KR100356836B1 - Homogeneous alignment mode lcd - Google Patents

Abstract

The present invention discloses a horizontal alignment mode liquid crystal display device having fast response characteristics while improving viewing angle characteristics. The present invention discloses an upper and lower substrates facing each other at a predetermined distance and having a unit pixel defined therein; A liquid crystal layer interposed between the upper and lower substrates and including several liquid crystal molecules; A first horizontal alignment layer interposed between the lower substrate resultant surface and the liquid crystal layer and having a rubbing axis in a predetermined direction; A second horizontal alignment layer interposed between the upper substrate resultant surface and the liquid crystal layer, the second horizontal alignment layer having a rubbing axis parallel to a rubbing axis of the first horizontal alignment layer; A pixel electrode formed between the lower substrate and the first horizontal alignment layer; A counter electrode formed between the upper substrate and the second horizontal alignment layer and driving liquid crystal molecules together with the pixel electrode; A polarizer disposed on an outer surface of the upper substrate and having a predetermined polarization axis; And a decomposer disposed on an outer surface of the lower substrate and having an absorption axis orthogonal to the polarization axis of the polarizer, wherein the pixel electrode includes at least one slit perpendicular to the rubbing axis of the first horizontal alignment layer, and The counter electrode may be formed in a plate shape.

Description

Horizontal alignment mode liquid crystal display {HOMOGENEOUS ALIGNMENT MODE LCD}

The present invention relates to a liquid crystal display device, and more particularly, to a horizontal alignment mode liquid crystal display device having improved viewing angle characteristics and response characteristics.

In general, a thin film transistor liquid crystal display (TFT-LCD) may be miniaturized in volume and low power consumption in comparison with a conventional cathode ray tube (CRT). However, such a thin film transistor liquid crystal display device has a front viewing angle comparable to that of a CRT, but is not excellent in an oblique direction. The change in the viewing angle in this way depends on the refractive index anisotropy of the liquid crystal molecules constituting the liquid crystal layer, as is known.

In order to solve this problem, a vertical alignment (VA) mode and an in plan field (IPS) mode liquid crystal display have been conventionally proposed.

First, the configuration of the VA mode liquid crystal display device is as follows.

Liquid crystal layers having negative dielectric anisotropy are sandwiched between the upper and lower substrates each having electrodes, and vertical alignment films are interposed on inner surfaces of the upper and lower substrates, respectively. This VA mode has the advantage of excellent response speed characteristics.

On the other hand, the configuration of the IPS mode liquid crystal display device is as follows.

The upper and lower substrates face each other at a predetermined distance. The liquid crystal layer is interposed between the upper and lower substrates, and the pixel electrode and the counter electrode are disposed at a predetermined interval on the lower substrate. At this time, the gap between the pixel electrode and the counter electrode is larger than the gap between the upper and lower substrates. Horizontal alignment layers are interposed on the inner surface of the lower substrate and the upper substrate. Then, the electric field formed between the pixel electrode and the counter electrode is formed in parallel with the lower substrate surface, so that the viewing angle characteristic is improved.

However, the above-described IPS mode has excellent viewing angle characteristics but very slow response speed, which makes it difficult to use for realizing moving images. In addition, in the IPS mode, the liquid crystal molecules are uniformly arranged when the electric field is applied or after the electric field is applied, causing a color shift phenomenon in which a predetermined color is expressed according to the viewing direction.

On the other hand, while the VA mode has excellent response speed characteristics, the viewing angle is very narrow.

Accordingly, an object of the present invention is to solve the above-mentioned problems, and to provide a horizontal alignment mode liquid crystal display having fast response characteristics while improving viewing angle characteristics.

1 is a perspective view of a horizontal alignment mode liquid crystal display device according to the present invention;

2 is a view showing liquid crystal molecules constituting the liquid crystal layer of the present invention.

3 is a view showing a phase compensation plate of the present invention.

4 is a perspective view schematically illustrating a pixel electrode and a common electrode of a horizontal alignment mode liquid crystal display according to the present invention.

5A and 5B are cross-sectional views for explaining the operation of the horizontal alignment mode liquid crystal display device according to the present invention;

6 is a graph showing an iso contrast ratio of a horizontal alignment mode liquid crystal display device according to the present invention;

7 is a graph showing transmittance according to voltage in a horizontal alignment mode liquid crystal display according to the present invention.

