, alkylcarboxy Yloxy, it is alkoxycarbonyl or alkoxycarbonyloxy group; r is 0, 1, 2, 3 or 4. The phenyl ring in the above formula may be substituted by 1, 2, 3 or 4 groups L.

The term “polar group” in this context is F, Cl, CN, NO ₂ , OH, OCH ₃ , OCN, SCN, optionally fluorinated alkylcarbonyl, alkoxycarbonyl, alkyl having 4 or less C atoms. By carbonyloxy or alkoxycarbonyloxy group is meant a group selected from mono-, oligo- or polyfluorinated alkyl or alkoxy groups having 1 to 4 C atoms. The term “nonpolar group” is not covered by the above definition of “polar group” and may be halogenated alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl having one or more, preferably 1 to 12 C atoms. Means an alkylcarbonyloxy or alkoxycarbonyloxy group.

  Particularly preferred are mixtures comprising one or more polymerizable compounds having a high birefringence acetylene group or tolan group, such as, for example, the compound of formula R7 above. Suitable polymerizable tolans are described, for example, in GB 2351734.

  Suitable photoisomerizable compounds are known. Examples of the photoisomerizable compound include azobenzenes, benzaldoximes, azomethines, stilbenes, spiropyrans, spirooxazines, fulgides, diarylethenes, and cinnamic acid compounds. Further examples include 2-methyleneindan-1-ones as described, for example, in EP1247796, and (bis-) benzylidenecycloalkanones, as described in EP1247797.

  Particularly preferably, the LC material comprises one or more cinnamic acid compounds, in particular cinnamic acid compounds (cinnamate esters) reactive mesogens (RM) as described, for example, in US5770107 (P0095421) and EP02008230.1. Very preferably the LC material comprises one or more cinnamic acid compounds RM (cinnamate RM) selected from the formula

Where
P, A and v have the meanings as above; L has the meaning of any one of L ¹ as defined above; Sp is, for example, alkylene having 1 to 12 C atoms or alkyleneoxy, etc. A spacer group or a single bond; R is Y or R ^{0 as} defined above, or P-Sp; Here, Y is the above-mentioned polar group, that is, F, Cl, CN, NO ₂ , OH, OCH ₃ , OCN, SCN, alkylcarbonyl, alkoxy which may be fluorinated having 4 or less C atoms. It means a group selected from a carbonyl, alkylcarbonyloxy or alkoxycarbonyloxy group, or a mono-, oligo- or polyfluorinated alkyl or alkoxy group having 1 to 4 C atoms.

  Particularly preferred are cinnamic acid compounds RM having a polar end group Y as defined above. Highly preferred are cinnamic acid compounds RM of the formula III and IV where R is Y.

  The light irradiation used to cause photoisomerization in the LC material depends on the type of compound capable of photoisomerization and can be easily selected by those skilled in the art. In general, compounds that exhibit photoisomerization induced by UV light are preferred. For example, in the case of cinnamic acid compounds such as compounds of formula III, IV and V, UV light having a wavelength in the UV-A range (320-400 nm) or 365 nm is typically used.

  Polymerizable LC materials containing high content photoisomerizable compounds allow easy control and adjustment of the retardation of optical retardation films, so such materials are for the purposes of the present invention. Has been found to be particularly useful. For example, an alignment layer of an LC mixture containing a photoisomerizable compound with a high content is subjected to light irradiation that induces photoisomerization, and the decrease in retardation increases as the irradiation time increases. Show. For such materials, the retardation can be varied within a wider range of values and more precisely controlled, for example by changing the irradiation time, compared to a material that shows only a slight retardation change. Can do.

  Thus, according to a preferred embodiment of the present invention, the polymerizable component of the polymerizable LC material comprises at least 12 mol% of photoisomerizable compound, preferably cinnamic acid compound RM, most preferably formulas III, IV and Including those selected from V.

