KR101493616B1 - Display cell manufactured by using a stamp and method of manufacturing a display using the same - Google Patents

Abstract

Disclosed is a method of manufacturing a display cell using a stamp method, for examples, an LCD cell and manufacturing a display by using the LCD cells. A method of manufacturing a display cell includes a step of allowing a stamp which includes a stamp substrate and an orientation material layer formed on the stamp substrate to touch a target on a substrate, and a step of forming an orientation layer on the target substrate by transferring part of the orientation material layer to the target substrate through a method of filling the stamp.

Description

TECHNICAL FIELD [0001] The present invention relates to a display cell manufactured using a stamp, and a method of manufacturing the display using the same. BACKGROUND OF THE INVENTION < RTI ID = 0.0 >

The present invention relates to a display cell and a method of manufacturing a display using the same, for example, a liquid crystal display device.

Conventional alignment methods for forming an alignment layer of a liquid crystal display device use mechanical rubbing, UV irradiation, ion beam alignment, and the like. However, these methods generate static electricity, dust, Lt; / RTI >

Korean Published Patent Application No. 2013-0031742 (Publication date: March 29, 2013)

The present invention provides a method of manufacturing a display cell, for example, an LCD cell using a stamping method, and manufacturing a display using the LCD cells.

According to an aspect of the present invention, there is provided a method of manufacturing a display cell, including: forming a stamp substrate on a target substrate; And forming an alignment layer on the target substrate by transferring a portion of the alignment material layer to the target substrate through a method of peeling the stamp.

A method of manufacturing a display cell fabrication stamp according to an embodiment of the present invention includes: coating an alignment material on a stamp substrate; And forming an alignment material layer on the stamp substrate by irradiating the coated alignment material with ultraviolet light to cure the alignment material.

A method of manufacturing a liquid crystal display device according to an embodiment of the present invention includes forming a first alignment layer on a first target substrate by transferring a first alignment material layer of a first stamp including a first alignment layer and a first alignment material layer to a first target substrate, The method comprising: fabricating a first LCD cell comprising: Forming a second LCD cell including a second alignment layer formed by transferring a second alignment material layer of a second stamp comprising a second stamping substrate and a second alignment material layer to a second target substrate; And arranging the liquid crystals between the LCD cells.

A stamp according to an embodiment of the present invention includes a stamp substrate; And an alignment material layer formed on the stamp substrate. Here, the alignment material layer corresponds to an alignment film of a display cell, and the alignment material layer is formed by coating an alignment material on the stamp substrate and irradiating linear polarized ultraviolet rays.

An LCD cell according to an embodiment of the present invention includes a target substrate; A polyimide (PI) alignment layer formed on the target substrate; And a reactive mesogen (RM) alignment layer formed on the PI alignment layer. Here, the RM alignment layer is formed by transferring a reactive mesogen layer cured by linear polarized ultraviolet rays onto the PI alignment layer.

Since the present invention forms an alignment film of a display cell in a stamping manner, the alignment film forming process is simple and the alignment film has anisotropic properties, so that excellent electrical characteristics can be realized.

In addition, since the reactive mesa alignment film covers the surface defects of the PI alignment film, the C-V characteristics can be improved.

1 is a view illustrating a liquid crystal display device according to an embodiment of the present invention.
2 is a view showing an alignment film forming process according to an embodiment of the present invention.
3 is a diagram showing a liquid crystal alignment state.
4 is a diagram showing an XPS spectrum of an RM stamp.
5 is a view showing the light transmittance characteristic.
6 is a diagram showing the temperature stability characteristic.

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

The present invention relates to a method of forming an alignment film for aligning liquid crystals in a certain direction, and for example, a reactive mesogen (RM) can be used as an alignment material. Specifically, the present invention uses a stamping method in which a reactive mesogen is transferred onto a target substrate, and is a non-rubbing method.

Conventionally, a mechanical rubbing method, a UV irradiation method, an ion beam alignment method, or the like has been used as an alignment method for orienting an alignment film. However, these methods generate static electricity, dust and the like and generate low fixed energy, image sticking, . On the other hand, the orientation method of the present invention solves this problem by using a stamping method.

Also, the master mold may be reused many times when a master mold is manufactured by transferring the reactive mesogen layer used in the present invention onto a polyimide (PI) alignment layer to form a RM alignment layer, Therefore, it is economically efficient.

In addition, the alignment method of the present invention is a simple process, and the number of cleaning processes can be reduced.

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

1 is a view illustrating a liquid crystal display device according to an embodiment of the present invention.