(Explanation of symbols for the main parts of the drawing)

10-lower substrate 13-pixel electrode

15-first horizontal alignment layer 17-polarizer

20-upper substrate 23-counter electrode

25-second horizontal alignment layer 27-decomposer

28-phase compensation plate 28a-liquid crystal molecules constituting the phase compensation plate

30-liquid crystal layer 30a-liquid crystal molecules

In order to achieve the above object of the present invention, the present invention, the upper and lower substrates opposed to each other at a predetermined distance, the unit pixel is limited; A liquid crystal layer interposed between the upper and lower substrates and including several liquid crystal molecules; A first horizontal alignment layer interposed between the lower substrate resultant surface and the liquid crystal layer and having a rubbing axis in a predetermined direction; A second horizontal alignment layer interposed between the upper substrate resultant surface and the liquid crystal layer, the second horizontal alignment layer having a rubbing axis parallel to a rubbing axis of the first horizontal alignment layer; A pixel electrode formed between the lower substrate and the first horizontal alignment layer; A counter electrode formed between the upper substrate and the second horizontal alignment layer and driving liquid crystal molecules together with the pixel electrode; A polarizer disposed on an outer surface of the upper substrate and having a predetermined polarization axis; And a decomposer disposed on an outer surface of the lower substrate and having an absorption axis orthogonal to the polarization axis of the polarizer, wherein the pixel electrode includes at least one slit perpendicular to the rubbing axis of the first horizontal alignment layer, and The counter electrode may be formed in a plate shape.

In addition, the present invention, the upper and lower substrates opposed to each other at a predetermined distance, the unit pixel is limited; A liquid crystal layer interposed between the upper and lower substrates and including several liquid crystal molecules; A first horizontal alignment layer interposed between the lower substrate resultant surface and the liquid crystal layer and having a rubbing axis in a predetermined direction; A second horizontal alignment layer interposed between the upper substrate resultant surface and the liquid crystal layer, the second horizontal alignment layer having a rubbing axis parallel to a rubbing axis of the first horizontal alignment layer; A pixel electrode formed between the lower substrate and the first horizontal alignment layer; A counter electrode formed between the upper substrate and the second horizontal alignment layer and driving liquid crystal molecules together with the pixel electrode; A polarizer disposed on an outer surface of the upper substrate and having a predetermined polarization axis; And a decomposer disposed on an outer surface of the lower substrate and having an absorption axis orthogonal to a polarization axis of the polarizer, wherein the counter electrode includes at least one slit perpendicular to the rubbing axis of the second horizontal alignment layer, The pixel electrode may be formed in a plate shape.

In addition, the present invention, the upper and lower substrates opposed to each other at a predetermined distance, the unit pixel is limited; A liquid crystal layer interposed between the upper and lower substrates and including several liquid crystal molecules; A first horizontal alignment layer interposed between the lower substrate resultant surface and the liquid crystal layer and having a rubbing axis in at least two directions that are symmetrical to each other; A second horizontal alignment layer interposed between the upper substrate resultant surface and the liquid crystal layer, the second horizontal alignment layer having rubbing axes parallel to each of the rubbing axes of the first horizontal alignment layer; A pixel electrode formed between the lower substrate and the first horizontal alignment layer; A counter electrode formed between the upper substrate and the second horizontal alignment layer and driving liquid crystal molecules together with the pixel electrode; A polarizer disposed on an outer surface of the upper substrate and having a predetermined polarization axis; And a decomposer disposed on an outer surface of the lower substrate and having an absorption axis orthogonal to a polarization axis of the polarizer, wherein the pixel electrode has a plurality of slits extending to be perpendicular to each of the rubbing axes of the first horizontal alignment layer. The counter electrode may be formed in a plate shape.