  The term “polymerizable component” refers to polymerizable mesogenic and non-mesogenic compounds in the total polymerizable mixture. That is, it does not contain other non-polymerizable components and additives such as initiators, surfactants, stabilizers and solvents.

  Preferably the polymerizable component of the LC material is 12 to 100 mol%, very preferably 40 to 100 mol%, in particular 60 to 100 mol%, most preferably 80 to 100 mol% of a photoisomerizable compound, Preferably it comprises a cinnamic acid compound RM, most preferably one selected from formulas III, IV and V.

  In another preferred embodiment, the polymerizable component of the LC material is 20-99 mol%, preferably 30-80 mol%, most preferably 40-65 mol% of a photoisomerizable compound, preferably cinnamic acid. Compounds RM, most preferably include those selected from Formulas III, IV and V.

  In another preferred embodiment, the polymerizable component of the LC material comprises 100 mol% photoisomerizable RM, preferably a cinnamic acid compound RM, most preferably selected from formulas III, IV and V .

  The tilt angle θ of the LC molecule (director) in the polymerized film can be determined from retardation measurement. Those measurements show that when the LC material is exposed to light irradiation used for photoisomerization for a relatively long time or with a relatively high light intensity, its initial planar alignment changes to tilt or splay alignment. . In particular, these spray type films do not exhibit the reverse tilt defects normally associated with spray type LC films formed on low pretilt substrates. Therefore, the method according to the present invention provides an excellent way to obtain a retardation film having a uniform splay orientation.

  Thus, according to another preferred embodiment of the present invention, the orientation of the LC material in the film is controlled by changing the irradiation time and / or intensity of the light irradiation used to cause isomerization in the LC material. This preferred embodiment has a splay structure by changing the orientation in a polymerizable LC material layer having a planar orientation, as described in steps a) to e) above, and the number of reverse tilt defects. The present invention also relates to a method for producing a polymerized LC film with little or no tilt defect.

  This embodiment also relates to a spray-oriented film obtained by said method, preferably having a thickness of less than 3 μm, very preferably 0.5 to 2.5 μm.

  The optimum irradiation time and irradiation intensity depend on the type of LC material used, in particular the type and amount of photoisomerizable compound in the LC material.

  As described above, for example, the retardation reduction of a polymerizable LC material containing a cinnamic acid compound RM is large in a mixture having a high concentration of the cinnamic acid compound RM. On the other hand, when the polymerizable LC material is irradiated with a high dose of UV light, a spray alignment film is formed.

  Thus, another method for controlling retardation and orientation changes in the LC layer is obtained by photoisomerization as a function of the concentration of the photoisomerizable compound while still maintaining the planar orientation in the LC layer. The maximum reduction in retardation that can be achieved.

  In the polymerizable LC mixture used in the process for producing a film according to the invention where no change in orientation from planar to spray is required, the polymerizable component is preferably 40-90 mol%, very preferably 50-70%. Photoisomerizable cinnamic acid compounds of the formula III, IV and / or V.

  In the polymerizable LC mixture used in the process for producing a film according to the present invention where an orientation change from planar to spray is desired, the polymerizable component is preferably 100% photoisomerizable of Formula III, IV and / or V Contains cinnamic acid compounds.

  Again, the polymerizable LC mixture used in the process for producing a film according to the present invention in which an orientation change from planar to spray is desirable is preferably a photoisomerizable cinnamic acid compound of formula III or IV wherein R is an alkyl group Not included.

  By using a photomask method, a patterned film having regions with different orientations and / or different retardations can be produced using the method according to the second preferred embodiment.

  Particularly preferred are films having at least one region with a planar orientation and at least one region with a splayed orientation.

  More preferred is a film having at least one region with zero retardation.

Using the above method, multiple layers comprising a plurality of polymerized LC films, each having a different orientation of the LC material, can also be produced by the following method. That is,
A) providing a first layer of polymerizable LC material comprising at least one photoisomerizable compound on a substrate;
B) arranging the first layer of LC material in a planar orientation and fixing the orientation by polymerizing the material;
C) a method comprising providing a second layer of LC material by the steps of A) and B) using the first layer as a substrate,
The LC material in at least one of the first and second layers or selected regions of those layers is subjected to light, preferably UV light, that causes isomerization of the isomerizable compound prior to polymerization. It is a method of exposing.