Referring to FIG. 1, the liquid crystal display device of the present embodiment includes a liquid crystal display panel 100 and a backlight unit 40 that provides light to the liquid crystal display panel 100.

The liquid crystal display panel 100 includes a first substrate 110, a second substrate 112, a first alignment film 114, a second alignment film 116, a liquid crystal layer 118, a first polarizer 120, And may include a polarizing plate 122.

The remaining components except for the orientation films 114 and 116 are widely known, and the description thereof will be omitted.

Each of the orientation films 114 and 116 may be made of, for example, a reactive mesogen, and may be composed of a single film or a plurality of films. In addition, each of the alignment films 114 and 116 may have an anisotropic property.

According to one embodiment, each of the alignment films 114 and 116 can be formed on the substrate 110 or 112 using a stamping method as described below, which is a thin film RM alignment film.

Hereinafter, the orientation method of the present invention will be described in detail.

2 is a view showing an alignment film forming process according to an embodiment of the present invention.

Referring to FIG. 2A, in the alignment method of the present embodiment, an alignment material is coated on a stamp substrate 200 to form an alignment material layer 202. Here, the stamp substrate 200 may be a flexible substrate considering a peeling process or the like. The alignment material may be formed by various methods such as spin-coating, roll coating, slit coating, And can be coated on the stamp substrate 200.

Although various materials can be used as the alignment material, it is preferable that a reactive mesogen (RM) having excellent effect is used. The reactive mesogens (RM) can be formed with sufficient thickness to account for the subsequent peeling process.

2 (B), the alignment layer 202 is irradiated with ultraviolet (UV) light to cure the alignment material layer 202. As a result, the alignment material layer 202 having the anisotropic property (Not shown). Hereinafter, the structure of FIG. 2 (B) will be referred to as an RM stamp.

According to one embodiment, the alignment method irradiates linearly polarized UV with an alignment material layer 202, which is used for directional photopolymerization of the monomers of reactive mesogens on the stamp substrate 200 Can be guaranteed.

Subsequently, the alignment method can transfer the RM stamp onto the cell structure for the LCD cell as shown in FIG. 2C. The cell structure may include a first substrate 110, an electrode (for example, ITO layer) 212, and an orientation layer, for example, a PI orientation layer 214, as a sequentially positioned target substrate. Specifically, the orientation material layer 202 of the RM stamp may be transferred after contacting the PI alignment film 214. [

The PI alignment film 214 may be formed on the first substrate 110 through various methods such as photo alignment, ion beam alignment, inorganic film oblique deposition, micro-rubbing, and self-adsorption alignment. For example, the PI alignment layer 214 may be spin-coated on the first substrate 110 on which the ITO layer 212 is formed, followed by soft baking and hard baking.

2 (D), the RM stamp can be peeled. As a result, a thin RM culture film 220 made of a reactive mesogen is formed on the PI alignment film 214 . That is, the orientation material layer 202 of the RM stamp can be separated into two layers 220 and 222. [ As a result, for example, a RM alignment film 220 having a thickness of 10 nm can be formed on the PI alignment film 214 for liquid crystal alignment and switching.

Finally, the structure having such an overall structure will be referred to as a lower LCD cell (display cell). The lower LCD cell may include a PI alignment layer 214 and a RM alignment layer 220. Here, the PI alignment film 214 has anisotropic properties due to the RM alignment film 220.

The RM alignment film 234 can be formed on the PI alignment film 232 on the second substrate 112 on which the ITO layer 230 is formed through the above stamp. That is, an upper LCD cell is formed.

2 (E), the lower LCD cell and the upper LCD cell are arranged, and as shown in FIG. 2 (F), the lower LCD cell and the upper LCD cell The liquid crystal layer 118 is formed.

In summary, in the alignment method of the present invention, a stamp having a reactive mesogen layer is produced, and the stamp is contacted with a target substrate (first substrate or second substrate) and then peeled, that is, the orientation material layer is transferred onto the PI alignment layer The RM alignment layer can be formed on the PI alignment layer. The process of forming the alignment film by using the stamp is simple. The LCD using the alignment method of the present invention has better liquid crystal alignment than the conventional LCD using the alignment method such as the rubbing method, and can have more excellent electro-optical (EO) characteristics.

In the above, PI or reactive mesogen may be used as the alignment film, but other orientation materials may be used. Further, although the LCD cell includes two alignment films, it is sufficient to include at least one alignment film.

Hereinafter, characteristics of the LCD according to the alignment film of the present invention will be described.