In addition, the present invention, the upper and lower substrates opposed to each other at a predetermined distance, the unit pixel is limited; A liquid crystal layer interposed between the upper and lower substrates and including several liquid crystal molecules; A first horizontal alignment layer interposed between the lower substrate resultant surface and the liquid crystal layer and having a rubbing axis in at least two directions that are symmetrical to each other; A second horizontal alignment layer interposed between the upper substrate resultant surface and the liquid crystal layer, the second horizontal alignment layer having rubbing axes parallel to each of the rubbing axes of the first horizontal alignment layer; A pixel electrode formed between the lower substrate and the first horizontal alignment layer; A counter electrode formed between the upper substrate and the second horizontal alignment layer and driving liquid crystal molecules together with the pixel electrode; A polarizer disposed on an outer surface of the upper substrate and having a predetermined polarization axis; And a decomposer disposed on an outer surface of the lower substrate and having an absorption axis orthogonal to the polarization axis of the polarizer, wherein the counter electrode has a plurality of slits extending to be perpendicular to each of the rubbing axes of the second horizontal alignment layer. The pixel electrode may be formed in a plate shape.

Here, a phase compensation plate is further interposed between any one of the upper substrate and the decomposer, between the lower substrate and the polarizer, between the upper substrate and the liquid crystal layer, or between the lower substrate and the liquid crystal layer. At this time, the phase compensating plate is a film cured in a state where the liquid crystal molecules of the disc type are placed upright (nx = ny> nz). In addition, the phase retardation value of the phase compensation plate is preferably the same as the phase retardation value of the liquid crystal layer and the phase is opposite.

The polarization axis of the polarizer is preferably a rubbing axis of the first horizontal alignment layer of about ± 40 to 50 °.

According to the present invention, slits perpendicular to the rubbing axis are formed in the pixel electrode or the counter electrode. Accordingly, the electric field between the pixel electrode and the counter electrode is partially tilted so that the liquid crystal molecules are arranged in a band form. Accordingly, since the liquid crystal molecules are symmetrically arranged to obtain a symmetrical viewing angle, and the liquid crystal molecules are arranged in a band form to operate stably, the liquid crystal molecules are operated at a high response speed without reverse flow when the voltage is turned on or off.

In addition, the phase compensation plate cured in the form of a disk-type liquid crystal molecules are selectively placed on the outside or inside of the substrate to obtain a high contrast ratio of the liquid crystal display device and to secure a perfect viewing angle in any aspect. have.

(Example)

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a perspective view of a horizontal alignment mode liquid crystal display device according to the present invention, FIG. 2 is a view showing liquid crystal molecules constituting the liquid crystal layer of the present invention, and FIG. 3 is a view showing a phase compensating plate of the present invention. to be. 4 is a perspective view schematically illustrating a pixel electrode and a common electrode of the horizontal alignment mode liquid crystal display according to the present invention, and FIGS. 5A and 5B are views for explaining the operation of the horizontal alignment mode liquid crystal display according to the present invention. It is a cross section. 6 is a graph illustrating an isocontrast ratio of the horizontal alignment mode liquid crystal display according to the present invention, and FIG. 7 is a graph showing the transmittance according to voltage in the horizontal alignment mode liquid crystal display according to the present invention.

First, referring to FIG. 1, at least one transparent lower substrate 10 and upper substrate 20 are opposed to each other at a predetermined interval. At this time, the distance d between the upper and lower substrates is called a cell gap. In addition, the upper and lower substrates 10 and 20 have limited unit pixels. The upper and lower substrates 10 and 20 include a liquid crystal layer 30 including a plurality of liquid crystal molecules 30a. As the liquid crystal molecules, a material having a positive or negative dielectric anisotropy (Δε) may be selectively used. The liquid crystal molecules may have a rod having a larger z-axis (nz) than the x-axis (nx) and the y-axis (ny), as shown in FIG. It is a rod type and has refractive index anisotropy. Further, the phase retardation value (the product of the cell gap and the refractive index anisotropy of the liquid crystal molecules: dΔn) of the liquid crystal layer is such that the maximum transmittance is obtained, i.e., a value of λ / 2, by the following transmittance formula of Equation 1 below.