  Particularly preferred are multilayer structures having 2 or more, very preferably 2, 3 or 4 polymerized LC films.

  For example, a first polymerized planar LC film is produced according to the method described above. The film is used as a substrate and then coated with a second layer of the same LC mixture. Next, the second layer is also arranged in the planar direction. Thus, a laminated structure including two planar polymerized LC films can be manufactured. Prior to polymerization, when the second layer is irradiated, for example with a sufficient dose of UV light, it exhibits a spray structure. Therefore, a laminated structure including a planar and spray type polymerized LC film can be produced.

  Prior to polymerization, when the LC mixture of the first layer is irradiated, for example with a sufficient dose of UV light, the first layer produces a splayed LC film. Coating this spray-type film with a second layer of the same LC mixture, irradiation, and polymerization, the second layer forms a homeotropically arranged layer, so that the lamination of the spray and homeotropic film A structure can be manufactured.

  Particularly preferred are multilayer bodies having at least one layer with planar orientation and at least one layer with splay orientation.

  Further preferred are multilayer bodies having at least one layer with splay orientation and at least one region with homeotropic orientation.

  By combining the above methods, a film having a pattern of regions having different orientations and regions having different retardations can also be produced.

  By combining the above methods, it is also possible to produce a multilayer body having two or more layers, in which at least one layer has a different orientation and / or a different retardation pattern. is there.

  To produce a polymer film, preferably a substrate is coated with a polymerizable LC mixture, which is preferably aligned in a planar orientation and isomerized to form the desired retardation or orientation pattern, eg, thermal or chemical Polymerize in situ by exposure to radiation to fix the LC molecule orientation. Alignment and curing take place in the LC phase of the mixture.

  In displays and optical elements according to the present invention, a polymerizable and isomerizable LC material is preferably applied on a color filter functioning as a substrate or on an alignment layer provided on the color filter.

  The polymerizable LC material can be applied onto the substrate by conventional coating techniques such as spin coating or blade coating. It is suitable for professionals such as screen printing, offset printing, open reel printing, letterpress printing, gravure printing, rotary gravure printing, flexographic printing, intaglio printing, pad printing, heat seal printing, inkjet printing or printing by stamp or printing plate. Can also be applied to the substrate by known printing techniques.

  It is also possible to dissolve the polymerizable mesogenic material in a suitable solvent. The solution is then coated or printed on the substrate, for example by spin coating or printing or other known methods, and the solvent is distilled off before polymerization. In most cases, it is preferred to heat the mixture to facilitate evaporation of the solvent. As the solvent, for example, a standard organic solvent can be used. Solvents include, for example, ketones such as acetone, methyl ethyl ketone, methyl propyl ketone or cyclohexanone; acetates such as methyl-, ethyl- or butylacetic acid or methyl acetoacetate; alcohols such as methanol, ethanol or isopropyl alcohol; toluene or xylene Aromatic solvents such as methylene chloride or halogenated hydrocarbons such as trichloromethane; glycols such as PGMEA (propyl glycol monomethyl ether acetate), γ-butyrolactone or esters thereof. A mixture of two, three or more of the above solvents can also be used.

The initial alignment (eg, planar alignment) of the polymerizable LC material can be achieved by providing an alignment layer by, for example, rubbing a substrate coated with the material, shearing the material during or after coating, and providing an alignment layer. Alternatively, it can be obtained by applying an electric field to the coating material or by adding a surface active compound to the LC material. For a review of alignment methods, see Sage's book (I. Sage, “Thermotropic Liquid Crystals”, edited by GW Gray, John Wiley &
Sons, 1987, pages 75-77) and T. Uchida and H. Seki, ″ Liquid Crystals
-Applications and Uses Vol. 3 ″, edited by B. Bahadur, World Scientific Publishing, Singapore 1992,
pages 1-63). A review of alignment materials and methods can be found in Cognard's report (J. Cognard, Mol. Cryst. Liq. Cryst. 78, Supplement 1
(1981), pages 1-77).

