Optical alignment photomask and design method thereof

Abstract

The invention belongs to the technical field of liquid crystal optical alignment, and discloses an optical alignment photomask and a design method thereof.The optical alignment photomask comprises a plurality of first areas and second areas which are adjacent and alternate, the first areas and the second areas take a plurality of parallel straight lines as adjacent boundary lines, and the incident planes and the emergent planes of the first areas and the second areas are the same and parallel to each other; each of the first region and the second region comprises a plurality of two-dimensional closely arranged unit structures, each unit structure comprises a cylindrical dielectric body arranged in the center and a metal body arranged on the outer side of the dielectric body, and the cross section of the metal body is square. By regulating and controlling the waveguide parameters of each unit structure, the emergent angles of ultraviolet light passing through the two areas can be symmetrical, so that the alignment of products can be realized only through one-time exposure, the alignment efficiency and the yield of the liquid crystal panel are greatly improved, and the liquid crystal panel is simple in structure and convenient to prepare.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid crystal optical alignment, and in particular to a photomask suitable for optical alignment and a design method thereof. Background Art

[0002] In the manufacturing process of liquid crystal panels, the alignment process has an important impact on the quality of the product. The alignment process is mainly divided into friction alignment and non-friction alignment. The friction alignment method can provide liquid crystal molecules with a strong alignment ability, but in the production process, the friction between the flannel and the substrate will generate static electricity and particle pollution, and static electricity and particles can often directly cause damage to liquid crystal components. Therefore, both academia and industry are studying non-friction alignment methods, which can not only avoid static electricity and particle pollution, but also make it easier to control liquid crystal molecules.

[0003] Among them, the most widely used non-friction alignment method is to irradiate the alignment agent with photosensitizer with linear polarized ultraviolet light, which is generally called ultraviolet light alignment method, or photo-alignment for short. Photo-alignment uses linear polarized ultraviolet light to irradiate the polymer alignment film with photosensitizer, so that the polymer has alignment ability. Its advantages are that it can avoid contamination of the glass substrate surface, can be used for small area alignment, can be used for pattern alignment through the mask, and can control the parameters of the liquid crystal unit, such as pre-tilt angle, surface orientation strength, etc., by using the angle of the incident light and the length of the irradiation time.

[0004] UV2A (Ultra Violet Vertical Alignment) technology is a VA (Vertical Alignment) panel technology that uses ultraviolet light (UV = UltraViolet) for liquid crystal alignment. Its name comes from the multiplication of ultraviolet light UV and the VA mode of the liquid crystal panel. After adopting UV2A technology, the aperture ratio, contrast and response speed can be improved, and the production process can be greatly reduced. In the alignment process, in order to achieve a wide-viewing angle display effect, polarized UV light is required to irradiate a single sub-pixel partition of the same substrate twice or more at a certain tilt angle (such as first unidirectional irradiation, then rotating the substrate 180°, and then unidirectional irradiation for the second time, and the two unidirectional irradiations are combined to form bidirectional irradiation) to form 4Domain, 8Domain and other alignment effects. At present, only half of the UV light plays a role in each exposure using a half-shielded mask, so the utilization rate of UV light is low, and multiple exposures also reduce production efficiency. Summary of the invention

[0005] In order to solve the technical problems of low production efficiency and ultraviolet light utilization rate of UV2A alignment technology in the prior art, the present invention proposes a photo-alignment mask and a design method thereof to improve the production efficiency of photo-alignment products.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a photo-alignment mask, comprising: a plurality of adjacent and alternating first areas and second areas, the first areas and the second areas are adjacently divided by a plurality of parallel and equidistant straight lines, the first areas and the second areas have the same incident surfaces and exit surfaces and are parallel to each other, the first areas and the second areas each include a plurality of two-dimensionally closely arranged unit structures, each unit structure includes a cylindrical dielectric body arranged in the center and a metal body arranged outside the dielectric body, and the cross section of the metal body is a square;

[0007] Along the straight line direction, the radius of the dielectric body of each unit structure in the first zone and the second zone changes; along the direction perpendicular to the straight line, the radius of the dielectric body of each unit structure in the first zone is the same, the radius of the dielectric body of each unit structure in the second zone is the same, and the radius of the dielectric body of each unit structure in the first zone is different from that in the second zone.