3 is a diagram showing a liquid crystal alignment state. Polarized optical microscopy (POM) was used to observe the alignment of the liquid crystals formed on the RM alignment layer.

As shown in FIG. 3A, a Schlieren texture was observed in liquid crystals randomly arranged on a pure PI alignment film without any surface treatment. On the other hand, a local alignment of the liquid crystals was induced on the RM alignment film transferred from the stamp cured by nonpolarized UV as shown in Figs. 3 (B) and 3 (C).

Thus, the present invention formed a RM layer on the stamp using linearly polarized UV to uniformly align the liquid crystals. As a result, a defect-free liquid crystal layer is formed as shown in (D) and (E) of Fig. 3, and liquid crystal molecules are arranged in a wide region. This arrangement may be necessary for various display applications.

On the other hand, the optical retardation of the target substrate was measured so as to track the liquid crystal alignment operation on the other PI alignment film and the RM alignment film as shown in FIG. 2 (F). The ability to align liquid crystal molecules depends on the anisotropic nature of the orientation films. Specifically, the optical delay measurement using the polarization analysis method of visible light can evaluate the anisotropy of the target substrate and determine the optimal conditions for producing the stamp.

No retardation was observed in the pure PI film, which means that the liquid crystals can not be arranged on the PI film without alignment treatment. On the other hand, the retardation increases as the reactive mesogen is printed on the optically isotropic PI film. The delay of the RM alignment film formed by transferring the layer of orientation material from the RM stamp on which the non-polarizing UV curing was performed slightly increased. However, this delay is not sufficient to realize the full array of liquid crystals.

Thus, the present invention utilizes a stamp made by linearly polarizing UV curing, resulting in improved delay and anisotropy of the RM alignment layer. This allows complete liquid crystal alignment.

4 is a diagram showing an XPS spectrum of an RM stamp. XPS analysis was used to confirm photopolymerization of RM monomers under polarized UV irradiation.

The XPS spectra of C 1s and O 1s of the RM stamp before and after UV irradiation are shown in FIGS. 4 (A) and 4 (C), respectively. The core-level XPS spectrum of C 1s is decomposed into three components as shown in Fig. 4 (A). The low binding energy component peak at 284.6 eV is attributed to the C-C bond and the peak at 286.2 eV is associated with the C-O bond. The other component peaks at 288.5 eV correspond to C = O bonds in RM monomers.

After polarized UV irradiation, the atomic percentage of the C-C single bond is significantly improved to about 20.6%, and the C-O single bond increases to about 8.7%. On the other hand, the C = O double bond decreases to 13.6%. This is because polarized UV irradiation destroys the C = O double bond to produce radicals that form a C-C single bond and a C-O single bond. This forms a linear cross-link between the reactive mesogens through photopolymerization.

Figure 4 (C) shows the XPS spectrum of O1s. The component peaks at 531.6 eV correspond to O = C double bonds and the component peaks at 533.0 eV due to O-C single bonds. After UV irradiation, the molecular concentrations of O = C and O-C are reduced to 54.0% and 27.0%, respectively, because weak O1s bonds are destroyed in photopolymerization of reactive mesogens. The LC core structure of the reactive mesogens can be maintained qualitatively in a homeotropic state due to linear polarized UV radiation.

Next, the XPS spectrum of the substrate on which the PI film was formed before and after the transfer of the orientation material layer (RM film) was confirmed. FIG. 4 (B) shows the change in the core-level XPS spectrum of the C 1s peak on the PI-coated substrate. The component peaks at 284.6 eV, 286.2 eV and 288.5 eV correspond to the degraded peaks of the RM stamp.

The atomic concentration of the C-C single bond increases to approximately 19.7%, and the C-O single bond increases significantly to approximately 25.8%. The C = O double bond atomic concentration also increases to 36.4%. Increased atomic concentrations of C-C bonds, C-O bonds and C = O bonds contribute to the transfer of the RM film to the PI membrane through contact with UV cured RM stamp. In addition, as shown in Fig. 4 (D), the atomic concentrations of O = C bonds and O-C bonds on the PI film increase to 20.9% and 34.2%, respectively, due to the transferred RM film.

Optical loss is an important factor when adding new films because new films can reduce the transparency of light when forming new films. Hereinafter, the light transmittance when using the PI alignment film formed by the conventional rubbing method and the RM alignment film / PI alignment film of the present invention will be compared.

5 is a view showing the light transmittance characteristic. For comparison of light transmittance characteristics, an ultraviolet-visible light spectrophotometer was used as shown in Fig. 5 (A).