In a preferred embodiment, the polymerizable LC material includes an additive that induces or promotes planar alignment of LC molecules on the substrate. Preferably the additive comprises one or more surfactants. Suitable surfactants are described, for example, by Cognard (J. Cognard, Mol. Cryst. Liq. Cryst. 78 , Supplement 1, 1-77.
(1981)). Particularly preferred are nonionic surfactants, such as the commercially available fluorocarbon surfactant Fluorad FC-171 (registered trademark; from 3M Co.) or Zonyl FSN (registered trademark; from DuPont). And other surfactants described in GB022718.8.

  In another preferred embodiment, an alignment layer is provided on the substrate and a polymerizable LC material that forms a retardation film is applied over the alignment layer. The alignment layer induces the desired initial orientation, such as planar orientation, in the LC material. The LC material is then isomerized and cured according to the method described above. Suitable alignment layers are known in the art, such as alignment layers produced by rubbing polyimide or photoalignment as described in US Pat. No. 5,602,661, US Pat. No. 5,389,698 or US Pat. No. 6,717,644.

  Polymerization can be effected, for example, by exposure to heat or actinic radiation. Actinic radiation means irradiation with light such as UV light, IR light or visible light, irradiation with X-rays or γ-rays, or irradiation with high energy particles such as ions or electrons. Preferably the polymerization is carried out by UV irradiation at a non-absorbing wavelength. As the actinic radiation source, for example, a single UV lamp or a UV lamp set can be used. When high lamp power is used, the curing time can be shortened. Another possible source of actinic radiation is a laser such as a UV laser, an IR laser or a visible laser.

  The polymerization is preferably carried out in the presence of an initiator that absorbs at the wavelength of actinic radiation. For example, when polymerization is performed by UV light, a photoinitiator that decomposes under UV irradiation to generate free radicals or ions that start the polymerization reaction can be used. When curing a polymerizable material having an acrylate group or a methacrylic ester group, preferably a radical photoinitiator is used, and when curing a polymerizable material having a vinyl group, an epoxide group and an oxetane group, preferably a cation Sex photoinitiator is used. It is also possible to use a polymerization initiator that decomposes when heated to produce free radicals or ions that initiate polymerization. As a photoinitiator for radical polymerization, for example, commercially available Irgacure 651, Irgacure 184, Darocur 1173 or Darocur 4205 (both from Ciba Geigy AG) can be used, while cationic photopolymerization can be used. In some cases, commercially available UVI 6974 (Union Carbide) can be used.

  The curing time depends in particular on the reactivity of the polymerizable material, the thickness of the coating layer, the type of polymerization initiator and the power of the UV lamp. The curing time according to the invention is preferably within 10 minutes, particularly preferably within 5 minutes and very particularly preferably less than 2 minutes. For mass production, a short curing time of less than 3 minutes, very preferably less than 1 minute, in particular less than 30 seconds is preferred.

  The mixture may be one or more dyes, especially UV dyes such as 4,4′-azoxyanisole or commercially available Tinuvin (Ciba AG ( From Ciba AG, Basel, Switzerland)).

  In another preferred embodiment, the mixture of polymerizable materials comprises 70% or less, preferably 1-50%, of one or more non-mesogenic compounds having one polymerizable functional group. Typical examples are alkyl acrylates or alkyl methacrylates.