[0008] In the photo-alignment mask, along the straight line direction, the radius of the dielectric body of each unit structure in the first zone is periodic and changes monotonically within each period, and the radius of the dielectric body of each unit structure in the second zone is periodic and changes monotonically within each period, and the change trends of the first zone and the second zone are opposite.

[0009] The metal width between each adjacent unit structure is greater than the skin depth of the metal.

[0010] The parameters of each unit structure meet the following conditions:

[0011]

[0012] Wherein, (x, y) represents the position of a unit structure 6, a(x, y) represents the radius of the dielectric body 7 of the unit structure 6 at the position, h represents the thickness of the unit structure, β(a(x, y)) represents the lateral propagation constant of the unit structure 6 at the position, represents the initial phase of light, n represents an integer, x represents the horizontal axis displacement, θ in is the incident angle, θ out1 and θ out2 Denote the emission angles of the first and second zones, θ out1 = -θ out2 , λ represents the wavelength.

[0013] The relationship between the waveguide lateral propagation constant β and the radius a of the dielectric body is:

[0014]

[0015] J m (au) represents the m-th order Bessel function of the first kind, represents the first kind of Hankel function, J′ m (au) and represents the corresponding derivative, u represents the lateral propagation constant of the incident light in the dielectric part, and v represents the lateral propagation constant of the incident light in the metal part. The expression is:

[0016]

[0017] Among them, k d represents the wave vector of the incident light in the dielectric, k metal Represents the wave vector of incident light in the metal.

[0018] In addition, the present invention also provides a method for designing a photo-alignment mask, comprising the following steps:

[0019] Step 1: First, determine the angular frequency ω, wavelength λ, and incident angle θ of the incident light based on the parameters of the exposure equipment. in , according to the product to be aligned, determine the width pl of the first and second zones, and determine the emission angle θ out1 ,θ out2 , from which the phase change is calculated The distribution of

[0020] Step 2: Select the dielectric material and the metal material, and determine the relative dielectric constant ε of the two materials d , ε metal , according to the above parameters, the numerical relationship β(a) between the radius a of the cylinder and the lateral propagation constant β of the waveguide is calculated;

[0021] Step 3: According to Determine the side length d, thickness h of the metal body and the radius a of the dielectric body;

[0022] Step 4: Calculate or measure the conversion efficiency of the first zone and the second zone, and adjust the length l of the first zone and the second zone in combination with the incident light power distribution, so that the energy of the output light in each first zone and each second zone is the same.

[0023] The step 3 also includes the step of determining the number range of unit structures in each of the first area and the second area.

[0024] In step 3, there are:

[0025]

[0026] The relationship between the waveguide transverse propagation constant β and the radius a of the dielectric body (7) is:

[0027]

[0028] J m (au) represents the m-th order Bessel function of the first kind, represents the first kind of Hankel function, J′ m (au) and represents the corresponding derivative, u represents the lateral propagation constant of the incident light in the dielectric part, and v represents the lateral propagation constant of the incident light in the metal part. The expression is:

[0029]

[0030] Among them, k d represents the wave vector of the incident light in the dielectric, k metal Represents the wave vector of incident light in the metal.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The present invention proposes a light-alignment mask and a design method thereof. The mask is divided into multiple unit structures to form multiple adjacent alternating first zones and second zones by utilizing a metasurface phase control method. By optimizing the waveguide parameters of the first zones and the second zones, the emission angles of ultraviolet light after passing through the two zones can be made symmetrical. Therefore, the light-alignment mask of the present invention only requires one exposure to achieve alignment of the product, which greatly improves the alignment efficiency and yield rate of the liquid crystal panel. Moreover, the structure is simple and the preparation is convenient. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A schematic structural diagram of a photo-alignment mask provided in Embodiment 1 of the present invention;

[0034] Figure 2 It is a schematic diagram of the unit structure in the first area and the second area in the first embodiment of the present invention;