T ≒ T ₀ sin2 (2χ) · sin2 (π · Δnd / λ) .............. (Equation 1)

T: transmittance

T ₀ : Transmittance for reference light

χ: angle formed between the optical axis of the liquid crystal molecules and the polarization axis of the polarizer

Δn: refractive index anisotropy

d: distance or gap between the upper and lower substrates (thickness of the liquid crystal layer)

λ: incident light wavelength

A first horizontal alignment layer 15 having a pretilt angle of 3 ° or less is interposed between the lower substrate 10 surface and the liquid crystal layer 30. A second horizontal alignment layer 25 is interposed between the upper substrate 20 surface and the liquid crystal layer 30. The first and second horizontal alignment layers 15 and 25 are rubbed in a predetermined direction, respectively, and the rubbing axis r1 of the first horizontal alignment layer 15 and the rubbing axis r2 of the second horizontal alignment layer 25 are mutually different. Anti-parallel. A polarizer 17 having a polarization axis (not shown) is disposed on an outer surface of the lower substrate 10, and a decomposer 27 having an absorption axis perpendicular or perpendicular to the polarization axis is attached to an outer surface of the upper substrate 20. . At this time, it is preferable that the rubbing axis r1 of the first horizontal alignment layer 15 is about ± 40 to 50 °, preferably ± 45 ° of the polarization axis of the polarizer 17. A phase compensating plate 28 is interposed between the upper substrate 20 and the decomposer 27. In this case, as shown in FIG. 3, the phase compensating plate 28 has a liquid crystal of a disk type, that is, the y axis ny is relatively larger than the x axis nx and the z axis nz. The phase compensating plate 28 is formed of a cured film of small liquid crystal molecules 28a. The phase compensating plate 28 has the same phase delay value dΔn of the liquid crystal layer as the phase retardation value d1Δn1, where d1 is a phase compensation. The thickness of the plate, Δn1, has the refractive index anisotropy of the phase compensation plate.

As illustrated in FIG. 4, a pixel electrode 13 is interposed between the lower substrate 10 and the first horizontal alignment layer 15, and a common electrode (eg, a gap between the upper substrate 20 and the second horizontal alignment layer 25). 23) is formed. In this case, at least one slit S perpendicular to the rubbing axis 15a of the first horizontal alignment layer 15 is formed in the pixel electrode 13, and the common electrode 23 is formed in a plate shape. In addition, on the contrary, the pixel electrode may be formed as a plate, and slits perpendicular to the rubbing axis of the second horizontal alignment layer 25 may be formed on the common electrode. Here, it is preferable that the ratio of the width of the slit S and the width of the pixel electrode or counter electrode 13, 23 between the slit S has a value between 0.01 and 0.9.

The horizontal alignment mode liquid crystal display device having such a configuration operates as follows.

Referring to FIG. 5A, before the electric field is formed between the pixel electrode 13 and the counter electrode 23, the liquid crystal molecules 30a in the liquid crystal layer 30 may be formed of the first and second horizontal alignment layers 15 and 25. Under influence the long axis is arranged parallel to the surface of the substrate 10. Accordingly, while the light passing through the polarizer 17 passes through the liquid crystal layer 30, the polarization state is changed to transmit the light, but the liquid crystal molecules 28a in the phase compensation plate are separated from the liquid crystal molecules of the liquid crystal layer 30. Since the refractive index anisotropy of 30a) is arranged to compensate, the refractive index anisotropy of the liquid crystal layer 30 is compensated. Therefore, a perfect dark can be realized in any aspect.

On the other hand, when a voltage difference is generated between the pixel electrode 13 and the counter electrode 23, an electric field E is formed between the pixel electrode 13 and the counter electrode 23. In this case, the electric field E is formed to be generally perpendicular to the surfaces of the substrates 10 and 20, but symmetrically tilted by the slit S in a portion where the slit S of the pixel electrode 13 is formed. do. Thus, for example, when the dielectric anisotropy is negative, the liquid crystal molecules 30a are arranged in the form of symmetrical bends by a symmetrical and partially tilted electric field, as shown in FIG. 5B. As such, as the liquid crystal molecules 30a are rearranged, light passing through the polarizer 17 passes through the liquid crystal layer 30 and the phase compensating plate 28, and the polarization state thereof is changed, thereby decomposing the decomposer 27. As it passes, the screen is white. In addition, when the liquid crystal molecules 30a are arranged in a bend state as described above, when the electric field is turned on or off, backflow of the liquid crystal molecules is alleviated, thereby increasing the response speed. In addition, a symmetrical viewing angle may be secured by a symmetrical arrangement of liquid crystal molecules. In addition, the arrangement of the phase compensating plate 28 compensates the refractive index anisotropy of the liquid crystal molecules, thereby obtaining even viewing angle characteristics on any side of the screen.