The average light transmittance of the RM alignment film / PI alignment film and the rubbing type PI alignment film was 81.4% and 81.2%, respectively, which means that no light loss occurred even though the RM alignment film was formed on the PI alignment film. Since the thin RM alignment layer is not a topographical structure, the light loss in the interface between the alignment layers and the liquid crystal layer can be minimized.

The excellent EO characteristic including the reduced threshold value V _th and the fast response time can be realized in an LCD fabricated on the basis of a RM alignment film as shown in Fig. 5 (B). A rubbing type PI film and a nanopattern PI film using LIL were used for comparison.

The voltage-transmittance (VT) curves confirm that the liquid crystals can be switched off to on-off under an external voltage above a predetermined threshold (V _th ). The threshold for RM alignment at 10% transmittance is 8.4% lower than that of LCD with rubbed PI film and is 28.9% lower than the threshold of LCD including nanopatterned PI film using LIL.

The time-permeability graphs of the printed RM orientation film, the rubbing PI film and the nanopattern PI film are attributed to the rise and fall response times as shown in Fig. 5 (C). The VA-LCD using the RM alignment layer has the fastest response time of 26.5 ms (11.9 ms up and 14.6 ms down), and the VA-LCD using the rubbing type PI film has 36.1 ms (15.3 ms up and 20.8 ms down) And the response time of the VA-LCD using the nanopattern PI film is 27.5 ms (rising 10.2 ms and falling 17.3 ms), respectively.

The excellent EO characteristics of the LCD using the RM alignment layer can contribute to the defect-filling effect of the RM alignment layer on the PI alignment layer. The RM alignment layer can fill the microdefects on the PI alignment layer and can interfere with the molecular redirection and increase the molecular collisions of the liquid crystals at the interface between the liquid crystals and the alignment layers.

Image sticking is an important issue for developing high quality displays with long LCD lifetime. The image sticking may be characterized by the capacitance-voltage (C-V) hysteresis of the LCD cells. Time-dependent loss of trapped charges causes image sticking. Unlike the CV curves showing the characteristic hysteresis from the LCD cells using the conventional rubbing type PI film, the hysteresis-free CV curve for the LCD cell is acquired in the RM alignment film / PI alignment film as shown in (D) do. This indicates that the RM alignment film can cover the defects of the PI alignment film, trapping charges and increasing C-V hysteresis. Consequently, there is almost no charge present at the interface between the liquid crystals and the alignment layer in the LCD including the RM alignment layer / PI alignment layer.

6 is a diagram showing the temperature stability characteristic.

Referring to FIG. 6, the RM alignment layer filling the defects on the PI alignment layer improves the temperature stability of the conventional rubbing type LCD cell and the PI film based LCD cell. Increased thermal budget in advanced LCDs, such as microdisplay and high brightness displays, reduces the quality of organic materials and reduces the lifetime of the display. Therefore, alignment films having high thermal stability are required for display. LCDs including the RM alignment layer / PI alignment layer provide improved high-temperature operation due to improved thermal stability. This is caused by surface defect filling mentioned above. The LCD cell using the rubbing type PI film is stable up to 150 ° C but becomes unstable at 210 ° C and has a locally arranged state. On the other hand, the LCD cell including the RM alignment layer / PI alignment layer maintains stability up to 210 ° C.

It will be apparent to those skilled in the art that various modifications, additions and substitutions are possible, without departing from the spirit and scope of the invention as defined by the appended claims. Should be regarded as belonging to the following claims.

100: liquid crystal display panel 102: backlight unit
112, 114: substrate 114, 116: alignment film
118: liquid crystal layer 120, 122: polarizer

Claims (15)

Contacting a stamp comprising a layer of orientation material formed on the stamp substrate on a target substrate by irradiating the stamp substrate and the linear polarized ultraviolet radiation; And
And forming an alignment film on the target substrate by transferring a part of the alignment material layer to the target substrate through a method of peeling the stamp,
Wherein the orientation material layer of the stamp is separated into two layers at the time of filling and a portion of the orientation material layer of the stamp remains on the stamp. The method of claim 1, wherein the display cell is an LCD cell, the alignment material of the alignment material layer is a reactive mesogen, and the target substrate is an upper substrate or a lower substrate of an LCD. delete 2. The method of claim 1, wherein a polyimide (PI) alignment layer is formed on the target substrate, and a RM alignment layer formed by the transfer is formed on the PI alignment layer. 5. The method of claim 4, wherein the alignment material layer has anisotropic properties by irradiating ultraviolet light, and the PI alignment layer has anisotropic properties by the RM alignment layer. delete delete delete delete delete delete delete delete delete delete

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