  In order to increase the cross-linking of the polymer, 20 or more of one or more non-mesogenic compounds having two or more polymerizable functional groups in the polymerizable LC material may be used instead of or in addition to the bifunctional or polyfunctional polymerizable mesogenic compound. It is also possible to increase the cross-linking of the polymer in addition to less than%. Representative examples of bifunctional non-mesogenic monomers include alkyl diacrylates or alkyl dimethacrylates having an alkyl group of 1 to 20 C atoms. Typical examples of multifunctional non-mesogenic monomers are trimethylolpropane trimethacrylate or pentaerythritol tetraacrylate.

  It is also possible to add one or more chain transfer agents to the polymerizable material to change the physical properties of the polymer film of the present invention. Particularly preferred are thiol compounds such as monofunctional thiol compounds such as dodecanethiol or polyfunctional thiol compounds such as trimethylolpropane tri (3-mercaptopropionate), very particularly preferably eg WO96 / 12209, WO96 / 25470 or US6420001 as mesogenic or liquid crystalline thiol compounds. With the addition of a chain transfer agent it is possible to control the length of the free polymer chain and the length of the polymer chain between two crosslinks in the polymer film of the present invention. Increasing the amount of chain transfer agent decreases the polymer chain length in the resulting polymer film.

  The polymerizable LC material can further comprise one or more monomers and / or one or more dispersion aids that can form a polymer binder or polymer binder. Suitable binders and dispersion aids are disclosed, for example, in WO 96/02597. Particularly preferred, however, are LC materials that do not contain binders or dispersion aids.

  Polymerizable LC materials can further include, for example, catalysts, sensitizers, stabilizers, inhibitors, chain transfer agents, co-reactive monomers, surface active compounds, lubricants, wetting agents, dispersants, hydrophobizing agents, adhesives, flow improvement. One or more other suitable ingredients such as agents, antifoams, defoamers, diluents, reactive diluents, adjuvants, colorants, dyes or pigments may be included.

  It is also possible to manufacture a patterning film by thermal patterning instead of the patterning layer described above. For example, by polymerizing different regions at different temperatures using layers of polymerizable LC material (which need not contain isomerizable compounds), different regions have different birefringence and thus different retardation. .

  The following examples are provided to illustrate the present invention and are not intended to limit the present invention. In these examples, unless otherwise noted, all temperatures are in degrees Celsius and all percentages are given as weight percentages. Simulations of optical performance such as brightness, chromaticity and contrast plots are performed using a Berreman 4 × 4 matrix calculation.

<Example 1-Production of patterning HWF>
The following polymerizable LC mixture is prepared:

Compound (1): 14.4%;
Compound (2): 18.0%;
Compound (3): 17.0%;
Compound (4): 17.0%;
Compound (5): 32.0%;
Irgacure 651: 1.0%;
Fluorado FC171: 0.6%

  Compounds (1) to (5) have been reported in the prior art. Irgacure 651 is a commercially available photoinitiator (from Ciba AG (Basel, Switzerland)). Fluorad FC171 is a commercially available nonionic fluorocarbon surfactant (from 3M).

Dissolve the mixture to prepare a 50 wt% xylene solution. This solution is filtered (0.2 μm PTFE membrane) and spin coated onto a glass / rubbed polyimide slide (low pretilt polyimide JSR AL 1054 from Japan Synthetic Rubber). The coating film is exposed with 20 mW cm ⁻² of 365 nm light in air using a tone (0: 50: 100% transmission) mask.

Next, the obtained film is photopolymerized using a 20 mWcm ⁻² UV-A irradiation under an N ₂ atmosphere for 60 seconds to obtain a patterning film having a pattern of regions having different retardations.

<Example 2-TIPS-Display>
The optical performance of the TIPS-LCD having the optical layer stack shown in FIG. 2 is calculated. The parameters of the constituent elements are as follows.

Front polarizing plate direction: + 45 °
Rear polarizing plate direction: -45 °,
LC director orientation (transmission subpixel, dark state): + 135 °,
LC director orientation (transmission subpixel, bright state): + 90/180 ° (dual domain),
LC retardation (transmission subpixel): 275 nm,
LC director orientation (reflective subpixel, dark state): 135 °,
LC director orientation (reflective subpixel, bright state): 90 or 180 °,
LC retardation (reflection subpixel): 138 nm,
In-cell HWF optical axis (reflection subpixel): + 22.5 °,
In-cell HWF retardation (reflection subpixel): 275 nm.