[0035] Figure 3 is a schematic diagram of a unit structure in Embodiment 1 of the present invention;

[0036] Figure 4 is a schematic diagram of light passing through a light alignment mask in the first embodiment of the present invention;

[0037] Figure 5 Schematic diagram of propagation in the mask cross section AA in the first embodiment of the present invention;

[0038] Figure 6 The radius a of the cylinder in the unit structure provided by the present invention is relationship;

[0039] In the figure, 1 is the first zone, 2 is the second zone, 3 is a straight line, 4 is an incident surface, 5 is an exit surface, 6 is a unit structure, 7 is a dielectric body, 8 is a metal body, and 9 is a transition zone. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0041] Embodiment 1

[0042] like Figures 1 to 3 As shown, the first embodiment of the present invention provides a light alignment mask, comprising: a plurality of adjacent and alternating first areas 1 and second areas 2, the first areas 1 and the second areas 2 are adjacently divided by a plurality of mutually parallel straight lines 3, the first areas 1 and the second areas 2 have incident surfaces 4 and exit surfaces 5 that are identical and mutually parallel, the first areas 1 and the second areas 2 each comprise a plurality of two-dimensionally closely arranged unit structures 6, each unit structure 6 comprises a cylindrical dielectric body 7 disposed at the center and a metal body 8 disposed outside the dielectric body, and the cross section of the metal body 8 is a square;

[0043] Specifically, Figure 2 As shown, in this embodiment, along the direction of the straight line 3, the radius of the dielectric body 7 in each unit structure 6 in the first zone 1 and the second zone 2 changes periodically; along the direction perpendicular to the straight line 3, the radius of the dielectric body 7 of each unit structure 6 in the first zone 1 is the same, the radius of the dielectric body 7 of each unit structure 6 in the second zone 2 is the same, and the radius of the dielectric body 7 of each unit structure 6 in the first zone 1 is different from that in the second zone 2.

[0044] Furthermore, in this embodiment, along the straight line 3, the radius of the dielectric body 7 of each unit structure 6 in the first zone 1 is periodic and changes monotonically within each period, and the radius of the dielectric body 7 of each unit structure 6 in the second zone 2 is periodic and changes monotonically within each period, and the change trends in the first zone and the second zone are opposite.

[0045] Specifically, in this embodiment, the metal width between adjacent unit structures 6 is greater than the skin depth of the metal.

[0046] Furthermore, in this embodiment, the parameters of each unit structure 6 satisfy the following conditions:

[0047]

[0048] Wherein, (x, y) represents the position of the unit structure 6, a(x, y) represents the radius of the dielectric body 7 of the unit structure 6 at the position, h represents the thickness of the unit structure, β(a(x, y)) represents the lateral propagation constant of the unit structure 6 at the position, represents the initial phase of the light, n represents an integer, x represents the horizontal displacement parallel to the straight line 3, θ in is the incident angle, θ out1 and θ out2 Denote the emission angles of the first and second zones, θ out1 = -θ out2 , λ represents the wavelength.

[0049] Furthermore, in this embodiment, the relationship between the waveguide lateral propagation constant β and the radius a of the dielectric body 7 is:

[0050]

[0051] Among them, J m (au) represents the m-th order Bessel function of the first kind, represents the first kind of Hankel function, J′ m (au) and represents the corresponding derivative, u represents the lateral propagation constant of the incident light in the dielectric part, and v represents the lateral propagation constant of the incident light in the metal part. The expression is:

[0052]

[0053] Among them, k d represents the wave vector of the incident light in the dielectric, k metal represents the wave vector of the incident light in the metal, and:

[0054]

[0055] Among them, ε d and ε metal They represent the dielectric constants of dielectrics and metals respectively, c represents the speed of light, and ω represents the angular frequency of the incident light.

[0056] Combine the following Figures 4 to 6 The alignment principle of the present invention is introduced.