6 is a graph illustrating an isocontrast ratio of the horizontal alignment mode liquid crystal display according to the present invention. According to FIG. 6, in the horizontal alignment mode liquid crystal display of the present invention, the contrast ratio is 10 or more in most areas of the screen. , Has excellent image quality characteristics.

In addition, FIG. 7 is a graph showing transmittance according to voltage in the horizontal alignment mode liquid crystal display according to the present invention. According to FIG. 7, the transmittance of the liquid crystal display is generated when a voltage of 1V or more is applied to the pixel electrode. Has a driving voltage.

The present invention is not limited to the embodiment described above. In the present invention, the technique of unidirectional rubbing on the alignment film, forming a slit in the electrode so as to have a direction perpendicular to the rubbing axis, and forming a double domain in the liquid crystal layer has been described. However, the present invention is not limited thereto, and the same applies to rubbing in at least two directions symmetric to the alignment layer. That is, the technique of rubbing in at least two directions while being symmetrical with the alignment layer, and forming slits in the electrodes in a direction perpendicular to each of these rubbing axes to form multiple domains in the liquid crystal layer is also included. You will be able to reap.

In the present invention, the phase compensation plate is interposed between the upper substrate and the decomposer, but is not limited thereto, and may be selectively interposed between the lower substrate and the polarizer, between the upper substrate and the liquid crystal layer, or between the lower substrate and the liquid crystal layer.

As described in detail above, according to the present invention, slits perpendicular to the rubbing axis are formed in the pixel electrode or the counter electrode. Accordingly, the electric field between the pixel electrode and the counter electrode is partially tilted so that the liquid crystal molecules are arranged in a band form. Accordingly, since the liquid crystal molecules are symmetrically arranged to obtain a symmetrical viewing angle, and the liquid crystal molecules are arranged in a band form to operate stably, the liquid crystal molecules are operated at a high response speed without reverse flow when the voltage is turned on or off.

In addition, the phase compensation plate cured in the form of the disk-type liquid crystal molecules are placed on the outside or inside of the substrate selectively to obtain a high contrast ratio of the liquid crystal display device to ensure a perfect viewing angle from any side. have.

In addition, this invention can be implemented in various changes within the range which does not deviate from the summary.

Claims (20)