  The in-patterning-cell HWF can be manufactured by the method described in Example 1, for example.

  The angular luminance of the transmissive and reflective subpixels is shown in FIG. The on-axis brightness is 45.4% (transmission) and 47.1% (reflection).

  A bright state chromaticity plot of the transmissive and reflective sub-pixels is shown in FIG. The chromaticity is 1.1% (transmission) and 0.9% (reflection).

  The on-axis contrast of the transmissive and reflective subpixels is shown in FIG. The average angles of> 10: 1 contrast are 79.4 ° (transmission) and 49.0 ° (reflection). The average angles of> 100: 1 contrast are 52.2 ° (transmission) and 21.7 ° (reflection).

<Example 3-TIPS-Display>
The optical performance of the TIPS-LCD having the optical layer stack shown in FIG. 3 is calculated.

  The parameters of the constituent elements are as follows.

Front polarizing plate direction: + 45 °
Rear polarizing plate direction: -45 °,
LC director orientation (transmission subpixel, dark state): + 45 °,
LC director orientation (transmission subpixel, bright state): + 0/90 ° (dual domain),
LC retardation (transmission subpixel): 275 nm,
LC director orientation (reflective subpixel, dark state): 45 °,
LC director orientation (reflective subpixel, bright state): 0 or 90 °,
LC retardation (reflection subpixel): 138 nm,
In-cell HWF optical axis (reflection subpixel): + 112.5 °,
In-cell HWF retardation (reflection subpixel): 275 nm,
+ C plate retardation: 90 nm,
+ A plate optical axis: + 45 °,
+ A plate retardation: 138 nm.

  The in-patterning-cell HWF can be manufactured by the method described in Example 1, for example.

  The angular luminance of the transmissive and reflective subpixels is shown in FIG. The on-axis brightness is 46.3% (transmission) and 47.3% (reflection).

  A light state chromaticity plot of the transmissive and reflective sub-pixels is shown in FIG. The chromaticity is 1.1% (transmission) and 1.5% (reflection).

  The on-axis contrast of the transmissive and reflective subpixels is shown in FIG. The average angles of> 10: 1 contrast are> 80 ° (transmission) and 41.8 ° (reflection). The average angles of> 100: 1 contrast are> 80 ° (transmission) and 17.7 ° (reflection).

  The simulation results clearly show that a transflective IPS having good optical performance can be designed by introducing a patterning retardation plate. Thus, a standard viewing angle performance equivalent to that required by the television industry can be combined with reflective LCD technology to create a display that can be viewed in all light conditions.

It is a figure which shows TIPS-LCD by this invention. FIG. 4 is a diagram illustrating an arrangement of optical layers in a TIPS-LCD according to a preferred embodiment of the present invention. FIG. 4 is a diagram illustrating an arrangement of optical layers in a TIPS-LCD according to a preferred embodiment of the present invention. It is a figure which shows the calculated value of the angular luminance in the transmission mode of TIPS-LCD by Example 2. FIG. It is a figure which shows the calculated value of the angular luminance in the reflection mode of TIPS-LCD by Example 2. FIG. It is a figure which shows the calculated value of the light state chromaticity in the transmission mode of TIPS-LCD by Example 2. FIG. It is a figure which shows the calculated value of the light state chromaticity in the reflection mode of TIPS-LCD by Example 2. FIG. It is a figure which shows the calculated value of the angular contrast in the transmission mode of TIPS-LCD by Example 2. FIG. It is a figure which shows the calculated value of the angular contrast in the reflection mode of TIPS-LCD by Example 2. FIG. It is a figure which shows the calculated value of the angular luminance in the transmission mode of TIPS-LCD by Example 3. FIG. It is a figure which shows the calculated value of the angular luminance in the reflection mode of TIPS-LCD by Example 3. FIG. It is a figure which shows the calculated value of the light state chromaticity in the transmission mode of TIPS-LCD by Example 3. FIG. It is a figure which shows the calculated value of the light state chromaticity in the reflection mode of TIPS-LCD by Example 3. FIG. It is a figure which shows the calculated value of the angular contrast in the transmission mode of TIPS-LCD by Example 3. FIG. It is a figure which shows the calculated value of the angular contrast in the reflection mode of TIPS-LCD by Example 3. FIG.