[0057] The incident light is incident on the incident surface at point (x,y,0) parallel to the xz plane. The incident light angular frequency is ω, the wavelength is λ, and the angle between the incident light and the normal direction is θ in , the angle between the outgoing light passing through the first area Area1 and the normal is θ out1 , the angle between the outgoing light passing through the second area Area2 and the normal is θout2 = -θ out1 , the phase change between the incident light and the outgoing light The following relationship is satisfied:

[0058]

[0059] By adding different phases to light at different positions Light deflection can be achieved.

[0060] In this embodiment, the metasurface phase control method is used to divide the mask into multiple unit structures, and each unit structure will add different phases to the light according to its different parameters. In this embodiment, each unit structure is a cylinder embedded in a cuboid, the height of the cuboid is h, the length of the bottom side of the cuboid is d, the height of the central cylinder is h, the radius is a, the material of the cylinder is a dielectric, and the material of the remaining part of the cuboid is metal. Each unit structure can be regarded as a circular waveguide. The unit structure uses the surface plasma mode propagation constant β in the waveguide to change with the change of radius a. The unit structure can use this law to achieve phase changes of light in the range of 0 to 2π.

[0061] The distribution of the radius a of the dielectric body 7 on the mask satisfies Then we can get the above formula (1). According to formula (1) and θ out1 = -θ out2 The constraint relationship can determine the geometric parameters of the waveguide, that is, the unit structure 6. In addition, in this embodiment, the width of the metal between adjacent unit structures should be greater than the skin depth of the metal.

[0062] Embodiment 2

[0063] Embodiment 2 of the present invention provides a method for designing a photo-alignment mask according to embodiment 1, comprising the following steps:

[0064] Step 1: First, determine the angular frequency ω, wavelength λ, and incident angle θ of the incident light based on the parameters of the exposure equipment. in , according to the product to be aligned, determine the width pl of the first and second zones, and determine the emission angle θ out1 ,θ out2 , from which the phase change is calculated

[0065] Step 2: Select the material of the dielectric body 7 and the material of the metal body 8, and determine the relative dielectric constant ε of the two materials d , ε metal According to the above parameters, the numerical relationship β(a) between the radius a of the cylinder and the lateral propagation constant β of the waveguide is calculated, and the calculation formula is the above formula (2).

[0066] Step 3: Determine the side length d, thickness h of the metal body 8 and the radius a of the dielectric body 7.

[0067] Specifically, in step 3, various parameters are determined according to the following steps:

[0068]

[0069] Specifically, according to formula (7) and (8), the above formula (1) can be obtained, so the above parameters are determined according to formula (1).

[0070] The step 3 also includes the step of determining the number range of the unit structures in each of the first area 1 and the second area 2 .

[0071] Step 4: Calculate or measure the conversion efficiency of the first zone 1 and the second zone 2, adjust the length l of the first zone 1 and the second zone 2 according to the conversion efficiency, and combine the incident light power distribution to make the energy of the output light in each first zone 1 and each second zone 2 the same.

[0072] A transition method of this embodiment also includes a process of determining the transition zone and other positions. Generally speaking, UV2A technology is a multi-mask simultaneous exposure, and the connection position between the masks is regarded as a transition zone. The specific processing method is irrelevant to the present invention and is therefore not described.

[0073] After the design is completed, a metal film with a thickness of h is processed on the mask according to the determined parameters, the position of each unit structure is determined, and a cylindrical hole is processed in the center of each unit structure. Finally, the selected dielectric is filled in the cylindrical hole to form a cylindrical dielectric body, and the processing of the orientation mask is completed.

[0074] When the previous process is completed, the product only needs to be exposed once before the subsequent process of the product can be carried out.