Upper and lower substrates that face each other at a predetermined distance and have a unit pixel defined therein; A liquid crystal layer interposed between the upper and lower substrates and including several liquid crystal molecules; A first horizontal alignment layer interposed between the lower substrate resultant surface and the liquid crystal layer and having a rubbing axis in a predetermined direction; A second horizontal alignment layer interposed between the upper substrate resultant surface and the liquid crystal layer, the second horizontal alignment layer having a rubbing axis parallel to a rubbing axis of the first horizontal alignment layer; A pixel electrode formed between the lower substrate and the first horizontal alignment layer; A counter electrode formed between the upper substrate and the second horizontal alignment layer and driving liquid crystal molecules together with the pixel electrode; A polarizer disposed on an outer surface of the upper substrate and having a predetermined polarization axis; And A decomposer disposed on an outer surface of the lower substrate and having an absorption axis orthogonal to a polarization axis of the polarizer, The pixel electrode includes at least one slit perpendicular to the rubbing axis of the first horizontal alignment layer, The counter electrode is in the form of a plate, A phase compensating plate is formed between the upper substrate and the decomposer, between the lower substrate and the polarizer, between the upper substrate and the liquid crystal layer, or between the lower substrate and the liquid crystal layer. And a phase retardation value of the phase compensating plate is the same as the phase retardation value of the liquid crystal layer, and the phases are opposite to each other. The horizontal alignment mode liquid crystal display of claim 1, wherein a polarization axis of the polarizer is in a range of ± 40 to 50 ° with a rubbing axis of the first horizontal alignment layer. Upper and lower substrates that face each other at a predetermined distance and have a unit pixel defined therein; A liquid crystal layer interposed between the upper and lower substrates and including several liquid crystal molecules; A first horizontal alignment layer interposed between the lower substrate resultant surface and the liquid crystal layer and having a rubbing axis in a predetermined direction; A second horizontal alignment layer interposed between the upper substrate resultant surface and the liquid crystal layer, the second horizontal alignment layer having a rubbing axis parallel to a rubbing axis of the first horizontal alignment layer; A pixel electrode formed between the lower substrate and the first horizontal alignment layer; A counter electrode formed between the upper substrate and the second horizontal alignment layer and driving liquid crystal molecules together with the pixel electrode; A polarizer disposed on an outer surface of the upper substrate and having a predetermined polarization axis; And A decomposer disposed on an outer surface of the lower substrate and having an absorption axis orthogonal to a polarization axis of the polarizer, The counter electrode has at least one or more slits perpendicular to the rubbing axis of the second horizontal alignment layer, The pixel electrode is in the form of a plate, A phase compensating plate is formed between the upper substrate and the decomposer, between the lower substrate and the polarizer, between the upper substrate and the liquid crystal layer, or between the lower substrate and the liquid crystal layer. And a phase retardation value of the phase compensating plate is the same as the phase retardation value of the liquid crystal layer, and the phases are opposite to each other. The horizontal alignment mode liquid crystal display of claim 3, wherein the polarization axis of the polarizer is in a range of ± 40 to 50 ° with a rubbing axis of the first horizontal alignment layer. Upper and lower substrates that face each other at a predetermined distance and have a unit pixel defined therein; A liquid crystal layer interposed between the upper and lower substrates and including several liquid crystal molecules; A first horizontal alignment layer interposed between the lower substrate resultant surface and the liquid crystal layer and having a rubbing axis in at least two directions that are symmetrical to each other; A second horizontal alignment layer interposed between the upper substrate resultant surface and the liquid crystal layer, the second horizontal alignment layer having rubbing axes parallel to each of the rubbing axes of the first horizontal alignment layer; A pixel electrode formed between the lower substrate and the first horizontal alignment layer; A counter electrode formed between the upper substrate and the second horizontal alignment layer and driving liquid crystal molecules together with the pixel electrode; A polarizer disposed on an outer surface of the upper substrate and having a predetermined polarization axis; And A decomposer disposed on an outer surface of the lower substrate and having an absorption axis orthogonal to a polarization axis of the polarizer, The pixel electrode includes a plurality of slits extending perpendicular to the rubbing axes of the first horizontal alignment layer, The counter electrode is in the form of a plate, A phase compensating plate is formed between the upper substrate and the decomposer, between the lower substrate and the polarizer, between the upper substrate and the liquid crystal layer, or between the lower substrate and the liquid crystal layer. And a phase retardation value of the phase compensating plate is the same as the phase retardation value of the liquid crystal layer, and the phases are opposite to each other. The horizontal alignment mode liquid crystal display of claim 5, wherein a polarization axis of the polarizer is in a range of ± 40 to 50 ° with a rubbing axis of the first horizontal alignment layer. Upper and lower substrates that face each other at a predetermined distance and have a unit pixel defined therein; A liquid crystal layer interposed between the upper and lower substrates and including several liquid crystal molecules; A first horizontal alignment layer interposed between the lower substrate resultant surface and the liquid crystal layer and having a rubbing axis in at least two directions that are symmetrical to each other; A second horizontal alignment layer interposed between the upper substrate resultant surface and the liquid crystal layer, the second horizontal alignment layer having rubbing axes parallel to each of the rubbing axes of the first horizontal alignment layer; A pixel electrode formed between the lower substrate and the first horizontal alignment layer; A counter electrode formed between the upper substrate and the second horizontal alignment layer and driving liquid crystal molecules together with the pixel electrode; A polarizer disposed on an outer surface of the upper substrate and having a predetermined polarization axis; And A decomposer disposed on an outer surface of the lower substrate and having an absorption axis orthogonal to a polarization axis of the polarizer, The counter electrode has a plurality of slits extending to be perpendicular to each of the rubbing axes of the second horizontal alignment layer, The pixel electrode is in the form of a plate, A phase compensating plate is formed between the upper substrate and the decomposer, between the lower substrate and the polarizer, between the upper substrate and the liquid crystal layer, or between the lower substrate and the liquid crystal layer. And a phase retardation value of the phase compensating plate is the same as the phase retardation value of the liquid crystal layer, and the phases are opposite to each other. 8. The horizontal alignment mode liquid crystal display of claim 7, wherein the polarization axis of the polarizer is in a range of ± 40 to 50 ° with the rubbing axis of the first horizontal alignment layer. delete delete delete delete delete delete delete delete delete delete delete delete