Explanation of symbols

10 pixels 10a reflective subpixels 10b transmissive subpixels 11a, b plane parallel substrate 12 liquid crystal (LC) medium 12a divided LC layer (reflective subpixel part)
12b LC layer divided (transmission subpixel part)
13a, b Polarizing plate 14a Reflective electrode 14b Transparent electrode 14a1 ITO layer 14a2 Reflective layer 15 Color filter 16 Retardation film 16a Retardation region 16b Non-retardation region 17 Non-linear electric element 18 Step 19 Back surface + C plate Retardation plate 20 Back surface + A plate Retardation plate

Claims (8)

In a transflective liquid crystal display having one or more pixels divided into reflective and transmissive subpixels,
(A) an LC cell in in-plane switching (IPS) mode having an electrode layer and an LC layer that is switchable between different orientations when an electric field having a main component parallel to the LC layer surface is applied;
(B) front and back polarizing plates sandwiching the LC cell and having front and back polarization directions;
(C) It is arranged between the front polarizing plate and the LC layer, and has a pattern of a region having a predetermined on-axis retardation and a region having substantially no retardation, and the retardation region is substantially A transflective liquid crystal display comprising at least one retardation film disposed so as to cover only a reflective subpixel. (A) the following elements: (a-1) first and second substrate surfaces that are parallel to each other and at least one of which is transparent to incident light;
(A-2) an array of non-linear electrical elements provided on one of the substrates that can be used to individually switch individual pixels of the LC cell, such as transistors;
(A-3) A color filter array provided on one of the substrates and having a pattern of various pixels that transmit one of primary colors red, green, and blue (R, G, B), A color filter array, in which the color filter may be covered with a planarizing layer,
(A-4) an electrode layer provided on the inner side of the first or second substrate designed to be able to apply an electric field so that the main component is parallel to the plane of the LC layer;
(A-5) As an optional element, an alignment layer provided on the electrode,
(A-6) a liquid crystal (LC) cell having an LC medium switchable between at least two different orientations by applying an electric field;
(B) a first linearly polarizing plate provided on the first side of the LC cell;
The liquid crystal display according to claim 1, further comprising: (c) a second linearly polarizing plate provided on a second side of the LC cell; and (c) at least one patterning retardation film as defined in claim 1. .   The liquid crystal display according to claim 1, wherein the LC layer in the reflective subpixel has a ¼ wavelength retardation.   The liquid crystal display according to claim 1, wherein the patterning retardation film is a half-wave retardation film (HWF).   5. The liquid crystal display according to claim 1, wherein the LC layer in the patterning retardation film and the reflective subpixel are integrated to form an achromatic quarter-wave retardation plate (AQWF). .   The liquid crystal display according to claim 1, further comprising at least one + A plate and / or at least one + C plate retardation plate.   A color filter having a pattern of R-, G-, and B-pixels; and the patterning retardation film further optimizes the efficiency of converting linearly polarized light into circularly polarized light for each of the R, G, and B colors. Shows the pattern of R-, G- and B-pixels with different retardations adjusted so that the R-, G- and B-pixels of the retardation film correspond to the corresponding R-, The liquid crystal display according to claim 1, which is disposed so as to cover each of the G- and B-pixels.   A patterned HWF used in a TIPS-LCD with transmissive and reflective sub-pixels and having a pattern of regions with half-wavelength (λ / 2) retardation and regions with substantially no retardation.