[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A photo-alignment mask, characterized in that: include: A plurality of adjacent and alternating first areas (1) and second areas (2), wherein the first areas (1) and the second areas (2) are adjacently divided by a plurality of parallel and equidistant straight lines (3), the incident surfaces (4) and the exit surfaces (5) of the first areas (1) and the second areas (2) are identical and parallel to each other, and the first areas (1) and the second areas (2) each include a plurality of two-dimensionally closely arranged unit structures (6), each unit structure (6) includes a cylindrical dielectric body (7) arranged at the center and a metal body (8) arranged outside the dielectric body, and the cross section of the metal body (8) is a square; Along the straight line (3), the radius of the dielectric body (7) of each unit structure (6) in the first zone (1) and the second zone (2) varies; along the direction perpendicular to the straight line (3), the radius of the dielectric body (7) of each unit structure (6) in the first zone (1) is the same, the radius of the dielectric body (7) of each unit structure (6) in the second zone (2) is the same, and the radius of the dielectric body (7) of each unit structure (6) in the first zone (1) is different from that in the second zone (2).

2. The optical alignment mask according to claim 1, characterized in that: Along the straight line (3), the radius of the dielectric body (7) of each unit structure (6) in the first zone (1) is periodic and changes monotonically in each period, and the radius of the dielectric body (7) of each unit structure (6) in the second zone (2) is periodic and changes monotonically in each period, and the change trends of the first zone (1) and the second zone (2) are opposite.

3. The optical alignment mask according to claim 1, characterized in that: The metal width between each adjacent unit structure (6) is greater than the skin depth of the metal.

4. The optical alignment mask according to claim 1, characterized in that: The parameters of each unit structure (6) satisfy the following conditions: Wherein, (x, y) represents the position of the unit structure (6), a(x, y) represents the radius of the dielectric body (7) of the unit structure (6) at the position, h represents the thickness of the unit structure, β(a(x, y)) represents the lateral propagation constant of the unit structure (6) at the position, represents the initial phase of light, n represents an integer, x represents the horizontal axis displacement, θ in is the incident angle, θ out1 and θ out2 Denote the emission angles of the first and second zones, θ out1 = -θ out2 , λ represents the wavelength.

5. The optical alignment mask according to claim 4, characterized in that: The relationship between the waveguide transverse propagation constant β and the radius a of the dielectric body (7) is: J m (au) represents the m-th order Bessel function of the first kind, represents the first kind of Hankel function, J′ m (au) and represents the corresponding derivative, u represents the lateral propagation constant of the incident light in the dielectric part, and v represents the lateral propagation constant of the incident light in the metal part. The expression is: Among them, k d represents the wave vector of the incident light in the dielectric, k metal Represents the wave vector of incident light in the metal.

6. The method for designing a photo-alignment mask according to any one of claims 1 to 5, characterized in that: The following steps are involved: Step 1: First, determine the angular frequency ω, wavelength λ, and incident angle θ of the incident light based on the parameters of the exposure equipment. in , according to the product to be aligned, determine the width pl of the first and second zones, and determine the emission angle θ out1 ,θ out2 , from which the phase change is calculated The distribution of Step 2: Select the material of the dielectric body (7) and the material of the metal body (8), and determine the relative dielectric constant ε of the two materials d , ε metal , according to the above parameters, the numerical relationship β(a) between the radius a of the cylinder and the lateral propagation constant β of the waveguide is calculated; Step 3: According to Determine the side length d, thickness h of the metal body (8) and the radius a of the dielectric body (7); Represents the phase change between the incident light and the outgoing light; Step 4: Calculate or measure the conversion efficiency of the first zone (1) and the second zone (2), and adjust the length l of the first zone (1) and the second zone (2) in combination with the incident light power distribution, so that the energy of the output light in each first zone (1) and each second zone (2) is the same.

7. The method for designing a photo-alignment mask according to any one of claim 6, characterized in that: The step 3 also includes the step of determining the number range of the unit structures in each of the first area (1) and the second area (2).

8. The method for designing a photo-alignment mask according to any one of claim 6, characterized in that: In step 3, there are: The relationship between the waveguide transverse propagation constant β and the radius a of the dielectric body (7) is: J m (au) represents the m-th order Bessel function of the first kind, represents the first kind of Hankel function, J′ m (au) and represents the corresponding derivative, u represents the lateral propagation constant of the incident light in the dielectric part, and v represents the lateral propagation constant of the incident light in the metal part. The expression is: Among them, k d represents the wave vector of the incident light in the dielectric, k metal Represents the wave vector of incident light in the metal.

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